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The hardware consisted of a pressurized 50 cu ft (1,400 litres) tank insulated with 34 layers of insulation, a condenser, and a Gifford-McMahon (GM) cryocooler that has a cooling capacity of 15 to 17.5 watts (W). Liquid hydrogen was the test fluid. The test tank was installed into a vacuum chamber, simulating space vacuum. [55]
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.
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.
A concept to provide low Earth orbit (LEO) propellant depots that could be used as way-stations for other spacecraft to stop and refuel on the way to beyond-LEO missions has proposed that waste gaseous hydrogen—an inevitable byproduct of long-term liquid hydrogen storage in the radiative heat environment of space—would be usable as a monopropellant in a solar-thermal propulsion system.
Hydrogen has nearly 30% higher specific impulse (about 450 seconds vs. 350 seconds) than most dense fuels. Hydrogen is an excellent coolant. The gross mass of hydrogen stages is lower than dense-fuelled stages for the same payload. Hydrogen is environmentally friendly. However, hydrogen also has these disadvantages: [citation needed]
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.
Beginning at T+44 seconds, the pneumatic system responded by venting propellant to reduce pressure levels, but eventually, they exceeded the LH2 tank's structural strength. At T+54 seconds, the Centaur experienced total structural breakup and loss of telemetry, the LOX tank rupturing and producing an explosion as it mixed with the hydrogen cloud.
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]