INFERNITYFLAME IN FREEFALL

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Attribute
Hardware groupMDCA group
Pillars
SuppressionPrevention
Fuel phaseLiquid
MaterialMethanol and heptane droplets
ShapeSingle spherical droplet on a support fiber
SizeInitial droplet diameter 2 to 5 mm
O2 concentration50%
Pressure14.7 psi
AirflowVaried / not specified
FacilityMulti-user Droplet Combustion Apparatus (MDCA) in the Combustion Integrated Rack (CIR)
Module / vehicleInternational Space Station
Sensors
  • High-speed cameras for droplet and flame imaging
  • Radiometers for flame radiation
  • Soot concentration and soot temperature diagnostics
  • Droplet deployment and ignition instrumentation
Variables tested
  • Oxygen mole fraction from 0.10 to 0.50
  • Suppressant type: carbon dioxide or helium
  • Diluent gas, primarily nitrogen with some helium tests
  • Pressure from 0.5 to 1.0 atm
  • Fuel type: methanol versus heptane
  • Initial droplet diameter from 2 to 5 mm
ObjectivesQuantify the suppressant effectiveness of inert gases in microgravity, find the most conservative limiting oxygen index for steady combustion, and validate droplet combustion and extinction models.
Key findings
  • Mapped flammability boundaries for liquid fuel combustion across oxygen, pressure and suppressant conditions.
  • Tested carbon dioxide and helium as suppressants from zero concentration up to the no-flame limit.
  • Observed droplets either burning to completion or extinguishing at a finite droplet radius.
  • Provided spatially and temporally resolved measurements of burning rate, extinction, radiation and soot for model validation.
Relevant environments
Spacecraft cabinSpace stationSpacesuit
SourceNASA PSI