156 posts in this topic

So one of the recurring problems of SSTOs, it seems is simply the energy density of the fuel means you can't afford the structural mass fraction.
Perhaps we're going about this the wrong way.
I know, there's no appreciable benefit to flying your butt into orbit instead of just gravity turning your way there.

But let's say that's what really tickles your pickle, I believe it is possible, albeit with a different fuel source.
Hydrocarbons have too poor an ISP, LH has too low density, and LOX just doesn't have the kick we need.

So what do we do?
Well, we need a fuel that has friendly characteristics such as high hydrogen content, liquid or easily liquified, and our oxidizer needs the same but freferably with a little more pep than LOX.

The answer, I think, is Tetraborane and Chlorine Trifluoride, feeding a linear aerospike on a blended wing body craft.

Is this stuff poisonous, corrosive, and violently reactive with almost all substances?
You better believe it.
But hey, the Gemini astronauts rode the Titan, fueled by UDMH and Nitrogen Tetroxide.

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If the whole point of an SSTO is to make space cheap, then using massive amounts of highly toxic, corrosive and violently reactive fuels is not going to help you. Any cost reduction you might get by saving a stage is going to be offset by the costs of producing, handling, and storing propellants.

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On 3/24/2017 at 2:34 AM, Nothalogh said:

So one of the recurring problems of SSTOs, it seems is simply the energy density of the fuel means you can't afford the structural mass fraction.
Perhaps we're going about this the wrong way.
I know, there's no appreciable benefit to flying your butt into orbit instead of just gravity turning your way there.

But let's say that's what really tickles your pickle, I believe it is possible, albeit with a different fuel source.
Hydrocarbons have too poor an ISP, LH has too low density, and LOX just doesn't have the kick we need.

So what do we do?
Well, we need a fuel that has friendly characteristics such as high hydrogen content, liquid or easily liquified, and our oxidizer needs the same but freferably with a little more pep than LOX.

The answer, I think, is Tetraborane and Chlorine Trifluoride, feeding a linear aerospike on a blended wing body craft.

Is this stuff poisonous, corrosive, and violently reactive with almost all substances?
You better believe it.
But hey, the Gemini astronauts rode the Titan, fueled by UDMH and Nitrogen Tetroxide.

Two questions.

First, what kind of performance do you think this could provide? Do you have any specific numbers you've put together?

Second, whatever SSTO-performance-enabling technology you might posit, how would an SSTO be able to beat a TSTO using the same?

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14 minutes ago, sevenperforce said:

First, what kind of performance do you think this could provide? Do you have any specific numbers you've put together?

Second, whatever SSTO-performance-enabling technology you might posit, how would an SSTO be able to beat a TSTO using the same?

No definitive idea, as I stated, I'm just spitballing for the people that have a boner for SSTOs regardless of the physical detriments of such an approach.

Quote

But let's say that's what really tickles your pickle, I believe it is possible

Which was prefaced by this

Quote

One of the recurring problems of SSTOs, it seems is simply the energy density of the fuel means you can't afford the structural mass fraction

One piece of technology I forgot to mention at all was the concept of the Air-Augmented Rocket, best demonstrated in the ultra low mass Soviet ICBM project developed by KBM

http://www.astronautix.com/g/gnom.html

Edited by Nothalogh

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In the real world I think the parallel stage to orbit is going to be the most efficient option, as far as not wasting payload mass on hauling engines into the stratosphere before using them.

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1 hour ago, Thor Wotansen said:

In the real world I think the parallel stage to orbit is going to be the most efficient option, as far as not wasting payload mass on hauling engines into the stratosphere before using them.

There is a critical trifecta: parallel staging (with or without crossed), air augmentation, and altitude compensation. Using all three, SSTO-like operations should be readily achievable. 

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