What would a flame, in a space with no gravity, look and burn like?
If a flame under zero gravity burns, it has to have oxygen. If the atmosphere around the flame is oxygen, I suspect it would look pretty much the shape we see here on earth, but shaped that way by the velocity of the fuel and oxygen mix from the ? burner. Maybe a bunsen burner would be an example. The fuel gas is forced under pressure through an orofice and up the tube, and venturi effect pulls in oxygen to mix. So the gas mix has velocity exiting the pipe. The only trick I see in this is that to see a vertical flame as on earth, the observer would have to orient his/ herself so it appears vertical to him/ her.
There would be no flame in space as we see on earth because there would be no oxygen. to support combustion. On the other hand if a welding torch were used, supplying oxygen as well as fuel, there would be combustion. The flame would probably be larger because the vapours would expand rapidly in a vacuum, and there would be no gravity so that would make the flame dissipate more rapidly. Since there would be rapid heat loss as well, there might have to be a shield of sorts to contain the heat near its application point, and this would also affect the shape of the flame. It is much more likely in my mind that this type of heat application would be better with electrowelding rather than combustion, because of the difficulty containing the heat.
