Posted on 09/09/2005 5:26:35 AM PDT by nuke rocketeer
In the past month, we have been blessed with numerous leaks from NASA of various study documents relating to the new boosters that will be needed to carry out the new manned moon program. I've been monitoring the large volume of Web chatter about these plans, and have noticed a disturbing theme therein. Many Space Cadets are expressing dissatisfaction with these leaked NASA plans. They say that the Shuttle-derived boosters are too primitive, too expensive to develop, too expensive to operate, and not inspiring enough. They can't understand why we will be returning to the Moon with rockets and space capsules that look like minor variations of those used in the Apollo program 40 years ago.
(Excerpt) Read more at spacedaily.com ...
Yes.
An ablative shield possibly? Cast a shield from a material that carries away heat when vaporized? (Ice?)
Again, see my post #10. A rail gun, with a mountain top terminus solves both problems. Shooting a vehicle into space while keeping acceleration structural loads below 7 G. Atmospherics are greatly helped by not entering the atmosphere until the vehicle is already above the thickest part of the atmosphere (higher is better). And high energy beams may be able to split the flight path, thus decreasing resistance even more.
Does this involve large amounts of cabbage , beans and beer?........
First off is the fact that even at 29,000 feet (the top of Mt. Everest) you've got a hell of a lot of atmosphere to deal with, and you're going to hit it at well over 8 km/sec (you have to account for drag losses in your exit velocity). You can't be going straight up -- your velocity has got to take you in a ballistic trajectory that forces you to remain in the sensible atmosphere (which lasts up to ~400,000 feet) for quite a long time -- several minutes, at least. Note that the Shuttle sheds most of its orbital energy, and thus gains most of its atmospheric heating, above 200,000 feet. Bottom line is that there are tremendous heating issues to deal with, even with a rail gun.
In essence you're reversing the ballistic missile re-entry problem. (Harvey Allen's famous work on re-entry body shapes is summarized here, with a good assessment of the heating issues involved.)
An alternative is to use a railgun to boost the vehicle to a "respectable" speed to get it up high, and then use rockets to finish the job. The problem there is that the power overhead for the railgun probably increases tremendously due to the vastly increased launch mass.
You've also got to deal with the problem of how to move your great big mass through the long tunnel. You've got probably surmountable alignment and smoothness issues, but you've also got to deal with holding the payload in the center of the gun. Do you put it on rollers?
Finally, you've got to figure out a way to pull the air out of your tunnel, but still allow the payload to get out safely. This means a door of some sort that has to be big and heavy enough to keep air out, but must be nimble enough to open quickly, when the payload is close to the exit. Unfortunately, the act of opening the door will let the air come cascading in, which will lead to severe turbulence, buffeting, and shock waves as it rushes down the tunnel and comes into contact with the hypervelocity payload. Your tolerances are shot at that point, and you'd be in significant danger of hitting the wall, which would be a disaster.
So there's a huge design issue there that can probably only be addressed by adding "non-propulsive" length and width to your tunnel, and/or by making a faster door. Note that if it takes one second to open the door, then you've got to ensure that your payload is at least 8 km away when you start to open it. If you've got any experience with supersonic wind tunnels, you'll recognize the likelihood that there will be a large shockwave coming down the tunnel toward your payload.
Actually, perigee will probably be much lower than that (subterranean), because you probably can't achieve a horizontal velocity at the exit without taking a very sharp turn somewhere close to the exit: mountains are generally too pointy to allow the gradual curve needed to achieve a horizontal exit, and it would be prohibitively expensive to build an external tube.
Nope, just a label on the reactor.
Thin glass suffices to hold the vacuum in an electron tube at sea level. Why not a glass window that the ship smashes through?
At 8 km/sec? It would make a pretty flash and you might get some shrapnel into orbit.... ;-) (And the glass would have to be thick....)
But I heard they have the tehcnology . .
they can rebuild him . .
faster . .
stronger . . .
Perhaps I'm foolishly cautious but somehow I don't think that I would like to be the first to test drive an atomic bomb motorized vehicle. Maybe that's why it never became a reality. They couldn't find the volunteers.
It would depend on how large the opening was. A dome shaped glass can be thinner than a flat pane that withstands the same vacuum, just like relatively strong light bulbs can be made of very thin glass because of their globular/tubular shape.
The ship could have a pointy tip at the end of a rod to break the glass, and the rod itself made so it would break off once the ship hit air. The glass could be inscribed with break lines on the inside like a hand grenade, so that it would come apart neatly without bits getting sucked back down the tube before the ship could get all the way out.
The DOD actually funded a scale model test back in the late 50's or early 60's that used conventional explosives. It worked and did not fly apart and had no significant erosion of the dome.
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