Guns in Space

[JohnRich 4]

News:

Guns In Space: Still Just Science Fiction

"The idea of taking guns into space has a long and scientifically…um…questionable history. It hasn’t been done much in real life but literature abounds with fictitious examples. We’ve been speculating about heat rays, Phasers, and Imperial Laser Blasters for ages, but where does science take you when you start thinking about shooting real guns in space?

"With that in mind, I thought I’d add some more completely useless space shooting tips of my own..."

Full story: Truth About Guns.com
Another: Live Science.com

Good tips for shooting in space. Watch out for that bullet that orbits all the way around a planet and comes back around and hits yourself in the back. That would suck.

This is intended to be a discussion about the subject of the physics of shooting guns in space.
Please keep politics out of it.

[AggieDave 6]

Shouldn't that read,


"Guns...



in SPAAAAAAAAAAAAAAAccccceeee!"

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[kallend 1,625]

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News:

Guns In Space: Still Just Science Fiction

"The idea of taking guns into space has a long and scientifically…um…questionable history. It hasn’t been done much in real life but literature abounds with fictitious examples. We’ve been speculating about heat rays, Phasers, and Imperial Laser Blasters for ages, but where does science take you when you start thinking about shooting real guns in space?

"With that in mind, I thought I’d add some more completely useless space shooting tips of my own..."

Full story: Truth About Guns.com
Another: Live Science.com

Good tips for shooting in space. Watch out for that bullet that orbits all the way around a planet and comes back around and hits yourself in the back. That would suck.

This is intended to be a discussion about the subject of the physics of shooting guns in space.
Please keep politics out of it.

Depends on the spacecraft orbit and muzzle velocity of the round, but even pointing the gun straight down, the bullet would almost certainly miss the Earth if fired from a spacecraft in a stable orbit. In fact, pointing in ANY direction and you'd still likely miss the Earth unless in very low orbit.

...

The only sure way to survive a canopy collision is not to have one.

[DanG 1]

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Depends on the spacecraft orbit and muzzle velocity of the round, but even pointing the gun straight down, the bullet would almost certainly miss the Earth if fired from a spacecraft in a stable orbit. In fact, pointing in ANY direction and you'd still likely miss the Earth unless in very low orbit.

What if you're aiming at the broad side of a barn on Earth?

- Dan G

[JohnRich 4]

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Good tips for shooting in space. Watch out for that bullet that orbits all the way around a planet and comes back around and hits yourself in the back. That would suck.

Depends on the spacecraft orbit and muzzle velocity of the round, but even pointing the gun straight down, the bullet would almost certainly miss the Earth if fired from a spacecraft in a stable orbit. In fact, pointing in ANY direction and you'd still likely miss the Earth unless in very low orbit.

Explain, please. Is the bullet going to achieve escape velocity and break away from an orbital trajectory, to go flying off in space? Perhaps to land on Mars?

Even if not that, would a bullet burn up and disintegrate upon entering the atmosphere, so that it would never reach the ground?

[kelpdiver 2]

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Depends on the spacecraft orbit and muzzle velocity of the round, but even pointing the gun straight down, the bullet would almost certainly miss the Earth if fired from a spacecraft in a stable orbit. In fact, pointing in ANY direction and you'd still likely miss the Earth unless in very low orbit.

what's "very low" in this context? All manned orbital flight is pretty low. Even with the massive perpendicular vector of the orbit, doesn't the bullet just need to get a wee bit lower to start getting some atmosphere (drag)?

Does suggest we need to move on to lasers, post haste. Or we need to get our Beretta 92s from Hong Kong so the magazines are bottomless pits.

[quade 3]

Without reading the articles to see how the author approached the subject, to me, physical bullets make very little sense. The biggest issue, I think, would be Newton's 3rd law and how the shooter maintains control of his own body after the first shot. This scales up to guns on ships as well. You'd want your main guns in-line with your center of gravity and smaller guns spaced around it and firing in sequence in an attempt to keep the main gun on target.

The other thing you'd have to worry about is how the recoil affects your orbit. Yes, you can correct for this, but it means that for every bullet you fire, computers have to figure out how it affects orbit and thrusters have to fire to fix it which simply wastes fuel.

The idea you'd somehow fire a bullet and it would make an orbit and hit you in the ass is silly. The bullet will probably either burn up in the atmosphere or head off into deep space. Very few will remain in orbit. The odds are, you're more likely to be hit by another piece of space debris.

All in all, I think recoilless energy weapons like lasers are the way to go.

quade -
The World's Most Boring Skydiver

[kallend 1,625]

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Depends on the spacecraft orbit and muzzle velocity of the round, but even pointing the gun straight down, the bullet would almost certainly miss the Earth if fired from a spacecraft in a stable orbit. In fact, pointing in ANY direction and you'd still likely miss the Earth unless in very low orbit.

what's "very low" in this context? All manned orbital flight is pretty low. Even with the massive perpendicular vector of the orbit, doesn't the bullet just need to get a wee bit lower to start getting some atmosphere (drag)?

.

Low enough that atmospheric drag causes orbit degradation over the attention span of the gunman.

...

The only sure way to survive a canopy collision is not to have one.

[aarco 0]

The coolest thing about Halo - is the liping effect of the Letrockx Ring and other learner level ways -- Most weapons are energy typic- and based physically on spacial frequency - - A charge must come from a sensor that has a read in the environment- most of these networks are built with AIs - in physical law and Magic weapondry - we learn a great deal more then just shot -- bang-- or mixture sciences from power to powder-- you have to be linked to the balance of it all - and finding the answers the ones would be looking for on strange new worlds - or old ones filled with pain and memories of old and lost battles - -- a laser or light force- energy gathered from other places and designed for a perpuse - kill the monster ranggorn with your blaster without having to deal with the stupid caughing art of poor clearical meaning -- laughing is fun -- but come on man - not while your home-world is being invaided -- if thats how you spell that:-)(-: O pO %4@$ &*^Metal liquid dream door - jack just landed- not thinking about just killing something - but new pie has a direction - but don't forget the floor - issue distance.

Having something never beats doing (>|<)
Iam building things - Iam working on my mind- I am going to change this world - its what I came here 4- - -

[lawrocket 3]

I like what kallend wrote. But it’s got me thinking of what would happen.

Let’s say a person has an M-16. It’s got a muzzle velocity of about 950 meters per second. Then let’s say that somebody is out floating on an MMU outside the ISS. The ISS has an orbital velocity of about 7700 m/s and an altitude of about 360 km. So that’s the starting altitude and velocity relative to earth. It completes one orbit every 91 minutes.

So let’s say some spacewalker shoots off the M-16. The muzzle velocity will be 950 m/s relative to the spacewalker. Depending on the mass of the spacewalker, the spacewalker could be blown in an opposite direction, but let’s assume that the round left at 950 m/s relative to the spacewalker. First question is: in which direction was the round shot?

If the round was shot exactly in the opposite direction of the shooter, you’ve just knock the round’s velocity down to 6750 nm/s at the point of the orbit where the shot occurred. Because velocity and orbit cannot be separated, what you’ve done is (assuming the ISS orbit was circular) is changed the orbit to an elliptical orbit with a lower perigee on the far side of the earth while giving the round a higher average speed around the earth. (lower orbits mean higher speed relative to earth and shorter orbital periods).

STS-36 was one of the lowest orbits attained by a shuttle - about 210 km. Its orbital period was 88.5 minutes – 2.5 minutes quicker than the ISS because of its lower altitude/higher speed relative to earth.

Not knowing the precise mathematics, however, I don’t know whether or not clipping a 950 m/s off of the orbital velocity of the round would be enough from the 350 km altitude to put the round’s perigee in the earth’s atmosphere. But it’s possible. If it’s not, though, that round will fly through the same spot where it was fired after one orbit so long as atmospheric drag doesn’t slow it down. Fortunately, the EVA astronaut would be a minute or so behind it.

Shooting in the direction of travel would have the opposite effect – it would make an elliptical orbit with the high point on the other side of the earth, slow down to total orbital time and average orbital velocity, and make the round be a few seconds later at intercepting the spacewalker.

Also interesting to me – how quickly would the orbit decay? That round is going to maintain its spin. It’ll cut more easily through the thin atmosphere than would a less aerodynamic object.

edited to add: like kallend said, anything but a very low orbit or a large enough delta v (where the delta-v would put the round in the atmosphere at perigee) would cause the earth to be missed entirely.

My wife is hotter than your wife.

[rehmwa 2]

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over the attention span of the gunman.

I'll agree since you put a time limit on it.

...
Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants

[rhaig 0]

from the second link:

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The only difference between pulling the trigger on Earth and in space is the shape of the resulting smoke trail. In space, "it would be an expanding sphere of smoke from the tip of the barrel,"

This would only be true if the gas had no force behind it correct? We're still talking about pressurized gas leaving a confined space. Yes, the shape of the smoke trail would be different, but not an expanding sphere.

--
Rob

[JohnRich 4]

Picking up your spent brass for reloading is going to be much more difficult too. That stuff is going to be floating around all over the darned place!

But hey, you don't have to worry so much about elevation adjustments to compensate for bullet drop from gravity.

[billvon 2,400]

>but even pointing the gun straight down, the bullet would almost certainly miss the
>Earth if fired from a spacecraft in a stable orbit.

Indeed, about the only way to make sure it WOULD hit the earth would be to fire it retrograde to the orbit. You need about 66 meters/second to deorbit from ISS altitudes and most guns can achieve that. (Indeed that would be a great way to dispose of waste on the ISS since it would not only get rid of the waste, it would also keep the station in orbit.)

If you fired it straight down, from the astronaut's perspective, it would drop away from the station without any change in velocity. Dropping down puts it in a lower orbit; this results in it moving faster relative to objects in higher orbit. This results in it going into a higher orbit. Thus over the course of 45 minutes the shooter would see the bullet drop towards the planet, start moving faster, then rise above him and move into a higher orbit. If you had a high enough muzzle velocity you could hit the atmosphere before it started to rise again but it wouldn't be easy.

One of the old standards in science fiction is the shooter who stands on the surface of a moon* and fires his gun at someone on the horizon. He is then somehow made to reappear in the same place one orbital period later to be killed by the bullet from his own gun, returning one orbital period later. This is of course very unlikely for several reasons but is theoretically possible.

(* - for our moon you'd need a muzzle velocity of around 2000 m/s, which would be unlikely.)

Some other notes:

Most projectile weapons will be fairly useless in space. Most spacecraft (EVA suits included) are armored against micrometeorites that are orders of magnitude lighter than, but an order of magnitude faster than, bullets, giving you a similar energy. The Orbiter was hit by several tiny bits of junk over the years, blowing holes up to an inch across in it - fortunately in areas that were not mission critical (like the radiators.)

High muzzle velocities will make fairly effective reaction engines, and would allow you to change your velocity. Firing 22 rounds from an M-16 would change your velocity by 1mph (assuming a 200 lb person in a 200 lb spacesuit.) One science fiction premise is that freefall "gunships" would have a single gun, used alternatively as a means of propulsion and as weapon.

[lawrocket 3]

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You need about 66 meters/second to deorbit from ISS altitudes and most guns can achieve that

Gotta thank bill for doing the math.

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Dropping down puts it in a lower orbit; this results in it moving faster relative to objects in higher orbit. This results in it going into a higher orbit.

Okay. I’m visualizing this. Shooting straight down would at once lower the orbit and increase the velocity relative to the earth. In that case the orbit would move from circular to an elliptical orbit that is higher at both foci, right? Because it’s straight down the tangential velocity of the round is unaffected but the gravitational thrust was affected momentarily.

So in, say, 15 minutes the round will be below and ahead of the astronaut but at 45 minutes the round will be above and behind the astronaut. Then at 70 minutes it will be below and ahead of the astronaut again only to below and behind at 85 minutes.

Come to think of it, assuming perfect orbits, would a round fired at exactly at the direction of gravity actually hit the astronaut in 22.5 minutes if some maneuver was not accomplished? It seems that the circular and the elliptical orbits would intersect at four points versus the single point when tangential thrust is applied.

My wife is hotter than your wife.

[billvon 2,400]

>So in, say, 15 minutes the round will be below and ahead of the astronaut but at
>45 minutes the round will be above and behind the astronaut. Then at 70 minutes it will
>be below and ahead of the astronaut again only to below and behind at 85 minutes.

"Behind" and "ahead" are hard to relate to here but you'd basically overlay a more elliptical orbit on top of a mostly circular one. (The ISS is in a mostly circular orbit; it varies from a perfect circle by about 15 miles.) From the astronaut's perspective he'd see it do a big circle around him, intersecting with him (in a perfect world) twice per orbit.

BTW the first time this became a problem was during the Gemini missions. Astronauts would see the target ahead of them, so they'd thrust towards it. That would increase their orbital speed, so they'd rise above it. That would make them want to thrust downwards to get back in line with the target. If done near apogee that would result in them descending more rapidly than expected (descending part of the orbit + downward thrust) so they'd end up below it. But now they'd overtake it because they were in a lower orbit going faster . . .

If you plotted it from the point of view of the astronaut it would look like the target was doing this helical rotation around the astronaut's vehicle. The first astronauts referred to this embarrassing flight path as a "whifferdill."

[lawrocket 3]

I would have reckoned there were four intersections in the orbits. As a person who never even took physics, I’ll take your word for it.

Yeah. I recall on the first spacewalk mission with McDivitt and White that the first objective was to rendezvous with the upper stage of the Titan and was unsuccessful because orbital mechanics were counterintuitive to pilots and McDivitt just couldn’t get it right. Needless to say they’d gotten it pretty well mastered by the time Apollo 9 came along and McDivitt & Schweikart had no choice but to successfully rendezvous or die.

The whifferdill became a plague of the astronauts seeking to rendezvous because it burned so much fuel. Michael Collins wrote much about the whifferdill he and Young experienced docking with the Agena because apparently the guidance platform was out of plane in the Gemini capsule itself, which required the manual corrections once they got close.

Those astronauts were always in competition as to who could do tasks using the least amount of fuel.

My wife is hotter than your wife.

[dannydan 0]

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All in all, I think recoilless energy weapons like lasers are the way to go.

i want one in .45-70!

[airtwardo 6]

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All in all, I think recoilless energy weapons like lasers are the way to go.

i want one in .45-70!

WITH a Trapdoor!

~ If you choke a Smurf, what color does it turn? ~

[jgoose71 0]

Look, space is big!!! During my time I spent as the tail gunner in the space shuttle, I was never hit by any of my own rounds!

The size of space is what keeps most of our satellites from running into each other and being struck by meteorites and such!!!

"There is an art, it says, or, rather, a knack to flying. The knack lies in learning how to throw yourself at the ground and miss."
Life, the Universe, and Everything

[quade 3]

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The size of space is what keeps most of our satellites from running into each other and being struck by meteorites and such!!!

Oh my . . . no.

http://online.wsj.com/article/SB123438921888374497.html

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

quade -
The World's Most Boring Skydiver

[ZigZagMarquis 8]

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Picking up your spent brass for reloading is going to be much more difficult too. That stuff is going to be floating around all over the darned place!

Yeah, but I still bet there would be some idiot range master or moron in the next stall that tried to snake your brass anyways!

[pchapman 261]

Orbital mechanics sure are fun to get your head around, with all their counter-intuitive aspects.

As for actual guns in space, I'd think the only ones would be on the Soviet Almaz manned military reconnaissance space stations, orbited in a couple of the missions identified as Salyut.

(Or did anyone have any sort of weapon stashed in some survival kit? Unlikely but I don't know.)

Internet sources are a little unclear on the details, even when one digs to the specialized space sites, beyond just Wikipedia.

But it sounds like the adapted aircraft cannon may have been test fired on Salyut 3 when crew were not aboard. The cannon was fixed to the station structure, so the whole station had to be maneuvered to aim it.

Like the Soviet moon program, it's all cool cold war era activity that only came to light afterwards.

[Niki1 1]

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Without reading the articles to see how the author approached the subject, to me, physical bullets make very little sense. The biggest issue, I think, would be Newton's 3rd law and how the shooter maintains control of his own body after the first shot. This scales up to guns on ships as well. You'd want your main guns in-line with your center of gravity and smaller guns spaced around it and firing in sequence in an attempt to keep the main gun on target.

The other thing you'd have to worry about is how the recoil affects your orbit. Yes, you can correct for this, but it means that for every bullet you fire, computers have to figure out how it affects orbit and thrusters have to fire to fix it which simply wastes fuel.

The idea you'd somehow fire a bullet and it would make an orbit and hit you in the ass is silly. The bullet will probably either burn up in the atmosphere or head off into deep space. Very few will remain in orbit. The odds are, you're more likely to be hit by another piece of space debris.

All in all, I think recoilless energy weapons like lasers are the way to go.

I heard Bobby Overby descibe firing a shotgun in freefall. I think he came to the concludion that it was a pretty bad idea for the recoil reason.

Most of the things worth doing in the world had been declared impossilbe before they were done.
Louis D Brandeis

Where are we going and why are we in this basket?

[aarco 0]

Secret 38 stashed in the glove box of the Apollo Moon lander- Moon walk stress to great for return - can't find blue killme pill - -Air Force says Good idea - Just in Case -- Other topic - -Skydiver takes math class learning that Delta B - - is nauminal Physics term in Nasa for Rang comparison equation - B meaning Boost -- Delta meaning -- the three mass factors - forward contoled motion - power setting - shape with Mass factor - and - point of throst - - V is power and path - -B is boost past - last V path

Having something never beats doing (>|<)
Iam building things - Iam working on my mind- I am going to change this world - its what I came here 4- - -