Kerbal Delta V Planning
A Kerbal mission succeeds when each stage has enough velocity change. Delta v is the budget that moves a craft from pad to orbit, from orbit to transfer, and from transfer to landing. This calculator helps you compare stage mass, fuel mass, engine efficiency, thrust, atmosphere, losses, and reserve margin in one place.
Why Stage Order Matters
In a stacked rocket, the lower stage must push everything above it. That includes upper stages, payload, fuel, and engines. After the lower stage burns out, its dry mass is normally dropped. The next stage starts with less mass, so the same engine efficiency can produce more useful delta v. For that reason, small mass changes near the top can affect every lower stage.
Atmosphere And Engine Efficiency
KSP engines have vacuum and sea level specific impulse values. A launch stage on Kerbin works through dense air first, then thinner air. The calculator blends both values with the selected pressure percentage. Use sea level pressure for pad checks. Use zero pressure for vacuum stages, transfer stages, and orbital maneuvers.
Thrust, TWR, And Control
Delta v alone does not prove a rocket will lift. Thrust to weight ratio shows whether the stage can accelerate against local gravity. A Kerbin launch stage usually needs a TWR above one. Higher values climb faster, but they may waste energy through drag and steering losses. Upper stages can use lower TWR because they already fly in space.
Losses And Reserve Margin
Real KSP flights lose velocity to gravity, drag, steering, and imperfect piloting. The loss field reduces each stage estimate. The reserve field keeps extra delta v unused for corrections. A safe mission should have a positive final margin after both adjustments. Use larger reserves for landings, rescue missions, docking practice, and unfamiliar planets.
Using The Output
The result shows stage delta v, adjusted delta v, mass ratio, effective impulse, thrust, and TWR. Compare the total usable delta v with your mission target. Export the values when testing several designs. Small changes in payload, fuel, staging, or atmosphere can reveal a better rocket before launch. Repeat the check again after moving parts between stages, because staging balance often changes the entire vehicle budget quickly.