VASIMR Plasma Thruster To Be Tested Aboard ISS

Toren Altair brings news that NASA and the Ad Astra Rocket Company finalized a Space Act Agreement earlier this week to test the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) on the International Space Station. The agreement hinges on a series of requirements for the thruster's performance and efficiency in ground-based tests. "The primary technical objective of the project is to operate the VASIMR VF-200 engine at power levels up to 200 kW. Engine operation will be restricted to pulses of up to 10 minutes at this power level. Energy for these high-power operations will be provided by a battery system trickle-charged by the ISS power system. These tests will mark the first time that a high-power, steady-state electric thruster will be used as part of a manned spacecraft." Reader clarkes1 points out related news of a runway trial for Virgin Galactic's WhiteKnightTwo, the mothership that is designed to carry SpaceShipTwo from the ground to 50,000 feet. A very brief video shows the oddly-shaped plane moving down a runway under its own power.

Comments

Re:white knight 2 looks too fragile

[Nyeerrmm]

Actually, on any airplane, the wing has to be able to support the full mass of the aircraft, albeit spread over the entire surface of the wing. If you think about it, it has to have the aerodynamic pressure be at least equal to the mass of the aircraft. And then all that load gets transferred to the spars, so on a normal single-wing aircraft, the central spar is carrying the entire aircraft mass, if its the type of design that carries through the middle of the aircraft.

Also, in order to strengthen it to support the weight of SpaceShipTwo, you can do it without any visible change, just make the spars in the wing heftier.

As far as having to make it look cool, of course they do... its supposed to appeal to people who want to spend $200k going to (suborbital) space. And given that the methods to check the structural soundness of such a set-up are well established, and that Rutan isn't an idiot, I'd imagine it can handle worst case scenario loads with a safety factor of 1.2 or 1.3, as is common for any aerospace application.

Re:Launch from altitude vs near equator

[Deadstick]

As far as satellite launching is concerned, the height of the launch site is utterly trivial. In order to achieve a low earth orbit, you have to accelerate an object to about 23,000 feet per second; for a one-pound object, that will take over 8 million foot-pounds of energy. Lifting that same object from sea level to the top of Mt. Everest will take 29,029 foot-pounds.

The latitude of the launch site offers some tradeoffs. A site on the equator will give you a few hundred extra feet per second than one at 45 degrees latitude, not a real big advantage. However, a launch directly into orbit will always put you in an orbit whose inclination is at least the latitude of the launch site. Launch from Cape Canaveral, and you'll be in an orbit inclined at least 28 degrees from the equator. You can make it higher, but not lower. If you want to get an equatorial orbit -- which most communications birds need -- you have to launch into the inclined orbit first, fly to the equatorial plane, and then make a "plane change" maneuver which takes a substantial fraction of the energy it took to put you in orbit. From the equator, you can launch directly into any inclination, which is why the European Space Agency birds come out of French Guiana.

rj