Author Topic: Which is ultimately better, reusable rockets vs. spaceplanes?  (Read 8169 times)

Offline whitelancer64

I meant to include airlaunch as well when I made this thread. So airlaunch where the carrier plane carries a spaceplane or where the carrier plane carries a booster. Say you take the stratolaunch plane and take the second stage off the ITS and put them together, would that be superior to the ITS as a whole?

I mean I just sit here and day dream about the future of spaceflight and we have all these new people on the scene with all their schemes but I keep wondering which one in the end will be the superior way of doing things. I think at this point Elon And Jeff have the right idea with VT/VL rockets but at the same time I dont want to shut the door prematurely on other ideas as well.

Say you were given a 100 billion dollars to revolutionize spaceflight so that one day the average man might be able to book a flight into space. Which route would you take? Would you go down the path Elon and Jeff are taking?

ITS won't fit. It's supposed to be about 12 meters in diameter. That's roughly the distance between the two bodies on the Stratolaunch, but the ground clearance for the payload is about 1/4th that.

That aside, air-launch doesn't give you much of a benefit, yes, you save roughly 10% of the fuel it takes to get to the launch altitude, but really it's simpler to just make the first stage ~10% bigger. The major pluses are you do avoid the costs of having to build or lease a launch site and maintain it, and you have more control over when you can launch.
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Offline envy887

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I meant to include airlaunch as well when I made this thread. So airlaunch where the carrier plane carries a spaceplane or where the carrier plane carries a booster. Say you take the stratolaunch plane and take the second stage off the ITS and put them together, would that be superior to the ITS as a whole?

I mean I just sit here and day dream about the future of spaceflight and we have all these new people on the scene with all their schemes but I keep wondering which one in the end will be the superior way of doing things. I think at this point Elon And Jeff have the right idea with VT/VL rockets but at the same time I dont want to shut the door prematurely on other ideas as well.

Say you were given a 100 billion dollars to revolutionize spaceflight so that one day the average man might be able to book a flight into space. Which route would you take? Would you go down the path Elon and Jeff are taking?

ITS won't fit. It's supposed to be about 12 meters in diameter. That's roughly the distance between the two bodies on the Stratolaunch, but the ground clearance for the payload is about 1/4th that.

That aside, air-launch doesn't give you much of a benefit, yes, you save roughly 10% of the fuel it takes to get to the launch altitude, but really it's simpler to just make the first stage ~10% bigger. The major pluses are you do avoid the costs of having to build or lease a launch site and maintain it, and you have more control over when you can launch.

A significant advantage of air launch is you can be high enough to light vacuum engines, and you don't need a TWR much over 1.

But yes, Stratolaunch would have to be TEN TIMES bigger to lift the ITS upper stage. It could lift a hypothetical Falcon-5 sized vehicle with a single Raptor Vac engine, which with ITS mass fractions would SSTO about 15,000 kg to LEO.

Offline Clueless Idiot

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"But yes, Stratolaunch would have to be TEN TIMES bigger to lift the ITS upper stage."  Lol well that's not practical at all so I guess for the foreseeable future reusable rockets really are the future eh? So Elon and Jeff chose the right route to take it seems

Offline envy887

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"But yes, Stratolaunch would have to be TEN TIMES bigger to lift the ITS upper stage."  Lol well that's not practical at all so I guess for the foreseeable future reusable rockets really are the future eh? So Elon and Jeff chose the right route to take it seems

Well, maybe not. The ITS upper stage is kinda massively gigantically large. It's nearly as heavy by itself as the entire Saturn V stack.

For current normal payloads, Stratolaunch with a custom 2-stage expendable rocket is about the right size. It's even  possible that it could launch a fully reusable SSTO with a payload about the size of Dragon.

Offline Clueless Idiot

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"with a payload about the size of dragon" that's not going to revolutionize the world and get millions of people living in space. Fella's I think the verdict is out on this one, reusable rockets will give you the best bang for your buck, and it's so cool because they're being developed with earnest right now, what a time to be alive.

Offline Jim

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Fella's I think the verdict is out on this one, reusable rockets will give you the best bang for your buck,

No, you can't say that for many reasons, among that spaceplanes have not been disproven.  Also, cost savings from reuse have yet to be realized.

Offline edkyle99

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The difference between reusable rockets and spaceplanes is that we know a spaceplane can do the reentry.
We know that VTVL has a good chance of working for first stages.  We know that space planes work for reentry.  The next step seems obvious.

 - Ed Kyle

VTVL 1st stage + spaceplane upper stage?
Something along those lines.  The upper stage would need to reenter at much higher velocity than the first stage.  The winged reentry method (STS, Buran, X-37B, etc.) is proven.  The problem is that this limits the upper stage to LEO.

 - Ed Kyle
« Last Edit: 06/09/2017 03:19 PM by edkyle99 »

Online RonM

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The difference between reusable rockets and spaceplanes is that we know a spaceplane can do the reentry.
We know that VTVL has a good chance of working for first stages.  We know that space planes work for reentry.  The next step seems obvious.

 - Ed Kyle

VTVL 1st stage + spaceplane upper stage?
Something along those lines.  The upper stage would need to reenter at much higher velocity than the first stage.  The winged reentry method (STS, Buran, X-37B, etc.) is proven.  The problem is that this limits the upper stage to LEO.

 - Ed Kyle

LEO isn't a problem if it can hand off the payload to a cislunar tug. That will cover everything except the occasional interplanetary mission.

Online Lars-J

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Which is ultimately better, reusable rockets vs. spaceplanes?
« Reply #48 on: 06/11/2017 05:25 PM »
My personal belief is that in the future, spaceplanes will seem like a quaint dead end for aerospace.

The appeal of spaceplanes seems to in my opinion be primarily emotional, and linked to the heavy involvement of test pilots in early space flight. This pilot lobby remained a strong force in NASA before and during the shuttle program.

While it is no doubt possible to build a fully reusable space plane system, it does not appear to be the optimal solution.

Again, this is my opinion and I reserve the right to be proven wrong. :)
« Last Edit: 06/11/2017 05:26 PM by Lars-J »

Offline john smith 19

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The difference between reusable rockets and spaceplanes is that we know a spaceplane can do the reentry.
We know that VTVL has a good chance of working for first stages.  We know that space planes work for reentry.  The next step seems obvious.

 - Ed Kyle

VTVL 1st stage + spaceplane upper stage?
Something along those lines.  The upper stage would need to reenter at much higher velocity than the first stage.  The winged reentry method (STS, Buran, X-37B, etc.) is proven.  The problem is that this limits the upper stage to LEO.

 - Ed Kyle
So you're looking at first stage staging around M10 with a winged 2nd stage to take it and the payload to orbit then coming back.

I've never ceased to be boggled at the concept of VTHL. You need a vehicle that's strong in two major axes and big enough to carry all the propellant.

This has always seemed to me to give you the worst of both worlds. 
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Online Lars-J

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I've never ceased to be boggled at the concept of VTHL. You need a vehicle that's strong in two major axes and big enough to carry all the propellant.

Yes, and that applies to both VTHL and HTHL. (The latter is actually worse, since it needs to sit on the tarmac and lift off fully loaded, whereas VTHL spaceplanes only need to support its near-empty weight while horizontal)

Online Patchouli

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LEO isn't a problem if it can hand off the payload to a cislunar tug. That will cover everything except the occasional interplanetary mission.

I think in the future this will eventually prove to be the most cost effective solution as this makes full reusability a lot easier.
Kinda like how things were in the Space Odyssey movies.

Though a reusable rocket and a space plane are not mutually exclusive as the latter can be a payload for a reusable rocket and a SSTO one could simply fill a different role.

I think  HTHL type space planes probably will win out for passenger service since they have easier boarding, lower g throughout the mission, and have better abort options etc while VTOL rockets will likely end up carrying most of the large cargo.
On better abort options for example if half the thrust is lost soon after take off on a vehicle like Skylon it doesn't immediately fall out of the sky and can turn around and land.
If something goes wrong early during take off a T+0 failure just kill the thrust and hit the brakes like in this video of an aborted takeoff.

« Last Edit: 06/16/2017 05:59 AM by Patchouli »

Offline john smith 19

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Yes, and that applies to both VTHL and HTHL. (The latter is actually worse, since it needs to sit on the tarmac and lift off fully loaded, whereas VTHL spaceplanes only need to support its near-empty weight while horizontal)
The difference is only 3 VTHL cargo carrying vehicles have ever flow and only one of them had primary thrust operating through its launch axis.

In contrast several thousand HTHL designs have been developed in the 114 yrs since the Wright brothers first flight.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline TrevorMonty



LEO isn't a problem if it can hand off the payload to a cislunar tug. That will cover everything except the occasional interplanetary mission.

I think in the future this will eventually prove to be the most cost effective solution as this makes full reusability a lot easier.
Kinda like how things were in the Space Odyssey movies.

If lunar or asteriod supplied fuel to LEO ever becomes cheap enough it could partially refuel a SSTO for earth return. A SSTO becomes lot simplier and lighter if it has amble fuel for retropulsive burn and landing.
Water or cryo fuel can also be used for cooling of heat shield surfaces.
« Last Edit: 06/17/2017 08:04 PM by TrevorMonty »

Offline QuantumG

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If lunar or asteriod supplied fuel to LEO ever becomes cheap enough it could partially refuel a SSTO for earth return. A SSTO becomes lot simplier and lighter if it has amble fuel for retropulsive burn and landing.
Water or cryo fuel can also be used for cooling of heat shield surfaces.

... or as I was saying a few years ago, heat shields are going to look pretty antiquated as soon as cheap propellant is available in LEO. At least for any cargo you care about getting to the ground in one piece - especially crew.

BTW, I'd even go beyond extraterrestrial propellant... if you have a reusable tanker that can take fuel to orbit then it makes sense to increase retropropulsion on any crew carrying vehicle that can refuel.
Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

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