Wed 10 Dec, 2003 06:41 am
Unless we get CATS = cheap acess to space, an international hotel on Mars is likely more than a century in our future. With extreme CATS it could happen in a decade.
The space elevator fans may be disappointed. Success depends on the CNT = carbon nano tubes really being 40 times stronger than kevar by gross weight in actual space applications. Some of the support technology is still on the drawing boards, so some of what we think will work, will require alternatives.
I just learned of a space craft design by Robert Winglee. Analog Science Fiction and Fact January/february 2004 issue page 40. It releases a few kilograms of almost any kind of gas or vapor into space and has a strong magnetic field like the Magsail. The extremely thin cloud acts like a sail with the solar wind. It could be launched from the end of the space elevator and pass Mars going 50 kmps = 180,000 KMPS = 100,000 mph, and continue accelerating all the way to the heliopause, about 80 AU from Earth according to optimistic projections. The projected ISP is over 20,000, far better than any other propulsion system likely this decade. Does anyone have a link to more details, such as why a test flight can't happen in 2004, how strong the magnetic field needs to be? Is auxiliary power needed to go any direction other than down wind?
The prototype is expected to use less than two kilowatts to produce more than one newton of thrust, up to 32 times the thrust with less electricity and less ejection mass than the recently tested deep space ion engine which produced 0.092 newtons of thrust. Neil
Sorry Neil, you are a few steps ahead of me there. What you are discussing is viable interstellar travel. I'm more interested in the space elevator. If we had a world program to build it, (taking into account developments in materials technology), not only could we have holidays on Mars, but we could get rid of all the high level nuclear waste, expand nuclear power and save the Earth.
I'm excited about the space elevator also. Magnetospheric Plasma propulsion = M2P2 should be useful as a supplemental engine in the inner solar system as it can run continously for months without refueling. Manned space craft should have one or more back up propulsion systems.
A scaled up model might get to Centauri Proxima in 1600 years if it can refuel enroute. It's practical limit is likely not much past the solar pause, about 80 AU from the Sun = 7 or 8 billion miles. Traveling toward the Sun it can prevent excessive speed by braking. Neil
What about a nuclear heat exchange engine? We made one in the 50s, so we should certainly be able to make one today. That might be the next logical step in propulsion systems. I hope we won't rely on chemical propulsion too much longer.
It is my understanding that a nuclear engine was ground tested rather thoughly in the 1960s. It had about ten times the ISP of the best chemical rockets. It was made of mostly graphite = carbon and enriched uranium. It heated hydrogen gas to more than 1000 degrees c = 1832 degrees f and could likely be made to operate even hotter thus increasing the ISP. It could likely be combined with an ion engine or M2P2 for still better performance. There were significant radio-active isotopes in it's exhaust so it was not suitable for operation in Earth's atmosphere, but could likely be operated the rest of the way to Mars and on the surface of Mars at reduced power to supply abundant heat and electricity. It would need to be scaled up for a 6 month manned trip to Mars. It might even be functional for lift off from Mars and the return trip to Earth. It was discontinued because of the nuclear test ban, could likely be reactivated, but has not been space tested. Only the space elevator looks more promising. Neil