EricF wrote:Would a fractional output of the drive to allow for a slowed descent help with the heat issue of reentry?Perhaps those flimsy ceramics that keep getting damaged on the space shuttle would no longer be needed?
That depends on the achievable thrust efficiency and thrust-to-weight ratio. The proponents mention 1 N/W as an achievable thrust efficiency, and I've been informed that a T/W of 10:1 is "more than conservative" - I believe there are notional thrusters that approach 50:1. So that's the optimistic expectation.
If, on the other hand, the drive were proven to work and developed, but with no advances beyond elimination of the observed thrust die-off, ground launch and propulsive entry would be ruled out. The thrust efficiency and T/W that Paul March seems to have already observed experimentally would make for a better space drive than VASIMR, but that's all it would be good for...
Polywell-powered QED engines could probably do propulsive entry. Certainly if Bussard was right, Polywell is what you'd call a "game-changer" in a lot of ways.
But if Mach-effect technology works, and works as well as the proponents hope, it's much more than just a game-changer. Fully propulsive landing on (and launch from) every terrestrial planet and moon in the solar system, in sequence, repeatedly, without refueling, would not be impossible. High-thrust trajectories would yield transit times measured in days rather than months or years. Radiation shielding could be as heavy and bulky as you wanted. This technology could render most
science fiction obsolete. It would revolutionize not just space travel, not just air travel, but also power generation and even ground travel. That last probably requires some explanation:
I have a car. It has an IC engine, rated at 114 hp (85 kW). Fully loaded (and it's been pretty full), the car is probably about two metric tonnes. If, instead of accelerating by exploiting the static friction between the tires and the road, I simply used a Mach-effect thruster with a thrust efficiency of 1 N/W, this vehicle would go from 0 to 60 mph in a little over half a second.
The reason is (presumably) that over most of the acceleration curve, there's a significant amount of mass in the universe that has a velocity much closer to the velocity of the car than the velocity of the road is, resulting in the v in P = F·v being really small, so that for a given P, F is large (or for a given F, P is small). So the thrust efficiency could theoretically be significantly higher than that of a
wheeled vehicle.
There's another way it could help, but I won't get into that because I already sound too much like a free-energy nutjob...
Betruger wrote:So the sci-fi winged space/air craft (e.g. Star Wars') would be feasible and interesting design schemes after all.. Nuts.
Yep. You could even use the wings as radiators in space - with enough thrust efficiency, the power dissipation rate should be quite low even for high-thrust operation, so you wouldn't need the proverbial football field...
Actually, a saucer-shaped craft has advantages too, if the available acceleration exceeds 1 gee...