NASA extinguishes experiment about setting things on fire in space NASA has concluded its Spacecraft Fire Safety Experiment (Saffire) with a test onboard a Northrop Grumman Cygnus spacecraft after it departed from the International Space Station (ISS). The final experiment, Saffire-VI, was sent to the ISS in August 2023 and concluded on January 9, when the Cygnus it was traveling on safely …
Have they worked out the manner in which things burn and flames propagate in a gravity free atmosphere with low airflow rates?
Eg, If after a few bevvies celebrating a successful spacewalk, Tim Peake drops his unextinguished ciggie onto his bedside stash of old copies of Razzle, what happens next?
《drops his unextinguished ciggie onto his bedside stash of old copies of Razzle》
I imagine the "ciggie" would have floated off on the slightest air current and only by remote accident land on his razzles*.
The bevvies if carbonated (beer) don't quite work out the same in zero G either. :(
When I think about the role of rising hot air (draught or convection?) in terrestrial fires, its not particularly clear to me how a fire in zero G would behave - I cannot see how hot gaseous combustion products and heated air can 'rise.' Just expands around the combustion site and removed by any external air flow?
Fire fighting would probably differ too. If the crew had ready access to a personal air supply then flooding a burning compartment with nitrogen I imagine could be effective.
I suppose the last mission to the ISS could run the real thing just as they leave.
* had to look it up a UK pecularity it seems Razzle
"When I think about the role of rising hot air (draught or convection?) in terrestrial fires, its not particularly clear to me how a fire in zero G would behave - I cannot see how hot gaseous combustion products and heated air can 'rise.' Just expands around the combustion site and removed by any external air flow?"
Small, single-point-source fires such as a candle, match etc burn with a circular flame in zero gravity, and extinguish quickly due to consuming the available oxygen. All fires need 3 things; fuel, oxidiser and a heat source - so removing one stops the fire.
With larger fires, the same thing should happen in theory (the fire consumes the immediately available oxygen and burns out), BUT larger fires end up changing the material density of the air; which creates areas of lower and higher pressure, which creates a form of turbulence. This can (and does, as the experiments show) have the effect of bringing more oxygenated air into the area of the fire such that it can become self-sustaining. And that is very, very dangerous.
as counter-intuitive as this may sound, rather than flooding the compartment with Nitrogen (which is already notoriously non-reactive in large concentrations here on earth), I'd go for something like Carbon Monoxide. Sure it's really bad if it gets out when you don't want it to, but it does bind the remaining oxygen in the area, and as far as I'm aware, they already have carbon dioxide scrubbers to assist in keeping O2 levels in the healthy range up there.
There's probably a thousand reasons why it's a bad idea to keep compressed cannisters of carbon monoxide handy on an orbital structure, but at least the science around it is exceptionally well known.
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