Mass driver. And a backup one in a secret location in case the loonies stage a revolution.
Well done for spotting the reference.
Not quite. IIRC the narrator speculated that with a bit more pull, one of the arrows might be launched into orbit. But it was only a speculative statement, and didn’t happen in the story.
A History Channel program on space weapons said that temperature extremes and vacuum are going to be huge problems for conventional firearms. Direct sunlight will heat the weapons up rapidly, and they won’t radiate heat away very well; shadow will plunge them into deep cold. Moving between sunlight and shadow will expose them to hundreds of degrees in temperature change which will likely making moving parts inoperable. And, as mentioned above, they won’t shed heat while firing.
Speaking of moving parts, vacuum will tend to boil away lubricants, leaving everything dry and unlubed.
It’s enough to make one wonder if the first moon war will be fought with swords. 
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Oh no … don’t encourage the fanboys …
Spacesuits and moonbuggies can be made to work under these conditions. I think the history channel was up to its old tricks of trying to make everything sound Xtreme in order to draw viewers.
Unless your lunanauts are going full auto, heat will have time to conduct itself away into the bulk of the weapon between shots, just as it does on earth.
Plus your lunar weapon could be designed to have 6 times the mass of an earth weapon yet maintain the same portability. Not only could that extra mass serve as a heat sink, it’d improve recoil damping and allow for steadier aiming.
Almaz stations. Crazy bastards, those Russians.
Lasers.
Okay, maybe not in the 1970s, but certainly today, no?
Unlike on Earth, you don’t have an atmosphere to interfere with beams, so you should be able to deliver more power to the target (and more accurately). Weight of a weapon is less of an issue for obvious reasons. Finally, you only have to do enough damage to tear open a spacesuit.
I don’t think recoil would be a problem. The low gravity would be acting perpendicular to the force of the recoil, and thus have no effect. This is the reason a bullet takes the same time to hit the ground on earth, weather fired from a gun or dropped from the same height.
Right, but low gravity also means that there’s less friction between the astronaut and the ground, and they’ll also be a bit easier to tip over. My guess is that the astronaut-soldier will have to be a bit more careful when picking a firing position with high power firearms – not a huge deal, but another example where things are more awkward on the moon.
Sort of what I was thinking, yeah. Even then, reloading’s going to be complicated with those stiff, bulky gloves.
Better make it a crossbow pistol, too, because you wouldn’t be able to hold a full-size crossbow in a normal aiming position. Same would apply to rifles and shotguns.
[tiny hijack:/ how does a bullet accelerate? Part of it shears away in flight? /tiny hijack/.]
The fine regolith of the Moon’s surface is actually a huge problem, not just for firearms but for any device with articulating, translating, or rotating components. In the near-vacuum of the Moon’s surface, it forms a fine layer that is several feet thick in places, and is freely disturbed in Luna’s low surface gravity, but once it comes into contact with any liquid or even slightly charged surface it accumulates with a vengeance and forms a thick layer of cement (search on “vacuum cementing”). As the Apollo lunar missions demonstrated, the dust gets into everything, sticks to it due to electrostatic attraction, and gums things up to no end; see NASA/TM—2005-213610/REV1 The Effects of Lunar Dust on EVA Systems During the Apollo Missions, James Gaier, April 2007. While it seems like a minor issue at first, it turns out to be a major problem in using any mechanisms or moving machinery for any extended period of time, and may well be a health risk as well. I can imagine this being a major issue for any kind of ammunition feed mechanism; you’d definitely want the magazine to be sealed against the environment. If using a gas piston or gas-retarded delayed blowback action you’d also need to protect the port(s) against dust intrusion. A purely recoil operated mechanism like inertial blowback, recoil-operated cam, or roller locking mechanism (as is used in most handguns) would be desirable.
Lubrication would have to be a dry lubricant or self-lubricating surfaces. Fortunately, this is not a major problem; there are both dry powder lubricants that have been developed specifically for satellite and long-term space probe mechanism which are readily suitable, and low friction hard finishes that, combined with open clearances between sliding parts, should prevent tribological issues (provided that you aren’t plagued by vacuum cementing).
The thermal and material issues, while not insignificant, are not as large an issue as they may seem. The amount of heat convected away from a gun barrel by air convection is pretty small compared to the heat transfer to the environment sink via radiation (hence, why heavy machineguns and chain guns employ a water cooling system). The thermal cycling–going from extreme hot in direct sunlight to extreme cold in darkness–would demand using materials that are resistant to thermal cycle fatigue and have high general toughness. You’d also have to pay significant attention to differences in thermal expansion rates of materials, and build in tolerances that would account for such differences to prevent binding or high thermally-induced stresses. Glass-fiber polymer composites (like those used in the frame of the Glock and other composite frame firearms) would be desirable; however they would require a protective coating against the unfiltered UV radiation which causes the polymers to break down.
Recoil is something of an issue, and would probably drive you to using a lighter mass, high penetration projectile like the flechette rounds suggested by Patch. A larger problem is physically handling and accurately aiming a firearm. Just from watching videos of the astronauts on the Moon in the Apollo-era A7L suits shows just how difficult it is to perform even basic tasks like deploying mechanism arms or collecting rock samples. Holding an oversized pistol out in front, single-handed would be plausible, but bringing a two-handed rifle to bear would be next to impossible. Being able to obtain a bead (align the head with the sights) would also be very difficult except in standing or kneeling position. Firing around cover or firing from a prone position would be out of the question. It would probably be easier to mount the gun to a hardpoint on the suit torso and aim via some kind of control mechanism or by physically orienting the suit; in either case, accuracy is likely to be poor.
The suggestions to use a GyroJet-type pistol with a self-propelled cartridge, or a crossbow of some type are probably the most practical, both in terms of minimizing recoil and avoiding the binding issues with thermal expansion and lubrication. These would minimize moving parts, although the obvious problems with handling and aiming the weapon in a vacuum suit remain.
A man-portable penetrating laser weapon is right out, for the same reasons that it isn’t suitable for use on Earth. It’s not that a compact, high energy laser itself is implausible, but the power source for such a weapon would be way too large to be practicable for an astronaut to carry, and could be readily defeated by an ablative coating that would absorb and radiate away the energy delivered by the laser. Lasers are hugely inefficient in terms of energy usage, and a high energy laser would produce a lot of waste heat that would have to be removed via an exhaust coolant or some other means. The lack of an atmosphere is not a significant advantage at the ranges that surface combat would occur; the thermal blooming issues that plague high energy lasers intended for ABM applications occur because of the enormous mass of atmosphere that must be penetrated and the levels of energy that are absorbed.
However, this is all academic. The idea of astronauts taking potshots at one another is fanciful at best. Just keeping astronauts alive and marginally functional in a vacuum environment is enough of a challenge without throwing in open warfare. If it was desired to take out enemy combatants on the Moon’s surface, it would be far easier to simply shower their spacecraft and base with projectiles delivered from orbital or suborbital vehicle. Individual combat in a vacuum environment in anything like existing hard- or semihard-shell pressure suits would be way too difficult, risky, and fatiguing to be practical.
Stranger
Maybe, but firearms have some different requirements. They need gas-tight sliding parts (they can’t use gaps in the systems that depend on gas pressure) and the same parts have to resist shock – you can’t use a pliable soft rubber seal like you could on a spacesuit.
Not true, though I had to draw a diagram to convince myself of it.
Ideally, when you’re about to fire a gun while standing, one foot is forward and one foot is back, with your center of mass between them. Gravity is pulling your center of mass straight down, so you’re supported by both feet. As the gun fires, your center of mass is pushed backwards, so the center of mass is now being pushed backwards (by the gun) and downwards (by gravity). If you’re braced correctly, the two forces add up to a single force pointing backwards and down, but inside of your back leg. This puts more force on your back leg and less on your front, but everything still balances and you stay standing. If your back leg is too far forward, the sum of the two forces ends up pointing outside of your back leg. Now things don’t balance and you tip over.
OK, so think about what happens if gravity gets reduced: now, for the same push from the gun, the sum of gravity and recoil points farther backwards (the sum force is smaller overall, because gravity is smaller, but it points more backwards, since recoil is relatively larger). Result is that a stance that’s well-braced on Earth might not be on the Moon.
As a separate issue, you’re also more likely to skid on the Moon, since there’s less gravity forcing your foot to the ground, so less friction. But I suspect that even on the Moon, there’s plenty of friction for resisting recoil of any reasonably sized personal weapon.
If I remember the Clarke story correctly, the U.S. and Soviet moonbases got into a “defense race” of sorts, with each trying to build a bigger and thicker wall to absorb the impact of the previously-fired low-orbiting slugs.
If there was a military necessity, I’m sure the bright lads and lasses at DARPA could come up with some kind of airtight, internally-lubricated rifle that could withstand the temperature extremes of the lunar surface. It wouldn’t surprise me if there are plans for that sort of thing already.
As for bows and arrows… in The Forever War, Joe Haldeman posited that an energy-absorption field could make all beam weapons inoperable, so Earth’s gallant warriors of the distant future have to train with bows, arrows, spears and swords. The more things change…
If we’re assuming Apollo-era spacesuits, you can add in that an astronaut probably couldn’t get his feet far enough apart to be well-braced even for Earth, plus a top-heavy design to the suit, with the helmet and life-support system.
Hu? No, a bullet has reached its maximum speed the moment it exists the barrel of the firearm. From then on, it only slows down.
Bullets accelerate by chemical combustion.
Yeah, but it’d make for one hell of a spy-novel.
Bonding, John Bonding* in Lunar Fighting, while on his third day of his lunar expedition to investigate the cause of a series of strange ‘accidents’ at Luna-One, John Bonding discovers a mysterious agent working for a foreign government… but will he survive to tell anyone? In this hand to hand space fight, tactics rule!
*Not a copyrighted/trademarked name
So you can have also use those big ass swords that you see in manga and anime? I’'ll use that in my comic.
;)
Okay, power remains a problem. But how about a particle beam instead?
I agree. It would be ridiculously easy to kill an astronaut on the surface. If you HAD to have people on the moon in a war, your only hope would be to keep them in a bunker deep underground. Do your fighting from space or with robot drones on the surface.