Would it be possible for an astronaut to shoot a “sniper rifle” (the one usually used to kill targets on a long distance) on the moon? I mean, the weapon would probably work pretty well if there aren’t any parts that need air pressure or gravity to work. But what about the bullet?
If the astronaut had a very potent scope - something that hypothetically could see a target on our planet - would he be able to actually shoot and hit this target?
Inspired by this comic.
In short, the weapon should function just fine. Bullets don’t need air to work, because all the oxygen for combustion is carried in the powder. You’d probably even gain some muzzle velocity because of the lack of air pressure (and air mass) on the front of the bullet as it travels down the barrel. I’ll assume the extra 1 atm of delta-P wouldn’t cause any part of the gun to blow up.
However, you couldn’t shoot a target on the Earth. Your muzzle velocity will be nowhere near the escape velocity of the moon (2.4 km/s). And any bullet that did go fast enough to escape, on the right trajectory to intersect the earth, would undoubtedly burn up in the earth’s atmosphere. It would just be a meteor.
Except of lubrication issues, there’s no problem firing a rifle on the moon. The escape velocity on the Moon is 2.38 km/sec, which is 7808 feet/sec - faster than any rifle I know (it’s almost twice as fast as the .220 Swift, at 4,000 ft/sec).
Even if you could fire a projectile and have it escape the Moon’s gravity, the targeting would be too complicated for a human to do - it would take a LONG time for the bullet to reach the Earth, and in that time the Earth would have rotated many degrees.
Also, I dont think you aim at the earth if you want to hit the earth.
As others have said, the mechanism of the sniper rifle, whether autoloading or bolt action, should work. You would want to use a fine dry lubricant like molybdenum disulfide (Dri-Slide, SmoothKote) so the volatile compounds don’t boil off. However, the environmental problems of operating on the Moon are fairly formidable. The first and worst is dust; the fine, electrostatically-charged dust on the Moon sticks to and infiltrates everything, and is nearly impossible to remove. Even during the short duration of the lunar missions it caused substantial difficulty (see NASA/TM—2005-213610/REV1 “The Effects of Lunar Dust on EVA Systems During the Apollo Missions”, James Gaier, April 2007) and there is no clear engineering solution to dust intrusion, which would be enormously problematic for a close tolerance device like a piston-operated automatic rifle or a rotating bolt.
Another are the extreme thermal conditions on the Moon; about 250 °F in sunlight to to -385 °F in darkness, and there isn’t a lot of middle ground. Firearms are designed for operation at normal Earth surface temperatures and can sometimes have problems even then. The coefficient of thermal expansion (CTE) problems of taking a firearm designed for terrestrial use may well have binding problems with the high CTE. Compounding that is the fact that while on Earth most man-portable weapons are cooled by convection to the surrounding air, a rifle on the Moon would only be able to (slowly) radiate away the heat generated by the firing of a round. So, you can expect to have problems after a few shots on a close tolerance firearm like a sniper rifle.
The other thing to consider is that if your rifle is sighted in for terrestrial use it will shoot way high, both because of the significantly lower gravity and the lack of air resistance reducing the anticipated drag on the bullet. If the bullet is precisely designed for significant aerodynamic stabilization it may also be less stable in the vacuum conditions of the Moon, but this is most applicable to lightweight rounds; the heavier bullets typically used in sniper rifles are probably not as prone to this by design.
So the essential answer is that you could fire a sniper rifle on the Moon at least a few times as long as it was protected from dust and thermal extremes, but you couldn’t carry it around openly for any duration of time and expect reliable operation. Realistically, if you wanted to use a rifle on the Moon (or Mars, or another solid planet) you’d probably want to design it for that specific application, e.g. the temperature and atmosphere conditions, as well better protection from dust intrusion, a specific bullet and cartridge loading for that atmosphere and gravity, and provide some system for internal cooling, e.g. a liquid heat exchanger loop in critical areas like the chamber, piston, and along the barrel which would go to some kind of radiator or coolant tank.
You could not fire a rifle from the Moon at Earth unless the cartridge had sufficient muzzle velocity (~2400 m/s). This is about 2.0 to 2.5 times the velocity of the most powerful sniper rifles in existence, and probably more than you could hope to achieve from a single cartridge gas-fired gun. Even if you could fire a round at that speed, you wouldn’t aim directly at the Earth because it would have rotated well out of the way by the time your bullet reached that distance; you’d need to fire ahead of it and compensate for the affects of Lunar and Earth gravity on the bullet during its trajectory. This is a surprisingly difficult problem for a purely ballistic object; the Apollo missions typically performed a number of planned mid-course corrections and occasionally unplanned or modified corrections. A slight deviation early in the trajectory of the bullet from the planned course may have it miss the Earth completely.
Stranger
Yeah, just ask the door gunner Gxrypth of Zork Force: you gotta lead it.
OK, time for Plan B. If you had a long enough knife, could you stab someone from the moon?
“Never bring a knife to a space fight.”
Stranger
I just have to say - I LOVE THIS FORUM. I asked a hypothetical question based on a web comic. And people are getting into details such as the chemical composition of lubricants. I should post here more often again.
And a knife would be very good on a astronaut-astronaut fight - cutting a suit open sure would cause some problems for the knifed fighter.
Even if you, say, fired the gun from your return vehicle once it has achieve escape velocity and were headed back to the Earth (and if you had the precise vector needed to at least have the bullet hit the Earth) I think the bullet would burn up in the Earth’s atmosphere, so wouldn’t hit the target, regardless.
Just throw rocks.
If you fast forward to the 45 minute mark in this Youtube video you can hear about how the Soviets actually fired a canon in space.
Joking aside, there’s nothing much to ‘lead’ - the Moon is tidally locked to the Earth, so the Earth does not appear to move much at all from the POV of someone standing on the moon.
But I think you have to fire backwards in terms of the Moon’s orbit around the Earth - thus cancelling orbital velocity and allowing your bullet to fall into Earth’s gravity well.
It’s quite interesting. Does anyone know of any serious research on hypothetical space combat tactics using today’s technology? This comes up all the time in science fiction with a lot of handwaving in favor of the story’s preferred plot devices, but it would be interesting to consider how we could leverage what we have and know. For example, if you were a General in charge of preparing for a hypothetical US-Russia showdown on the Moon and had a NASA-large budget, what would you send?
One thought that I had was to field large numbers of cheap, “throwaway” weapons that would be expected to become unusable quickly (due to the moondust). E.g. instead of sending a few expensive top-of-the-line rifles and a ton of ammo crates, send a ton of crates full of old weapons with loose tolerances, each with one or two magazines each. As soon as your weapon jams from the moondust, throw it away and open the seal on another zip gun.
That’s pretty harsh.
And try not to kill your artificial intelligence system. He’s smarter than you…in some ways. But he is probably your best friend.
Robert Heinlein’s The Moon is a Harsh Mistress (1966) - a classic space politics novel with some combat.
The William Tell Overture?
What about re-entry, is there ceramic rounds that could survive? I assume metallic would burn up.
Could someone explain in more detail please. The bullet wouldn’t be going faster than it does on earth, would it? Or is it a matter of the amount of time it spends going that fast?
In Heinlein’s The Moon Is A Harsh Mistress it took a futuristic quasi-maybe-sentient supercomputer to work out the trajectories to do that.
