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Satellite Power Fuel Requirements Estimator

The Satellite Power Fuel Requirements Estimator estimates propellant mass for a maneuver while explicitly including the mass of the satellite power subsystem in the spacecraft starting mass. It uses the ideal rocket equation, making it useful for early mass trades where changes in arrays, batteries, power electronics, or supporting structure alter the mass that must be accelerated.

The result shows how much propellant is associated with the entered delta-v and specific impulse. It can help compare power-subsystem mass options, but it does not model tank residuals, pressurant, finite-burn gravity losses, attitude-control consumption, or mission-specific reserve policy.

Calculator inputs

kg
kg
m/s
s
%
Result
—
Estimated propellant requirement
Mass before propellant reserve—
Ideal maneuver propellant—
Reserve allowance—

1. Enter spacecraft dry mass
Use dry mass excluding the power subsystem so its contribution can be shown separately.

2. Add power-subsystem mass
Include arrays, batteries, regulators, deployment hardware, and other mass you want associated with the power system.

3. Enter maneuver delta-v
Use the total delta-v allocated to the maneuver or mission segment being estimated.

4. Set specific impulse
Enter the propulsion-system Isp for the maneuver.

5. Add reserve
Apply the desired percentage reserve to the ideal propellant estimate.

6. Review propellant mass
Use the result for preliminary mass budgeting and follow with a mission-specific propulsion analysis.

Mass ratio = exp(delta-v / (g0 × Isp))
Ideal propellant = dry mass with power subsystem × (mass ratio − 1)
Propellant with reserve = ideal propellant × (1 + reserve)
g0 = 9.80665 m/s²

This form solves for propellant added to a known dry spacecraft mass for the specified ideal delta-v. It assumes constant specific impulse and uses the ideal rocket equation; real mission budgets often include additional losses, trapped propellant, disposal maneuvers, attitude control, and operational reserves.

What the result means

The result is the ideal rocket-equation propellant mass for the stated maneuver, increased by the reserve percentage you entered.

Use a detailed propulsion and mission delta-v budget for flight design and final tank sizing.

Given

  • Dry mass excluding power = 900 kg
  • Power subsystem = 180 kg
  • Delta-v = 120 m/s
  • Isp = 220 s
  • Reserve = 8%

Calculation
Dry mass with power = 1,080 kg. Mass ratio = exp(120/(9.80665×220)) = 1.0572. Ideal propellant = 1,080×(1.0572−1) = 61.8 kg. With reserve ≈ 61.8×1.08 = 66.7 kg.

Result
Estimated propellant ≈ 66.7 kg.

Increasing power-subsystem mass raises the propellant required to achieve the same delta-v and Isp.

Why is power-subsystem mass entered separately?

It makes the propulsion impact of a heavier or lighter power design visible. The rocket equation responds to the total dry mass that must be accelerated.

Is this the same as launch vehicle propellant sizing?

No. This calculator is intended for spacecraft maneuver propellant and uses a single effective specific impulse. Launch ascent requires staged, trajectory-dependent modeling.

What specific impulse should I use?

Use the value appropriate to the propulsion system and operating mode for the maneuver being budgeted. Do not mix values from a different thruster type simply because they are higher.

Does the reserve percentage cover all mission contingencies?

Not necessarily. Programs may maintain separate allocations for statistical dispersion, attitude control, collision avoidance, disposal, trapped propellant, and unusable residuals.

Why does a small delta-v still require propellant?

Any positive ideal delta-v requires a mass ratio above one. For small delta-v, the resulting propellant fraction is small but not zero.