Drop Test at Esrange – David’s Story

So Me (David) and Mikko arrived at Esrange on sunday the  22:nd of August feeling quite prepared but at the same time knowing there were still a few issues to be solved. We began working on preparing the DT-FFU’s first thing after brekfast on monday morning in what is called the “Cathedral” next to the balloon pad. After lunch Gustav arrived and joined the team. The weather outside was unstable with low clouds and during the morning it had been raining. So the verdict from Olle was to cancel flight and drop on monday and instead focus on planning and fixing everything thoroughly and do an early bird on tuesday morning.

The drop test team was supposed to concist of Me, Olle, Mikko and Gustav and the test itself was supposed to be a relatively small operation, or at least that was the picture we of the SQUID team had. But before we knew it this had in fact turned out to be quite a large opearation with the risk analysis having to go through the Esrange safety board, two more people joining us (Mark and Tomas from Esrange), mission overview and briefing etc, people in the operations central both in the Esrange main building and at the balloon pad.

During the afternoon we had the first mission meeting where we went through the drop procedure, checked from which direction the aircraft would fly in over the balloon pad, commands that were gonna be used, where people were supposed to be posted and so on. After the mission overview meeting everything finally started to feel very serious and real, and cool of course, this was the moment I started to feel a bit anxious.

Afterwards the team continued preparing the Drop-Test FFU’s for being thrown out from the airplane. We encountered a problem with cutter times not being consistent but pinpointed the problem to a manufacturing error. Fortunately we had one spare cutter which made two of the cutter units working as expected. Finally having this problem solved we proceeded to packing the parachute for the final time. When placing the top plate, closing and locking the FFU you could not help but feel even more anxious as this could be the last time we actually saw these models and the thought “hope we did everything correctly” was ringin through my head the rest of the night.

But anyhow finally the two units were ready and we proceeded to go to sleep. Falling asleep was not that hard as we were extremely worn out but I could not help going through the test procedure in my head as I was the one who was going to sit in the aircraft behind Olle and throw out the FFU’s. The anxiety was starting to take over completely but could not, fortunately, overwhelm the tiredness, so I fell asleep.

Next morning the first thing the team did was to run up to the “Cathedral” and check that the FFU’s were ok, which they were. The sky was clear and the sun was shining, weather looked perfect and we knew that today will be the day. Proceeding to have a nice breakfast which afterwards immediately was followed by the final mission breifing made the nervousness start to come back and tension started to build up a bit. Going through the mission everything seemed clear and ok for drop test. So me and Olle packed the FFU’s and headed to the amphibious aircraft which was stationed about 1 hour ride away from Esrange, while the ground crew did their preparations and got into positions.

Finally at the aircraft me and Olle practiced the drop procedure with a dummy (cookie jar) about five times before both of us felt confident with the commands and procedures.  Afterwards we loaded the units and took of heading for Esrange.

Well over Esrange we established contact with ground operations, checking we had the go for commencing the test. Upon reciving clearance from operations we turned in on a base leg for the balloon pad and the door was opened. The wind was really strong and it became really cold inside the aircraft. Finally turning in towards the final for the first practice drop with a dummy Olle called out “One minute” which meant one minute to drop and I switched on the imaginary power switch to the FFU (cookie jar in this case) and screamed confirmed, meaning the unit was activated and ready. Shortly after that Olle called “activate” whereafter i pushed the imaginary cutter start button and started the count to drop 1 2 3 4 5 6 7 8 9 10 then I threw it. Now I had felt how it was to actually throw something out of an aircraft and must say its not as easy as it sounds, the wind is blowing really hard which makes things hard and also it was very cold.

So now we proceeded with the first sharp drop after recieving clearance from operations. The same procedure as above took place but now with the real DT-FFU unit A. When switching on power i got confimation of system ok by the LED light installed. Then the signal cam to activate and the button was pushed and i started counting. Positioning myself into the practice drop position while counting the LED flashes up to ten the DROP. The FFU was deployed and fell, immediately Olle turned the aircraft and we got very good visual on the falling unit. Waiting waiting, hoping to see the red parachute and finally I saw it. The parachute deployed perfectly and the unit was slowly descending beautifully down to earth. Wohoooo! Confirmation came from ground that they had visual on the parachute and tracked it.  Second drop could commence with DT-FFU B which was equipped with a camera.

So same procedure again, power activation, status ok, cold air blowing and finally “Activate”. The unit fell and once again we turned around and tracked it. Falling, falling but no parachute. By this time it had fallen much longer than the A unit and both me and Olle was sure that this one would impact and be completely destroyed when suddenly we saw the red parachute deploying. Not long afterwards the unit touched ground and we laughed inside the aircraft at those margins. Calling on radio and concluding the test it was time to have some fun so we turned the aircraft around and came in low above the ground team for a victory flyby which was awesome 😀 then we left Esrange and returned to where we had started.

I felt great and on my way back I was also given controls of the aircraft 😀 Could simply not wait to see the videos and pictures of the test 😀

Preparing for drop test

Today has been a hectic day. I, Gustav, arrived at lunch and immediately joined David and Mikko in the preparations for the drop test which had been moved to tuesday due to bad weather today. There where some smaller errors in the test FFU´s however we’ve now compensated for those and are ready for the test tomorrow. Since it’s a bit to late for a longer update today I promise that we’ll maker a longer follow up later on with more details around the preparations as well as the outcome of the test. But for now wish us good luck for tomorrows tests.

The importance of documentation

In technical projects it is always important with documentation. Many people are involved and the only way to know what’s really going on is to make sure everything is down in writing. This is especially true in the aerospace industry, where the technical systems are very complex and the machines may never be reachable for an inspection. One of the best examples of this is the development of the Airbus A380; all the documentation produced during development, if printed out, would weigh more than the plane itself!
In a REXUS project like SQUID, we mainly deal with three kinds of documentation; Meeting minutes, checklists during the launch campaign, and finally the Student Experiment Documentation, SED.
The SED is a document which describes the whole experiment and the team and organizations involved in it. It details the hardware, the software, the team, the planning behind the project, the procedure at launch,the outreach/PR activities and all the tests and processes during the development. The document is updated constantly, and new major revisions are produced and sent in to the REXUS/BEXUS group at ESA 5 times during the project. Our latest version can be found just a couple of posts down!
Version 1 is sent in for the Preliminary Design Review (PDR) in January. It details the preliminary design of the experiment, and states the objectives and requirements that are to be met.
Version 2 is prepared for the Critical Design Review (CDR) in June. The requirements and objectives are already fixed, and focus is on producing a detailed design of the experiment for manufacturing.
Version 3 is written for the Integration Progress Review (IPR), which usually occurs 6 weeks after the CDR. Focus is on addressing the issues raised during the CDR, and adding more information in preparation for the launch campaign. This is the step SQUID is currently at. The document, with all report appendices and schematics, already weighs in at over 350 pages!
Version 4 is submitted a couple of weeks before the launch campaign when the experiment is shipped off, following the Experiment Acceptance Review.
Finally, version 5 is sent in 3 months after the finished launch campaign. Here the results and any lessons learned are documented.
But how does a team of almost ten people manage to work together on a single document?
Well, we’ve gone through a couple of different methods.
Google Docs: We started off using this web word processor, which had some advantages; No program installation was needed, everyone was always in sync, a few people could work on the same document simultaneously, and commenting could be done in real-time. However, the hassle of having to copy paste and reformat all the text into the SED template Word document was way too much for each new revision, taking several hours even when the document was much shorter than it is now. It also requires a working internet connection, and this was not always the case, especially when team members were travelling.

LaTex: This is quite a different way of writing documents, more akin to programming than traditional word processing. It’s easy to use templates and numbering of figures, elements and references is automatic. It’s also easy to merge changed documents together when collaborating. The generated documents also look very good. However, we never got around to adding all the formatting code and such to our previous versions.
Word & Dropbox: We ended up using the merge feature of Microsoft Word, combined with sharing folders in Dropbox. That way the individual word documents are always up to date. It’s not as easy to comment anymore, but this isn’t as important now that everyone has a pretty good idea of their respective areas. However, as Mario can testify, merging is far from flawless!
So, if you want to know everything that’s worth knowing about SQUID, just have a look in the SED.

Top plate ejection test 1

SQUID special forces test team has news for you all out there!!

After some hectic days of manufacturing parts for the landing system we finally have the target in sight. Attached to this status update is a video where you can find all the attempts performed tonight. Everyone has been working like being in a military bootcamp and the results are finally showing. Our top plate ejection system test can be considered a huge step forward for SQUID as the tests have proven that the design we’ve derived is in fact working in the test setup used.

Next mission is to once again infiltrate the workshop and continue to push through in manufacturing all parts needed for the drop test. Lots of tests and late nights are awaiting us but we will push through to the final end and see to it that we finish our mission successfully.

Ok some serious comments then. The test consisted of activating the cutter through the electronics and switches that are intended in the drop test model. As the cutter is activated the dyneema rope holding the top plate down will melt thus ejecting the plate. The first test was conducted with a weaker spring and was in fact a successfull ejection. However we could not stand to not have a successfull ejection with the stronger springs so sturdy as we are we found a way to compress and secure them. The difference can clearly be seen in the video and we all know that if something can fly higher then of course it also should 😀

StudentExperimentDocumentation v.3 finished

So right now we’re in the middle of preparing our selves for the drop test which is to be taking place next week in Kriuna. In the mean time please check out our documentation which where finished last night. The SED, as it is called, covers the whole experiment including background, planning, design, tests and more. So if you’re interested in how our experient works, please check it out!


PCBs soldered!

Written by Monica

So after have received the PCBs, the exciting tas of soldering started…we have 11 PCBs to solder…but for now 3 of them are critical to test and specially to be tested during a helicopter drop test that is coming in the next weeks.

It is worth to let you know that the challenge in this soldering is to handle the components..becuase they are so tiny that any false movement and they will fly and never see them again, specially the resistors and capacitors.. the ones we were used are case 0603 (1.6 mm × 0.8 mm)..

Other component part of the challenge was the FPGA becuase it has 100 pins and of course they must be clean and dont touch the next pin…when you see then by bare eye it looks so good but if you look with a microscope you will be surprised so it is very important to handle with care this component…. in the next picture some components

In the next part I will show you the PCBs as I showed some posts ago …and how they look now.


Beacon transmitter

It´s now time for me to give you a short summary of the work that has been done concerning the Radio beacon. But I’d first like to give you a motivation of why the beacon is so important for those of you who need a short reminder off the construction of our experiment please take a short look at Så vad är det vi ska göra egentligen? / So what’s all this about then? (please note though that we’ve changed from airbags to parachute for the landing system).

Since all the data that will be recorded after the FFU has separated from the RMU will be stored onboard of the FFU it’s a primary objective to be able to find the FFU after it has landed. To track the FFU two different systems has been integrated into the FFU. The first system is a GPS which receives the current coordinates of the FFU while in flight. The coordinates are then transmitted through a satellite modem and are then received through a web interface. The second system is the beacon transmitter. A beacon transmitter is a consists of a simple radio transmitter who transmits a signal in an devoted frequency. This signal can then be tracked by a simple receiver. The tracker/receiver consists of a simple radio receiver working at the same frequency as the transmitter  and a simple analog meter displaying the strength of the received signal. By pointing the receiver antenna at different directions is simply its possible to track in what direction the transmitter is located.

In practice the system used by SQUID consists of the TX1 transmitter from Radiometrix. The transmitter makes use of a simple quarter wave whip antenna (which in reality consists of a stripped coaxial cable). For the experiment the beacon will be sitting within the eBox while the antenna is attached to one of the parachute ropes. The transmission is done over 169.4125 MHz and is then received by the receiver.

TX1 transmitter

To test the transmitter function a NRX1 receiver, from the same company making the transmitter, has been bought. This transmitter will be integrated into a simple circuit. The idea is to make use of the Received Signal Strength Indicator (RSSI) which is provided by the receiver. The RSSI works by providing a voltage on one of the legs of the receiver which varies depending on the strength of the received signal.  The circuit will consist of battery holder, power switch, the receiver, analogue current meter and a receiver antenna. The analogue current meter will be connected to the RSSI pin and will vary by the signal strength of the voltage provided by this pin.

NRX1 receiver

The testing will start during next week and will be rounded of by the drop test. During next week a simple transmitter circuit will be built including the transmitter, a power switch, antenna and battery. The testing will start of by placing the transmitter in the Lilian wood nearby KTH, the receiver will then be used to try to find the transmitter. I hope to have some more info about the progress of these tests shared to you all during next week.

Towing Test extended story

On June 3 the SQUID team set out once more towards Tierp airfield in order to conduct the second towing test. The main goal of this test was to prove that the parachute can be deployed no matter how the FFU top is oriented. In order to improve on the design since Towing Test 1 some modifications had been done to the system out of which some proved to be very effective while some a little more vague.

Towing test 2 started off with 2 test runs to determine whether the regular streamer, used during Towing Test 1, or a new modified one with a pocket at the end provided more drag. It could be determined from these two runs that the modified one provided about 10N more at about 30m/s. Therefore this modified streamer was used for all deployment tests.

Afterwards followed the main test runs and the team was extremely efficient and we dispatched the FFU:s with an average time of about 30 minutes including all the times for the modifications and everything inbetween the runs.

The main issue from Towing Test 1 was that deployment could not be achieved when the FFU was mounted facing straight up on the rig. The results from that time where thus not sufficient to conclude that deployment should be reachable under the conditions we will face during descent.

However starting the test runs with the FFU facing straight up deployment failed on the 1:st run in this configuration. This was determined due to the parachute getting snagged by one of the hinges holding the top cover. The complete hinge and spring mechanism was afterwards removed and replaced with the old mechanical and manual half cookie jar used during the first towing test. The 5 following test runs with the FFU facing straight up were a success with deployment achieved during all of these. However during two the ropes broke after the parachute inflated. The last run even proved that the parachute could be deployed at 80km/h instead of 110km/h.

These results mean that our parachute should be able to deploy during the re-entry conditions. The next step will be the largest one this far in the landing system development and also the most critical namely the Drop Test. On August 23 three SQUID members will be present at Esrange conducting these tests, myself being the main responsible for the landing system being of course one of them. So now awaits a really hard road in order to prepare thoroughly for this critical test.

We have come a long way but now its getting really serious, the fighting gloves are on and the bell has sounded.