Falling with style
Hello everyone! Måns here with an update from our successful drop test last Saturday! :D
Last week we performed an important drop test in order to verify several different aspects of our FFU: ejection system, the parachute deployment with a boom dummy, GPS tracking, and telemetry along with on-board data acquisition.
Compared to previous REXUS experiments, instead of dropping the FFU from a helicopter up in Esrange, Kiruna (almost as north as you can get in Sweden), we tried a different approach by dropping it from a small propeller airplane at Sundbro Airfield, Uppsala. This was most certainly the cheaper and more flexible alternative and allowed us to perform the test within a week’s notice.
As per our experiment timeline, the FFU free falls through the atmosphere after performing all the essential measurements. Once it reaches 5 km of altitude, the pressure sensors will activate the thermal cutter which in turn will cut the kevlar thread that is retaining the lid. After the thread has been cut, a spring will push out the lid and the parachute will be pulled out by the aerodynamic turbulence.
To test the parachute deployment, we used a test FFU with the ejection system, a dummy boom attached to simulate the actual boom and some dead weight to get the final mass right. Our dedicated passenger Max accompanied by the experienced pilot Amar, took off in the plane from Sundbro Airfield. The drop, located about 10 min away from the airfield, is an enormous field that we had received permission from the farmer to perform the drop test on.
At the field, the rest of the Rexus team stood waiting at a safe distance from the actual drop site, to observe the drop and later go out and gather the test FFU We would also do a post impact analysis and then return it to Sundbro Airfield to prepare for another drop.
In the picture above, you can see how the drop site looked like. Before the first drop test of the test FFU, two foam dummies were dropped. This gave important feedback of the winds and allowed the pilot and Max to practice the drop.
During the first drop, Max accidentally started the parachute ejection timer inside the cockpit. Fortunately, he was able to salvage the situation by fast reflexes and manually holding down the recovery unit lid. However, this meant that the parachute instantaneously deployed after the drop and boom assembly got tangled. This provided important information on a potential situation that could happen if the boom is not fully extended and gets tangled in the parachute. Luckily, the parachute still functioned and the descent was controlled.
Unfortunately, on this drop we did not receive any GPS location and the on-board data acquisition was saved but seemed to not have been parched correctly.
On the second drop the pin was pulled as Max dropped the test FFU and the parachute deployed 4 seconds after. In the picture below you can see how the drop looked like the second time. This time the boom was fully extended upwards as the parachute deployed and de-accelerated the dummy boom which then got ripped off at the attachment point on the test FFU.
This time we received a GPS signal and the on-board data was successfully saved. In the picture below you can see how the test FFU landed securely on the ground and the two GPS antennas exposed.
Overall, the drop test was a huge success by providing important feedback about our FFU ejection system along with demonstrating a new drop test procedure that can be used again by future REXUS teams from KTH.
As for now many in the team will focus on their exams the following week. But stay tuned to hear more about our next adventures! Also, make sure to check out our website: www.b2d2.se for other exciting news from us and do not forget to follow our Facebook page and Instagram accounts.
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