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imachavel
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so in theory in space.......
#14796071 - 07/20/11 02:03 AM (12 years, 9 months ago) |
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if I had a space ship that was 5 miles away from a grenade, and this grenade exploded, in theory, it would travel at the same speed for 5 miles and hit my space ship as though it had exploded right next to it.
without air friction, or gravity, objects in motion tend to stay in motion. this is how the voyager got to pluto with a few rocket corrections right? objects in motion tend to stay in motion makes so much more sense in space
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TheFakeSunRa
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Re: so in theory in space....... [Re: imachavel]
#14796462 - 07/20/11 06:06 AM (12 years, 9 months ago) |
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It seems like you think grenades are projectiles like bullets.
-------------------- [quote]Asante said: You constantly make posts thatr fling middle school insults at people you don't like mixed in with maladjusted psychopathic comments about wanting to beat up the other poster with a crowbar. You know how shit you are, you just don't give a fuck for precisely that reason. I disendorse you.[/quote]
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trendal
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Re: so in theory in space....... [Re: TheFakeSunRa]
#14796492 - 07/20/11 06:18 AM (12 years, 9 months ago) |
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It seems like you think grenades are projectiles like bullets.
Grenades are projectile weapons...the blast doesn't kill you, it's the flying shards of metal that do it. Grenades are designed so that the housing will shred into a lot of metal shards.
To the OP: yes, theoretically the grenade pieces will hit you with the same force as if you were right beside the explosion.
However, this is highly unlikely...at 5 miles out from the blast, the ever-expanding wave of shards will drop off to 1 shard per a few miles of space. It is unlikely that you would be in just the right location to be hit.
That being said...it is theoretically possible.
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Seuss
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Re: so in theory in space....... [Re: trendal]
#14796530 - 07/20/11 06:38 AM (12 years, 9 months ago) |
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Ignoring the grenade, and pretending that it is a bullet instead...
The bullet started at rest and accelerates as it leaves the gun barrel. Assuming there are no other forces acting on the bullet, does it continue to accelerate (going faster and faster), or does it travel at a fixed velocity?
(I know the answer, this is for the OP to think about...)
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imachavel
I loved and lost but I loved-ftw



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Re: so in theory in space....... [Re: Seuss] 3
#14800127 - 07/20/11 08:39 PM (12 years, 9 months ago) |
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I don't know, I don't see why it would accelerate. objects at rest tend to stay at rest, objects in motion tend to stay in motion. What would cause the bullet to accelerate further?
I actually looked this up one time online, because a bullet is a lot different from a grenade as an example. a grenade explodes and the metal shards don't travel much more then a few feet or meters usually. a bullet being fired can travel over a mile if it's powerful enough. so a grenade was a much better example to show how things in space will move forever. now when I looked it up online, the only things that would stop a bullet is the gravity of earth, the gravity of the moon, or the gravity of the sun or another planet. if these conditions are right, a bullet being fired will travel through space at the same velocity for an infinite amount of time. but it will eventually collide with something else or fall into orbit or a planets gravity.
Now I once looked up if a bullet can be fired in space, and obviously there is no oxygen in space. And the answer is yes, because a bullet is gas propelled, the oxygen is between the blasting pin(cartridge) and the projectile(bullet) so the pin hits the cartridge and the bullet will still explode. However, you probably could not fire more then a few shots. there is no air in space, and most guns are air cooled. even though it might appear when firing one, that the chamber stays hot for a very long time, the air moving through the chamber actually keeps the gun from getting past a certain temperature as it is cooled in mili seconds with the air. in space firing a few shots might cause the gun to melt, especially if you have multiple clips.
but take in mind, in space certain temperatures make earth temperature look mild, in the day time in space the temperature can get past water boiling temp (212 Fahrenheit) and at night I guess can get below 200 Fahrenheit. Would a gun really be able to fire at such a low temperature? I guess above boiling wouldn't be TOO bad. Remember, in a desert there are no clouds keeping the temperature in, so in the day it's really hot and at night really cold. now imagine in space! there is NOTHING to hold in temperature, except the object itself, so between sun light and sun set, the temperature might easily drop from boiling to below 200 in minutes if not seconds. I suppose there is nothing to measure temperature change in space if no objects are present, so only the object itself would be able to tell you how fast that would be. So would an object at boiling temperature take longer then minutes to reach negative temperature? I doubt it, air does indeed keep temperatures from changing too fast, even though it doesn't appear that way. it also cools things too though, so what you'd probably see with a piece of metal is a hot piece of metal red hot, that stays red hot as long as it's kinetic energy is still within the metal. as soon as it disappears however, in minutes or seconds it would probably reach negative temperature.
now even though air cools things, it also has density, and temperatures are harder to change in density. so it's possible the gun would take a little longer to cool but once it did would cool at an extreme rate. Did I say that right? It's so hard to figure out the difference. Ok according to this I'm right in that it would take longer for things to cool down without atmosphere. also here are some really contradicting space facts:
http://www.sailwithbluemoon.com/how-long-can-you-survive-in-space-without-a-space-suit.html/
apparently nasa says you can survive 30 seconds in space if you hyperventilate to get as much oxygen in your blood as possible, then release your breath so your lungs don't explode at the loss of pressure. but then someone else says people have put pets in a vicum chamber which creates an instant vacuum and kills the pet immediately. really crazy shit. apparently the oxygen and c02 in your lungs start to expand and create bubbles which explode your veins, and also your blood boils as it's mostly water which boils in space at a temperature of like 45 degrees. I guess water is a phenomenon that occurs only on planets with gravity. all the pressure keeps it from boiling. if you were born in space water would be as rare as dry ice or liquid nitrogen. in space 99.98 percent of water is ice or gas, there isn't enough pressure to turn it into water.
space is a pretty hostile place. I feel bad for that dog on sputnik, fucking communists send a dog into space knowing it will die to run tests on life. fucking gar-bage.
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I did not say to edit my signature soulidarity! Now forever I will never remember what I said about understanding the secrets of the universe by paying attention to subtleties!
I'm never giving you the password again. Jerk
Edited by imachavel (07/20/11 08:58 PM)
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Doc_T
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Re: so in theory in space....... [Re: imachavel]
#14800149 - 07/20/11 08:42 PM (12 years, 9 months ago) |
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Well researched!
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Stonehenge
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Re: so in theory in space....... [Re: Doc_T]
#14812971 - 07/23/11 10:54 AM (12 years, 9 months ago) |
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The question of the bullet fired in space is not as simple as it seems. The textbook answer may be that after firing it continues at the same velocity. I believe that is incorrect and i intend to show why.
First of all, the acceleration does not fall to zero the instant the bullet leaves the muzzle. It does drop off but a column of hot gases erupt after the bullet and keep pushing it for a while. On earth, the atmosphere quickly cancels this acceleration and produces braking or deceleration. In space, we could expect the acceleration to continue for some ways after it leaves the gun. As long as some of the gas is pushing on it, it has a tiny acceleration. After the propellant gases diffuse to the point that no molecules of it are pushing, then velocity will not increase from that push, possibly a mile or two out
There are other forces at play including the solar wind. This is composed of fast moving charged particles from the sun. The wind will take over accelerating the bullet a tiny bit until it has left the solar system and the wind falls to zero. Even then we still have another force which is light pressure. Light exerts a tiny push on anything it hits. So in theory at least, the bullet could continue to accelerate indefinitely.
-------------------- “A democracy cannot exist as a permanent form of government. It can only exist until the voters discover that they can vote themselves largesse from the public treasury. From that moment on, the majority always votes for the candidates promising the most benefits from the public treasury with the result that a democracy always collapses over loose fiscal policy, always followed by a dictatorship.” (attributed to Alexis de Tocqueville political philosopher Circa 1835) Trade list http://www.shroomery.org/forums/showflat.php/Number/18047755
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imachavel
I loved and lost but I loved-ftw



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Re: so in theory in space....... [Re: Stonehenge]
#14825435 - 07/26/11 12:12 AM (12 years, 9 months ago) |
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umm, from what I know in space, only gravity of a planet or another planets orbit will change the speed and velocity of the bullet. nothing else will slow it down, it should go on forever. from what I know a comet is a piece of rock from a planet that exploded years ago, that is still traveling at the same exact speed.
why would any of this other stuff be different? whether the bullet would explode is the question
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I did not say to edit my signature soulidarity! Now forever I will never remember what I said about understanding the secrets of the universe by paying attention to subtleties!
I'm never giving you the password again. Jerk
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DieCommie

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Re: so in theory in space....... [Re: imachavel]
#14825589 - 07/26/11 12:54 AM (12 years, 9 months ago) |
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.
Edited by DieCommie (11/16/16 10:04 AM)
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Seuss
Error: divide byzero



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Re: so in theory in space....... [Re: DieCommie]
#14826259 - 07/26/11 06:25 AM (12 years, 9 months ago) |
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> In physics we sometimes call those 'higher order terms'.
Or as my physics adviser used to say, "Assume that we have a spherical chicken traveling with a velocity of ..." along with "Take any complex physics problem and make assumptions until the problem becomes easy to solve." (The last statement was usually used in the context of theoretical and experimental physics.)
-------------------- Just another spore in the wind.
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Seuss
Error: divide byzero



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Re: so in theory in space....... [Re: Stonehenge]
#14826274 - 07/26/11 06:34 AM (12 years, 9 months ago) |
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> After the propellant gases diffuse to the point that no molecules of it are pushing, then velocity will not increase from that push, possibly a mile or two out
Without the walls of the barrel, the gasses and the bullet are going to quickly reach equilibrium. Remember, the mass of the bullet is many orders of magnitude larger than the the mass of the gas. Acceleration (ignoring gravity, solar wind, etc) will drop to nearly zero almost instantaneously (around 1E-3 second) after the combustion gasses are no longer constrained by the barrel.
-------------------- Just another spore in the wind.
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Stonehenge
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Re: so in theory in space....... [Re: Seuss]
#14827831 - 07/26/11 02:39 PM (12 years, 9 months ago) |
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Diecommie, you are correct. I was deliberately ignoring many factors, chief among them gravity which would also act on the bullet. Gravity could hinder, modify or increase the speed of the bullet. The voyager spacecraft used the slingshot effect of a large planet's gravity, in this case jupiter, to give it added speed so it could escape the solar system without using a lot of fuel. There are also electrostatic fields and static em fields in space which could act on a bullet.
>Without the walls of the barrel, the gasses and the bullet are going to quickly reach equilibrium. Remember, the mass of the bullet is many orders of magnitude larger than the the mass of the gas. Acceleration (ignoring gravity, solar wind, etc) will drop to nearly zero almost instantaneously (around 1E-3 second) after the combustion gasses are no longer constrained by the barrel.
It will drop off quickly but not instantaneously. I estimated a mile or two before it reached zero. Don't forget that the gas has a higher velocity than the bullet, has a forward motion and is produced for an instant after the bullet exits. That explains the flash from a muzzle seen at night and why flash suppressant guards must be used on combat. The propellant keeps burning long enough that we can see it burn after it exits the barrel behind the bullet. What e are you referring to and by -3 do you mean minus 3 or to the -3 power? That would be shown as e^-3. But you know that so we can only guess at your meaning and how you arrived at it. If you mean e as in the mathmatical e, how does that relate to time in this case?
Exactitude will never be had but i wanted to show that it was not a simple situation. The gravity of the gun itself would pull on the bullet so it's a highly complex problem if you want to get it to perfection. Can't be done.
As for the gun overheating, that will not be a problem. In space, materials give off heat and cool rapidly unless they are close to a source of radiant heat.
-------------------- “A democracy cannot exist as a permanent form of government. It can only exist until the voters discover that they can vote themselves largesse from the public treasury. From that moment on, the majority always votes for the candidates promising the most benefits from the public treasury with the result that a democracy always collapses over loose fiscal policy, always followed by a dictatorship.” (attributed to Alexis de Tocqueville political philosopher Circa 1835) Trade list http://www.shroomery.org/forums/showflat.php/Number/18047755
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DieCommie

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Re: so in theory in space....... [Re: Stonehenge]
#14827979 - 07/26/11 03:08 PM (12 years, 9 months ago) |
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10e-3 = 1x10-3, he means a millisecond.
Quote:
In space, materials give off heat and cool rapidly unless they are close to a source of radiant heat.
Well, a vacuum is a great insulator. I dont think it would cool rapidly. There will be no conduction and no convection, only radiation.
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Stonehenge
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Re: so in theory in space....... [Re: DieCommie]
#14828130 - 07/26/11 03:40 PM (12 years, 9 months ago) |
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>Well, a vacuum is a great insulator. I dont think it would cool rapidly. There will be no conduction and no convection, only radiation.
Bingo! radiation it is. Even highly polished objects lose heat rapidly in space. Deep space has the temperature equivalent of nearly zero. That is to say, thermal radiation coming in is equal to that. Roughly.
>10e-3 = 1x10-3, he means a millisecond.
That isn't what he said, he said 1e-3. I'm not that up on math so i don't know all the shorthand terms. I recall from my days in college that e was about 2.7 but if he meant log to the base e it would be something else. So i'm still in the dark. Engineers are used to talking in highly cryptic terms that will throw the layman. They love doing that.
-------------------- “A democracy cannot exist as a permanent form of government. It can only exist until the voters discover that they can vote themselves largesse from the public treasury. From that moment on, the majority always votes for the candidates promising the most benefits from the public treasury with the result that a democracy always collapses over loose fiscal policy, always followed by a dictatorship.” (attributed to Alexis de Tocqueville political philosopher Circa 1835) Trade list http://www.shroomery.org/forums/showflat.php/Number/18047755
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DieCommie

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Re: so in theory in space....... [Re: Stonehenge]
#14828259 - 07/26/11 04:02 PM (12 years, 9 months ago) |
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Right, I wrote that wrong. 1e-3 = 1x10-3. the 'e', often written as 'EE' or 'ee' is the calculator button for ' x 10 ^ '.
As for the temperature... I believe the amount of heat radiating away or on to it is really low compared to the heat that can be lost through convection. The gun would thus stay hot longer in space, unless you fired it near a star to keep it hot.
Edited by DieCommie (07/26/11 04:12 PM)
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Stonehenge
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Re: so in theory in space....... [Re: DieCommie]
#14828390 - 07/26/11 04:27 PM (12 years, 9 months ago) |
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>Right, I wrote that wrong. 1e-3 = 1x10-3. the 'e', often written as 'EE' or 'ee' is the calculator button for ' x 10 ^ '.
Not on my calculator. But a millisecond would not be correct either. The gas rushing out would continue at least a second though it would drop off rapidly. We are talking theory here, not practicality.
>As for the temperature... I believe the amount of heat radiating away or on to it is really low compared to the heat that can be lost through convection. The gun would thus stay hot longer in space, unless you fired it near a star to keep it hot.
The suns radiated heat travels an average of 93 million miles and you can feel it easily. Would you say radiation doesn't work very well? The earth would be cold without it. Objects in space quickly cool to near zero temps unless they are warmed in some way. The space shuttles and crafts had to equalize the heat taken in by the sun and radiated away. The side away from the sun got extremely cold and the other side got very hot unless something was done.
But if it was near enough to the sun, then it would stay hot or heat up even more.
-------------------- “A democracy cannot exist as a permanent form of government. It can only exist until the voters discover that they can vote themselves largesse from the public treasury. From that moment on, the majority always votes for the candidates promising the most benefits from the public treasury with the result that a democracy always collapses over loose fiscal policy, always followed by a dictatorship.” (attributed to Alexis de Tocqueville political philosopher Circa 1835) Trade list http://www.shroomery.org/forums/showflat.php/Number/18047755
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DieCommie

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Re: so in theory in space....... [Re: Stonehenge]
#14828401 - 07/26/11 04:29 PM (12 years, 9 months ago) |
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Quote:
Objects in space quickly cool to near zero temps unless they are warmed in some way.
If by quickly you mean as slow as possible, then yes. Again, vacuum is the best insulator there is.
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Doc_T
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Re: so in theory in space....... [Re: DieCommie]
#14828427 - 07/26/11 04:34 PM (12 years, 9 months ago) |
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Firing a gun several times rapidly would melt it, yes. No way to radiate the heat in a vacuum until it gets glowing hot and starts emitting photons.
Even in atmosphere you can do it, howitzers have strict limits on firing rates for this reason. (One I worked on was "4 rounds per minute for first three minutes, then one round a minute after that.")
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Stonehenge
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Re: so in theory in space....... [Re: Doc_T]
#14828764 - 07/26/11 05:33 PM (12 years, 9 months ago) |
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Doc t, i'm sure you are correct about howitzers. Heat loss in a vacuum would depend on the surface of object. Bright shiny metal would radiate the least, and black will radiate the most.
Objects are radiating photons of energy at all times. When you are next to an object at the same general temperature as yourself, you feel no heat but it is radiating heat. Have you ever been right next to something very cold and felt like it was radiating cold? Cold can not be radiated, only heat, light and so on. When your hand is next to an object of about the same temp, it radiates heat to you at the same rate you radiate it to the object. If the object is very cold, it radiates less heat. You are giving it heat and getting very little in return. It feels like the object radiates cold.
-------------------- “A democracy cannot exist as a permanent form of government. It can only exist until the voters discover that they can vote themselves largesse from the public treasury. From that moment on, the majority always votes for the candidates promising the most benefits from the public treasury with the result that a democracy always collapses over loose fiscal policy, always followed by a dictatorship.” (attributed to Alexis de Tocqueville political philosopher Circa 1835) Trade list http://www.shroomery.org/forums/showflat.php/Number/18047755
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DieCommie

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Re: so in theory in space....... [Re: Stonehenge]
#14828785 - 07/26/11 05:36 PM (12 years, 9 months ago) |
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The amount of heat lost from an object depends on its temperature alone (blackbody radiation). The qualities you describe, the surface and the shine, only affect how incoming radiation will interact with the object.
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