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NASA engineers are developing a radical new form of launch that begins aboard an electrified track similar to that of a rollercoaster.  (Source: NASA)

The sled would then fling a scramjet into the air, which would activate and rocket to the upper atmosphere. Once in the upper atmosphere, the scramjet would fire a capsule launch vehicle into space as the final step.  (Source: NASA/Artist concept)
New launch system could be used for manned launches and satellite launches

NASA's budget may be cut, but that hasn't stopped the first international organization to put a man on the Moon from dreaming big.  One key question the agency is looking at is what the next big thing in space propulsion will be.  NASA and foreign space agencies have examined plasma enginesion enginesnuclear-powered designs, and solar sails, but these technologies lack the impulse and thrust to accelerate a launch vehicle into orbit. 

However, NASA's latest proposal may be the most creative idea of them all and has the potential to be relatively affordable.  The new proposal starts by placing a sled on electric tracks -- NASA's sled needs to reach a whopping 600 mph (appr. 1,000 km/h).

At the end of the track, the passenger vehicle, which rests atop the sled, will be flung off, launching at extreme speed.  The passenger vehicle would be a wedge-shaped aircraft, with scramjets aboard, which would activate upon launch.  Those scramjets would accelerate the aircraft to Mach 10.

Wings would gradually angle the craft into the Earth's upper atmosphere.  At the boundaries of the Earth's atmosphere, the scramjet would fire the actual spacecraft -- a capsule.  The maneuver would be akin to firing a round out of a barrel

By using mechanical motion to launch the craft, instead of expensive chemical boosters, the cost of launches could dramatically decrease.

NASA's Stan Starr, branch chief of the Applied Physics Laboratory at Florida's Kennedy Space Center, says the technology to achieve this type of launch isn't that far away.  In a released statement, he explains, "All of these are technology components that have already been developed or studied.  We're just proposing to mature these technologies to a useful level, well past the level they've already been taken.  Essentially you bring together parts of NASA that aren't usually brought together."

Engineers at NASA and the U.S. Air Force have worked on a variety of scramjet projects thus far, including the X-43A and X-51 (a missile design).  So far these programs have had a couple of successful launches and tests under their belt, raising hopes that the technology can soon be applied to projects like the launcher.

Mr. Starr and other NASA engineers have assembled a proposal to build the system, which they're dubbing the Advanced Space Launch System.  They're seeking grants from a variety of sources.

Under the plan Langley Research Center in Virginia, Glenn Research Center in Ohio, and Ames Research Center in California would build and test the parts of the hypersonic aircraft.  Dryden Research Center in California, Goddard Space Flight Center in Maryland and Marshall, along with the Kennedy Space Center would engineer the rail track.  The plan calls for an actual two-mile long test track to be laid down parallel to the crawlway that the Shuttle used to be transported along to Launch Pad 39A.  Mr. Starr comments, "I still see Kennedy's core role as a launch and landing facility."

The 10-year plan for the launch platform calls for the program to begin with launching small drones -- like those used by the Air Force -- into orbit.  This would be followed by satellite launches.  If all goes according to plan, the system could eventually be used for low-cost manned mission launches, as well.



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RE: Mass driver
By DanNeely on 9/15/2010 10:03:31 PM , Rating: 4
Yup. The scramjet will save a lot of fuel. It's the only realistic near future technology that can significantly reduce the cost of launching something into orbit.

Doing a back of the envelope calculation, a 1000m/s launch track + mach 10 scramjet will reduce the amount of fuel needed to reach mach10 by a factor of 2.2 allowing for either a much smaller total rocket or a much larger upper stage + payload combination. At mach 25 (slightly under orbital velocity of mach28.5) the ratio increases to 6.5:1. At mach 28.5 the ratio goes up to 8.3:1 but this would be undercut somewhat due to the need for a circularizing rocket burn once the ship reached space (otherwise it's in a ballistic missile type orbit and would reenter shortly after leaving the atmosphere).

As back of the envelope math these calculations ignore various fiddly bits that can significantly alter the final results. The relative mass of the ramjet vs conventional rocket module would be a major factor in where the actual numbers end up. For a real world example a large chunk of the higher performance of hydrogen rockets over kerosene or solid fuel rockets is lost because cryogenic hydrogen is bulky and the larger fuel tanks increase the parasitic mass of the rocket itself.

For anyone curious about my math, the rocket equation when solved for the mass ratio is:

m0/m1 = e^(deltav/g/Isp)

e = 2.71
g = 9.81m/s
Isp (kerosene rocket) = 350s
Isp (kerosene ramjet) = 1250s

deltaV (kerosene rocket) is 3400, 8500, or 9700m/s in the three cases above.

deltaV (kerosene ramjet) is 2400, 7500, or 8700m/s (remember the ramjet is leaving the launch track at 1000m/s).

Specific impulse (Isp) is a measure of how long 1kg of propellant can produce a thrust of 1g. Since only ~28.1% of the propellant in a kerosene rocket is kerosene (the remainder is oxygen) a ramjet, by getting its oxygen from the air, will have 3.56 as much kerosene per kg of propelant and be able to burn for 3.56x as long giving an Isp of 350*3.56 ~= 1250s.

PLugging the numbers above into the rocket equations gets mass ratios of 1.22, 1.84, and 2.03 for the scramjet vs 2.69, 11.88, and 16.86 for the conventional rocket. These numbers divided by each other are what I cited in the 2nd paragraph.

http://en.wikipedia.org/wiki/Tsiolkovsky_rocket_eq...
http://en.wikipedia.org/wiki/RP-1


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