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#1
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The case for air launch
http://mae.ucdavis.edu/faculty/sarig...a2001-4619.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? |
#2
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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. -- |
#3
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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. |
#4
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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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