I was wondering - Could one send an objetc to space using only a really big catapult or slingshot? Rockets are usually huge because they need a LOT of fuel. What if someone wants to send a small object to outer space and has no access to fuel?
Do a search on Railguns. That’s probably the likeliest way it will happen.
This article (as the name suggests) discusses a variety of ways to get stuff into space without using the traditional rocket engine approach:
You have two main problems with something like a catapult or a slingshot.
First of all, all of your acceleration would have to happen over the length of the machine’s working distance. So your object has to go from a dead stop to a velocity capable of reaching space over the length of your catapult’s throwing arm. There are very few things that could survive such nightmarish acceleration forces. A human being would be squished into a puddle of goo. Something like the space shuttle would be smashed into a bizillion pieces.
The second problem is that the object that you are launching would also have to be able to survive hurtling through the lower atmosphere at those speeds. The friction from the atmosphere will burn up most things at those speeds. Consider that the space shuttle, which accelerates much more slowly using rockets, can’t even crank up its rockets to full power until it has left the lower atmosphere, because the shuttle couldn’t handle the aerodynamic stresses involved with going faster through the atmosphere. If you listen to old space shuttle launches, the phrase “go at throttle up” was the point where they were through the lower atmosphere and could finally crank the rockets all the way up without destroying the shuttle (it’s also the point at which the O rings burned through and destroyed the Challenger).
As an aside, it’s quite possible that the first man-made object in space wasn’t launched by a rocket. During an underground nuclear test someone forgot to weld a manhole cover in place. It was difficult to tell from the test camera footage, but some of the scientists and engineers involved calculated that the manhole cover may have had sufficient velocity as it passed the test camera to have made it all the way into space. That helps to put it in perspective, though. Your object basically has to be able to survive being blasted into space by a nuclear bomb. If it can handle those kinds of stresses, then it can be launched into space from the ground. That’s roughly the order of magnitude involved.
A spacecraft is launched by such a method in Footfall.
On Earth I don’t think it’s super practical, because of the aerodynamic heating in the lower atmosphere. But if you’re on the Moon, say, it’s probably a good idea. 34 seconds of 3g acceleration, which anybody can take in a sitting position, will get you to orbital velocity, about 1 km/s. Lay out a 17km linear accelerator and you can just throw things and people into orbit. Make it a little longer and you can throw things into a transfer orbit to the Earth. If you don’t do it too often, you can just accumulate the energy you need for each launch with solar panels. That way you only need rocket fuel for your landings. It might also work pretty well on Mars, which has a very thin atmosphere.
Even if your payload can survive the horrendous acceleration needed, you still can’t get into orbit that way. Without rockets, you’d just go up, and then come back down (more precisely, you would be in an orbit which intersects the surface of the Earth). You’d need to be catapulted up, and then use some rockets at the top of your trajectory to stay in orbit (admittedly, this would take significantly less fuel than rocketing the whole way).
I don’t think that’s necessarily true. If you had a device like a railgun that could be aimed precisely, I would think that you could calculate an angle and initial velocity that would result in an orbital trajectory.
But anyway the real problems, as already stated, are the huge acceleration and the atmospheric friction. Since almost the entire trajectory of the payload would be ballistic, simple physics tells us that its initial speed as it ascended the lower atmosphere would have to be equal to the same speed at which it would return to the surface from orbit PLUS all the losses from atmospheric friction, or in other words, much greater than the speed which causes returning spacecraft to start to burn up even in the thin upper atmosphere. It would be like a meteorite in reverse, vaporizing as it ascended.
Thank you, Mr. Spock.
Well, it was launched by a succession of small nukes, not one.
“God was knocking, and he wanted in bad.”
This was in part the rationale for Arthur Kantrowitz’ Laser Propulsion. Your “motor” sat on nthe ground, and all you had to send up was your payload, enclosure, and your reaction mass (which did not have to be explosive or reactive).
This was distinct from Light Pressure Propulsion, and was orders of magnitude stronger, giving a hefty specific impulse. The idea was that you used a powerful and concentrated laser beam to ablate a thin layer of your reaction mass material from a big frustrum of the stuff attached to your capsule. The ablated material would then be heated by the laser pulse and become optically dense, absorbing the rest of the pulse energy via inverse bremsstrahlung. It would expand, pushing the payload forward. After an appropriate wait for the stuff to dissipate, you’d repeat the cycle. Kantrowitz hoped to use this to propel stuff from the earth’s surface (well, from mountaintops, which gave you a height advantage, and clear air) up to orbit.
The ideas were refined. He eventually favored a two-pulse system (a metering pulse to ablate the material,. followed by a power pulse to heat it and induce a Laser Sustained Detonation Wave). Ideally, the ablated material would be ice, maybe mixed with some stuff to improve absorbtion of the laser wavelength, and to promote ionization.
I woeked on this for a few years, and blasted dime-sized pieces of plastic around the lab. The concept was picked up in science fiction by Jerry Pournelle (“High Justics”), Michael Cube McDowell (“The Quiet Pools”) and Dean Ing (various pieces). The nice thing was that, as in Pournelle’s story, you coulkd send up delicate structures like, well, people, because it didn’t all depend upon a single big PUSH at the start, but had a continuous and gradual puish all the way up. But you didn’t need lots of rocket fuel and machinery to control ity, and so you could save on all the extra fuel needed to lauch the initial fuel.
I don’t know of anyone who actually got this working for a launch of a payload into space, or even up in the air, but a related idea did see reality – Rensselear Polytechnic’s Prof. Leik Myrabo’s Apollo Lightcraft substituted air for the reaction mass, soi you didn’t even need to carry the reaction mass. His craft focused light on ambient air, causing it to expand and push the craft upwards. Obviously, this coul;d only operate as long as air surrounded the craft, but his idea was to bulld up momentum while in the atmosphere. Some of his launches at White Sands, NM are on YouTube, and he has a website:
http://science.nasa.gov/science-news/science-at-nasa/1999/prop16apr99_1/
In The Fountains of Paradise by Arthur C. Clarke, humanity builds an elevator from Sri Lanka to a satellite at geostationary altitude (twenty-some thousand miles). They use a bunch of wire-like material that is just a couple molecules thick (would make a really good weapon). Not sure how the system is affected by rotational wobble or crust slippage, but they must have got the technique down pretty well, because at the end of the book, there were several towers all around the globe.
It’s also somewhat complicated by the fact that the mass of the shuttle (or any rocket) is changing significantly as it burns off fuel. I saw performance graphs of the Saturn V once, and it burned off about 75% of its mass in the first three minutes. A thrust that would give you 3g at liftoff would be giving you 12g just before the first stage was empty and jettisoned.
Ooh, we have got to send this to Mythbusters.
Sadly no. You need to change your direction to circularise your orbit. Otherwise all orbits return to their start point. The moment your object leaves the end of the rail-gun it is in orbit, since there is no further addition of speed. No matter what direction you point it, its orbit will eventually bring it back to the point it left. Unfortunately, this path will involve intersecting the Earth’s surface. Even if you jump off the ground under your own leg power, you are orbiting the Earth for a moment. Orbits don’t care about the existence of the Earth’s surface, they are all relative to the centre of mass of the Earth. The surface is simply an unfortunate complication for those orbits that are not very circular.
I’m not sure that Frank Doyle can pull off going full scale with that one.
Shot Pascal-B, in Operation Plumbbob, is the one you’re talking about. A scientist involved with the shot, Dr. Robert Brownlee, wrote here about the predicted velocity for the four inch thick steel shaft cover, as well as what was actually observed.
You don’t need a nuke to explode things into space. Project HARP used an extra-long 16 inch battleship barrel, with some adjustments to the propellant, to launch payloads up to 110 miles high. If the solid-rocket motors in the test vehicles had worked like they were supposed to, they might have eventually shot one into orbit.
When I was young and growing up in Vermont there was a lot of news about this guy, Gerald Bull working on something to use large artillery pieces and shoot stuff up into orbit. He was also working on a Project HARP sponsored by the Defense Department for that. I recall it all over the newspapers when I was a teenager long long ago. From what I understand up in Northern Vermont still there are foundations and steel tube still about discarded from some project of his.
Then he pursued other interests, one of which was providing artillery for Iraq and could shoot 1000 miles, or so, which is enough range to hit Israel.
Someone took exception to that and Mr. Bull was sent packing onto the next life.
This depends on how you design your projectile. If you heat-shield all but a single control fin, the fin will burn off while also affecting the trajectory. Once in space, you might be able to fling off a small bit of mass to achieve the desired orbit. These strategies would not violate the “without engines” concept.
If a railgun shot a hollow, cylindrical projectile with a lens in its center, could a powerful ground-based laser shoot through the lens and vaporize the atmosphere directly in front of the projectile, creating a vacuum for it to travel through with decreased resistance?
You can work out what the velocity change is, and then work out how much mass and how fast you need to fling it. Turns out the answer is: very very fast; and about the only technology capable of flinging mass that fast is a rocket engine.