Propulsive Landing Burn Simulator

Falling — throttle up to slow down

Engines

Throttle 0%

Altitude

–

Velocity

–

Fuel remaining

–

Net G-force

–

Suicide-burn estimate at current thrust: – — the altitude below which you can no longer stop in time.

How it works

The booster falls under gravity while its engines fight back with thrust. Newton's second law along the vertical axis gives the acceleration every frame:

m·dv/dt = T(throttle) − m·g − ½ρCdA·v|v|
dm/dt = −T / (Isp·g₀)   (Tsiolkovsky mass flow)

Thrust T comes from however many engines are lit at the chosen throttle; each engine that burns also consumes propellant mass at a rate set by its specific impulse Isp — exactly like a real Merlin-class engine, more thrust drains the tanks faster. As fuel burns off, the ship gets lighter, so the same thrust decelerates it more and more, which is why real landing burns throttle down near the end.

Engines (1–3) — more engines means more available thrust (and a higher fuel burn rate at full throttle), letting you start the burn later but risking overshoot if you can't throttle down fast enough.
Throttle — your only real-time control; too little and gravity wins (crash), too much and you decelerate to a hover and run out of fuel before touchdown.
Air drag — toggles the ½ρCdA·v² aerodynamic term; it slightly slows the fall at high speed and disappears near the ground where it matters least.
Suicide-burn estimate — the theoretical latest safe ignition altitude, h = v²/(2a), where a is the deceleration your current throttle would produce. Ignite later than this and no amount of throttle saves you.

Real-world relevance: this is the actual physics behind SpaceX-style propulsive landings — the same rocket equation and thrust-to-weight tradeoff that let a first-stage booster reuse itself instead of burning up or being discarded.

Booster Engine plume Landing pad

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