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SpaceX Unveils Heavy-Lift Rocket Designs
FleaPlus writes "At the recent Joint Propulsion Conference, SpaceX's rocket development facility director Tom Markusic unveiled conceptual plans for how its current Falcon 1 and Falcon 9 commercial rockets can be evolved into heavy-lift rockets, ranging from a Falcon X capable of lifting 38,000kg to orbit, up to a 140,000kg Falcon XX (more than either the Saturn V or the 75,000kg shuttle-derived rocket Congress currently plans on having NASA spend >$13B building). SpaceX presentations also discuss a new Merlin 2 heavy-lift engine, solar-electric cargo tugs, adapting their current engines for descent/ascent vehicles fueled by Mars-derived methane, and a desire for the government to take the lead on in-space nuclear thermal propulsion while commercial focuses on launchers. In a recent interview, SpaceX CEO/CTO Elon Musk expressed his goal of lowering the price of Mars transportation enough to enable early colonization in 20 years, and his own plans for retiring to Mars."
I like nuclear thermal as much as the next /.er, but is there really any point in thermal rockets beyond attaining orbit?
For one thing there's the slight problem that you die during the transit through the Van Allen belts if you don't have a high-thrust engine or very large radiation shields.
And nuclear thermal rockets kind of suck ass for attaining orbit since you have to ensure that they land somewhere safe if they fail during launch; NASA's test plans for the early models involved polar launch where the flight path was designed to dump it in Antarctica or a remote part of the ocean if something went wrong.
As 0123456 indicated, there are both a need for high thrust engines in space and huge risks with the use of nuclear-anything propulsion on Earth. In addition to passage through the Van Allen belts, we also need to consider the Oberth effect. When you're trying to leave a gravity well (such as Earth's), then thrust deep in the well has a higher effective ISP than equivalent thrust higher up the well.
Second, because of the risks of operating nuclear rockets in Earth's biosphere, it makes sense, that if you're eventually going to have a nuclear powered rocket to orbit, that you try it somewhere else first and generate a reliability record. Space is the "somewhere else".