The story of Project Stetind at EuRoC
Friday 8. Okt - Friday 15. Okt
Making a rocket is a lot of hard work. Before going to Portugal we had made a large effort to be as ready as possible. Unsurprisingly we were still not ready. Leading up to departure we had performed complete assembly of the rocket something like three times, but we still hadn’t resolved every issue that had popped up during assembly. They were things like misalignments between screws in the fuselage and the inner structure, camera misalignments and rod length adjustments.
Coming down to Portugal our biggest fear was that the shipping crate would not pass through customs even before the competition was over. Our team leader Hannah and a stalwart member Hege had something like 50 phone calls to try to get the crate through customs by the time we arrived. The Portugal customs, in the end, told them to stop calling. In a blessing in disguise, Hege was unable to make the last flight from Stockholm to Lisbon due to a ticket error. While she waited for her next flight, she got a call from customs requesting some final information. Had she been on the flight, this phone call would never have happened, and we would have lost what we afterwards know was crucial time to work on the rocket.
We arrived in Lisbon and started getting our rental cars. Hannah was able to go to the customs and wrestle the crate out on the street. While we had a huge crate with no means of transporting it, we at least had our rocket safely in our own hands.
As we dismantle the crate and stuff it into one of our tiny rental cars, the feeling of being on a long road of problem solving starts to dawn on us. While the imminent launch might seem a bit threatening, we are, after all, engineers, and to solve problems is our trade. At any rate, all of us are looking forward to an exciting event.
Saturday 9. - Sunday 10.
After driving to the campsite through the night, we wake up on a Saturday, refreshed and ready to work on the rocket. The weather is pleasing and relaxing, bordering on a bit hot, but we are nonetheless focused on the task ahead. For the next two days, we start assembling the rocket, this time with a zero tolerance for things being out of shape.
We adjust the holes of the airframe, adjust the lenses and adjust the camera-mounts. Soldering takes place.
We have to saw down the upper threaded rod a centimetre, cringing at the loud sounds of last-minute fixes. We accurately measure the CG and the weight of the rocket. Our calculations have brought us within a few millimetres and a few hundred grams of the actual value, which at a late hour like this, is a relief.
Monday 11. - Tuesday 12.
All this tuning takes surprisingly long, and before we know it, it is Monday, and the event is in full swing. While the other teams relaxedly show off their rocket and take their time explaining their systems, we feel like we have to constantly work on our rocket to be ready in time. Our launch day is set to Friday, but as expected, by Tuesday we are asked to fly earlier, due to other teams having their rocket stuck in the toll. We continue to work, but as small problems continue to slow our progress, we approach our new flight readiness review all too fast.
While the judges initially want us to launch the day after, on Wednesday, halfway through the flight readiness review, we get a somewhat disappointing, yet much needed remark: “Guys, you are not launching tomorrow”. There are almost no action items in the review, but the judge recognised that we needed time to make the small stuff work. Our cable management was unfinished. Lots of connections were unsecured. And we were missing a venting hole in the aft. Graciously, Paulo, our reviewer, told us he needed us to be at our best at launch day, and right now, we were not at our best.
One of the problems we encountered was that the payload’s intended power management solution did not work. It would not accept the signal sent from avionics to turn on properly, and this led to the following problem: In the design of Stetind, the payload is somewhat stupidly embedded quite deeply in the assembly-process, as the payload casing is a structural element for the inner structure. This did not allow us to quickly open and close the payload. And since the intended way for the payload to turn on did presently not work, it would have to be partially switched on before it was assembled into the inner structure. This was to happen many hours before flight, and presently there was not enough battery life in the payload to keep it alive until launch. As the payload team was macgyvering a solution with a power bank, the rocket team also had their problems.
Small tasks, like modifying the arming pins and attaching insulation to the boattail were being performed, but crucially, the mechanical team needed access to the entire structure with avionics and payload in order to fine-tune the interface with the outer structure of the rocket. With all the teams competing for the same hardware, progress on all fronts was slow.
Wednesday disappears in a fog of small problem-solving tasks. The cameras, for example, were due to some ridiculous ground sharing paths being fed power through the HDMI, which means it draws power when it is not supposed to. This problem persisted until launch day, and the only reason it did not fell the system was the avionics team’s cautious over-dimensioning of the Stetind battery pack.
In the background, the motor is being loaded at the launchsite, and food, refreshments and transportation is constantly being fed a smaller technical crew, who all need to work around the clock. In the middle of all the problem solving we are once again asked to launch a day early, this time on Thursday. Although we want to help the other teams, we realise we need the time to make our own rocket work. This decision to turn down the proposed new launch-window also means we are turning down the possibility of a backup launch window. We consider this, but decide it is better to concentrate all our effort on a single launch window, instead of rushing, and potentially wasting time on an unsuccessful launch, which could have been better used on problem solving.
In the middle of the afternoon on the day before launch, another last-minute accident happens. 15 volts is sent through one of our servos, frying it dead. With the reserve servo also suffering a different malfunction earlier in the week, we are left one servo short. We get much needed help from another team, Endeavour, who is in Lisbon, and can buy us a replacement servo. We get the servo in the night, and the team has to work until the morning to get the rocket disassembled down to where the servo is in the assembly process, and all the way back up.
Friday 15. Launch Day
When we all wake up at 05:00 launch day, some team members have gotten no sleep at all.
We drive to the launch site in the dark, and although it has been a lot of last-minute efforts, we are currently tracking no issues on our rocket. All is ready to launch, and just in time.
As we arrive at the launch site at 7 o’clock, the first step is installing the batteries into the payload. They have gotten the powerbank solution to work, which gives them an estimated 10 hours of on-time. After the batteries are installed, the mechanical team begins its lengthy assembly. The motor is being fetched, and installed, and the inner structure comes together, is laboriously calibrated, and avionics is slowly but surely fitting all the cables in place. A couple of small hiccups slows us down: The newly installed servo is a millimetre too big, and we have to resort to filing to get all the components to fit together. Not great, not terrible. The cabling bunches up on one of the joints, hindering assembly into the fuselage. Nothing a couple of strips can’t fix.
As the hours tick by like minutes, our launch readiness review closes in on us. We get it postponed by two hours. As the final deadline comes upon us, everything is ready, and we complete the launch readiness review quickly, with no problems discovered.
We are heaving the rocket to our shoulders as the flag switches to yellow, and we are allowed down to the launch rail. We walk down slightly nervous, but in good spirits. As we arrive, we realise we are not the only ones having problems. As we are loading the rocket on the launch rail, the nosecone of a Polish team pops open as it sits on the launch rail. A definitive scrub. The range manager tells us we are in good shape. Famous last words there, as we are tuning our GPS with our handheld receiver, a solder on the receiver breaks loose, disconnecting the battery. Without a GPS-receiver, there is a slim chance we will be able to find our rocket once it lands. After a flurry of discussion, we decide to try to run back to mission control and have the receiver soldered together. The only reason we get time for this is because the other teams around us are also struggling. The soldering iron is heated as Andreas, one of the launch crew, runs back to get it fixed. We get it soldered, and as he comes back, the igniter is being installed, the avionics is on, and we hurry back to mission control at the last minute.
The countdown initiates, and at T-0, nothing happens. A bad connection, apparently. The range manager goes back to the launch rail, strips off some wire at the end of the igniter, and reinstalls it into the firing bus.
A new countdown: At T-0, the call is heard: “Misfire”.
Misfire means that the igniter has gone off, but the fuel grain has failed to ignite. It is with heavy steps we return to the launchpad and run through the scrub checklist.
Since so many other teams have failed to launch, there is no chance for a launch window the day after. When we return, though, there is a glimmer of hope. Reinhard, one of the pyrotechnicians, says that he might be able to cook something up for us in the pyro-tent. Jacob Larsen, perhaps one of the most integral people on site, says there is a possibility we can piggyback on the Scottish teams launch window, given that their launch goes well.
We only have about one and a half hour to get the rocket taken apart, the batteries extracted and changed, the parachutes packed back together, get out to the launch rail and set up the rocket, and then get back again. It is a momentous task, but in a feat of teamwork I have never experienced before, we manage to get all done in time, except for getting out to the launch rail.
Luckily, the Scottish team is also somewhat slow. We are watching a beautiful launch by the Swiss team, which unfortunately hits the ground hard due to a main parachute system malfunction.
The yellow flag comes back up, and we run out to the launchpad and get the rocket up in record time. We come back to mission control to watch. When the countdown goes to zero, the rocket flies off the launch rail straight as an arrow into the heavens. The altitude callouts say 20 thousand, 25 thousand, 30 thousand feet. And, finally, 32 thousand feet. It is an amazing feeling, and a relieving sight when we see the drogue chute like a tiny dot in the sky. We lose telemetry at some point, only to get back video feed, but no telemetry, a few moments later.
It turns out the main chute has opened already at apogee. This means the rocket is in for a lengthy descent. It travels 25 kilometres downrange, and takes 30 minutes to reach the ground. It almost lands back at the paddock area where we have worked on the rocket for the last few days. We mount a recovery operation with a few of the team members who still have energy to go. And although we get close, the fire brigade of Ponte de Sor gets there before we do.
When we get the rocket back, it turns out only half of it has been recovered. The “smart” half, as it were, with all the electronics and data from the flight. The other half is nowhere to be found. While we ponder this, get some sleep, and process the last week’s efforts, we are greeted with a pleasant surprise! The rocket stetind, with its maximum velocity of 1.5 mach, and its final apogee of 9835 meters, has broken the EuRoC altitude record, the velocity record and the record for the flight closest to 9000 meters. Although the recovery was not perfect, on Saturday evening we win the 9000 meter EuRoC SOLID award. A worthy achievement for the Project Stetind!
One thing remains though. The aft is nowhere to be found. We scrutinize the flight data and video, and decide to get into contact with the firemen and search the landing site of the missing aft. It is nowhere to be found. This is where we go into analysis mode. The aft seems to have unscrewed itself during the descent. This appears to be for three reasons. Firstly, due to the early deployment of the main, without the main release mechanism actually activated, the swivel link is hidden inside the rocket, unable to perform its job. Secondly, the glue that was holding the eyebolt in place, seems to have been too weak to counteract the rotation of the aft. And thirdly, the aft just so happened to rotate in the out-direction for the eyebolt threads.
We find the point in the video where it most likely fell off, and use GPS data to reconstruct a flight path. Although all three flight computers malfunctioned for three different reasons during flight, we were able to simulate a likely apogee location downrange. Combining this with some Newtonian mechanics, we were able to estimate a drop location. Only four members have the energy required to search for the aft at this point. We have to go all the way to Lisbon to get a rental car, and then all the way back to the launch site. The chances of finding our aft seemed to shrink for every kilometre of stingy vegetation we drive past. We stop at the estimated drop site, and lo and behold, after a mere 45 minutes of searching, we find the aft sticking out of the ground like a flag, only the front end damaged. Remarkably intact even after a 9000meter fall. We are ecstatic and relieved, and after a lengthier visit to the Ponte de Sor shipping storehouse, we are able to pack the aft together with the rest of the rocket, to be shipped back to Norway. And with that action, the Project Stetind was officially over, short only of the awaiting celebration.