Guns in space

Status
Not open for further replies.

learn2shoot

Member
Joined
Jul 6, 2006
Messages
364
Location
Springfield, VA
I realize this is a bit off topic, but interesting none the less.

http://ask.yahoo.com/20060726.html

Dear Yahoo!:
What would happen if I shot a gun in space?
Kimm
Buffalo, New York

Dear Kimm:
Ah, an inquiry that warms the hearts of gun-toting physicists. The peacenik response might be...nothing. A gun cartridge holds the bullet or metal tip and the gunpowder (yup, they still use that stuff). The latter requires a spark, a nifty chemical reaction that involves oxygen, which tends to be sorely lacking in space. However, forward-thinking manufacturers have packed an oxidizer within the bullet casing. Whether that's sufficient for an explosive launch is up for much debate.

That doesn't satisfy our bloodlust, does it? We'll assume we can send the bullet on its merry way with the proper gun. The scenario then conjures up the classic physics poser of shooting the monkey. Since we find shooting a cute primate abhorrent, we'll sub in the garden gnome.

Where you're standing when you execute this maneuver, such as within a planet's gravitational pull, would affect the bullet's speed and path. As long as your aim is true, the bullet would travel a straight line (aka Newton's first law of motion) until some sort of force or object impedes it. Meanwhile, the recoil (Newton's third law) has pushed you back with an equal and opposite force multiplied by your mass.

The next question is, can you fire off another shot? A regular old earth gun likely won't cotton to its new environment and may seize up, blow up, or do something equally annoying. Plus, we've littered space with enough dangerous debris already, do we really need to have bullets go flying?

I cannot think of how or why the gun would blow up or seize up. I would think that the gun would function fine (with the presence of an oxidizer). Any chemists or gun-toting physicists in here?
 
In space, no one can hear you scream.


It would ignite, but I'm not sure if there would be enough oxygen for it to burn completely.

Anthony
 
Since firearms don't rely on gravity to function and the 15psi or so atmospheric pressure doesn't significantly offset chamber pressure, I'm sure your rifle or handgun would function just like it does at the range. Ballistics would change for sure. With no air resistance to slow the bullet and much less gravity to cause drop you are going to hit well above point of aim unless you adjust your sights. If you are floating in "space walk" conditions your recoil velocity will pretty much be muzzle velocity times the bullet weight (in grains) divided by your weight (in grains). So if you shoot a 30-06 (150 gr @ 2700fps) and you (and the gun) weigh 200 pounds you will be propelled backward at a rate of 2700*150/200/7000 or 0.3 fps. Forget about finding your brass if you shoot an auto though. The brass will keep going and going and going. Just like the energizer bunny.

All the oxidizers needed are in the primer and propellant. Modern, and for that matter antique, firearms do not need oxygen in the atmosphere to burn. Black powder arms compress the powder by hammering the ball tightly down on the charge (no air space at all). With the exception of black powder catridges that have survived the move to smokeless, there is very little air space in a modern cartridge and it wouldn't matter if that pace as filled with an inert gas.

The real question is will you hear the shot?:)
 
I cannot think of how or why the gun would blow up or seize up.
the differences in thermal conductivity means the the different parts of the gun will shrink and expand in the extreme temps at different rates, this isn't good for slide to frame fit. the lubricant's also wouldn't fair well, perhaps even turning into a gas with the lack of pressure.

seriously though, if the Russians wanted to sell more AKs they would bring one up and fire off a few rounds, that would be an awesome endorsement of reliability.
 
Reminds me of a SciFi story I read many years ago about the US and USSR colonists starting a shooting war on the moon. Ever orbit of the bullets they had to duck and take cover until the low gravity finally had an effect. LOL
 
The person who "answered" in that article ought to be shot into space himself.

Both the primer and smokeless propellant in a modern cartridge will work in a zero-oxygen environment. Remember that you can fire 9x19 out of one of those specially modified glocks while underwater? Not much gaseous oxygen in there.

The gun would not "sieze" or "blow up." The vacuum would have no noticeable effect on the gun - It relies neither on gravity or atmospheric pressure to work or to hold itself together. The absence of air pressure and friction would have a negligible effect on the moving parts of the gun - Measureably none. If you exposed the thing to the sun it would get hot in a hurry, but we can assume that if the heat/cold dichotomy of hard vacuum isn't turning you into a flaming popsickle it probably isn't hurting your gun any. Lubricants would probably freeze in a hard vacuum, but they're not strictly needed for function with most guns.

What would happen is that the recoil from the shot would throw you backwards in a zero-g/zero atmosphere environment, and you'd run the risk of drifting away. If you have another shot you could fire in the other direction and stop yourself...
 
the differences in thermal conductivity means the the different parts of the gun will shrink and expand in the extreme temps at different rates, this isn't good for slide to frame fit. the lubricant's also wouldn't fair well, perhaps even turning into a gas with the lack of pressure.

Good points. I didn't think of the effect on lubricants. Guess I'll have to use a bolt action rifle with graphite if I ever get a chance to try this....

In the movie where they send the roughnecks to drill a hole in the meteor that was about to wreck the earth (can't remember the name) the machine gun mounted on the vehicle seemed to work fine.

Why did they think they would need vehicle mounted automatic weapons anyway?
 
assuming the shooter is in earth orbit (rather than interstellar space,etc) the bullets ultimate trajectory is going to depend on the direction that it is fired, because the gun and shooter are already travelling about 18,000 mph

fired "forward", the bullet would eventually (if it doesn't hit anything) settle into a higher orbit. fired backward, it would probably drop to the earth and burn up in the atmosphere. fired sidways, the bullet would probably end up in an orbit at a different angle (inclination to the earth's axis)

there's probably a real rocket scientist on THR that could provide all the equations ;)
 
Indeed - good point on the lubricant. I think a dry Gov. 1911 would work fine for a long time (not a tightened one though due to the temp problems).

There are a lot of holes in the answer given in the article. One of the worst is that the general public will believe it. He says the bullet will be affected by the planet's gravity then immediately says the bullet will go in a straight line "as long as your aim is true". All this happens "until" some force acts upon it. Perhaps a sudden burst of gravitons is what he's thinking of.

Maybe that explains a long time mystery of mine. If my aim isn't true, then the bullet trajectory curves more than usual!

Why did they think they would need vehicle mounted automatic weapons anyway?
Because Bruce Willis was in the movie; no other reason necessary! It was called Armageddon. There were more holes in the science of that screenplay than any other movie in history. Even "Amazon Women on the Moon" apparently had a better science advisor.
 
I didn't think of the effect on lubricants. Guess I'll have to use a bolt action rifle with graphite if I ever get a chance to try this....

http://yarchive.net/space/spacecraft/space_lubricants.html
Solid lubricants are definitely preferred for vacuum use. Teflon is quite
popular. Graphite is not a lubricant at all in vacuum -- in the absence
of air, it becomes an abrasive! However, a similar but more obscure solid
lubricant, molybdenum disulfide, does work in vacuum.

good to know for all the libertarian sci-fi fans.
 
Sometime after firing, your bullets would come back at you !! Not from behind, but from ahead and above.

If you were to fire a series of bullets straight ahead of you, they would leave the gun at velocitys similiar to they would on Earth.

Your bullets would then, via centrifigual force RISE significantly (to a higher orbit).

This is where it gets interesting. Now because your bullets are in a higher orbit than you, they also have a much larger circumference around the Earth to follow. As a result the relative speed between you and your bullets slows down as they gain altititude until eventually your bullets will be traveling SLOWER than you.

In short, any bullets fire in space will behave like boomerangs. They will leave your gun rapidly, stop in mid "air", reverse direction and fly over your head.

Orbital mechanics are weird. Of course the bullet never really slows down, but it certainly does strange things from the point of view of the shooter.

The moral of the story. If you need to shoot someone in space, better get a calculator first (and keep your head down) :)
 
Wouldn't you be sent flying backwards with the same force propelling the projectile forward?
 
Wouldn't you be sent flying backwards with the same force propelling the projectile forward?

Yes, but the same things happens on Earth. It's called "recoil", and is a function of Newton's Third Law of Motion, i.e., for every action there is an equal and opposite reaction. Force is the product of mass and acceleration, however (F=MA). Since the combined mass of you and the gun is much larger than the mass of the projectile, you will have a much lower acceleration, and consequently the rearward velocity will be quite low.
 
It is an interesting calculation to compute the necessary velocity to put the bullet into 'low moon orbit' (it is surprisingly small!) and how long you would have to stand in one place to shoot yourself in the back (quite some time).
 
Yes, recoil is more a function of your mass than it is of gravity. The only benifit gravity gives you is the friction with your feet, or the shooting bench and your butt.

If you laid down on a perfectly frictonless skateboard and fired a gun or a rifle, you'll get some idea of how fast you'll move. Even with a .50 BMG or 12ga slugs, it's not a lot.

You mass several hundred, if not thousand times the bullet, depending on caliber. Recoil for an astronaut should be managable with just hands, feet, (assuming there's something like a larger ship or station to grab onto) or a tether, or gas thruster manuvering system.

If it's a rifle, taking the "prone position", with the bore in line with the major axis of your body, head to feet, is probably adviseable. The "standing position" with the bore at right angles to your body, at the shoulder would probably impart some spin, that could be a nusiance.

As to the "shooting yourself in the back" on the moon with a .45 ACP, when standing at the peak of a tall mountian its feasable. However, I wonder (assuming no other mountains are in the way) if gravitational disturbances from mountains, plains, and mineral density variations wouldn't bring it off course just enough to miss you by a few feet.

The earth's geology is more dynamic, but for both ICBM targeting and satellite station-keeping, density maps of the earth are factored in to keep the trajectories true. For instance, you weigh a fraction of an ounce less at Yellowstone, because of the low-density magma plume that makes the area vocanicaly active.

But if you are on a raised platform on a perfectly smooth airless planet, and shoot from a machine rest with the right velocity, shooting yourself int he back of the head is possible.
 
"and how long you would have to stand in one place to shoot yourself in the back (quite some time)."

Actually it would be exceptionally difficult to shoot yourself in the back. Maybe if you shotdown at 180 degree angle. Maybe

See my above post. The bullets would not "go around" and come from behind.

They would shoot out from your gun(normally), rise(into a higher orbit) and "stop" in mid air and come straight back toward you over your head.

however If you were to shoot 1 bullet straight ahead, and 2 bullets straight behind you, would get shot from the first bullet - from the front.

Orbital mechanics is a extremely counter-intuitive.
 
Regarding smokeless powder, would the cartridge casings need to be air tight or do the powder grains themselves contain the oxidizer? I do remember reading that black powder packed in tight has enough O2 to burn in the air mixed in with the powder.

What would be the best bullet shape in open space? terminal performance would be one of the biggest factors as long as the bullet grabs the rifling well for gas seal.

For operation of an automatic, do you think the recoil mechanism would need to be adjusted for operating in a vacuum? Could you might be able to use the vacuum to assist the return stroke. Maybe I am overestimating that effect. I am curious if fouling of the gas system would be the same concern. Probably so.

Also, metal parts in actual contact might transfer heat okay, but heat dissipation off the barrel and gun in general would be very poor with no air to take off the heat.
 
For the "shoot yourself in the back on the Moon experiment", you would have to take planetary rotation into effect and add or subtract it as needed from your desired muzzle velocity, but if you had a perfectly uniformly smooth airless world, you stood at the equator, and shot exactly horizontaly perfectly in line or against planetary rotation at the orbital velocity needed, for the altitude you were standing, you could do it.

So in terms of pure orbital mechanics it's possible, but in practice almost impossible.

It would be fun to have an astronaut do the space version of "Hatchers Notebook's" pond experiment, stationed exactly at the moon's equator, with a machine rest, and a plate of armor and a target painted on it behind him.

Assuming he's at the moon's highest elevation on the equator, he could probably get to within a few feet of himself if he had a good radar, a computer, and some careful load development.

As to the oxygen factor, all gunpowder (BP, smokelss, cordite etc.) is self-oxidizing to the point that there'd be no difference to firing it in space, or something like a pure nitrogen or CO2 atmosphere. There never was enough oxygen in any gun barrel or cartridge case to make a diference from the beginning of the invention of gunpowder.

The vaccuum of space wouldn't "assist" the operations of a firearm any more than it would hinder it. The vaccumm is equal on all sides and parts of the gun just like the air is on Earth. The differential between the expanding gasses and the vaccuum would be a bit different, but only by 14psi, (sea level on Earth) well within the variations from shot to shot of modern ammunition. The extra 14 psi pussing "in" on the gun when it's fired vs. the tens of thousands of PSI in the chamber is negligable. So no "guns exploding in space" of that you can be sure.

Negating any other space factors like heating or freezing, or thermal expansion and contraction of the parts, for the moment If your gun KB's in space, it was going to do it on the ground.

The slide velocity on recoil and blowback operated automatics would be negigably higher with no air resistance, outside, or being "squeezed" out through the frame and slide gap. If it's a factor at all, it's well within the range of recoil spring stregth and load selection.

Gas retarded semi-autos like the HK P7 would probably cycle a bit "late" as the pressure differential in the locking cylinder would be a bit higher due to the vaccuum. If it's enough to cause a failure to cycle is debateable, but again, load choice, and the proper recoil spring could probably overcome it.

Gas operated semi-autos might require different port sizes or pistons, and recoil springs, something with an adjustable gas piston like the FAL would be good idea. It shouldn't take too much to get the gas system of most any automatic rifle adjusted properly to function in a vaccuum.

Lubricants that withstand vaccuum, design tolerances and/or alloys that take thermal expansion and contraction from sunlight and shadow in space into account throw in more factors, but NASA has lots of parts and tools that work in a vaccuum, so while I think it's up in the air if stock firearm designs would work in space, it's a minor enginnering challenge to get them to do so.

However, my gut tells me that if you took a stock Kalashnikov and some Wolf 7.62x39 ammunition that functioned well on Earth, lubricated with a non-volitile synthetic grease, and took it into space. I'd wager it has an 80% chance of getting through an entire 30 round magazine without trouble.

FYI, the Russians did mount some rather large machineguns on thier late 60's or early 70's Saylut space stations. Borne of cold-war paranoia, they were afraid of close reconnisance by US spy sats, or outright capture by a "secret" US spaceplane that "existed" before the shuttle.

Either that, or someone at Cosmodrome watched "Dr. No" one too many times.
 
Last edited:
Well - you wouldn't really fly backwards unless you held the gun directly in line with your center of mass.

If a recoil (force) is applied to a mass (you) at any point other than center of mass, a rotational moment (force) will apply that is proportional to the distance from center of mass.

For example - assume a 6'5" 250 lb shooter (that's me!) - in a standard isosolese hold my 44 magnum would be approximately 3 feet above and 3 feet forward of my center of mass - assuming a pefect triangle - strightline distance to COM is the square root of the sum of the squares or sqroot of 18 or approx 4.25 ft

So a rotational acceleration or "spin" will be imparted to me (force / mass X moment arm / circumference of the circle described by my spin) (1500fps x .034lbs/250lbs x 4.25 ft / 18.8 ) = about 3 rotations per minute.

Tall skinny guys will spin faster - short stocky guys will spin slower.

So - in space - shooting from the hip may actually be the preferred method - to minimize the distance from COM the recoil force is applied to your mass and therefore reduce the resultant spinning...
 
Points

It's an interesting point that for a sphere with a density equal to the Earth's a very low orbit will have a period of about 84 minutes, regardless of the size of the sphere. The orbital speed is then the circumference of the sphere divided by 84 minutes. It would be 60 mph for a sphere with a circumference of 84 miles. A 45 ACP could be launched into a stable orbit around an asteroid of around 1200 miles circumference or 390 miles diameter. If you are on Ceres you will probably need a 357 Magnum to do this.

Most cartridges are not absolutely airtight. If exposed to a vacuum for an extended period certain components of the powder will evaporate and change the burning chracteristics of the powder. This might or might not have a significant effect.
 
What the cosmonauts packed were sawed-off shotguns, and the purpose was to defend themselves against wild animals should they meet some before the rescue team gets there.

http://www.smh.com.au/articles/2003/05/05/1051987657858.html

Off-course spacemen lucky
May 6 2003

It could have been a lot worse for the two Americans and one Russian whose landing ended up nearly 500 kilometres off course and their recovery hours late.

In 1976, a Soyuz spacecraft came down in a freezing squall and splashed into a lake; the crew spent the night bobbing in the capsule.

Eleven years before that, two cosmonauts overshot their touchdown site by 3000 kilometres and found themselves deep in a forest with hungry wolves. That's when Russian space officials decided to pack a sawed-off shotgun aboard every spacecraft.

Astronaut Kenneth Bowersox said with a smile that he didn't need the gun in the Kazakh steppes where he landed on Sunday: "There was nothing out there but grass and us."

Yesterday, Russian space experts met to discuss what went wrong with the Soyuz capsule carrying Bowersox, astronaut Donald Pettit and cosmonaut Nikolai Budarin back from the international space station. The spacecraft was a new model that had never gone through a re-entry before.

"I'll call it an interesting test flight experience," Bowersox, a Navy captain and former test pilot, told The Associated Press several hours after touchdown.

It was the first time NASA astronauts had returned to Earth in a foreign spacecraft and to a foreign land. The switch from a shuttle to Soyuz landing came after the Columbia disaster in February, which resulted in the indefinite grounding of the entire shuttle fleet.

The cockpit computer displays abruptly switched from a normal re-entry to a ballistic one just minutes before touchdown, and the three men knew they were in for a considerably steeper and rougher ride than usual.

They came in short of their targeted landing site and two hours passed before recovery forces spotted them. Two more hours went by before helicopters arrived for them, and another two hours before NASA personnel reached the scene.

Bowersox, who commanded the 5-month space station mission, said he and his crewmates enjoyed having some time by themselves to get their land legs back and savour nature.

"It was the most beautiful dirt I've ever seen," he said.

By late afternoon, Bowersox, Pettit and Budarin had landed in the Kazakh capital of Astana, and a few hours later, they reached Star City, outside Moscow, where they were greeted by a crowd including their wives.

During the flight from Astana to Star City, Bowersox told the AP he thought the crew had notified Russian Mission Control about the computer indications for a ballistic entry, but couldn't be sure. It's also possible communication was lost at that point, he said.

The last call received from the Soyuz was to confirm that the main parachutes had deployed 16 minutes before touchdown. The antennas were smashed after the capsule smacked down and was dragged 12 metres by the parachutes.

"We thought everybody should know [where the Soyuz landed]," Bowersox said. "Obviously, we know so everybody else should know," he joked.

A similar sentiment was expressed by Mercury astronaut Scott Carpenter, who overshot his splashdown point in the Atlantic by 400 kilometres in 1962.

Carpenter fell behind in his orbital work and, while rushing to catch up, made a series of mistakes that led to the off-course landing. NASA knew where he was because of radar, but the flight director made sure Carpenter never flew in space again.
 
Most cartridges are not absolutely airtight. If exposed to a vacuum for an extended period certain components of the powder will evaporate and change the burning chracteristics of the powder. This might or might not have a significant effect.

But if the cartridge WAS airtight, wouldn't the atmospheric pressure inside pop the bullet out before you fired? Depends how strong the crimp is and how much headspace in the cartridge, I suppose. Better carry one in the pipe, it may be the only shot you have. :D
 
Status
Not open for further replies.
Back
Top