LOHAN starts to feel the barometric pressure [printer-friendly] • The Register

Original URL: http://www.theregister.co.uk/2012/05/17/lohan_motor_trigger/

LOHAN starts to feel the barometric pressure

Mulls spaceplane rocket motor trigger

Posted in SPB, 17th May 2012 09:03 GMT

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As the design of our Low Orbit Helium Assisted Navigator (LOHAN [1]) Vulture 2 spaceplane continues apace [2], we've been considering just how to fire the aircraft's solid rocket motor at a predetermined altitude.

[3]We haven't yet revealed exactly which mighty unit will eventually power the Vulture 2 heavenwards, and still have to determine whether off-the-shelf solid rocket motors will actually fire at low pressure and temperature.

That's what our forthcoming Rocketry Experimental High Altitude Barosimulator (REHAB [4]) experiment is designed to do, although we're still waiting for a few last bits for our shed-built hypobaric chamber.

If the rocket motors won't fire under simulated high-altitude conditions in an out-of-the-box state, we'll obviously have to find a way to make sure they will ignite when the big day comes.

So, assuming we've got our powerplant to go bang at altitude and -60°C, how are we going to trigger it when LOHAN launches for real?

Well, our instinct is to go for a pressure-operated electronic trigger board, like AED's Rocket Data-Acquisition System [5] (R-DAS). This piece of rocketry kit could be programmed to fire up the 12V igniter system at a predetermined altitude, based on the barometric pressure.

There is a slight problem, though. The R-DAS has a Motorola MPXS4100 pressure sensor, which is only good down to 20kPa, which by our reckoning represents an altitude of around 12,500 metres, or 41,000 feet.

We need a sensor that will go down to 1 kPa, so we threw AED an email asking if the R-DAS could be fitted with an alternative Motorola sensor covering the required range.

We're still waiting for a reply, and while we're twiddling our thumbs, we thought we'd invite our LOHAN reader experts to give us their opinion, or perhaps suggest an alternative line of attack.

Over to you...®

Further LOHAN resources:

New to LOHAN? Try this mission summary [6] for enlightenment.
You can find full LOHAN coverage right here [7].
Join the expert LOHAN debate down at Reg forums [8].
All the LOHAN and Paper Aircraft Released Into Space (PARIS) vids live on YouTube [9].
For our SPB photo archive, proceed directly to Flickr [10].
We sometimes indulge in light consensual tweeting, as you can see here [11].

A tip of the hat to our LOHAN associates

LOHAN starts to feel the barometric pressure

Further LOHAN resources:

Links