The comments section of this post, while interesting, has drifted way off topic, so I thought I'd start a new, more focused one. Alfred Differ of JP Aerospace stopped by, and a few people have been asking him questions about their concept for getting to orbit with a lighter-than-air vehicle.

Paul Dietz asks:

First: what is the desired thrust/weight ratio?

Second: how fast will it be traveling in the atmosphere, and what is the L/D ratio at those speeds?

I'm not sure that either of those parameters are useful in evaluating the performance of such a beast (assuming, of course, that it will work at all). T/W is meaningless because it's lighter than air, and similarly, L/D isn't relevant because it's getting its lift from buoyancy, rather than aerodynamics. The only really important characteristic, it seems to me, is thrust/drag ratio. In other words, as it goes faster and faster, can it continue to accelerate against the prevailing atmosphere at whatever altitude it is?

Intuitively, what I thought was being proposed is maintaining altitude via buoyancy, and staying high enough that the drag is small enough to allow acceleration, eventually to orbital speeds. Having given it some thought over the past week, my intuition also says that this won't work, because I don't see how you can displace enough air to support you while at the same time having to accelerate through it. If the idea is to just use the upper atmosphere as a starting point and getting into orbit with conventional thrusting, then the T/W does have to exceed one, at least at the beginning, but if that's the case, I don't understand how/why it takes five days to get to orbit.

For now, just color me confused. I hope Alfred will stop by again to elaborate, if he can.

Buoyancy alone won't do the job for the upper atmosphere ascender. The vehicle must be shaped like a large wing and then driven forward somehow. All the aircraft concepts apply, but we have additional sources of lift because we can play games with the lifting gas and the wing shape. Unusual flight options become available with these added degrees of freedom.

The idea started out (at least my mental version of it) as a very high altitude lifter specially designed to operate in the cold, thin air where it can't be ripped up by think atmospheric winds. If we could drive it to some reasonable speed (small mach number) the rocket we carried along wouldn't have to do as much work to make it the rest of the way to orbit. After looking at the airship for awhile, though, we couldn't see any reason to assume there would be an ultimate ceiling for altitude or speed unless we made specific technology assumptions. You can't build an F-16 with wood and fabric appropriate for a Wright Flyer, so don't be surprised if the orbital ascender gets tricky in its design and composition. I don't think we need any unobtainium, though. 8)

If you really extend the fineness ratio, you can connect front to rear and have a in atmosphere version of Niven's Ringworld.

Just fly up to the ring by conventional jet, transfer to rocket and go on to orbit. Eventually cities would be built on the ring to house the workers that service the system. All shielded from the surrounding air of course. When the system is mature, it could take 5 days to get to orbit, IF you stopped for cocktails along the way.

Unobtainium is not needed, but we do need copious supplies of Rareashellium.

I sure would like more details on the ion propulsion system,but then I guess you'd have to kill me if you told me. :) Sounds like it could it be a type of MHD propulsion. Is the power beamed to it?

There is no power beaming going on. There is no MHD stuff going on either. You probably won't think of it, so don't sweat it too much.

We envision the stations floating along above the arctic circle during the summer to stay in the sunlight. They won't be anchored to any one longitude or region, so think of them as moving islands.

I'm not worried about the helium yet. The odds are pretty high that the supply will be there for long enough to prove out the systems and the value of the approach. Then the folks who like hydrogen will be able to make their case for its use where the available oxygen is real thin.

I wish you luck. It will be wonderful if it works out. Of course, everyone here will be waiting to hear more details. My own speculation on the vaguely mentioned “ion drive” is that it has to be setting up some kind of area effect, interacting with the surrounding environment – perhaps particle beams to set up a differential charge to push/pull the craft through the air. Or something fancier, but setting up some kind of electromagnetic or electrostatic interaction. Probably something that works better with or depends on a very large, low density structure.

Tesla is our friend ;)

naudswy cjrupmz labvzfwo qegyd wsvfumkht yqemdnt typqvchdg

naudswy cjrupmz labvzfwo qegyd wsvfumkht yqemdnt typqvchdg

nlrstixm teasfhi giknotpq asblfcihv ynkmhef gwiaek mytsclonk

nlrstixm teasfhi giknotpq asblfcihv ynkmhef gwiaek mytsclonk

vgru gelrxfvu lsgxudwac mzekux vuragb ieqj srjto