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11 Comments
Dfens wrote:
So the only problem with the Saturn V was that they didn't launch the first stage vertically? If they'd done that and shut off the engines with enough fuel and oxidizer in the tanks to allow it to make a nice, soft landing at the launch pad (yeah, how much could that possibly take), then they could have launched only a single upper stage instead of two and that vehicle would have magically put a huge payload into orbit. I've got to party with that guy. He's got the good stuff.
Rand Simberg wrote:
So the only problem with the Saturn V was that they didn't launch the first stage vertically?
No.
Why do you feel compelled to make idiotic comments on my blog?
Robert wrote:
Dfens, you probably already know this, but just in case:
If you are interested in using two stage Saturn-V derived launch vehicles, look up Skylab 1 and Saturn INT-21.
For reusable concepts, you could google "Saturn flyback" and "Saturn-Shuttle".
Dfens,
Well, yes, if you:
a) made the F-1 engines throttleable
b) developed flight control algorithms for landing the thing
c) accepted a much lower payload to orbit, because of course there's a tradeoff there
d) spent a lot of extra time and money making the thing reusable, etc etc.
I wasn't making the argument that "them thar NASA guys don't know what they were doin." I was arguing that if you're trying to get to low-cost access to space, here's a good approach for doing it.
Dfens,
Well, yes, if you:
a) made the F-1 engines throttleable
b) developed flight control algorithms for landing the thing
c) accepted a much lower payload to orbit, because of course there's a tradeoff there
d) spent a lot of extra time and money making the thing reusable, etc etc.
I wasn't making the argument that "them thar NASA guys don't know what they were doin." I was arguing that if you're trying to get to low-cost access to space, here's a good approach for doing it.
~Jon
Brock wrote:
Why do you feel compelled to make idiotic comments on my blog?
Because everyone responds to him? Don't feed trolls.
Dfens wrote:
Significantly lowering the efficiency of the vehicle is probably not going to reduce launch costs a lot. This vehicle is going to have very small payload margins as Jonathan duely notes. In fact, I'd be surprised if they were positive. Plus it's going to fight its way through a sea of oxidizer on its way up. Plus landing gear is going to be a big issue for a vehicle of this size and will drive the structural mass fraction. This one's no more of a keeper than that Delta Clipper was.
If you look at the energy equation for getting a mass to orbit 5% should go to lift and 95% to velocity. In rockets that percentage is almost reversed. To me that indicates the place to gain effeciency is in lift. Rocket engines are remarkably inefficient at producing lift and we should have moved past that idea a long time ago.
Rand,
FWIW, I woke up early this morning, so I was able to get Part IV up this afternoon during lunch.
~Jon
Dfens wrote:
You missed the only one that's actually been done, an airbreathing, Mach 3.4, fly back first stage with a flyback, rocket powered second stage. It was proposed by Boeing in the mid '80s. It was all anyone was talking about at the Kent Space Center those days. It was sure a hell of a lot smarter than anything that came out of NASA's ALS program. The proposal team for ALS wanted to submit a non-flyback cargo rocket 2nd stage version of it to NASA as an unsolicited proposal, but managment wouldn't let them. It would have been a futile effort anyway. It would have launched 15 payloads a day instead of 10 a year like their beloved shuttle "fleet". There's another sweet spot in the optimization curve at Mach 2 if you want to make an all aluminum first stage instead of using more expensive and heat resistant materials. But why have a serious space program when the current version offers so many laughs?
Dfens,
By definition an approach that has only been proposed and never built or tested cannot be considered to have "actually been done". As it is, that small improvement in staging Mach costs you a lot in extra airbreathing hardware. There's better ways of eking out a little more performance from a glideback stage than adding a second propulsion system.
~Jon
Dfens wrote:
You neither know whether or not this has been built, nor do you know how to design space systems better than the people who patented this idea.
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This page contains a single entry by Rand Simberg published on June 16, 2008 5:53 AM.
So the only problem with the Saturn V was that they didn't launch the first stage vertically? If they'd done that and shut off the engines with enough fuel and oxidizer in the tanks to allow it to make a nice, soft landing at the launch pad (yeah, how much could that possibly take), then they could have launched only a single upper stage instead of two and that vehicle would have magically put a huge payload into orbit. I've got to party with that guy. He's got the good stuff.
So the only problem with the Saturn V was that they didn't launch the first stage vertically?
No.
Why do you feel compelled to make idiotic comments on my blog?
Dfens, you probably already know this, but just in case:
If you are interested in using two stage Saturn-V derived launch vehicles, look up Skylab 1 and Saturn INT-21.
For reusable concepts, you could google "Saturn flyback" and "Saturn-Shuttle".
Dfens,
Well, yes, if you:
a) made the F-1 engines throttleable
b) developed flight control algorithms for landing the thing
c) accepted a much lower payload to orbit, because of course there's a tradeoff there
d) spent a lot of extra time and money making the thing reusable, etc etc.
I wasn't making the argument that "them thar NASA guys don't know what they were doin." I was arguing that if you're trying to get to low-cost access to space, here's a good approach for doing it.
~Jon
Dfens,
Well, yes, if you:
a) made the F-1 engines throttleable
b) developed flight control algorithms for landing the thing
c) accepted a much lower payload to orbit, because of course there's a tradeoff there
d) spent a lot of extra time and money making the thing reusable, etc etc.
I wasn't making the argument that "them thar NASA guys don't know what they were doin." I was arguing that if you're trying to get to low-cost access to space, here's a good approach for doing it.
~Jon
Why do you feel compelled to make idiotic comments on my blog?
Because everyone responds to him? Don't feed trolls.
Significantly lowering the efficiency of the vehicle is probably not going to reduce launch costs a lot. This vehicle is going to have very small payload margins as Jonathan duely notes. In fact, I'd be surprised if they were positive. Plus it's going to fight its way through a sea of oxidizer on its way up. Plus landing gear is going to be a big issue for a vehicle of this size and will drive the structural mass fraction. This one's no more of a keeper than that Delta Clipper was.
If you look at the energy equation for getting a mass to orbit 5% should go to lift and 95% to velocity. In rockets that percentage is almost reversed. To me that indicates the place to gain effeciency is in lift. Rocket engines are remarkably inefficient at producing lift and we should have moved past that idea a long time ago.
Rand,
FWIW, I woke up early this morning, so I was able to get Part IV up this afternoon during lunch.
~Jon
You missed the only one that's actually been done, an airbreathing, Mach 3.4, fly back first stage with a flyback, rocket powered second stage. It was proposed by Boeing in the mid '80s. It was all anyone was talking about at the Kent Space Center those days. It was sure a hell of a lot smarter than anything that came out of NASA's ALS program. The proposal team for ALS wanted to submit a non-flyback cargo rocket 2nd stage version of it to NASA as an unsolicited proposal, but managment wouldn't let them. It would have been a futile effort anyway. It would have launched 15 payloads a day instead of 10 a year like their beloved shuttle "fleet". There's another sweet spot in the optimization curve at Mach 2 if you want to make an all aluminum first stage instead of using more expensive and heat resistant materials. But why have a serious space program when the current version offers so many laughs?
Dfens,
By definition an approach that has only been proposed and never built or tested cannot be considered to have "actually been done". As it is, that small improvement in staging Mach costs you a lot in extra airbreathing hardware. There's better ways of eking out a little more performance from a glideback stage than adding a second propulsion system.
~Jon
You neither know whether or not this has been built, nor do you know how to design space systems better than the people who patented this idea.