text: The flame itself is not affected by gravity.  It will burn as long as there is oxygen present in the right quantities.  The difference is that in gravity, hot air rises.  This allows the air to move upward past the flame and causes the flame to stand 'up'.  In zero gravity, the hot air does not rise as there is no 'up'.  The flame is more of a sphere shape and sputters because the oxygen is being consumed by the flame and the air is not moving.  A normal looking flame can be achieved in space if you artificially move the air by blowing on it or with a fan.