Good luck aiming the slugs to hit the rail on a vehicle a million kilometers away.
Quote from: ChrisWilson68 on 04/13/2017 09:18 pmGood luck aiming the slugs to hit the rail on a vehicle a million kilometers away."Railgun" is the wrong device. It's would been to be a variant on a maglev launcher, with the "net" at each end being a long magnetic funnel. to steer the projectile into the braking/accelerating tube(s).[And if you really don't care about delicacy, you can always use the Orion model. Big impact plate. "Kinetic Sail". Bang bang bang.]
I like composites, but aluminum lithium alloy is pretty great. Aluminum 737 has lighter dry weight per passenger than composite 787, for instance.
There are actually some manufacturing advantages to composites, which is why you have fiberglass boats and wind turbines instead of just aluminum. Composites are easier to make compound curves, for instance.
The REAL trick why rockets can beat alt-launch concepts is because of rapid reuse. Reusing the booster 1000 times and the upper stage hundreds of times with zero refurb on the booster and virtually none on the upper stage. Rapid reuse and the ability to use LOx and LNG, both ridiculously cheap, is the biggest threat to alt-launch.
I think the optimal solution for that route would be a dynamic version of the space fountain, where the top isn't gradually lifted up by the pellet stream, but accelerated to escape velocity. This would be my favourite pet idea since it can have near-optimal energy efficiency all the way up to escape velocity and doesn't require a track.
Composites are easier [than metal] to make compound curves, for instance.
You can do it with metal, but you need a big press or need to rivet smaller pieces together or stamp them with a hammer, etc. It's more difficult to achieve complicated curves with metal parts.
Quote from: Nilof on 04/15/2017 12:22 pmI think the optimal solution for that route would be a dynamic version of the space fountain, where the top isn't gradually lifted up by the pellet stream, but accelerated to escape velocity. This would be my favourite pet idea since it can have near-optimal energy efficiency all the way up to escape velocity and doesn't require a track.Confused here. In order to accelerate the ship to orbital velocity, the pellets need to be have more than orbital velocity when they reach the ship, and so haven't you just invented a space-cannon for the pellets?
If you think that's all they're good for... then if you do happen to build one, (a) please don't tell your military about it and (b) please don't aim it in the direction of North Korea! (..or the Middle East, Russia or anywhere else on Earth, pretty much)
Mass drivers are possibly the most practical option for non-rocket space launch.
Quote from: ChrisWilson68 on 04/13/2017 09:18 pmGood luck aiming the slugs to hit the rail on a vehicle a million kilometers away.Im sure you could think of alternatives yourself. I think what you are actually doing is continuing the topic of recent posts, pointing out the huge gulf of technical hurdles before ideas like this could supplant reusable rockets. I totally agree there.I was really just making the academic point that there is a potential loophole to escape the obvious problem of scaling magnetic schemes up to HSF scales and down to HSF-survivable accelerations.
Quote from: Nilof on 04/09/2017 06:32 pmMass drivers are possibly the most practical option for non-rocket space launch.Something moving 7.7 km/s at sea level would have a dynamic pressure of 37,000 kilo pascals. This speed at the top of Chimborazo would 17,000 kilopascals. A severe hurricane is about 3 kilo pascals. Max Q for ascent of many space craft is around 35 kilopascals.And what is flight path angle at launch? If straight up, it'd get out of the thick atmosphere pretty quick. But with no horizontal velocity, it'd come straight back down.If launched at near horizontal flight path angle, it'd take 20 minutes or so to ascend above the thick atmosphere. Given a .04 drag coefficient, radius of 1.8 meters and a 500,000 kg rocket, that'd be 20 to 30 minutes of 1.5 g deceleration. Nine minutes at that drag would completely kill a 7.7 km/s velocity.
Build a 50km tall tower. Way easier than a space elevator!
Of course, entirely other things might be superior to chemical rockets in the long run, it's just that I wouldn't bet on it being mass drivers throwing slugs over enormous distances at vehicles.
Quote from: Robotbeat on 04/18/2017 11:33 pmBuild a 50km tall tower. Way easier than a space elevator! And way easier than warp drives as well. But still not plausible.
Quote from: Hop_David on 04/19/2017 05:20 pmQuote from: Robotbeat on 04/18/2017 11:33 pmBuild a 50km tall tower. Way easier than a space elevator! :)And way easier than warp drives as well. But still not plausible.I mentioned earlier in the thread the idea of having lighter than air skyscrapers. I think the record for high altitude balloons is about 50km.Having a tall structure like that could also give you a lot of control over your altitude also, by shuttling some pressurised compartments up and down like elevators. Near the top they would transform into dead weight.Access to all these different heights could also allow you to tack against different streams and perhaps also generate power.
Quote from: Robotbeat on 04/18/2017 11:33 pmBuild a 50km tall tower. Way easier than a space elevator! :)And way easier than warp drives as well. But still not plausible.
Build a 50km tall tower. Way easier than a space elevator! :)