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A while back I had the ultimate Idea, one that would give us mars without the been there done that syndrome. A reusable orbital transfer vehicle, mad for Mars-Earth payloads.The Vehicle would be modular, any part that needs replacement could be replaced quickly. The vehicle would look like a long scaffold tower, At the very back there would be the propulsion unit. This would be a high ISP rocket, perhaps Ion, GNCR, etc. The tower would then stretch far to the Nuclear Reactor, which again could be replaced if needed. The space in between would be a modular space for Fuel tans, the Loading station would be plenty long and fuel tanks could be added for extra payloads and the like. In front of another tower would be general storage(water, food, etc.), a cylinder with four stationing points, which could be loaded with the needed supplies. connected on front would be a Spinning artificial gravity wheel where the crew would live, and work etc. in front of that in the center, would be the docking port for all sorts of Spacecraft; Mars landers; etc. In front of that at the very front would be the heavy payload, if the mission was just a landing, then It might have nothing and not need as much fuel tanks aft, but the front could contain small bases, Space Stations and such.
When in orbit around earth or Mars it could act as a space station, and if it had a 20-30 year life which nuclear power could Give IMHO, hen it could to many mars missions.
Granted this idea is still a concept, but what do you think?
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I agree that it would be best to have a reusable spacecraft to take people from LEO to LMO and back. The concept has many advantages:
*It is reusable.
*It does not waste fuel by sending an interplanetary spacecraft to a planet's surface.
*The requirements for interplanetary spaceflight are very different from atmospheric flight. This way it is not necessary to make a spacecraft that can do both.
*The spacecraft could visit many other places besides Mars, such as asteroids, Venus, and or Mars' moons. This would both increase the amount of useful work the spacecraft could do, and give scientifically interesting intermediate missions to test the craft before attempting Mars.
*The mission architecture is modular. The Earth launcher/lander, Mars launcher/lander, and the interplanetary spacecraft can all be upgraded independently as replacements become available.
There are many different options for the actual layout of the spacecraft. My advice is to try and keep it as small as possible. Just because we could build battlestar galactica, doesn?t mean that you can get Congress to approve it.
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I suppose the main concern I have is that something long and thin can't be aerobraked, so you have to haul along a lot more fuel. That won't be the case if we have an advanced propulsion system with a very high Isp, but that's a half century or so away.
One possibility would be to design the cargo and human portions to detach and aerobrake separately, with the engine and fuel tanks using propulsion to go into orbit.
-- RobS
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Would it be possible to flip the craft around and use it's main engines for decelleration, a la Apollo? even if it took an hour that is still not much on interplanetary flight.
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Of course, that's easy, but you have to launch the fuel you will burn to slow the ship down, and then you ave to launch the fuel that will accelerate the fuel to Mars, and pretty soon your ship becomes so enormous it isn't practical.
-- RobS
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A reuseable high-ISP (and high thrust for manned) ship is absolutely the only way to get anything besides small science teams to Mars. Keep in mind with such a design though, that the truss itself adds weight, and the long it is the stronger (and heavier) per-length it must be to handle maneuvering torque. The advantages of large "hardpoint" size and lower radiation dose (with the reactor/NTR being far away) should be weighed against the size of payloads you intend to send and how much a thicker radiation shield would weigh. Payloads are generally not all that big compared to fuel tankage either.
Since most of the high-Isp engine concepts, except ion drives, involve the use of hydrogen as a fuel, the fuel tanks are going to be fairly large. The tank itself should be integrated with the ship design too, and you might even connect your payloads to it and save on structure. With the manned section on the opposit end from the reactor/NTR you could use the hydrogen itself as a partial radiation shield maybe.
A more compact ship would be easier to aerobrake too, since the longer it is the wider the shield has to be to prevent the super-high-temp "wake" from scorching the back end of your rocket... Maybe another good reason to persue propulsive capture with a nuclear engine.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
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In a mission that uses an electric, low-thrust drive, the reusable transfer spacecraft and the lander would probably separate just prior to reaching Mars. The lander would aerobrake and make either a direct entry or aerocapture into Mars orbit and then de-orbit. The transfer ship would thrust its engines opposite the direction of motion and slowly brake into Mars orbit over the course of weeks. I doubt that a fragile ship designed to operate in weightlessness like our Mars transfer vehicle would be able to survive aerocapture.
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