2: Rocket motor testing in the Rocketry Experimental High Altitude Barosimulator (REHAB) chamber
It's fair to say that the small matter of how to get a solid rocket motor to fire at altitude has been a right palaver. It's taken months to go from an initial concept of a shed-built hypobaric test chamber to the full-fat REHAB rig:
The bits and pieces are:
- Perspex lid
- Igniter cable
- REHAB chamber
- Vacuum pump
- Pressure gauge
- Digital thermometer
- Evacuation tube
- Thermocouple cable
- Safety tether tied to SPB standard brick
- Vacuum filter
- Insulated box
- Silicone seal
The only novelty here is the vacuum filter, which we've added to the system to allow us to see if the firing of reader Rob Eastwood's custom igniter is causing a significant pressure rise in the chamber prior to motor ignition.
The filter will intercept any smoke particles and other gunk from the igniter before it gets to the vacuum gauge - an expensive piece of kit kindly supplied by Applied Vacuum Engineering.
This means we can test for igniter-induced pressure rise without shutting off the isolation valve between chamber and gauge.
We'll give that a go next week. In the meantime, we do know that we can persuade a Cesaroni rocket motor to fire at around 20mbar - equivalent to 76,500ft (23,300m):
We've got more REHAB tests planned just as soon as a new batch of motor reloads turns up, so there's further low-pressure tomfoolery on the horizon.
Next page: 3: Rocket motor heater
James Van Allen had similar issues
I was only reading recently that when James Van Allen(he who the radiation belts are named after) had similar problems getting his test "rockoon" to fire at altitude due to extreme cold he solved the problem by heating cans of orange juice, attaching it to the firing mechanism and then wrapping the whole lot in insulation.
Of course those mechanism's were clock work and we have progressed a long way since then. For instance we now have pot noodles
I guess it will provide some resistance to rotation as the side of it would have to push against air to rotate.. Perhaps it will work, just for different reasons!
You are fitting a tail to orientate the truss in the wind?
If the truss is floating from a balloon then it would be travelling at the same speed as the wind and so cannot work. Or am I not thinking this through properly?