Gigantic Air Gun To Blast Cargo Into Orbit

Hugh Pickens writes: "The New Scientist reports that with a hat tip to Jules Verne's From the Earth to the Moon , physicist John Hunter has outlined the design of a gigantic gun that could slash the cost of putting cargo into orbit. At the Space Investment Summit in Boston last week, Hunter described the design for a 1.1-kilometer-long gun that he says could launch 450-kilogram payloads at 6 kilometers per second. A small rocket engine would then boost the projectile into low-Earth orbit. The gun would cost $500 million to build, says Hunter, but individual launch costs would be lower than current methods. 'We think it's at least a factor of 10 cheaper than anything else,' Hunter says. The gun is based on the SHARP (Super High Altitude Research Project) light gas gun Hunter helped to build in the 1990s while at the Lawrence Livermore National Laboratory (LLNL) in California. With a barrel 47 meters long, it used compressed hydrogen gas to fire projectiles weighing a few kilograms at speeds of up to 3 kilometers per second."

Re:G-forces ????

[Tx]

If you RTA (yes I know, not likely), you'll see that they acknowledge this issue, their intent is to use this for robust cargo only (rocket fuel is given as an example, not e.g. satellites or humans). They also state that ablative heatshields would be necessary to survive atmospheric transit, so wouldn't be a fully reusable vehicle either. Sounds like one for the back burner, as it isn't solving the current launch capability issues.

Re:Starting to get afordable

[mrsquid0]

Only if you want them to arrive on orbit as people paste. The G-forces in a cannon launch would be very high.

Re:nothing new here

[cheesybagel]

explosive materials (fuel) wouldn't be able to be shot up in a gun

Bullshit. Several weapon systems do just that, including the rocket assisted howitzer shells [wikipedia.org] used in the M109 Paladin [wikipedia.org].

TFA, my good sir:

[Eil]

While humans would clearly be killed and conventional satellites crushed by the gun's huge g-forces, it could lift robust payloads such as rocket fuel. Finding cheap ways to transport fuel into space will lower the cost of keeping the International Space Station in orbit, and in future it may be needed to supply a crewed mission to Mars.

Re:G-forces ????

[Hojima]

Just a quick bit of physics review: 1)A=V/t 2)d=.5*A*t^2 now substituting, we get d=.5*(V/t)*t^2=.5*V*t. The distance of the cannon is 1.1, the final velocity is 6, thus the time is about .37s. This would imply an acceleration of about 1670G. So the acceleration due to gravity is essentially multiplied thousands of times. Ever watch DBZ? Yea, well even Goku had a tough time with 100x gravity. Don't see how it will work with anything but raw materials. Any structural entity would be reduced to a density stratum.

Re:Gerald Bull

[Gudeldar]

Bull was killed by Mossad because he was helping Iraq build a "supergun". You make it sound like he was killed because of Project HARP.

Re:Saddam already tried just that

[tomhudson]

Search for Gerald Bull [wikipedia.org] and read abut his super-gun project.

Re:nothing new here

[AJWM]

or explosive materials (fuel)

Fuel isn't explosive. Fuel-oxidizer mixes, or some monopropellants, may be explosive, but are not necessarily shock-sensitive. This would be fine for launching suitably-built canisters of fuel or water, or other insensitive cargoes.

And don't overestimate the sensitivity of some electronics packages -- gun-fired projectiles with electronic fuses are a decades-old technology.

Re:nothing new here

[John Hasler]

> Cargo it seems would have a better chance but any sensitive equipment (like
> 99% of anything used in space) or explosive materials (fuel) wouldn't be able
> to be shot up in a gun.

Nonsense. Guns have been firing projectiles filled with explosives for centuries. The US Army has had shells filled not only with explosives but optics, electronics, and actuators for terminal guidance for dacades. In WWII they had anti-aircraft guns that fired shells with vacuum tube proximity detonators in them. In WWI they used shells with self-winding mechanical timers. Fuel would be easy.

Re:G force.

[John Hasler]

The acceleration is an artillery piece runs to the thousands of Gs. Artillery shells are full of explosives, electronics, and machinery. This gun should be able to handle pretty much all of the consumables and many of the parts and materials needed by the space station.

Re:1670 g

[John Hasler]

Which, given that artillery shells exceed 2000g and are full of explosives, electronics, and machinery, should be easy.

Re:Pumpkins

[kryptKnight]

For those who don't know, the OP is referring to pumpkin chunking [wikipedia.org]. It's a competition to see whose machine can throw a pumpkin the farthest. There are separate categories for catapults, trebuchets and cannons, and there are annual competitions and championships all over the world.

Re:this has real potential...for certain things

[AJWM]

With discrete component electronics you just pot the whole thing in epoxy. I don't know how well that works with integrated circuits -- the point of failure is likely to be the fine wires that connect the chip to the package leads, although those may be light enough that the real concern is vibration rather than steady G force. Even vacuum tubes can be built tough, if they're built small.

But ~400 Gs (per calculations by a poster above) is nothing. The radio proximity fuzes in WW II antiaircraft projectiles didn't use transistors, and had to withstand ~20,000 Gs when fired and ~5,000 Gs of shell spin.

Re:Pumpkins

[Anonymous Coward]

A catapult uses a spring of some sort.

A trebuchet uses a falling weight.

The idea of the long barreled cannon is that it can spread out the acceleration of the object over its travel down the length of the barrel, rather than relying on a short rapid acceleration that would be likely to cause damage.

Re:G-forces ????

[Anonymous Coward]

Next time just use v^2 = u^2 + 2 * a * s and you don't need to calculate the launch time first.

Re:Gravity

[John Hasler]

It saves a great deal of fuel by getting the rocket needed to achieve the remaining velocity going 3km/sec and above the atmosphere.

Re:Why gas?

[Digestromath]

Extreme heat and magnetic forces would make it harder on the payload. Ultra high energy railguns usually need to have thier rails replaced everyfiring. Add in the complexity of, no doubt, hundreds of massive capicitors, it would be like the LHC.

Re:1670 g

[Anonymous Coward]

http://www.globalsecurity.org/military/systems/munitions/ergm.htm

Re:G-forces ????

[Anonymous Coward]

What are the power requirements for such a mechanism?

You can't break the laws of physics, no matter how much power you apply.

Why not make it longer for smaller accelerations?

Because the acceleration for 1.1km is 1670 g and scales like length^(-1) so you'd need it 200x longer to get down to still 8.35 g.

Aside, what happens to fuel (liquid and solid) under such high g-load? I can find no studies on it.

Why do you care, they're going to use "inertia canceling", right?

P.S. I am an Aerospace Engineer.

Make sure you don't work on anything other than fluid flow.

Re:G-forces ????

[sjames]

It's not even 1 Km^2 total, even if the final pressure in the tube was 3000 atm. Certainly not enough to change the weather.

The beauty of the system is it's very simple which translates to inexpensive (for something of that scale anyway). The engine for orbit is based mostly on the need to take the most direct practical path out of the atmosphere rather than start out on an orbital trajectory.

I'm thinking it'll be a solid fuel engine to withstand the launch stresses and to be inexpensive and reliable.

The idea is to avoid costly precision. Just shoot it up there, track it's orbit and go get it. (yeah, not quite THAT simple...)

Comment removed

[account_deleted]

Comment removed based on user account deletion

Re:G-forces ????

[edremy]

You'd be surprised what will survive insane accelerations. G-hardening electronics is a solved problem- witness the Army's Copperhead artillery shell [wikipedia.org]. Looking at the speed and barrel length, Copperhead undergoes *much* higher acceleration- 6km/sec over 1100 meters vs. ~1km/sec in about 4 meters. Back when I was in Armor, the DOD was looking at active electronics on tank rounds, and those hit 1.5km/sec in about 3 meters.

You won't ride to orbit on this, but there's lots of stuff that doesn't have to worry about being pulped on launch.

Re:G-forces ????

[dbIII]

What are the power requirements for such a mechanism?

Truckloads to compress all of that gas.

Why not make it longer for smaller accelerations?

The idea of these gas guns is to have them long enough to get things going at close to the wave speed of the gas. They are so simple that a "valve" is a thin sheet of steel with an X scribed on it to make sure it bursts in the right spot to supply the shock wave. You don't get gentle acceleration with such a device.
I'm no aerospace engineer (materials science and engineering turned computer wrangler) but it doesn't take one to play with these multi-stage gas guns. Of course designing the cutting edge ones to go fast on a low budget did involve leading aerospace engineers like Ray Stalker. Many smaller ones were designed pretty well the same way you would design a pressure vessel and a really big air rifle (not by me but I looked at the drawings). I used one to effectively explosive weld mixtures of metal power into solid objects. The physics is not tricky at all in the gas gun since you are dealing with single shock waves at known velocities in a single dimension (ie. up or down). We used an Apple ][ with an interface card to a couple of light sensors to measure the velocity of projectiles in the thing.

Re:Short-term Project

[bill_mcgonigle]

Considering we just hit the Moon to try to figure out how much water ice is there, it seems unlikely that we have any good ideas on which asteroids have water ice in them

Some progress on that front:
http://www.usnews.com/science/articles/2009/10/08/ice-confirmed-on-an-asteroid.html [usnews.com]

much less the ability to bring them to where we need them (yet)

Yeah, I think smart folks feel it's a pretty straight-forward, if slow, proposition, but we'd have to still design and build the actual devices. Heck, convincing the populace that the rocket scientists wouldn't crash the asteroid into Earth is probably the hardest part.

That's more the type of project I'd expect a few decades _after_ we do what this project is talking about. All in good time, my friend...

Agreed. :) This kind of air gun could be a good way to bridge the gap.

Re:I See. Yet Another Cockamamie Scheme...

[TapeCutter]

I don't know about the GP but I only needed one look. Do you realise you have reinvented Luminiferous ether [wikipedia.org]?