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>> You never want to hear about a fire in space,
but that's exactly what had to happen for this experiment.
The FLEX-2 experiment burned fuel droplets
to see how they react without gravity.
Now this information could lead to better ways
of extinguishing flames in space as well as lead
to environmentally friendly fuels here on Earth.
>> My experiment is a droplet combustion experiment.
We burned fuel droplets in microgravity
to understand how liquid fuels burn;
so that we can use them efficiently and also cleanly
by understanding how the chemistry works.
And it has got another application,
which is fire safety in space.
If you burn these things in different environments,
reducing the oxygen concentration slowly,
and then finding out what is the minimum oxygen concentrations
below which is cannot burn anymore,
so that enhances the fire safety in microgravity environment.
Also we used different diluents in the ambient.
So, for example, on Earth you have oxygen and nitrogen.
But we can change it into oxygen
and carbon dioxide, oxygen and helium.
These inert diluents, they change the behavior
of how these things burn.
For example, in space station now they use carbon dioxide
as a fire extinguisher.
So is it the most efficient inert that we can use?
So if we try different inerts like helium, carbon dioxide,
and sometimes also xenon.
So this tells us what is the effective fire suppressant
in space.
So this experiment has got both practical applications looking
at how liquid fuels burn, also fire safety in microgravity.
So these are the main applications of my experiments.
It has benefits, you know, if you use a lot
of liquid fuels in, you know, transportation
and power generations and so forth.
So the objective here is how to use it more efficiently.
So these liquid fuels, they have a very complex
chemical kinetics.
So by looking at spherically symmetric burning
in microgravity,
we can understand the chemistry much better.
That means we can use fuels like gas, diesel,
aviation fuel more efficiently
at the same time reducing the pollution formation.
For example, one of the things that we discovered
in the FLEX experiments is the so-called cool flame combustion.
What happens there is the hot flame goes out,
under the drop it continues to burn at a very vigorous rate,
but without any visible flame?
And it just partially oxidizes the liquid fuel
and it extinguishes at some point.
This is called low temperature combustion
or cool flame combustion as we call it.
And this has got a lot of important implications
for Earth applications.
For example, the new internal combustion engines
that are coming up are being developed.
One, for example, its CCI engine,
this homogeneous charge compression ignition engine,
which involves low temperature chemistry.
So the FLEX results will have important applications
in that area for example.
And also low temperature chemistry it reduces knocks
formation and soot formation and so forth.
So this has got practical applications in the form
of using the good fuels in the efficient and clean way.
And the space applications for this is also very critical
because from the point of fire safety.
So if you have a fire fighting strategy
in a microgravity environment or the spacecraft environment,
so if you think once the hot flame is gone,
then you can't think that the fire is extinguished.
What is happening it's almost like smoldering combustion
on Earth like if you put a piece of log in the fireplace
and the flame goes out, but it can still smolder
and product toxic gases just like that.
This is the first time anybody has observed this.
The hot flame goes out, and there's no visible flame,
and still the liquid fuel continues
to burn partially oxidizing this fuels spewing
out combustible mixtures.
So it is very important to know that so that in principle,
at least we have demonstrated that, after hot flame,
the cool flame can be a fire hazard because it can reignite
and then bring back the hot flame.
So that is a very important space application.
And also we have looked at the suppressant effectiveness.
Is it CO2 is better?
Or helium is better?
Or some other inert is better?
So it has got both Earth applications as well
as fire safety applications in space.
>> And that will do it for us here
at the Payload Operations Integration Center
in Huntsville.
Now back to you at Mission Control in Houston.
[ Silence ]