mechanics Module
Interactive Simulation Screen
SYS_OKLesson Directive // Orbits & TrajectoriesREF_CORE
Orbital Transfers
Hover over a variable in the formula above, or see glossary below:
Semi-major Axis
Meters or Kilometers
Initial Orbit Radius
Meters or Kilometers
Target Orbit Radius
Meters or Kilometers
To move from one orbit to another, a spacecraft must change its velocity (ΔV). A Hohmann transfer is the most fuel-efficient way to transfer between two circular, coplanar orbits.
INSIGHT: Transferring orbits requires exactly two engine burns.
The Transfer Ellipse
The first burn puts the spacecraft into an elliptical transfer orbit. The lowest point (periapsis) is at the original orbit, and the highest point (apoapsis) touches the target orbit.
INSIGHT: The semi-major axis (a) of this ellipse is the average of the two orbital radii.
Circularizing
When the spacecraft reaches the target altitude, it is moving too slowly to stay there. A second burn is required to circularize the orbit at the new altitude.
INSIGHT: Without the second burn, the spacecraft would fall back to its original orbit.