Forge · Mission Analysis Tool

LEO Survivability Estimator

If propulsion fails mid-mission, will a small satellite hold a usable low-Earth orbit long enough to finish — or decay and reenter? Enter rough mass and altitude ranges; this maps the survivability window and ranks the parameters that matter most.

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Nominal coast lifetime
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Time still needed after failure
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Min. safe altitude (nominal sat)
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Ballistic coefficient

Survivability window

Green = the orbit lasts long enough to finish the mission after a mid-mission failure; red = it decays first. Drag area held at the nominal value.

Survives (margin ≥ 2×) Survives (tight) Marginal (≈ break-even) Fails (decays) Fails badly (< ½ needed) Break-even contour

Coast lifetime vs. altitude

Band spans your mass range (heavier = longer life). The dashed line is the time still needed after the failure; where the band crosses it is your minimum safe altitude.

What matters most

Each bar shows how much the coast lifetime swings as one input moves across its plausible range while the others stay at nominal. Longer bar = more leverage over survival.

    Model & assumptions
    • Near-circular orbit, drag-only secular decay: da/dt = -(CdA/m)·ρ(h)·√(μa), integrated to a ~120 km reentry floor.
    • Atmosphere: piecewise-exponential (US Standard Atmosphere / Vallado), scaled by the solar-activity multiplier — the single biggest real-world swing in LEO lifetime.
    • "Effective drag area" is the time-averaged ram-facing area; a tumbling or sun-tracking sat varies this. Cd ≈ 2.2 is typical free-molecular flow.
    • Screening-grade, order-of-magnitude estimate — not a high-fidelity reentry predictor. No J2/lunar-solar perturbations, no eccentricity growth, no attitude model.