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Ecliptic orbit: A non-inclined orbit with respect to the ecliptic. Equatorial orbit: A non-inclined orbit with respect to the equator. Near equatorial orbit: An orbit whose inclination with respect to the equatorial plane is nearly zero. This orbit allows for rapid revisit times (for a single orbiting spacecraft) of near equatorial ground sites.
Getting there requires a geostationary transfer orbit with an apogee directly above the equator. Unless the launch site itself is quite close to the equator, it requires an impractically large amount of fuel to launch a spacecraft directly into such an orbit. Instead, the craft is placed with an upper stage in an inclined parking orbit.
A non-inclined orbit is an orbit coplanar with a plane of reference.The orbital inclination is 0° for prograde orbits, and π (180°) for retrograde ones. [citation needed]If the plane of reference is a massive spheroid body's equatorial plane, these orbits are called equatorial, and the non-inclined orbit is merely a special case of the near-equatorial orbit.
For rockets and space vehicles, propellants usually take up 2/3 or more of their total mass. Large upper-stage rocket engines generally use a cryogenic fuel like liquid hydrogen and liquid oxygen (LOX) as an oxidizer because of the large specific impulse possible, but must carefully consider a problem called "boil off," or the evaporation of the cryogenic propellant.
The 70-foot-long (21 m), 17-inch-diameter (430 mm) liquid oxygen feedline runs externally along the right side of the liquid hydrogen tank up and into the intertank. Two 5-inch (130 mm) diameter re-pressurization lines run beside it. One supplies hydrogen gas to the liquid hydrogen tank and the other supplies oxygen gas to the liquid oxygen tank.
In this case, non-inclined orbits are called equatorial. [2] For a heliocentric orbit, the ecliptic or invariable plane. In this case, non-inclined orbits are called ecliptic. [2] For an orbit outside the Solar System, the plane through the primary perpendicular to a line through the observer and the primary (called the plane of the sky). [3]
The remaining nitrogen is, in part, used as propellant for a nuclear-powered magnetohydrodynamic electromagnetic plasma thruster, which maintains the orbit at about 120 km, or a solar powered thruster (and collection system) for altitudes above 150 km (as stated in the original 1959 JBIS article, p119) compensating for atmospheric drag. [2]
For example, there are five of these points in the Sun-Earth system, five in the Earth-Moon system, and so on. Spacecraft may orbit around these points with a minimum of propellant required for station-keeping purposes. Two orbits that have been used for such purposes include halo and Lissajous orbits. [5]