Weekly Report #21: Testing (Structure)

Wow, it has definitely been a long time since our last weekly report. If you follow our Facebook page however, you know we have been busy during the last six weeks. You may remember our experiment looking basically like this:

1Lots of nice drawings and renderings, but the only thing actually finished was the frame. Now though, we are here:

2Yes, SMARD is actually completed and ready for launch in March! During this and the next two weeks, we will describe the assembly and testing phase from each team’s perspective, starting today with structure.

At the time of our last weekly report, we had quite a long to do list:

–          Finish the solar panel (the solar cell mass dummies still had to be glued on)
–          Manufacture and integrate the electronics housing
–          Manufacture and integrate the GoPro camera housing
–          Integrate acceleration sensors and lighting LEDs

We did encounter our fair share of problems with workshop availability and delivery delays, but by the end of November everything was finally done, just in time for the thermal vacuum test at the Institute for Space Technology (LRT) at our university.

Below, you can see the experiment being put into the vacuum chamber. The many cables are connected to temperature sensors. I am sure the electronics team will tell you a lot about them, but we were mainly interested in one thing: After being cooled down to -25 °C, would the mechanism still activate quickly enough?

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During testing ten seconds of heating time had not been enough to get the SMA spring to contract even from room temperature on several occasions. In the cold vacuum however, the mechanism actually deployed after only three seconds! We were obviously very happy with this result.

The final structural test was yet to come, however: the dreaded shaker table. During the integration week in Bremen at the ZARM facilities, the entire experiment was subjected to the same vibration loads it will encounter during launch on the REXUS rocket. You may remember that weekly report where we wrote about our analysis and calculations and stuff? Well now it was time to see how they would hold up to reality. Below you can see the shaker table on the top and the experiment with additional acceleration sensors mounted on the bottom picture:

4l 4rNo one from the structures team had come along to Bremen, so we were all sitting in Munich biting our nails while reading status updates on our phones. The test was postponed several times, but in the end we got the message: No structural damages, mechanism deployed successfully. One cable had actually detached, but this will be an easy fix. Our structural design is validated and ready for flight!

Now, we won’t just sit around doing nothing until March. The structures team will continue work on the HDRM, improving electrical contacts and optimizing activation time. We will keep you updated on further developments. For now though, the SMARD structures team is signing off for some well deserved holidays. See you in 2015!