a friend of mine for a school project made a gauss driver that accelerated a 1 gram projectile to 40 km/h with only a couple feet of coil

ya it was. Helped some friends move yesterday and am still destroyed from the experience. proof reading capabilities have been slow to return to a functional state

It's been a long time since I looked it up, but if I'm remembering correctly experiments with off the shelf electronics potted in epoxy could survive up to 20,000Gs of uniform acceleration. The trick is how small all the 'delicate' bits are. I think it was for the SHARP project?

dare wrote:

Looked up some more data, and sure enough, 1000 G's seems to be doable according to some real-world scientists. I'm surprised, but not complaining.

1000 g's is doable for what? Solid inanimate objects? I believe some of the rail guns being tested today exceed 60,000 G's in acceleration when firing solid projectiles. I'm guessing your 1000 g target is based off the object being fired being something where damage is more of a consideration. Incidentally, while they may say that these guns are used to put packages in orbit cheaply they are not the only source of propulsion for those packages. It simply isn't possible to shoot something into orbit without a secondary method of propulsion because the elliptical orbit would trace back through the gun. The full operation is probably something along these lines: Assuming the railgun is 200m in length the package is accelerated at about 650 G to a velocity of about 1.6 km/s. It is given a fairly flat trajectory that would not normally exceed an altitude of 50km and during the trip it fires a small metallic hydrogen rocket that accelerates it to a circular orbit of 50km. To do this the engine needs to generate a Δv of an additional 400 m/s. This requires a burn of about 13 seconds (assuming that the metallic hydrogen produces 3 G of acceleration). Assuming metallic hydrogen has a specific impulse of 1600 2.5% of the launching mass would need to be reaction mass. You would have a bit more taken up with the nozzles, power supply, and stabilizing em field generator but you are probably looking at about 90-95% of the launch mass being cargo, which is really good. Incidentally, you could also launch at even slower speeds. 250 G's would give you a muzzle velocity of around 1 km/s but you would be required to now use 6% of your launch mass as remass. This is still better than using 12% of your launching mass which is what is required without the rail gun.

It makes it easier to intercept. Picking up cargo is pretty much the same as a docking maneuver and trying to match a highly elliptical orbit is always a pain in the behind. Also, you've got to spend at least some secondary propulsion to bring up your periapsis, unless you just trust people to always collect the cargo before it can complete a single orbit. Otherwise your minimum periapsis is the elevation of the railgun (it can and probably will be lower but it can never be higher unless your launch velocity is high enough that you are on an escape trajectory). If you are already doing that circularizing the orbit actually isn't all that hard. Just make sure the vehicle remains pointed in the direction of travel (i.e. make sure the engine is pointed directly prograde) and as you approach apoapsis fire the engines. You will gain a small amount of altitude for your apoapsis since you aren't completely parallel with the surface (that only happens at apoapsis) but most of your energy will go into raising your periapsis. Since your initial trajectory was a little shy of 50 km at apoapsis the small amount of increase will bump you up to right around 50 km. Cut off the engine when your apoapsis and periapsis match and you're circular. I do this more or less 'by hand' (computers keep the ship facing prograde) in Orbiter all the time and if I'm being really obsessive I can get a perfectly circular orbit every time by using the RCS for final adjustments (I mention that I have to be really obsessive to do this. It isn't that its hard, its just that generally you don't worry as long as periapsis and apoapsis are within a dozen km of each other).

Right. I talked about that in a previous post. The problem with the idea of 'pick it up at apoapsis' is 'what happens if you miss?'. If you're not equipping the payloads with some form of secondary propulsion that is strong enough to put the payload into a permanent orbit (i.e. one that can sufficiently reduce the eccentricity of the orbit) then when someone misses a payload (and sooner or later it will happen) the payload will return to the surface with almost the same amount of energy it launched with (since there's no atmosphere to bleed off energy).

They're done on spreadsheets but I could break them down into their formulas if you really want. Which ones did you want, though?