NASA Sets Initial Requirements For Next-Generation Orbital Space Plane System

Feb. 18, 2003 -- NASA today released the top level requirements for the Orbital Space Plane (OSP), a next generation system of space vehicles designed to provide a crew rescue and crew transport capability to and from the International Space Station. These requirements set the foundation for the design of the vehicle and its associated systems.

The Level I requirements for an OSP system were developed based on NASA's missions, as defined in the Integrated Space Transportation Plan, input from industry and Department of Defense partners participating in the program. The requirements were reviewed at multiple levels within NASA. The final review and approval process included the NASA Administrator, Deputy Administrator, Associate Administrator for the Office of Aerospace Technology, and the Associate Administrator, Office of Space Flight.

"This is an important first step in making the Integrated Space Transportation Plan a reality," said NASA Deputy Administrator Frederick Gregory. "The Orbital Space Plane system will give us the flexibility needed to safely and efficiently get crew to and from orbit and to provide crew rescue and logistical support to the International Space Station. These initial requirements help to outline a comprehensive system that will significantly complement the capabilities of our existing Space Shuttle fleet," he said. Any future changes to the Level I Requirements would be considered by the Orbital Space Plane Program Office and require approval from the NASA Executive Council. The program is in the process of developing Level II Requirements for the OSP system. Unlike the Level I requirements, which were defined by NASA, Level II requirements will be defined at the program level and will be detailed in a document referred to as the Systems Requirements Document (SRD) planned for release no later than late 2003.

Editor's Note: The original news release can be found here.

Note: This story has been adapted from a news release issued for journalists and other members of the public. If you wish to quote any part of this story, please credit National Aeronautics And Space Administration as the original source. You may also wish to include the following link in any citation:

http://www.sciencedaily.com/releases/2003/02/030219081318.htm

I've seen discussions of next generations space planes before, and I've also seen discussions of a "space elevator". I remember an idea I saw in an old sci-fi movie from the fifties. The basic idea is a rail that a rocket goes along until it gets up to speed, and is then launced into orbit.

In the real world, the launch rail and rocket would instead be an electromagnetic rail, a carrier, and a payload designed to survive the heat of exiting the atmosphere. Once in orbit the capsule could dispose of the used up heat shielding and proceed with its mission.

Escape velocity is something like five miles per second. My question is would a system like this have any possibility of being technically and economically feasible? I have this vision of a hundred miles of electromagnetic rail traversing the desert, with an ever so slight rise during the last few miles to ensure the payload makes it over the horizon. Is this vision purely sci-fi, or does it offer enough practical advantages to be worth pursuing?

Is this vision purely sci-fi, or does it offer enough practical advantages to be worth pursuing?

One way to look at this is with a question? Why don't we take off horizontally now? Answer: Drag. Rockets take off vertically - despite needing to overcome gravity by brute force with no lift whatsoever - because they've got to get to low drag conditions as soon as possible.

The shuttle sheds as much velocity as all that rocket fuel added during takeoff - for free - by scrubbing it off against air. And it does virtually all of it above 100,000 feet (meaning if you want to use a 'flying' system,you'd have to get above that high, or you're facing the same drag that slows it down on re-entry).

Is it hopeless? Nothing technical is hopeless. The largest counterbalance to the drag is that you wouldn't have to carry oxygen along with you if you accelerated within the atmosphere.

So much for qualitative issues. What about the numbers? Well (still qualitative, actually) the numbers indicate that you can't get going fast enough at an altitude where there's enough air to use with fuel - at least, not enough that it's worth the weight of including airbreathing propulsion systems that aren't going to work for most of the way. An SR-71 carrying a rocket on its back is not as cost-effective as adding a few (thousand) more pounds of fuel for the rockets you need anyway.

However, that's an engineering problem, not a physics problem, and I have a lot of faith in engineers. When they figure out how to make a SCRAMJET (Supersonic Combustion RAM JET) work, they'll be able to get a space plane up a useful point on something like the current launch profile (speed versus altitude) using air breathing propulsion. An example would be Mach 10 at about 150,000 feet (faster/draggier at that altitude than the Shuttle, but still useful). Once they get to that point, you'll see rolling takeoffs and things like the old movies promised us (probably not the flying cars, though).

Best answer of all, though, is to keep NASA out of it. Let out commercial bids to supply the ISS with material and personnel. I'll bet you find some creative solutions if they don't have to feed the NASA bureaucracy.

You are correct, the drag from the horizontal positioning of this system is the major downside of the design. However, this is counterbalanced by the concept affording the delivery of externally supplied power (through the electromagnetic rail system) all the way up to the moment where the payload leaves the rails. Once released, perhaps that might be a good time to engage a scramjet for the minute or so it takes to exit the atmosphere. Either that, or just fire rockets, or simply carry on with the momentum delivered by the launch system if it is enough to do the job.

Anyway, I'm no rocket scientist, just a guy who likes old sci-fi movies.

I've read a troubling financial analysis of this OSP concept by Rand Simberg. The upshot of this analysis is that if they can't hold development costs down for the OSP then it will cost at least as much as the shuttle per flight. They keep spouting ten years and 12 billion dollars for development of this and it will give us less capability than the shuttle with increased costs.

See post 5:

NASA Sets Initial Requirements for Orbital Space Plane System

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