6 ms·

Accelerating in a huge vacuum chamber seems pretty difficult to achieve, and wouldn't there be a huge shock to the vehicle as it hits a wall of dense air? How

Accelerating in a huge vacuum chamber seems pretty difficult to achieve, and wouldn't there be a huge shock to the vehicle as it hits a wall of dense air? How much of a difference would a low pressure chamber make, I wonder? Maybe you could build the circular accelerator then a much longer exit pipe that runs up the side of a mountain. Although that sounds way, way easier said than done! But if your exit air pressure is roughly equal to your accelerator air pressure, then you don't need a fancy airlock system. The tether they proposed also seems a bit too much of the wishful thinking like "we just need a bundle of carbon nanotubes 1km long!" Wouldn't an electromagnetic accelerator work better?

MadnessASAP 2y ago
Well actually.... Even if you place the exit at higher altitude with lower pressure, without a seal you'll still end up with higher pressure at the base. Just like you do in open air, the weight of the air column pushing down increases the pressure.
- bloopernova 2y ago
  Good point! If the launch vehicle can accelerate well enough in low pressure instead of vacuum then maybe you could "just in time" depressurize segments of the tube. Although that's still getting perilously close to the magical airlock concept. Apologies for rambling, this is fascinating.
  - MadnessASAP 2y ago
    It's an interesting idea, but I don't see a feasible use for it on Earth, probably be quite handy for returning bulk materials to Earth from a hypothetical moon base. Unfortunately Earth's atmosphere makes most surface base accelerators to space impractical. A many kilometers long linear accelerator that ramps off a suitable mountain could make for a interesting 1st stage that wouldn't subject the payload to ridiculous G forces. But you'd still need to accelerate the payload and 2nd stage and with SpaceX and co driving down 1st stage costs I still don't see it as cost effective.

MadnessASAP 2y ago

Well actually.... Even if you place the exit at higher altitude with lower pressure, without a seal you'll still end up with higher pressure at the base. Just like you do in open air, the weight of the air column pushing down increases the pressure.

bloopernova 2y ago
Good point! If the launch vehicle can accelerate well enough in low pressure instead of vacuum then maybe you could "just in time" depressurize segments of the tube. Although that's still getting perilously close to the magical airlock concept. Apologies for rambling, this is fascinating.
- MadnessASAP 2y ago
  It's an interesting idea, but I don't see a feasible use for it on Earth, probably be quite handy for returning bulk materials to Earth from a hypothetical moon base. Unfortunately Earth's atmosphere makes most surface base accelerators to space impractical. A many kilometers long linear accelerator that ramps off a suitable mountain could make for a interesting 1st stage that wouldn't subject the payload to ridiculous G forces. But you'd still need to accelerate the payload and 2nd stage and with SpaceX and co driving down 1st stage costs I still don't see it as cost effective.