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NASA Looks At Railgun-Like Rocket Launcher
coondoggie writes "NASA is looking hard at a way to blast spacecraft horizontally down an electrified track or gas-powered sled and into space, hitting speeds of about Mach 10. The craft would then return and land on a runway by the launch site."
Well, I believe this critter was up and at it in the 70's at Princeton: http://en.wikipedia.org/wiki/Gerard_K._O'Neill
Schroedinger's Brexit: The UK is both in and out of the EU at the same time!
Sorry, but 10x roller coaster speeds isn't close to Mach 10.
NASA is on to something interesting here. It would seem that MagLev is required (no wheels can handle that speed), and it would be interesting to see what kind of acceleration they can get out of LIM's. Rocket propulsion seems a waste in this application. It might help bullet-train technology, and we can get some new spin-off inventions from NASA.
I need trepanation like I need a hole in the head.
You're being facetious, but that's exactly what would happen.
General Relativity: Space-time tells matter where to go; Matter tells space-time what shape to be.
Once ignited, Mach 10 wouldn't be outrageous for a Scramjet.
Well, that seems a bit optimistic for a device that has been successfully flown, what, twice? Its kind of like planning the Boeing 777 the day after the wright brothers first flight.
The real killer with all these "hybrid" lifter designs is they are all ignorant of the virtually unknown 666 rule.
The 666 rule is that Mach 6 (which is tricky for an air breathing aircraft) at 60000 feet (again, tricky) is a whopping 6% of the way to orbit.
So, if, in your wildest dreams, you can simultaneously achieve mach 6 at 60Kft, which would be quite the noteworthy achievement, you've still got 94% of the way to go.
Alternately, you could take the required second stage, and make the fuel tank at least 6% bigger and skip all this air breathing foolishness.
"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
IIRC he's generally credited with the concept of communications satellites
Nope. That was Arthur C. Clarke, another of the grand masters of hard science-fiction.
The higher the technology, the sharper that two-edged sword.
before gravity takes control.
As the GP said, gravity is a conservative force. It is ALWAYS in control. Right now, gravity from distance stars is pulling us in their direction--the force is infinitestimal but present nonetheless. It is an extreme colloquialism to say that when you throw a ball up in the air gravity "takes control" when it starts to fall down, never mind that gravity caused the slowing of its ascent as well. Same as in orbits.
"Coasting into orbit," in your colloquial usage, simply means cutting the engines at a lower altitude than the final orbital altitude. To pull it off, you have to be going faster than orbital velocity at the lower altitude so that after your engine is cut off, some of your kinetic energy is transferred to potential energy, and you slow down while still going up until you reach the final orbit. This is no doubt used for small portions of most flights. But the GP's point is correct; anyone who understands Newtonian physics will be able to tell whether and what orbit you will reach once you cut your engines, thus no one ever bothers to talk about "coasting".
The only difference with a railgun-only launch system is you reach the maximum velocity at ground level and spend the *entire* trip to orbit "coasting." This is not what NASA is proposing. They will use the railgun only as the first stage, followed by scramjets and an orbital-insertion rocket engine, which is a much more realistic proposal.
When you cut off your engines, you *are* in orbit. There is no "final" orbit to go to from there. The only question is, does your orbit intersect the Earth or not :-)