Space Tourist Trips To the Moon May Fly On Recycled Spaceships 95
thomst writes "Rob Coppinger of Space.com reports that UK-based private company Excalibur Almaz plans to offer commercial lunar-orbital tourist missions based on recycled Soviet-era Soyuz vehicle and Salyut space stations, using Hall Effect thrusters to power the ensemble from Earth orbit to the Moon and back. The company estimates ticket prices at $150 million per seat (with a 50% profit margin), and expects to sell about 30 of them. Excalibur Almaz has other big plans, too, including ISS crew transport, Lagrange Point scientific missions, and Lunar surface payload deliveries. It expects to launch its first tourist trip to the Moon in 2014."
Hall effect thrusters? (Score:4, Informative)
For those unfamiliar with the tradeoffs: Hall effect thrusters make fairly efficient use of the reaction mass - about 2000s, compared to ~250 for solid rockets or ~300-400 for liquid rockets. That means a considerable increase in your delta-v - since you only need 10-20% as much reaction mass for the same impulse, you get 5-10x more delta-v. Great, right?
The trouble is that you need a power source. Liquid fuel rockets just burn the propellant. Hall effect thrusters (and other ion thrusters) need a power source in addition to the propellant.
This is a great tradeoff for stationkeeping on satellites - you only need tiny amounts of thrust, so you can easily generate enough power using solar cells or a RTG. Thus the very efficient use of reaction mass means a much longer useful life, or more useful payload in your satellite for a given launch mass, etc. It's just plain more efficient.
But this isn't like that. They seem to want to use them to perform the Hohmann tranfer [wikipedia.org]. That means having a very high thrust for a short duration - not just because you want to get there more quickly, but because it's much more efficient than a long continuous burn.
They're talking about 100KW. That seems low. Ballpark 5000 newtons of thrust... Compare to the Apollo command/service module at ~90,000 newtons. Thus they'll need a fairly long burn at that power. How the heck are they generate that kind of power for a long duration?