Gate Orbit

Gate orbits are optimal circular departure orbits for transfer from one planet to another. At certain specific orbits around a cosmic body, the additional delta-v required to go from orbital velocity to hyperbolic trajectory for an interplanetary transfer, is minimal. Gate orbits can therefore be very useful for minimising the delta-v budget for an interplanetary trip.


For example, the required delta-v for a Hohmann transfer orbit from the Earth to Mars (considering Earth at 1 AU and Mars at 1.52 AU) is 2.94 km/s. To reach 2.94 km/s at infinity from a low Earth orbit at, say 200 km altitude, requires a 3.61 km/s burn. If the vehicle were to leave the Earth's attraction from the 92,000 km high Mars gate orbit instead, required delta-v would be only 2.08 km/s. At higher still orbits the required delta-v rises again. For example, at 150,000 km, required delta-v is now 2.17 km/s.

Reducing the delta-v from 3.61 to 2.08 km/s can reduce the total mass of the vehicle by as much as 38%, or increase the payload by 62%!

The radius of a given gate orbit can be calculated using the following equation:

where:

  • is the distance between the orbiting body and the central body, in km
  • is the standard gravitational parameter, in km3s−2
  • is the required velocity at infinity, in km·s−1. Remember is also known as

Famous quotes containing the words gate and/or orbit:

    You, mistress,
    That have the office opposite to Saint Peter,
    And keeps the gate of hell!
    William Shakespeare (1564–1616)

    The human spirit is itself the most wonderful fairy tale that can possibly be. What a magnificent world lies enclosed within our bosoms! No solar orbit hems it in, the inexhaustible wealth of the total visible creation is outweighed by its riches!
    —E.T.A.W. (Ernst Theodor Amadeus Wilhelm)