Expert Reviewed by: David Chen, Aerospace Engineering Specialist
Master your orbital maneuvers with our precise KSP Delta-V Calculator. Whether you’re landing on Mun or embarking on an interplanetary voyage to Duna, understanding your vessel’s total change in velocity (Δv) is the key to mission success in Kerbal Space Program.
KSP Delta-V Calculator
KSP Delta-V Calculator Formula
$\Delta v = I_{sp} \cdot g_0 \cdot \ln\left(\frac{m_{wet}}{m_{dry}}\right)$
Formula Source: KSP Official Wiki | NASA Propulsion Basics
Variables Explained
- Isp (Specific Impulse): Represents engine efficiency (measured in seconds). Higher values mean more thrust per unit of fuel.
- Wet Mass: The total mass of your rocket stage including all fuel and oxidizer.
- Dry Mass: The mass of the stage once all usable fuel has been exhausted.
- g0 (Standard Gravity): In KSP, this is constant at 9.80665 m/s².
What is a KSP Delta-V Calculator?
A KSP Delta-V Calculator is an essential tool for Kerbal Space Program players to determine the “budget” of their spacecraft. Delta-V (Δv) represents the total change in velocity a ship can achieve. In spaceflight, we don’t measure distance in kilometers; we measure it in the velocity required to change orbits or reach new destinations.
Understanding your Δv allows you to compare your ship’s capabilities against a Delta-V Map. If the map says you need 3,400 m/s to reach Low Kerbin Orbit and your ship only has 3,000 m/s, you know you need more fuel or more efficient engines before leaving the VAB.
How to Calculate Delta-V (Example)
- Determine your engine’s Isp (e.g., 300s).
- Find your Wet Mass (e.g., 10 tons) and Dry Mass (e.g., 4 tons).
- Divide Wet Mass by Dry Mass (10 / 4 = 2.5).
- Take the Natural Log (ln) of that result (ln(2.5) ≈ 0.916).
- Multiply by Isp and 9.81 ($300 \cdot 9.81 \cdot 0.916 \approx 2,696 \text{ m/s}$).
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Frequently Asked Questions (FAQ)
What is the g0 value in KSP? KSP uses 9.80665 m/s² for gravity in the Delta-V formula, regardless of which planet you are currently orbiting.
Why is my in-game dV different? This calculator uses the vacuum Isp. Engines perform differently inside an atmosphere (like Kerbin’s surface) where air pressure reduces efficiency.
Does Delta-V change with gravity? No. Delta-V is a measure of potential velocity change. However, the Thrust-to-Weight Ratio (TWR) does change based on the local gravity of a planet.
Can I calculate multiple stages? Yes, but you must calculate them one at a time, using the mass of all subsequent stages as part of the “Dry Mass” for the current stage.