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Build an arbitrarily large SSTO rocket


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This is pretty simple, but I don't believe it has been posted yet, so here goes.

Empirical testing shows that a stack of six LFTs and one LFE can lift 3.2 mass units into orbit. A decoupler on the bottom of the stack is currently necessary to avoid the sticky pad, and liftoff is slow like you wouldn't believe, but it works.

Now, it is possible to build radially outwards by adding the following components: A radial decoupler, a SFB attached to it, and a stack decoupler attached to the SFB (which can be omitted for style points). These components have a total mass of 3, giving a net gain of .2 mass per stack; at this point simply add as many stacks as needed. Your only limits are pilot skill, computer horsepower, and launchpad size.

Vertical snapping is a huge help for stability here. You can turn it on in the settings.cfg file.

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So, how many stacks would it take to carry a 3xLFT+1xLFE to orbit, so you could SSTO twice in a row?

Counting the CP and a decoupler, that's a mass of 11.3, so you'd need a minimum of fifty-seven, not allowing for any additional dead weight in the form of controls and struts.

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Counting the CP and a decoupler, that's a mass of 11.3, so you'd need a minimum of fifty-seven, not allowing for any additional dead weight in the form of controls and struts.

I just got this:

Yawmaster + CP + 3xLFT + 1xLFE + Decoupler

Into a 70km circular orbit with enough fuel to spare for a deorbit burn with this:

Tricoupler + 3x((6xLFT + 1xLFE) + 3x(Radial Decoupler + SRB + SAS + 5xLFT + 1xLFE)) + struts

...and I didn't use vertical snapping :P

MECO:

fcs88.png

Apokee:

5XCn5.png

And a nice, 'soft', touchdown (which apparently scared the pants off Jeb).

nIf6g.jpg

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Yeah, I've been thinking about it; tricouplers allow for much better efficiency. Your lofted mass per stack with a radial-SFB-radial-SFB-decoupler-tricoupler-<stack> is 1.2 instead of 0.2, and going straight to the tricoupler on the main stack gives you a carry weight of 8.8 right there.

Hum. E'en with that I'm not sure how you managed. Evidently my math is out somewhere. Perhaps that sixth LFT is more trouble than it's worth.

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Yeah, I've been thinking about it; tricouplers allow for much better efficiency. Your lofted mass per stack with a radial-SFB-radial-SFB-decoupler-tricoupler-<stack> is 1.2 instead of 0.2, and going straight to the tricoupler on the main stack gives you a carry weight of 8.8 right there.

Hum. E'en with that I'm not sure how you managed. Evidently my math is out somewhere. Perhaps that sixth LFT is more trouble than it's worth.

He also omitted the radial decoupler between the SRBs and the liquids. I'm not sure you realize, but in theory, this multiplies your payload-per-stack by 5 since it frees up an additional 0.8 on top of the 0.2 you mentioned. So I believe this works out to... 12 stacks, WITH the Command Pod and no SAS?

Also, do you think you could fire the boosters without stuff exploding? I bet that'd help even more, if only because they'd be empty by the time you got to altitude (thus reducing the mass your liquids must accelerate to orbital speeds).

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He also omitted the radial decoupler between the SRBs and the liquids.

Er, no? He lists radials. What he omits is the stack decoupler, but he adds SAS modules, so he's not saving weight per stack.

And yes, you could, in theory, burn the solids on top of the LFT stacks. You'd need to dump heat via struts or winglets, but you can prevent explosions.

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Hum. E'en with that I'm not sure how you managed. Evidently my math is out somewhere. Perhaps that sixth LFT is more trouble than it's worth.

It's not as simple as '6x can get 1y into orbit, therefore 600x can get 100y into orbit'. I think it's just that the biggest hurdle of getting something into orbit is actually getting it out of (most of) the atmosphere at a decent rate. Once you're there you can take your sweet time gravity turning into a circular orbit with weak engines and no fuel. The design I used could probably be made more efficient by reducing the number of LFTs on each 'booster' stack, thereby providing more T/W at launch and less dead weight once you're up in the air.

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It's not as simple as '6x can get 1y into orbit, therefore 600x can get 100y into orbit'. I think it's just that the biggest hurdle of getting something into orbit is actually getting it out of (most of) the atmosphere at a decent rate. Once you're there you can take your sweet time gravity turning into a circular orbit with weak engines and no fuel. The design I used could probably be made more efficient by reducing the number of LFTs on each 'booster' stack, thereby providing more T/W at launch and less dead weight once you're up in the air.

I beg to differ; when building laterally, 600x will get you 100y. But, as you say, better TWRs can be a better option that more fuel.

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