Author Topic: Pure Fantasy: BFR as S1, SLS Core w/ J-2X as S2  (Read 12170 times)

Offline TomH

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Re: Pure Fantasy: BFR as S1, SLS Core w/ J-2X as S2
« Reply #20 on: 03/03/2016 07:58 pm »
I put this together rather quickly, so is this the general idea?  It is big!

Yea, that's the idea. Payload may well differ though.

While the idea was a bit of a lark, I have to wonder whether it would actually be cheaper than developing Dark Knights, RS-25-E and EUS. The BFR would be reusable and also would impart a whole lot more impulse than solid boosters. I would think you could put a massive lunar lander below that Orion and use the SLS core all the way through TLI and maybe even as a crasher stage for a one stage LM that could achieve polar landing.

I think this architecture is something NASA could afford (leasing the BFR launch service) while SpaceX concentrates on Mars. It would provide a robust single launch architecture. SpaceX and NASA could still assist each other in their respective venues.

Offline 93143

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Re: Pure Fantasy: BFR as S1, SLS Core w/ J-2X as S2
« Reply #21 on: 03/03/2016 08:41 pm »
Expecting to come along 30 years later and use the components in a fundamentally different design is madness.

Actually the Shuttle stack (sans orbiter) is a pretty obvious candidate for redesign into an inline launcher, which is why the idea has kept showing up over the last 38 years.  Lose the spaceplane, put the engines on the bottom of the tank and the payload on top.  You'd have to redesign the tank into a core stage to make this work, but most of the production infrastructure can be common, and the launch infrastructure can be the same, so you can keep flying Shuttle while developing and flying Magnum NLS-1 Jupiter SLS...  wait.  Nuts.
« Last Edit: 03/03/2016 08:49 pm by 93143 »

Offline spacenut

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Re: Pure Fantasy: BFR as S1, SLS Core w/ J-2X as S2
« Reply #22 on: 03/04/2016 12:12 am »
The ideas to redesign the shuttle stack I've seen over the years were very good ideas.  It was to keep the existing manufacturing infrastructure in place.  Problem is, we have waited so long and over engineered the whole thing over many years, that SLS has become a kludge and a very expensive one to say the least. 

I am not a rocket scientist but a "space nut".  However, from the outside looking in, a side mount early on or the Jupiter Direct plan was the best and lowest cost to get super heavy lift going faster.  Now, by the time the SLS is developed and ready for launch, Falcon Heavy, Vulcan, SEP tugs, fuel depots, along with potential BFR will make it to expensive to work. 
« Last Edit: 03/04/2016 12:13 am by spacenut »

Offline Paul451

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Re: Pure Fantasy: BFR as S1, SLS Core w/ J-2X as S2
« Reply #23 on: 03/05/2016 05:42 am »
Expecting to come along 30 years later and use the components in a fundamentally different design is madness.
Actually the Shuttle stack (sans orbiter) is a pretty obvious candidate for redesign into an inline launcher, which is why the idea has kept showing up over the last 38 years.

I'm aware it's obvious, it's just picking the wrong vehicle to start.

The Shuttle itself was an impossible design goal. It shouldn't have worked, it was too far beyond the state-of-the-art. Hence every system and sub-system was not only engineered to within an inch of its life, the whole collective system was a finely balanced compromise of the various impossibilities. Change one element and you destroy that balance, you end up in a worse position than merely starting with a blank sheet of paper.

That's why even moderate changes such as switching to liquid boosters, or the shuttle-c (still side-mount), proved to be too expensive to seriously contemplate while still operating the Shuttle. You can't swap out the orbiter with a cargo carrier, nor the boosters with different boosters, nor significantly upgrade the orbiters themselves, without also having to redesign the rest of the system. There's not only no savings from reusing parts, there's added costs.

If you want to Lego a rocket, you have to start with a system which was either designed to be flexible, or was designed with solid engineering margins.

It's the difference between building a castle with Lego bricks and building one with playing cards.

[Aside: Had the Shuttle stack been originally tested with an expendable cargo stage before the manned "reusable" orbiters were ready, then it might, by necessity, have been more flexible. Leaning towards a design like Energia, which was intended to be more adaptable: Side-stack, or in-line, multiple booster configurations, etc. But Energia was developed with 20/20 hindsight.]

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