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The Business Case for Reusable Launch Vehicles
An anonymous reader writes "Remember the failures of "shuttle replacements" like VentureStar? A Space Review article argues that even if VentureStar succeeded technically, it and other proposed big RLVs would never have made it financially: they cost too much to develop and wouldn't have made it up through increased launches. What's the solution? The author says that suborbital RLVs, like what Carmack, Rutan, and the other X Prize contenders are working on, will create a business cycle that will eventually lead to orbital vehicles."
The problem with incremental development of RLVs is that there's a huge
leap between the size and difficulty of putting something into space
for five minutes (as in the current X-prize contenders) and putting it
into orbit (as in the shuttle). That will make it difficult to evolve our
way into a commercial space program.
I often find myself pointing out that just getting into space isn't
all that hard. Lifting yourself up 100km requires about a megajoule
(that's the energy equivalent of a stick of dynamite, or about 1/12th
of a gallon of gasoline (about 1/4 kg or 1/2 pound of gasoline), or a
jelly doughnut, or running a hairdryer for 2 minutes) per kilogram of
mass.
By contrast, orbital speed is something like 7000 meters per second,
(or 16,000 miles per hour for you provincials). Getting going that fast
requires an additional 24 megajoules per kilogram of mass (for a total of
25).
In short, the difference between the amount of energy you need to
get into orbit and just into space is a factor of 25, for the same
mass. That ratio of 25 is about equal to the difference between the
latent chemical energies of broccoli and gasoline.
Except that, in the case of space travel, you better be burning
something at least as energetic as gasoline to start with, or you'll
never even hoist yourself up 100km.
The way we've traditionally gotten into orbit is to concentrate the
kinetic energy into ever smaller bits of the vehicle: you use a huge
rocket motor and tanks to get everything started moving, then ditch the
empty tankage and rocket motors for the first stage -- that lets you
concentrate on moving a smaller amount of stuff even faster.
Realistic reusable designs are usually not staged designs,
because it's hard to recover and reuse the first stages. The problem is
that you have to have incredibly lightweight tankage and engines to make
everything work. But pushing stuff to lighter weight makes it more
flimsy and less prone to being reusable. Darn.
The VentureStar, IIRC, ran into problems with exactly this technology --
they were using lightweight carbon fiber tanks to hold their propellant,
and they couldn't make the tank light enough to boost itself into orbit.
The shuttle is NOT a reusable vehicle in any but the most technical
sense of the word: it requires constant skilled redesign and intelligent
(rather than scripted) maintenance, and the engines have to be overhauled
after every flight.
Ed, one of the guys aboard the ISS currently, wrote his take on the future of spaceships, which i thought was a good read.
You're out a bit with that hair dryer. At 2400W (max in places like Australia and New Zealand), it takes 416 seconds to go through a MJ and 555s at 1800W (max for North America (I think: I might be wrong about the 15A)). That's not quite 7 minutes and over 9 minutes, respectively. Even then, I don't think I'd want a 1800W hair dryer pointed at me. That's no hair dryer, that's a hot-air paint stripper!!!
Bill - aka taniwha
--
Leave others their otherness. -- Aratak
acutally, algea produce far more oxygen then the rain forests. too bad the weather pattern changes from the loss of rain forest will probably kill the algea.
The Kruger Dunning explains most post on
RTFWG!
Read The F*ing William Gibson! Not troll, more like alluding to books that should be mandatory reading as an example of 21st century poetry...
Code poet, espresso fiend, starter upper.
Damn good idea.
"Only two things are infinite, the universe and human stupidity, and I'm not sure about the former."
Um. You do know that the only reason that the Space Shuttle isn't fully reusable is that Congress wouldn't pony up enough development (not research) budget at the key point in the architecture cycle? That there existed and exists an entirely plausible design based on the same basic technology that the Shuttle uses?
My degree isn't in aerospace engineering
Ok, perhaps you didn't. So why are you stating that something can't be done when you don't actually know about it?
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"Well, if you want a (not terribly poetic, but still oddly familiar sounding) fictional look at what might happen if some philanthropist/entrepreneur was successful at RLVs, read Michael Flynn's Firestar, followed by three others in the series. Four books could've been tightened up to three, but it's still a good read.
The Spoon
Updated 6/28/2011
Oh, and your defence concerns are bunk.
Any sufficiently advanced technology is indistinguishable from a rigged demo
--Andy Finkel (J. Klass?)
No problem. Check out the NASA history on the subject; it's reasonably good.
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"Once upon a time the USA never had a reputation for doing things on the cheap. But today, it looks like they are trying to do everything on the cheap. (Iraq?) Seems like Washinton has been invaded by penny pinching accountants, or is it body snatchers, I cant remember.
Launching from 100,000 feet and Mach 3 will help even more - there was a proposal to build the third B-70 to support this kind of mission. There are also a couple of advantages of a very high altitude launch - for a given altitude, the velocity will be lower than a ground launch (lower aerodynamic pressure) and the nozzle can be configured for vacuum. The latter allows for a good expansion ratio with moderate pressure - smaller pumps for liquids or thinner cases for solids.
DARPA is currently funding a project called RASCAL (Responsive Access, Small Cargo, Affordable Launch) that would use such a high-altitude, high-speed aircraft to launch small (on the order of 100 kg) spacecraft into LEO quickly and cheaply. Earlier this year they awarded a contract to a startup, Space Launch Corporation, to continue design work on RASCAL. First flight is tentatively scheduled for 2006.
Jeff Foust
The Space Review