Spaceflight Simulator Wiki

This is a list of terms used in both this Wiki and in real-life.


Term Definition
Apoapsis An object's furthest point from a body in an orbit
Periapsis An object's closest point from a body in an orbit
Aerobrake The act of slowing down a spacecraft via atmospheric friction
Drag Force acting opposite to any object's relative motion
Eccentricity How much an object's orbit deviates from a circle (0.0 = circular; Between 0.0 and 1.0 = Ellipse; 1.0 = Parabola; More than 1.0 = Hyperbola )
Gravity assist Entering a sphere of influence without orbiting to accelerate/decelerate and reduce fuel usage
Liftoff The first moment of a rocket's flight
Lithobrake Slow down and safely land a spacecraft by impacting into a celestial body
Oberth effect Burn at periapsis during repeated orbits to save Delta-v
Trajectory The path that an object follows
Thrust Reaction force described quantitatively by Newton's third law
Escape velocity Minimum speed for an object to escape from a body's Sphere of Influence
Suicide Burn Landing burn at 100% bhrust shortly before landing.
Prograde Burn in the direction of the orbit
Retrograde Burn in the opposite direction of the orbit.
Semi-major axis An imaginary line between an ellipse's centre and the furthest point from it on its perimeter
Revolution The time it takes for an object to complete a full orbit around another object.
Rotation period The time it takes for an object to rotate around its rotational axis until it reaches the same relative position to the surrounding objects as before.
Inclination The angle the rotational axis is shifted from the objects relative position to its surroundings.
Cosine decay The inefficiency caused by engines deviating from the direction of thrust, equal to 1 minus the cosine of the deviation.


Abbreviation Full Form
Delta-v (∆v) Change in velocity that can be made by the spacecraft
g Gravitational constant of Earth
ICBM Intercontinental Ballistic Missile.
LEO Low Earth Orbit
LES Launch Escape System
RCS Reaction Control System
SOI Sphere of Influence
SRB Solid Rocket Booster
SSTO Single Stage To Orbit
TWR Thrust to Weight Ratio
RTG Radioisotope Thermoelectric Generator
LRB Liquid Rocket Booster