Scramjet Rail-Gun


Rev Up The Rail Gun
A 240,000-horsepower linear motor converts 180 megawatts into an electromagnetic force that propels a scramjet carrying a spacecraft down a two-mile-long track. The craft accelerates from 0 to 1,100 mph (Mach 1.5) in under 60 seconds— fast, but at less than 3 Gs, safe for manned flight.

Fire The Scramjet

Get Into Orbit

Stick The Landing

24 hours! Hahahahahaha! They said that about the Shuttle, too... Still, what's not to love about maglev scramjets? It's even fun to say!


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6 Responses:

  1. LunaticSX says:

    I didn't know Yoyodyne Propulsion Systems was a NASA sub-contractor.

  2. cthulhu says:

    Going that fast low in the atmosphere is a big waste of energy - huge drag and aerodynamic heating problems.

    • Nick Lamb says:

      But the nice thing about "that low" (on the ground) is energy is so cheap here you can waste it. 5MJ of energy on the ground costs almost nothing. 5kJ of energy 2km up is really expensive, you will probably have to bring it with you. So even if it's really inefficient energy-wise it may be a cost saving to put lots of kinetic energy in at ground level.

    • Adam says:

      Mach 1.5 is fast and wasteful in the low atmosphere, but it will just trade speed for altitude. You don't have to go very high to be above the majority of the atmosphere. In minutes, it can be above 80% of the atmosphere, and it's not going to be much more wasteful than, say, a supersonic bomber. That's are expensive compared to jet airliners, but it's very cheap compared to the cost of launching a large rocket into orbit.

      Even if it does waste energy by going fast in low atmosphere, that's a very very small amount of waste compared to the win you get by using atmospheric oxygen. A very large percentage of the fuel used by normal rockets is simply used to lift the rest of the fuel. For the space shuttle to lift an extra 1 lb of payload takes something like 4 extra lbs of fuel. Around half of that fuel is oxygen. The weight savings for using oxygen from the atmosphere are dramatic. Being able to get your second stage 37 miles up going half the necessary orbital speed using only atmospheric oxygen would be huge.

  3. Jeffrey McBeth says:

    When that rocket separates from the scramjet, it is still less than half way to orbital speed. You need about 70% less fuel to complete boosting to LEO too.

    • mentallill says:

      But "less than half-way" means less than a quarter of the kinetic energy. If takeoff is at Mach 1.5, and the end of atmospheric propulsion at Mach 10, only 2% of the energy comes from the rail gun part.

      It sounds an awful lot to me like the idea was to skip the turbojet part entirely, going straight from the rail gun to scramjet flight, but that didn't work, so they put it back in. It's probably easier to optimize the turbojets for working in the mach 1.5-4 range rather than starting them out at zero, but it's still a rocket on a scramjet on a turbojet on a railgun car, and the railgun part is the equivalent of the turducken's pigeon.