The Workshops

Horus Lupercal

Primarch - Warmaster
Professor
Swingin' on a Star
Deja Vu
Biker Mice from Mars
ET phone home
Floater
Copycat
Registered
Could the gas system of an AR-15 work in the vacuum of space? In this scene, the bolt is travelling much slower so I guess the gas was much weaker and can't push it back as easily like on Earth.
Does the gas come from the combustion of the powder in the bullet cartridge?
Well, these are some most excellent questions for me to ponder. And ones which I've no doubt NASA are actually working on right now with their recent purchase of a couple of rifles for testing.
It wouldn't surprise me if that's one thing they're using X-37 for, is a place to test fire rifles safety in space.

Technically, the gas operation of any gas operated weapon will work perfectly fine in the vacuum of space.

Technically.

However, as you rightly ask, does the propellant create hot gases, or does it heat already existing gas present. My thinking is that it creates hot gases, similar to an SRB. In that case, a 5.56x45 NATO round will work just fine in vacuum.

I can't watch the video, so I'll assume the slow movement isn't a combination of filming effects and the whole 'everything' moves slow on the moon' trope and consider why the bolt would move slower.

In the real world, the gas imparted on the system will move the bolt carrier backwards at speed until it compresses the recoil return spring and buffer plate enough so it gets pushed forwards again to complete the cycle. On the Moon, because the bolt carrier will actually be 1/6th its mass on Earth, will only need 1/6th the force required to cycle the weapon. I think NASA will be using much lower grain propellant for this reason as it doesn't want the bolt basically hammering the weapon apart as it cycles.
Also, the human firing it will be 1/6th his mass. But the recoil impulse fired will still be the same and will effect him 6 times more than usual, another reason to 'dial down' the round.

Sustained burst fire could potentially lift him off his feet entirely.

That won't make a huge problem for accuracy and lethality, as the low gravity and zero atmosphere means bullet drop and muzzle velocity reduction will be almost non-existent and effective range almost infinite.
Theoretically, 5.56mm rounds fired from the surface will become at least sub-orbital, if not mini-death satellites, constantly circling the moon at 900+m/s until their orbit decays or they strike a solid object. And it doesn't need to even cause huge amounts of damage to a man to become effective, like on Earth. All the bullet needs to do is cause sufficient damage to an enemy combatants space suit, compromise its integrity and the occupant is dead regardless. Hell, at those velocities, you'd be able to engage and over-penetrate landers, habitats, craft in low orbit and the like thanks to their extremely thin aluminium construction.
Much lower muzzle velocities are required for space combat, and I think another good, safe reason to 'dial back' the bullet.

I mean, there are a million other problems NASA would need to solve before they use firearms in space. Ammunition cook offs and extreme weapon heating / cooling due to sunlight being big ones.
 

yonkee

Queen of Awesome
Staff member
Team Kolibri
TEAM HAWK
Swingin' on a Star
Atlas
Fly me to the Moon
Registered
MOTY 2022
Could the use of firearms eventually be considered a war crime? If a bullet punctures a space suit the person suffocates, and may have their blood both boil and freeze. It sounds like a cruel and unusual punishment to me
 

Horus Lupercal

Primarch - Warmaster
Professor
Swingin' on a Star
Deja Vu
Biker Mice from Mars
ET phone home
Floater
Copycat
Registered
Could the use of firearms eventually be considered a war crime? If a bullet punctures a space suit the person suffocates, and may have their blood both boil and freeze. It sounds like a cruel and unusual punishment to me
No. It doesn't work like that. The ammunition hasn't been modified to create that additional effect. That's just what happens.
In the same way as it's not a war crime firing tungsten darts into a tank and having the crew smeared by hypersonic shockwaves, the ammunition cook off and incinerate them before the tank explodes.

What is illegal is modifying the ammunition to create a more damaging effect. Like if you engrave a deep cross on a bullets head, rather than it staying in one piece on impact, it splits and really messes someone's day up.
That is illlegal, because you've modified it to do more harm than is necessary. Another reason why deforming ammunition is a touchy subject in the military. We don't use them in the British Army for that reason.

Obviously you'll be thinking 'how is vaporising someone using DU ammunition legal and not 'excessive', but making a split in a 5.56mm round suddenly a war crime?'. There is a difference, but not one I'd expect you to understand.
 

Altaïr

Space Stig, Master of gravity
Staff member
Head Moderator
Team Kolibri
Modder
TEAM HAWK
Atlas
Deja Vu
Under Pressure
Forum Legend
Theoretically, 5.56mm rounds fired from the surface will become at least sub-orbital, if not mini-death satellites, constantly circling the moon at 900+m/s until their orbit decays or they strike a solid object
The orbital velocity of the Moon is rather 1700 m/s. I am not sure a weapon can fire a projectile at such speed, especially a light weapon that can be handled by hand...
 

Horus Lupercal

Primarch - Warmaster
Professor
Swingin' on a Star
Deja Vu
Biker Mice from Mars
ET phone home
Floater
Copycat
Registered
The orbital velocity of the Moon is rather 1700 m/s. I am not sure a weapon can fire a projectile at such speed, especially a light weapon that can be handled by hand...
Ah yes. So no, it won't be orbital. But at 970m/s, a 5.56mm round isn't going to come back down any time soon and should happily go sub-orbital to decent altitudes.

Tank main guns can create that kinda velocity though. APFSDS darts can get to around 1800m/s
 

Chara-cter

37°14′0″N 115°48′30″W
Man on the Moon
Registered
Could the use of firearms eventually be considered a war crime? If a bullet punctures a space suit the person suffocates, and may have their blood both boil and freeze. It sounds like a cruel and unusual punishment to me
It won't be a war crime but someone might argue that you violated the Outer Space Treaty, which sucks
The orbital velocity of the Moon is rather 1700 m/s. I am not sure a weapon can fire a projectile at such speed, especially a light weapon that can be handled by hand...
Saw someone made a .17 round in a .50 BMG case that could travel at Mach 5.5, just enough to be in orbit :p
 
Saw someone made a .17 round in a .50 BMG case that could travel at Mach 5.5, just enough to be in orbit :p
We had this caliber, the 7.92×94 Patr.318, which is close enough. It was used by the SS-41 anti-tank rifle, one major issue with this type of caliber was that it wore the hell out of the barrel, so the gun was designed like a machine gun, with spare barrels and all. Its design was just as intended, to achieve a muzzle velocity great enough to defeat enemy armor.

Im not sure why exactly, but it might be something to do with the immense chamber pressure acting upon a smaller surface of a smaller caliber, which in turn magnifies the pressure acting upon the rifling of the barrel, accelerating its wear.

Nowadays, modern and effective anti-tank rounds have big calibers accompanying their big cases, like the 30×173 mm.

1617548634214.png
 
Im not sure why exactly, but it might be something to do with the immense chamber pressure acting upon a smaller surface of a smaller caliber, which in turn magnifies the pressure acting upon the rifling of the barrel, accelerating its wear.
Hell, just for this reason, a lot of big guns nowadays are moving towards smoothbore, because from a manufacturing standpoint, smoothbore barrels are considerably cheaper and easier to fabricate. They also theoretically wear out slower than rifled barrels, might even be a lot easier to clean too.

Though this is for tank guns only, to my knowledge, not sure about naval guns.
 
Speaking of rifling, I've finally learned a new way to make rifling with the help of a instruction video made by the CATI guys. Ashamed to say that I've never heard of ECM until today, good to know.

 

Horus Lupercal

Primarch - Warmaster
Professor
Swingin' on a Star
Deja Vu
Biker Mice from Mars
ET phone home
Floater
Copycat
Registered
It's mostly because tank guns use APFSDS rounds and not only do they not need the spin to stay stable, but the spin actually makes them less effective.

They have been moving towards smoothbore for a while now, with only british made tank guns (like the Royal Ordnance 120mm on Challenger 1+2) still being rifled. Everyone else uses a smoothbore gun, and it looks like we will be too if the propositions I've seen for Challenger III go ahead, using a smoothbore 130mm gun from Rheinmetall.

Naval guns, despite being bigger, still need rifling though.
 

Horus Lupercal

Primarch - Warmaster
Professor
Swingin' on a Star
Deja Vu
Biker Mice from Mars
ET phone home
Floater
Copycat
Registered
But is it completely true that smoothbores are much easier (maybe cheaper) to manufacture than rifled ones? I know logistically it could be a pain in the ass, as you have to convert the entire ammunition stock to be smoothbore compliant. In the short run at least.
Yeah, they will be.

Actually, it makes ammunition easier to come by, cos everyone is using the same type of ammunition. Similar to how everyone went to a standard NATO 7.62 rather than the numerous iterations of .30calibre ammunition around like .303, 30-06 etc.
A German Leopard II can fire American Abrams ammuniton. Whereas a British Challenge II, despite also being a 120mm gun, can only fire British 120mm ammuniton.



I noticed that modern warships no longer uses those massive triple cannons, all I see nowadays are "small" gun turrets, CIWS and missiles
Yeah, it's all about sending missiles and shooting down missiles these days.:(
Yep. As impressive as an old school broadside is from a battleship, in terms of absolute accuracy and lethality, a single, modern guided missile destroyer could happily take on every single battleship ever built simultaneously and, find, track and sink them all without problems. You'd just need to keep supplying it with missiles.
The only real exception (ironically enough) would be the Iowa class after they were re-fitted with cruise missiles, modern radar and CIWS weapons.
Then that destroyer better get fucking running, cos Mighty Mo doesn't hang about and certainly doesn't fuck about.
Same with aircraft carriers. A single Nimitz class could take on every ship ever to sail in the Royal Navy (up to and possibly including the Invincible class carriers) and wipe the floor with the lot of them.

As a side note, those 'small' guns tend to be 5-6inch guns, around 150+mm in calibre. That's heavy artillery realms in terms of land based weaponry.
 

Blazer Ayanami

Space Shuttle enthusiast // Retired Admin
Registered
Forum Legend
So here’s a question that I hope is in the right thread cause this thread is about engineering and my question is about an engine.

As you all know Jet Engines work by compressing the air and burning it, basically. However this requires an atmosphere of oxygen. So I’m wondering, for a planet who’s atmosphere is not made of oxygen, but it is basically made of a flammable or combustible element, is it possible to make an engine that “breaths” this gas, in the same way Earth Jets breath oxygen?
 

Mooncrasher

Reading LOTR lore
Staff member
Team Valiant
Discord Staff
Voyager Quest
Man on the Moon
Forum Legend
Well, remember that there's two different parts to a rocket engine.
Let's take Falcon 9: Oxygen and a special kind of Kerosene. Kerosene is the fuel that burns, oxygen (the oxidiser) simply allows the burning to take place.

Jet engines are the same way. You compress the air so there's lots of oxygen, inject some kerosene, ignite the kerosene, and the kerosene burns very strongly because of the oxygen.

If you take that jet engine to somewhere with a flammable atmosphere that has no oxygen:
Suck in the atmosphere, compress it, inject kerosene, ignite it, and.... nothing happens?
That's because you're missing an oxidiser! Fuel can't burn without an oxidiser, unless it's hypergolic.

That does raise questions about jet engines that inject oxygen instead of kerosene... Maybe that could work. But one oxygen leak and you might blow up the whole plane in this flammable atmosphere.
 
As you all know Jet Engines work by compressing the air and burning it, basically. However this requires an atmosphere of oxygen. So I’m wondering, for a planet who’s atmosphere is not made of oxygen, but it is basically made of a flammable or combustible element, is it possible to make an engine that “breaths” this gas, in the same way Earth Jets breath oxygen?
Mission Le Verrier actually rode on this concept with its Neptune hypersonic unmanned aircraft, where the engine was modified to inject oxidiser into the combustion chamber instead of fuel.

Unfortunately that thread was deleted.
 
But one oxygen leak and you might blow up the whole plane in this flammable atmosphere.
Doesn't have to be liquid oxygen, the contents would've boiled off by the time you reach such a planet, like Neptune. An alternative would be a liquid-at-room-temperature type of oxidiser, like Nitric Acid.

About an explosion from a leak, I'm not sure about that. Maybe it depends on the concentration of oxidiser or fuel in the local atmosphere. I mean, is Titan or Neptune fully saturated with Methane or Hydrogen?

Aircrafts on Earth never had any explosions from fuel leaks, not that I've heard of at least.