There is no shortage of proposals for radically innovative space launch schemes that, if they worked, would get us across the valley to other hilltops considerably higher than the one we are standing on now—high enough to bring the cost and risk of space launch down to the point where fundamentally new things could begin happening in outer space.
This is plainly not true. I know of only three alternative schemes that might be viable, and when you look at what they are and what their caveats are, it becomes obvious why we’re stuck on chemical rockets.
Then there’s space elevators, which would require a major breakthrough in materials science, and might still be impossible even then.
Then there’s the Orion spacecraft design—that is, an extremely large ship propelled by launching nuclear bombs out the back to ablate a shield on a spring. In addition to the political problems, it’s also extremely inflexible (it has to be huge or it doesn’t work), hard to iterate on (for the same reason), and environmentally damaging (as in “would cause human deaths”, not to be confused with the more common “would anger irrational activists”).
Finally, there’s the space gun idea (as envisioned by Quicklaunch): a wide, neutrally buoyant gun barrel extending from the ocean surface to the sea floor. Unfortunately, the calculations I’ve seen indicate that the acceleration will be too high for humans, and it still needs a second stage rocket (for fine-tuning its orbit, if nothing else). So, even if this were built, we’d still need rockets for launching humans, and possibly also for launching equipment too large for the barrel diameter. I think this one should be pursued, but it’s no historical accident that rockets came first.
I agree, though, that unless ATO works out, chemical rockets are probably just about the best and safest technology we are likely to find for launch from earth.
But if Less Wrong ever undertakes some kind of collective brainpower exercise as an experiment, I’d love to see whether the smart people here can figure out how or whether the ATO idea might work. There is some weird stuff that happens when the atmosphere gets thin enough so that the mean free path becomes comparable to the scale height and the airship dimensions become comparable to both.
This is plainly not true. I know of only three alternative schemes that might be viable, and when you look at what they are and what their caveats are, it becomes obvious why we’re stuck on chemical rockets.
Then there’s space elevators, which would require a major breakthrough in materials science, and might still be impossible even then.
Then there’s the Orion spacecraft design—that is, an extremely large ship propelled by launching nuclear bombs out the back to ablate a shield on a spring. In addition to the political problems, it’s also extremely inflexible (it has to be huge or it doesn’t work), hard to iterate on (for the same reason), and environmentally damaging (as in “would cause human deaths”, not to be confused with the more common “would anger irrational activists”).
Finally, there’s the space gun idea (as envisioned by Quicklaunch): a wide, neutrally buoyant gun barrel extending from the ocean surface to the sea floor. Unfortunately, the calculations I’ve seen indicate that the acceleration will be too high for humans, and it still needs a second stage rocket (for fine-tuning its orbit, if nothing else). So, even if this were built, we’d still need rockets for launching humans, and possibly also for launching equipment too large for the barrel diameter. I think this one should be pursued, but it’s no historical accident that rockets came first.
Two other technologies that might play a role are Airship to Orbit from J.P. Aerospace, and the space tethers ideas of Robert Forward’s company.
I agree, though, that unless ATO works out, chemical rockets are probably just about the best and safest technology we are likely to find for launch from earth.
But if Less Wrong ever undertakes some kind of collective brainpower exercise as an experiment, I’d love to see whether the smart people here can figure out how or whether the ATO idea might work. There is some weird stuff that happens when the atmosphere gets thin enough so that the mean free path becomes comparable to the scale height and the airship dimensions become comparable to both.
Wikipedia link with more ideas: Non-rocket spacelaunch. I like the idea of building a tower of balloons :-)