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How well would a firearm like the M4 perform in outer space?
http://www.quora.com/Physics/How-well-w ... ans2627496

How well would a firearm like the M4 perform in outer space?
I wonder what would happen to a firearm when fired in outer space, the most problematic thing I can imagine is the heat buildup

Frank Heile, PhD in Physics then career in SW Eng
106 votes by Don van der Drift, In PhD Physics program for 2.5 years, former Physics researcher at LBNL, Sietse de Boer, Ryan Carlyle, (more)
The vacuum of outer space will not be a problem for firing a bullet. Guns do not need oxygen to work. The "gunpowder" or whatever explosive is in the cartridge that holds the bullet is completely self contained and does not depend on the atmosphere. It has an oxidizer mixed with the fuel and is perfectly capable of firing in a vacuum. Even the primer which is struck by the pin of the firearm is completely self contained and will work in a vacuum.

The gun will work (very slightly) better in space. The bullet will not have to push and compress the air in the barrel as it exits the gun. Air will not slow down the bullet as it travels, so the range of the gun would essentially be infinite.

There's more. I just thought this was an amusing treatise on the subject. The scary part is that the Rooskies pulled a Crazy Ivan and actually TRIED shooting a gun in space, having test-fired a gun from their Salyut space station.

.......wonder what they were shootin' at.....

I wonder what kind of recoil issues they experienced.

Yeah, this is one of those things that people who know nothing about guns or space don't think about, people who know a decent amount about both think correctly about, and that people who know a little bit about both think incorrectly about.

Of course, just making sure the cartridge propellant burns is only part of it - most lubricants aren't vacuum-rated, so there's a chance that whatever was used on that gun would boil off or flash-freeze, so the action could lock up. Outgassing of polymer materials is another potential issue, but that probably wouldn't have a huge impact on function. Might not get more than one shot (or even that if the firing pin was stuck, I guess). There's a (possibly-apocryphal) story about early Apollo astronauts sorting through a standard aircraft survival kit to see which items would be useful if they crashed on the moon - the matches were useless, but they thought they coups use the pistol as a means of propulsion.

Incidentally, I think that the Soviets were only going to use the cannon on the Almaz stations against American anti-satellite weapons, and that they only test-fired it once. At least, that's the official story....

Steve133 wrote:Yeah, this is one of those things that people who know nothing about guns or space don't think about, people who know a decent amount about both think correctly about, and that people who know a little bit about both think incorrectly about.

Of course, just making sure the cartridge propellant burns is only part of it - most lubricants aren't vacuum-rated, so there's a chance that whatever was used on that gun would boil off or flash-freeze, so the action could lock up. Outgassing of polymer materials is another potential issue, but that probably wouldn't have a huge impact on function. Might not get more than one shot (or even that if the firing pin was stuck, I guess). There's a (possibly-apocryphal) story about early Apollo astronauts sorting through a standard aircraft survival kit to see which items would be useful if they crashed on the moon - the matches were useless, but they thought they coups use the pistol as a means of propulsion.

Incidentally, I think that the Soviets were only going to use the cannon on the Almaz stations against American anti-satellite weapons, and that they only test-fired it once. At least, that's the official story....

So I'll stick with my 1911, and lube it with graphite.

I also wondered if it would fire at all since oxygen would be needed, but IDK since they will fire underwater. Is there enough oxygen underwater for that or is it the oxygen trapped inside the sealed case of the round? Hmm. Oh, I just went back and noticed the author mentioning an oxidizer.

The recoil thing is also interesting.

Cooling, isn't it pretty cold in space? Why would heat build up be an issue?

C-dub wrote:I also wondered if it would fire at all since oxygen would be needed, but IDK since they will fire underwater. Is there enough oxygen underwater for that or is it the oxygen trapped inside the sealed case of the round? Hmm. Oh, I just went back and noticed the author mentioning an oxidizer.

The recoil thing is also interesting.

Cooling, isn't it pretty cold in space? Why would heat build up be an issue?

The propellants contain oxidizers.

C-dub wrote:
The recoil thing is also interesting.

Recoil is no different than here on earth. If you're holding it, it would recoil just the same. If the gun was floating when fired, both objects would move apart from each other just like they would here on earth as well.

C-dub wrote: Cooling, isn't it pretty cold in space? Why would heat build up be an issue?

This is one thing people don't realize about space. Yes, it's cold, but there's very little heat transference. You need contact for that. Heat would actually leave an object much quicker in ice water than in space due to contact and heat transference. In space, an object actually retains its heat fairly well relatively speaking.

Scott in Houston wrote:

C-dub wrote: Cooling, isn't it pretty cold in space? Why would heat build up be an issue?

This is one thing people don't realize about space. Yes, it's cold, but there's very little heat transference. You need contact for that. Heat would actually leave an object much quicker in ice water than in space due to contact and heat transference. In space, an object actually retains its heat fairly well relatively speaking.

Yeah, hard vacuum is about as good of an insulator as you can get.

Wonder how accurate the gun would be? It would of course have to be re-sighted in but even if sighted in for outer space would the bullet fly the same path each time?

Ericstac wrote:Wonder how accurate the gun would be? It would of course have to be re-sighted in but even if sighted in for outer space would the bullet fly the same path each time?

Maybe someday we'll be discussing the grouping we can achieve at 20,000 miles?


Seriously, that is a good question.
In reality, is shouldn't be much different than what we see here when in a controlled environment like an indoor range. The only variable you'd experience in space vs. here is the lack of air, so if you can control the air down here and keep it as a constant for each shot, the 'accuracy' could be measured the same.

Scott in Houston wrote:

Ericstac wrote:Wonder how accurate the gun would be? It would of course have to be re-sighted in but even if sighted in for outer space would the bullet fly the same path each time?

Maybe someday we'll be discussing the grouping we can achieve at 20,000 miles?

We'll have to revise the four rules.

Know your target and the closest planetary object behind it.

george wrote:Gravity is still involved, you know.

Only if you are at the local shooting range in a close-Earth orbit. Go to the more rural ranges out past the orbit of Pluto where gravity may have less of an effect.

Scott in Houston wrote:

C-dub wrote: Cooling, isn't it pretty cold in space? Why would heat build up be an issue?

This is one thing people don't realize about space. Yes, it's cold, but there's very little heat transference. You need contact for that. Heat would actually leave an object much quicker in ice water than in space due to contact and heat transference. In space, an object actually retains its heat fairly well relatively speaking.

I'm no engineer/physicist, but I think it would be a matter of how hot the barrel was, wouldn't it? Machine gun barrels can glow red under extreme use, and they give off part of that heat energy as light. Stars give off part of their heat energy as light, and that doesn't need contact with a substrate to transfer, does it? The light from stars transfers without there being any atmosphere between the star and earth. In fact, we experience some of that transfer as heat. So here is my hypothesis:

• A red-hot gun barrel would cool in space at a relatively rapid rate until it had given off enough energy to stop emitting light, at which point the rate of cooling would be greatly reduced as the heat transfers through the bearer's hands and is dealt with by the spacesuit's cooling apparatus. The problem of course is that the insulating layers of spacesuits would impede that heat transference.

Like I said, I'm no rocket scientist, so I'd be interested to know from someone better informed if my guess is correct or not.

Steve133 wrote:Of course, just making sure the cartridge propellant burns is only part of it - most lubricants aren't vacuum-rated, so there's a chance that whatever was used on that gun would boil off or flash-freeze, so the action could lock up..

As far as the effectiveness of lubricants in space, I have an anecdotal but I'm-pretty-sure-it's-true story to offer. As some of you know, my family was part of the Caltech/JPL community. My parents were professors there, and my father in law was a JPL engineer who designed and built guidance packages for a number of spacecraft. One of my good friends who was one of my racetrack pit-partners was also a technician at the Carnegie Institute facility on the Caltech campus, and they were building a gyroscope to be used in one of these guidance packages that was to be sent into space—I think it might have been the Hubble Telescope. The problem was how to lubricate the bearing points of the spinning gyroscope's axis. This is less of a critical issue for a gyroscope that is going to return to earth because of the sheer length of time the lubricant will have to hold up for one that is not going to return. They had a meeting about how to procure a lubricant with the properties of tackiness so that it would adhere well to the parts to be lubricated without migrating to places that did not need it, low volatility so that it would not evaporate away, the ability to absorb tremendous shearing forces, and yet the ability to maintain a thin film at the points of contact between moving parts. Brian got up, left the meeting, went out to the parking lot, and retrieved the can of Bel-Ray motorcycle chain lube from under the seat of his motorcycle. He brought it into the meeting, explained its properties, demonstrated it, and—according to what he told me—the decision was reached to use tiny amounts of motorcycle chain lube at the points of contact. Instead of spending thousands of dollars on research and sophisticated materials, a $3.95 can of chain lube saved the day.

I love those kinds of stories, and I have another one involving my father in law, who saved the government from spending a million dollars on a spacecraft part with a $1.98 piece of wood.