rmartin@clear.com (Bob Martin) (02/02/91)
In article <7332@crash.cts.com> dang@crash.cts.com (Dan Gookin) writes: > >I have this perverse curiosity about what fire--specifically a >flame--would look like in space. > >If figure if you lit a match, it probably would lack the familiar >conical shape the flame has here on earth. In fact, I think it would >look like a point of light or perhaps a spherical flame. (And >then my mind thought "Ooops, pure oxygen atmosphere--Whoosh!) > >But what would fire look like in space? or actually, zero-g? Would >there be flames? Would it be spotty and amorphous? There is no >scientific reason behind this; just curiosity (a mind-exercise, >if you will). > >dang This is a mind-exercise that I find rather tantalizing... First of all, what is a flame? A flame is a stream of incandescent particles and gasses. The incandescense is due to the heat produced by the oxygen-fuel reaction. The shape of the flame is due the the fact that the hot gases are less dense and thus rise away from the source of heat. (convection). This creates a current of fresh oxygenated air flowing past the zone of reaction allowing the reaction to continue as long as their is fuel. Without gravity (or a suitable substitute such as linear acceleration or angular momentum) there would be no reason for the hot gases surrounding the reaction zone to move out of the reaction zone. Thus the only way that oxygen could get to the site of the reaction is diffusion, and this would seem a very slow method indeed. probably the reaction would proceed so slowly that the reaction site would cool to below ignition temperatures and the reaction would cease altogether. In short there would be no sustained flame at all (except on the net ;-) and a very brief flash of incandescense. However, what if you blew on it! You could keep your match burning by constantly blowing on it with a gentle stream of air. Or by waving it around in a gentle manner. Stop for an instant and the flame might go out. (This seems like an interesting ploy for a sci-fi short). Flames could exist in a ventilated area as long as the air was moving at a rate sufficent to keep the reaction site from cooling down too much. Also it seems likely that you could create a small airflow by attracting the ions created near the reaction zone with an electrostatic charge. Thus you might be able to keep the flame buring by placing it between two charged plates. The flame would point at the plate which was attracting the most ions. If you decrease the voltage on the plates the airflow would diminish and the flame would get smaller. Increase the voltage and the flame becomes bigger. !!Electrically controlled fire!! On a rotating space station, convection currents would be generated by the centripetal force normal to the floor of the station. But they would also suffer corriolos (sp) effects. So flames would burn pointing more or less towards the hub of the station, but a large enough flame would exhibit a curious curve in the direction of rotation. A thin flamable thread might be able to burn even in the abscense of any airflow because the reaction site would travel along the thread quickly enough for it to reach sufficient oxygen to keep the temperature of the reaction site high enough. Similarily a very thin sheet of paper might exhibit the same effect. In the case of the thread, the "flame" might appear as a small globe of incandescing gases moving along the thread. In the case of the sheet of paper it might appear somewhat cylindrical bending and turning as if made inroads into the fuel. A bunsen burner would probably burn well, since the flow of gases out of the burner would stir the local air up enough. The same is probably true of a conventional gas stove, or a butane cigarette lighter. ------- I wonder if any experiments of this nature have been tried on board the zero-gee aircraft???? -- +-Robert C. Martin-----+:RRR:::CCC:M:::::M:| Nobody is responsible for | | rmartin@clear.com |:R::R:C::::M:M:M:M:| my words but me. I want | | uunet!clrcom!rmartin |:RRR::C::::M::M::M:| all the credit, and all | +----------------------+:R::R::CCC:M:::::M:| the blame. So there. |
Paul.Blase@nss.FIDONET.ORG (Paul Blase) (02/05/91)
DG> I have this perverse curiosity about what fire--specifically a DG> flame--would look like in space. An experiment to do just this was performed on the shuttle recently. Has anyone seen the results yet? --- via Silver Xpress V2.26 [NR] -- Paul Blase - via FidoNet node 1:129/104 UUCP: ...!pitt!nss!Paul.Blase INTERNET: Paul.Blase@nss.FIDONET.ORG
gregc@cimage.com (Greg Cronau) (02/05/91)
In article <10134@ncar.ucar.edu> strandwg@ncar.ucar.edu (Gary Strand) writes: >> Dan Gookin > >> If figure if you lit a match, it probably would lack the familiar conical >> shape the flame has here on earth. In fact, I think it would look like a >> point of light or perhaps a spherical flame. > > Why? What effect does gravity have on the burning particles, relative to > the forces they feel from the other heated particles around them? I would > think that since gravity plays such a small role in what a flame looks > like, it would look the same on the Shuttle (say) as here on earth. >-- >Gary Strand There is only one success -- to be able >Internet: strandwg@ncar.ucar.edu to spend your life in your own way. >Voicenet: (303) 497-1336 - Christopher Morley There is a reason that a match flame has a conical shape pointed upwards. The flame heats the air. Hot air is less dense than cold air, hence an equal volume of hot air is lighter than the surrounding cold air. This causes the hot air to rise and the cold air to fall into the space left by the hot air. This is what makes hot air balloons work. WHICH WAY IS *UP* IN ZERO-G?!?! There is *NO WAY* that a match flame would be conical in zero-g unless you were waving it around in your hand. The hot air *would* be less dense, but *gravity* is what makes that less-dense air rise! A flame has just as much chance burning with a conical shape in zero-g as a flame on earth has of burning with the flame pointed down or sideways. gregc@cimage.com
brndlfly@athena.mit.edu (Matthew T Velazquez) (02/10/91)
Okay, think about this: If, as most have been saying, a flame lit in zero gravity would simply deplete the oxygen in the immediate vicinity and go out, is there any sort of procedure for a fire on board something like the Shuttle once it reaches orbit? Anyone with first- or second-hand knowledge? T Velazquez MIT Aero/Astro brndlfly@athena.mit.edu
bdietz@sdcc13.ucsd.edu (Jack Dietz) (02/11/91)
In article <1991Feb9.163542.11355@athena.mit.edu> brndlfly@athena.mit.edu (Matthew T Velazquez) writes: >If, as most have been saying, a flame lit in zero gravity would simply deplete >the oxygen in the immediate vicinity and go out, is there any sort of procedure >for a fire on board something like the Shuttle once it reaches orbit? Anyone >with first- or second-hand knowledge? > I have neither, but pulling out my old and dog-eared copy of The Space Shuttle's Operator's Manual, it shows diagrams of most of the bays inside the front module. Each of these bays has at least one fire extinguisher shown. Furthermore, a control panel on the far left of the commander's seat has controls for monitoring smoke alarms and manually setting off the various extinguishers. Don't worry, they thought of that... :) -- Jack >> Restriction alt.swedish.chef.bork.bork.bork has been removed. Jack Dietz (bdietz@ucsd.edu) UCSD Comp Eng Sophomore <<big deal>>
finley@snuffy.lerc.nasa.gov (Brian Finley) (02/12/91)
In article 11310 Alan Hepburn states: >Wasn't this experiment run on the last Shuttle flight? At least, I >thought I remembered hearing that one of the astronauts was going to >try lighting a match, or a candle, to evaluate the effects of microgravity >on a flame (a hot one, not a verbal one). The experiment he refers to is the Solid Surface Combustion Experiment which was developed here at NASA Lewis. The experiment did fly on the last shuttle mission and will fly on several more missions. A sample of ashless paper was burned and filmed for appoximately one minute. Future experiments will use different materials to burn and different levels of oxygen in the burn chamber. The next scheduled flight of the experiment is on the SLS-1 mission in MAY '91 STS-40. One of the future materials to be burned will be polymethylacrylate (plexiglass). The project objectives are:(I took this from one of there states reports) The objective of the Solid Surface Combustion Experiment is to determine the mechanism of gas-flame spread over solid fuel surfaces in the absence of buoyancy-induced or externally imposed gas-phase flow. Measurements in low-gravity environment of flame shape and rate of flame spread will be made. This data will provide insight into relative importance of gas-phase momentum generated by vaporization/pyrolysis of the fuel surface and the diffusion of gas-phase fuel in controlling fuel/air mixing. Temperature measurements of both the fuel surface and the gas phase will provide an indication of forward heat conduction in both the solid and the vapor phases; it also will provide qualitative information on the radiant heat flux to and from the fuel surface. The Principal Investigator for the SSCE is Prof. R. Alternkirch of Mississippi State University. -- ---------------- Brian Finley / To err is human-and to blame it on a computer is even more so Internet: finley@snuffy.lerc.nasa.gov Phone: +1 216-891-2975