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That sounds very interesting and cool. But the lower-tech approach in the original article sounds radically more practical in real terms than either drones or l

That sounds very interesting and cool. But the lower-tech approach in the original article sounds radically more practical in real terms than either drones or liquid-hydrogen-powered ramjets ;-)

namibj 8y ago
This was the general medicine-remote-island-delivery approach ;). The LH2 ramjet could probably be made to launch from a <100m long catapult, I once did a few calculations and UHMWPE fibers should allow accelerating within iirc. 50m to Mach 0.7 with something like a large (half-ton, due to the energy density) steel coil spring (like in a watch, just a "little" larger) at the muzzle and that coiling up the rope pulling an iirc. 100 kg aircraft with a sled or so, due to the ramjet not delivering enough thrust at lower speeds. The side effect would be that because they gain thrust with speed (up to a point, for the LH2 constellation somewhere over Mach 3), there would be plenty of thrust to spare, and combined with the high structural strength necessary for the catapult, and the lack of vertebrae on board, turns up to about 30~50 G are feasible, all at near ground level. While there is certainly an appeal to this, and the technology being sufficiently low-tech for a home shop (I am just going to refer to Sam Zeloof's garage wafer fab), any attempts at building something like it as a large hobby project would be futile for there being no way to test it outside of a remote desert area or the ocean, both rather inhospitable to a one-man flight crew. There are reasons supersonic aircraft are not tested over inhabitation. It would not be nice to a street it could technically fly through, unless the buildings are already blast proof. And a hobby project of that scale you can't even play with will not be worth it. (If you happen to know how to play with something like this despite the supersonic-over-land ban, please divulge your secret.)

That sounds very interesting and cool. But the lower-tech approach in the original article sounds radically more practical in real terms than either drones or liquid-hydrogen-powered ramjets ;-)

namibj 8y ago

This was the general medicine-remote-island-delivery approach ;). The LH2 ramjet could probably be made to launch from a <100m long catapult, I once did a few calculations and UHMWPE fibers should allow accelerating within iirc. 50m to Mach 0.7 with something like a large (half-ton, due to the energy density) steel coil spring (like in a watch, just a "little" larger) at the muzzle and that coiling up the rope pulling an iirc. 100 kg aircraft with a sled or so, due to the ramjet not delivering enough thrust at lower speeds. The side effect would be that because they gain thrust with speed (up to a point, for the LH2 constellation somewhere over Mach 3), there would be plenty of thrust to spare, and combined with the high structural strength necessary for the catapult, and the lack of vertebrae on board, turns up to about 30~50 G are feasible, all at near ground level. While there is certainly an appeal to this, and the technology being sufficiently low-tech for a home shop (I am just going to refer to Sam Zeloof's garage wafer fab), any attempts at building something like it as a large hobby project would be futile for there being no way to test it outside of a remote desert area or the ocean, both rather inhospitable to a one-man flight crew. There are reasons supersonic aircraft are not tested over inhabitation. It would not be nice to a street it could technically fly through, unless the buildings are already blast proof. And a hobby project of that scale you can't even play with will not be worth it. (If you happen to know how to play with something like this despite the supersonic-over-land ban, please divulge your secret.)