This week, one of the most important and crucial subsystems is being highlighted: recovery.

The rockets designed by the EPFL Rocket Team are intended to be launched and recovered several times. In this way, we can properly test all subsystems or parts of subsystems that compose them for competition.

The competition’s scale, the Spaceport America Cup, gives a good number of points to the decent and recovery of the vehicle part. Thus a controlled decent and a recovery of the vehicle in good condition gives a maximum of points.

Moreover, for obvious safety reasons, allowing the rocket to fall freely is simply not an option. Recovery therefore has the crucial task of bringing it down in a controlled and safe manner to the ground.

To ensure this mission, the recovery team has developed an innovative parachute system. Indeed, the competition requires 2 different events during the descent: the deployment of a “drogue” (small parachute) at the peak to ensure a fast but controlled descent to avoid that the rocket has time to leave far from its launch point with the high winds. Then when approaching the ground, the opening of the main parachute which will guarantee a smooth landing. The particularity of our system is that it performs these two tasks with one and the same parachute thanks to a “reefing” mechanism.

How does recovery work ?

Now that we have seen the main objectives and operating principle of recovery, it is time to study in more depth how all this is done.

The first step is the detection of the apogee by the ravens, small specialized avionics. A signal is then sent to trigger the drilling of CO2 capsules in the rocket. This will generate a high overpressure in the recovery bay tube and thus cause the nose cone to eject.

The parachute, connected on the one hand to the body of the rocket and on the other hand to the nose cone by “shock cords”, will then be taken out of its bag and inflated. It is then in a “reefed” state, i. e. it is contained and does not expose its entire surface to air friction. Most of the descent takes place in this state until the arrival of the second event when an electrical signal is sent from the body of the rocket to the igniters located at the base of the parachute. These igniters will then cut the line that previously restricted the parachute so that it can deploy its full wingspan and ensure a smooth landing on the cow’s floor.

Future improvements:

– Improve dereefing method

– Make a new parachute

– Make the system more reliable

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