Meet Wednesday! The New CU PCB
The Common Unit, CU, controls data management, parachute deployment, and localization signals. The CU PCB stores linear acceleration, angular rate, pressure, magnetic field, and raw GPS data throughout the experiment. Upon detecting a rise in pressure to that expected at approximately 5 km altitude, the CU activates its thermal cutter. The thermal cutter burns the fishing line holding the CU lid to its bottom plate; consequently, the lid is released with the help of springs, and the parachute is released due to air drag. The CU then uses radio beacon and satellite modem to communicate its GPS location. These functions are vital to the recovery of the experiment's two Free-Falling Units, FFUs, as well as later data analysis.
One CU PCB, named Leia, was inherited from SCRAP, the previous REXUS team from KTH. The other one has been recently completed and named Wednesday by Laura. Wednesday has passed preliminary functionality tests that prove she can operate in the various modes required of her, manage data, and correctly identify her position.
Both CUs were then tested in vacuum. This was done with the help of SCRAP's very own Alexander Karlsson, who managed the CUs for that team! This test was meant to show that not only can the electronic components operate in vacuum conditions, but that the thermal cutter would be activated upon reaching the predetermined pressure. Leia passed this test with flying colors; unfortunately, Wednesday did not. Debugging is in progress to determine why the detection of the predetermined pressure did not lead to the activation of the thermal cutter.
Once debugging is completed, focus can be moved to the manufacturing of thermal cutters. Leia and Wednesday will then be tested in a thermal chamber to determine if the electronic components, especially the thermal cutter, can operate in various temperature conditions. The next step is to test the mechanics of the parachute deployment system to make sure that the activation of the thermal cutter leads to the release of the CU lid and the deployment of the parachute.
This test of the system as a whole is, in fact, being done this week by SPIDER, another project team from KTH using a similar CU design. They will toss the CUs from a helicopter and examine the functionality and effectiveness of the recovery system. Their test results will help determine any design changes or further testing required by our project.
Hopefully, we'll have some positive updates for you soon! And a special thanks to Alex for the expert consulting!
