Original URL: http://www.theregister.co.uk/2011/09/12/lohan_motor/
LOHAN eyes hardcore partner's impressive girth
Vulture 2 spaceplane needs thrust you can trust
The dust has settled on our recent trip to International Rocket Week (IRW) and the dramatic launch of the Negligible Altitude Obstreperous Model Initiative (NAOMI) rocket, so it's time to reveal just what the assembled experts thought would be the best power plant for the Vulture 2 spaceplane.
Our primary considerations for the aircraft's power plant are minimum weight, simplicity and ease of operation. We know a lot of you favour experimental options, either hybrid or liquid fuelled, but our experience at IRW demonstrated that when it comes to a risky high-altitude launch, less is most certainly more.
The experts agreed with our initial analysis, and suggested we should select a single off-the-shelf solid fuel motor, and design the Vulture 2 around that. The idea of using multiple units was quickly binned because the consequences of one not firing are too hideous to contemplate.
The first and most obvious possibility that presented itself was the AeroTech RC 32/60-100NS - a 32mm-diameter motor specifically designed for rocket-powered gliders. Its most potent reload is a G-class insert (the G12-RCT) providing a long, steady-ish burn (see graph) which is ideal for propelling our spaceplane without tearing the bleedin' wings off.
Obviously, there are a couple of further considerations: how to make absolutely sure the motor will fire; and how will the motor perform at altitude and -60°C?
Our rocketry chums reckon a failsafe electronic trigger system is in order, with an independent back-up circuit powering a back-up igniter in case of primary ignition failure.
That makes perfect sense, but it's not a lot of use setting the thing off if it can't deliver under extreme conditions. We got in touch with AeroTech to see what they thought, and president Gary Rosenfield was kind enough to reply: "The overall motor performance will be higher, but the burn rate will be lower at the environmental conditions you quoted. Without testing, I do not know if the motor will ignite reliably at that altitude without a burst plug or other means to retain internal pressure."
Well, we like the first bit of Gary's analysis, but his concern about possible implications of lack of pressure are a bit of a worry.
Unfortunately, rocket motors aren't something they allow you to fire up in a hypobaric chamber, so we'll have to put our thinking caps on and mull this one a bit further.
To get things moving while we ponder, we've ordered an AeroTech RC 32/60-100NS to see how it measures up on the ground. Naturally, this will certainly involve a static firing test and perhaps a quick flight attached to something cheap and expendable. This is before we even consider inserting it into the Vulture 2, which will be neither of those two scenarios.
Your thoughts and suggestions are, as ever, most welcome. ®