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The History And Future Of Spaceplanes

Jess Sponable of AFRL is giving a talk with the post title.

Jess starts out by noting the upcoming fifteenth anniversary of DC-X flight tests.

Common vision between industry and government of reliable, routine, diverse and affordable space access. Confident that it is coming at us, though not sure when.

Discussing HAVE REGION program of the 1970s, which was to develop structural concepts for potential space planes. Subject to thermal and aero loads in test chambers on the ground. All airframes came in within three percent of estimates. Validated loads, with some articles tested to destruction, some deliberately, some otherwise. Best vehicle was Boeing RASV. Honeycomb structure, with very little metal. Highly classified at the time, but now all declassified. Came very close to SSTO weightwise, but concerns were about durability and operability.

Talking about NASP, now. We learned that it's really really hard to get an airbreather all the way to orbit. Have to spend too much time in the atmosphere to take advantage of the scramjet. Had high ISP, but horrible engine T/W--even worse than conventional aircraft engines, and hydrogen fuel was required, which required very large tanks because of its low density. It was a very complex vehicle in terms of shapes, and the heating problems of flying that low in the atmosphere at such higher velocities were very challenging. It would have been a very large vehicle.

Now going on into other SSTO projects. Points out that Mike Griffin actually started the DC-X program while at SDIO. DC-X/XA was the best program he ever worked on. It didn't have to work because it was a test vehicle. They had a 26-hour turnaround time. Pete Conrad was determined to demonstrate three flights a day. Very low infrastructure required (~$600K). First ever composite linerless oxygen tank, long before X-33 tank failed a few years later. NASA tried X-34 and X-33 which both failed.

A missed opportunity was not extending the DC-X program with a more integrated airframe and fly to Mach 8, for about $90M. Once you've flown something and developed that experience base, it's cheaper to extend it. Had they gone for Mach 8 from the beginning of DC-X, it would have been a billion dollar program.

Lesson learned was that two-stage, hydrocarbon fuels is a winner, despite the loss in Isp, because the vehicles are so much smaller. Isn't saying that SSTO isn't the right answer, and that you couldn't build a demonstrator, but it might not be operable.

The reason that the commercial sector is important is because we don't have any choice. We don't have the money to do it the way the government does. Build quick, reduce risk will be a quarter of the cost of government program business as usual.

The good news is that the entrepreneurs are starting to engage, and they're putting a lot more into it than either NASA or the Air Force are interested in. Talking about Bezos, Branson, Musk, Carmack. John Carmack has a great approach--just go build it.

As naval power was built on the back of maritime power (ocean commerce) the Air Force will have to engage with the private sector. AF is continuing to engage in technology push toward operability. Will trade performance gains for operability, which also pushes toward two-stage. Building a ground-based demonstrator tank (common bulkhead) that they want to evolve into a Mach 7 test vehicle. Technology will support wide range of applications.

Mach 12 vehicle will be about the size of an F-15. Not big vehicles with hydrocarbons--lots of room for growth.

Pure energy price to put a person into orbit is about $76. To actually approach that cost will require much higher flight rates than are required by the Air Force, which is why they have to partner with the private sector and private markets.

In giving XCOR the contract, they're not paying them to build a flight test vehicle--they're doing that with their own money. They're paying them for technology development, and it will be shared with the industry. "Build an industry, not just a government program."

Increase in the of knowledge doubling dramatically increasing. By 2020 knowledge will be doubling every 73 days. Time is on our side. AFRL will be continuing to push and mature technology that are beyond our horizon, but some of them will be helpful to us now.

Technologies are more complex than initial Wright work for airplanes, but we are getting to the point that we can do amazing things with small teams. Discussing technology exchange forum in Dayton where they will present their technologies to private developers to make them aware of what the Air Force has. Also a three-day workshop in New Mexico for the DC-X anniversary to discuss lessons learned for the future.

 
 

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8 Comments

ralphe wrote:

Here is what I think about the present and future of space planes, assuming there is one.

I applaud everyone working to make a workable, lower cost, earth to orbit vehicle, but we have given up the high ground to the neo-luddites by limiting our options. I think, and the equations seem to agree, that chemical fuels are always going to be costly and improvements in performance will be at the margins. The mass fractions will never work. Space advocates should be pushing nuclear power.

After years of seeing irrational obstruction. new nuclear plant licenses are in the works. We should be talking about using nuclear propulsion for our space program and especially anything leaving from Earth orbit.

Itís easy to fault NASA for being to expensive, but private players doing more for less just canít bring the costs down enough to gather much popular support. If we are going anywhere in the future we will be using nuclear or something else we havenít even considered seriously.

So I ask, are we fighting for a commercial space program using chemical propulsion because it is the best there is, or just because we know that it is as much as is achievable? I will go along with what works, but I think that changing the popular view of nuclear power will get us into an interplanetary civilization long before even the best non governmental chemical programs will.

Rand Simberg wrote:

I think, and the equations seem to agree, that chemical fuels are always going to be costly and improvements in performance will be at the margins. The mass fractions will never work.

You're wrong. There's nothing in "the equations" that demand that spaceflight be anywhere near as costly as it is now. Cost has little to do with mass fractions.

I have to agree with Anonymous. Chemical rockets can be made substantially cheaper than they are today by rethinking the systems architecture. (With the notable exception of XCOR, where I am obviously biased in their favor, most chemical rocket systems ever built can trace their heritage to taking off from Peenemunde and dropping bombs on London. That's not a systems design that optimizes for operations cost.)

Chemical fuels will always be costly
Kerosene is three bucks a gallon, and LOX is cheaper than beer. Fuel (actually, propellant) is cheap, systems are (currently) expensive.

I'm a big fan of nuclear rockets, beamed propulsion, space elevators, whatever... and I curse NASA for shutting down NIAC which could afford to actually look at some of that stuff. But chemical rockets are good enough to build thriving commercial enterprises from Earth to orbit. Once in LEO, then you can light off your nuclear rocket since, as Jeff Greason says, "space is already radioactive."

Monte Davis wrote:

"It didn't have to work because it was a test vehicle."

Tattoo that on the forehead of every NASA administrator, Congressional committee chair, and space fan. The more we throttle back impatience for the Breakthrough Operational Vehicle, the better our chances of learning what we need to actually bring it within reach. Festina lente and Reculer pour mieux sauter and all that.

"The reason that the commercial sector is important is because we don't have any choice. We don't have the money to do it the way the government does."

Exactly. I tune out whenever people go off about the wonderfulness of the market, how the private sector is always cheaper and faster and smarter and more lovable than dumb old government. What matters most is that it has to take smaller bites -- and that's what's needed (see above), whoever does it.

Rand Simberg wrote:

Actually, I was "anonymous." Sorry 'bout that.

T.L. James wrote:

First ever composite linerless oxygen tank, long before X-33 tank failed a few years later.

This might be a little misleading for those who didn't follow X-33 closely (probably the ambiguity of hurried liveblogging). The LOX tank on X-33 wasn't composite (aluminum), and the composite tank that failed was an LH2 tank.

Brock wrote:

"Pure energy price to put a person into orbit is about $76."

Whoa. Could someone elaborate on what this means? This is the lowest figure I've every seen for reaching orbit. If kerosene is $3/gallon, does that mean it only takes 25 gallons of kerosene to put someone into orbit? Or is that some other kind of fuel? What kind of energy are we talking about here? Am I right to assume that this number does not include "minimal" shielding / ship weight?

Theoretically, if we developed a one-seater rocket that weighed 150 pounds (it's pure composite), ran on autopilot (no salary for pilots), and was mass produced for $75, does that mean $75+75+75 = $225 to orbit, not including the cost of your suit and a filled air tank? Is that what this means?

Rand Simberg wrote:

I assume that it's a calculation purely of the energy difference (kinetic and potential) between being in orbit and on the ground, including no consideration of how this is achieved.

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This page contains a single entry by Rand Simberg published on March 27, 2008 5:19 PM.

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