The case for air launch

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iain-3@truecircuits.com - 18 Jun 2005 00:34 GMT

http://mae.ucdavis.edu/faculty/sarigul/aiaa2001-4619.pdf

I got this link off http://www.hobbyspace.com/Links/RLVNews.html

Overall, I thought this was a great presentation... but when it came
to presenting their own idea, there were a couple bits I didn't get.

Basically, they want to dump a missile out of the back end of a C-5
doing a zero-G trajectory at max altitude. The missile slows and
descends by parachutes connected to the sled/launcher that also hauled
it out of the C-5. The sled/launcher ends up in the ocean (then
recovered), and the missile has the tanks in front of the payload, so
it can dump the tanks suborbitally and circularize with an OMS. Tanks
burn up on reentry.

So, when the missile fires, does it launch through the middle of the
three chutes? What happens if the sled platform is rocking back and
forth? It seems like pointing accuracy is low here.

Also, doesn't the exhaust burn the chutes on the way up? Does that
mean the sled has another set of chutes? Aren't these things
expensive?

... and, if they wanted to scale it up, isn't it entertaining to
think about a C-5 sized object attempting a mach 2 reentry from
100k feet?

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Anvil* - 20 Jun 2005 20:47 GMT

iain-3@truecircuits:
*snip*

> Basically, they want to dump a missile out of the back end
> of a C-5..

A Minuteman was successfully launched from a C-5 in 1974.
You can search for the multiple times weight and size limitations
have been discussed.
My own concern would be the amount of hazardous materials
enclosed within the plane. I do like air-launch for limited size
launches but a more specialized craft seems prudent. Placing
the potential bomb outside and the flight crew in a capsule that
can eject/separate increases survivability of an event.
--

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iain-3@truecircuits.com - 22 Jun 2005 01:35 GMT

I figured (or read more closely) out how they avoid burning the
'chutes:

They dump the missile out of the sled before it fires it's engines.
So, at T=0 the missile actually has negative velocity to overcome.
The overall delta-V gain claimed for a parachute/high altitude
launch is 1200 ft/sec. If the rocket freefalls for even 5 seconds,
it's lost over 10% of that. Ouch.

I'd wonder about heating of the rocket and payload while it is
backing up into it's own exhaust.

And, yep, they reference the minuteman launch from a C-5.

It seems like a lot of these schemes stem from the insight that a
rocket engine is so pathetically mismatched to the task of
accelerating a great big heavy thing from a stop on the ground.

I suppose if you can rely on the engines igniting you could just
blow the rocket out of a tube with compressed air, like the MX
missile start. That's about the cheapest way I can think of to
throw something up in the air.

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Anvil* - 08 Jul 2005 00:15 GMT

iain-3:

> I figured (or read more closely) out how they avoid burning the
> 'chutes:

-----
Aviation Week & Space Technology/June 27,2005 p32

Seems Transformational Space Corp has developed a lanyard
and chute system to rotate a rocket vertical on drop. Firing
vertically behind the aircraft rather than horizontally and
crossing in front. Seems they will also be pursuing a
pressure-fed rocket design.

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Space Forum / Space Flight / July 2005

The case for air launch