I’m more familiar with antiques, and even my “modern” knowledge is ca. 1960 or so, but that corresponds with what I know. Wikipedia lists very few rimfire cartridges that are not .17 or .22, and I believe they are all obsolete, most of them from the mid-19th century, when rimfire and centerfire were seen as rival, rather than complementary, technologies. Both .17 and .22 also have centerfire versions.
If you’re going to talk about “the temperature of the Earth”, you have to average over the entire surface, half of which is lit and half dark at any given time. So the diurnal or seasonal cycles don’t change anything. The changing distance from the Sun would have an effect, but it’s a relatively small one, as is the internal heating from radioactive decay. And the residual heat of formation was lost long ago.
You might be interested in “underwater Kalashnikov”, APS. There is another one underwater rifle, even more interesting (or crazy) because it’s capable of firing either special underwater ammo with long projectiles, or standard 5.45 mm Russian ammo. ASM-DT is really fascinating piece of engineering, with magazine slot that can be adjusted to accommodate different magazines.
Well, some sources I’ve seen say the residual heat from formation is still about 5 to 10% of the heat. So it’s a small, but significant contribution. Hmmm… Here’s a reference from a fairly reliable pop-sci source,
http://www.physorg.com/news62952904.html
But that is beside the point, your original message said,
The point I was trying to get to, but I guess I did not get across well is that due to the diurnal cycle of the Earth, temperatures on Earth really do not get to the equilibrium temperature that an objects in near-Earth space get when either exposed to or shielded from direct sunlight for long periods. Terrestrial temperatures are moderated by the heat capacities of the great masses of the land, air, and water. The temperature of the Earth rises all day until the sun starts to get pretty low which tells you we never reached equilibrium. An object in space that is exposed to the direct sun for a much greater time and does reach reach equilibrium could get a lot hotter. The reverse is true for night. The temperature drops all night. We never get down to the equilibrium temperature that an object near Earth that spent an extended period of time in shadow would get to. (Or an object with less mass and therefore less heat capacity gets to equilibrium more quickly.)
For example, the moon, which rotates with respect to the sun every 28 days and has no atmosphere, has more time for a given point to get into equilibrium with the sky and less ability to transport heat via bulk mass transport. The moon has surface temperature variations between about -230 to 120 C between night and day. So, I personally would not call that range “the vicinity of of the temperatures you find on Earth” given that the cold and hot records on Earth are in the -90 and 57 C neighborhood, respectively.
Finally, we’ve been completely abusing the word equilibrium. What I’ve called equilibrium above is not really equilibrium, but steady state. Yes, the temperature of the test object will not change with time, but it is not at true thermal equilibrium with its surroundings.
Man, I love this board. Where else posters would be self-nitpicking?
I’d just like to note that it was 50 years ago today (Januay 31, 1958) that the U.S. entered the Space Age by launching Explorer 1 into orbit, the first artificial satellite in the history of Mankind, except for the two launched some months earlier by the Commies.
<snickering>
I think Chronos’s point was that the Earth as a whole is in thermal equilibrium with its surroundings. The amount of heat received (and generated, as you pointed out), minus the amount of heat lost by radiation, is close to zero. It’s not exactly zero as the rate of heat received/absorbed is not constant, but it’s pretty close to it and doesn’t underscore the point Chronos was trying to make.
If you take the environment (sun, stars, background radiation, etc) as a given, then wouldn’t it be valid to say the earth is in thermal equilibrium with it?
The temperature of any given part of the Earth rises in the day and drops at night, but the Sun never sets on the Earth as a whole. It’s always lunchtime somewhere on the globe, and likewise always sunset, always midnight, always brillig, and so on.
http://www.aerospaceweb.org/question/atmosphere/q0291.shtml
“even though space is generally very cold, the fact that it is a vacuum means there is no medium to conduct heat away from the body”
The box is not going to ‘radiate’ excess energy, unless it’s actually spewing material of some sort. In fact, my guess is that the box would heat up if it’s relatively near a star.
Which implies that a big problem with guns in space is that you can fire fewer times, as barrel would heat up faster than on Earth causing all kinds of damage.
Your implications are all right - but remember heat radiation, or black body radiation, happens as a result of the temperature of the material.
The last clause in the sentence you quoted is pretty important: “…and it cools rather slowly.”
It doesn’t need a medium for heat exchange, because it’s radiating in the infrared. In a vacuum it’s a slow process. And in sunlight, it would be negligible, compared to the heat input from the sun’s radiation - which includes it’s own black body radiation.
Which, as I say, doesn’t invalidate all your conclusions. Just a small error in your premises.
Oh, I forgot to thank SlowMindThinking for the correction of my own errors.
This post should be called: Would gunpowder burn in outer space. Then I wouldn’t have to read all the crud that is posted about temperature and recoil- who cares.
At outer space temperature extremes the steel and or plastic a conventional firearm is constructed of would not hold up to even one discharged round. So arguments about how a gun works and recoil are completely senseless.
The spring steel in the firing mechanism would not work either. If you did manage to explode a round in the chamber your space suit would be compromised by throusands of small shards of brass, plastic and steel a split second after the entire firearm burst. Unless you are using a special “space gun”.
Maybe someone can figure out how long it will take for the shards of metal to hit the visor of someone who has A7L suit on and stands 6 feet tall.
I agree that’s the only part of the question answered by this article, but that doesn’t mean we should continue to ignore other issues.
As already explained, an object near earth and in sunlight would reach a reasonable temperature (close to the average temperature on earth). It would take longer to cool down after each shot, as heat is only carried away by radiation, but that shouldn’t affect the first shot.
Why not?
And you base your assertion on what? I mean we all know that steel at temperatures close to absolute zero is to brittle, but hey, what’s unreasonable in scenario like that:
You put your space shuttle on orbit along rogue satellite. Put your spacesuit, takes your trusty Colt .45 and heads to airlock. Open it, climb outside, aim at nearby satellite and pull the trigger. Since loss of temperature due to radiation will be very little, all parts of gun would still be close to 20 Celsius or whatever is standard temperature inside space shuttle. Why shouldn’t your pistol fire as usual?
You’re not going to like it here much, then. This sort of grist is just what the mill of this board feeds upon.
As an engineer who works on rockets and space systems, I can assure you that this is not the case. It is true that many steels will become brittle in exposure to cold, but it is hardly the case that they would shatter into “thousands of small shards of brass, plastic, and steel” or that “the entire firearm [would] burst.” If thermal fracture did occur due to temperature (most likely at a weld or geometric stress concentration like a small radius fillet) then it would just brittle fracture as materials here on Earth do, rather than exploding in the fantastic manner described. Most steels used for high quality springs are quite resistant to thermal stress fracture as a result of being carefully alloyed and tempered to survive an “infinite” stress life. (Infinite being longer than the anticipated life of the machine they are a part of.) Of course, springs do break or wear out occasionally, but when was the last time you went in for a routine replacement of your valve springs on your car engine?
One does have to select materials carefully for use in space environments, and the thermal stress cycling between sunlight and shadow could potentially cause premature fatigue, or interferences between aluminum and steel components which will expand at different rates. Long term exposure to space environments would cause volatiles in polymer frames and components to sublimate, and the harsh UV would eventually start to break down polymer chains (though the glass fiber used in most polymer composite gun frames would retain its form indefinitely), but the most likely problems in firing a conventional firearm in space are evaporation of lubricants (already mentioned) and possibly issues with ambient pressure on gas piston-operated arms (though I suspect this would be minimal). The lubricant problem could be addressed by using dry lubricants that are resistant to vacuum adhesion, and in fact, a version of Dri-Slide–advocated by some gun owners for tight tolerance firearms that are prone to contamination faults–is actually used for lubricating mechanisms on satellites and spacecraft.
If you were going to carry a weapon in vacuum for long term (perhaps to protect yourself against buzzing monoliths and psychotic spacecraft computers) then you’d want to design it to withstand the hazards of that environment. If you just want to pop outside your Shuttle for a quick gunfight with a passing megalomaniac or antagonistic cosmonaut, however, the trusty old 1911 will probably serve you quite well. Just rememeber, in space, it is always “high noon”.
Stranger
Answer shallow enough so it doesn’t need to be waded through:
Yes. Anything that’s deflagrating or detonating combusts too fast for it to get its required oxygen from the air, so it must carry its own. Oxygen balance describes the percentage of oxygen available compared to the amount of oxygen necessary for complete combustion, with respect to molecular mass.
Well, I agree in general: any compact thing that detonates is supplying its own oxidizer. And any kind of gunpowder falls into this category.
But you can get real explosions using atmospheric oxygen; you just have to suspend the fuel, either as a gas or in particles or droplets. Examples include a natural gas explosion, grain elevator explosions and fuel-air bombs. They all need just the right balance of fuel and air, but do happen.
Interesting discussion (thanks for mentioning it, “Clicker”).
No, a firearm will not work in space, despite confident commentary. Although it will propel the round (as well as affecting you - Newton’s Third Law), it would be a very tepid end-velocity.
The reason is that your propellant was not formulated to contain it’s own oxidizer (except by chance), given it was intended to be used within our atmosphere (e.g. the source of a readily available oxidizer). Simply, the total amount of actual oxidizing elements contained will be minimal. This is a chemical fact. :smack:
The round will indeed be propelled, but a a low velocity, compared to the same attempted event on the surface of the planet. Flick a pea at someone, and you have a good mental image of the carnage you won’t commit.
If you want to insist that you are actually firing a firearm, given the tiny end-velocity, please do. However, you are talking the difference between firing an arrow from a longbow, and just weakly throwing the arrow at it’s target by hand (a suspect analogy, but go with it for the moment).
So. Formulate a new propellant that contains a significant proportion of it’s own oxidizer, and yes, your firearm will work as desired 
; use our current standard propellants, and you will get a tiny pop. 
No, that is a chemical falsity. Gunpowder and modern smokeless powders have all the oxidizer they need in the form of nitrates (most commonly potassium nitrate) which is mixed in with the propellant. If this were not the case, there is no way that the powders would burn forcefully enough to expell a projectile at several hundred feet per second, nor is the amount of oxygen found in the cartridge sufficient to provide complete combustion.
Stranger
Where does an equivalent amount of oxidizers magically appeared in this chemical process to replace that which is no longer present (absence of atmosphere)?
TANSTAAFL, Bud. 
[ A+15 - 15 does NOT equal A+15 ]