|MLA Citation:||Bloomfield, Louis A. "Question 171"|
How Everything Works 23 Jul 2018. 23 Jul 2018 <http://howeverythingworks.org/print1.php?QNum=171>.
I talked with Kathryn Thornton, a former NASA astronaut who has actually performed combustion experiments in space and she described those experiments to me. In them, a drop of fuel was supported on a fiber and ignited. The flame front radiated outward from the fuel drop at ignition to form a spherical shell around the drop, which shrank slowly as it was consumed. Because convection requires gravity, there was no rising current of air to bring in new oxygen and to sweep away the burned gases. Instead, oxygen had to diffuse into the burning sphere and it did so quite slowly—the burns lasted for as much as 30 seconds on only a few cc's of fuel. Water vapor that formed during the combustion also had a tendency to diffuse into the fuel and dilute it so that it eventually stopped burning.