NASA Flame Extinguishment - 2 (FLEX-2) experiment: Video

The Flame Extinguishment - 2 (FLEX-2) experiment is the second experiment to fly on the ISS which uses small droplets of fuel to study the special spherical characteristics of burning fuel droplets in space.

The FLEX-2 experiment studies how quickly fuel burns, the conditions required for soot to form, and how mixtures of fuels evaporate before burning.

Understanding these processes could lead to the production of a safer spacecraft as well as increased fuel efficiency for engines using liquid fuel on Earth.

Earth Applications
Watching fuel burn in a perfect sphere provides a unique view of fire that would be impossible to recreate on Earth.

Better knowledge of fire’s dynamics could lead to improved fuels for vehicles and aircraft, including efficient, environmentally friendly mixtures of chemicals that burn well together and produce less soot.

Soot results from the incomplete burning of a hydrocarbon, and it is harmful to human and environmental health.

The FLEX-2 experiment provides a unique view on soot formation that would be impossible under the influence of Earth’s gravity.

Space Applications
The FLEX-2 experiment measures soot buildup, flame heat and the burning rates of various types of fuels and fuel mixtures.

Understanding how fuels burn in microgravity could improve the efficiency of fuel mixtures used for interplanetary missions by reducing cost and weight.

It could also lead to improved safety measures for manned spacecraft.

Conditions for this test:
Test conducted with 50/50 fuel mixture of iso-octane and heptane in a standard air environment (21% oxygen and 79% nitrogen at 1 atm).

Burn with 3-mm droplet experienced flame oscillations, which appear as a hole in the flame shell that repeatedly opens and closes.

These oscillations create asymmetries in the flame, resulting in a force imbalance on the droplet.