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Launching from altitude gives you very little, so does spinlaunching. It is because it’s about speed, not altitude. Witch Spinlaunch, they plan to laumch aroun

Launching from altitude gives you very little, so does spinlaunching. It is because it’s about speed, not altitude. Witch Spinlaunch, they plan to laumch around 5000kmph, and you need a speed of around 25000kmph to reach orbit. In other words, they would need to use their setup to launch a rocket of a size of 1/2-3/4 of size of a falcon1 to get into orbit, and even then, unless they land the second stage, they will come out far more expensive than what SpaceX is doing. The tech may work on moon, but even on Moon a different solution - similar to maglev - may be better, bacause there would be no issues with crazy centrifugal forces. Anything launching from earth will require some sort of a rocket fuel (or some new laws of physics), because even if you managed to launch at the speed of 25000km/h from the ground, the payload would slow down before it left the atmosphere.

trhway 3y ago
>even if you managed to launch at the speed of 25000km/h from the ground, the payload would slow down before it left the atmosphere. Project HARP was shooting 16 inch artillery shells at 2100m/s, and they reached 180km altitude, i.e. the atmosphere was slowing it down only for 15%. While higher speeds cause higher losses, the larger payloads would benefit from decreasing surface-to-volume ratio, plus if one launches from say a plateau in Andes where atmosphere is aleady thinner, I think the losses will be similar for large payloads at speeds close to orbital.
- kolinko 3y ago
  Oh, nice, TIL. Good point about surface to volume ratio.
rcxdude 3y ago
Yeah, but isn't it also a lot about the tyranny of the rocket equation? The more speed you want the more mass of fuel you need to accelerate so the more fuel you need, etc. That means if you can start your ascent at even a relatively small fraction of the final speed you need the size of your rocket can shrink substantially.
- kolinko 3y ago
  Sure, but with a system like this you still need to build for reusability of a rocket - if not then even a smaller rocket will be more expensive than what SpaceX is planning to do with Starship. And if you're building a fully reusable rocket system, then neither size nor fuel matter as much as the simplicity and reliability of launch and landing. And here traditional rocket systems will win on Earth. On Mars or Moon, with less gravity and atmosphere these systems will be more feasible though since they can possibly launch into orbit without rocket boosters.

trhway 3y ago

>even if you managed to launch at the speed of 25000km/h from the ground, the payload would slow down before it left the atmosphere. Project HARP was shooting 16 inch artillery shells at 2100m/s, and they reached 180km altitude, i.e. the atmosphere was slowing it down only for 15%. While higher speeds cause higher losses, the larger payloads would benefit from decreasing surface-to-volume ratio, plus if one launches from say a plateau in Andes where atmosphere is aleady thinner, I think the losses will be similar for large payloads at speeds close to orbital.

kolinko 3y ago
Oh, nice, TIL. Good point about surface to volume ratio.

rcxdude 3y ago

Yeah, but isn't it also a lot about the tyranny of the rocket equation? The more speed you want the more mass of fuel you need to accelerate so the more fuel you need, etc. That means if you can start your ascent at even a relatively small fraction of the final speed you need the size of your rocket can shrink substantially.

kolinko 3y ago
Sure, but with a system like this you still need to build for reusability of a rocket - if not then even a smaller rocket will be more expensive than what SpaceX is planning to do with Starship. And if you're building a fully reusable rocket system, then neither size nor fuel matter as much as the simplicity and reliability of launch and landing. And here traditional rocket systems will win on Earth. On Mars or Moon, with less gravity and atmosphere these systems will be more feasible though since they can possibly launch into orbit without rocket boosters.