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Telescope Resolution Fuel Requirements Estimator

The Telescope Resolution Fuel Requirements Estimator estimates spacecraft propellant needed to deliver a telescope payload through a specified maneuver delta-v. It makes telescope payload mass explicit alongside spacecraft bus mass, so early optical design choices can be translated into a first-order propulsion consequence.

The calculator uses the ideal rocket equation with a single specific impulse and an optional propellant reserve. It is useful for mission concept trades, not detailed trajectory or tank design. Launch-vehicle ascent, staging, boil-off, finite burns, attitude-control fuel, and mission-specific contingency policy require separate analysis.

Calculator inputs

kg
kg
m/s
s
%
Result
—
Estimated propellant requirement
Combined dry mass—
Ideal propellant—
Propellant / dry mass—

1. Enter spacecraft bus mass
Use dry bus mass before maneuver propellant is added.

2. Enter telescope payload mass
Include the telescope assembly and payload items that travel through the maneuver.

3. Enter allocated delta-v
Use the maneuver or mission-segment delta-v to be supported by this propellant budget.

4. Set propulsion Isp
Enter the effective specific impulse for the propulsion mode.

5. Add reserve
Apply a percentage reserve over the ideal rocket-equation propellant.

6. Review the mass impact
Use the result to compare telescope mass and propulsion trades during early mission design.

Dry mass = spacecraft bus mass + telescope payload mass
Mass ratio = exp(delta-v / (g0 × Isp))
Ideal propellant = dry mass × (mass ratio − 1)
Propellant with reserve = ideal propellant × (1 + reserve)

The model assumes a single burn-equivalent delta-v and constant specific impulse. It solves the ideal rocket equation around the entered dry mass and then adds a simple percentage reserve. Detailed mission design should distinguish individual burns, losses, residuals, pressurant, disposal, and attitude-control propellant.

What the result means

The result is the ideal spacecraft maneuver propellant associated with the entered bus and telescope dry mass, increased by the selected reserve.

It is suitable for concept-level mass trades, not detailed propulsion subsystem or trajectory design.

Given

  • Bus dry mass = 1,200 kg
  • Telescope payload = 650 kg
  • Delta-v = 350 m/s
  • Isp = 320 s
  • Reserve = 10%

Calculation
Dry mass = 1,850 kg. Mass ratio = exp(350/(9.80665×320)) = 1.1181. Ideal propellant ≈ 218.3 kg. With 10% reserve ≈ 240.1 kg.

Result
Estimated propellant ≈ 240.1 kg.

A heavier telescope increases the propellant required for the same spacecraft maneuver capability.

Does better telescope resolution always mean more propellant?

Not directly. Resolution can drive larger optics or supporting structures, which may increase payload mass; propellant increases only through the resulting spacecraft mass and delta-v requirement.

Can I combine multiple maneuvers into one delta-v input?

For an early ideal estimate, total allocated delta-v can be used with a representative Isp. If propulsion modes or mass events differ between burns, model them separately.

Why is launch vehicle fuel not included?

Launch ascent is a staged trajectory problem governed by the launch vehicle design. This tool addresses spacecraft maneuver propellant after the spacecraft dry mass is defined.

Should telescope propellant or consumables be included in payload mass?

Use dry payload mass for the mass that remains after the maneuver propellant is consumed. Other consumables should be treated consistently with the mission mass budget.

How should I interpret propellant reserve?

It is a simple percentage allowance above the ideal maneuver amount. Actual programs often manage reserves by maneuver category and confidence level rather than one universal percentage.