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Post by Cybermortis on Aug 29, 2013 13:13:41 GMT
It is a long standing TV and film Trope to include sound in space, from the sound of weapons firing to ships flying past and of course the spectacular explosions.
Conventional wisdom and science tells us that none of this should of course happen - space is a vacuum* so there is nothing for sound waves to propagate through.
(*Space is not a complete vacuum, as there are hydrogen atoms floating around. But for all intents and purposes it might as well be a total vacuum)
However, when J.M Straczynski was developing the TV series Babylon 5 he talked to several people from NASA for technical advice. During these talks the issue of sound in space come up, and the answer was interesting.
According to those people from NASA it is technically possible to hear an explosion in space. The logic (and science) is that an explosion would create an expanding globe of gas that would carry sound waves from the explosion - especially if the explosion took place in a spacecraft that possessed an atmosphere.
As far as I can tell no one has ever tried to see if this theory hold true.
My thinking is that MB could see if you could hear an explosion in space, or at least in a vacuum. A small fire cracker detonated in a vacuum chamber with a number of microphones would allow them to do this, and moving the microphones would give an idea as to how close you would have to be.
The tests could also be carried out by placing the cracker inside a small plastic bag filled with air, allowing them to see if that increases the distance at which anything can be heard (or if it increases the chances of anything being heard).
This testing would also allow them to cover several other related myths;
'Will a gun fire in space?' - This was often posted on Disco. Physically there is no reason that a gun will not physically work in space. So the question is if gunpowder would ignite (which it will as it contains its own oxidizer). Setting off a firecracker would prove this, as would putting say a starter gun or conventional pistol loaded with a blank round inside the chamber and firing it.
'The colour of an explosion in space will depend on the internal atmosphere' - This is another B5 'myth' that came from NASA. The idea is that different atmospheres (such as methane) would/will create a different coloured explosion. This would be easy to test by filling the bag containing the fire cracker with different types of gas. According to JMS they carefully researched this for B5 to make sure that the colours of ship explosions were consistent with what the atmosphere was meant to be for that ship.
Thoughts?
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Post by GTCGreg on Aug 29, 2013 14:38:41 GMT
If you were to detonate a fire cracker in a vacuum with microphones also withing a reasonable distance from the detonation, I have no doubt that the microphones would register the "explosion." In fact, depending on distance, the particle wave front from the explosion would most likely damage the microphones. The fact that you have a bunch of particles in your "vacuum" would simply mean you no longer have a vacuum.
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Post by the light works on Aug 29, 2013 14:39:00 GMT
It is a long standing TV and film Trope to include sound in space, from the sound of weapons firing to ships flying past and of course the spectacular explosions. Conventional wisdom and science tells us that none of this should of course happen - space is a vacuum* so there is nothing for sound waves to propagate through. (*Space is not a complete vacuum, as there are hydrogen atoms floating around. But for all intents and purposes it might as well be a total vacuum) However, when J.M Straczynski was developing the TV series Babylon 5 he talked to several people from NASA for technical advice. During these talks the issue of sound in space come up, and the answer was interesting. According to those people from NASA it is technically possible to hear an explosion in space. The logic (and science) is that an explosion would create an expanding globe of gas that would carry sound waves from the explosion - especially if the explosion took place in a spacecraft that possessed an atmosphere. As far as I can tell no one has ever tried to see if this theory hold true. My thinking is that MB could see if you could hear an explosion in space, or at least in a vacuum. A small fire cracker detonated in a vacuum chamber with a number of microphones would allow them to do this, and moving the microphones would give an idea as to how close you would have to be. The tests could also be carried out by placing the cracker inside a small plastic bag filled with air, allowing them to see if that increases the distance at which anything can be heard (or if it increases the chances of anything being heard). This testing would also allow them to cover several other related myths; 'Will a gun fire in space?' - This was often posted on Disco. Physically there is no reason that a gun will not physically work in space. So the question is if gunpowder would ignite (which it will as it contains its own oxidizer). Setting off a firecracker would prove this, as would putting say a starter gun or conventional pistol loaded with a blank round inside the chamber and firing it. 'The colour of an explosion in space will depend on the internal atmosphere' - This is another B5 'myth' that came from NASA. The idea is that different atmospheres (such as methane) would/will create a different coloured explosion. This would be easy to test by filling the bag containing the fire cracker with different types of gas. According to JMS they carefully researched this for B5 to make sure that the colours of ship explosions were consistent with what the atmosphere was meant to be for that ship. Thoughts? I like it. some thoughts: 1: a standard bag of atmosphere will probably not fare well in vacuum. their gas container might end up a bit more substantial. 2: electric ignition (technically a squib instead of a firecracker) with a battery powered remote would probably be their best explosive technique. 3: they told George Lucas there was no sound in space. George Lucas ignored them. George Lucas is a millionare. Overall, I like it. I think it would make a good episode |
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Post by the light works on Aug 29, 2013 14:44:56 GMT
If you were to detonate a fire cracker in a vacuum with microphones also withing a reasonable distance from the detonation, I have no doubt that the microphones would register the "explosion." In fact, depending on distance, the particle wave front from the explosion would most likely damage the microphones. The fact that you have a bunch of particles in your "vacuum" would simply mean you no longer have a vacuum. scale and distance would have to be a consideration - as cyber said. he also pointed out that space is not true vacuum, because it has particles in it. I.E. stray hydrogen atoms, space dust, asteroids, spaceships, small planets... |
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Post by Cybermortis on Aug 29, 2013 14:58:02 GMT
The difference between vacuum and air pressure at sea level is only 14.7 psi, which I suspect is well within what plastic could withstand - maybe not a typical shopping bag but certainly the slightly thicker types of plastic MB have access to.
If you can work out the distance you could 'hear' an explosion for a small amount of explosive, you could probably estimate how far away you could hear a larger explosion.
It might be interesting to put the microphones inside small air filled boxes, to see if that might amplify any sound - meaning that you might be able to 'hear' the explosion better if you are on a ship or station.
Note; Using plastic bags to hold the air would be the only viable option here, as having a stronger or more rigid container runs the risk of creating shrapnel that could damage the microphones or vacuum chamber.
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Post by the light works on Aug 29, 2013 15:19:44 GMT
The difference between vacuum and air pressure at sea level is only 14.7 psi, which I suspect is well within what plastic could withstand - maybe not a typical shopping bag but certainly the slightly thicker types of plastic MB have access to. If you can work out the distance you could 'hear' an explosion for a small amount of explosive, you could probably estimate how far away you could hear a larger explosion. It might be interesting to put the microphones inside small air filled boxes, to see if that might amplify any sound - meaning that you might be able to 'hear' the explosion better if you are on a ship or station. Note; Using plastic bags to hold the air would be the only viable option here, as having a stronger or more rigid container runs the risk of creating shrapnel that could damage the microphones or vacuum chamber. I am not so sure that "standard" bags can withstand a full 14.7 psi pressure differential - though of course, filling them with a lower volume would allow them to be holding a lesser pressure differential. of course, the internet will not show me any figures related to bursting pressure of baglike containers - except that there is a guy who can burst three hot water bottles with his nose in under a minute. |
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Post by the light works on Aug 29, 2013 15:22:37 GMT
a "burst box" might be an alternative; where it worked on a similar principle to the chicken gun; if they could not find anyone willing to let them blow things up in their vacuum chamber.
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Post by Cybermortis on Aug 29, 2013 15:54:36 GMT
MB has the equipment needed to create their own plastic bags out of plastic sheeting - and I'd be surprised if they don't have sheets of different types of plastic lying around the shop.
They could test these plastics to see which thickness or type of plastic is best suited for the test - they don't need a vacuum chamber for this as they can simply pump air into the bags until they fail. Something that they can rig up using materials and equipment sitting around M5 very quickly.
Chamber wise they would be best off using the chambers at NASA, which are large and very efficient but also require that they very carefully plan the details of the tests to make sure that their is no risk of damaging the chamber - which is why I keep talking about plastic bags rather than boxes or other types of container, as these could create fragments that could damage the chamber.
Failing that MB could make their own vacuum chamber although this would not be as effective or large as those at NASA which might limit the tests they could do.
Going to NASA also makes sense since the 'myth' comes from them, and as such they might well be interested in seeing if the science theory holds up.
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Post by the light works on Aug 29, 2013 16:18:03 GMT
It would also be good to build a system where their "blast bag" sealed to the top of their test machine - the machine could contain any shrapnel from whatever their explosive device; while the bag produced the explosive containment failure. (keeping in mind that their explosive might also be capable of producing hazardous shrapnel; unless they are using fuel-air explosives.)
*note: in college, we used an oxygen/acetylene "gas cannon" for most of our theatrical explosions, as the only expendable besides the welding gas that was necessary was common masking tape - which simply kept the gases from wandering off before time to trigger the explosion. EDIT: it also meant the only possible shrapnel was the masking tape.
another alternative testing means could consist of simply releasing air pressure into their test bags (in vacuum) until they fail - in this case they could simply use any inflatable bag; or find the one that gave them the best "bang" in free air. - that would also minimize the risk of shrapnel damage, though it wouldn't let them do the secondary "explosion color" testing.
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Post by Cybermortis on Aug 29, 2013 16:32:33 GMT
You don't need to test the pressure limits of their bag designs in a vacuum chamber. Just inflate them on the desk in the shop, those that can withstand 14.7 psi (ideally a little more than that*) will be able to hold air in a vacuum. Its quick, easy and requires nothing more than a air pump with a pressure gage.
(*You'd want to find a balance here. The bag needs to be capable of holding air at atmospheric pressure, but if it is too strong it will absorb some of the energy from the explosion and might mess up the results. Ideally you'd want something that could hold between 15-20 psi.)
An alternative to using fire crackers would be to place a small amount of gunpowder in a plastic bag and remove the air to compact it. Then you can set it off with a spark. This would remove any possibility of producing any shrapnel that could damage the chamber. I suspect that a standard fire cracker could not do any damage to one of NASA's vacuum chambers anyway, but given the expense of such equipment it would be better safe than sorry. An added advantage of using their own pre-packaged 'fire crackers' would be that they could alter the amount of charge.
The problems with designing anything to catch fragments would be the risk that the catcher could potentially produce fragments itself. And even if it doesn't it will absorb and deflect any wave of gas that it hits - which could screw up the results.
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Post by the light works on Aug 29, 2013 16:40:39 GMT
you misunderstood the purpose of the alternative test - the purpose was an alternate source of the explosive force; if they were disallowed from using pyrotechnics in the vacuum chamber. - basically produce their explosive expansion by blowing up balloons until they burst.
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Post by the light works on Aug 29, 2013 16:43:37 GMT
You don't need to test the pressure limits of their bag designs in a vacuum chamber. Just inflate them on the desk in the shop, those that can withstand 14.7 psi (ideally a little more than that*) will be able to hold air in a vacuum. Its quick, easy and requires nothing more than a air pump with a pressure gage. (*You'd want to find a balance here. The bag needs to be capable of holding air at atmospheric pressure, but if it is too strong it will absorb some of the energy from the explosion and might mess up the results. Ideally you'd want something that could hold between 15-20 psi.) An alternative to using fire crackers would be to place a small amount of gunpowder in a plastic bag and remove the air to compact it. Then you can set it off with a spark. This would remove any possibility of producing any shrapnel that could damage the chamber. I suspect that a standard fire cracker could not do any damage to one of NASA's vacuum chambers anyway, but given the expense of such equipment it would be better safe than sorry. An added advantage of using their own pre-packaged 'fire crackers' would be that they could alter the amount of charge. The problems with designing anything to catch fragments would be the risk that the catcher could potentially produce fragments itself. And even if it doesn't it will absorb and deflect any wave of gas that it hits - which could screw up the results. well, I guess with dark gunpowder in a clear bag you could theoretically trigger it with a high energy laser, and not have any ignition hardware... but doesn't it take a certain amount of containment to develop an explosion with gunpowder? |
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Post by Cybermortis on Aug 29, 2013 17:20:30 GMT
you misunderstood the purpose of the alternative test - the purpose was an alternate source of the explosive force; if they were disallowed from using pyrotechnics in the vacuum chamber. - basically produce their explosive expansion by blowing up balloons until they burst. Not a bad idea for a small scale in house test. They could certainly test the basic principle this way, as making a vacuum chamber from clear plastic piping should be easy enough. I think that if NASA is unwilling to allow them to run tests using pyrotechnics they would be better off making their own chamber - a large pressure tank with a couple of slots cut out for very heavy duty plastic 'glass' windows would do the trick. (And would allow them to use as much explosive as they like, up to and including C4 which NASA is unlikely to let them use regardless.) There is not much point in them going to NASA just to burst some balloons - too much hassle for too little result. The chambers at NASA are larger, and far more efficient at removing air than anything MB is likely to be able to produce in the shop - or at least without a hell of a lot of work and a very good pump, the kind they will not have in the shop. Which is why they would be the better option here. Being larger they are also less likely to cause false readings by vibrations being passed to the microphones through the chamber walls. Then again, if this interests NASA they may well be willing to help MB out by assisting in the design of a suitable chamber and maybe even be able to provide some equipment MB might otherwise have trouble getting - for example they may have a couple of pressure tanks far larger than anything MB could get their hands on and which would be considered expendable. My thinking here is that NASA may not have been willing to run such tests, as there is no particular reason to do so - or at least no reason they could justify spending money on it and risking equipment that could be put answering more important questions, such as if the new space suits are really air tight*. However helping MB run the tests would not only allow them to see what would really happen, but could be justified on the grounds that it is good PR to appear and/or be mentioned on a TV show. (*Best to find this out before someone takes a new suit out for a space walk....) A larger 'expendable' chamber might also be suitable to test if you might hear sound from a spacecraft that flies past you with its engines on full blast - The logic here being that the gasses coming out of the tail pipe are going to carry sound with them. *Edit* An additional space-sound myth is; Astronauts can talk to each other if the radio goes down by pressing helmets together, allowing the sound to pass from one helmet to the other. You just need two helmets fitted with a speaker and microphone and pressed together. |
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Post by the light works on Aug 29, 2013 17:51:21 GMT
an argument for using NASA facilities for a balloon burst testing session is that they could set up multiple tests; and not have to start the evacuation from scratch for each test. - or even get a measure of how little air in the vacuum chamber would still effectively transmit the sound.
if they got to do live pyro testing, I would also want to see either burst discs or pressure transducers in use to measure the blast wave propagation; and compare it to similar blasts in atmosphere.
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Post by User Unavailable on Aug 29, 2013 18:15:25 GMT
Yeah, there has to be confinement of the gasses from the powder burning, to get a "bang". If you cut open a firecracker and pour out the powder and light it, it just burns, with no bang.
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Post by the light works on Aug 29, 2013 18:22:57 GMT
Yeah, there has to be confinement of the gasses from the powder burning, to get a "bang". If you cut open a firecracker and pour out the powder and light it, it just burns, with no bang. I do find myself thinking slow motion firecrackers in vacuum might be in the running for the top ten cool explosions on mythbusters. |
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Post by User Unavailable on Aug 30, 2013 4:01:53 GMT
Yeah, there has to be confinement of the gasses from the powder burning, to get a "bang". If you cut open a firecracker and pour out the powder and light it, it just burns, with no bang. I do find myself thinking slow motion firecrackers in vacuum might be in the running for the top ten cool explosions on mythbusters. from a mortar platoon. This how we dispose of all those left over Increments, after a day of firing. The ones in this video are the newer "Donut" charges that were just becoming standard when I got out of the Marines in 90. There are 4 of these per round. Charge 4 is a charge for max range, you remove charges and change elevation of the gun to reduce range of the round. So you have left over charges (increments) at the end of the day. When I first went in the Corps, the 81mm rounds had 9 cloth increment bags on the round, so at the end of the day we would have a pretty big pile to burn, from an 8 gun platoon. Judging by the "motivating" haircut the young troop had, I would wager he was a "boot" in training, as we're the ones standing around close and watching. They learned real quick that increment burning is not something you stand around close and watch as it gets REAL HOT, REAL FAST and the heat can be felt even a hundred meters away. Here is a properly distanced increment burning. though he didnt make a long enough fuse of powder and had to run away as it got HOT. Increment burning a are so bright you can get eye injury akin to looking at a welder flash. We never looked directly at the burning increments. (Sorry for the off topic bits, I remembered Increment Burning when searching for videos of burning gunpowder) |
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Post by the light works on Aug 30, 2013 13:31:55 GMT
I do find myself thinking slow motion firecrackers in vacuum might be in the running for the top ten cool explosions on mythbusters. from a mortar platoon. This how we dispose of all those left over Increments, after a day of firing. The ones in this video are the newer "Donut" charges that were just becoming standard when I got out of the Marines in 90. There are 4 of these per round. Charge 4 is a charge for max range, you remove charges and change elevation of the gun to reduce range of the round. So you have left over charges (increments) at the end of the day. When I first went in the Corps, the 81mm rounds had 9 cloth increment bags on the round, so at the end of the day we would have a pretty big pile to burn, from an 8 gun platoon. Judging by the "motivating" haircut the young troop had, I would wager he was a "boot" in training, as we're the ones standing around close and watching. They learned real quick that increment burning is not something you stand around close and watch as it gets REAL HOT, REAL FAST and the heat can be felt even a hundred meters away. Here is a properly distanced increment burning. though he didnt make a long enough fuse of powder and had to run away as it got HOT. Increment burning a are so bright you can get eye injury akin to looking at a welder flash. We never looked directly at the burning increments. (Sorry for the off topic bits, I remembered Increment Burning when searching for videos of burning gunpowder) ah, but it is the comparison to doing it without an atmosphere I am interested in seeing. |
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Post by User Unavailable on Aug 30, 2013 14:32:12 GMT
Here is a gun being fired in a vacuum.It answered no only the "age old" question asked thousands of times on the old boards, but demonstrates the sound not traveling through a vacuum very well.
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Post by the light works on Aug 30, 2013 14:57:11 GMT
Here is a gun being fired in a vacuum.It answered no only the "age old" question asked thousands of times on the old boards, but demonstrates the sound not traveling through a vacuum very well. "the oxygen is in the bullets" kind of dumps the whole "science content" portion of the clip, though. now I want to know, though - how much of the sound we heard was transfer through the structure, how much was the bullet punching through the containment, and how much was gases expanding into the vacuum. perpetual curiosity can be an inconvenience. |
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