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A Space Cannon That Might Actually Work
Unequivocal writes "Chalk another one up to Jules Verne. Physicist John Hunter is proposing a space cannon with a new design idea: it's mostly submerged. 'Many engineers have toyed with the [space cannon] concept, but nobody has came up with an actual project that may work. Hunter's idea is simple: Build a cannon near the equator, submerged in the ocean, hooked to a floating rig ... A system like this will cut launch costs from $5,000 per pound to only $250 per pound. It won't launch people into space because of the excessive acceleration, but those guys at the ISS can use it to order pizza and real ice cream.' Though it won't work on people, with launch costs that low, who cares?"
If you try to launch an object from the surface of the Earth using a "cannon" the projectile won't be doing anything other than decelerating throughout its flight and this means bringing the projectile to very high velocities where atmospheric heating and stresses become major problems. Then again, launch its self may be a problem as the Hydrogen propelling the projectile is detonating at an extremely high temperature and pressure. Small nitpick as well from TFA:
A big reason space food is what it is instead of the Earthling food we're all accustomed to has to do with keeping the station reasonably clean and experiments doubly so. Crumbs and fluid loose in the station can cause problems.
Sigs are too short to say anything truly profound so read the above post instead.
For most ideas, feasibility lay entirely on the hands of engineers.
For example, building a skyscraper 2km tall is merely an engineering problem. A space elevator is merely an engineering problem. A script to automatically discard redundant comments is merely an engineering problem.
Still, parent's comment is obviusly not discarded.
http://en.wikipedia.org/wiki/Project_Babylon
Yes gents, Saddam Hussein could have given us cheap access to space ensuring new area of prosperity for mankind, and era of space colonization...and we killed him!
PS. If a supergun has a basic design similar to German V-3, it might be almost bearable to humans...
One that hath name thou can not otter
Min orbital velocity = 7.6 km/s
Earth Escape Velocity = 11.2 km/s
Funny coincidence, world record for hydrogen gun == 11.2 km/s
These guys plan to have the gun propel the projectile to 6.0 km/s, and then the projectiles themselves are rocket motors that will add an additional 3.0 km/s. That gives them enough acceleration to reach orbital velocity and take into account friction/gravity losses.
The reason they plan to limit the gun to 6.0 km/s is because that requires the hydrogen gas to only reach 1700 kelvin, which after taking into account heat exchange with the barrel, it ends up being a few hundred kelvin below the melting point of steel ( the barrel ).
-Malakai
A Dragon Lives in my Garage
Most reputable materials folks I know still claim its a fundamental technology problem, not merely a funding one. While the expected stresses are nominally within what an ideal carbon nano-tube structure can handle, the purity required for that is well beyond what we can manufacture.
In order to feasibly build a space elevator, we would need much improved nano-technology. Not that I feel that its necessarily an idea-killer -- I'm not terribly knowledgeable on nanotech, but its one of those fields that always surprises me with how fast its going.
Make it long enough and it CAN launch people. (You'll need good streamlining to avoid nasty deceleration when it leaves the muzzle, though.)
The ocean is DEEP. Something that's roughly neutrally buoyant (i.e. a gun barrel supported by floats distributed along its length) needs to spend negligible structural strength supporting itself. (It only needs to be strong on any part that protrudes from the water - which might be a lot to avoid sinking it when it recoils.) You might want to put "helper combustion chambers" along it periodically to boost and smooth the acceleration if you want to launch live stuff though.
Also you can make it larger diameter and put sabots on the projectile while it's in the barrel to reduce the internal pressure variations or fire very dense loads. (Doesn't really help the materials strength issues, though, because the curvature lessens as diameter rises.)
Recoil? By being submerged it's an inside-out hydraulic shock absorber. B-)
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
First of all, you can't get into stable orbit ballistically; you have to use a rocket motor at apogee of ballistic trajectory, at the least.
Also, we do have clear examples of electronics (from the 60's...) surviving launch to half of orbital velocity from a modified big naval cannon (Project HARP). And that's more or less a "normal" cannon, very short, very high acceleration. Look up V-3; such design can maintain almost constant acceleration, close to average one, and be hypothetically several kilometers long.
So why don't we go totally overboard, and assume a barrel length of 30km; and close to half of orbital velocity (so it will be easier, since there's ^2 in this part of equation ;p) - 3.5 km/s. From simple calculations that gives 20 g. Definitely bearable, as far being launched from a cannon into space goes. With 5 km/s you have 42 g.
Yes, widely unpractical and even...stupid. But I didn't actually suggest using it for humans, just said that it might be almost bearable.
One that hath name thou can not otter
You are misinformed (and here you didn't even need to perform any basic calculations...)
http://en.wikipedia.org/wiki/G-force#Human_tolerance_of_g-force // I would venture a guess they were breathing and their brain was supplied with blood // without loss of consciousness or apparent long-term harm. The record for peak experimental horizontal g-force tolerance is held by acceleration pioneer John Stapp, in a series of rocket sled deceleration experiments in which he survived forces up to 46.2 times the force of gravity for less than a second. Stapp suffered lifelong damage to his vision from this test //"this test" likely means eyeballs-out
Early experiments showed that untrained humans were able to tolerate 17 g eyeballs-in (compared to 12 g eyeballs-out) for several minutes
(emphasis mine)
In my hypothetical scenario with 20 g that acceleration would last only 17 seconds, quite bearable. In the overboard example with 42 g, it would last 12 seconds (eyeballs-in!), which still might be survivable (and with eyeballs-in, which stresses eyes less, perhaps even without long-term damage)
One that hath name thou can not otter
Even if a 1.5 light second long cable were feasible you'd still have to deal with the fact that, as far as I understand, the anchor would have to be in geosynchronous orbit. Since the Moon isn't in geosynchronous orbit, the surface moves relative to the Moon you'd end up winding the cable around the planet.
no, no! they would simply make the base of the elevator mobile, and put it onto a train that constantly runs around the equator at the speed of the earth's rotation, plus or minus (as appropriate) the speed of the moon's orbit.
think of the money we'd save getting things into orbit!
For one thing we need a big counterweight, and the 'easiest' way to do that is to tow an asteroid into Earth orbit. I'd say building a space tug is an engineering challenge.
I don't think towing an asteroid is the easiest way; it would be much easier to just start with a very small counterweight (e.g. a rocket stage, or even nothing). That would give you a very low-payload-capacity cable. No problem, you send a very small/light elevator-car up the cable, and when it gets to the end of the cable, it stays there and becomes part of the counterweight. Now you send a slightly larger/heavier elevator-car up the cable, and when it gets to the end, it stays there too. Repeat as necessary until you have enough mass at the end of the cable to support whatever payloads you want to bring up.
I don't care if it's 90,000 hectares. That lake was not my doing.