gml@ssc-vax.UUCP (Gregory M Lobdell) (07/18/85)
... in space?
This question came up the other day in discussion. We seemed to think
that there would be problems because in the absence of a gravity field
the heated air would not rise. Thus CO2 would not be pulled away from
the area of burning and O2 would not be pulled in. Therefore
combustion would not be continuous.
What do you all think. Have there been any experiments in this area.
I can see how NASA would be leary of any such experiment. A fire in
space would be worse than a fire on a sailing vessel. However, if the
above hypothisis is correct, such a fire would never happen. And if
there was a fire, where would you point the fire extiguister?
Wanting to go for a ride on the Shuttle!
Gregg Lobdell
Boeing Aerospace {I only work for them and their opinions aren't mine}randy@utcsri.UUCP (Randall S. Becker) (07/21/85)
> ... in space? > > This question came up the other day in discussion. We seemed to think > that there would be problems because in the absence of a gravity field > the heated air would not rise. Thus CO2 would not be pulled away from > the area of burning and O2 would not be pulled in. Therefore > combustion would not be continuous. Actually, I would suspect that this would depend on the diffusion rate of CO2 in the ambient atmosphere. If CO2 would diffuse at a high enough rate then (assume the presence of O2) the candle should continue to burn at an ever decreasing rate. Forgive me if this sounds rediculous. It's been a while since I've taken any chemistry. Randy -- Randall S. Becker Usenet: ..!utcsri!randy CSNET: randy@toronto
horst@leadsv.UUCP (John Selhorst) (07/23/85)
In article <1273@utcsri.UUCP>, randy@utcsri.UUCP (Randall S. Becker) writes: > > that there would be problems because in the absence of a gravity field > > the heated air would not rise. Thus CO2 would not be pulled away from > > the area of burning and O2 would not be pulled in. Therefore > > combustion would not be continuous. > > Actually, I would suspect that this would depend on the diffusion rate of > CO2 in the ambient atmosphere. If CO2 would diffuse at a high enough rate > then (assume the presence of O2) the candle should continue to burn at an > ever decreasing rate. Wouldn't the rate of decrease stabilize at some equilibrium? I want to know what a flame in zero gravity looks like. John Selhorst {(ucbvax!dual!sun) (ihnp4!qubix)}!sunncal!leadsv!horst {allegra ihnp4 dual}!fortune!amdcad!cae780!leadsv!horst
tmoody@sjuvax.UUCP (T. Moody) (07/24/85)
> ... in space? > > This question came up the other day in discussion. We seemed to think > that there would be problems because in the absence of a gravity field > the heated air would not rise. Thus CO2 would not be pulled away from > the area of burning and O2 would not be pulled in. Therefore > combustion would not be continuous. > > What do you all think. Have there been any experiments in this area. > I can see how NASA would be leary of any such experiment. A fire in > space would be worse than a fire on a sailing vessel. However, if the > above hypothisis is correct, such a fire would never happen. And if > there was a fire, where would you point the fire extiguister? > > Wanting to go for a ride on the Shuttle! > Gregg Lobdell > Boeing Aerospace {I only work for them and their opinions aren't mine} As to whether a candle would burn in null-g: Seems to me that the kinetic energy of combustion would take care of expelling the CO2. As for the oxygen supply, I suspect that's done by atmospheric pressure, not gravity, anyway. It would *look* different, though.
gnome@olivee.UUCP (Gary Traveis) (07/24/85)
> > ... in space? > > > > This question came up the other day in discussion. We seemed to think > > that there would be problems because in the absence of a gravity field > > the heated air would not rise. Thus CO2 would not be pulled away from > > the area of burning and O2 would not be pulled in. Therefore > > combustion would not be continuous. > > Actually, I would suspect that this would depend on the diffusion rate of > CO2 in the ambient atmosphere. If CO2 would diffuse at a high enough rate > then (assume the presence of O2) the candle should continue to burn at an > ever decreasing rate. > I think that the first statement is correct - but the candle would still burn through "flicker oscillation". As the globular flame expands it would choke it's own combustion. Then, on partial flame-out, denser, colder air would rush in around the wick. Unless some strange around-the-wax-base convection currents can be set up when it starts, it would probably oscillate. Gary (hplabs,allegra,ihnp4)oliveb!olivee!gnome
gml@ssc-vax.UUCP (Gregory M Lobdell) (07/25/85)
> > Actually, I would suspect that this would depend on the diffusion rate of > > CO2 in the ambient atmosphere. If CO2 would diffuse at a high enough rate > > then (assume the presence of O2) the candle should continue to burn at an > > ever decreasing rate. > > Wouldn't the rate of decrease stabilize at some equilibrium? I want to know > what a flame in zero gravity looks like. The problem might be that the rate would stabilize below the minimum needed to support combustion, i.e. not enough heat generated to melt wax, drive CO2 diffusion, etc. The flame would probably be round, or slightly flattened on the side near the fuel source. The current space program uses a 100% O2 atmosphere. If you lit a flame in such an atmosphere, would all the dust and other random particles ignite in the presence of the flame? >From: fluke!allegra!convex!hosking (Doug Hosking) > >I don't know, but I'd hate to think of what the melted wax would do if >it did burn! But it seems to me that the surface tension of the wax would be great enough to keep it from floating away, and if it did float away it would probably skin over before it caused any problems.
inc@fluke.UUCP (Ensign Benson, Time Cadet) (07/26/85)
*** REPLACE THIS LINE WITH YOUR MESSAGE *** *** NO, WHY DON'T YOU REPLACE YOUR STUPID LINE WITH MY MESSAGE? *** The questoon was: Would a candle burn... > ... in space? > > This question came up the other day in discussion. We seemed to think > that there would be problems because in the absence of a gravity field > the heated air would not rise. Thus CO2 would not be pulled away from > the area of burning and O2 would not be pulled in. Therefore > combustion would not be continuous. I think that if NASA is really thinking about experimenting with extratereestrial sexual relations, they may find that the candle burns at both ends! Good question, though - please post the most sincere-sounding answer. -- Ensign Benson -Time Cadet- _-_-_-_-_-_-_-_-_-_-_-The Digital Circus, Sector R-_-_-_-_-_-_-_-_-_-_-_
mahar@weitek.UUCP (mahar) (07/26/85)
In one of G Harry Stine's books, I don't remember the title, he discusses at length what happens to a candle in zero G. Candles have been studied on airplanes in ballistic flight. A burning candle seems to go out as soon as zero G is reached. The candle starts burning again when gravity returns. Combustion is still taking place in zero G. The lack of heat convection prevents an open flame. I read this a few years ago, so more work may have been done since then.
pcf@drux3.UUCP (FryPC) (07/26/85)
> ... in space? > > This question came up the other day in discussion. We seemed to think > that there would be problems because in the absence of a gravity field > the heated air would not rise. Thus CO2 would not be pulled away from > the area of burning and O2 would not be pulled in. Therefore > combustion would not be continuous. I do not think that the O2/CO2 supply is the problem. In a 'theoretical' still air, there is no O2, the candle can not burn, but in any 'real' (sic) environment, there should be enough air movement to keep combustion going. I think there are other problems:- My understanding of how a candle works, once it is burning in normal G: The heat from the flame melts the solid wax. Capilliary action draws the molten wax up the wick. Increased heat vaporises the molten wax. The vapor burns using oxygen and producing CO2 H2O etc. Only the vapour is flammable, the non-flammable liqud wax forming a pool around the base of the wick stops the flame from going in that direction and melting the wax faster than it can be burned. In zero G: The heat from the flame melts the solid wax. Capilliary action draws some of the molten wax up the wick the rest floats off. Increased heat vaporises the molten wax. The vapor burns using oxygen and producing CO2 H2O etc. The flame would burn in all directions, the pool of melted wax would not remain to stop the flame from travelling along the wick so the candle would soon turn itslef into floting blobs of hot/liquid wax. My theory: The candle burns, but not for long and is very messy. Experiment: Take two candles, light them both. Invert one of the candles. Observe how they burn. Average the results. Peter Fry drux3!pcf P.S. All this is, of course, wild speculation from a position of inteligent ignorance.
werner@aecom.UUCP (Craig Werner) (07/29/85)
> > ... in space?
You'd have to ask the Russians. As long as the Americans use a pure
Oxygen atmosphere (they did thru Skylab, and I believe they still do), this
is one experiment that is not going to be done on the shuttle.
--
Craig Werner
!philabs!aecom!werner
"The world is just a straight man for you sometimes"peter@kitty.UUCP (Peter DaSilva) (07/29/85)
I think the experiment's been done. For an amusing application see "Stardance", by Spider Robinson.
mike@bambi.UUCP (Michael Caplinger) (07/29/85)
Arthur C. Clarke used this problem in his juvenile novel ISLANDS IN THE SKY. A young "space cadet" is fooled into believing that the air in a spacecraft cabin is going bad when an older cadet lights a match and it goes out almost immediately. After the joke is exposed, the older cadet demonstrates that if the match is moved about while burning, it won't go out. Of course, there's no guarantee that Clarke was right about this. - Mike
gnome@olivee.UUCP (Gary Traveis) (07/29/85)
> The current space program uses a 100% O2 atmosphere. If you lit a > flame in such an atmosphere, would all the dust and other random > particles ignite in the presence of the flame? > Uh, wrong. The atmosphere is far from 100% O2. Remember the accident that killed four astronauts? That was the last time pure O2 was used, and that was many years ago.
hollombe@ttidcc.UUCP (The Polymath) (07/31/85)
In article <1816@aecom.UUCP> werner@aecom.UUCP (Craig Werner) writes: > You'd have to ask the Russians. As long as the Americans use a pure >Oxygen atmosphere (they did thru Skylab, and I believe they still do), this >is one experiment that is not going to be done on the shuttle. I thought we stopped using 100% O2 after the Apollo 13 disaster. Can someone confirm the current state of such? -_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ The Polymath (aka: Jerry Hollombe) Citicorp TTI Common Sense is what tells you that a ten 3100 Ocean Park Blvd. pound weight falls ten times as fast as a Santa Monica, CA 90405 one pound weight. (213) 450-9111, ext. 2483 {philabs,randvax,trwrb,vortex}!ttidca!ttidcc!hollombe
jkw@lanl.ARPA (07/31/85)
> > > ... in space? > > You'd have to ask the Russians. As long as the Americans use a pure > Oxygen atmosphere (they did thru Skylab, and I believe they still do), this > is one experiment that is not going to be done on the shuttle. > Oh I don't know about that. Surely NASA could design an experiment to enclose a candle and a whiff of "normal" atmosphere for no more than 10 or 20 million $. Look what they did with Coke and Pepsi :-).
fred@mnetor.UUCP (Fred Williams) (08/01/85)
In article <1816@aecom.UUCP> werner@aecom.UUCP (Craig Werner) writes: >> > ... in space? > > You'd have to ask the Russians. As long as the Americans use a pure >Oxygen atmosphere (they did thru Skylab, and I believe they still do), this >is one experiment that is not going to be done on the shuttle. > Craig Werner I understand that the oxygen environment is at 1/5 atmospheric pressure. It therefore exerts the same pressure as the partial pressure of oxygen at ground level. Otherwise it would upset the blood chemistry of the astronauts. Burning can then be expected to take place with no more or less violence than here on earth. Whether this is acceptable to shuttle astronauts is another matter. Fires do happen on earth and if one were to start aboard the shuttle it would be of little use to calmly walk to the nearest exit. Also to perform the experiment the fans used to circulate the air on the shuttle would have to be shut down, and the air given a time to settle. Disturbances due to breathing could probably be tolerated and it would not be too much of a problem for people there to breath carefully to avoid inhaling the same air they just exhaled. It would only take a minute or two for the experiment anyway. I think it would be a good bit of PR to televise back to earth. Cheers, Fred Williams
henry@utzoo.UUCP (Henry Spencer) (08/01/85)
Actually, I believe if you check you will find that while Mercury, Gemini,
and Apollo used pure oxygen, Skylab did not and the Shuttle does not.
They do run at somewhat lower pressure than Earth surface, so the mix is
oxygen-rich relative to normal air, but there is a fair bit of nitrogen
in it. This is why Shuttle astronauts going outside spend a long time
pre-breathing pure oxygen (long enough that it's starting to be a serious
nuisance): the space suits use pure oxygen at the lowest possible pressure,
and the astronauts have to flush the nitrogen out of their bodies before
they decompress to suit pressure.
--
Henry Spencer @ U of Toronto Zoology
{allegra,ihnp4,linus,decvax}!utzoo!henryfred@mnetor.UUCP (Fred Williams) (08/02/85)
In article <440@olivee.UUCP> gnome@olivee.UUCP (Gary Traveis) writes: (from somebody.)... >> The current space program uses a 100% O2 atmosphere. If you lit a >> flame in such an atmosphere, would all the dust and other random >> particles ignite in the presence of the flame? >> > >Uh, wrong. The atmosphere is far from 100% O2. Remember the >accident that killed four astronauts? That was the last time >pure O2 was used, and that was many years ago. That was the last time O2 was used at full atmospheric pressure. I had been under the impression that afterwards, on launch they used 80% nitrogen & 20% oxygen. The mixture then reduced to pure oxygen at much lower pressure during boost phase. In the past few days there have been several postings declaring an O2-N2 mixture is standard throughout shuttle flights. This could very well be the case. I could be out of date. Regardless, the risk of fire from a candle experiment would not be increased by the shuttle air. I don't think. Cheers, Fred Williams
b-davis@utah-cs.UUCP (Brad Davis) (08/02/85)
In article <65@ssc-vax.UUCP>: >The current space program uses a 100% O2 atmosphere. If you lit a >flame in such an atmosphere, would all the dust and other random >particles ignite in the presence of the flame? > >In article <1816@aecom.UUCP> werner@aecom.UUCP (Craig Werner) writes: >> You'd have to ask the Russians. As long as the Americans use a pure >>Oxygen atmosphere (they did thru Skylab, and I believe they still do), this >>is one experiment that is not going to be done on the shuttle. > >I thought we stopped using 100% O2 after the Apollo 13 disaster. Can >someone confirm the current state of such? > Are you sure about this? At the beginning of the Apollo program we were using close to a 100% O2 atmosphere (90+%) and lost 3 astronauts during a test when a fire swept through the capsule. (I think it was Apollo 3.) NASA decided that they might have been saved had the atmosphere been less O2. I think that the Russians used a He - O2 mixture at the time. I also think that NASA changed after that. A 100% O2 mixture would burn the astronauts lungs. The biggest reason for using a high concentration of O2 is that the pressure of the cabin can be kept lower, simplifing sealing the cabin. -- Brad Davis {ihnp4, decvax, seismo}!utah-cs!b-davis b-davis@utah-cs.ARPA
henry@utzoo.UUCP (Henry Spencer) (08/02/85)
> >Uh, wrong. The atmosphere is far from 100% O2. Remember the > >accident that killed four astronauts? That was the last time > >pure O2 was used, and that was many years ago. > > That was the last time O2 was used at full atmospheric pressure. > I had been under the impression that afterwards, on launch they > used 80% nitrogen & 20% oxygen. The mixture then reduced to pure > oxygen at much lower pressure during boost phase. More specifically, the Apollo flights all started out with the cabin full of 80/20 mix and the astronauts breathing pure oxygen (through either oxygen masks or their spacesuits, not sure which). The cabin atmosphere changed to pure oxygen during boost. The astronauts had to be breathing pure oxygen from the start to avoid decompression problems. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry
ix241@sdcc6.UUCP (ix241) (08/06/85)
During Apollo and earlier missions NASA always used a reduced pressure pure oxygen enviroment on missions. They used full pressure O2 for many ground tests until the disaster of Apollo 1. Currently an Earth normal atmosphere is used in the Shuttle. That is the reason space walkers have to prebreathe. The suits use the 4PSI pure O2 that was used in the older missions. The main reason for the reduced pressure, however is to make the suits easier to operate. Less work against pressure. John Testa UCSD Chemistry sdcsvax!sdcc6!ix241
moose@ames.UUCP (Mary Kaiser) (08/07/85)
> > > ... in space? > > You'd have to ask the Russians. As long as the Americans use a pure > Oxygen atmosphere (they did thru Skylab, and I believe they still do), this > is one experiment that is not going to be done on the shuttle. > > -- > Craig Werner > !philabs!aecom!werner > "The world is just a straight man for you sometimes" *** REPLACE THIS LINE WITH YOUR TWO CENTS WORTH *** Actually, the astronauts on Skylab attempted to use some conventional (i.e. no forced-air) gas burners to perform some mineral studies. The burners apparently kept going out. I don't know about the wax melting stuff...too low tech for NASA's taste I guess. Now water bubbles....
hollombe@ttidcc.UUCP (The Polymath) (08/07/85)
In article <1688@mnetor.UUCP> fred@mnetor.UUCP (Fred Williams) writes: >I had been under the impression that afterwards, on launch they >used 80% nitrogen & 20% oxygen. The mixture then reduced to pure >oxygen at much lower pressure during boost phase. In the past few >days there have been several postings declaring an O2-N2 mixture is >standard throughout shuttle flights. This could very well be the case. >I could be out of date. From _The Space Shuttle Operator's Manual_ by K.M. Joels, G.P. Kennedy, and D. Larkin, Ballantine Books, 1982, section 2.2, paragraph 2: "An atmosphere like the earth's is maintained in the crew compartment. Atmospheric pressure is 14.7 psi ... the same as standard sea-level conditions. The atmosphere consists of 79% nitorgen and 21% oxygen, again very close to what you left on earth. In an emergency, cabin pressure is reduced to 8.0 psi ..." -_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ The Polymath (aka: Jerry Hollombe) Citicorp TTI Common Sense is what tells you that a ten 3100 Ocean Park Blvd. pound weight falls ten times as fast as a Santa Monica, CA 90405 one pound weight. (213) 450-9111, ext. 2483 {philabs,randvax,trwrb,vortex}!ttidca!ttidcc!hollombe