NASA to buy lightweight, semi-automatic rifles

[Sauer Grapes]

Maybe first they should think about what the guns could be used to shoot at? Jack.

Maybe armed in case of an emergency landing back on Earth? Possible landing in an unfriendly territory.....

 

[AHM]

Yes, 5.56 rounds aren't nearly fast enough to orbit the moon.

They're fast enough if you fire them out the side door of the Space Shuttle.

They need to post those signs wherever NASA bureaucrats gather.

An upperclassman told us that when he was younger,
he once rode a crowded elevator in the school's administration building.

The car stopped at the deans' floor and everyone else
but an upperclassman got off.

After the door closed, the upperclassman said,
"if a mongoose got loose in there,
there'd be nothing left alive".

 

[meh]

They're fast enough if you fire them out the side door of the Space Shuttle.

If you add height and/or speed at some point it will get all the way around. I thought about deriving the differential equation and solving it. It sounded fun, but then I remembered nobody was going to pay me for it, so...

 

[HorizontalHunter]

The vacuum of space shouldn't make any difference in modern ammo. Rounds have oxidizers in them. Can fire in a vacuum, under water, etc. What would be interesting though is the low G's of space and the moon. I wonder if there is an angle you could shoot while standing on the moon where it would be possible to shoot around the entire moon and hit yourself with it (ie. not enough angle to escape gravitational pull, but high enough to account for minimal bullet drop and little atmosphere to reduce velocity).

I think they should send up an AR and some ammo in the next replenishment launch . I think a space walk with an AR and a couple of mags is in order.

Bob

 

[meh]

If you add height and/or speed at some point it will get all the way around. I thought about deriving the differential equation and solving it. It sounded fun, but then I remembered nobody was going to pay me for it, so...

Actually, I did end up playing with this a bit. It's interesting. You can make it all the way around if you add enough height, but if you don't have orbital velocity, the bullet winds up, of course, at a lower altitude when it gets all the way around. What I found more interesting was exploring the effect of shooting at an angle. Yes, you can add distance by firing upwards at an angle, but here's the catch. If you don't have orbital velocity horizontally, you're not going to make it all the way around no matter what angle you choose, and the greater the angle, the more you rob the bullet of horizontal velocity to give it altitude instead. Even if you have sufficient velocity, but not escape velocity, the ballistic trajectory when firing upwards at an angle is an ellipse that intersects the moon on the other side. I probably should have intuited that because without air resistance, the force of gravity acts symmetrically on the bullet once it reaches the halfway point. It wants to come into the surface at the same angle it left.

Anyway, at a mere 3200 fps, for example, firing from the surface with the muzzle 6 feet off the ground, you can increase your range to almost 442 miles, best angle I found, but that only gets it 6.5% of the way around before it hits the surface. You need about 5521 fps firing horizontally to get all the way around. Then it takes over 109 minutes to get back to you.

 

[HorizontalHunter]

 

[AHM]

You need about 5521 fps firing horizontally to get all the way around. Then it takes over 109 minutes to get back to you.

Not counting the mezzanine.

 

[Dench]

Actually, you're forgetting Newtonian physics here. Every action has an equal and opposite reaction.

They want them for emergency propulsion!

There was a person here a while ago who was under the impression the felt recoil was the same force as the impact of the round at normal non insane distances.

 

[AHM]

There was a person here a while ago who was under the impression the felt recoil was the same force as the impact of the round at normal non insane distances.

Spoiler: Sometimes F=ma

 

[Dench]

HK21's for the other stuff. At least in the past, I have no idea now.

 

[meh]

Not counting the mezzanine.

I'm also idealizing the moon as a perfect sphere, which it ain't. More than the minimum velocity will be needed to obtain a clear path when firing near the surface, but with more speed, it takes longer to complete the orbit.

 

[Spanz]

Maybe armed in case of an emergency landing back on Earth? Possible landing in an unfriendly territory.....

come on....its aliens
shoots them

 

[Yazz]

They could get them for free from Australia!

 

[M1911]

They could get them for free from Australia!

I think you mean New Zealand.

 

[AHM]

HK21's for the other stuff. At least in the past, I have no idea now.

I always thought it meant you were supposed to shoot out of the door,
not towards it.

I'm also idealizing the moon as a perfect sphere, which it ain't. More than the minimum velocity will be needed to obtain a clear path when firing near the surface, but with more speed, it takes longer to complete the orbit.

Masscons? Masscons? Don't talk to me about Masscons!

 

[meh]

Masscons? Masscons? Don't talk to me about Masscons!

LOL. Not to worry, I was only thinking about the bullet hitting a lunar mountain or something. Besides, masscons are a good thing. It would be a dick move to put a collection of fast moving pieces of lead in stable low orbit of the moon.

 

[AHM]

It would be a dick move to put a collection of fast moving pieces of lead in stable low orbit of the moon.

No need to travel a quarter million miles to experience a dick move.

 

[rkwjunior]

Does DI work in vacuum? I'd imagine piston may cycle.

I dont think the round would ignite at all. You need oxygen to burn, there is no oxygen in a vacuum.

 

[fshalor]

I dont think the round would ignite at all. You need oxygen to burn, there is no oxygen in a vacuum.

How sealed are crimped cases? Short walk may have enough chooch for primer and charge.

 

[AHM]

I dont think the round would ignite at all. You need oxygen to burn, there is no oxygen in a vacuum.

How sealed are crimped cases? Short walk may have enough chooch for primer and charge.

Let me Google that for you.

 

[AHM]

Let me Google that for you.

Modern ammunition contains its own oxidizer ...​

(In markèd contrast to ancient ammunition,
which contains its own oxidizer).

 

[fshalor]

Modern ammunition contains its own oxidizer ...​

(In markèd contrast to ancient ammunition,
which contains its own oxidizer).

That jives with my initial understanding. Primary is sealed and compete so would fire. Main charge should fire, though would be slightly adversely impacted due to cold exposure and vacuum plus moisture sap. Overall reaction would be seriously attenuated. Gases from that reaction will most likely cycle the bolt out of battery, but would there be enough gas produced to actuate the DI system and cycle the bolt completely?

My bet is a normally buffered AR15 rifle length barrel and gas tube system would fire but short cycle in space and require manual charging handle ops.

No need for a followon shot anyway as you would be moving backwards at around... 8-80 FPS.

 

[AHM]

That jives with my initial understanding. Primary is sealed and compete so would fire. Main charge should fire, though would be slightly adversely impacted due to cold exposure and vacuum plus moisture sap. Overall reaction would be seriously attenuated. Gases from that reaction will most likely cycle the bolt out of battery, but would there be enough gas produced to actuate the DI system and cycle the bolt completely?

My bet is a normally buffered AR15 rifle length barrel and gas tube system would fire but short cycle in space and require manual charging handle ops.

No need for a followon shot anyway as you would be moving backwards at around... 8-80 FPS.

Operating in a vacuum, there's a greater pressure differential and thus more yield:

Net thrust​

Spoiler: Here's what that 'oxidizer' ingredient looks like