LOHAN turns up the heat on Vulture 2 motor

Couple of old laptop batteries, or a broken fondleslab or two. Enough capacity to get you into the stratosphere with the heaters on. No need for extra sensors, timers, or faith in the insulation. Job done.

Ideas in no order

1) Too late to mount the rocket in the truss I guess.

2) Fuel cell, for example: http://www.horizonfuelcell.com/portable_power_minipak.htm (temps might be an issue)

3) Solar? probably too large an area needed to give the current needed.

4) Wind -hmm non-starter

5) A just big-enough (LiPo? - http://www.overlander.co.uk/batteries-chargers/lipo-batteries/lipo-batteries-6100mah-4s-14-8v-30c-supersport.html) battery that can be set to turn on at a certain time or altitude?

all for now.

How much heat is in a nice cup of tea?

That'd be the proper boffin way to keep things warm.

drop 'em?

Would it be possible to use an external battery pack that could be dropped off on parachutes at set altitude to and allow the rest to continue unencumbered? You have the altimeter thingy all set up so it shouldn't be that difficult to add an extra triggered event.

Layer of insulation

Go for aerogel! Anything else would be disappointing.

tuppence

As an on board option, caps are pretty light and cheap. A set of 10F caps running through that Polyimide Thermofoil might keep LOHAN warm enough to light her fire. That said, I imagine it would be more of an insurance thing with the preheat on the ground and let the caps do what they can on the trip up.

Come on

Surely this isn't rocket science? ;)

Insulation is the key. There are some fantastic materials around these days. In a well insulated, small size environment 2 watts is a lot of heat!

Cheap and lightweight

I'd suggest that airborne heating might be best done with some of those air-activated hand warmer heater packs. They're light, and cheap. Sure, they're technically producing heat through a form of combustion (oxidization of iron filings IIRC), but there's no open flame, and you've already proven that the rocket motors are bloody hard to ignite with the correct gear, let alone by accident.

They're safe enough to be used near skin, so I wouldn't think overheating would be a problem. They do need oxygen though, so their effectiveness will decrease somewhat with altitude I suspect. Might be a good insurance policy...

Nice bit of kit

but I'd have gone for a suitable length of nichrome wire wound around the engine. Cheap, robust, no need for epoxy (inbetween the heater and the engine) reducing heat transfer to the engine body. You could even distribute the turns so that there are more around where the igniter sits

I have my doubts

I doubt you'd be able to insulate the motor casing enough (On all ends) to prevent it from cooling. The business end, the nozzle, is where it matters. And that is exactly the bit you can't insulate as good as the rest. And even the rest can probably not be insulated enough to keep it nice and toasty for 30 minutes in an environment well under freezing.

If you really want to save weight, do some quick calculations on the amount of energy needed to keep the motor warm all the way. (For which you need a thermal resistance value for the motor insulation) and for warming the motor up from cold prior to launch. I am guessing warming it up from cold in flight is going to be more efficient than trying to keep it warm all the way.

Then also decide if you NEED it to be at +20 degrees C or if you can get away with only -5 C for instance. The lower the temperature difference with the outside air, the smaller the heat loss through conduction.

KISS objection

Extra piece of equipment to stick to the glider? Dangling wires? Don't like it very much.

Surely simply using more flammable material for the igniter will sufficiently heat up the part of the fuel that needs to fire up. After that it will heat itself. No?

Or, attach the motor to the glider in such a way that until launch it can rest inside a cylinder that is attached to the truss, and heat the insides of this stationary cylinder. (But this, too, fails the KISS principle.)

Just a thought

You sure you need to epoxy the element to the engine? It seems a little permanent. Wouldn't TIM compound and duct tape work just as well, and be removable?

Plus, well, duct tape.

Not all insulators will work

With low pressure, insulation relying on trapped air is nearly useless. This rules out fibreglass, wool, polyurethane foam, and even aerogel. Since radiation is the only source of heat loss at altitude, you need radiant insulation. Layers of infrared reflective material separated by a small gap performs quite well on satellites. A cheap version can be made out of a space blanket and some cheap lace.

Of course, you'll probably need a bit of conventional insulation before it reaches altitude.