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Old 04-14-2014, 06:36 PM   #31
scc
 
Join Date: Mar 2013
Default Re: [Spaceships] Winged Spaceships

OK then, if I use the Merlin-1D thrust to weight ratio of 150, yielding 7.5 Gs my atmospheric speed is 1.9 mps, with a 5.74 needed for orbit I only need 3.84 mps.

Using the KVD-1's Isp of 462 I get .154 mps per tank of fuel, 15 fuel tanks will get me into orbit with room to spare (0.318 mps) carrying 190 tons of cargo (I think that can work)

Altogether this means it takes $600,000 of rocket fuel to lift 190 tons of cargo to orbit, that's $3157.89 per ton or or $1.41 per pound
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Old 04-14-2014, 08:07 PM   #32
Anthony
 
Join Date: Feb 2005
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Default Re: [Spaceships] Winged Spaceships

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Originally Posted by scc View Post
OK then, if I use the Merlin-1D thrust to weight ratio of 150, yielding 7.5 Gs my atmospheric speed is 1.9 mps, with a 5.74 needed for orbit I only need 3.84 mps.
Remember, accelerating to atmospheric speed costs fuel. There's no point unless you have an air-breathing thruster that has better performance than your rocket.
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Old 04-14-2014, 08:32 PM   #33
scc
 
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Default Re: [Spaceships] Winged Spaceships

Yes, but it uses a lot less fuel. The F1 has a 2.27:1 ratio of oxidizer to fuel
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Old 04-14-2014, 08:55 PM   #34
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Default Re: [Spaceships] Winged Spaceships

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Yes, but it uses a lot less fuel.
The systems you mentioned are rocket engines. They don't change fuel consumption for atmospheric use -- if you want to use less fuel, you'll need an air-breathing engine.
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Old 04-14-2014, 09:02 PM   #35
scc
 
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Default Re: [Spaceships] Winged Spaceships

The thread of discussion had moved onto rocket engines with air intakes
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Old 04-14-2014, 09:25 PM   #36
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Default Re: [Spaceships] Winged Spaceships

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The thread of discussion had moved onto rocket engines with air intakes
The performance of such engines is at best incidentally related to the performance of rocket engines from fuel tanks, as liquid oxygen has somewhere on the order of 5,000 times the oxidizer density of air. Realistically, you probably need a completely different engine, and in any case you should model it as a ramjet or scramjet, not a rocket.
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