Hej everyone! Stefano here. Tired of being locked inside and want to get out? Let’s do it, be ready for ejection! Same as you, our experiment will need to get out of its own dark room, aka “the rocket”, and be free (falling) in space. How? Let’s see it.
Our Ejection Mechanism will basically kick the Free Falling Unit out of the rocket. The working principle is based on compression springs which will be loaded before launch and kept compressed by steel cables; but let’s see in more detail.
This metal “toaster” is our ejection system and it will be located inside the rocket. It will contain, protect the FFU until it’s deployment time.
Once the rocket reaches our desired altitude, it will be needed to open the door and eject our FFU. Since it’s complicated to open doors on rockets, we will simply eject that as well. Four small springs on the front side, each having a force of about 60 N, will push out the hatch, freeing the path for the FFU which will follow one second later: a big spring, able to deliver almost 100 N of force, will move a pusher plate which will drive our experiment out.
The front springs are powerful enough to give the hatch enough acceleration to not be an obstacle in the ejection of the FFU.
But if all these springs are compressed since before launch, how can everything stay in position and start moving only when desired? The answer is simple: steel wire cables. These constitute the retention system and there are two of them: one to retain the hatch and another for the FFU. The
first is shaped like a U and it goes around the ejection system while the second is positioned on the backplate of it. These 2mm cables will be pretensioned in order to avoid any kind of movement during the rough launch phase. We expect loads on them up to 1.5 kN but no worries, our tests showed they can withstand until almost 3 kN.
Three pyrocutters will be used to cut these cables when it’s time for ejection. The pyrocutters are small devices where an electrical signal will ignite a small controlled explosion which, in turn, will activate a blade directed towards the cable. They are contained in 3D printed plastic cases.
But where are we now?
At the moment we’re in the middle of the testing phase, the first tests on cables have been successfully conducted and we will start soon with ejection testing. Here a simplified version of what will happen during FFU ejection, just to give you a glimpse:
We expect an ejection velocity between 3 and 5 m/s but it doesn’t really matter, as long as the ejection is successful and the FFU doesn't get stuck hanging half out of the rocket.
That’s all from us this week, 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.