Since my last post a couple more things have happened that are pretty cool. Actually a lot of things happened, like becoming a photographer for the Stanford Daily, applying to join BASES (an entrepreneur group with a budget of half a million frickin’ dollars) and making arrangements to discuss my choice of major and undergraduate research opportunities with one of the 1996 Nobel laureates (!) but I don’t have the energy to write about it all… So I’ll do a brief keyboard mash about the SSCP.
The Stanford Solar Car Project (SSCP) is pretty much what it sounds like. It’s undergrads only (i.e. no professors involved) and we build a car that runs on solar power and race it across Australia at the World Solar Challenge. It’s one of the first things I got stuck into, and even before starting any real work on the project, I’ve learnt a huge amount, just by being in a proper workshop with tools and working with genuinely decent equipment (as one of my friends once put it, tools become beautiful once 4th formers [read: 13 year olds] aren’t allowed to use them). I’ve used a soldering iron that works using ‘pure physics’ (as Nathan put it) – it’s simply awesome: RF AC gets pumped through the iron and due to the skin effect, all the current flows through the tip, heating it up; I’ve learnt to solder surface mount ICs efficiently (it actually only takes a couple of minutes to do each one); I’ve used a battery welder in which the current is so high that it’s measured in kiloamps and the cables jump due to the massive B-fields when making the weld; and I’ve learnt to weld and use a mill.
Probably the most exciting thing is the amount of influence a mere freshman with little experience like me is allowed to exert. Before I proceed, I need to say a little about DC to put it all in perspective. DC is the head of the software team, and he is legendary. Apparently he did CS 140 and got a girlfriend in the same quarter. Descriptions of his physical feats reminded me of Alcibiades’ description of Socrates – he apparently did a 10 mile mountain hike in flip flops—one of which was broken—without complaining and managed to fall asleep on asphalt in the middle of the desert with people shouting and engines running all around. DC’s programming ability appears to be revered within the team … and that’s coming from people whose skill sets include welding their names in cursive handwriting on 1” iron bars and solder surface mount ICs on flying leads … without a breakout board … in 20 minutes. So when I suggested a method of wiring the solar panels and his response was along the lines of ‘we’ve never thought of that before, we might implement that’, and subsequently let it be my call how to implement an entire software project, I was … a tad surprised.
As a sidenote, I think the best quotation to date on the SSCP has to be ‘Everything seems to be working except the ON/OFF switch’ (!)
P.S. List of non-American expressions that I use
I’m compiling a directory of these; supposedly Americans don’t use the following vocabulary / idioms:
‘Take the piss out of’ ≈ ‘to make fun of’
‘Bollocks’ ≈ ‘oh crap’
‘Lie in’ [n.] = ‘sleep in’
‘Half eight’ := 08:30
‘Query’ [n.] ≈ ‘question’
‘To get done for doing something’ = ‘to get caught by the authorities for doing something’ ‘Shotgun’ (I extend its usage to just about anything; equivalent to claiming dibs on something)
‘Posh’ [adj.] ≈ ‘classy’ / ‘fashionable’
It’s through the use of some of these that I’ve managed to provoke several ‘oh you British people’ from my roommate…
P.P.S. How to like Stanford
This algorithm seems to work for me:
1. Find some random freshman
2. Talk to him/her
3. Be surprised
I could elaborate, but the fact is that Professor Harry Elam really wasn’t kidding when he declared at convocation that every single person is here for a reason; everyone I’ve met, without exception, is simply amazing.
Overwhelmed is an oft-used word, but for me, a British public school kid going to what I now believe to be the unequivocally the best university in the world for myself, it is an appropriate one.
Welcoming Latino students to campus
I flew from Heathrow in the economy section of the upper deck of a Virgin Atlantic Boeing 747 over South Greenland, Hudson Bay and the Rockies, and landed on Sept 2nd, well in advance of Int’l Student Orientation (ISO) on the 11th. Over the course of the week, in between setting up bank accounts, getting a phone contract and buying a camera (Canon Rebel XS + 18-200mm lens – blog post about it later!) I took the opportunity to explore the bay area. Golden Gate at night from the Marin Headlands is spectacular. The road on which Steve Jobs lives is beautiful. The wildlife on the Monterey coast is diverse and exciting. The weather is unbelievable. I visited Mills Hospital where I was born, and caught a glimpse of the house of my babyhood on Diaz Lane in Foster City; coming from drizzly, noisy, bustling London (which I of course still love), I am convinced that this part of California is the best place in the world to live.
And of course, I visited the campus on which I am to spend the next four years of my life, and it is best described as … indescribable – one really has to see it for oneself to understand truly what all the fuss is about. At every turn, from every angle, at any time, the sheer quality of the facilities and the opulence of the college blows me away. Just to illustrate with what I know of the sports facilities: the Arrillaga Sports Facility has a pristine fitness centre with modern equipment including some I’ve never seen before, a rock climbing wall with 6 routes set every week and an enormous basketball court. On the other side of the lawn, the Ford Recreation Centre has a gymnastics gym larger than my secondary school’s sports hall. Behind the tennis courts are four outdoor swimming pools and an American Football stadium. South of the main university is a Stanford-owned area of gently rolling hills larger than Richmond Park in London known as ‘The Dish’, named for the large satellite dish placed at its centre. West of that area is SLAC, the longest linear particle accelerator in the world, a luxurious golf course and a stables. Ridiculous is a word that springs immediately to mind. Ridiculous awesomeness. Plus campus has hummingbirds and a bamboo plantation.
On the 11th, ISO started. Apart from the cheesy, artificial and often cringeworthy icebreaker activities, the fire alarm that woke up the whole dorm at 3am, the most tuneless anthem I’ve ever heard (‘Hail Stanford Hail’) and the beach trip which was overcast and windy (ergo cold), I now genuinely believe that I couldn’t have ended up anywhere better. On the second night we had the opportunity to eat dinner with a faculty member. He teaches energy options, and in the ensuing discussion, I discovered that I am in the company of a class of, for lack of a better word, amazing people. The sheer knowledge, intelligence, passion and lust for knowledge infused with exceptional self-confidence (but not arrogance), communication skills and life experiences of some of the people I’ve met makes me feel like I’m in the company of an unequivocally brilliant set of people and that I’m going simply to love the next four years of my life. There were two debaters who took part in that discussion and both had a truly ridiculous amount of knowledge and breadth. They had exceptional understanding of the argument from political, social, economic and scientific perspectives, and the arguments and ideas they came up with and articulated eloquently were simultaneously inspiring and overwhelming. I subsequently met someone has very similar academic ambitions as I (physics with a CS twist) and is actually doing the same IHUM (Intro to Humanities) course as me, for the same reason (interest in philosophy). An appreciable proportion of the people I’ve met do programming to a level that exceeds casual interest (a fellow Brit did got through to the British Informatics Olympiad finals … and also does rock climbing). The people here are a hand-picked bunch of ludicrously well-rounded students, and it really makes a difference; I have yet to meet someone who falls into a stereotype – we have athletic, artistic and eloquent techies and logical, philosophical and scientific fuzzies. At first I had some deep academic concerns about choosing Stanford over Cambridge for precisely this reason – I believed that well-roundedness necessarily precludes expertise in any particular area. As it turns out, I was completely wrong, and the opposite is abundantly true. At the convocation speech, the following joke was made: “what do you call someone who only speaks one language? American”. But from what I can tell, a very large proportion of my peers are bilingual (at least). And speaking of people, Reed Jobs is in the same class as me (Stanford 2014) and I saw his dad, the CEO of Apple, at convocation. Just putting that out there…
Steve Jobs at Convocation
Then New Student Orientation (NSO) began. All over campus, the freshmen, a.k.a. ‘frosh’ (if you’re in the UK, read: ‘freshers’) started to arrive and the entire campus had a festive atmosphere. Each new arrival was personally raucously and vociferously greeted by a bunch of ecstatic Residential Assistants (RAs – sophomores and upperclassmen who have volunteered to help with freshmen dorms), and I finally met my roommate! Having gone to a day school and still used to the single-room paradigm at universities, I was slightly nervous about this but it seems Stanford really did their research and have come up with a good match – I think this arrangement will work out very well indeed.
Roble RAs welcoming incoming freshmen
I can’t talk about everything I like / am impressed with / have noticed. I haven’t even mentioned how beautiful the campus is, or how I have yet to see a raindrop. But here is a selection of stuff I happen to be able to remember off the top of my head.
Dorm Themes + cheers
Every dorm has a theme – mine (Otero) is ‘Moterotown’, a mutation of Motown; Robles has ‘Pirates of the CarRoblean’; Burbank’s theme is my personal favourite: ‘The Burbank Theory’, based on the famous TV comedy show ‘The Big Bang Theory’. They even have a poster pointing to a place on the couch saying ‘Sheldon’s seat’!
Further to this, there is a lot of class and dorm pride. Each dorm has several cheers, so at large events we can make our presence loudly felt (we also like shouting ‘FOURTEEEEEN!’ to demonstrate class pride), and after overcoming the initial self-consciousness it’s good fun and seems to contribute to a sense of family, spirit and bonding; I can’t think of a less clichéd / cheesy way of putting it but I’m absolutely genuine. According to the guy I bought my SLR from, his son went to Stanford and his freshman dorm was also Otero, and every year, for some reason or other, the people always bond really well and build longer lasting and deeper friendships with each other than at other dorms. I can see this being true of our dorm this year (our discussions are open and honest, and other people have commented on our spirit and energy when cheering) which leads me to suspect there’s some selection process going on, in which case I’m proud and delighted to have been chosen for Otero. Oh yeah – every dorm has a baby grand piano, a table tennis table and a flatscreen TV in its lounge.
There’s a football game tonight – Stanford v Wake Forest – at our stadium and since I’m irreversibly caught up in school pride, I will be attending and noisily supporting the two footballers who happen to be in my dorm (they’re *enormous*!). Relatedly, in events in which we’re going up against Cal-Berkeley, a popular cheer is ‘Beat Cal’.
Academics
Since classes haven’t actually started yet I can’t say much, but we did have a talk on an incredible CS project undertaken by Stanford students on AI. They developed a robot that could recognise images using what seemed to me as a particularly intelligent statistical approach to AI and image recognition and could (for example) walk to the office to get a stapler. There was also a demonstration of reinforcement machine learning in which a toy helocopter was doing ridiculous stunts all on its own. As it turns out, half the people involved in the entire project were undergrads. There are also incredible opportunities here. If all my near-future plans works out, I’ll be getting an inside-scoop tour of SLAC, meeting and possibly working with the quantum computing guys at IBM and meeting Prof. Leonard Susskind, a legendary string theorist. This is why I chose Stanford.
Speeches + discussions
These people really know how to do inspiring speeches. Dr Harry Elam is one of the strongest speakers I’ve ever heard, and at the end of every speech, regardless of the speaker (yeah there have been quite a few…), I’ve felt inspired and excited about being here. And I’m not normally impressed by this sort of thing.
There was also a ‘Faces of the Community’ event which consisted of some cultural dancing / music (e.g. Japanese drums, jazz dancing etc) but also talks from some really exceptional people (low-income, queer, ethnic minorities, disabled) talking about themselves. All their talks struck me as candid, honest, open, courageous – they must be truly great people to be able to accept their situation, and despite it make a real difference in their community, succeed and thrive in one of the world’s leading universities and above all stand up in front of 2000 strangers and open up. There was a subsequent discussion in the Otero lounge and many of my peers expressed similar sentiments to my own. Speaking of which, throughout NSO we’ve been having reasonably regular dorm discussions on multifarious topics, and again the openness and open-mindedness of our small community’s members is remarkable.
Unrelatedly, on another occasion there were some (pretty damn great) musicians in a band who had to do this cringeworthy music-camp style thing encouraging people to listen to each other. They got two volunteers to come up on stage and play the bass guitar, and they ended up giving away two guitars! I’m not sure what to make of that – it’s an incredible gesture, sponsored by some music company, and whether it reflects more the wealth of Stanford’s alumni or the university’s will to get people to try out new things is debatable. I’m not sure what point I’m trying to make (if at all), but something tells me that sort of thing wouldn’t have happened had I chosen Cambridge!
Geekiness
Despite what I said about well-roundedness, Stanford is undeniably geeky, but in a good way. I received an email whose first line read: “Dear awesome members of Group n, where 0<n<=24 && n∈N*". During our first dorm meeting, the Resident Fellow set out the dorm rules, beginning with 'Don't be stupid'. He continued to define stupidity as 'an act that significantly increases the probability of physical, psychological or financial harm occurring to you or someone else' (I personally think it should be 'an act that significantly increases the expectation of the sum of physical, psychological and financial harm occurring to you or someone else' but hey), and gave a load of examples of stupidity. Abstracting everyday concepts and working with them for sake of argument (and/or comedy) is the sort of thing I do on a regular basis; I think I'll fit in just great!
Health
I’ve managed to go on a jog every morning so far, including one 60-minute run which was a result of my getting lost… Californians are normally pretty health conscious but I am determined never to develop a shape whose parameters can be summarised by a radius (i.e. any sort of spheroid). Let’s see how long this is going to last… There was also a swing dancing class as part of NSO which was very reminiscent of Ceroc which I used to do (a bit) in London. It’s actually offered as a 1-unit class and therefore contributes towards a degree. It was also good exercise.
Miscellaneous
There’s a free bus service (‘the Marguerite’) around campus and nearby bits of Palo Alto, which apparently used to be horse-drawn (it’s now powered by hybrids, or something green like that). Stanford is also the most bike-friendly place I’ve ever been – I’ve seen more bike parks around campus than I have in the whole of London, and buses (including the Marguerite) have bike racks on the front.
The food is also pretty good. It’s not quite as luxurious as the specially-arranged food I got whenever I was at Cambridge for events (this includes Trinity, Corpus and St Cats) but it’s very decent, and much better than what I’ve been eating at school for the last ten years.
One thing I’ve noticed is most stuff in America is cheesier than most Brits would expect. The Kennedy Space Centre had some of the cheesiest exhibits I’ve ever seen, and even here the icebreakers and cheering etc. just make me feel self-conscious and uneasy and serious points made in these situations just make me want to laugh!
So yeah. Beat Cal!
I apologise if this post is probably not massively helpful to anyone thinking of applying: it’s most certainly biased, contains only one point of view and it’s written by someone who’s only been here a week. It’s more of a stream of consciousness affair – a disorganised and ineloquent splashing of ideas onto a page, and I haven’t said everything I want to (if I had, I’d've written an extremely fat book). I just wanted to say I’m happy, and am sure I made the right decision after agonising for literally months over my choice of Stanford, Harvard and Cambridge. In almost every comparison I’ve subconsciously made of myself with my year group at Stanford, I’ve felt inadequate and overwhelmed. I used to think I was pretty clever, but I now know that’s really not the case. For the first time in my life I’m acutely aware that I’m in the company of people who will shape the future and create the world of tomorrow – I’ve finally found a group for which I believe it. I feel that this is where I belong but simultaneously massively outclassed in every aspect. It’s bizarre, and wonderful.
Over the years I’ve taken part in two school-related trips that I will remember for the rest of my days. The first is my first walking trip to Snowdonia in 2005 at the end of my first year at St Paul’s. The second is this one. Both were characterised by breathtakingly beautiful scenery, exciting activities, and an incredible group of likeminded, diverse and amazing people (both were also organised by physicists…) Ours is also a bit of an underdog story, riddled with adventures, stress, disasters and rollercoaster ups and downs but mitigated by dedication, resourcefulness and the best team I have ever worked with. It’s a good story; I hope you enjoy it.
(Also, please check out my pics. “Click to embiggen” applies to all the illustrations in this post.)
The CanSat Competition
Our CanSat
By means of introduction, we were taking part in the first ESA European CanSat competition – a competition to build coke can sized ‘satellites’ that are to be dropped from 1km up (fired up there by a rocket) and drift down to earth using a parachute, taking data as they descend. The thing was organised by ESA, took place at the Andøya Rocket Range (ARR) and was overseen by NAROM (National Centre of Space-Related Education, translated into Norwegian to make the acronym).
The primary mission was to take temperature and pressure data, and teams were required to come up with and effect a secondary mission. Ours (Team Eclipse) could be classified as ‘advanced telemetry’; we were to take measurements of GPS position, speed and course, and acceleration and heading data, to create a wind profile of the various wind layers encountered during the descent. This could be used for the deployment of a hypothetical second payload – to allow the crew to drop the package at exactly the right location for it to fall to an exact position on the ground. Such devices actually already exist and are known as dropsondes and are used by the RAF for similar purposes. We were sponsored by Mattherhorn Investment.
Here’s a quick overview:
Pressure sensor
Used the one that came with the Pratt Hobbies CanSat kit
Calibrated it using bell jar and Pasco altitude datalogging meter
Confirmed at RAL [we did some testing at the Rutherford Appleton Laboratory] to within experimental error
Temperature sensor
Tested at RAL until batteries conked out.
HMC temp sensor seems not to work, but resists calibration owing to wide scatter
Instead derived function using thermistor’s datasheet. Inferred temp as a function of thermistor resistance using Eureqa, CanSat transmits raw voltage, crunch numbers at ground.
Battery
Conked out at low temp (-15°C). Trying to insulate it. Fulfils 3 hr lifetime requirement at room temp.
GPS chip
Needed to import a few libraries
Needed a voltage regulator to get PCB’d
Needed an antenna + connector pins to be bought
Takes time (anything from 45 seconds to 10 minutes) to boot up + acquire satellites
Very temperamental, often just doesn’t work
Antenna was loose, had to secure using araldite
Accelerometer
At first thought there weren’t enough ADCs on the microcontroller, invented logic / switching circuit; but found more ADCs on board
Needed calibration
Used as redundancy for HMC
A short killed it. Needed to buy a new one two days before flight
HMC
I2C Protocol, took forever (research) to get it to work
In meantime, Plan B: get magnitude of accel using analogue accelerometer and use GPS data points (D speed / Dt) to work out accel bearing (this plan was ultimately abandoned when we worked out how to use I2C)
Poor documentation, took 2 days (12 man hours) to work out interpretation of tilt/roll/bearing, and finally worked it out
Discovered tilt/roll are calculated from accel data on chip to get ‘down’ vector, and are redundant data, so factoring them in resulted in apparent constant direction of accel downwards with varying magnitude (!) Chose to assume tilt/roll = 0 for entire flight, just use heading data. Interpretation we took so long to work out was barely used!
Tested using home-made centrifuge
Centrifuge used for testing accelerometer in HMC - consists of Pasco runway on top of turntable, CanSat sitting in bucket
EEPROMs
Nearly didn’t fit, constructed I2C stack to house it all, caused short due to space shortages
Voltage regulator
Adding EEPROMs in late with extreme limitations of space, +Vcc contact pushed through insulation + touched earthed CanSat body, caused short, fried V regulator
Had to buy Zener diode minutes before shops closed (no stock of 3.3V 3-pin regulators)
The two fried components we threw out at the ARR
Printfloat
The NAROM guys accidentally gave all the teams a buggy and redundant function to print floating point numbers so we spent some time debugging this
Data Flow Diagram of our system
Harvester
Adapted by me from a Visual Basic example program
Dumps raw data to file
HAL
Written entirely by myself in C#
Scrapes + treats data from raw file
Outputs treated data to csv
Outputs GPS trace
Calculates + outputs wind profile
Visualiser
Written entirely by myself in C#
Uses DirectX to display a 3D visualisation of the wind profile
Day 0 (Sat 14th Aug) – Preparations
We had a pressure sensor and thermistor-potential-divider temperature sensor. There was a voltage regulator (3.3V) which powered the entirety of the secondary mission: an analogue accelerometer, a digital compass with a built-in accelerometer (the HMC), four EEPROMs which we had added at the last minute, and a GPS chip.
We hadn’t actually done much proper work on the CanSat until a couple of weeks before going to Norway, though we had done a balloon test. We needed to get the go-ahead from the Civil Aviation Authority to fly weather balloons to 100m altitude from our school playing fields but one balloon managed to get loose and flew upwards out of sight, resulting in several awkward phone calls to the authorities and the end of our balloon test! Due to lack of planning and an abundance of problems (including shorts, loose connections and general unticked to-do list items), we ended up doing our actual balloon test on the last day (a Saturday), the day before we left for Norway with a dummy CanSat using video cameras to judge position and speed etc. The reason for our lack of operational CanSat was a short which fried our voltage regulator and analogue accelerometer, though at the time we only knew the regulator had fried and were assuming the worst for all the 3.3V components. I had to rush to Maplin on bike in the rain and arrived exactly at their closing time, at which point I burst in, dripping and dishevelled, and announced to a group of bewildered Maplin employees ‘I need a 3.3V voltage regulator. It might seem funny, but this is a bit of an emergency!’
I ended up buying a Zener diode, as they had no 3-pin regulators in stock.
Day 1 – Journey Up
I discovered non-vicariously that traffic conditions between Barnes and Heathrow are amazing if you wake up at 4:30 am. The Team Eclipse representatives (Matthew Willetts, Tim Palmer, Jacob Ader, Dr Stephen Patterson and myself) convened at 5:30 at Heathrow Terminal 3 with a broken CanSat and a load of equipment (breadboard, croc clips, multimeter, araldite, superglue etc.) – as Tim pointed out, it was clear from what we packed that we hadn’t a clue what was wrong with the damn thing… We were joking at this point about the probability of getting everything working. We figured it was about 1/256 – 50/50 for each of 8 components.
An interesting feature I noticed about Norway’s airports is the fingerprint-based security (apparently phased in about 4 years ago) which replaces the need for a boarding pass and passport after initial check-in. It was incredibly (surprisingly) efficient, secure and functional, and I personally think the UK is sorely in need of such a system.
Our travel itinerary was slightly ludicrous and to get from London to the Andøya Rocket Range where we would be staying we needed to make three flights: London-Oslo, Oslo-Tromsø, Tromsø-Andenes (and of course a taxi journey from Andenes [Apparently the airport in Norway with the second longest runway] to the ARR). We met the Czech team on Oslo before our second flight and flew with them to Tromsø, and we shared our Tromsø-Andenes leg of the journey with the Belgians and the Norwegians.
We did manage to take a peek around Tromsø during our stop. There are two cathedrals, both of which we managed to visit (though only from the outside) and a long bridge from one side of the river / bay to the other. We also discovered at this point that the GBP is ridiculously weak against the NOK – just about everything at Tromsø cost about 1.5 to 2 times more than it would in London… We did find these things called ‘boller’ which were hot cross bun-sized sweet bread rolls which were going for 3 for 20K (approx. £2).
Tromsø's main street
Tromsø's main square
A view of one of the cathedrals from Tromsø's large bridge
The prop plane that took us on the last leg of our journey - from Tromsø to Andenes
On arriving at the ARR we had dinner2 (the Norwegians have two dinners; the first a heavy one, the second more of a supper snack type thing) when I first tasted Brunost, a type of brown cheese Norway is famous for. As someone put it, you either love it or hate it; I guess I fall into the first category. We were told that there was to be no alcohol at the ARR (to much groaning) and then worked on the CanSat until past midnight. We also quickly botched our presentation together (it appeared that we were the only team that didn’t know we needed to do a presentation the next day), confirmed our primary mission components and HMC were working, and discovered the second analogue accelerometer had fried.
The Andøya Rocket Range Hotel
Day 2 – Presentations and work
There was an opening ceremony in the morning
Opening the competition
Our presentation was extremely rushed as we had attempted to fit 6 months of work into a 10-minute presentation. Luckily the entire competition was in English, so we could talk very quickly and wing it a little. We even managed to throw in some Boris Johnson humour and unpreparedness…
We were then given a talk on the Norway Space Centre, whence these (rushed and probably mostly factually incorrect) notes come:
1st rocket launched was 60 years ago, named after Ferdinand the Bull, to investigate noctilucent clouds which are ~ 82 km up, ~ -130°C, humidity ~ 10-6 sea level humidity; wanted to investigate meteoric clouds as a cause.
Svalbard has 24 hr darkness in the winter, good for Aurora Borealis
Norway owns plenty of ocean; if ocean area were taken into account, Norway would be the second largest country in the world (to Russia)
NSC launched its first satellite recently (July 2010) – a side 20 cm cube satellite weighing 6 kg; geostationary; manage ships in ocean.
Microgravity ecology on ISS. Had to build 50-60 M EUR flowerpot!
Svalbard is the best representation of a Martian landscape on Earth – found chemicals there unique to Mars (!)
There are no Norwegian astronauts as the NSC concentrates more on building stuff
Every year ESA do a space camp thing in Norway – the students build an actual rocket, put instruments inside and launch it.
Torstein Wang from NAROM (Torstein literally means ‘Thor’s Hammer’. How awesome is that?) then gave us a talk on the intruder rocket which was to fire our CanSats into the cloud layer to be deployed. Here are some more notes:
Modified Intruder rocket (great name), but lengthened
0-1.9 s after lift off – fuel burn, rocket gets to max speed
Delayed charge set, rocket goes at constant speed to 1 km altitude
Explosive charge ejects nose cone + CanSats
Using Yagi antennas
We were then given the evening to work on our CanSats. We managed to get the voltage regulator, EEPROMs and GPS chips working, much to our relief. Stephen (the school physics technician who was overseeing our project) explained about the De Broglie-Bohm interpretation of QM during a spare moment, then everyone except myself went to bed – I (along with the Spanish team as it transpired the following morning) pulled an all-nighter to get an EEPROM program working. At about 4am I got bored and climbed a very steep mountain next to the ARR and was rewarded with a truly spectacular view of a sunrise over distant mountains.
I took the Union Jack to the top of the world at 4am
Sunrise over Andoy - staggeringly beautiful
Microwave antenna at the ARR
Day 3 – the launch
I awoke when Stephen opened the door of the electronics workshop to find me sprawled across three office chairs with an enormous platter of crisps on the table – I think I might have dozed off for half an hour or so. The rest of the team entered soon after with my breakfast and we discovered a fault in the radio transmission board. Panicking, we grabbed spare boards from another team and NAROM, and Tim set about debugging a piece of electronics already scarred from months of resoldering. As it turned out, it was just a loose connection to the antenna.
The launch was at Skarsteinsdalen and on the bus ride there I had to do some emergency reprogramming to fix a small problem related to the EEPROMs. Being Paulines we forgot to bring the audio cable to connect the radio receiver to the laptops so ended up having to borrow one. We also discovered at this stage that our alkaline batteries would not survive 30 minutes of flight due to voltage drop (the Zener diode was also a less efficient regulator than the 3-pin one and wasted more power) so ended up having to borrow a lithium one (which retains the same voltage over its lifetime) from the Belgians. We tried to insulate the battery and warm it up to prolong its lifetime by first putting it under Jacob’s armpit then putting it in a bag and dipping it in hot Earl Grey tea!
Our launch!
The Intruder Rocket
During the actual launch the GPS chip, the most important one to our secondary mission, failed and we collected no GPS data. Our (in hindsight way too large) parachute, however, deployed beautifully (we had only worked out how to fold it the previous night and had never tested to check it would open) and thanks to the lack of wind, the thing landed 700 metres away, within the 800m competition limit. We ended up using nothing but accelerometer data to do some Euler’s Method enormously fudged ‘integration’ to get what looked like a decent wind profile and GPS trace. We even ended up having to solve a horrific second order non-linear differential equation to get wind speed as a function of acceleration and the CanSat’s ground speed using Wolfram Alpha (and linear programming to get the constants). We also created the second presentation to present our results.
Beautifully deployed parachute. Photo by Matthew Willetts
One other dramatic moment was when the rocket containing both the Spanish and Czech teams’ CanSats misfired – the first part of the fuel burnt, but owing to (presumably) some sort of blockage the fuel stopped burning for one or two seconds and by the time the CanSats were ejected the rocket had almost hit a mountain, and both teams got mere seconds of data. The Belgian team also blamed us (in jest) for their own lack of GPS data – their GPS stream stopped at the same time as when their accelerometer registered a spike, which corresponded with when our CanSat was dropped into the rocket on top of the Belgian one. We both eventually decided to (still in jest) blame ESA for not planning the thing properly and putting two GPS-enabled CanSats in the same rocket! Though we did feel a bit guilty afterwards.
By the end of the evening I had slept for 10 hours in the previous 72 and quite rapidly conked out.
Day 4 – presentations and result
Most people in the room seemed pretty impressed with our Google Earth and Visualiser visualisations and we managed to time it just right. We got a tour of the ARR and received a talk on NAROM:
All profit goes to organic growth
They have a student rocket programme in which the students take part in the entire operation of building a rocket, launching it to 9 km and analysing data.
They have cool projects like ANSAT and CubeSat
We were then sat back in the main conference room for the results. We were massively sleep-deprived and our best attempt at a joke was ‘the Irish are going to shame us’ which looked pretty likely when they announced the third and second places (the Belgians and the Irish respectively). And finally, first place: ‘we selected this team because they were well-organised and always calm’. It wasn’t us. ‘We have decided that the British team, Team Eclipse, have won the first ESA CanSats in Europe competition!‘ I was apparently too stunned to stand up for a couple of seconds… In the end every team won a well-deserved special award, including the tightest budget and the best outreach.
Wind profile visualisation
In the aftermath, for the first time everyone was free and available to socialise. We played a couple of games of Mafia, took photos and had a BBQ. The Spanish seemed to find my attempts at Spanish inexplicably amusing and I discovered that a member of the Spanish team had worked on a similar electronics problem that I had previously and talked with him for a while on that (in English) – apparently many of the other teams had been forced to take special English lessons for this competition. I found myself in the midst of the friendliest likeminded group of people I had ever met, and really started to enjoy myself.
We also took part in a local tradition of swimming in the Arctic sea – the cold shock made me feel numb and warm stepping out of the sea into the wind which was slightly concerning. The full routine was swim-sauna-cold shower-sauna-jog, and by the end of the evening I had had 16 hours of sleep in the previous 96, but was still feeling physically amazing and revived.
Swimming in the Arctic Ocean
Day 5 – whale safari
We started the morning by talking to a Norwegian reporter who described London as ‘too warm’ and to whom we said we would celebrate by ‘sleeping … a lot’. We (the UK and Belgian teams) went mountain climbing with the help of a map of a good route that I had drawn after my previous ascent. We even found a guest book near the top which we all proudly signed. We lunched rapidly and moved to some really quaint cabins (which reminded Matthew of Cape Cod) in Andenes where we were to spend the night. We bought plenty of spirits and beer (Norwegian Dahls beer is better than Budweiser in my opinion) and I grabbed myself a kilo of Brunost… The Norwegians told us that if you kill a crow, cut off its legs and hand it into the police, you’re entitled to 50 Kroner. When we asked them the reason for this strange law, they responded nonchalantly, ‘they steal our strawberries’.
Signing the mountain guest book
View of Andenes from the top of the mountain
The whale safari which we had signed up for followed. The journey out was probably the roughest journey I had ever had (with the exception of a couple of sailing outings I had previously done) and we sighted two sperm whales. We dined at Andenes’ former jail which had been turned into a restaurant, and ethical issues aside, medium rare whale meat is delicious. What followed was an evening of drink…
A sperm whale!
We found a flagpole. We had a flag...
My photography 'skills' really don't do the sunset justice
A precedent for what happened later...
Day 6 – journey back
We found our CanSat story in two local papers, though one of the published pictures featured us kneeling next to an upside-down union jack. Though considering the photo had been taken just after our launch and we had just discovered we had no GPS data, we were effectively in distress and the orientation was justified. On the way back, for the first time we were questioned about the CanSat at airport security (an aluminium cylinder with wires sticking out) which we explained by showing them the newspaper article! At an idle moment the Norwegians, whose travel itinerary followed us to Oslo, explained a little about their coinage – the 20K piece has the Norwegian king on it (Norway being one of very few countries in which the monarch has any real power), and the 200K note has a picture of the guy who discovered the science behind Aurora Borealis. We said our final goodbyes and took off for Heathrow Terminal 3.
Distressed Union Jack
On the way back the rayleigh scattering from the setting sun lit the clouds beautifully from above.
Concluding thoughts
We’d started off intending to win. Over the course of half a year, as we encountered setback after setback, made agonisingly slow and sometimes negative progress, and lost active team members, we discovered this project was a damn sight more difficult than we had originally anticipated, and morale fell to dangerous levels. We came to Norway with a tin can filled with smoking components and frayed multicore cables, hoping not to win but just to get some data of any sort. Cortisol levels reached personal lifetime highs for every one of our team members at the ARR, and sleep dep began to drive us literally and quite disturbingly delirious. Despite this, we won a European competition, made some amazing friends, took some great photos of the staggeringly beautiful scenery and learnt some lasting lessons. It’s been an amazing experience, and I owe the guys at the ARR, NAROM and ESA, as well as my teammates and everyone else who took part, my sincere gratitude.
The Team Eclipse Norway representatives. Top row: Jacob Ader, Matthew Willetts, Dr Stephen Patterson. Bottom row: Bryant Tan (myself), Tim Palmer. Photo by Dag Martin Nilsen from NAROM.
I’m back from an exhausting, exhilarating and grossly exercise-deficient 9-day trip to Florida. This was originally meant as a school physics trip (much like the ‘physics trip’ to Thorpe Park…) to see the penultimate shuttle launch. Sadly the launch was delayed to November, and the rocket launch that was supposed to have replaced the shuttle launch also didn’t happen in the end. Fortunately, it is very difficult to go to FL and get bored, so we had a pretty packed schedule. For me it was one heck of a trip for several reasons, but mainly because there were about 100 other like-minded secondary school students on the trip, and also because it was the first time I’ve been to the US since I was born (I left CA, where I was born, when I was a toddler so everything was new to me) In brief, and in pictures (click any pic to embiggen, or click here to see them all):
Scary
Day 0 – Flight in
We had dinner at Ponderosa, a buffet where, as Matthew put it, we ate so much that we became sad afterwards. Presumably a combination of feeling ill and sleepy, or some sort of shock from having eaten so much oil.
Sunset combined with the East Coast clouds is beautiful. The photo, taken through a double-glazed window, really doesn't do it justice at all.
Day 1 – Baseball, Beach
We were taken to watch a baseball match in the morning. It was something like the national U16′s baseball final, and I didn’t find it hugely entertaining; compared to cricket, the batsman seems to miss most of the time and I seem to remember points (runs?) were scored extremely infrequently.
This is a freakily timed shot - I think the ball itself appears between the legs of the fielder (!)
We spent the afternoon at Cocoa Beach. There wasn’t a trace of any oil, presumably because some poor team of people is paid to somehow keep it at bay by trawling, scraping or shovelling the black mess someplace else, so we got the famous golden sand + glistening ocean experience. Which was pretty cool :)
Pelicans sometimes dive-bomb the water to get fish. They're awesome that way.
Day 2 – Universal Studios
Florida’s famous for its theme parks, so we spent the day at Universal Studios. I was surprised by the amount of care, effort and cash pumped into the actual theming of the rides. I found the Simpsons ride unreasonably effective; it was effectively a glorified ’4D’ (I hate that name…) experience, but by adjusting the tilt and roll of the entire platform to provide a ‘g-force’ direction and having screen practically surrounding the riders (I’d say at least 2 pi steradians), some really incredible effects were achieved.
I can't remember this beast's name. But it was extremely fun, even though there were no inversions.
The universe revolves around me...
We dined at Hard Rock Cafe which was apparently really good, but some of us, me included, were still full at the time (burgers for lunch etc.) that we didn’t eat anything (dinner was ridiculously early; at 4:30)…
Day 3 – Kennedy Space Centre; Lunch with an Astronaut
We explored the KSC Visitor Centre in the morning and did the shuttle launch experience, which I thought was an impressively well-designed piece of kit; they even used the lumbar to give the impression of forward acceleration (relative to the rider’s frame of reference). We then had ‘lunch with an astronaut’ which actually just meant a really tasty lunch during which an astronaut appeared, gave a talk, took some questions and offered photo ops. I had the distinct impression he had been asked to dumb down his talk as much as possible – he answered almost all the questions as if reading from a simple.wikipedia.org page printed in Comic Sans. He did quote an equation which he claimed was related to Kepler but which we had never heard of before, and when we asked him about it he implied Kepler had derived it using linear regression on Tycho Brahe’s data, which could have described any of Kepler’s laws. I suspect it was derived from his laws and energy considerations but seeing as nobody could remember the equation afterwards I decided to drop the matter.
The VAB: the world's second largest building by volume, and it has its own weather...
Day 4 – KSC; Astronaut Training
I wasn’t really sure what to expect from this day but I was actually pretty pleased with how it all panned out. There were some great displays and tours including old space equipment with accompanying stories (corned beef springs to mind), there were live demonstrations of the heat-proofing tiling material used on the orbiter and the hygroscopic powder used in the space toilets (sodium polyacrylate). We did a role-playing exercise of operating the shuttle on a mission, and of course we each had goes in the astronaut gyro things. The organisers were friendly and I thought it was a thoroughly worthwhile day.
Day 5 – Free day at KSC
The centre is actually really massive, including up-close coach tours to the launch sites and the legendary VAB (the Vehicle Assembly Building, which is allegedly so big that rainclouds form inside it). We were told about the ‘twang’ (the brief tipping forward of the entire shuttle before takeoff when the main engines are turned on), the difference between the orbiter (the plane-like thing) and the shuttle (the entire orbiter + external tank + boosters system), and the stages of shuttle launch (which I honestly can’t remember. SRBSep [Solid Rocket Booster Separation] and ETSep [External Tank Separation] happen in that order, I think…), and even had wildlife pointed out to us (including a truly enormous bald eagle nest that’s been around for almost 50 years). Apparently there are something like 320 species of bird on the complex.
Full-scale model of the Saturn V rocket. It's MASSIVE!
Day 6 – Island Adventure Theme Park
More theme parks! All I’ll say is that Harry Potter Land was unbelievably crowded (45 mins queue to get into a shop), butterbeer tastes like Dr Pepper with a 0.5cm thick layer of vanilla cream on top, and Duelling Dragons is probably the most impressively designed ride I’ve ever been on – the timing and closeness of the near-collisions are truly incredible, and the density of twists and turns made me lose track of the true direction of ‘up’, which has never happened to me on any other ride (and I’ve been on quite a few).
The Hulk. Great ride, pulled some pretty big gs
Harry Potter Land - beautifully themed.
Day 7 – Airboating
Airboats are simply awesome vehicles. They are capable of going into (basically) a drift at top speed without the least bit of instability, and you stop by turning them 180° and turning up the fans while going backwards. We managed to snap a load of wildlife with some helpful pointers from the driver.
These go incredibly quickly and have scarily good stability. They're like hovercrafts, but *much* better.
You can just about see a bald eagle near the top right of the tree
I have no idea why this didn't blur or be focussed on the wrong thing (like my camera usually does)
We also visited the mall, which was almost entirely clothes, shoes, jewelry and food, as expected…
Miscellaneous Observations
Lots of the stuff I was told about the US and/or Florida actually turned out to be spectacularly true. The cars are, almost without exception, enormous. Most parking lots are easily 0.5m wider than in the UK. People are generally friendly, happy and Anglophilic (it was also the first time I’d come across a customs person who smiled at me). The food portions are ludicrous, leading to the unmitigated and undeniable crassulence of an alarming proportion of the people. And the skies are just beautiful.
A beautiful and bizarrely radiating-patterned sunset
For some reason there's something beautiful about the skies in Florida. Most of the time, every type of cloud, from cumulostratus to cumulonimbus to cirrus is represented.
P.S. Interestingly, I actually managed to lose 1 lb. Go figure.
I’m back from my last ever school walking trip, a week of hill walking, this year on Skye, which is supposed to be one of the best places for hiking in the UK. Despite being an island just off the west coast of Scotland, its highest peak (Sgurr Alasdair) is taller than the tallest mountain in England! Needless to say, I’ve snapped plenty of photos.
In brief: it was mostly rainy except for the last day, on which we climbed Sgurr nan Gillean which was the most prominent peak viewable from Sligachan Lodge (where we were staying), though it was only actually visible on the last two days of our stay owing to mist and rain! On all the other days we did shorter walks, persevering despite the showers and wind.
Sgurr nan Gillean (left), Am Basteir and Bruach na Frithe (right), seen from Sligachan Lodge
Wildlife
Surprisingly enough, despite being sparsely forested owing to the weather, Skye has a cornucopia of wildlife, including a couple of golden eagles which we spotted soaring hundreds of metres above our heads. Bird photography is incredibly difficult and I resorted to looking through my DSLR’s EVF with one eye and following the bird with the other, making tracking flying objects possible. We also spotted a few seals and even a whale at one point! Sadly I was unable to get a shot of the whale, as it was too far away and even with 10x optical zoom my photo may as well have been of a wave. Probably the best wildlife we saw was on the way back from Skye when we stopped near Loch Lomond for leg stretching and saw a bird’s nest in the roof of a building, at arm’s reach!
A golden eagle soaring above us. My camera's collecting lens is too small to give a clear shot of fast-moving objects at such zoom
I was really lucky with my timing to catch this seagull landing
Bird's nest in the rafters of a building near Loch Lomond. Awww :)
A seal sticking his head out of the water
A robin near to Loch Lomond
Nature
On our descent on the last day we came across an enormous boulder sitting in the middle of the path, either deposited by a glacier or dislodged from the mountain above. Like most other rocks in the area, it was gabbro rock, a plutonic (slowly solidified igneous) rock with lots of crystals (largely quartz), making it ideal for rock climbing. Of course, we couldn’t resist! Since it was only a couple of metres high the hardest route up I could find was something like a V0, though lots of crimping and palming was necessary and the harshness of the rocks shredded our hands.
Gabbro boulder. Even with a sit start the hardest route was probably only a V0
What a climber's hands should look like!
We also spotted a halo rainbow around the sun. These are different from normal rainbows as they appear when the observer is facing, rather than facing away from, the sun. The colours are also reversed – red is on the inside of the ring rather than on the outside.
Halo around the sun ('sunbow'). Not technically a rainbow.
Miscellany
We found a spent bullet case on the path, marked as a .270 Winchester round, used extensively for hunting, though apparently Skye was once used for military training.
Spent bullet case
Bullet case markings: '.270 WIN'. The markings on the top of the rim look like Russian letters
Evenings were dedicated to film watching, eating and general procrastination. We watched Stardust which was partly filmed on Skye, frequently recognising paths we had walked and landscapes we had admired on the walks. And since we were in Scotland, a haggis for dinner was obligatory!
I actually wrote most of this the day after my interviews but my Non-Disclosure Agreement (which ends tonight) prohibited me from posting this. So now in the spirit of full-disclosure, here’s how my interview went.
Applying for PhysNatSci at Corpus Cambridge means you get a choice of being considered by the head of Physics or the head of Chemistry. Considering my utter ineptitude when it comes to organic Chemistry I naturally chose Physics which meant I had to take a Physics test as well as have interviews (the chemists didn’t). Good thing is I didn’t have to sit the TSA…
Corpus Test [60 mins]. Non-calc.
Apparently ‘nobody finishes all the questions’ but it was well within the capability of most people in our set to do this in the time, and I did. I wouldn’t say 1 question every 6 minutes is over-ambitious; it’s probably just the college trying not to freak people out. Dr Sutherland said I did very well in the test and we didn’t discuss any of those questions (which they did discuss for the previous guy – I couldn’t help but overhear a bit). M = Maths, P = Physics.
M1: Estimate sqrt(101) to 4sf
M2: x+y = xy = 3. Find x^3 + y^3.
Was quite surprised with this answer!
M3: differentiate x^x and x^(1/x)
M4: Sketch y = x/(x-1)^2 and y^2 = x/(x-1)^2
Had time at the end so I found the turning point. Did this my personal way by dividing top+bottom by x and finding x coord of turning point of the bottom. I just dislike the quotient rule I guess. Too messy.
M5: A generalised Fib sequence is given by F(0) = 1, F(1) = a, F(n)=F(n-1)+F(n-2). For what values of a is this a geometric progression? Find sum to infinity.
Wrote answer as a = phi or a = phi – sqrt5. Latter converges.
M6: Sketch y = tan(x) and y = arctan(x) on the same axes. Hence or otherwise, find the integral from 0 to 1 of arctan(x)
For some reason that I still do not understand, I decided arctan(1) = 1 (and missed it when checking) so integrated with incorrect limits and used the wrong area of the rectangle. I hope that didn’t make me seem too extremely retarded.
P7: Sketch acceleration-time and velocity-time graphs of a parachutist jumping out of a plane, opening the parachute, then landing safely on the ground.
P8: Water is placed in a sealed vessel. What would happen to the pressure if all forces between water molecules were to disappear?
I wrote an expression for this using PV=nRT then converted n/V into (water density)/(molar mass of water in Kg) so P is only in terms of constants and the temp. But I overheard the end of the previous interview – they were discussing this question – seems like all you had to say was ‘P goes up because intermolecular forces are attractive’ (neither of which I actually wrote – damn).
P9: Light inextensible strings, masses forced to move up-down. Find a as a function of x and sketch the graph.
I panicked when I got a horrific 2nd order ODE that I couldn’t solve then realised I didn’t have to solve it (since I had to find a(x) not x(t)). I was surprised to find a was infinite at x = l but it kinda makes sense considering tensions.
P10: Force F pushing againt 5 blocks: F -> ■■■■■. Acceleration a to the right. Draw all forces. What is the resultant force?
P11: The radius of the Earth is about 4 times the radius of the moon. What is the ratio g(earth)/g(moon)?
Used Gauss’ law for gravitational fields, complete with surface integral and symmetry argument to evaluate it. Thank you CAPS!!
Went out before and after Corpus dinner (which was excellent) and didn’t actually get to sleep until after 2am – I’m not great at sleeping in unfamiliar rooms/beds. I did manage to get this rather nice photo out of my bedroom window using nothing but incredibly steady hands and a ridiculous ISO:
Woke up at 8 for breakfast (of which I ate a disproportionate amount; again excellent) and spent the morning extremely unproductively in the JCR – the freshers who were helping put on History Boys… Got lunch (if I get in I will relish every meal), had an enormous cup of coffee and braced myself.
Corpus Interview 1 [30 mins, Dr M Sutherland and Dr S Bohndiek (latter from another college)]
1. Sketch the graphs of x^2 + y^2 = 1 and x^100 + y^100 = 1.
Interviewer said this was an easy warm up.
2. Show that z_n = exp(-x^2/2) is a solution to d2/dx2 (z_n) + x d/dx (z_n) + (n-1)x = 0. [something like that. No idea where n came from.]
Totally screwed this one up. It was a really trivial question – literally plug in the answer – but by the time I’d finished differentiating the thing several times I forgot where I was trying to get to so didn’t complete the final part – subbing it all in! From this point on they must have thought I was stupid and gave me easy stuff which really sucks.
3. Ice sitting in a glass full to the brim of water. The ice melts. Does the glass overflow? What will happen if the Arctic ice melts? Does this mean sea levels will not rise?
4. Estimate the change in sea level if everyone in the world went swimming in the sea at the same time.
Assumed Earth’s surface is flat without saying so – oops. Got about 10^-6 metres.
5. Integrate sin(x)sinh(x).
First talked about parts – and explained why it doesn’t work with sin(x) * sinh(x), realising (mentally) the problem reduces to 0=0 after two integrations by parts. Tried writing sinh(x) as e^x – e^-x then doing parts on each bit – works – can let I = integral and solve algebraically after doing parts twice; standard trick. I explained this doesn’t work for the first splitting because you get +I on both sides of the equation whereas with the second splitting you get +I on LHS and -I on RHS and the equation can be solved. Interviewer implicitly didn’t let me write anything down (“don’t do it – just talk about the method”) until they asked “how much do you know about complex numbers?” and my face must have lit up and I immediately said de Moivre and got the answer. Perhaps should have made it clearer that I hadn’t done it in school (but just happen to know of it and find it cool) since I needed to be ‘reminded’ whether it was cos + i sin or sin + i cos.
6. e^(i pi)
Awesome I got asked this :) I identified it as Euler’s identity and showed it from de Moivre.
I didn’t feel great after this interview – still kicking myself over being such a complete and utter retard for that differential equation / normal distribution question. People get executed for that sort of stupidity in China. Maybe that’s a good thing – cleans out the gene pool (much like Darwin awards).
Corpus Interview 2 [25 mins, Dr P Beattie and Dr P Cicuta]
At first the interviewer sat me down on this really uncomfortable chair which creaked a lot and I nearly slid off (like Hammersmith bus station) and said Corpus has 2 interviews for second opinions and in case one interview goes badly (so hopefully I managed to redeem myself).
1. What have you read about Quantum Computing? What problems do researchers face? How are they attempting to overcome these problems?
Talked about qubits and mentioned unit vector idea, introduced ket notation, talked about quantum parallelism but didn’t get onto Shor’s algo. Main problem is quantum decoherence. Evacuate experiment, cool with either other large ions or lasers. I could have gone on for a (very) long time but didn’t…
2. You play the violin [yes]. How would one work out the frequency of a string vibrating? Would a change in air pressure affect this frequency?
I remember seeing v = sqrt(T/(linear density)) somewhere once before so used it.
3. A standing wave is set up in a tube full of air sealed at one end. Draw the standing wave. What is the frequency of vibration? How would a change in air pressure affect the frequency? If an entire orchestra were playing and helium were pumped into the room, what would the audience hear?
Wind instruments go higher, string instruments don’t. Orchestra would probably get a bit out of time (brass and wind tend to be slightly out of time unless they correct for time delay of sound getting to them so their correction timing delay would be wrong) but I didn’t mention this.
4. What is the frequency ratio of an octave? a fifth? If you go up twelve fifths, would you go up an integer number of octaves? [Not quite]. How does the piano overcome this?
2x, 1.5x. (3/2)^n is never an integer. Well-tempered klavier; semitones are a lie!
5. Estimate the fuel effiicency of a jumbo jet and a car [litres per (passenger mile)]. Comment on your answers.
They seemed happy that I guessed the unit right but I couldn’t estimate the volume of fuel a jumbo jet would use – I attempted a really unintelligent method of getting at the answer by comparing the time it takes to fill up a jumbo against that to fill up a car. Interviewer suggested just saying it takes one tanker to fill a plane.
Turns out efficiencies are about the same, but I pointed out the two types of transport don’t exactly compete – you wouldn’t take a jumbo for a journey conceivably doable by car!
6. A yo-yo and a rock are dropped simultaneously. Which one accelerates faster? Why?
First the idiot in me used the extremely clunky and inelegant moment of inertia argument and obtained an expression for linear acceleration after drawing a force diagram. I offered to work out I for yoyo by integrating but interviewer said don’t bother. Interviewer then asked me whether there’s an alternative argument. I said energy. I tried to make it clear we hadn’t done circular motion properly in school yet but I said I was guessing formulae by comparing with linear stuff (esp. rotational energy E = (1/2) I w^2) and he seemed to agree with me. Ironically in the very mechs lesson I missed to go to interview AJM taught this stuff.
Dr Beattie said it was very good at the end – nice feel-good to end whole experience with which put me in a good mood for the rest of the day, though possibly it was just a horrible mind trick to give failed candidates a good feeling about themselves. In each one both interviewers alternated asking questions (they were very deferential about who asked the next question!)
Overall – despite the illusion of having not failed too much, which made me think it had all gone swimmingly, thinking back, there wasn’t a single hard question which was really quite concerning – nobody doing both physics and FM at SPS would have found any of that remotely difficult. Hearing what other people who also had Cambridge interviews said, it seems like everyone else got an opportunity to show off (bouncing balls losing energy at each bounce, infinite ladder of resistors linking to the golden ratio etc.) whereas I may well have come off as a stupid exam-factory-drilled robot who can only do bog standard questions on topics. I also didn’t get to talk about stress-energy tensors, semiclassical gravity and black stars (cf. one of the most awesome SciAm articles published recently) which was also annoying. Both interviews were friendly – the second was extremely so, and the first possibly a little less; both were formal and at desks – no armchairs/sofas etc.
The plan: if they gave me easy stuff for the reason I think they did, I’ll go to Stanford whence I have an offer… And since I am an avid rock climber t’would be all the more awesome.
Most of the other people applying to Corpus (nobody that I know of from SPS or SPGS or indeed any other school I know well) said they found the test and interviews difficult – but as Matthew pointed out, apparently a Game Theory analysis suggests the strategy that if you’re weak, act strong and if you’re strong, act weak. Considering everyone was applying for hard sciences at a top university it wouldn’t surprise me if they were mostly just good game theorists in addition to good scientists.
I get the decision letter (and possibly email) tomorrow. Eep.
I’m back from my last winter walking trip with the school (to the Lakes), and it was quite definitely one of the best trips I have been on! Here are some things I picked up on when I was there – hopefully this will be useful for whenever I next go hiking in winter.
Ice Formation
We noticed this rather interesting phenomenon on the first day on Skiddaw (931 m):
This is actually just a wire fence - it's quite incredible.
Apparently the reason for this is that as the wind blows across an object, little bits of water vapour condense on the surface of the object. If it’s cold enough (which it was) the water freezes immediately on the side of the object the wind is blowing. If this goes on for long enough with a constant wind direction, you get massive ice chunks several inches long pointing in the direction of the wind. Cool huh?
Batteries
Apparently the Gold DoE guys were advised that “batteries run out faster when cold”, and therefore that they should put electronic devices in their pockets to keep them warm. A little thought reveals this as a half-truth; batteries produce a voltage due to an electrochemical reaction (cf. my inorganic chemistry notes!) and a reduction of temperature reduces the rate of reaction, reducing the size of the voltage. So it is true that batteries perform worse in the cold and that one can increase their performance by heating them up; however since the reaction is taking place slower, they are actually being used up more slowly so I guess it’s inaccurate to say they ‘run out’ faster (their output voltage falls to most devices’ threshold faster but they don’t lose energy faster, so I guess whether they ‘run out’ faster is interpretation-dependent).
I thought the effect would be pretty minimal, but considering it was about -5°C (with wind-chill bringing it down to below -20°C), it wasn’t all that surprising I went through 3 packs of batteries on the first walk! Rechargeable batteries are extremely poor in the cold, partly because they start off below 1.5V, and probably also to do with greater sensitivity of rate constants to temperature etc. (stuff we haven’t yet done in chemistry). My Duracell Alkaline batteries were also pretty rubbish; the only thing that lasted long in the cold were GP “Super” Alkaline batteries (0% Hg/Cd) given to me by Dave. They lasted the whole of the second day.
Waterproof Trousers
After this trip I won’t say a word against these things ever again for a very good reason: there’s only one (good) way of going down an icy slope!
Thermos Flasks
These are unbelievably useful. The ability to sit down and sip warm tea at the top of a mountain where spit goes ‘chink’ (ok it wasn’t *that* cold) is really quite something. Plus don’t use a camelbak system. Really don’t.
The water in the Camelbak tube froze. In fact even the top of my Sigg had to be defrosted.
Buffs / Balaclavas
Wind-chill is the main problem when walking across ridges, and scarves simply don’t cut it when it comes to face-protection. Mine kept getting tangled and falling off my face and directing my breath up onto my glasses where the condensation just froze onto the lenses making seeing rather difficult! So yeah – I’m getting a proper buff for next time. Also, speaking of wind-chill, ski-goggles are also useful even when not skiing.
These guys had the right idea! Someone pointed out they look like they've come straight out of Halo...
Today concludes another fantastic week working at Imperial. This post will probably be a lot less massive than the previous one owing to time constraints (I’ve just come back from several exhausting hours of rock climbing at the Westway and Google Calendar tells me I have my driving theory test at some point in the near future).
Firstly, some pics to support stuff from my last post.
The entire table looks like this - I can understand why everything needs to be realigned and tweaked every 15 minutes for the experiment to work! The two blue lasers are I think the main cooling lasers, pumping from the ground to the high energy levels of Ca+.
This is a used Cu O-ring (actually called a gasket) - you can easily see where the knife edge bit into the Cu making a vacuum seal
A top view of the laser setup. You can see the diffraction grating (with an arrow drawn on it) and the connections to the piezo behind it. Click to embiggen.
Equipment
Tantalum Oven
This is the equipment used to produce neutral atoms which are to be ionised.
The oven is suspended between the two electrodes by a Ta wire. The Cu foil is there for a test run of the oven - if it works we should be able to see a spattering of grey Ca on the Cu.
This is the plate on which the entire experiment (ion trap, oven and all) will sit. It will get inserted into one of the holes in the central 6-way cross can.
When I first heard they were going to use an oven, for some reason I imagined some sort of miniature baking oven that somehow emits atoms when turned on! The actual oven is actually a tiny 1cm long tube of tantalum (Ta), sealed at one end by essentially squashing the end, with a tiny hole in the middle of the tube. Ca shavings are stuffed into the open end before the oven is closed, again by squashing. The whole oven is attached by a piece of Ta wire to two electrical contacts across which a potential is applied. The Ta conducts current and heats up, acting as a heating filament. The Ca heats up and the most energetic atoms spit out of the hole (the process is basically evaporating the Ca at very low pressure and high temperature).
I asked why Ta is used – presumably Tungsten (W) has virtually the same properties in that it heats up when current flows through it, and since W is the metal of choice in light bulbs, presumably it’s cheaper? Apparently W can indeed be used; for such applications the criteria for metals are that they are UHV-suitable (don’t trap/adsorb other molecules/atoms on/to their surface which subsequently outgas, ruining Ultra-High Vacuums) and won’t melt at high temperatures. However Ta is normally more suitable than W because it’s more malleable (whereas W is very springy) and can be easily spot-welded (to stick the wire onto the oven). However thoriated W is better than Ta as an electron source since the thorium gives it a much lower workfunction, allowing more electrons to pop out for the same energy input.
Vacuum Pumps
In my previous post about this work experience I omitted some detail on the pumping that I learnt this week. As it turns out, the actual pumping requires three pumps. The first is a roughing pump, to get the pressure down to a very rough vacuum (~10-2 mbar). Here they were using a rotary vane pump:
This image was nicked from wiki
Essentially as the off-centre internal cylinder turns, the vanes get longer / shorter accordingly such that the pressure at the input is always getting lower and at the output it’s always getting higher, forcing the air out of the output. The principle is essentially PV conservation.
The second stage is a turbo pump which is basically an electrical version of the intake fan of a jet engine. It spins extremely quickly (so quickly that it requires a low pressure to operate lest it smash itself to pieces) and the idea is that it spins so quickly that any molecule that hits a spinning blade hits the part of it such that it gets kicked outwards, away from the vacuum. This gets the pressure down to about 10-5 mbar. The final stage of course the ion pump.
When air is pumped out the can sits in an oven - the idea is to heat up anything that can outgas while pumping, making it outgas more, thus getting rid of 'outgassable' stuff
Wavelength Tuning using Iodine
There are several ways of tuning wavelength (I wrote something about the cavity method – setting up a standing wave – in my previous post), but I found this way of doing it particularly interesting. Like all other elements, iodine has a certain absorption spectrum, a feature used in star spectroscopy to determine elemental composition. But instead of doing what astronomers do (measure wavelengths to identify elements), here we were using a known map of iodine’s spectrum to tune the wavelength: light shining through the iodine has a certain attenuation which is dependent on the wavelength (owing to electron energy levels). By shifting the wavelength around using a piezoelectric it is possible to obtain a local iodine absorption spectrum (wavelength against intensity). By comparing this local spectrum with an ‘atlas’ – iodine’s spectrum for a large range of wavelengths, it is possible to locate the local spectrum within this atlas, thus identifying the wavelength. Apparently a narrow band of local spectrum is sufficient to identify a unique location in the atlas: there are no ‘repeats’. Whether this is non-repeating property is specific to iodine (hence its use) I’m not sure; the isotope used is radioactive so there must be some really good reason to want to use it!
Techniques and Procedures
Saturated Absorption Spectroscopy
All atoms radiate photons. However in a cloud of atoms these photons are affected by the Doppler shift owing to the random movement of the atoms, and a graph of frequency against intensity (basically a spectrum) shows an underlying distribution for this radiation. However the interesting bit of spectroscopy occurs on the surface of this curve, in the form of ‘ripples’ on the underlying curve’s surface. While a human can normally see the ripples roughly by eye, the underlying curve gets in the way of accuracy.
The solution is a method of somehow obtaining the underlying distribution without the ripples using lasers and subtracting this curve from the spectrum, resulting in a graph of just the ripples. I’m still clueless as to precisely how this works / is performed since I didn’t personally bear witness to the process (I heard something about matching lorentz curves to points but that was probably more to do with analysis of the ripples rather than the process of saturated absorption spectroscopy) so it looks like some wiki-ing is called for.
Walking the beam
This isn’t some physicist’s attempt to be a pirate and getting the words muddled; it’s actually a rather clever (though extremely time-consuming) method of aligning a laser beam. Bascially the ideal situation is a laser beam passes precisely through two points. This is very difficult to achieve with just one stand so a setup with mirrors is necessary. Here are several different failed attempts at diagram-ifying the thing:
The dotted lines were added by me to show where the beam will go
At each of the two points the beam needs to go through an adjustable iris is placed (think circular doors in sci-fi films), and mirrors alpha and beta (making up the periscope) can be adjusted so the beam’s height (h) and angle of elevation (e) can be adjusted more or less independently. Then the following two-step process is iterated until the beam is almost exactly where it needs to be.
1. Open B completely, close A so it becomes a tiny hole, and adjust the laser so it goes through A using mirror alpha
2. Open A, close B so it becomes a tiny hole, and adjust the laser until it goes through B using mirror beta.
Illustrations of the steps are as follows:
For some reason it reminded me of numerical analysis / Newton Raphson type things – constantly optimising and getting closer and closer to perfection yet never reaching it. GL’s cobweb illustration of numerical analysis seemed particularly similar to this situation. Anyways while I quite like how it works, walking the beam does start to lose its novelty after doing it for a couple of hours…
Scanning Tunnelling Microscopy
Danny also explained some awesome stuff on this and how it works. Basically the idea of STM is to use quantum tunnelling calculations to make a map of a surface. A probe is held (say at +5V) very near a surface (grounded), and owing to quantum tunnelling, a certain current flows between the probe and the surface. This current is proportional to exp(-l) (or something like that) so it is possible to measure l to a very high degree of accuracy. As the probe is scanned across the surface, a matrix of measurements of l against (x,y) can be created, thus mapping the topology of the surface. This mapping can in fact be so accurate that it can pinpoint individual atoms sticking out from / adsorbed to an otherwise flat surface.
Conclusion
The last two weeks have been nothing short of awesome. I’ve learnt (and sometimes noted down) many new things on every one of the last ten working days and I’ve recounted here and in last week’s post merely a handful of the more interesting bits and pieces. I even solved an apparently insurmountable practical problem thus moving the entire scientific community forwards! I mean … I came up with a (pretty good) solution to unscrewing a stuck nut… Many thanks to Danny Segal for giving me such a wonderful opportunity.
5W Green Laser used for pumping Titanium-Sapphire Laser
I’ve been looking forward to this for quite some time – two weeks of work experience in a lab at Imperial College working with some PhD students with an ultimate goal of making some progress towards the construction of a quantum computer that doesn’t take tens of man-hours to perform each calculation. After a week I feel I’ve learnt a lot about formal lab work and large-scale experiments (*slightly* different from the 20-minute assessed practicals from AS!) and about the general physics and concepts behind some of the experiments and equipment – I’ve been (not so) conscientiously filling pages of my notebook with messy notes and cryptic diagrams so hopefully some of the stuff I write here will make some vague sense and not quite directly contradict truth.
There are also several interesting bits and pieces lying around the place. There’s an enormous Newton’s Cradle in which each ball looks like it could be heavy enough to be a ship’s anchor. There are also enormous capacitors lying around everywhere for the people working on high-density fluxes.
Capacitor banks lying around
The Building
The Physics / Maths / Computer Science part of Imperial is somewhat bizzarre – from what I gather it consists basically of two adjacent buildings which were built at different times and were haphazardly connected together by knocking down bits of walls. Unfortunately the actual floor levels are out of alignment and the floor heights are also different, which means there’s a crazy staircase joining the two buildings together and floors 6 and 7 in one of the buildings had to be rechristened 6 and 6M for the sake of keeping the numbering consistent with the lifts. There are also only connections on certain floors of each building so it’s possible to leave the Blackett Lab on the bottom floor, go up one level and be confronted with a solid-looking wall where the connection should be. As if things aren’t crazy enough, there’s a set of lifts placed almost exactly at the junction (so to speak) between the two buildings, making it really confusing to navigate the whole 3D maze. It’s pretty good fun actually!
The Lab and Equipment
Optics
I was quite surprised when I first saw the lab – I was expecting a Leonard Hofstadter style lab (as seen on The Big Bang Theory) but actually quantum computing with ions (ions therefore being the main focus of most of the projects which I’ll come to later) involves a fairly large amount of optics work, so each of two adjacent, connected labs I was working in has an optical table as its centrepiece littered with lasers and ridiculously complicated setups of mirrors and lenses which have been tuned very accurately to direct laser beams into tiny optical fibres and whatnot. Speaking of accuracy, the setups are so sensitive to small shifts that they need to be tuned almost constantly. The PhD students told me they detect a lot more drift during the daytime when other experiments are going on in other labs which release radio waves and traffic is rumbling overhead (despite being two floors below ground level and over a block away from a small road) than at night when there is less activity.
The equipment is also sensitive to tiny temperature fluctuations. Most of the lasers are basically diode lasers:
It’s a fairly standard laser setup in which electrons and holes come together in the depleted region between n and p type semiconductors and then either wait for a nanosecond or so before annihilating and releasing a photon (spontaneous emission) or get hit by a photon, resulting in stimulated emission. What was experimentally interesting was that the cavity length in fact determines the wavelength of the laser owing to the fact that a standing wave needs to be created which ‘fits’ exactly in the cavity (a whole number of half-wavelengths need to fit in the cavity) and this is sensitive to temperature. So each laser box has four BNC sockets: one for providing the laser with electricity, one for a thermistor which is hooked up to a feedback loop system which regulates temperature using a Peltier junction heat pump (which occupies another socket on the laser), and one for a piece of Piezo (placed on the diffraction grating) which can change width depending on the voltage across it (or maybe current through it, or something) thus allowing the cavity length to be adjusted, though my suggestion to manipulate the piezo in the feedback loop to compensate for temperature changes would fail since the temperature-dependent expansion of the cavity is several orders of magnitude greater than anything the piezo can correct. When I heard that I was pretty astonished the laser cavity had to be adjusted to such an exact length – several orders of magnitude more exact than the expansion of a bit of metal when raised by a few degrees. The entire laser is covered by a thick black piece of foam to protect it from temperature fluctuations in the room.
Electromagnets
It was pretty cool to find out that I was to be working in the same room as a 2.5 Tesla electromagnet! Ion trapping, as I will also come to later, involves not only charge and potential fields but also magnetic fields, so the Penning Trap the researchers there were using was sitting inside an enormous superconducting electromagnet.
The superconducting electromagnet uses liquid He to keep cool – as a sidenote I asked why they (and CERN) use cool superconductors (more expensive liquid He) instead of the more recently discovered crazy warm ones (cheap liquid N2); the reason is because above a certain current, superconductors end up failing and develop some resistance causing heat to be produced resulting in a quench (the He boils off, expands to something like 15x its volume and the whole can explodes in a fit of freezing fury), and the cool superconductors can carry a much higher current before this happens, allowing more powerful electromagnets. Of course this comes at a very high cost. As can be seen from the diagram, the He (at ~4K) is shielded from room temperature by a layer of liquid N2 (at a balmy ~77K). The He needs to be replaced about once every couple of months, while the N2 is replaced about twice a week. The superconducting coil, power supply and cables are eventually going to have 80A coursing through them – a truly formidable current!
Refilling with N2
N2 is very cold!
Apparently the way they get the electromagnet to start conducting current is to simply arrange the coil in a loop – they can’t expose the 4K superconductor to air, so it is necessary to induce the current in the superconducting coil. Once this is done, the power supply can be switched off and the current in the superconductor just keeps going round (owing to the lack of resistance), allowing a very strong noise-less magnetic flux to be produced (the flux’s precision is something like 10-6%)
Vacuums
This was particularly new to me. I’d never worked with 2.5 Tesla or 5W lasers before, but while I’ve come across magnets and lasers in experiments, I’ve never really observed experiments involving vacuums before (apart from the bell-ringing-in-a-jar/gerbil-squeaking-in-a-jar one to show sound doesn’t travel well through a near-vacuum). There’s a lot of novel (to me) and interesting experimental stuff that goes on here.
Basically the idea of creating a seal when joining two flanges together is to use a copper O-ring. Each flange has a ‘knife edge’ (90° very sharp edge) and when they’re pressed together with a Cu O-ring in between, the knife edges cut into the soft Cu; thus the Cu itself becomes the seal.
While flicking through Inward Bound by Abraham Pais (recommended by CAPS) I read about various attempts at making a good vacuum pump. Modern technology has come a long way since the mercury-filled jar, and now creating a very good vacuum is a multi-stage process. First all the equipment is cleaned thoroughly – for some reason fats and oils from people’s hands (for example) are disastrous for a vacuum so everything needs to be wiped squeaky clean with something like acetone or isopropanol. Then everything is sat on the optical table which has a source of clean dust-free air on the ceiling which constantly blows on the equipment, keeping dust off and constantly cleaning it of bits of dust that have settled. Then everything is put together using gloves, nuts, bolts, Cu O-rings and *a lot* of effort (believe me, putting flanges on sideways while stopping the Cu O-ring from slipping out is infinitely more difficult than measuring SHM of a cork in a tub of water – reference to AS practical; one of the researchers also described putting He into the cannister having first cooled it sufficiently to stop everything boiling off immediately as a dark art rather than a science). The air is pumped out using a conventional pump until the pressure inside is something like 10-6 millibars, at which point an ion pump is turned on to essentially evacuate the remaining air molecule by molecule. The pump essentially ionises the gases inside the chamber and use charged plates to attract them out. The final result is a very good vacuum.
The Projects
Photon Ionisation
There was a MSC researcher from Germany sharing the lab with the PhD students from Imperial, and he was working on a different method of ionisation. The supervising prof, Dr Danny Segal (a reader in Quantum Optics), explained that the previous approach to getting ions was to use a ‘splat gun’ approach – basically a stream of neutral atoms from an oven hits a stream of electrons from an electron gun, and those electrons will tend to knock out some electrons from the stream of particles, resulting in a few ions. This has a few problems: lots of atoms never get ionised so end up getting deposited on the side of the chamber, screwing up the shape of the potential well in the ion trap; lots of electrons end up floating around in the chamber and get deposited on insulators, again causing irregularities in charge distribution.
The German MSC researcher was working on using photons to create these ions – a much more tenuous stream of neutral particles is projected into a beam of photons which, via the photoelectric effect, knock out electrons creating ions. This should have a higher rate of ionisation leaving fewer ‘waste’ atoms sticking to the inside, and the number of photoelectrons knocking around the chamber should be much lower than the number of electrons being shot from the electron gun. I suggested the photons might knock electrons off other bits of the apparatus, again screwing up the flux; apparently this should happen infrequently enough to allow a reasonably controllable flux, though some researchers using a Paul trap (involving an oscillating EM field) apparently detected ionisation using photons of the wrong frequency for direct ionisation leading them to believe electrons were being knocked from the apparatus and these, accelerated by the oscillating field, slammed into atoms causing ionisation.
Anyways the setup was more or less thus (a picture is worth a thousand words):
The way to ionise these Ca atoms is to first use a laser to excite the atoms – push some electrons up to a higher energy level. The UV LED then does the actual ionisation from that energy level. The picture above is of a half-finished setup (optics haven’t been sorted out yet and there are two unsealed flanges).
Laser cooling
GSM/KPZ gave us an article in class last year about laser cooling (‘Cool things to do with lasers’, Ifan G Hughes et al 2007), and it turns out it’s useful for Quantum Computing – a jittery ion is presumably pretty bad for physicists who want a stable wavefunction. Well, here’s the setup.
Click to embiggen
It’s in fact mostly about using lasers to manipulate electron energy levels in a Ca+ ion:
The Ca+ ion has an energy level electrons can fall down to (RHS of diagram) where they would stay for quite long before falling back down which is undesirable considering the cooling involves shuttling electrons between the leftmost levels (in the diagram). So four red lasers are required to pump those back up to the top energy level.
QED
I’m not really sure what’s going on in this experiment but basically, since QED is only significant at high charges (something like that), the researchers go to GSI to conduct this research. The idea at GSI is to slam super-high energy ions through a gold foil which apparently strips them of all electrons. Different ions are separated via a very similar system to how a mass spec works.
Some Other Physics-ey Stuff
Ion Trapping
There are of course lots of different methods of trapping ions – I mentioned one in my post about the UCL antimatter lecture. Apparently it’s provable from Maxwell’s equations that it is impossible to create a static 3-dimensional potential well to trap ions, so there are currently two main methods: using a purely electromagnetic system (using either some feedback system to wobble the ions towards the centre of the trap or a constantly oscillating field like in a Paul trap), or to use magnets:
A cation is sitting at the bottom of a potential well in the z direction. It is surrounded in the xy plane by oppositely charged plates. As it is attracted to the plates, the z-directional magnetic field causes it to move in a circular motion (as seen in cloud / bubble chambers to determine momenta of ejected charged particles), represented on the diagram by ‘micro OOO’. The charge on the plates are then somehow tuned to make the large-scale motion of the particle resemble a circle and so it eventually loops back on itself, so its path shape looks like what is labelled in the diagram as ‘tuned, get O’
The Ca+ Ion
The actual quantum computation to be done with the Ca+ ion (not a typo: just one +; this isn’t chemistry!) involves electron energy levels. An electron can be in one of two energy levels, and that is the qubit. In Ca+ there are two more or less independent distinct situations in which an electron can be in one of two energy levels, allowing two qubits to be encoded into one ion.
The use of this isn’t only to cram more qubits into fewer ions (I read a research group somewhere is making base-5 ‘qudits’ using microwaves and superconducting things) but also to allow easier entanglement – since both qubits are in the same ion it’s supposedly easier to make them interfere in a predictable manner, which allows a quantum NOT gate to be set up which is critical to quantum computing; supposedly only two research groups in the world have managed to get this quantum NOT gate to work.
Ion hopping
The biggest limitation apart from the sheer fiddly-ness and slowness of everything in the quantum computing world is the fact that it’s impossible to put more than about 8 ions in one trap before they start screwing up each others’ wavefunctions. The PhD researchers had previously been working on a solution to this problem that the theorists came up with – getting the ions to hop around in the trap, thus manipulating each ion more or less individually. This has already been done using Paul traps (I think) but the researchers here were trying to use Penning traps and show they are in fact better for quantum computing (or at least can do the same things as Paul traps).
Overall
There’s a lot more I would say if I had the time but as with all blog posts, you’ve got to stop somewhere. But overall I’ve never done modern practical physics before (at UCL we looked at some particle traces on the computers which is the closest I’ve really got so far) so this is a pretty damn amazing experience for me, hence the mega-post.
Last week I was in Cranfield participating in the Aerospace Challenge Finals. The challenge this year was to come up with a design for a device to drop humanitarian aid accurately (within 20 metres of a target) from 3000 metres up. Our idea managed to make it to the finals which turned out to be a week of lectures on general aerospace engineering, activities and flying! Photos are here.
Flying
Each person got two flying experiences, both of which included some time piloting the aircraft: about 10-20 minutes in a helicopter and about half an hour in a fixed-wing plane.
My first flying experience was with a small Robinson helicopter, which can only really be described as terrifyingly, exhilaratingly awesome. The pilot managed the take-off which was one of the most breathtaking experiences I’ve ever had – in a helicopter you’re literally sitting in a big transparent flying bubble with the engine behind you, so the view and experience is truly amazing as the land falls away beneath you… I later took over and found control extremely difficult – even a tiny movement of the stick causes the vehicle to tilt violently in that direction making a beginner like me very prone to overcorrection leading to a serious case of increasing-amplitude SHM! The actual stick is situated between the pilot and the copilot and a rotating handle is stuck on the end allowing dual control, so my rather flailing and uncontrolled flight was abruptly and expertly rectified when the pilot took control (though not before I turned and prepared to land by erratically lurching towards a patch of grass). The pilot then demonstrated some cool things one can do with a helicopter including skid landing and take-off, going backwards and sideways while spinning etc.
Here you can see how control over steering is shared between pilot (me) and real pilot (instructor)
The next day I got in a PA28 – my first fixed-wing experience. The pilot had to go through an enormous list of things to check before taking off and explained a little about what she was doing (mostly checking the engine could rev at certain RPMs and wouldn’t give out in certain situations, flicking on and off various lights and calibrating [and pointing at] instruments). The runway was also ridiculously long so she didn’t even bother with flaps for takeoff. This was much easier to fly than the helicopter and the dials and instruments in the cockpit didn’t obscure the view as much I had inferred they would from MS Flight Sim’s portrayal. I did a few rather ginger turns and pitch adjustments before relinquishing control back to the pilot who then demonstrated some steep banks, a stall (which sounded dangerous and seemed to imply the engine cutting out) and a dive (which was extremely cool). Later that week Matthew and I were inspired enough to ask about possible places to get flying instruction – flying has always been one of those things I’ve wanted to learn but I’ve always ended up not having enough time or money to start…
Here the instructor is doing a steep bank. She even did a pretty steep dive totally relaxed and with that pen in her hand!
Me flying the PA28!
Activities
The week started with some group leadership exercises which consisted of attempting to place 30 cards in the correct pattern (easy) and work out the shape and colour of two missing shapes while blindfolded (hard) – both were much more enjoyable than I had expected from that genre of exercises.
The first engineering challenge we were given was an egg-drop challenge – the idea was to construct a package which will protect an egg from a drop of 4 metres. We were given limited materials and each material had a price; the idea was to make the cheapest package that doesn’t crack the egg. Our attempt turned out to be the most epic non-fail in history – literally seconds before the end of the construction phase we managed to pop two balloons which made us completely change our plan and in the last few seconds and in great haste we crammed stuff into a crumple zone and added a parachute … and it somehow worked and turned out to be the cheapest package (if wastage is deducted)! I guess that really proves the KISS principle: Keep It Simple Stupid.
The second engineering challenge was along similar lines – dropping aid – though it was from a more macro perspective. The game was called ‘airlift’ and sold by Elite – the idea was to plan an air route through several African villages which uses the least fuel, while dropping packages of aid which we had to construct out of wooden blocks, paper and tape while making sure everything fits in the cargo hold. The first thing I pointed out when time started was that both problems were NP-complete: the packing problem was almost exactly the same as the knapsack problem and the route planning was basically the Travelling Salesman problem with fuel added in as a factor. In other words we had to be either very good at intuitive problem solving or somehow get lucky. As it turned out, as perhaps a combination of the two, we somehow managed to come up with both the the optimum packing configuration as well as the best route, and finished literally as the final buzzer went – not bad!
The rest of the week was dotted with things like paper plane competitions (which included an awesome flying paper ring which seems impossible when you first see it fly), a game of (actual) CTF and some sports.
Lectures
Over the week there were daily lectures. Much as I would love to discuss them all here in depth I haven’t got that much time / space and besides most people aren’t as interested as I am in the effect of negative angles of attack… But I’ll go a little into some of the most interesting lectures.
Fly by Wire (FBW)
The problem for a long time had been that when going sufficiently quickly, adjusting the controls from the cockpit was really quite hard work – the air going past has so much momentum and the mass flow rate is so high that to change its direction by (for example) adjusting the ailerons requires a lot of force. To make things worse, at supersonic speeds a shock cone is developed (some awesome videos of this are on Youtube) – if this touches the aileron the stick can be wrenched out of the pilot’s hand. Some of these controls were partially solved by making the stick adjust small tabs in the wing instead of the entire aileron, reducing the force required to steer, and by making controls non-reversible (force on the aileron doesn’t affect the flying stick). There are of course some problems with these such as lack of ‘feel’ of the controls. So recently manual stick-aileron transmission was replaced with an electronic motor which receives instructions from the cockpit and adjusts the ailerons itself. Not only does this take all the strain off the pilot, but it also allows a computer to neutralise bad judgements on the part of the pilot such as initiating a sharp dive at 50 feet, implemented by a feedback mechanism from the aircraft to the computer. It also simplifies the cockpit – instead of filling the area with controls, dials an instruments, a computer screen with a joystick and throttle suffices to fly a FBW plane. I asked whether, since FBW significantly reduces the pilot’s direct control over the aircraft, FBW might actually make complicated manouevres more unsafe or indeed completely impossible. John Farley, who was giving the talk, said that, from his vast experience, pilots, however experienced, cannot really be trusted to fly planes safely all the time, and in fact he would feel safer trusting a computer’s judgement and letting a computer do such manouevres than a pilot. That talk also proves that a Boeing 747 probably has non-reversible controls so that scene in Snakes on a Plane (I think it was that film) in which the pilot asked the co-pilot to help pull back on the stick very hard was probably a load of rubbish. Not that you needed to be told that.
Basic Aerodynamics
One of the interesting things from this talk was the reasoning for why helicopters don’t go fast. There is always one part of the rotor going forwards, and if the helicopter moves forwards sufficiently quickly that part of the rotor travels at supersonic speeds generating a shockwave that could rip apart the rotor. In addition, even at lower speeds, there is an imbalance between the airspeed of the fowards-going part and backwards-going part of the rotor meaning a gimbal has to change the angle of attack of the blade depending on which way it’s going: the angle of attack of the rearwards-going blade has to increase to increase lift on that side otherwise the helicopter would just roll over. Of course, there is a maximum angle of attack this blade can be set to before it stalls which is about 20°. This limits the helicopter’s speed at subsonic speeds.
An RAF Hawk landed at the airstrip for us - here is the pilot demonstrating how the entire tailplane rotates
Automation and the future
This was probably the most interesting talk of the week; unfortunately it was cut short for us owing to a jetstream flight. Apparently currently pilots of Euro Fighters get sensor fused info presented to them in the form of advice as to what to do and they simply act upon that, which means half the time the plane is telling the pilot what to do: it is telling the pilot how to control it: semi-automation. Even in commercial aircraft a system called TCAS (Traffic Collision Avoidance System) senses other aircraft and advises the pilot on how to manoeuvre. There is clearly room for improvement: unmanned aerial vehicles are coming. This of course led to the whole humans v computers discussion but for every example of a pilot doing something heroic and saving the plane, there are several examples in which pilots screwed up and computers would have saved lives – Chris Roberts, the speaker, asked whether it *really* is desirable to have a pilot flying the plane, and whether the problem of pilots becoming de-skilled from letting the autopilot take over really is such a problem after all. I also found it very interesting and surprising that currently many landings of commercial aircraft are performed by the autopilot in low-visibility situations.
Anyways overall it was a fantastic week. Whatever the results of the competition turn out to be, I for one got a lot out of six days in Cranfield. I learnt a lot, made some friends, made some good contacts in the industry, and had some great fun relaxing in the English countryside!
Posted by arctanb 
