Congratulations to all experiments on REXUS 14 for a successful flight. The launch of REXUS 13, which MUSCAT is on, is preliminary scheduled till Wednesday morning. We are all waiting with excitement.
The RMU electronics is really starting to take form. There is not much left to solder now. What you can see on the picture is a FPGA at the top-left corner. It will handle all the communication between the ground station an the FFUs while the FFUs are mounted inside the rocket. You can also see seven coils distributed over the board. Two of them are for filtering the 28 V power that is supplied to the MUSCAT experiment. The rest of the coils belongs to step down converters. Four of those are 4.2 V and will be used to charge each FFU while mounted inside the rocket. The fifth is a 5 V regulator that together with a few linear regulators will power the FPGA, sensors and the camera control circuits.
The the work of the RMU electronics can be divided into several steps:
- Conceptual design
- Electrical schematics
- PCB layout
- Verification of hardware
- Firmware implementation
We are currently at step 3. PCB layout means that we are creating a drawing of were every component will be placed and how all the connections will be routed.
The RMU electronics is quite similar to the FFUs. As you can see in the conceptual diagram below, the backbone is a FPGA and it features sensors. The main task for the RMU electronics is to split the communication from our data connection into the experiment out to the four FFUs. This is handled inside the FPGA. The RMU electronics will also be able to control a camera that will be mounted inside the RMU.
An early morning the 29th of August, me, Leo, Andreas and Miguel left KTH. Our destination was Stockholm Skydiving Club located in Gryttjom outside a small town called Tierp.
To test that everything would work, a complete test was made inside the airplane. Leo held both Free falling units (FFUs) in his hands and observed that the parachute deployment was initiated at the right altitude. Everything went smooth. At an altitude of 900 meters the pressure threshold was reached and the parachute deployed.
With this test done we had great confidence in the system. So we sent up our beloved FFU called OJ with the experienced skydiver Stefan. Stefan dropped OJ, hanging from his parachute, at 1800 meters over the ground. Stefan quickly lost track of OJ. From the ground we desperately stared at the sky to spot the parachute deployment of OJ. Since Stefan with his big parachute was only as a small dot from the ground, this was a harder task than imagined. The seconds passed and no sight of OJ. Minutes passed, ten minutes passed. We gave our trust to the built in localization system. It was supposed to send its GPS coordinates through an on board satellite modem. But no messages were received. Later we searched the fields with a Para-motor, but no luck. I’m not going to prolong this any further, the sad fact is that we still haven’t found OJ and we have no idea what went wrong.
If we were to give up at this point, we would go home with nothing new, even less than we came with. So after some heavy discussions we made the decision to send up our other FFU called Glad. This time we reduced the drop height to increase the chance of spotting it from the ground. And yes we did! Glad collected data as planned during the free fall. After a perfect parachute deployment it sent its GPS coordinates and GLAD could be recovered a few hundred meters away. The data is yet not fully analyzed, but it looks promising.
I have finnaly connected to internet. During the offlinetime I have maneged to travel to the hotel in Stainebach, get some sleep, eaten, breakfast and reached DLR.
Now I’m halfway through the soldering course at lunch brake.
To be continued…