The first launches of SQUID: Spring and RID testing

Yesterday the rocket interface disc, RID, finally arrived. This is the piece that actually mounts the free-flying unit, FFU, to the rocket. The custom made wave spring that will eject the FFU arrived a couple of weeks ago, and now we could finally mate them together.

The rocket interface disc (RID) with the ejection spring

However it soon became apparent that the spring had a tighter fit in the spring gully than we had expected, and to determine whether this would affect the ejection or not me and Mikko carried out some spring testing.

Soon half of the team had gathered around to watch and help out as we covered a sturdy table down in the workshop with foam and devised a clever way of holding the bottom plate of the FFU down against the spring. An unlucky Mario was selected sit under the table and cut a rope going down through a hole in the bottom plate and rid, and down through the table where it was hooked up to a tightening mechanism. To document the ejection we borrowed a Casio high-speed camera from the department of mechanics.

We did two “launches” today, and while the launches weren’t as straight as they could have been the results seem positive, especially since the weighted-down bottom plate was not perfectly balanced. However, since the radius of the spring is slightly lower than expected the very top part of it easily gets jammed between the bottom plate of the FFU and the RID. More testing will be done soon, but until then enjoy the fancy high-speed videos! Sorry for not having turned them right way up, but this would decrease the video quality.

The flickering is due to the flourescent lighting in the room,  and the towel in the first video was an attempt at catching the falling plate. 🙂

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Parachute load test with an unexpected outcome

Last Thursday it was time to determine once and for all how much the parachutes we use in the landing system could handle. Having failed to break them in both the car towing test and the actual drop test, me and our supervisor Gunnar Tibert resorted to more brutal methods.

One of the 70″ parachutes was hung upside down from a hook in the Structures Lab at KTH, supported by a single line of paracord which was to brake the fall. This is the same type of cord that was successfully used in the drop tests above Esrange. The parachute was loaded with about 19 kg of extra load, and dropped with 1.5 m of slack paracord.

Sometimes it's best to use what you have closest at hand! 19 kg of old newspapers have just the right density to fill out the parachute nicely.

Much to our surprise, it turned out the paracord, which we thought was rated to the equivalent of a couple of hundred kilograms in force, was the weakest link:

View from the hook of the crane, filmed with the GoPro HD Hero.

420 FPS high speed footage shot using a Casio consumer camera. This doesn’t show the paracord breaking, but is cool nontheless!

Right now we’re trying to determine the speed right before and after the line broke so we can calculate the force in the cord. At any rate, it is likely we will switch this cord for the real system to be sure that the same won’t happen during our flight! However, the cord still needs to be flexible so the shock to the experiment isn’t too great.

SQUID on the official website of Sweden!

Recently Mario was interviewed for the education sub-site of the official website of Sweden, Sweden.se. The article is now online, check it out! 😀

Of course we agree, projects like SQUID are an excellent reason to study in Sweden (and at KTH, above all!). 😉

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.

The art of making streamers

Jacob writes

After two presentations at Bergtorpsskolan in TÀby and two more at Naturvetargymnasiet in SödertÀlje the school visit part of our outreach plan is done for the time being. All work is now focused on the tasks that need to be finished for the Critical Design Review in the beginning of June!

One such task is choosing the proper streamer for the landing system.

In order to minimize the risk of the parachute getting entangled with the free-flying-unit (the ejected part of the experiment), it needs to be pulled out and away from it. We hope to be able to do this with a simple streamer, which is kind of like a long ribbon of cloth or plastic.

Streamers are commonly used on model rockets in place of parachutes, but we haven’t found any good info on them being used for anything bigger. This means we have to do some testing! What we’re mostly interested in is how the drag from the streamers varies with speed, the weight of the material, and the dimensions of the streamer itself.

This weekend I have a great opportunity to test just this my holding them out on a stick from a car, but first I need something to test! During lunch today I headed to a hobby store which just happened to have some streamers for model rockets at hand… including some big 7*70 inch ones!

The model rocket streamers are very light while the info we’ve found on the subject says that a heavier streamer might provide a lot more drag. However, thanks to the LAPLander team we have a lot of thick, heat- and tear-proof airbag cloth lying around at the lab, so I immediately got to work cutting out more streamers of various dimensions from that.

It’s going to be fun sitting in the back seat of a convertable testing all these during the weekend, I’ll write up a post about how it went next week!

Oh, and here’s a pic from one of the presentations we held at Bergtorpsskolan. It’s been great fun and the students have been really interested, and haven’t been afraid of asking us tricky questions! Hopefully we can go out and do this again after summer.

David and a group of students at Bergtorpsskolan

Yuri’s Night in Stuttgart – Part 2

Today we took a bit of a break from the space-related work and took a trip into town, with our target set on the new Mercedes-Benz museum. It’s on the other side of town from Vaihingen where we’re staying, but the S-bahn took us there in just 20 minutes.

The museum was extremely impressive, both from the outside and inside. Three elevators carry visitors up to the top of the central concourse, and the trail then goes down in a spiral, starting with the humble beginnings of the first Daimler and Benz cars and ending with the latest luxurious supercars and a massive display of the legendary Silver Arrow race cars. I won’t say much more and let the images speak for themselves.

We stayed over three hours, there was just so much to see. Once we did get back to town we had some food (strange german sausage-pastries) and checked out some stores, before heading to the observatory. Most of the preparations for Yuri’s Night had already been done though, and we were treated a rather strange laser show in the planetarium, a mashup of mummies, dinosaurs, and astronauts.

Last but certainly not least we headed to the train station tower from which we could see much of central town, and then to a traditional german pub which served the most amazing dinner. We did not stay very late though, as we had a job to do the next day…

Delar till de sfĂ€riska sonderna / Parts for the spherical probes

We are sorry for the lack of updates the last week, but we’ve been busy investigating an alternative landing solution. We’ve come to the conclusion to use a parachute system instead of the previously mentioned airbags. It hasn’t all been hard work though, we got to visit an astronomy camp at Barnens Ö, where we held a presentation and fired off model rockets! More on that and the new landing system in a later update!

In the meantime, the parts we ordered for the spherical probes at the ends of the SCALE system booms have started to arrive. Here is a picture of one of the freshly made wire boom probes, and one of the circuit boards it will contain. They were both manufactured by external companies from plans made by us.

Hej alla bloggbesökare! Det var ett tag sedan vÄr sista uppdatering, eftersom vi har behövt lÀgga allt krut pÄ att hitta en ny landningslösning. Vi har nu bestÀmt oss för att anvÀnda en fallskÀrm istÀllet för de tidigare luftkuddarna, men detta berÀttar vi mer om i ett senare i inlÀgg. Roligast av allt var att vi fick Äka och hÄlla presentation och skicka upp modellraketer för en massa astronomiintresserade högstadieelever vid ett astronomilÀger pÄ barnens ö! SÄ fort vi har redigerat ihop den lÀgger vi upp en video frÄn uppskjutningarna!

Under tiden kommer hÀr lite bilder pÄ de alldeles nytillverkade sfÀriska sonderna som ska sitta lÀngst ut pÄ trÄdantennerna, och pÄ ett av de kretskort som de kommer innehÄlla. BÄda tillverkades frÄn vÄra ritningar av företag utanför KTH.

One of the SCALE probes, which will sit on the end of the wire booms and contain accelerometers, gyros, wire tension sensors, and the Uniprobe magnetic field sensor

A circuit board for the spherical probes at the end of the SCALE booms. There are seven boards in total in each one!