Thursday, 2 August 2012


Over the last week we have been doing some of the less exciting things leading up to the first vehicle test.

I have been mainly programming the flight and ground software as well as some wiring. I learnt my lesson on the nitrous thruster project about having un-necessary complex software and ground electronics. For that project I wrote a python program that I used to control the test stand electronics. This in itself wasn't so bad but the program was not well written and thought out. The test stand software/communication proctorial also had random communication interruptions which the test stand software did not handle well. For first test I my  "fix" was to have the test stand micro controller reset itself every few seconds (which didn't affect operation) so if it froze it would fix itself.

This time around I decided to use lab-view for control. There is a certain cool factor in writing your own program from scratch to "remotely control your rocket" but there is no point in re-inventing the wheel and lab-view makes the graphical side much quicker and handles serial much better than a python program written by me.

For the flight software I had been giving some thought to using simulink to run the rocket but from a safety perspective I don't really feel comfortable letting a program I diffident write (interpreted from the simulink program) control the rocket so I will still be using Arduino.

Commands are sent to the rocket individually via a 5 character string over serial. I wanted to be able to command individual solenoids manually and also give the vehicle commands which it knew what to do with. For example "S2255" means set solenoid 2 to 255 and "S2000" means set solenoid 2 to 0.

At the moment the rocket will continuously send out Pressure and IMU data every 0.1 seconds which is displayed in the labview program. It also sends diagnostic strings when enabled which says what it is doing program wise.

This weekend I want to do some trial runs filling, pressurising, venting and testing out all the systems. I also want to pressurise to 800PSI to test the tank. I know the burst pressure should be around 950PSI but it is possible this tank could be weaker than the previous one we tested.

I ended up just buying a lighting truss to suspend the vehicle for tethered testing. It is 4m high and can support up to 60KG.  Sam started making a wooden truss but considering the lighting one was only going to be slightly more expensive I think it will work out better. Its also potable and comes with a carry bad which could come in handy. I was also worried about the wooden one burning.

The stainless tubing is a continual source of frustration but hopefully it will finished this weekend. If you can work with flexible hose I would highly recommend it over hard tube.

No comments:

Post a Comment