It sounds interesting--but the article does not go into much detail about the specifics of this ion thruster. Ion thrusters traditionally are able to achieve anywhere from 10000 sec to 100000 seconds of specific impulse, but their thrust levels are all very small: typically no more than a few millinewtons to about 0.1 newton of thrust. The largest and most powerful units are capable of nearly 1 Newton.

I am intruiged by the invention of a former astronaut and multiflight shuttle veteran Dr. Chang Diaz: the VASIMR or Variable Specific Imulse Magneto plasma Rocket. The VASIMR engine is unique in that it uses high power RF (radio frequency) to induce ionization and ohmic heating in a plasma which is then accelerated by thermal excitations alone along a path confined by magnetic fields generated by superconducting coils. The actual nozzle throat is a partial magnetic 'mirror' and the nozzle is formed by additional coils shaping the magnetic field into a de Levaal nozzle shape. This kind of engine is capable of a higher thrust, low Isp mode which could generate hundreds of newtons of thrust at something about 1000 seconds of Isp. While for cruise, the engine is switched to its higher power mode which generates less thrust, but much higher exhaust velocities: nearly 15,000 seconds of Isp.

I think that ultimatly because the VASIMR does not have the 'space charge' limitation of conventional electrostatic ion thrusters, and with the adaptability in high and low power modes, and with potentially very flexible propellant feeds, for large applications such as manned deep space craft, I see VASIMR winning out over ion thrusters every time.

A nice brief on VASIMR is available at:
http://www.nasatech.com/Briefs/Sep01/MSC23041.html

A much more detailed and indepth paper is available online in PDF format at:
http://dma.ing.uniroma1.it/users/bruno/Petro.prn.pdf

I know its a little farther off topic--but Jaro, you found some good stuff there!

I skimmed over the nuclear aersopace plane a little too quick--I had done the search and post about a half hour before I had to leave for work--so I missed quite a bit of information there.

A nuclear aerospace plane makes a lot of sense. A conventional liquid hydrogen powered scramjet vehicle is a delicate balance of lift, drag, thrust and total available impulse. The most difficult thing is balancing these parameters so that a vehicle can actually fly and also perform a useful function (such as deliver payload.) It is difficult in the least to design something that can make the trip to orbit (which, as far as I know, has never been done!) and still carry a non-trivial payload--say atleast 10,000 kilograms. The best that modern technology has come up with is advanced graphite composite frames with a metalized-ceramic-graphite 'skin' and actively cooled metal matrix nosecaps and leading edges. These things have yet to be demonstrated as an integrated solution in the same vehicle.

Where nuclear power can really 'take off' as it were is in a vehicle that uses liquid hydrogen reaction mass and uses a nuclear thermal engine as an upper stage. A large vehicle has the advantage that enough hydrogen can be carried to provide adequate shielding from the reactor, presumably located in the tail. Such a vehicle could takeoff as a conventional aircraft, fly to a respectable 20,000 m altitude and accelerate to about Mach 2.5 before switching to full nuclear rocket power. The rocket engine will give the vehicle a steep 'climb out' of the atmosphere before pitching over in a synergic trajectory for a more tangential acceleration to orbital velocity.

My first impressions of such a vehicle makes me think that such a machine could be quite large on the ground--say somewhere near 600 metric tons fully fueled; it would be half again as long as a Boeing 747, say near 120 m; wingspan would be vairalbe (giant swing wing--swept 50m, extended near 110 m, ) it would probably burn around 300 metric tons of liquid hydrogen, and could deliver a substantial payload to orbit: say 50 to 100 metric tons to a 250 km high orbit. Even if the machine was smaller and only delivered 10 tons to lLow Earth Orbit, I think it would be worth building it. I definately think its worth crunching real numbers on it!

Well,

I think China has a good start, but they are still in their technological 'infancy' (I'm sure they would dispute this, but their Shenzhu spacecraft proves their intentions are space bound!) They have a lot of the basics, but the US didn't really begin exploring nuclear engines until after Project Mercury. Still, a lot of declassified data and information is available--the Chinese have proven themselves to be resourceful, crafty, and I fell confident the basic sophistication is there. But nuclear engines require prototypes to be built and tested, and tested and tested! This requires a lot of new infrastructure--which is where most of the expense of a research project is involved. Currently, I have not heard or read any evidence to convince me the Chinese are building the kinds of testing infrastructure needed for a dedicated nuclear engine R&D effort. Even the US lacks the basic facilities to test a full up nuke engine--so this shouldn't be too surprising. The critical thing for China would be integrating a nuclear thermal engine into an airframe capable of hypersonic flight--which is a bit more of a technological stretch for them. Not impossible, only very difficult. But well within the realm of possibility if they made a national effort to get it done.

Ditto for the Russians, although it would be likely that even now such an effort would remain mostly secret--they have a long history of announcing successes after they happen! I suspect that given the state of their defense infrastructure--I would imagine they have little money left for a nuclear engine R&D effort. That's not to say they don't possess the basic technical expertise and know how to do it--only the money and the national will are lacking. I think integrating a nuclear prop system with an airframe may be more manageable to for them--but it still would require a substantial national effort.

ESA could do it, I think--I'm certain they have all of the necessary ingredients involving the full spectrum of technologies needed to support a successful R&D effort--they just need a "European National Directive" or something like that to make it a fiscal priority.

Japan could probably also do it--although their technical problems with several of their nuclear fascilities seems to indicate an underfunded or understaffed nuclear infrastructure. Still, if the national will crystalized, I feel confident the Japanese could accomplish a successful nuclear aerospace plane.

India has expressed its long term intentions of also achieving a manned space program, and have also expressed intentions to build space stations and go to the moon. However, they are about where the US was in 1950: still an awful lot of work needs to be done, but they are off to a good start. With luck, they can avoid some of the pitfuls and ruts that the US has fallen into. I wish them the best of luck!