"A Cannon for Shooting Supplies into Space"

[Morbius Sire]

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John Hunter wants to shoot stuff into space with a 3,600-foot gun. And he’s dead serious—he’s done the math. Making deliveries to an orbital outpost on a rocket costs $5,000 per pound, but using a space gun would cost just $250 per pound.
Building colossal guns has been Hunter’s pet project since 1992, when, while a physicist at Lawrence Livermore National Laboratory, he first fired a 425-foot gun he built to test-launch hypersonic engines. Its methane-driven piston compressed hydrogen gas, which then expanded up the barrel to shoot a projectile. Mechanical firing can fail, however, so when Hunter’s company, Quicklaunch, released its plans last fall, it swapped the piston for a combustor that burns natural gas. Heat the hydrogen in a confined space and it should build up enough pressure to send a half-ton payload into the sky at 13,000 mph.
Hunter wants to operate the gun, the “Quicklauncher,” in the ocean near the equator, where the Earth’s fast rotation will help slingshot objects into space. A floating cannon—dipping 1,600 feet below sea level and steadied by a ballast system—would let operators swivel it for different orbits. Next month, Hunter will test a functional, 10-foot prototype in a water tank. He says a full-size launcher could be ready in seven years, provided the company can round up the $500 million. Despite the upfront cost, Hunter says he has drawn interest from investors because his reusable gun saves so much cash in the long haul. Just don’t ever expect a ride in the thing: The gun produces 5,000 Gs, so it’s only for fuel tanks and ruggedized satellites. “A person shot out of it would probably get compressed to half their size,” Hunter says. “It’d be over real quick.”
How to Shoot Stuff into Space
STEP 1: HEAT IT
The gun combusts natural gas in a heat exchanger within a
chamber of hydrogen gas, heating the hydrogen to 2,600˚F and causing a 500 percent increase in pressure.
STEP 2: LET THE HYDROGEN LOOSE
Operators open the valve, and the hot, pressurized hydrogen quickly expands down the tube, pushing the payload forward.
STEP 3: TO INFINITY AND BEYOND
After speeding down the 3,300-foot-long barrel, the projectile shoots out of the gun at 13,000 mph. An iris at the end of the gun closes, capturing the hydrogen gas to use again.

Saw this article a while ago, and it made me wonder: Theoretically and/or practically speaking, is such a thing possible?

[CtrlAltDe1337]

What happens when a storm/gale/hurricane hits the water-gun? It doesn't seem like that would be good for aiming. Cool idea though, I hope it works.

[MathiasOfAthens]

Whats the point of aiming? The sky is huge, you wont miss.

[visser300]

Another stupid idea.

[Gaidin]

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Saw this article a while ago, and it made me wonder: Theoretically and/or practically speaking, is such a thing possible?

I'M LOOKING FOR AN ONION LINK BUT I CAN'T FIND IT. SOMEONE HELP ME OUT HERE.

One word: Deceleration. Guy thought of step 1. He forgot step 2. Not that the atmosphere wouldn't break apart anything shot with the sheer amount of force necessary to give it that much lift anyway. So I'm not sure he even thought of step 1.

[hellheaven1987]

This is finally going to be true.

[Phier]

This is not a new idea, nor is it completely crazy...

http://en.wikipedia.org/wiki/Gerald_Bull

[saglam2000]

It's a good idea, too bad good ideas never get funded.

[Sphere]

Running some interesting calcs.

If the 5,000G's is real, that means a 1ft cube of solid steel (500lb) would experience a compression stress of ~17,000 psi. The yield strength of normal plate steel is ~36,000 psi . Start getting to ~1000 lbs payload and you are in a range which can deform some metals.

It's an interesting idea, but I think it would have to be limited to small payloads of .... less than delicate materials. A conventional rocket experiences ~3G's on takoff, and special care is taken in design to prevent damage to the payload. What do you do with 5,000G's?

A $500 million gun to launch artillery shells containing water into space?

[Phier]

Running some interesting calcs.

If the 5,000G's is real, that means a 1ft cube of solid steel (500lb) would experience a compression stress of ~17,000 psi. The yield strength of normal plate steel is ~36,000 psi . Start getting to ~1000 lbs payload and you are in a range which can deform some metals.

It's an interesting idea, but I think it would have to be limited to small payloads of .... less than delicate materials. A conventional rocket experiences ~3G's on takoff, and special care is taken in design to prevent damage to the payload. What do you do with 5,000G's?

A $500 million gun to launch artillery shells containing water into space?

In the long run, if it worked of course, it would be worth it for water alone. I'm guessing food could be sent as well.

[chamaeleo]

I'm guessing food could be sent as well.

It'd make for some mighty interesting pressure cooker recipes:

add whole uncooked turkey (8-10lb), 4 cups chopped potatoes, 2 whole onions, 6 carrots, 1 clove garlic, 1/2 cup butter, 2 tbs thyme, 2 tbs salt, 1tbs pepper, 1tbs rosemary, and 4 cups water. Seal vessel, aim, launch!

[Sphere]

In the long run, if it worked of course, it would be worth it for water alone. I'm guessing food could be sent as well.

Digging deeper

So let's carry cubic foot of water into space in a cylindrical container of radius 1ft and see how thick the walls need to be. Use some high alloy aluminum (fmax~40ksi)

1cubic ft x (62.4 lb/cf) 5,000G = 312 kips

Water Pressure "P" = 312 kips / 1*pi^2 = 31 ksi

t = PR/fmax = 31*1/40 = .8in


^ So to contain the water pressure you need ~.8in thickness of wall per 1 cubic foot of water. Actually more because the walls of the vessel will be under stress from the acceleration of their own mass as well.
Lets say an inch per cubic foot of water, very roughly speaking.

Not out of the question but still means a fairly small payload.

[Morbius Sire]

This is not a new idea, nor is it completely crazy...

http://en.wikipedia.org/wiki/Gerald_Bull

I never said it was. I just wanted to see if it was feasible, and if it is practical to do so. Plus I wanted to share it

Also, Gerald never actually succeeded in doing that, and he was killed after working with the iraqi government to design an obsolete technology.

Digging deeper

So let's carry cubic foot of water into space in a cylindrical container of radius 1ft and see how thick the walls need to be. Use some high alloy aluminum (fmax~40ksi)

1cubic ft x (62.4 lb/cf) 5,000G = 312 kips

Water Pressure "P" = 312 kips / 1*pi^2 = 31 ksi

t = PR/fmax = 31*1/40 = .8in


^ So to contain the water pressure you need ~.8in thickness of wall per 1 cubic foot of water. Actually more because the walls of the vessel will be under stress from the acceleration of their own mass as well.
Lets say an inch per cubic foot of water, very roughly speaking.

Not out of the question but still means a fairly small payload.

Hmm, out of curiosity; what about the high temperatures around the container/cylinder: since the Aluminum container is being propelled at such a high pressure and speed, won't the temperature be very high? At least high enough to be close to the melting point of the Aluminum alloy, if not more?

As well, How would the inside of the cylinder be insulated from outside temperature? after all, Aluminum has a great thermal conductivity; won't the water/transportation-material boil and/or melt during the flight?

But this is a specific criticism/question. I am sure Al can be switched with a carbon fiber-reinforced composite. It has a lower density than Al, and a relatively higher strength.

[Sphere]

Hmm, out of curiosity; what about the high temperatures around the container/cylinder: since the Aluminum container is being propelled at such a high pressure and speed, won't the temperature be very high? At least high enough to be close to the melting point of the Aluminum alloy, if not more?

Wouldn't concern me, its only in the barrel for maybe a second(?) which is not enough time to transfer any meaningful amount of heat. Air friction causing high temps while in flight would be far more concerning, because if you think about it, you'll have about the same heating as a craft reentering the atmosphere.

But this is a specific criticism/question. I am sure Al can be switched with a carbon fiber-reinforced composite. It has a lower density than Al, and a relatively higher strength.

Maybe, maybe not. CF while very high-strength/weight is also exceptionally brittle. From a fracture mechanic's perspective, ultimate fracture stress is less important than fracture toughness. If it is okay to let the vessel yield and deform a little, a ductile metal might make more sense than CF. Or maybe a combination of the two; an inner CF vessel, nested inside a ductile metal container.

[Ascarona]

Mweh even if it is a small payload, if it proves to be a working mechanism then have the gun fire multiple times until the station is restocked. It would be cheaper than the rocket method, and if it goes wrong you wouldn't lose as much either.

[Sphere]

Well, I think the bigger problem than just getting the "shell" into orbit, is how do you get the payload to go where you want it?

With a conventional rocket, a little wind, a little extra atmospheric pressure, and little engine flakiness etc. is no problem. You can always correct course and speed. With a shell, how do you insure you'll get it to, say, the international space station? Is it going to somehow guide itself in, or are you going to move the whole station to go get it like some trillion dollar golden retriever? How are you going to "dock" with it? How are you going to open a casing made to withstand 5,000G? A lot of delicate technical problems at odds with what is essentially a cannon shell.

[Phier]

Well, I think the bigger problem than just getting the "shell" into orbit, is how do you get the payload to go where you want it?

Oh you mean we have to figure out how to stop it?

[Rhaegar1]

I thought that supplying astronouts right now is being done at the same time they change the crew in ISS. However, if this works for this price I see a more interesting application of the technique for getting rid of nuclear waste. For 250$ per pound we are talking about half a million for getting rid of all the nuclear waste produced by a 500 MWe NPP like the one in the netherlands per year. Seems like a sweet deal to me.

[visser300]

I thought that supplying astronouts right now is being done at the same time they change the crew in ISS. However, if this works for this price I see a more interesting application of the technique for getting rid of nuclear waste. For 250$ per pound we are talking about half a million for getting rid of all the nuclear waste produced by a 500 MWe NPP like the one in the netherlands per year. Seems like a sweet deal to me.

So you get rid of nuclear waste by shooting them into space? Why dont you dump it into ocean? It's cheaper!

[Rhaegar1]

probably cheaper but somewhere in the 80's people figured out that there might actually be some donwsides to just dumping it in the environment so now everything is has to be stored.

Shooting nuclear waste into the sun however. Will have no environmental impact and for 500$ a kilo will probably be economically viable