Landing & Recovery Systems

As the scientific data collected during flight is stored into an on-board memory the survival of the FFU is vital to the mission. Therefore a landing and recovery system has been incorporated. 

SQUID's landing system consists mainly of three parts: a cross form parachute, a streamer and the top plate ejection system. The solution has been developed in-house due to design constraints and requirements making rendering standard solutions useless.

The system is triggered by an altimeter that is preset to recognize when it has reached a pressure altitude corresponding to approximately 5,5 km during the descent back to earth. At this altitude a thermal cutter is triggered inside the eBox which cuts a Spectra cord, this will release the top plate which is then ejected from the FFU by two preloaded springs.

Directly underneath the top plate a streamer is resting and beneath that the parachute is packed into the compartments between the SCALE systems. The streamer is connected to the parachute via a Kevlar Shock Cord and has been folded in such a way that allows it to immediately catch the air stream and deploy as soon as the top plate has separated. Following this event as soon as the streamer has been deployed and the rope connecting it to the parachute is stretched it will exert a drag force that will pull the parachute out from it's compartments in order to deploy. During descent and after landing the FFU is located using the recovery system.

Three very specific tests were conducted in order to test and validate the
system, two towing tests involving parachute deployment behind a car and
finally a drop test from an aircraft.
First step in testing the system was to prove the concept of using a streamer
to deploy the parachute and at the same time test different folding techniques
in order to identify the one most promising solution. Tests were first conducted
on May 24 2010 (see the Streamer testing report under Appendix E –
Experiment Reports). These proved that the principle of using a streamer to
pull out a parachute worked as can be seen in Figure 34. A promising folding
technique was also identified and adopted as the primary one for upcoming
tests. However when the FFU was put into unfavourable positions such as
with the opening facing straight up and the parachute deploying horizontally
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no deployment could be achieved. Therefore the system could not be
concluded to be able to work in the conditions possible during descent from
this test nor be ready for drop test.
A new test run was planned and conducted on June 3 2010 addressing this
problem. The results from this test shows that along with some smaller
modifications made to the FFU (see – ) deployment can now be reached with
the FFU facing straight up. The system could at this point be concluded ready
for drop test conditions as parachute deployment seemed reliable. More info
about this can be found in the – .
The drop test was conducted at Esrange in Kiruna on August 24. Two DTFFU’s
(Drop Test FFU), with an in principal identical setup of the landing
system as the real one, some electronics for activation and a mockup
structure, were manually activated and thrown out of an aircraft at 1000m
altitude. Both of the DT-FFU drops were successful and parachute
deployment was confirmed in both cases. The units were recovered and
inspected. Both had survived the test completely. The conclusion of this test
was that the system had been validated and was ready for flight. For more
information on the drop test campaign see the SQUID Drop-test Campaign
Report under Appendix H – Experiment test reports.
Following the drop test the cord’s used in the system and the parachute’s
yield strength was investigated in order to ascertain that the system will
withstand the shock during deployment. During the first test conducted the
weakest point in the system was found to be the single cord connecting the
FFU cords to the parachute. The safety margin of the Paracord 550 had to be
investigated because it was a critical single point of failure. Due to lack of
acceleration data the shock force from the drop test had to be calculated
using very simplified methods that yielded very uncertain and questionable
results (see Strength safety factor of paracord during parachute opening
under Appendix H – Experiment test reports). The numbers available however
tended towards the safety margin being way too low and therefore a HMA
cord with 1000 lbs yield strength was chosen as replacement.

Three very specific tests were conducted in order to test and validate the system, two towing tests involving parachute deployment behind a car and finally a drop test from an aircraft. As these were concluded successfully the system was ready for the real rocket launch at which the system performed flawlessly and brought the FFU completely unharmed back to earth.