Can Firearms be Fired in Space


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Life During Wartime
July 22, 2013, 11:04 PM
Can Firearms be fired in outer space such as on a space station or on the moon
and if so
can it cycle actions
and
how far would it go
endlessly or like in water

also what about rocket launchers

I have heard of the russians issuing their cosmonauts a gun the tp82

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jim243
July 22, 2013, 11:11 PM
Can Firearms be fired in outer space such as on a space station or on the moon

Yes they can. Gunpowder carries it own oxidizer and will work in outer space. The "Space Station" has a oxygen rich atmosphere and would start a flash fire, so the answer would be no on the space station because of fire hazards. Since the moon has 1/3 the gravity of the earth, you should be able to get 3 time the distance you would on earth, but it would actually be a little longer since there is no wind on the moon to slow down the bullet.

As to distance a bullet will travel in outer space is a little harder to answer. Newton's law of opposite and equal reaction would make the bullet go forward but you would also go backwards, so half the energy would be used to propel you in the opposite direction. How much energy would the bullet still have? I don't know, but in theory it would travel until it comes into a gravitational field of some planet, moon, comet or asteroid.

Hope that answers your questions.
Jim

Torian
July 22, 2013, 11:16 PM
Can Firearms be fired in outer space such as on a space station or on the moon
and if so
can it cycle actions
and
how far would it go
endlessly or like in water

also what about rocket launchers

I have heard of the russians issuing their cosmonauts a gun the tp82

I would prefer to talk about the proper use of commas and semicolons in this post, but with great effort, I will refrain from doing so.

:evil:

I was not aware that gun powder could ignite in a vacuum. I guess you learn something new every day.

OptimusPrime
July 22, 2013, 11:20 PM
It's not a vacuum, it's a self-contained capsule that has its own oxidizer.
To the OP's question, a rocket launcher like an AT4 or LAW should work on the same principle; they are sealed and should ignite just fine. However, I do believe the rounds will go much farther than only 3x the Earth distance because there is also no atmosphere and therefore no air resistance on the projectile.

Life During Wartime
July 22, 2013, 11:28 PM
If you fired either a rocket launcher or a firearm on the moon would it follow the curve of the planet or just go off into space would u think


plus, what were the russians thinking! :eek:

Torian
July 22, 2013, 11:30 PM
It's not a vacuum, it's a self-contained capsule that has its own oxidizer.
To the OP's question, a rocket launcher like an AT4 or LAW should work on the same principle; they are sealed and should ignite just fine. However, I do believe the rounds will go much farther than only 3x the Earth distance because there is also no atmosphere and therefore no air resistance on the projectile.
I'm not sure that "self-contained" capsule would hold a perfect seal in a vacuum.

jaysouth
July 22, 2013, 11:31 PM
Since it's not in a forest, will anyone hear it?

beatledog7
July 22, 2013, 11:32 PM
If you fired either a rocket launcher or a firearm on the moon would it follow the curve of the planet or just go off into space would u think

It would curve downward and hit the surface. Gravity exists there, too.

rkite
July 22, 2013, 11:36 PM
I would think the cartridge case would bulge or split in a vacuum. If air could escape the case or it was loaded in a vacuum then maybe not.

Escape velocity of the moon is about 3280 feet/second so a fast enough round could escape the moon entirely otherwise it would go into a temporary orbit. If shot straight up the bullet would either escape the moon entirely or drop back to the moons surface.

With little or no atmosphere a bullet would hold its speed much better only having gravity to deal with.

Schwing
July 22, 2013, 11:42 PM
I am referring only to the idea of firing a gun in the vacuum of space here:


Physics was a long time ago but a similar topic actually came up about whether a dynamite explosion would expand forever and the professor gave an explanation that was not what I expected. According to him, since space is a vacuum, the explosion would occur, (Just like gun powder, dynamite has all of the essential chemicals required to oxidize),but it would quickly retract back in onto itself once the initial energy was expended and the force (or lack thereof) of the vacuum was greater than the remaining energy in the explosion. It was his opinion that most of the debris ( Mostly paper and carbon I would expect) would retract back into the vacuum.

I believe that the bullet would gain a lot of momentum and would continue to travel much further than it would on earth but I do not believe that the expansion of gases would reach near the same level that it would within an atmosphere and the bullet would not achieve near the same max velocity.

Just my own logic. But this would be a great experiment just for giggles.

rcmodel
July 22, 2013, 11:43 PM
I'm not sure that "self-contained" capsule would hold a perfect seal in a vacuum. It doesn't need a perfect seal, any seal at all, or any air inside it to fire.

There is very little oxygen inside a cartridge in the first place, or any air inside a barrel as the bullet push's it out of the way as it accelerates down the bore.



The smokeless powder is able to produce it's own oxygen to support the combustion of the powder.

Just like a Solid Fuel rocket fired into space.

SO, space or no space, vacuum or no vacuum??
You pull the trigger, it's going to go Bang just like it would on earth.

The bullet will go one way at mostly normal velocity.

And you will go the other way at unnatural velocity, due to the recoil and no gravity holding your feet on the ground.

rc

AethelstanAegen
July 22, 2013, 11:49 PM
I have heard of the russians issuing their cosmonauts a gun the tp82

plus, what were the russians thinking!

The gun was not really intended for use in space but as others mentioned would likely work there. The gun was included as a survival tool for when the cosmonauts returned to Earth and could potentially be stranded in the middle of Siberia for a while until they could be picked up. I'm not sure if it was ever used or if they even still include it on launches today. That's the reasoning though and explains why it's basically a drilling.

YZ
July 22, 2013, 11:55 PM
it would actually be a little longer since there is no wind on the moon to slow down the bullet.


You mean no atmosphere.

jungle
July 22, 2013, 11:57 PM
If the Russians did in fact issue a firearm to their space crews it is because they land in what is now Kazakhstan, the largest land locked country on Earth.

A very small error on reentry might place the crew in a land survival situation requiring a firearm for food procurement.

They ran into the same problem with aircrew, vast country and limited SAR capability.

Willie Sutton
July 23, 2013, 12:03 AM
Well, "outer space" and the moon are not the same. In one case you have near zero gravity and a vacuum, and on the other hand you are subjected to nearly normal gravitational forces (1/6 earth G) as opposed to nearly 0 G in space. 1/6 sounds like a small number, but compared to zero, which you cannot divide by, it's a nearly infinite increase in G as compared to "outer space".

So there are three questions:

1: How does a projectile act in 0 G?

2: How does a projectile act in reduced G?

3: How does a firearm and it's cartridge act in a vacuum?


So, let's examine each:

In zero G: In space, a projectile would travel indefinately, slowed only by a few small physical effects: Gravity (there is *always* gravitational pulls in space, towards *something*), and the drag effects of subatomic particles impacting on the object. But basically it would keep on moving in a straight line until it eventually was either captured into orbit by some sort of body, or drawn into reentry onto the surface of some sort of body. For an astronaut firing a frearm in 0 G: Newton tells us that if you fire a firearm, half of the energy is ALWAYS in an equal and opposite vector to the projectile fired. If YOU are on a frictionless surface (IE: are an astronaut on an EVA), the force applied will drive you rearwards at a rate governed by the foot pounds of force applied, and your mass. That's a simple equation. You will stop when either drag or gravitational forces come into equalibrium with your new vector. Drag will be small, gravitational forces also small, and your distance travelled will be large. Velocity would not be very large since force = 1/2 mass times the square of the velocity of the projectile, and that mass would be small.


In reduced G: The moon has a gravitational pull of 5.2 ft/sec2, as opposed to the earths 33 ft/sec2, meaning that a projectile fired parallel to the moons surface will fall towards the surface and impact the surface about after about 6 times the length of time as the same projectile fired on the surface of the earth. The ballistic coefficient of the projectile will be a major player in decelleration on earth, but this will not be a large factor on the moon. The bottom line is that between taking 6x the length of time to fall to the surface, and the fact that the projectile will not be decellerating very much as it goes downrange, a projectile on the moon would be a LOT further downrange when it struck the surface, and it would have a LOT more retained energy when it did so. The astronaut firing the firearm would sense normal recoil forces as the kinetic energy imparted as recoil would be the same.

In a vacuum: A firearm fired in a vacuum will behave normally. This has nothing to do with zero G or reduced G (space = 0 G and moon = 1/6 G). A semiauto would cycle normally. Propellant would burn normally. Velocities would be normal, but would not drop off due to frictional effects (drag).



OK, you want to shoot at the passing bad-guys space vehicle?

In orbit: Firing a projectile from one space vehicle toward another in a dissimilar orbit is a problem of orbital mechanics. It's not nearly as simple as aiming and shooting. Google orbital rendezvous equations for some answers. Start here:

http://www.braeunig.us/space/orbmech.htm



What else? Yes it is rocket science.

(And greetings from Edwards AFB where we teach this stuff at the test pilots school).


Willie

.

YZ
July 23, 2013, 12:10 AM
Do you teach that the projectile will go farther in a vacuum+reduced G than in an atmosphere+reduced G?

Sam Cade
July 23, 2013, 12:12 AM
and the professor

Fails at pretty basic physics.
:banghead:




I believe that the bullet would gain a lot of momentum and would continue to travel much further than it would on earth but I do not believe that the expansion of gases would reach near the same level that it would within an atmosphere and the bullet would not achieve near the same max velocity.

Ignoring temperature (and a few other twitchy variables) a bullet fired in a vacuum will achieve the same nominal velocity as one fired in an atmosphere.

Newton states that:
An object that is in motion will not change its velocity unless an external force acts upon it.

Lacking an atmosphere or gravitational field our bullet will continue in a perfect line at the speed it attained as it left the muzzle ad infintum


Ninjaed by Willie Sutton. ;)

Sun Tzu warrior
July 23, 2013, 12:14 AM
I'm with RC; the equal and opposite reaction would be my biggest concern.
In other words, I wouldn't be concerned if the round would go into orbit, I would worry about me, as the shooter, going into orbit!
torian; nice try at refraining.........It didn't work. ....... Thougt I might mispel a word or too so you could have a reasn to try an get us bak to english clazz, or just complain whichever yu prefer. Cheers!

OptimusPrime
July 23, 2013, 12:15 AM
Yeah, exactly what I said. :scrutiny:

Willie Sutton
July 23, 2013, 12:23 AM
"Do you teach that the projectile will go farther in a vacuum+reduced G than in an atmosphere+reduced G?"


Atmosphere = drag.

So the more atmosphere, the more drag. The more drag the more rapid the decelleration of the projectile.

In a vacuum, there is no aerodynamic drag, so.... velocity will be retained nearly indefinately.

G simply effects the "drop" of the projectile. With 0 G, the projectile travels in an straight line. Under gravitational influences, it falls towards the body exerting the force. Imagine this: Shoot a .30-06 parallel to the earths surface and at the same time the projectile exits the muzzle, drop a golf ball from the same height. Both will strike the ground at the same time, as both are falling towards earth at the same rate. Do that on the moon and they will take 6 times the length of time to strike the moons surface. Now EVEN IF THE MOON HAD THE SAME ATMOSPHERE AS THE EARTH (IE: the same aerodynamic drag), the projectile would travel a lot further. Now remove that drag and it'll travel a LOT LOT further.

Make sense? It's two different things. You can have one, the other, or both.



Answer these:

In a vacuum on earth, meaning in a vacuum chamber, if you drop a feather and a lead ball from the same height, which will hit the bottom of the vacuum chamber first? What would the difference be on the moon, if any?

If you had a LONG vacuum chamber on earth, and shot a .30-06 horizontally and dropped a feather at the same time, which would fall to the bottom of the vacuum chamber first? Amy difference on the moon?

If you shoot that .30-06 in a long vacuum chamber at a muzzle velocity of 2200 FPS, what will the velocity be when it strikes the bottom of the chamber on earth? On the moon? If I was able to fire a badminton birdie at 2200 FPS in a vacuum how would it compare to a boattail spitzer bullet? A round musket ball?

If you shot a bullet at 2200 FPS from a height of 1 meter from the bottom of the chamber, how far downrange would the projectile be striking the bottom of the chamber on earth? How about on the moon?


Hmmm...


And Schwing's professor obviously got thru about 3rd grade...


Willie

.

Black Butte
July 23, 2013, 12:29 AM
Since the moon has 1/3 the gravity of the earth, you should be able to get 3 time the distance you would on earth

This is not entirely true because the time it takes a bullet to fall is not linearly dependent on gravity.

Willie Sutton
July 23, 2013, 12:49 AM
^^ the post you are replying to is wrong on three points:

1: Moon = 1/6 gravity,

2: Moon atmosphere has far lower aerodynamic drag decellerating the projectile,

and

3: And to your reply-point, the fall-rate is exponential, not linear. It's 33 feet per second squared on earth, and 5.3 feet per second squared on the moon. Hypothetically a falling body on earth falls 33 feet the first second, 66 feet the second, etc. On the moon 5.3 feet the first, 10.6 the second, etc. BUT: On earth there is also atmospheric drag on the fall of the object, and this is not true on the moon. A human, for example, accellerates to about 100 MPH on earth (parachutist in freefall) before the force of gravity and the drag from the atmosphere balance each other, and then he stops accellerating. On the moon the accelleration would be far more constant in the near zero atmosphere condition.



Q: If you shoot a .30-06 straight up on earth at 2200 FPS, what will the velocity be when it strikes the earth? What will the slowest velocity of the projectile be during it's entire flight from muzzle to earth when so fired? How would doing this on the moon change the velocity at impact and the minimum velocity of the projectile on the flight? How about the apogee altitude of the projctile in both cases?


Willie

.

climbnjump
July 23, 2013, 01:00 AM
I'm with RC; the equal and opposite reaction would be my biggest concern.
In other words, I wouldn't be concerned if the round would go into orbit, I would worry about me, as the shooter, going into orbit!

Would you not already be in orbit anyway? ;)

Still, F=MA in space just as it does on earth. Assuming you were floating in free space and not constrained, yes you would move in the opposite direction of the bullet. But since your mass plus the mass of the weapon you fired is much greater than the mass of the bullet and the burned powder, your acceleration and ultimate velocity will be much lower than that of the bullet.

And, if you fired the weapon from your shoulder like you would on earth, the recoil is going to be acting on you some distance above your center of gravity. So while you will be propelled backwards, you will also be spinning about your center of gravity.

ETA:
But since your mass is distributed on your body and not concentrated at your center of gravity, it won't be a "pretty spin", but more of an eccentric flopping motion...

Willie Sutton
July 23, 2013, 01:02 AM
"Would you not already be in orbit anyway?"


You're in orbit NOW... around the sun... which itself is in orbit... around the center of the Milky Way Galaxy...

ad infinitum, ad astra...

:neener:


Best,

Willie


.

YZ
July 23, 2013, 01:03 AM
Willie, Occam is calling.

Willie Sutton
July 23, 2013, 01:05 AM
^^ sigh... yes indeed. Not to be confused with Suttons Law... :banghead:


Willie


.

303tom
July 23, 2013, 01:07 AM
Well there is your answer !..................

jim243
July 23, 2013, 01:22 AM
Didn't know the moon had an atmosphere.

Jim

The average daytime abundances of the elements known to be present in the lunar atmosphere, in atoms per cubic centimeter, are as follows:
Argon: 40,000
Helium: 2,000-40,000
Sodium: 70
Potassium: 17
Hydrogen: fewer than 17
This yields approximately 80,000 total atoms per cubic centimeter, marginally higher than the quantity posited to exist in the atmosphere of Mercury.[5] While this greatly exceeds the density of the solar wind, which is usually on the order of just a few protons per cubic centimeter, it is virtually a vacuum in comparison with the atmosphere of the Earth.
In fact, the Moon is often considered to not have an atmosphere, as it cannot absorb measurable quantities of radiation, does not appear layered or self-circulating, and requires constant replenishment given the high rate at which the atmosphere is lost to space (solar wind and outgassing are not primary sources of the Earth's atmosphere, or of any stable atmosphere yet known).

Baron_Null
July 23, 2013, 01:27 AM
I'm not a physics genius by any stretch of the imagination, but it seems to me that the pressure that the powder generates would be slightly higher in space, given the fact that it doesn't have any atmospheric pressure counteracting the pressure inside the chamber.

I could be getting that completely backwards though, given the fact that the bullet would not have atmospheric pressure counteracting its movement.

Even if I'm right in my first assumption, I doubt the difference would be enough to dramatically change the pressures inside the chamber. Could be something to consider if you're planning on using max loads that you developed on earth in space, though.

I'm making myself giggle thinking about reloading manuals stating that you should reduce the powder load and work up to acceptable pressures when planning a trip to the space range.

Willie Sutton
July 23, 2013, 01:42 AM
"I'm not a physics genius by any stretch of the imagination, but it seems to me that the pressure that the powder generates would be slightly higher in space, given the fact that it doesn't have any atmospheric pressure counteracting the pressure inside the chamber."


Lower, actually, as you would not have the bore atmospheric mass opposing the accelleration of the bullet. When you fire a projectile you are expelling two masses with the gas generated by the cartridge: The bullet itself, and the mass of the atmosphere ahead of the bullet in the bore. Remove that mass and you reduce the total mass projected and thus the chamber pressure. BUT this is a VERY slight change, almost purely theoretical: The force needed to engrave the rifling and to overcome the friction of the projectile in the bore is orders of magnitude greater than the small mass of the bore-atmosphere gas.

What is happening *behind* the projectile is no different in a vacuum than in an atmosphere. It's a closed system.

And yes, the moon has an atmosphere. Thin, but...

Willie

.

50 cal
July 23, 2013, 01:44 AM
Am I the only one here that thinks NASA needs to build a shooting range on the moon and NRA members get a membrship discount?:) They spend billions on going to MARS so why not a shooting range on the moon? Makes sense to me:)

jaytex1969
July 23, 2013, 01:47 AM
I would prefer to talk about the proper use of commas and semicolons in this post

Looks to me to resemble haiku format.

OP a poet, perhaps?

Fun new post, OP. Thanks.

I am hoping I never need to apply or remember these new dimensions of theory in a practical application!

Malamute
July 23, 2013, 01:53 AM
I believe Willie Sutton wins the internets for yesterday and today!

Well said sir. Enjoyed reading your posts on the topic.





In case anyone missed that part,

Originally posted by Willie Sutton

...What else? Yes it is rocket science.

(And greetings from Edwards AFB where we teach this stuff at the test pilots school).


Willie

Willie Sutton
July 23, 2013, 02:20 AM
^^ Aw... shucks.... :o

Funny, at the door of the USAF Test Pilot School, where we walk into the school from the flightline, there is a painted sign on the crosswalk that says "this data is good" with the "this" and "is" crossed out and "these" and "are" added above. "These data are good", seeing as how "data" is plural. Usually only test pilots laugh at it. Oh well, need to earn a living somehow. Bank robbery or flying fighters... Hmmm... decisions, decisions...



Willie


.

Quentin
July 23, 2013, 02:39 AM
"Information" also is plural but we tend to refer to it as singular ("information is...") I guess I'll continue to say "data is..." And I'm gonna go fix that crosswalk sign! :D

Interesting thread guys!

JohnFLand
July 23, 2013, 03:26 AM
Willie, you need to re compute how far an object falls on the Earth and Moon after 1 second, etc. You are off by a factor of 2.

Lloyd Smale
July 23, 2013, 08:12 AM
id bet the biggest deterant to getting one to fire would be the extreem cold. id bet not to many firing pins would fall fast enough and powder would be tough to get to burn.

Hanzo581
July 23, 2013, 08:36 AM
I don't have anything scientific to add. But I was just wondering what the laws are for firearms on the moon.

YZ
July 23, 2013, 08:39 AM
There is no water or ice in a vacuum. The firing pin should fall the same way, as long as the firearm is structurally intact. Whether the deeply frozen powder will ignite, good question, I don't know.

Willie Sutton
July 23, 2013, 09:32 AM
"Willie, you need to re compute how far an object falls on the Earth and Moon after 1 second, etc. You are off by a factor of 2."


Quite so... brain segued into velocity late at night: The velocity would be 33 ft/sec^2 after one second, distance about 16 feet. V = gt, where G = accelleration which we will take at 33 ft/sec^2 for imperial units (9.8 meters/sec^2 for metric) and t = time.

D = (1/2)gt^2 where D = distance fallen, t = time of fall, and g = accelleration


Willie

.

Willie Sutton
July 23, 2013, 09:35 AM
"id bet the biggest deterant to getting one to fire would be the extreem cold. id bet not to many firing pins would fall fast enough and powder would be tough to get to burn"


Explosive bolts are used regularly to initiate a variety of things in space.

Mechanical systems generally work the same way as anyplace else, just don't use grease... :eek:

Larger Pyrotechnics, such as those used for parachute deplyment on reentry vehicles do often have heating systems installed though and are heated before use.


Willie

.

YZ
July 23, 2013, 09:53 AM
A normal cartridge primer will surely ignite, you're saying?

45_auto
July 23, 2013, 10:04 AM
Velocity would not be very large since force = 1/2 mass times the square of the velocity of the projectile, and that mass would be small.

You're confused about force and energy. They ARE NOT the same thing. A large mass at a small velocity will deliver the exact same recoil as a small mass at a high velocity, even though the small mass has much more energy due to the squaring of the velocity.

Actually, force = mass times acceleration: F = ma.

What you described is kinetic energy and is irrelevant to recoil forces. Kinetic energy = 1/2 mass times the square of the velocity.

Conservation of momentum will determine recoil velocity. Momentum is mass times velocity, and the momentum of the system (astronaut plus gun plus projectile) will be the exact same before and after firing the weapon.

This means that: mass(astronaut) x velocity(astronaut) + mass(projectile) x velocity(projectile) = 0 both before and after firing his weapon.

For example, a 500 pound astronaut (200 man + 300 suit) firing a 10 pound projectile at 10 feet per second would recoil at the exact same velocity as a 500 pound astronaut firing a 1 pound projectile at 100 feet per second, even though the 1 pound projectile will have MUCH more energy.

It's pretty easy to see using simple algebra.

Before firing 10 pound projectile (assuming a reference point with an unmoving astronaut):

mass(astronaut) x velocity(astronaut) + mass(projectile) x velocity(projectile) must equal 0.

(500 x 0) + (10 x 0) = 0

After firing 10 pound projectile:

mass(astronaut) x velocity(astronaut) + mass(projectile) x velocity(projectile) = 0 since total momentum must remain constant. Solve for astronaut velocity.

(500 x (-.2)) + (10 x 10) = 0 (the minus sign in front of the astronaut velocity means that his velocity will be in the opposite direction of the bullet's velocity)

This tells us that the astronaut would move .2 feet per second in the direction opposite the projectile.

Before firing 1 pound projectile:

(500 x 0) + (1 x 0) = 0

After firing 1 pound projectile:

(500 x (-.2)) + (1 x 100) = 0

This also tells us that the astronaut would move .2 feet per second in the direction opposite the projectile, just like the previous example with the slower 10 pound projectile. This is because both projectiles have the same momentum. The 1 pound projectile at 100 FPS (1 x 100 = 100) has the exact same momentum as the 10 pound projectile at 10 FPS (10 x 10 =100).

Energy wise, the 10 pound projectile at 10 FPS has 15.5 ft-lbs of energy, while the 1 pound projectile at 100 FPS has 155.5 ft-lb of energy. Neither is relevant to the recoil velocity of the astronaut.

This is the same basic stuff that Newton described about 400 years ago, that we used to get to the moon in the 1960's.

You can see how it works in these problems from a 1960 Schaum's Engineering Study Guide. 20-28 and 20-30 are the same thing as firing a gun in space:

http://img.photobucket.com/albums/v682/46auto/Forum%20Posts/rp-1.jpg

And greetings from Edwards AFB where we teach this stuff at the test pilots school

Greetings from AFRL (Air Force Research Lab, up on the hill overlooking Edwards). We've been trying to teach this stuff to pilots for a long time, sometimes they understand it, sometimes they don't!

Art Eatman
July 23, 2013, 01:08 PM
Some forty or so years back, a science fiction story hypothesized a very brief shooting war between a US moon colony and a Russian moon colony. The muzzle velocities of the projectiles was such that a stable orbit was created. The timing was calculated so it would be known when the swarm was expected to arrive at a given location along the path.

This led to a periodic need to grow feathers and "Duck!" as a cloud of projectiles came past.

:D

stanger04
July 23, 2013, 01:13 PM
I don't. Know all the math but if a pistol can fire under water, then I would assume it would fire in space. Then distance would be opposite of course as water is heavy resistance and space is less. The moon has like a 6th or a 3rd the gravity of Earth so the bullet would still drop. Everything has gravity and the greater mass attracts the lesser mass. This of course is a heavily butched paraphrase from an Discovery channel show, lol.

1858
July 23, 2013, 01:36 PM
Imagine this: Shoot a .30-06 parallel to the earths surface and at the same time the projectile exits the muzzle, drop a golf ball from the same height. Both will strike the ground at the same time, as both are falling towards earth at the same rate.

How about Coriolis effects?

Black Butte
July 23, 2013, 06:30 PM
Based on the difference in gravity, and ignoring smaller effects such as atmospheric drag, a bullet fired on the moon will travel the square root of six, or about two and a half, times farther on the moon than it would on the Earth before falling to the ground.

The math is simple! Falling distance is the product of half the gravity with the falling time squared. Plug in six times the gravity of the moon for the gravity of the Earth. Then take the ratio so the distance and remaining gravity term cancel. The ratio of times to fall the same distance is then the square root of six, as stated above. Since the horizontal distance traveled is linear in time, the bullet will go about 2.5 times farther on the moon.

Arizona_Mike
July 23, 2013, 06:50 PM
The escape velocity on the moon is 2.5km/s (7874 fps). What goes up will go down.

Mike

Cryogaijin
July 23, 2013, 06:53 PM
Reading this thread I keep reading things I need to respond to, then Willie posts.

Then I find something nitpicky to comment about Willie's post, and he adds an addendum later. Bah!

A note on temperatures: yes, extreme low temperature will cause wackiness in combustion, however the detonation of the primer would heat things up enough that it wouldn't be an issue. Remember space isn't so much COLD as a perfect insulator for conduction and convection.

OTOH, you would need to worry about ice buildup in the mechanism after you've stopped firing, though that should sublime away pretty quick. And there's vacuum cementing from the soot. . .

YZ
July 23, 2013, 07:01 PM
OK. Does anyone Willie or no Willie know to a certainty: Will a regular primer ignite in cosmic vacuum? Anyone?

Owen
July 23, 2013, 07:06 PM
the pressure difference between vacuum and Standard Pressure at Sea Level on Earth are minimal, as it is only 14psi, vs 55,000-65,000 psi in a rifle.

Now thermal stresses...that could be a problem.

Owen
July 23, 2013, 07:07 PM
YZ, there is no reason why a primer wouldn't detonate in a vacuum. primer detonation is atmosphere independent, and is not even a combustion event.

Jlr2267
July 23, 2013, 07:12 PM
Willie, the distance travelled under constant acceleration is proportional to time^2, therefore if 16 ft after 1 second then 64 ft after 2 sec and 144 ft after 3, etc,...

Panzercat
July 23, 2013, 08:01 PM
Fun fact: Lunar escape velocity is about 5,000 mph or 7k fps.

Carl N. Brown
July 23, 2013, 08:08 PM
The only way a gun could not be fired in space would be if it used the Daisy VL ignition system for caseless ammo: the Daisy VL .22 used a diesel effect with compressed air (containing oxygen) drawn from the surrounding atmosphere, compressed and injected under pressure into solid propellant at the base of the bullet.


I prefer the questions about the TP-82

Life during wartime: I have heard of the russians issuing their cosmonauts a gun the tp82

Life during wartime: plus, what were the russians thinking!

http://en.wikipedia.org/wiki/TP-82

The story I heard was that after cosmonauts returned from space in their capsule slightly off course, and spent the night trapped in the capsule by Siberian wolves until rescue could find them, they demanded there be a survival gun on board each capsule. TP-82 "pistol" was a double barreled 32 gauge shotgun with a lower 5.45x39mm barrel (three barrel drilling); the issue machete in its holster could be clipped to the butt as a shoulder stock. They also issued 32 gauge flare shells. TP-82 was issued 1986 to 2006.

Black Butte
July 23, 2013, 08:38 PM
A fun fact for Firefly fans. In episode 6, entitled "Our Mrs. Reynolds," Jayne shoots his favorite gun, Vera, in space by placing the gun inside a pressure suit.

Jlr2267
July 23, 2013, 09:24 PM
A fun fact for Firefly fans.

Say that 3 times, really fast.

jack44
July 23, 2013, 09:27 PM
Maybe space is anti gun you never know till you get there!.:)

Jcinnb
July 23, 2013, 09:30 PM
Mr Sutton: nice explanation but in the first instance you provided the formula for Kinetic Energy, not force.

Black Butte
July 23, 2013, 09:38 PM
Say that 3 times, really fast.

Hilarious! I didn't even realize the 4F thing when I wrote it.

Bobson
July 23, 2013, 09:45 PM
It would curve downward and hit the surface. Gravity exists there, too.
If the moon has 1/3 the gravity of the Earth, can we conclude that it would only require 1/3 the amount of thrust for an object to leave the moon's gravitational field? In other words, if a rifle was fired at exactly 90 degrees from the surface of the moon, is it remotely possible the bullet would go far enough to reach a point at which the moon's gravity no longer effected the bullet?

YZ
July 23, 2013, 09:47 PM
OWEN

You forgot the deep freeze. Still goes off you think?
This has become a county fair. One show after another. The original question, will the gun fire, is still unanswered.

the count
July 23, 2013, 09:50 PM
So, if you are doing a space walk and for whatever reason the tether to the ship got severed and you start to float away, your trusty little Keltec P9 that you sneaked onbaord could be used to propel you back to the mother ship?

Black Butte
July 23, 2013, 10:12 PM
If a rifle was fired at exactly 90 degrees from the surface of the moon, is it remotely possible the bullet would go far enough to reach a point at which the moon's gravity no longer effected the bullet?

I just did a calculation of the escape velocity from the surface of the moon. The bullet would have to leave the muzzle at 7800 feet per second. I don't even think a .50 BMG case necked down to a .22 LR bullet will get you there.

Willie Sutton
July 23, 2013, 10:27 PM
"Greetings from AFRL (Air Force Research Lab, up on the hill overlooking Edwards). We've been trying to teach this stuff to pilots for a long time, sometimes they understand it, sometimes they don't!"


Ahh, Rocket Ridge! .. I just drove past it on Mercury coming home an hour ago from chow at Domingos in Boron. Stop by TPS in the next week or so and look for the grey MiG. I'll be the one strapping in and sweating. Trade you tours. Good physics lesson too, well done!



"The original question, will the gun fire, is still unanswered"

This is purely a temperature related question. The answer is "Yes". Propellants and primers contain their own oxidizers, so the lack of surrounding atmosphere is not an issue. Impact fired primers would work fine as would the propellant.



"Mr Sutton: nice explanation but in the first instance you provided the formula for Kinetic Energy, not force."

Exhaustion and dehydration after 12 hours on the flightline and three sorties yesterday took it's toll.
I should have gone to sleep... ;-)




Willie

.

grendelbane
July 23, 2013, 10:31 PM
Here is a fun little bit of Moon firearms trivia. You take your 16" naval gun, (like on the New Jersey), and I will fire my AR15 at the same angle, side by side.

Guess which projectile goes the farthest on the Moon?

Remember, those 16" guns would fire over 20 miles on Earth. No AR15 on Earth can fire that far.

But, on the Moon, thanks to the lack of an atmosphere, yes, that dinky .223 bullet will shoot farther. This is because its velocity is higher. SBR AR15s need not apply.

amd6547
July 23, 2013, 10:57 PM
The Russians did experiment with arming a space station and supposedly test fired it:
"...In addition to reconnaissance equipment, Almaz was equipped with a unique 23mm Rikhter (factory index 261P or 225P) rapid-fire cannon mounted on the forward belly of the station. This revolver cannon was modified from the tail-gun of the Tu-22 bomber and was capable of a theoretical rate of fire of 1800-2000 (up to 2600) rounds per minute. Each 168*gram (ammo 23-OFZ-D-R ) or 173*gram (ammo 23-OFZ-G-R) projectile flew at a speed of 850*m/s relative to the station. The cannon had supply of 32 rounds and was tested at the end of the mission, when the station was operating in unmanned mode. To aim the cannon, which was on a fixed mounting, the entire station would be turned to face the threat.
Salyut 3/OPS-2 conducted a successful remote test firing with the station unmanned due to concerns over excessive vibration and noise.
OPS-4 was to have featured two rockets instead of the aircraft cannon, but this system has not been shown publicly and may have never been fully manufactured despite it being used experimentally...."
-Wikipedia.

68wj
July 23, 2013, 11:24 PM
Since it's not in a forest, will anyone hear it?
No sound in the vacuum of space.

YZ
July 23, 2013, 11:27 PM
This is purely a temperature related question. The answer is "Yes". Propellants and primers contain their own oxidizers, so the lack of surrounding atmosphere is not an issue. Impact fired primers would work fine as would the propellant.



.
So you are sure the deeply frozen primer will ignite, no?

Sam Cade
July 23, 2013, 11:42 PM
So you are sure the deeply frozen primer will ignite, no?

Why would the primer be cold?

YZ
July 23, 2013, 11:54 PM
Why would the primer be cold?
Because it is on the Moon. Extreme cold or extreme heat.

JonathanE
July 24, 2013, 12:02 AM
I just tested it. It worked great! I wish I had packed my chronograph.

Sam Cade
July 24, 2013, 12:22 AM
Because it is on the Moon. Extreme cold or extreme heat.

...and no atmosphere to carry off the heat.

http://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law

YZ
July 24, 2013, 01:01 AM
Sam. For energy transfer by radiation no atmosphere is needed.

Let's forget Wikipedia and stay on topic. Will the primer ignite at the drop of the firing pin at -250F, Sam?

Willie Sutton
July 24, 2013, 09:37 AM
"Will the primer ignite at the drop of the firing pin at -250F"


The one empirical data point we have is that the Russians did so with a slightly modified version of a standard aircraft cannon that used percussion primers. We know without any doubt that thousands of explosive bolts have been fired under those conditions, using electric primers. So we have a relatively good confidence level, but no formal proof. Spoke to a scuba diving buddy of mine yesterday who just happens to be a chemist for Federal, developing and testing primer materials. The chemical compositions in primers have no particular low temperature range where they would not behave normally. The metals of the primer cups and anvils are not outside of their working temperature range. So in his *professional* estimation primers would behave normally.

Ther'e nothing like a test in an environmental chamber though. Why don't you invest $100K into a test program and let us know how it works out to validate the above?


Willie

.

Krusty783
July 24, 2013, 10:07 AM
Sam. For energy transfer by radiation no atmosphere is needed.

Let's forget Wikipedia and stay on topic. Will the primer ignite at the drop of the firing pin at -250F, Sam?

If the primer is properly sealed, the only potential chemical issue would be if the constituents freeze out of suspension or something, kinda like freezing the water in a beer, but the alcohol is left in liquid state. This may impact the yield of the charge, but it should still be enough to ignite the powder.

The real issue would be the integrity of the primer case. I don't know how brass holds up in extreme cold like -250 F. The wrong material will be very brittle and shatter like glass when struck by the firing pin, which could either cause the primer to not ignite, or cause bad things if it does ignite.

YZ
July 24, 2013, 10:43 AM
Nah Willie I'll spend it on ammo. I hope the pilots are taught to say "I don't know" when they don't know.

Jim K
July 24, 2013, 03:02 PM
Recoil in space? I hope so, or we wouldn't be there.

Recoil is the "equal and opposite reaction" to the action of a mass (the bullet in a normal firearm) moving forward. The energy of recoil is NOT "half" the energy of the forward movement, it is EQUAL to it. Recoil does NOT occur because the bullet or the gas "pushes" on the air; if that were true, a rocket would not work in space.

Now, consider this. A rocket is propelled by hot gas coming out its back end (please, no bad jokes!). The gas is not solid, like a bullet, but there is so much of it that it has a lot of mass and it is moving at a very high speed.

In a rocket, that gas is the projectile (the "bullet") and the rocket itself moves in a reaction (it is the "gun"). So, in simple terms, man went to the moon on recoil.

Jim

Willie Sutton
July 24, 2013, 05:59 PM
"Nah Willie I'll spend it on ammo. I hope the pilots are taught to say "I don't know" when they don't know."


They do. I didn't know, so I reached out to people who ought to know. I've offered the best data I could find as a result. I invested a phone call to discuss it with a chemist working on primer compounds for Federal, and further bounced it off of a few of the physics guys here today on base. Those guys here are working for a little outfit called NASA Dryden, and one is a pyrotehcnics expert who did work on the shuttle program and is now doing pyro for other space program vehicles. None seemed to think that primers would not function.

Why don't you offer what results you have researched and the sources that you have engaged in order to come to any conclusions that you have reached? Or is your entire involvement asking the same question repeatedly and then dismissing the information that other people are inventing time and effort into obtaining? If you know something that has not yet been brought to the discussion, share it.


Willie

.

Cosmoline
July 24, 2013, 06:03 PM
A more practical question--what happens to sealed cartridges in a vacuum? Do they pop open, and if so what pops out?

Willie Sutton
July 24, 2013, 06:24 PM
Assuming that they were seated at the factory on a standard day and atmosphere, the interior pressure of the cartridge is going to be 14.7 PSIA, the "A" in "PSIA" meaning ABSOLUTE pressure (as referenced to a vacuum, not to the surrounding atmosphere) OK, maybe we compress a tiny bit of air inside as we seat the bullet, but let's work with 14.7 PSIG for starters.

At sea level on earth the pressure inside the case (14.7 PSIA) equals the atmospheric pressure surrounding it (14.7 PSIA), which is what you are exposed to all of the time (at sea level, at 59 degrees F, when the barometer is at 29.92 inches). The bottom line is that the pressure inside the case and outside are about the same and all is well.

Take it to a perfect vacuum and you have 14.7 PSIA inside the case and 0 PSIA outside the case. How much force is exerted on the base of the bullet trying to push it out of the case? Not a lot... for a .30 caliber bullet the surface area is only 0.07 square inches (pi r2, where Pi = 3.14159 and r = radius of the base of the bullet, or half of .30). So 0.07 square inches x 14.7 pounds per square inch = 1.03 pounds, more or less of pressure "forcing" the bullet out of the cartridge. Uhh... that's not a lot. The case grips the bullet far more strongly than that. So... the bullet stays in the cartridge. If there is a leak-rate past the bullet, over time the interior of the case would reach a vacuum. I expect that the bullet forms a perfect seal though.


I can state with absolute certainty that .30 caliber and .50 caliber military ammuniton is not pushed into the cartridge by the pressure of sea water at a depth of 130 feet, having recovered many such cartridges and seen thousands more of them on shipwrecks as a diver, with the cases neither crushed or wet inside. The pressure forcing a .30 caliber bullet INWARDS at 130 feet is about 72 PSI. (pressure found by knowing that 33 feet of salt water = 14.7 PSI, so at 33 feet you have two atmospheres, etc, so use as a formula depth/33+1 = atmospheres absolute, which = 5, and then atmospheres x 14.7 = pressure). and with that same 0.07 square inch surface that force then becomes 5 pounds. If 5 pounds does not press a bullet in, then one pound will not push a bullet out of it's case. There is a particular shipwreck that sank in 1918 that I have recovered .30-06 and .30-40 Krag ammo from, and have found the cases to still be dry inside, thus my speculation that even in a vacuum there would be a zero leak rate of the gas from the interior of the case into the surrounding vacuum.


Willie

.

YZ
July 24, 2013, 08:11 PM
Bud no offense that was the OP question. Can a firearm be fired in space. If you don't know whether the primer goes off in those conditions, you cannot give a straight answer. That's OK, but sure I wanted to get to the bottom of it. I don't research anything unless asked by someone, all I bring here is what's on top of my head.

rcmodel
July 24, 2013, 09:03 PM
I agree.

All the acceleration of a bullet takes place inside the bore of the gun.

If anything, the muzzle velocity would be slightly higher in space then it would be on earth.

Because there would be no air in the bore in front of the bullet that has to be compressed and blown out of the bore in front of the bullet.

As for a dynamite explosion retracting back in onto itself once the initial energy was expended??

BS.
If that were the case, solid fuel rockets would suck up their exhaust smoke plume & explode once the fuel in the rocket engine burned out.

But they don't.

rc

rsrocket1
July 24, 2013, 09:13 PM
Let's say you shoot a 180g 40 cal bullet at 1000 fps.
The reaction will send a 180 pound shooter in the opposite direction 0.14 fps = about 1.7 inches per second or 0.1 miles per hour.

Not particularly fast.

It's also why getting blown across the room by a pistol round is total bunk. The momentum imparted to the person shot is a little less than that imparted to the shooter when the gun is fired, even less if the bullet does not lodge in the body.

Sam Cade
July 24, 2013, 09:14 PM
Sam. For energy transfer by radiation no atmosphere is needed.

Let's forget Wikipedia and stay on topic.


Wait...so you don't understand why blackbody rates are germane?




Will the primer ignite at the drop of the firing pin at -250F, Sam?

There is no reason it would not.

Sam Cade
July 24, 2013, 09:20 PM
The reaction will send a 180 pound shooter in the opposite direction 0.14 fps = about 1.7 inches per second or 0.1 miles per hour.

Not particularly fast.



Boy, it would be annoying if that .1 miles per hour was turned into rotational velocity by being off COM.
:evil:

YZ
July 24, 2013, 09:44 PM
Sam Cade.
First it is not germane it's American.
On a serious note, vacuum has no temperature, but an object such as a cartridge has one. In the absence of solar radiation or other source of energy, it will be very cold.

Devonai
July 24, 2013, 10:13 PM
So, if you are doing a space walk and for whatever reason the tether to the ship got severed and you start to float away, your trusty little Keltec P9 that you sneaked onboard could be used to propel you back to the mother ship?

Spike Spiegel uses this technique in Heavy Metal Queen, episode 7 of Cowboy Bebop.

Sam Cade
July 24, 2013, 10:43 PM
. In the absence of solar radiation or other source of energy, it will be very cold.

True vacuum is a perfect insulator.

In the absence of any sort of conductive media things are going to be slow to lose any heat.



This is why the ISS has enormous radiators and astronauts wear things like LCVGs.

PedalBiker
July 24, 2013, 10:49 PM
On a serious note, vacuum has no temperature, but an object such as a cartridge has one. In the absence of solar radiation or other source of energy, it will be very cold.

Yes, but a vacuum is also a good insulator so things taken into a vacuum will tend to keep their original temperature for a while.

The reason black body radiation is important is that it's the primary way an object can cool in a vacuum.

tahunua001
July 24, 2013, 10:50 PM
an astronaut firing a gun would travel the oposite direction of the bullet with equal force and no the gun would probably fail to cycle.

it would essentially act like an impulse engine propelling the shooter backwards a little faster each time.

in theory, the bullet would travel indefinitely though due to it's small mass would easily be drawn into a planet's or stars gravitational field and burn up in it's atmosphere.

Jim Watson
July 24, 2013, 11:16 PM
A bullet fired in space will assume whatever orbit the combination of vectors of the shooter/gun/cartridge and the fired bullet dictates. That orbit might intersect an astronomical body or not. Or be perturbed by some body's gravity. Shoot carefully and leave a funny shaped asteroid. Probably ought to get a ticket for littering the space ways, too.

Mark T
July 24, 2013, 11:21 PM
Holy whiteboard, Batman.

YZ
July 24, 2013, 11:27 PM
Now we are getting somewhere. The cartridge will be still operational when you step out of the heated lunar module, loaded gun in hand, after the sundown to investigate a disturbance. I can buy that. If you put it down on a moon rock, then it should cool off through conductivity.

AKElroy
July 24, 2013, 11:44 PM
I just did a calculation of the escape velocity from the surface of the moon. The bullet would have to leave the muzzle at 7800 feet per second. I don't even think a .50 BMG case necked down to a .22 LR bullet will get you there.

With conventional rifling and bullet material, it would likely spin apart at that speed, but really slow rifling and a super hard core might get you there. No atmospheric friction to blow it up, so that might work.

Willie Sutton
July 25, 2013, 12:03 AM
"If you don't know whether the primer goes off in those conditions, you cannot give a straight answer"


Both a chemist from Federal Cartridge who specializes in primers, and several engineers at NASA who are experts in the field of pyrotechnics used in spacecraft have assured me that a standard primer will fire.

In the absence of any contrary information, I have a very high confidence level in the accuracy of their opinions. Add to that the empirical evidence that the Russians have done exactly what the OP asked about (reference multiple open source materials RE: Salyut 3), and the evidence offers that "yes you can" is an accurate one.


"The cartridge will be still operational when you step out of the heated lunar module, loaded gun in hand, after the sundown to investigate a disturbance."

Actually "after you walk across the terminator" since there is no "sundown" on the moon... each discrete location is either illuminated, or it's not.



Willie

.

denton
July 25, 2013, 12:22 AM
I just love it when people start talking physics...

Will a cartridge fire in a vacuum? Sure. It makes no difference to a cartridge whether it is atmosphere or vacuum. Firearms do not depend on atmosphere. Whether the firearm is hot or cold is a completely separate issue. Trajectories in a vacuum are much simpler than in an atmosphere.

If the firearm is warm, it will radiate its heat into space as electromagnetic radiation. Here on Earth, you can prove the existence of this phenomenon by viewing warm blooded animals through an infra-red imager. That's why Thermos bottles are aluminized: To reflect the radiation back into the bottle.

Thankfully, the kinetic energy does not split evenly between the firearm and the bullet... not even close. What is conserved is momentum. For any collection of objects without external forces, momentum is unchanged. The momentum of the bullet, gas, firearm, etc. before ignition = the momentum after.

Hence, if you are stuck in space, having drifted away from your ship, holding a sack of cannon balls, you can propel yourself to the ship by throwing cannon balls away from the ship. Momentum of you and the cannon balls before you throw = momentum of you and the cannon balls after you throw.

This is why a rifle begins to recoil before the bullet exits the barrel. The momentum of the rifle + bullet + gas decrees that as the gas and bullet start to move forward, the rifle will begin to move backward to conserve momentum.

Bonus question: How much mass does a Nosler 55 grain bullet have on the Moon? (trick question alert)

YZ
July 25, 2013, 12:24 AM
Just the sunset? I thought the whole sentence cannot be taken literally.
Experts spoke, so settled

Njal Thorgeirsson
July 25, 2013, 12:35 AM
Wait...so you don't understand why blackbody rates are germane?





There is no reason it would not.
Yes, actually there is a reason it would not- The kinetic energy of the firing pin provides the activation energy to initiate the reaction in which the primer compound decomposes. If the primer is extremely cold, it will take a lot more activation energy (faster strike) to initiate the reaction. Perhaps someone could try chilling a primed (uncharged) cartridge with wart-remover (liquid nitrogen) to <-300F and see if it fires. I'll see if i can find some wart remover and I'll try it next weekend perhaps.

HOWEVER, the member you have quoted is also somewhat incorrect in his analysis. Yes, space is -250F (or as low as -450F depending on source). BUT it is so 'cold' because of a lack of molecular activity (there are far fewer molecules floating around in space than in a concentrated atmosphere). For the most part, a hot object must contact a cold one to transfer heat energy. If there are no molecules bumping into the object (the cartridge), then the object will cool down relatively slowly. Things don't freeze very fast in space. In fact, an artificial vacuum is just as cold as space.

Willie Sutton
July 25, 2013, 12:36 AM
"I just love it when people start talking physics..."


And math... :rolleyes:




Willie

Njal Thorgeirsson
July 25, 2013, 12:39 AM
Bonus question: How much mass does a Nosler 55 grain bullet have on the Moon? (trick question alert)

55 grains. :cool:

And your answer was very good! Definitely correct physics right here!

Kernel
July 25, 2013, 12:48 AM
In space, in direct sunlight, could a normal everyday primer, the kind we use here on earth, get hot enough to self-ignite?

(That's a lot of commas for one sentence. Hope I did that right.)

it is not germane it's American....

Is that a Wernher von Braun reference? He was German[e] then became an American. Along the way he did something with rockets and space travel.

a dynamite explosion ... would quickly retract back in onto itself

How would it know to retract back to a single point of origin? As noted, vacuum in space is EVERYWHERE. There is no vector.

denton
July 25, 2013, 01:33 AM
55 grains

You have deftly avoided the first snare. But you were caught by the second.

Jim Watson
July 25, 2013, 01:35 AM
If you think I am going to divide 55 by 7000 and then by 32.2 just to show you I know what a slug is, you are nuts.

Njal Thorgeirsson
July 25, 2013, 01:36 AM
You have deftly avoided the first snare. But you were caught by the second.

And what snare would that be? 55 grains is indeed a measure of mass.

Willie Sutton
July 25, 2013, 01:44 AM
^^ What he said. ... it's mass.


"If you think I am going to divide 55 by 7000 and then by 32.2 just to show you I know what a slug is, you are nuts"


Directly from the Department of Redundancy Department? ;-)

Well done.


Willie

.

TEC
July 25, 2013, 08:03 AM
Well, if any of you are of a certain age, and loved the old 1950's TV show "Men into Space", you would have know from childhood that handguns could be and were fired in outer space. And also, you would have known that Angie Dickinson, Col. McCauley's wife in the TV series, was an absolute babe, even to very young guys. You can check out many of the original episodes on You Tube. Can't remember exactly which episodes involved gunplay, but those damned "Ruskies" were involved, as I recall.

http://www.youtube.com/watch?v=ZcKz6uv9Z6w

Carl N. Brown
July 25, 2013, 08:40 AM
Since black powder contains its own oxidizer (KNO3 potassium nitrate aka saltpetre) a flintlock should fire in space. I can see it in my mnd's eye: Davy Rocket, Final Frontiersman pre-steam punk sci-fi, black powder powered.

45_auto
July 25, 2013, 10:47 AM
Perhaps someone could try chilling a primed (uncharged) cartridge with wart-remover (liquid nitrogen) to <-300F and see if it fires. I'll see if i can find some wart remover and I'll try it next weekend perhaps.

Back in the late 1990's, I was on a project that was using about 3000 gallons of LN2 (liquid nitrogen) every other day.

After work, we used to fill Dewars (basically big thermos bottles) with it and play with it freezing ballons, cokes, food, etc. I can tell you for a fact that if you soak a crescent wrench in it for awhile, then take it out and immediately use it to pry against a bumper, it will break in half very easily!

We also submerged a couple of dozen 45ACP 230 grain lead round nose cartridges in it for a while, then pulled them out and immediately fired them at steel plates.

The normal room temp lead bullets would give you a disk about the size of a quarter when they flattened out hitting the plates. The cryo-bullets apparently just shattered into powder when they hit, all you could find of them looked like little grains of gray sand. Cases and primers looked perfectly normal.

I wish we had also tried some jacketed bullets to see what they would do.

Anyway, out of the couple of dozen cartridges we cryo-froze and fired, they all worked perfectly.

45_auto
July 25, 2013, 10:55 AM
Dupe

tuj
July 25, 2013, 11:01 AM
The Russians did it.

Almaz was equipped with a unique 23mm Rikhter (factory index 261P or 225P) rapid-fire cannon mounted on the forward belly of the station. This revolver cannon was modified from the tail-gun of the Tu-22 bomber and was capable of a theoretical rate of fire of 1800-2000 (up to 2600) rounds per minute. Each 168 gram (ammo 23-OFZ-D-R ) or 173 gram (ammo 23-OFZ-G-R) projectile flew at a speed of 850 m/s relative to the station. The cannon had supply of 32 rounds and was tested at the end of the mission, when the station was operating in unmanned mode. To aim the cannon, which was on a fixed mounting, the entire station would be turned to face the threat.

denton
July 25, 2013, 01:10 PM
If you think I am going to divide 55 by 7000 and then by 32.2 just to show you I know what a slug is, you are nuts.

LOL.... winner, winner, chicken dinner.

55 grains is indeed a measure of mass

That's not the case. 55 grains is a measure of weight, the force of gravity on a mass.

With a name as eloquent as yours, I'd almost bet the farm that you grew up with a much more sensible system of measures that we usually use here. So rather than converting to slugs, I'd probably just say 3.56 grams.

So you obviously realized that mass is the same, whether you're on the Moon or on Earth, even though the weight is different. A 55 grain bullet has the same mass both places, but grains are the wrong unit of measure for mass.

Quentin
July 25, 2013, 01:32 PM
This really is a fun thread! Neil Armstrong should have tested a 1911 and M16 back in July 1969! Maybe Heinlein's bullet swarm might still be in low orbit today! :D


Errr... Ben Bova? Men of Good Will?

DanTheFarmer
July 25, 2013, 11:47 PM
Hey Denton!

I was going to write something similar to you. I knew there are 7000 grains to a pound and that a pound is a unit of weight, not mass; therefore grains are a unit of weight.

When I double checked on Wikipedia it said that the grain was a unit of mass. After reading your comment I double checked the double check with other sources (Britainnica On line)and they say the grain is a unit of weight.

Unless someone puts a good case forward I going with grains being a unit of weight.

We really know how to have a good time on this thread, huh? Party!

Dan

rcmodel
July 26, 2013, 12:06 AM
But?

The OP's only question was, can a firearm be fired in space?

The only correct answer is, Yes, it can.

rc

YZ
July 26, 2013, 12:40 AM
We also submerged a couple of dozen 45ACP 230 grain lead round nose cartridges in it for a while, then pulled them out and immediately fired them at steel plates.

The normal room temp lead bullets would give you a disk about the size of a quarter when they flattened out hitting the plates. The cryo-bullets apparently just shattered into powder when they hit, all you could find of them looked like little grains of gray sand.


An excellent experiment. This beats any speculation.

Malamute
July 26, 2013, 12:43 AM
But?

The OP's only question was, can a firearm be fired in space?

The only correct answer is, Yes, it can.

rc


Yeah, but,..but,..that isnt nearly as much fun as 5 pages of thread drift and discussion. :D

Black Butte
July 26, 2013, 01:30 AM
Visual proof guns fire in space at 0:17. :)


http://www.youtube.com/watch?v=uACR_WgOgrw

Jim Watson
July 26, 2013, 01:37 AM
Not! Momentum IS created by converting your dinner into energy. You are using your muscle energy to push off from, applying force against, the canon balls and converting that bio-mechanical energy into linear momentum of your body towards your spaceship.

Can you say "vector moment?" Sure you can.

Creating momentum.

I see it as converting muscular effort/blood sugar oxidative energy into kinetic energy of the cannonball.
Momentum, being a conserved vector quantity, is equal in opposite directions and sums to zero.

Unless you are Aarn Munro with the engine room of the spaceship Sunbeam packed with aggie coils charged with raw momentum.

denton
July 26, 2013, 02:16 AM
Yes, momentum is conserved. Force is not. Kinetic energy is not. Momentum is.

As a further little doodle, momentum=mv. Kinetic energy = [integal] mv =1/2mv^2. Force = [derivative] mv = m dv/dt = ma.

If you want to talk about dinner being converted to kinetic energy, that's valid. Nevertheless, momentum is conserved.

In the cannonball example, if you and your spacecraft are at rest, and you throw cannonballs in the direction opposite the one you want to go, dinner does indeed get converted to kinetic energy. The thrown cannonballs move one way, and you and the sack of remaining cannonballs moves the other. But the center of mass of you and all the cannonballs never moves. For it to move, it would have to be acted on by an external force. F=ma requires that absent that external force, the center of mass doesn't move.

tuj
July 26, 2013, 02:19 AM
The answer is simple. Yes firearms can be fired in space. The Russians actually tested this with their rotary cannon mounted on their space station.

CapnMac
July 26, 2013, 04:43 AM
For the most part, a hot object must contact a cold one to transfer heat energy.
Which is the "why" of the size of the radiators on the ISS.

Which is very much like pouring boiling (100C) water into a 98C heated pot to "cool" it. Or thawing ice by placing it on a 1C plate (sublimation might "win" in that circumstance).

Actually, where the physics would get "interesting" would be upon bodies like Eros or Ceres, or, say moons, such as Mars' Phobos and Deimos--where the gravity is very low. So low as to be functionally "microgravity"--like that experienced on the ISS--despite being several orders of magnitude greater. IIRC, the EV for Ceres is in the 75-150fps range.

Nifty trivia--the ISS is a long ways up there, that 260 miles into the sky. However, on a 16" diameter desk globe, that's only half an inch or so. For our metric readers, ISS orbits at 417KM, on a 40.61cm globe that's 13mm--given that ISS is only 78m long, that's about 0.03mm long to scale.

That is, unless I've messed up the calculations from starting with a perverse ratio of 30.32cm = 6371km
Our world here has a very fractal scale--Everest is only a tenth as tall as the ISS--about 5/100" (1.3mm) high on our putative globe; Challenger Deep in the Marianas Trench would be a bit more than 0.07" (1.77mm) deep.

45_auto
July 26, 2013, 09:11 AM
That's not the case. 55 grains is a measure of weight, the force of gravity on a mass.

No, 55 grains is a measure of mass, not weight. No gravity involved. A bullet that masses 55 grains on earth would also mass 55 grains on the moon.

The exact same bullet will weigh .00786 pounds on earth, and .00131 pounds on the moon.

Grains are a measure of mass just like grams or slugs. The grain or troy grain (Symbol: gr) measure has been defined in terms of units of mass in the International System of Units as precisely 64.79891 milligrams

Unfortunately, most people don't understand the difference and refer to grains, grams and kilograms as "weight" on earth.

If someone "weighs" 80 kilograms on the earth, they will also "weigh" 80 kilograms on the moon. The correct term in quotes would be "mass".

The corresponding unit to the pound (weight) in the metric system is the Newton, but no 40 kg woman wants to admit that she weighs 392 Newtons!

denton
July 26, 2013, 01:13 PM
First, there is no NIST standard for weight. Weight varies by a few to several tenths of a percent at various locations on the surface of Earth, so there can be no standard. Instead, NIST holds a standard kilogram which is a unit of mass.

Ever helpful, NIST has provided a standard definition of the acceleration of gravity, and that allows us to convert back and forth between units of weight, such as Newtons, pounds, and ounces, to units of mass like slugs and grams.

Unconstrained by man-made definitions, gravity does what gravity does. The definition is just a convenience that is meant to be helpful.

Well, maybe it's not all that helpful, because it facilitates the casual interchangeable use of weight and mass in non-technical literature. You can see a glaring example of this at Wikipedia, http://en.wikipedia.org/wiki/Grain_(unit)

The NIST Handbook 44 defines a grain as precisely 1/7000 of a pound. A pound is a measure of weight (force of gravity on a mass). If a grain is 1/7000 of a pound, a grain is a measure of weight as well.

Even NIST will occasionally reference pounds as though they were masses. When they do, it is by invoking the standard definition of the acceleration of gravity. They do that in Handbook 44, which doesn't help the confusion. (weight = mass x acceleration of gravity) If NIST does it, then I guess it won't hurt if we casually refer to a grain as a unit of mass, so long as we hold in mind that it is not really so, and we are invoking a unit conversion based on a standard definition of g.

A pound is a unit of weight, a grain is a fraction of a pound, so a grain is a measure of weight.

When you get around to firing your firearm in space, it will be the mass of the bullet that will be of concern in determining muzzle velocity, not the weight of the bullet.

TEC
July 26, 2013, 02:39 PM
Denton:

Technically, the Newton is a fundamental unit of force - (1 kg*m/sec**2), where in lies one of the most fundamental relationships in classic fizzix:

F=MA, force = mass x acceleration The formula and its implication -- that the universe is just a giant machine, that, once having been set in motion, has entirely predictable outcome, over time, independent of the influence of God. I think that (and perhaps some other things?) got him excommunicated.

Weight is also unit of force, usually thought of in terms of the force exerted on any mass by another mass by the gravitational force (Fg), or in the case of "Pounds", the mass of a person or object affected by the acceleration due to earth gravitational force (Fg), about 32ft/sec*sec if I remember correctly. Weight on the moon would be the force exerted on the same mass by the moon's gravity, etc.

Mass is conserved. Gravity is a fundamental universal force that depends, I believe, on the mass of an object.

When it all get too confusing, and my mind starts to ramble, I just try to remember what rhymes with mass and then think fondly, instead, of Angie Dickenson and my childhood, and one of my first favorite TV shows, "Men into Space"
Angie was, of course, the first TV astronauts wife and, IMO, the female counterpart of the Duke, John Wayne in all of my black and white memories.

http://cache4.asset-cache.net/gc/74261190-john-david-carson-looking-at-angie-dickinson-gettyimages.jpg?v=1&c=IWSAsset&k=2&d=X7WJLa88Cweo9HktRLaNXqnpQsn7DP3EW%2B6rn9u1PxrUhJKr1iT4JzkLAzKI1jeJlom9r7GhxHAbu6bRR6boVw%3D%3D

denton
July 26, 2013, 03:11 PM
Technically, the Newton is a fundamental unit of force

Exactly.

Newtons and pounds are units of force. Weight is a force.

double bogey
July 26, 2013, 07:45 PM
Ok, we had someone fire an assembled bullet that was about -320F. Now we got to get him to do it in a vacuum, with lo/no gravity.:evil:

denton
July 27, 2013, 12:29 AM
Matt.. Matt... Matt... Reason with me.

Does F=ma? I think you have to agree that it does. Everyone should recognize and accept that basic formula. F is the sum of all externally applied forces, m is mass, and a is acceleration

So think about you and a sack of cannonballs, out in space.

You and the cannonballs have a center of mass, no? Of course you do.

Now if there are no external forces applied to the center of mass of you and the cannonballs, then F=0. If F=0, then a must be 0. If a=0, the center of mass of you and the cannonballs is not changing speed or direction, i.e, is not accelerating.

So when you push a cannonball away from you (that's an internal force, and does not count as part of F on the center of mass), some or all of the rest of the system has to move in the opposite direction, else the center of mass will move. And that would violate F=ma.

It's the principle that propels rockets.

It's also one of the grand laws of physics. It holds true on a quantum mechanical scale, and it holds true in relativistic mechanics. It's one of the pillars.

If you can get a copy of Hatcher's Notebook, he has a very nice discussion of how it applies to firearm recoil.

BTW, in space, without friction or gravity, you actually do get the results that conventional recoil calculations predict. Here on Earth, with the rifle against your shoulder, not so much.

climbnjump
July 27, 2013, 01:00 AM
Hence, if you are stuck in space, having drifted away from your ship, holding a sack of cannon balls, you can propel yourself to the ship by throwing cannon balls away from the ship. Momentum of you and the cannon balls before you throw = momentum of you and the cannon balls after you throw.

Well, yes but...

So when you push a cannonball away from you (that's an internal force, and does not count as part of F on the center of mass), some or all of the rest of the system has to move in the opposite direction, else the center of mass will move.

Yeah, there we go. If you meant an overhand throw in the first quote, you wouldn't quite get the desired affect, right? Conservation of angular momentum and all?

TEC
July 27, 2013, 01:08 AM
Denton: Do you mean that in a dynamic system, every action has an equal and opposite reaction?! Very interesting. If that's so, then not only the systems mass, but also its momentum (and energy) would be conserved. Cool.

BTW, n the first episode of Men into Space, (just watched it on U-Tube last night) Col McCauley gets saved after he the gets knocked off the space ship, while on a space walk (with magnetic shoes) so he can use a cutting torch to cut a stuck coupling on the spaceship's booster. His crew track him down, fly the ship to where he is drifting away, and, with the rocket engines still ablaze, throw him a rope from the open hatchway as they pass. Pretty exciting stuff for the 1950's

So, i guess if you can fire a gun in space, then using a cutting torch works too, and throwing a rope from a moving space craft is also relativistically easy, as long as you thought to bring extra rope and a cutting torch along for the space trip.

The spaceship's name was the XMP-13 (experimental moon probe). I guess XMP-13 was the TV forerunner of Apollo 13, huh. And remember, LSMFT.

Art Eatman
July 27, 2013, 10:21 AM
Back some sixty years ago, dividing the weight (aardvark pounds) by "g" gave what were then called "poundals". That way you could differentiate between plain old weight and the mass for calculations for impulse, momentum, energy, etc. Dunno if that convention still holds.

splattergun
July 27, 2013, 10:50 AM
I am referring only to the idea of firing a gun in the vacuum of space here:


Physics was a long time ago but a similar topic actually came up about whether a dynamite explosion would expand forever and the professor gave an explanation that was not what I expected. According to him, since space is a vacuum, the explosion would occur, (Just like gun powder, dynamite has all of the essential chemicals required to oxidize),but it would quickly retract back in onto itself once the initial energy was expended and the force (or lack thereof) of the vacuum was greater than the remaining energy in the explosion. It was his opinion that most of the debris ( Mostly paper and carbon I would expect) would retract back into the vacuum.

I believe that the bullet would gain a lot of momentum and would continue to travel much further than it would on earth but I do not believe that the expansion of gases would reach near the same level that it would within an atmosphere and the bullet would not achieve near the same max velocity.

Just my own logic. But this would be a great experiment just for giggles.
this professor's hypothesis forgets other aspects of physics which affect the explosion. Mass, gravity, momentum, etc. There have been explosions in space. Apollo 13, for one. No retraction of gasses there. The debris field is still detectable to those tracking space junk. It is likely expanding, due to the gravity of the moon pulling the debris.

Another explosion, much larger, is a nebula. A star explodes, the gas and debris continue to expand until the gravitational fields of other bodies affect the momentum. The mass begins to stabilize in form and pockets of more mass begin to contract in on itself.

It is gravity that causes material from explosions in space to contract. Other bodies' gravity will pull in part of the debris as well.

The debris from a gunshot in space would soon be pulled toward the object of greater mass. Earth, in this case.

dmazur
July 27, 2013, 10:54 AM
Dunno if that convention still holds.

From this source -

Poundal (http://en.wikipedia.org/wiki/Poundal)

English units require re-scaling of either force or mass to eliminate a numerical proportionality constant in the equation F = ma. The poundal represents one choice, which is to rescale units of force. Since a pound of force (pound force) accelerates a pound of mass (pound mass) at 32.174 049 ft/s2 (9.80665 m/s2; the acceleration of gravity, g), we can scale down the unit of force to compensate, giving us one that accelerates 1 pound mass at 1 ft/s2 rather than at 32.174 049 ft/s2; and that is the poundal, which is approximately 1⁄32 of a pound force.

The poundal-as-force, pound-as-mass system is contrasted with an alternative system in which pounds are used as force (pounds-force), and instead, the mass unit is rescaled by a factor of roughly 32. That is, one pound-force will accelerate one pound-mass at 32 feet per second squared; we can scale up the unit of mass to compensate, which will be accelerated by 1 ft/s2 (rather than 32 ft/s2) given the application of one pound force; this gives us a unit of mass called the slug, which is about 32 pounds mass.

Yes, I remember the poundal. I have not encountered it since grade school, which was a while ago.

As explained above, poundals and slugs are two different approaches to the same problem and are not used together. Unless "mass hysteria" is desired... :)

dmazur
July 27, 2013, 11:14 AM
...the force (or lack thereof) of the vacuum was greater than the remaining energy in the explosion...

Well, this is the first time I've seen "vacuum" described as a force.

An explosion under water creates a temporary low-pressure region, once the chemical reaction of the explosive stops. Water rushing back creates a force which seeks the lowest pressure outlet (the side of the bubble nearest the surface.) I understand this is what creates the geyser effect from something like a depth charge set "shallow" rather than "deep".

However, a vacuum isn't a fluid but is, of course, nothing. So I believe the "bubble collapsing" description was misapplied.

aka108
July 27, 2013, 11:18 AM
Does it really matter or will a correct answer change the course of Western civilization? None of us will go there to find out.

Clark
July 27, 2013, 11:29 AM
When we shoot a rifled gun on earth, the rotational reaction on the shooter gets offset by the rotational reaction of the target. The earth stays on the same path.

But in outer space when you shoot a gun, you never get rid of the spin. You can average it with your big space ship when you come back from your space walk. But the other cosmonauts will complain, "Hey! Stop bringing all that spin in here!"

jim243
July 27, 2013, 11:40 AM
It was his opinion that most of the debris ( Mostly paper and carbon I would expect) would retract back into the vacuum.

Interesting, creating a vacuum within a vacuum, not likely. That only works where there is atmospheric pressure to push the material back into the vacuum.

Jim

barnbwt
July 27, 2013, 11:47 AM
"Can Firearms be Fired in Space"
I think the little skirmish our boys had with their Russian counterparts on the Moon speaks for itself. Tragic misunderstanding, really; the cosmonauts merely needed a lift home since theirs was a one-way mission.

:D :D :D

TCB

YZ
July 27, 2013, 11:58 AM
Unfortunately it was the astronauts who needed a lift both ways from the Russians after the shuttle program was grounded.

Anyhow, I just came back from space. Turns out a certain Senator [moderator watching] has been there for some time. So NO THEY CAN'T.

Robert
July 27, 2013, 12:27 PM
Ok let's call this one asked and answered. And then some.

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