04/25/2023
Recovery Reliability highlights from the NASA Student Launch 2023.
Recovery reliability can be a “hard row to hoe”. One of the hardest is entanglement of the “laundry” (chutes and harness). The tail section can fall into the main chute. Unfortunately, that failure mode occurred at least twice at NSL. In all cases the tail section was falling above the nose containing the main chute during descent under drogue. Ideally the tail and nose sections would fall flat spinning about the drogue and/or the tail section would fall beneath the nose. Problem is the tail section has to be heavy enough to overcome the drag created by the fins, otherwise the nose, being streamlined, wants to fall ahead.
https://youtu.be/HLuCndLABTY?t=5716
https://youtu.be/HLuCndLABTY?t=25642
So, what to do?
First, a longer harness is almost always better because it generally locates the tail and nose sections farther apart.
Second, locate the drogue closer to the nose containing the main.
This can result in a flatter descent orientation. Even if the tail section still has a tendency to fall above the drogue, it won’t be for long after the main starts to deploy. Note, in the video segments linked above that was NOT done.
Third, use a drogue that creates more drag than the tail section, so that the tail section has the tendency to hang beneath the drogue and above the nose. Of course, that means the drogue might be larger than desired for a targeted descent rate or downwind recovery, but the drogue’s primary purpose is to facilitate a controlled descent. If it fails to control the tail section’s position in a way that it can fall into the main, then it is not fulfilling its purpose.
Vanderbilt does an excellent job, despite having extra fins on their tail section. Note, where the drogue is connected and that the tail section falls well below the nose containing the main throughout the descent.
https://youtu.be/HLuCndLABTY?t=21610
