The coming close approach with Mars (closest in 50,000 years) has focused attention on Mars exploration. There are two American space probes, spirit and opportunity, en route; as well as a British Beagle-2 probe carried by the ESA's Mars Express and the troubled Japanese Nozumi orbiter. While the NASA probes were launched early this summer with little hassle, the American Space Agency is in deep trouble. The Columbia disaster has grounded the space shuttle fleet, and there seems little doubt that the Columbia Accident Investigation Board will say that the shuttle cannot be flown for much longer. Optimistic NASA estimates that the Shuttle could be flown into the 2030's now seem fantastical.
While more scientific missions to Mars will bring a welcome increase in our scientific knowledge, they do not in any way advance our presence in space. Launched on disposable vehicles whose design histories reach back before the dawn of the space age, the American Mars probes are holdovers from the past. The future of space exploration, if there is to be one, lies with two developments. Truly reusable launch vehicles and heavy lift launchers. I have talked about reusable launch vehicles before here, and they would be crucial in any effort to develop a permanent foothold in Earth orbit, or on the moon. They would be the SUVs of space; reliable, capable of hauling people and small amounts of cargo, and basically travelling back and forth between the Earth and orbital facilities. They would allow us to get people into and back from space cheaply and safely. As such, they should be at the very top of NASA's list for things to do. (That they are not, is criminal.)
[Update] The Russians are designing a nuclear power station for Mars. They apparently have all the design work completed, but trouble looms on the horizon:
"The only stumbling block is how to deliver ready-made building blocks to a construction site 300 million kilometres (186.4 million miles) away from Earth."
That does present a problem, don't it? The solution to this problem is in the rest of this article:
But they are not all that we need. The primary justification for building the shuttle can be seen in the name of the vehicle itself - shuttle. The Space Shuttle was intended as a space bus to allow astronauts to go to a space station and back to earth. Of course, the first space station died before the shuttle started flying, and it took another twenty years to build the second one using the shuttle. Just as the shuttle was not the ideal vehicle for space construction (the size of the shuttle cargo bay imposed numerous constraints on the design of the ISS), a reusable launch vehicle like the DC-X would not be well suited for creating an orbital infrastructure.
To build in space, we don't need a bus, we need a big honking dump truck. Happily, we have most of the pieces already designed and tested. While it might be a good idea to stop flying the shuttle, there is no reason to dispose of the rest of the shuttle system. When you think about it a little, it becomes obvious. The solid rocket boosters, external tank and shuttle orbiter comprise the what NASA calls the Space Transportation System. The STS can put over twenty five tons of cargo into low earth orbit. All well and good. But - the whole shuttle orbiter goes up in orbit as well. Properly considered, the entire orbiter is payload. So, why not get rid of the orbiter?
The shuttle orbiter weighs about 175,000 lbs. Add in the orbiter's payload capacity of 55,000 lbs, and you get 230,000 lbs, or 115 tons. That's a lot of mass. There are two ways to go about disposing of the orbiter in order to create a heavy lift system. The simplest would be to create a dummy orbiter. In a dummy orbiter, the three main engines at the bottom, and all the pumping arrangements to get the fuel from the external tank would be identical to the systems in the orbiter. But the rest of the vehicle would be a light weight shell designed to hold and protect the payload during liftoff. The major advantage of this idea is that it would require no redesign or modification of the other parts of the system.
The dummy orbiter could be designed by a few guys from Lockheed over a long weekend, if we gave them enough pizza and mountain dew. If we wanted to be clever about it, we would design the cargo shell so that it could be immediately transformed into habitable living space - make it airtight, include conduits, airlocks and what have you. Once in orbit, you move the payload out, and then retrofit the space for whatever you need it for.
A more ambitious scheme would involve heavily modifying the external tank. Rather than having the shuttle orbiter with its three main engines, the engines would be moved to the bottom of the external tank, more like a conventional rocket. Atop the external tank would be the cargo module, just like with a ordinary disposable rocket. The real advantage of this change would be that you could easily allow for more solid rocket boosters. Each pair of boosters would increase the thrust of the STS stack by six and a half million pounds of thrust. This would allow truly large amounts of cargo to be lifted into orbit.
(And, while you're redesigning the ET, you can make it easiily convertible to hab space as well. Seeing as the ET is 150 feet long and 30 across, that's a lot of space for free, everytime you launch. Of course, we should have been doing that for the last twenty years. Aargh.)
What it boils down to is that for very little money, and very little time, we can have a heavy lift system that can launch as much into orbit as the old Saturn could. We just need to ditch the orbiter. With that kind of lift capacity, we could easily launch the material needed for a human crewed Mars mission, a lunar base, large orbital telescopes, or an expanded space station.
There are already assembly lines for the external tanks, and for the SRBs. While the shuttle engines would not be reusable in this configuration (unless they were somehow brought back to earth, for example by returning shuttles) they could be reused in space for other purposes, such as earth to moon shuttles, or even for lunar landers. The possibilities are endless, once you have the capability to rapidly move large quantities of mass into orbit