Well, we know for a fact that a '59 Corvette convertible can re-enter the Earth's atmosphere and land at least somewhat safely, as demonstrated in the 80's documentary "Heavy Metal". By canonical TL definitions, that is a TL6 vehicle, and an Air/Raft is TL8+.far-trader wrote:
Again though, it's a messed up idea from the get go. Poorly thought out and described imo. Intended I suspect merely as a plot device with no more thought than that given to it. And probably (I can almost recall the story) ripped whole cloth out of some Golden Age sci-fi. One that wasn't originally well thought out I expect, or if it was that info was neglected in dropping it into Traveller.
Can you offer your points to why you think the whole "reach orbit" thing is a reasonable statement?
Seriously though, while an Air/Raft achieving "orbital altitude" (that is, clear of the atmosphere) doesn't seem unreasonable, I have a hard time imagining one gaining enough linear velocity to be able to catch up to a ship in a free-fall orbit. (Maybe ships don't use free-fall orbits? Nah, I can't imagine that every high port is effectively a high-flying "floating city", though of course grav technology makes that a possibility....)
Once free from atmospheric drag, I can't see any reason an air/raft *shouldn't* be able to accelerate indefinitely as long as it still had a gravity well to push against, given how few restrictions are actually in canon, and how vague the "top speed" is. (Top speed in an atmosphere? In a vacuum?)
(IMTU, "lifter" grav systems do not really "thrust" like a jet or rocket, but act more like a propeller or maybe a wheel - the a-grav field can "grip" space and forces it away from the craft in any direction, with a speed limited by the pulse rate of the engine and the aerodynamics of the vehicle. You can turn off "g-friction" for faster travel, as with speeders or starships, which use alternate means to provide forward thrust. But even those can fall back on the lower speed but more precise "grippy" propulsion for fine control during landing or take off. The local gravity doesn't deteriorate the performance of lifters; I imagine there is the equivalent of a "Ground Effect" deep in a gravity well, so the whole "Can a 1-G drive take off from a 2g world?" question is resolve as "yes - the 2g world's gravity well gives the drive "more to push against". Though by the same logic, you can't use a lifter to get out to the 100d distance, since there's not enough to push against out there.
Major hand-wavium, but it solves a lot of conceptual problems.)
I suspect that aside from the sci-fi reference (which I don't recognize), the paragraph was meant to allow the use of Air/Rafts as an emergency way to get back to a ship in orbit if your Launch got trashed.