ESA CanSat Competition 2010

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.

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5 Responses to ESA CanSat Competition 2010

  1. Zahira says:

    Hi guys!!

    This is completely amazing!!! I was sure personally since I saw your progress that you were going to have the gold award. You were always the first to answer me, I saw your videos in youtube, you were even professionals speaking in front of the public and you did an amazing job. I know that you will go far in your professional career and keep an eye on the opportunities in ESA and the space sector!!

    Please send me these pictures to my private email account!! they are amazing!! And one with the trophy and the jury!!

    With kind regards,

    Zahira

  2. Liz Christmas says:

    Congratulations to the team! from a mystery relative in Ozzieland. Great achievement!

  3. Congratulations!

    What was the form of the (symbolic regression) calibration function for the thermistor?

    “We even ended up having to solve a horrific second order non-linear differential equation to get wind speed as a function of acceleration”. The horizontal force on the rocket will be some polynomial of wind velocity (probably with the quadratic term dominant), but how do you find the values of the coefficients?

    Also, your school physics technician has a PhD?

  4. arctanb says:

    Thanks :)

    James – the closest fit function when I stopped the search turned out to be:

    Temperature = (39.8795 * R – 1325580) / (61677900 / R – R – 33239.5)

    where R is the thermistor’s resistance.

    “We even ended up having to solve a horrific second order non-linear differential equation to get wind speed as a function of acceleration”. The horizontal force on the rocket will be some polynomial of wind velocity (probably with the quadratic term dominant), but how do you find the values of the coefficients?

    We had done experiments previously in which we had filmed a dummy CanSat (same weight as the actual one) dropping from a weather balloon – the footage allowed us to guesstimate initial conditions. We did however need to solve the differential equation to work out the CanSat’s expected trajectory given constant wind velocity to calculate useful data points.

    Also, your school physics technician has a PhD?

    He did his PhD in (I think) plasma physics and I understand he’ll be teaching a class next year.

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