I had read about the subject sometime before ( can’t remember where - can’t even remember if it was fiction).
But is it possible to launch a spaceship using a large (bore as well as lenght) cannon for the first stage ? It was speculated that this way the overall weight reduces and so does the fuel requirements.
The immense accelaration required to clear the earth would kill any human unfortuante to be a passenger.
When a rocket is used, energy is expended during a period of time and so accelaration takes place over a longer period of time, this occurs for as long as the rocket motor burns and can be over a couple of minutes.
When you use a cannon, all you are relying on is achieving the required escape velocity by the time the projectile exits the muzzle, which is a very short time indeed, a couple of milliseconds, ie from 0mph to 25k more or more(someone will correct me on the actual number itself) in less than 1/1000th of a second.I invite you to take a ride in a fast car that can do 0mph to 60mph in around 5 seconds and see what that feels like, then imagine a force tens of thousands of times greater.
The g-force would be pretty much disastrous.
Using a cannon to launch requires that you accelerate to escape velocity in a very short distance. Because of the g-forces involved in this, it’s not practical for many sensitive instruments and certainly not for humans. However, there have been a lot of proposals about using railgun launchers as mass lifters for raw materials needed in orbit such as building materials for the space station or lunar base.
This trhead sums it up pretty nicely.
Hehe simulpost/link.
The upshot is that it doesn’t seem too practical–esp. considering how much velocity you lose to the first few meters of dense atmosphere you must travel through.
The only upside, really, is that this technology exists now and could be implemented … it just wouldn’t be cost effective at all.
The sum-up section of the FAS link outlines the problems:
Your “first stage” qualification in the OP is very apropos. It seems near-impossible to launch a payload into orbit using ONLY a space gun, without any rocket stages at all.
The idea was used in Jules Verne’s From the Earth to the Moon and its first sequel. In the Annotated version of that book, Walter James Miller contends that Verne knew of the technical impossibility (the acceleration, as noted above, would have killed the passengers. ), but glossed over it to make an entertaining story. Certainly Verne realized the limits to using cannon in the little-read second sequel, The Purchase of the North Pole.(Dan Simmons can get away with killing his passengers from acceleration. Verne can’t.)
This doesn’t excuse H.G. Wells, sixty years later, for using the same idea in Things to Come. Nor of John Baxter, commenting on it in The Science Fiction Film, thirty years later saying that a Space Gun is a practical method of putting people into space.
I remember seeing a TV special a few years ago, probably on Discovery Channel, about some rocket scientist in the 30s (?? 50s??) had experimented with cannon-launched craft. He was considered “on the fringe” and his work was never followed up. Anybody recall this show?
Also, Jules Verne described a cannon-launched, manned ship in his famous novel, From the Earth to the Moon. Checking www.literature.com, he used a nine-foot-wide hollow ball, with an aluminum shell, and he located his cannon near Tampa, FL – both not too different from modern crafts’ aluminum hulls and KSC at Cape Canaveral.
Aack! Must preview and proofread!
Literature.ORG, not .com.
Plus, obligatory note of simulpost with Cal.
Actually, not “near-impossible” but rather impossible. The point at which a body’s acceleration ends is a part of any resulting orbital path. So even without an atmosphere and launched from a mountain top the body is going to come around and smack the muzzle of the gun, at least in an ideal world…
No, I don’t think so.
(1) You shoot a bullet from a gun. It travels forward, arcing into the ground.
(2) You fire another bullet, but with more explosive force. It travels even farther before striking the ground.
(3) Again, more force–the yet-faster bullet travels halfway around the world before it lands.
(4) Again–the bullet circles the earth completely and lands right behind you.
(5) Again–the bullet, traveling at orbital velocity, circles the earth and never stops.
(6) Again–this fastest bullet flies straight off into space and escapes earth’s gravity altogether.
http://csep10.phys.utk.edu/astr161/lect/history/newtongrav.html
See the purty cannon picture down the page.
Last post-- since your point seems to be re: the air friction resulting in deceleration, just keep in mind that the blast could always just be made large enough so that the projectile is traveling at orbital velocity once it’s cleared the atmosphere.
This one is a problem.
Ignoring atmospheric drag and turning this into a thought problem…
As stated above (by MonkeyMensch), the end of the barrel WILL be part of the orbital path unless some force (read rocket thrust) changes the shape of the orbit at altitude.
What if the initial bullet path is not tangential? (i.e., aim up, not parallel with the earth’s surface)
I was speaking without regard to atmospheric friction.
In that case your example (3) is as far around the Earth as you can shoot it and still hit the ground. As with the Holy Grenade of Antioch, (4) is right out!.
Anything faster than (3) but slower than (6) is going to include the gun itself in the orbital path. And with (6) if you fire at more than escape velocity (which is what I assume we’re talking about in this case) unless the gun is pointed vertically the path will be curved as it moves away from the Earth. It ain’t comin’ back but will describe a hyperbolic orbit.
On the other hand: On an airless world, a “space cannon” could be perfectly practical. If you don’t have to punch through the atmosphere quickly, you could launch at any angle, even horizontally, so it’s (relatively) easy to make the gun very long (and thus make the acceleration gentler). Unless you’re going for an escape orbit, you will need some sort of thrusters on the craft to re-shape the orbit, but you’d still get a significant savings on fuel.
Unless something (Earth impact or air friction for instance) interferes, an object will return and pass through the same point, at the same speed, at the same angle.
Of course, the Earth spins. This would leave the launching point someplace else when the object comes back through.
Ignoring air again… the launched object should impact the Earth on “from behind” on its path back to the launch site.
Unless something is done to make the orbit more round, you should get a very eccentric orbit from a ground launch that will intersect the Earth in such a way that the original launch will be exactly duplicated every orbit.
Escape velocity from earth is about 7 miles per second or 37,000 feet per second. A very, very fast muzzle velocity for any cannon, rifle, pistol, etc is 4,000 fps. Since you get no further acceleration once you’ve left the cannon it would be necessary to be going, just a guess, 50,000 fps to overcome air resistance. We’re talking a butt load of g forces here. It seems to me that astronauts are subjected to about 5-6 Gs spread out over 2-3 minutes. The same astronauts coming out of a cannon, even a very long barrelled one, would be subject to 2-3,000 gs. True, it would only be for a few milli-seconds but that’s the same situation a person faces after a long fall onto concrete.