Delta-v (Δv) is the total change in velocity a spacecraft can achieve by expending all its propellant. It is the primary currency of orbital mechanics — every maneuver (launch, orbit insertion, transfer, landing) costs a certain Δv, and the rocket must carry enough propellant to cover the total budget.

What is the Tsiolkovsky rocket equation?

The Tsiolkovsky rocket equation is Δv = Isp × g₀ × ln(m₀ / m_f), where Isp is specific impulse (seconds), g₀ = 9.80665 m/s², m₀ is the initial (wet) mass, and m_f is the final (dry) mass after burning propellant. It describes how propellant consumption converts to velocity.

What is specific impulse (Isp)?

Specific impulse measures how efficiently an engine uses propellant. Higher Isp means more delta-v per kilogram of propellant. Typical values: cold gas ~50 s, monopropellant hydrazine ~220 s, kerosene/LOX (Merlin) ~311 s, LH₂/LOX (SSME) ~453 s, ion thruster ~1,000–10,000 s.

Why does multi-staging increase delta-v?

Each stage drops its empty structural mass before the next burn begins, so subsequent stages start with a much better mass ratio. Staging allows rockets to reach orbit that a single stage cannot achieve with the same total propellant load.

How accurate are the maneuver presets?

The presets use widely cited reference values (e.g., ~9,400 m/s to LEO including gravity and drag losses). They are useful for feasibility checks but real missions add margins for steering, winds, and trajectory shaping — typically 5–15% overhead.

Delta-V Calculator

Name: Delta-V Calculator
Availability: InStock
Author: Nham Vu

Compute the velocity change a rocket can achieve using the Tsiolkovsky equation, with multi-stage support and orbital maneuver presets.

Maneuver Preset

Total Delta-V Budget

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Tsiolkovsky Rocket Equation

Δv = I_sp × g₀ × ln(m_wet / m_dry)

Δv — velocity change (m/s)

I_sp — specific impulse (seconds); higher = more efficient engine

g₀ — standard gravity = 9.80665 m/s²

m_wet — initial mass including propellant (kg)

m_dry — final mass after burn (kg)

Common Engine Isp Values

Engine / Propellant	Isp (s)

Summary

Compute the velocity change a rocket can achieve using the Tsiolkovsky equation, with multi-stage support and orbital maneuver presets.

How it works

Enter the specific impulse (Isp) in seconds for a rocket stage — this measures engine efficiency.
Enter the wet mass (full, with propellant) and dry mass (empty, without propellant) in kilograms.
Click "Add Stage" to chain multiple stages; each stage result feeds into the total budget.
Select a maneuver preset to see the required delta-v for common missions (LEO, GTO, lunar transfer).
The tool applies Δv = Isp × 9.80665 × ln(wet / dry) for each stage and sums them.
Compare your total budget against the preset requirement to assess mission feasibility.

Use cases

Estimate the delta-v budget for a single-stage-to-orbit vehicle design.
Plan multi-stage rocket staging separation points for maximum efficiency.
Check whether a given propellant mass fraction reaches low Earth orbit.
Compare engine choices (kerosene vs. hydrogen vs. methalox) by Isp for a fixed mass ratio.
Verify a lunar transfer burn requirement against available propellant.
Teach or study orbital mechanics and the Tsiolkovsky rocket equation.
Quick feasibility check for CubeSat or small-sat propulsion budgets.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu