Extremely skeptical about this airship thing. Calling even 127,851 feet "the edge of space" is a bit generous. Even if we go by the lower American boundary to space, 50 miles is 264,000 feet. Felix Baumgartner was less than halfway there.
It still gets you above more than 99 percent of the atmosphere. Atmospheric drag is significant, particularly for small rockets. Maybe not as much for the behemoths like the Starship. Let's say you have a 1 foot diameter rocket going Mach 5 with a drag coefficient of 0.3. The drag will be about 30,000 lbs. (see below about the orbital gun). So rockets launched from sea level don't accelerate as hard as they might until they get some of the atmosphere below them. Going a bit slower for a while means more is lost to gravity as well. If you launch from 127,000 feet, you can forget about this problem and accelerate as hard as is practical. Plus, any fairings to deal with what's left of the atmosphere will be much lighter than ones made for denser air would be.
On the other hand, how much helium do we have to throw away? Seems like if this was a regular thing, we might use up the reserves fairly quickly. Maybe people could be persuaded to accept hydrogen. It would probably be a good idea to burn the balloon and its gas after the launch.
don't worry the investor scammers are still out there like a
pneumatic orbital gun, I love how they just ignore what happens once it leaves the gun, and they plan on building this thing at sea level.
I checked out their site. (longshotspace.com) Their current subscale test rig, which gets up to Mach 4.2, accelerates projectiles at at least 5,800 g's. I doubt if a useful rocket can be made to withstand that much. On the other hand, they say they eventually want to make a 500 meter long cannon to get a 220 lb load up to Mach 5. That would take at least 300 g's. Let's say that load is 6 inches in diameter and has the same drag coefficient of 0.3, as above. If at sea level, maybe the drag would be around 7,500 lbs. That's more than 30 g's of acceleration in the wrong direction. No doubt, the muzzle would be above some fraction of the atmosphere, so maybe the drag will really be "only" 6,000 lbs. Still a problem.
Considering the aerodynamic drag, I wonder what the optimal angle for the launch would be, and how they'd support a 500 meter long cannon at that angle. I also wonder if a rocket built heavily enough to withstand 300 g's, launching at Mach 5, would actually have an advantage over one that launches at 0, but only needs to withstand 5 or 10 g's. I also wonder how useful tiny payloads, made to withstand 300 g's, would be.
Maybe the trick would be to bribe some politician near the equator with high mountains in his country, who doesn't care about environmental issues*, and build the cannon there. Maybe the muzzle could be at 20,000 feet, above half the atmosphere. And maybe a mountain with an appropriate slope for supporting the cannon could be found.
Obviously, I'm pretty skeptical about this proposal.
I suspect that, in the long run, if we continue to be a technological civilization, we'll have a space elevator. There are also some other dodges I've run across that wouldn't be quite as difficult as the space elevator. Still plenty challenging, though.
*Deaf llamas and condors, at a minimum. And who knows what propellant they'd end up using.
