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The Science Behind Building a Space Gun

samzenpus posted about a year ago | from the acme-approved dept.

Space 131

An anonymous reader writes "Astronomer and gamer Scott Manley (more famous for his Kerbal Space program coverage) has created a fantastic video explaining the science behind building guns that could one day be used to launch payloads into space. It's not as easy as simply making a bigger gun, there's a whole host of unorthodox 'gun' designs which work around the limitations of garden variety propellants."

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131 comments

I estimate it will be about a week (3, Insightful)

Anonymous Coward | about a year ago | (#42554287)

before the Mossad kills this guy...

Re:I estimate it will be about a week (5, Interesting)

Anonymous Coward | about a year ago | (#42554367)

LOL no kidding. Paging Dr Gerald Bull!

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

Re:I estimate it will be about a week (3, Interesting)

F34nor (321515) | about a year ago | (#42554603)

The bones of the space gun are rusting in the Bahamas. The biggest problem is A LOT OF MOTHERFUCKING Gs. That's why I say we just launch barrels of water.

Revive the lofstrom loop! (3, Interesting)

Cryacin (657549) | about a year ago | (#42554657)

http://en.wikipedia.org/wiki/Launch_loop [wikipedia.org]

Much better than a cannon, and finally a place where we can put all of that electricity from our power plants that we don't use during trough times to be used again when you get a spike. Just gloss over the energy of a small nuclear device in a moving cable over a 2000km area bit. That's not going to bother anyone...

Re:I estimate it will be about a week (2, Interesting)

pla (258480) | about a year ago | (#42556221)

Mod parent up (odd, I had a ton of points yesterday but none today).

Gerald Bull [www.cbc.ca] solved this problem 20-30 years ago. He even offered it to America, and we told him to kindly go fuck himself, so he did his work in Canada (actually right on the border, with his campus straddling both sides of the border).

Then the Jews decided he didn't deserve to continue living, so they sent a team of assassins to another sovereign country (without permission from that country) to kill him.

Hmm, violating national sovereignty to assassinate scientists... Where have I heard that before? [wsws.org]. Oh, right... Looks like pretty standard operating procedure for our bestest buds in the world, killing geeks.

he was sort of asking for it (3, Insightful)

Thud457 (234763) | about a year ago | (#42556957)

Really?!
The Israelis are bad for killing the guy that was going to give Saddam a GIANT GODDAMNED GUN to lob poison gas shells at Tel Aviv ?!!

Bull was pulling a Von Braun and just didn't have the luck of getting a buyout offer at the end.

Re:he was sort of asking for it (1)

smooth wombat (796938) | about a year ago | (#42557223)

If it's acceptable for one country, or two or three, to claim the right of self defense to go after someone who they think might be a threat to them, that country has no right to complain when another country, or group, does the same.

You can't claim you're always being picked on when you're the one doing the bullying.

Re:he was sort of asking for it (1)

JTsyo (1338447) | about a year ago | (#42558847)

To add to this, the gun was build into the side of a hill. It could only fire in one direction. Guess which country would be on the receiving end.

Re:I estimate it will be about a week (0)

Anonymous Coward | about a year ago | (#42554979)

I am guessing that you are refering to Gerald Bull.

Re:I estimate it will be about a week (-1)

Anonymous Coward | about a year ago | (#42555135)

Like they did all those poor little Sandy Hook kids in school...

Obligatory (5, Interesting)

Kylon99 (2430624) | about a year ago | (#42554377)

In honor of the time before xkcd, but in the style of such:

http://en.wikipedia.org/wiki/From_the_Earth_to_the_Moon [wikipedia.org]

Fucking Slashdot (-1)

Anonymous Coward | about a year ago | (#42554641)

Turn in your nerd cards. All of you. A space gun only gets you one of the two burns needed. You still have to loft the rocket and enough fuel for the insertion burn. This only buys you a fraction of the energy. Hell, even Pegasus the winged rocket is a better approach than a space gun.

ignorant (2)

rubycodez (864176) | about a year ago | (#42554785)

you turn in your geek card. in a multi-body system, such as the earth-moon one, there ARE trajectories to orbit from a "space gun"

Re:ignorant (2)

dotancohen (1015143) | about a year ago | (#42555567)

In a multi-body system there do exist balistic trajectories from one body which do not intersect either body again. However, the moon is too small and too distant to provide the effect from Earth. Conversely, I do believe that such trajectories could exist from the moon.

Re:ignorant (0)

Anonymous Coward | about a year ago | (#42557171)

In a multi-body system there do exist balistic trajectories from one body which do not intersect either body again. However, the moon is too small and too distant to provide the effect from Earth. Conversely, I do believe that such trajectories could exist from the moon.

You're completely forgetting that such trajectories exist even in a single-body system. It's called an escape trajectory :P

Re:ignorant (2)

egcagrac0 (1410377) | about a year ago | (#42556695)

Maybe the orbit that's directly reachable from the space-gun isn't where you want your spacecraft to go.

It's a lot easier to move the satellite than the gun. (Operation of a space-gun sort of depends on this.)

HOW TO DODGE A SPEED-OF-LIGHT LASER BLAST !! (-1)

Anonymous Coward | about a year ago | (#42554387)

Well, how do they do it ?? Does the next Star Trek NOT have actors dodging phaser blasts ??

Think of all the SPACE-themed shows over the years !! How many used bullets ?? Too many !! Starship Troopers. Space: Above and Beyond. Alienses.

Re:HOW TO DODGE A SPEED-OF-LIGHT LASER BLAST !! (1)

khallow (566160) | about a year ago | (#42554967)

Well, how do they do it ?? Does the next Star Trek NOT have actors dodging phaser blasts ??

How do people in the real world dodge really fast things like bullets now? By not being in the path of the weapon when it fires.

Of course, by the time of Star Trek, phasers should be able to automatically lock on the target in real time and hit it, no matter how the target dodges.

Re:HOW TO DODGE A SPEED-OF-LIGHT LASER BLAST !! (1)

egcagrac0 (1410377) | about a year ago | (#42556929)

Of course, by the time of Star Trek, phasers should be able to automatically lock on the target in real time and hit it, no matter how the target dodges.

So why do the crew keep practicing their aim [memory-alpha.org]?

I think it's called a mass driver (3, Interesting)

Joe_Dragon (2206452) | about a year ago | (#42554417)

I think it's called a mass driver

Re:I think it's called a mass driver (3, Informative)

roc97007 (608802) | about a year ago | (#42554437)

Some of the techniques resemble a mass driver, but many do not. It's actually an interesting video.

Re:I think it's called a mass driver (1)

JoshuaZ (1134087) | about a year ago | (#42554713)

Generally, the term "mass driver" used to mean electromagnetically accelerated launch systems. Most of these proposals use explosive power. Essentially, this sort of proposal essentially resembles 19th century/early 20th century suggestions for going into space.

Re:I think it's called a mass driver (1)

alexander_686 (957440) | about a year ago | (#42554791)

The article does mention mass drivers – it’s under the coil or rail gun section – and he does admit that he gives them short shrift – maybe to be followed up.

Re:I think it's called a mass driver (3, Insightful)

Grayhand (2610049) | about a year ago | (#42554947)

I think it's called a mass driver

By any other name the gee force issues are the same. The problem with mass drivers would be the expense. Imagine building a 500 kilometer CERN collider. Mass drivers are practical on the Moon because of the low gravity and no atmosphere.

Re:I think it's called a mass driver (2)

marcello_dl (667940) | about a year ago | (#42555911)

> Imagine building a 500 kilometer CERN collider.

That doesn't sound particularly difficult.

After all, somebody imagined a 750 km tunnel [slashdot.org] between CERN and Gran Sasso for neutrinos that go faster than light.

I will concede that the "building" phase is delicate, though.

Hasn't this been done already? (1)

bigkahunah (1093791) | about a year ago | (#42554447)

They had this technology at the turn of the previous century as shown here: http://www.youtube.com/watch?v=7JDaOOw0MEE [youtube.com]

Re:Hasn't this been done already? (2, Interesting)

Anonymous Coward | about a year ago | (#42554493)

they have, but it's impractical as in taking up airspace which causes it to act like a wall in the sky preventing airplanes to pass through.
it's easier and cheaper to just build a space elevator in the long run.

it's not economically interesting to prevent airplane traffic.

This is all well and good, but... (1, Insightful)

Anonymous Coward | about a year ago | (#42554469)

We know even vacuum tubes can withstand the 100000G acceleration and 20000RPM rotation from being fired out of a WWII cannon.

http://en.wikipedia.org/wiki/Proximity_fuze [wikipedia.org]

But for what else can you use this gun? We already have plenty of electronic junk up there and it's made its way there just fine without a gun.

This is probably a case of "it's time to revive a decades-old idea to make a name for myself"...

Re:This is all well and good, but... (1)

Anonymous Coward | about a year ago | (#42554531)

We already have plenty of electronic junk up there and it's made its way there just fine without a gun.

No it made it up there by burning butt loads of cash. A space gun would be orders cheaper which is the point.

Re:This is all well and good, but... (-1)

Anonymous Coward | about a year ago | (#42554567)

Yes, so now please redesign all our fragile space tech to be able to withstand that. The WWII fuze took years of wartime effort, and its ultimate goal was to blow up a few seconds after being fired...

The money you think you save will be more than eaten up by the fact that you'll have to redesign every. single. component. and. process. for no real improvement at all, plus the fun zoning you'll need for the noise ... Rockets are loud but a cannon? It's like being pushed by a supersonic mattress.

Besides, I always thought the pro-space argument was that fuel was the least expensive part of a rocket...

Re:This is all well and good, but... (4, Insightful)

F34nor (321515) | about a year ago | (#42554725)

Everything is expensive. As to what to do with a gun, just launch water into space. It provides fuel, air, food, and of course water.

Re:This is all well and good, but... (-1)

Anonymous Coward | about a year ago | (#42556161)

Water does all that by itself? Or do you need a whole bunch of magical technology to do so? And before you answer, THINK.

Re:This is all well and good, but... (2)

MozeeToby (1163751) | about a year ago | (#42556825)

a whole bunch of magical technology to do so?

You mean an electrolysis tank and a power source? Ok, granted there's some engineering to do there but considering the kinds of engineering that would go into building a spacecraft, it's a pretty trivial amount.

Re:This is all well and good, but... (1)

chihowa (366380) | about a year ago | (#42558807)

a whole bunch of magical technology to do so?

You mean an electrolysis tank and a power source? Ok, granted there's some engineering to do there but considering the kinds of engineering that would go into building a spacecraft, it's a pretty trivial amount.

Screw the power source. Panels and reactors are light enough to get up there through traditional means (and with fewer Gs and less chance of damage to them). The water is the heavy part. Just lob tanks of water up there, one after another, and capture them in orbit.

Re:This is all well and good, but... (1)

Anonymous Coward | about a year ago | (#42555695)

But for what else can you use this gun? We already have plenty of electronic junk up there and it's made its way there just fine without a gun.

Bricks & mortar, figuratively speaking, i.e. batches of construction elements for building structures in space, batches of radiation-shielding materials, in other words anything non-fragile and in bulk.

Re:This is all well and good, but... (1)

egcagrac0 (1410377) | about a year ago | (#42557035)

The article you linked says

Major problems included microphonic difficulties and tube failures attributed to vibration and acceleration in gun projectiles. The T-3 fuze had a 52% success against a water target when tested in January, 1942

52% success rate is pretty bad when the bullet is expensive, like many spacecraft are.

These are the same proximity fuzes that kept the acid for the battery that powered them in a glass vial which would shatter on firing, activating the battery just before it was used... right?

Also, I'm pretty sure that they had to use extremely ruggedized tubes - metal housings, and larger internal wires to keep the thing from self destructing or deforming to the point of non-operation. These are not likely to be thin-walled glass envelope vacuum tubes, as would be used in household radios and televisions.

Scaled Down Particle Accelerator (4, Interesting)

dns_server (696283) | about a year ago | (#42554549)

Why not scale down the LHC and build something that is capable of accelerating something relatively small say 10-100kg fast enough to make it to orbit instead of accelerating atoms to nearly the speed of light.

The problem with conventional rockets is you need to carry the fuel to get in to orbit as well as the fuel to go where you need to. The bigger the ship the more fuel you need to carry to overcome the weight of the fuel.

If you can split the carrying of fuel for your journey from getting your rocket in to orbit you would not need to waste as much fuel lifting itself.

You could set up an automated system that would fire a 10kg payload of fuel every 10 minutes and get what you need over time far cheaper than one big launch.

Re:Scaled Down Particle Accelerator (3, Insightful)

crtlaptop (1923984) | about a year ago | (#42554635)

Orbital speeds in atmosphere means bleeding off speed and part of the payload being vaporized. Its the same forces acting on re-entry. As far as I know (not very far) this makes it harder to send smaller objects.

Re:Scaled Down Particle Accelerator (0)

Anonymous Coward | about a year ago | (#42554679)

You would also need some form of propulsion to put the payload into its final orbit. However, lobbing loads of a few thousand kilos should be fairly cost-effective and simple.

Re:Scaled Down Particle Accelerator (1)

Anonymous Coward | about a year ago | (#42555775)

Orbital speeds in atmosphere means bleeding off speed and part of the payload being vaporized. Its the same forces acting on re-entry.

True. Even worse, you have to start with speed much higher then terminal velocity in the thickest part of atmosphere. Unlike in re-entry, we don't want any atmospheric braking action on the capsule. We would probably have to invent an analogue to supercavitation [wikipedia.org] in air - some means of clearing the path in front and on sides of it.

Re:Scaled Down Particle Accelerator (0)

Anonymous Coward | about a year ago | (#42554659)

See http://en.wikipedia.org/wiki/Linear_particle_accelerator

>The particle source. The design of the source depends on the particle that is being moved. Electrons are generated by a cold cathode, a hot cathode, a photocathode, or radio frequency (RF) ion sources. Protons are generated in an ion source, which can have many different designs. If heavier particles are to be accelerated, (e.g., uranium ions), a specialized ion source is needed.

The technology relies on charge particle and cannot be used for anything that are bigger than particles. It is fine for shooting subatomic particles by subjecting them to high electric fields or radio waves, but it does not work for anything bigger.

I am not sure WHO in the right minds up voted the GP of this.

Re:Scaled Down Particle Accelerator (2, Informative)

Anonymous Coward | about a year ago | (#42554823)

Why not scale down the LHC and build something that is capable of accelerating something relatively small say 10-100kg fast enough to make it to orbit instead of accelerating atoms to nearly the speed of light.

Accelerating charged particles and accelerating something more complex, like a 10kg payload, are in a completely different ballpark, unless you're happy with send particles into orbit.

Also, each of the protons in the LHC's beam have about as much energy as a fast baseball.

LHC's beam is NOWHERE near that energetic (2)

PeterM from Berkeley (15510) | about a year ago | (#42555981)

A baseball, per google search, weighs about .142kg and a 120mph baseball is going about 53m/s.

0.5 * mass * velocity^2 gives about 200J.

200J / 1.6e-19 gives around 1.24 x 10^21 eV.

The LHC's protons top out at around 7TeV, or 7 x 10^12.

Your estimate of the LHC's proton energy, sir, is off by a factor of something like 1.78 x 10^8, or in words, by a factor of 178 million, depending on what you think of as a "fast" baseball! (Unless you think of a baseball moving at .009mph as fast?)

Perhaps you were thinking of some cosmic rays, which are reputed to have that much energy? There are cosmic rays that have had 50J of energy, or about energy of a 60mph baseball. But the LHC has about a factor of 10 million to go to reach that class of energy!

--PM

Re:LHC's beam is NOWHERE near that energetic (0)

Anonymous Coward | about a year ago | (#42556315)

The GP might also have been confused (or read a news story from a confused reporter) about the difference between the energy per proton in the LHC, and the total energy in the LHC beam. The LHC accelerates many protons at once, divided into bunches of 10^11 or so protons.

The energy per bunch is 7 TeV x 10^11 = 112 kJ. Drat - that's too high to fit with the GP's baseball estimate.

Other possible sources of confusion include the difference between the energy the LHC achieves with protons versus with heavy nuclei (which is about 100x higher), and the energy of the protons in the lab reference frame versus the reference frame of the opposing beam of protons (which is the relevant energy for comparing with cosmic rays, in terms of the sort of physics that can happen).

This is all irrelevant, in any case, if we're talking about using a LHC-analogue as a space launcher. Those bunches of 10^11 protons are about as many protons as you can stick together without their electric repulsion pushing the bunch apart. That's 1.6 x 10^-17 kg of protons. If you try to launch more than this many pure protons at once, you'll fail - and if you mix with electrons (as in regular matter), then it won't have a sufficient charge-to-mass ratio to follow the magnetic field around the ring of the accelerator.

Re:LHC's beam is NOWHERE near that energetic (0)

Anonymous Coward | about a year ago | (#42556689)

The standard measure of the energy of a single proton in the LHC is comparable to a mosquito bumping into you. http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/lhc_glossary.htm

Re:Scaled Down Particle Accelerator (3, Informative)

Grayhand (2610049) | about a year ago | (#42555049)

It's the g-force involved. The benefit of a long barrel is lower g-forces. A short barrel would be possible but when you start talking a million Gs the only thing that could survive would be solid metals. It's a balancing act of barrel length as opposed to G-Forces involved. There's nothing special about how the LHC is built, magnets or explosives it's still converting energy into motion. Most gun launch systems plan on using explosives to cut costs. Explosives are cheap, magnets and electricity are expensive. If you could do it efficiently one gallon of gasoline would orbit a couple of kilos. The trick is not wasting the energy. As the projectile moves down the barrel the gas expands exhausting it's energy. Say you have a mile long barrel you'd likely run out of gas expansion before you reached the end then add in friction and a projectile that could reach orbit doesn't even make it a mile. Instead burn a cup of vaporized gasoline spaced out every ten feet along the barrel and you might need a few hundred gallons of gas to reach orbit but it's still dirt cheap. Watch the video and he explains why that wouldn't work either. The real solution is lower density gases like hydrogen that have a higher Mach speed. The best bet is watch the video. It's one of the best I've ever seen and explains the problems in laymen's terms.

Re:Scaled Down Particle Accelerator (0)

Anonymous Coward | about a year ago | (#42558307)

A rocket has even lower g forces as it gets to accelerate all the way to orbit instead of whatever the length of the barrel one can build.

Gun barrels have NOTHING to do with particle accelerators.

Re:Scaled Down Particle Accelerator (1)

DerekLyons (302214) | about a year ago | (#42555331)

If you can split the carrying of fuel for your journey from getting your rocket in to orbit you would not need to waste as much fuel lifting itself.

You spend the same amount of energy either way. (Probably more given massive losses to atmospheric drag such schemes suffer from.) TANSTAAFL.

Not that it makes much sense to spend more than the most miniscule of effort to avoid "wasting" fuel. Fuel is cheap, and the cost is all but lost in the noise at current launch costs. (It cost something like a million dollars to fill the Shuttle's external tanks...) Launcher costs scale only weakly with size - and very strongly with complexity. So if you want to reduce launcher costs, complexity is where you start. (Which is a huge part of how SpaceX has reduced launch costs.)
 

You could set up an automated system that would fire a 10kg payload of fuel every 10 minutes and get what you need over time far cheaper than one big launch.

That's the theory. It breaks down when it encounters reality... It's the equivalent of pouring the foundation for a 1500ft skyscraper by using armies of messengers on motor scooters, each carrying a bucket of cement, because motor scooters are cheaper than cement trucks. It actually ends up being *more* expensive and taking longer because of the increased labor, increased fuel, increased planning and management... not to mention the traffic jams at the receiving end. There's a reason why bulk goods are transported in bulk - it's cheaper, easier, and more efficient to do so.

Re:Scaled Down Particle Accelerator (1)

sFurbo (1361249) | about a year ago | (#42555401)

You spend the same amount of energy either way. (Probably more given massive losses to atmospheric drag such schemes suffer from.)

Yes and no. To lift a kg of matter into orbit, and to accelerate it to keep that orbit, you need a certain amount of energy. But this is only a small fraction of the energy an rocket uses [xkcd.com] to do this, because the rocket needs to accelerate all the fuel it is going to use later. So if you could accelrate the rocket before turning it on, you might save quite a lot of fuel.

Re:Scaled Down Particle Accelerator (1)

rich_hudds (1360617) | about a year ago | (#42556555)

Why not use a gun to fire fuel to a rocket then?

If you fired the gun every few seconds you wouldn't have the expense of lifting all of the fuel right from the start.

You'd just need the rocket to have some way of catching the fuel. Bit tricky admittedly.

Re:Scaled Down Particle Accelerator (1)

CaptSlaq (1491233) | about a year ago | (#42556775)

Why not use a gun to fire fuel to a rocket then? If you fired the gun every few seconds you wouldn't have the expense of lifting all of the fuel right from the start. You'd just need the rocket to have some way of catching the fuel. Bit tricky admittedly.

Some would say this is already being done with laser launch systems.

Re:Scaled Down Particle Accelerator (1)

DerekLyons (302214) | about a year ago | (#42556887)

Which part of "it's stupid to spend a lot of money to save fuel because fuel is so cheap" did you fail to comprehend? Pedantic parroting of things you only understand because someone reduced it to your level by producing a cartoon does not contribute usefully to the discussion.

Re:Scaled Down Particle Accelerator (1)

Lithdren (605362) | about a year ago | (#42558311)

Every now and then I see posts like this and wonder why someone with that kind of an anger issue is allowed anywhere near a computer.

Chill out.

Re:Scaled Down Particle Accelerator (0)

Anonymous Coward | about a year ago | (#42555359)

The required radius of a particle accelerator like the LHC is determined by a few things: the velocity you want the particles to reach, their charge/mass ratio, and the strength of the magnetic field that you can generate. If you're trying to use a similar system to put something in orbit, you can use a much lower target velocity, which lets you scale it down, all else being equal. But all else isn't equal: bulk matter (like your payload) is uncharged, and if you try to give it a charge of a billionth of a billionth of an equal mass of protons, the electrostatic repulsion would tear it apart.

So, it's a no-go. To use a cyclotron to put stuff into orbit, you'd need to scale it *up* - and by a factor of billions.

Re:Scaled Down Particle Accelerator (0)

Anonymous Coward | about a year ago | (#42555379)

1% of the speed of light ~3'000'000 m/s
Escape velocity ~ 11'000 m/s
-- Factor: ~270
Number of atoms in a virus ~600'000'000 ( http://answers.yahoo.com/question/index?qid=20060826150954AASGjhh )
-- Factor: ~2'200'000

So if we break up a virus into individual packages, we could get it into orbit in only two million shots (give or take). ... or were you joking?

Sea Water (0)

Anonymous Coward | about a year ago | (#42554587)

There was a design on the inter tubes that I can never re-find that used a giant tube in the ocean and a couple valves to make a space gun. Very cool.

Space Fountain. (1)

F34nor (321515) | about a year ago | (#42554595)

Use a particle accelerator to impart lift to a building. A space elevator without super materials.

Dr. Manley (3, Funny)

crtlaptop (1923984) | about a year ago | (#42554661)

Oh Scott Manley. I wish you had gotten your PhD. Dr. Manly would be pretty much the best name ever. You could say you have a PhD in Manlyness.

Re:Dr. Manley (0)

Anonymous Coward | about a year ago | (#42557601)

Nope. Sir Manley Power is the best name ever.

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

Re:Dr. Manley (0)

Anonymous Coward | about a year ago | (#42559947)

You've clearly never heard of this guy: http://www.af.mil/information/bios/bio.asp?bioID=6233
He used to be a Major General, giving rise to the name Major General Lord. /. interviewed him once here http://interviews.slashdot.org/story/08/02/29/1733222/ask-the-air-force-cyber-command-general-about-war-in-cyberspace

Submerged Gun in Marianas Trench OK for humans (2)

PerMolestiasEruditio (1118269) | about a year ago | (#42554715)

Marianas trench is 11km deep. A neutrally bouyant gun barrel inclined at about 20 gives a barrel length of 30km and is relatively cheap to build (a couple of billion for a few meters diameter).

If you immerse the astronauts in water (body hugging 'bath') they can easily withstand 10-20g for 15-30 seconds. That gives you 2.5-3.5km/s muzzle velocity, and a relatively simple rocket to prvodie the additional 5-6km/s - similar to current rocket second stages.

The gun can also be used at higher g to launch inert payload to orbital speeds without less rocket propulsion.

Guns are ok for lower speeds (up to perhaps 2-3km/s) but ram - accelrators are better than light gas guns for higher speeds.

Re:Submerged Gun in Marianas Trench OK for humans (1)

camperdave (969942) | about a year ago | (#42554793)

SpaceX can launch your people into orbit for $50 million. Why would you spend billions on a gun?

Re:Submerged Gun in Marianas Trench OK for humans (2)

Kell Bengal (711123) | about a year ago | (#42555409)

Because it only takes 20 or more launches to make a $1B space gun competitive with a $50M rocket.

Re:Submerged Gun in Marianas Trench OK for humans (0)

Anonymous Coward | about a year ago | (#42557515)

... assuming zero operational costs, and assuming your gun survives for 20 launches when all it's critical bits are 20,000 feet or more below sea level, and where the pressure is enough to squeeze submersibles so much that they literally shrink by inches.

Reality deprivation happens a lot here (0)

dbIII (701233) | about a year ago | (#42555585)

"Say they could" does not equal "can".
They've got a long way to go before they can prove it.

Re:Reality deprivation happens a lot here (1)

camperdave (969942) | about a year ago | (#42557153)

"Say they could" does not equal "can". They've got a long way to go before they can prove it.

No they don't. They've already shown they can launch a Dragon, dock it with the ISS, and return safely. The only thing they need to do a manned flight is stick in some seats and an oxygen tank. Granted, it may not be "man rated" yet, but it is not a long way to go.

Inexpensive way to send up inert objects (3, Insightful)

steveha (103154) | about a year ago | (#42554751)

This would be ideal for sending inert things like oxygen, water, rocket fuel, or some kinds of food. It would even work for structural parts or electronics if they could take the accelerations without damage.

For that matter, one of the problems of a Mars flight is having adequate shielding against the radiation the craft would encounter between Earth and Mars. With a system like this, the cost of getting the shielding up would be as cheap as possible. (I guess the mass of the shielding would affect the accelerations the craft could make and thus affect the length of the trip.)

One problem, as I understand it: a projectile launched from a big space gun would need to have its orbit adjusted or it will return to Earth. Either you need to catch it while in orbit (you get one chance) and add additional acceleration to put it in a stable orbit, or else the projectile needs to have rockets or something to adjust its speed. The video mentioned this issue briefly (the part about Newton figuring out that the projectile would return to the point of launch if no other forces acted upon it).

P.S. I saw proposals for an Apollo-style mission from Earth to Mars: a single giant rocket launches everything in one launch. Why is anyone even looking at doing it that way? Send the craft to space without fuel or consumables; send it up in parts even and assemble it in space. Then, as it is in orbit, fuel it up, load it with consumables, and then when it is ready send it on its way.

We don't really need giant space guns to make space access more affordable; we just need practical, reusable craft that can carry a small load to orbit, return, and do it again soon. It must not need man-decades of work to completely overhaul it, as the Space Shuttle needed. Single stage to orbit, two stage to orbit, whatever... but not single-use rockets. Rockets that fall into pieces as they ascend, where you never get a test flight because each flight uses up one rocket, will never give us cheap access to space.

According to Jerry Pournelle, the fuel cost of putting something into orbit is similar to the cost of flying it most of the way around the world on an aircraft. Because the aircraft isn't consumed by the flight, we can do this for much less than the cost of sending something into orbit. Practical, reusable transportation would be a total game-changer.

Re:Inexpensive way to send up inert objects (3, Informative)

currently_awake (1248758) | about a year ago | (#42554955)

Reusable rockets must be fully overhauled after every single flight and must be more rugged to survive repeated use, they therefore cost more than a disposable rocket. The Saturn 5 was much cheaper than the space shuttle. Using chemical fuels means 95% of the rocket must be fuel. To get usable launch weights you have to use every trick in the book to save weight. All those weight savings make rockets fragile, they wear out quickly and need everything rebuilt after each flight. The only way to make space cheap is by having the power source separate from the rocket/payload (gun, mass driver, loop, skyhook, tractor beam).

Re:Inexpensive way to send up inert objects (0)

Anonymous Coward | about a year ago | (#42555215)

Sure, that's the current state of the art. But saying something can't be done because we don't know how to do it now... well, that's not how progress works (though you would certainly be in good company going back hundreds of years.)

Re:Inexpensive way to send up inert objects (4, Interesting)

DerekLyons (302214) | about a year ago | (#42555009)

One problem, as I understand it: a projectile launched from a big space gun would need to have its orbit adjusted or it will return to Earth. The video mentioned this issue briefly

All gun schemes mention this 'briefly', if they mention it at all (most don't) - mostly in hopes that nobody will notice. The mass of the engines and fuel needed to circularize the orbit dominates the payload, and is *very* difficult to make resistant to the shock and acceleration. It's pretty much a showstopper all by itself, without even mentioning the need for (the currently non-existent) heat shielding needed to protect the payload on ascent. As the vehicle bleeds off energy to atmospheric drag and gravitational forces as it coasts upward, it has to leave the muzzle of the gun at considerably more than orbital velocity... essentialy exposing the payload to re-entry conditions at launch.
 

P.S. I saw proposals for an Apollo-style mission from Earth to Mars: a single giant rocket launches everything in one launch. Why is anyone even looking at doing it that way?

Nobody that I'm aware that's even remotely serious is proposing to do it that way.

Re:Inexpensive way to send up inert objects (1)

tibit (1762298) | about a year ago | (#42555427)

And this is the post that should be ending the silly discussion prompted by the article...

Re:Inexpensive way to send up inert objects (1)

steveha (103154) | about a year ago | (#42555571)

As the vehicle bleeds off energy to atmospheric drag and gravitational forces as it coasts upward, it has to leave the muzzle of the gun at considerably more than orbital velocity... essentialy exposing the payload to re-entry conditions at launch.

The video discusses this point. He really did cover all the bases.

Nobody that I'm aware that's even remotely serious is proposing to do [an Apollo-style mission to Mars]

NASA seems to be at least remotely serious about this mission, an Apollo-style launch. It's not a manned launch (even though Wikipedia seems to report that it is). The plan seems to be that astronauts would rendezvous with the sample return package, but astronauts would not ride this thing to Mars and back. Still, the sample-return mission is indeed an Apollo-style mission: everything launches on a single heavy lift rocket.

http://www.nasaspaceflight.com/2012/11/nasa-interest-2024-mars-sample-return-sls-orion/ [nasaspaceflight.com]

I'm pretty sure I saw some newspaper article about a manned mission done with a single launch, but perhaps I was mistaken.

Re:Inexpensive way to send up inert objects (1)

chihowa (366380) | about a year ago | (#42558943)

One problem, as I understand it: a projectile launched from a big space gun would need to have its orbit adjusted or it will return to Earth. The video mentioned this issue briefly

All gun schemes mention this 'briefly', if they mention it at all (most don't) - mostly in hopes that nobody will notice. The mass of the engines and fuel needed to circularize the orbit dominates the payload, and is *very* difficult to make resistant to the shock and acceleration. It's pretty much a showstopper all by itself, without even mentioning the need for (the currently non-existent) heat shielding needed to protect the payload on ascent. As the vehicle bleeds off energy to atmospheric drag and gravitational forces as it coasts upward, it has to leave the muzzle of the gun at considerably more than orbital velocity... essentialy exposing the payload to re-entry conditions at launch.

That's a feature, not a bug. A layer of heat shielding would cover the nose of the projectile, allowing it to survive ascent. During ascent, however, the shield would be ablated. If the projectile is not captured before it deorbits, it vaporizes on reentry.

After the construction of the gun, each launch is relatively cheap. The high G forces experienced by the payload would exclude using a gun for fragile materials. It's a perfect system for putting lots of dead mass into orbit cheaply, though (water, soil, construction supplies).

Re:Inexpensive way to send up inert objects (1)

danhaas (891773) | about a year ago | (#42559653)

The necessity of momentum to circularize the orbit is clear if your model consists of only the Earth and the satellite, but I wonder if the gravitational pull of the moon could be used.
What if we could shoot something up to a Lagrange point? Would we still need engines in our satellite?

Re:Inexpensive way to send up inert objects (0)

Anonymous Coward | about a year ago | (#42555375)

One problem, as I understand it: a projectile launched from a big space gun would need to have its orbit adjusted or it will return to Earth.

A small correction to this: if you launch an object at less than escape velocity, then it will be in an orbit that will eventually intersect the Earth again. If you launch it at greater than escape velocity, it's not in an orbit: it escapes the Earth entirely.

Why is anyone even looking at doing it that way? Send the craft to space without fuel or consumables; send it up in parts even and assemble it in space.

That doesn't necessarily save you anything: you still need to put the same amount of material in space whether you send it up as one big load or lots of little loads. The question is whether the greater efficiency of a single large launcher is better or worse than the improved economy of manufacturing lots of little launchers on a production line.

Re:Inexpensive way to send up inert objects (1)

tibit (1762298) | about a year ago | (#42555433)

If you launch it from a terrestrial gun, the launch velocity hasn't got much to do with velocity out of the atmosphere.

Re:Inexpensive way to send up inert objects (1)

jklovanc (1603149) | about a year ago | (#42555481)

An issue with reusable launch vehicles is that, due to the stresses of launch, parts have a tendency to bend and break. It can be quite difficult to find and diagnose these issues. Things can even become fuses and need to be replaced. It is quite similar to a drag racer. After each run the entire engine is re-built and they don't last many runs. One can build an item much lighter if it is tuned to almost destroy itself while doing it's job. A single use rocket has to hold itself together just long enough to get it's payload into orbit. A reusable vehicle must survive the stresses of getting to orbit, Survive the heat and stresses of reentry. Then land safely all with as little damage as possible so the whole vehicle need not be re-built.

Moon mining return system (1)

GodfatherofSoul (174979) | about a year ago | (#42554939)

This would work best as a system to return mined materials back to Earth.

Re:Moon mining return system (1)

Macgrrl (762836) | about a year ago | (#42555035)

This would work best as a system to return mined materials back to Earth.

As used in The Moon is a Harsh Mistress by Heinlein.

Just don't let Mike share his AI code with Watson [slashdot.org], he already has a sufficiently interesting sense of humour.

Re:Moon mining return system (1)

idontgno (624372) | about a year ago | (#42559229)

That's be juuuuust great. Watson taunting us from Moonbase 1 as he bombards major cities with hella big rocks: "Do a barrel roll, Earth!"

A few years old but highly relevant. (0)

Anonymous Coward | about a year ago | (#42555383)

http://www.youtube.com/watch?v=1IXYsDdPvbo

The entire talk explains not only how easy this would be, but some of the technical challenges around g-hardening. (Protip: use silicone and epoxy)

Cannon to the Planets (0)

Anonymous Coward | about a year ago | (#42555543)

Slasdot already covered this... Cannon to the Planets

How do you keep the barrel straight? (2)

trout007 (975317) | about a year ago | (#42556065)

At those speeds you need the barrel, track, or rail straight to extreme precision. Any deviations will set up a wave in the track that will destroy it.
We built a 1000 ft light gas gun and had it happen. A couple hundred feet down the track the projectile existed through the wall of the tube and the tube was bent into a sin wave.

10x slower than the escape velocity needed (1)

fezzzz (1774514) | about a year ago | (#42556141)

The problem we face is that the guns on earth with the highest muzzle velocity is still about 7x below the escape velocity needed to have a projectile stay in orbit.

The Paris gun, created by the Germans in WWII was able to reach a target 130 km away, but the muzzle velocity was only 1600 m/s and already they had to sort their bullets in increasing diameter as the inside of the barrel was worn out with each shot. The fastest gun muzzle velocity I know of is the kinetic penetrating sabot rounds shot from tanks, which reach a velocity of 1700 m/s. Escape velocity [wikipedia.org] is 11200m/s, which is well above this speed.

Catching a projectile from orbit is also not an option as this will slow the satellite with the amount of momentum needed to bring the projectile up to speed, not even speaking about the problems created with something as sensitive as a satellite need to catch a projectile travelling at 7x the speed of current bullets in kinetic tank destroyers.

Le Voyage Dans La Lune (1)

WebSorcerer (889656) | about a year ago | (#42557031)

Le Voyage Dans La Lune is a movie made in 1902.

From Wikipedia:

"At a meeting of astronomers, their president proposes a trip to the Moon. After addressing some dissent, six brave astronomers agree to the plan. They build a space capsule in the shape of a bullet, and a huge cannon to shoot it into space."

Wikipedia [wikipedia.org]

railgun (0)

Anonymous Coward | about a year ago | (#42557341)

how about electro magnetic projection such as with maglev trains and rail guns?

Disappointed...thought he meant a "space gun" (1)

dywolf (2673597) | about a year ago | (#42557535)

As in a "gun" (weapon) used in space, which is to me a MUCH more fascinating engineering and design problem. In space, inertia and recoil are a bitch.

Missles probably impractical because they rely on aerodynamic forces to steer (nozzle alone isnt enough to change course/ uses too much fuel), whch leaves us energy and projectile weapons. Turrets can't whip around. Anything kinetic needs to dissipate the recoil which will favor recoilless designs, but those have their own complexities (current designs still have -some- recoil, which while negligible on the surface would have a magnified effect in space). the classic problem of what to do with the heat buildup.

I honestly think space combat will favor a design that is the fusion of two "obsolete" technologies, that of battleship and bomber, though i'm thinking more medium/dive attac bomber. the battleship classic standard is that of dishing and taking damage; this translates to a large mass, and more mass has advantages for absorbing both recoil and heat. the bomber side from the concept of lobbing essentially dumb munitions (bombs or "depth" charges) on a calculated physics trajectory. Though the trouble there, is there no fluid medium to tranfer the energy, so the munition either absolutely must impact the target directly, or cast out a large amount of shrapnel (which would complicate the battlefield for the attacker too).

The list goes on. Fascinating.

Imagine a space gun... (0)

Anonymous Coward | about a year ago | (#42557933)

...that is used to launch a gun into space, which in turn that gun (in space) could be used to shoot at stuff back down on Earth. Now imagine a beowolf cluster of these guns in space ;-)

Yeah, I know we have treaties against weaponizing space, but in the end all treaties get broken anyway, and whoever is first to get such a gun into orbit will have a huge tactical advantage.

Ramjet-like projectile, (1)

zrbyte (1666979) | about a year ago | (#42557615)

sequentially detonated propellant... Hmm... It seems to me we're getting closer to the design of rockets :)

No substitute (1)

Necron69 (35644) | about a year ago | (#42557635)

Hokey religions and ancient weapons are no substitute for a good blaster at your side, kid.

Wait a minute. What are we talking about again?

Necron69

Space Donut (my space gun concept) (1)

deathcloset (626704) | about a year ago | (#42558579)

http://www.youtube.com/watch?v=QShvDj12xBc [youtube.com]
"This is the concept for a 10,000 Meter ( 30,000 Foot), ballon-supported space gun.
The tube or barrel is 0.6 Meters (2 feet) in diameter, so it is intended for launching very small payloads.
It is unknown how plausable this is,.

The goal is to get above 10K meters, as the atmosphere is less than 50% as dense as sea level, thus friction should be low and momentum from accelleration up the tube or barrel should encounter less resistance."

It's such a funky concept, I know. But I think it is at least rather different than most space gun concepts. Skepticism and criticism is most welcome.

Just trying to think outside the sphere.

got a coin (0)

Anonymous Coward | about a year ago | (#42559767)

a gun is not feasable, because any human in the projectile launched would become a
"nano-scale-thin-flat-pizza".
interesting enough the human body is 70? 80? 90? percent water and water does not compress.
so if the most of the projectile for once were not destructive, one could fill it with water (heavy) and
put a human inside.
unfortunately all we know about accelerating humans inside a water-bubble boils down to
errr ...
anyways if you would like to take a bet for a jellyfish to survive a launched from a 50 kilo water enclosing projectile (launched at ludecrase 1000g)
to orbit alive ... take me down for yes, it will sting u in orbit .. ALIVE : )

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