This week we have been doing a bit of analysis of the Acceleron IIIb flights we captured on video. We noted a few things:
1. It looks as if the stage separation was taking place a little later than we would have liked. The booster was already slowing down when the release happened. This can be seen at the top of the flight path as the booster starts pitching over. Since the release sequence is initiated by the pressure switch, we will need to make the pressure switch activate at slightly higher pressure. We can adjust the tension on the spring of the TDD, or alternatively add slightly less water to that segment with the pressure switch. Less water means that the segment will stop producing thrust slightly sooner compared to the other two segments that are still accelerating the rocket.
2. We now have a better idea of the time it takes to get to apogee and hence can set the parachute deploy delay for the sustainer appropriately. The parachute deployed about 2.5 seconds after passing through apogee.
3. The parachute deploy delay for the booster will be shortened as even the minimum setting allowed by the software on the day wasn't quite enough.
4. After release the booster looks like it falls more like a back-gliding rocket. It actually saved us a whole lot of work after the first launch since the parachute deployed so late. This is actually a favourable feature because if the parachute fails the rocket should land at a lower rate than if it hit nose first.
We have also been continuing with the next iteration of the flight computer. We are trying to reduce its weight and foot print to make the whole deployment system smaller and lighter.
The new flight computer uses a more compact and lighter launch detect switch. It works in two dimensions allowing you to mount the PCB in different orientations. The deploy servo is directly mounted to the PCB and the battery is directly below the PCB giving a more compact design. The full details of the flight computer will be posted once it has been tested.