Spaceflight Simulator Wiki

This is the master list for equations!

Δ v

Delta v.svg


  • M t is total mass.
  • M d is total mass minus fuel mass.
  • "In" is a natural logarithm.

See the Δ v page for a comprehensive explanation of Δ v.

Rocket Efficiency 

According to Stef:

Top to Bottom



  • E_r is Efficiency of the rocket, and
  • M_n < is Mass in tonnes of the succeeding stages.

Bottom to Top

EfficiencyBottomTop.svg, which simplifies to:


Exhaust Velocity of Propellant

VelocityExhaust.svg, where

is the exhaust velocity of your propellant, and

is the standard gravity, which on Earth  is: 

Thrust to Weight

TWR.svg, where

is force of thrust in kilonewtons (kN) and

is your rocket's mass in metric tons (t).

is the force of gravity. For example, on Earth , it is 9.8 m / s 2 .

If the TWR is greater than or equal to 1 your rocket will lift off the ground. 

Average ISP

AvgISP.svg, where

is the sum of all the forces, and

is the fuel consumption rate in kg / s.

Average ISP can also be calculated from each engine:

ISP.svg, where

is the force in kilonewtons of the n th engine, including duplicates, and

is the ISP of the n th engine.

Fuel Consumption Rate

The same fuel flow rate.

Fuel Rate.svg

Burn Time

Burn Time.svg

Mass for that Time

Mass for burn time.svg

Suicide burn

Suicide Burn.svg

Orbital Velocity

Orbital Velocity.svg

Orbital Period

Orbital Period.svg

Kepler's Third Law of Planetary Motion

SFS K3L.svg

SOI Radius

SOI Radius.png

Max Payload 

Max Payload.png

R = Required Δ v for Mission

X = Max Payload in tonnes



E = Eccentricity

rmax = Apoapsis

rmin = Periapsis

Please allow a margin of error of 10% as well as user errors.