Droplet Combustion Lab (2D): Microgravity Flame Simulator

Combustion Rack

Gravity 0.00 g

Ambient O₂ 21%

Droplet diameter 1.20 mm

Readouts

Standing by — press Ignite.

Droplet Ø

1.20 mm

Flame stand-off

— mm

Burn-rate K

— mm²/s

Burn time

0.0 s

How it works

Fiber-supported droplet combustion is a real ISS experiment family (FLEX, ACME) flown in the Combustion Integrated Rack. A liquid fuel droplet burns inside a diffusion flame whose size follows the classical d²-law, which is exactly linear in D² vs time — that's what the strip chart below the chamber view is plotting live:

D(t)² = D₀² − K·t
K = K₀ · ln(1 + B) · (1 + 1.7·√g)

D is droplet diameter, D₀ the initial diameter, K the burning-rate constant, B the Spalding transfer number (rises with ambient O₂), and the √g convection-gain term is a simplified stand-in for the natural-convection (Grashof-number) enhancement that only exists when buoyancy exists.

Gravity = 0 — no buoyancy, so fuel vapor and oxidizer meet purely by diffusion. The flame sits as a near-perfect blue sphere around the droplet, burns slower and cleaner (little to no soot).
Gravity → 1g — a buoyant plume rises off the flame, dragging in extra oxidizer and stretching the envelope into the familiar yellow, sooty teardrop seen on Earth. Convection raises K, so the same droplet burns faster.
Ambient O₂ — more oxidizer raises the transfer number B, driving both flame temperature and K up at any gravity level, while pulling the flame's stand-off ratio inward slightly.
The flame extinguishes when the droplet is fully consumed, or — in the low-g / low-O₂ / large-droplet corner — when radiative heat loss from the flame outpaces the (slow, diffusion-only) heat release, the radiative-extinction limit ISS crews study for spacecraft fire safety.

Real-world relevance: microgravity droplet-flame data feeds directly into spacecraft fire-safety standards and cleaner terrestrial diesel/spray-combustion models, since both are diffusion flames around a shrinking droplet.

Drag the chamber view to pan, scroll/pinch to zoom.

Diffusion flame Soot / convection plume

drag to pan · scroll to zoom