Orbiters

Challenger (and the orbiters built after it) had fewer tiles in its Thermal Protection System than Columbia, though it still made heavy use of the white LRSI tiles on the cabin and main fuselage compared to the later orbiters.

Russia is contributing its Luna landers and Oryol crewed orbiters, while China is improving its Chang'e robotic spacecraft.

Later missions from the Viking orbiters, which first launched in 1975, revealed yet more details about how water flowed on the surface and carved valleys.

The spacecraft—comprised of two scientific orbiters—should reach Mercury in 2025, after swinging twice past Venus and six times past Mercury itself.

The X-37B — about one-fourth the length of NASA’s shuttle orbiters — uses electro-mechanical actuators, removing concerns about the limited useful of hydraulic control systems.

Despite extensive preparation, Earth's success rate at Mars sits at just 40 percent, including planetary flybys dating back to the early 1960s, as well as orbiters and landers.

The pair of orbiters will make a number of fly-bys of Earth, Venus and Mercury until December of 2025 when they'll enter orbit around the small planet and finally separate to study and map it in greater detail than ever before.

The transfer module will use both ion propulsion and chemical propulsion, in combination with gravity assist flybys at Earth, Venus and Mercury to bring the two science orbiters close enough to Mercury to be gravitationally captured into its orbit.

After the flight, Columbia spent 18 months at the Rockwell Palmdale facility beginning in January 1984, undergoing modifications that removed the Orbiter Flight Test hardware and bringing it up to similar specifications as those of its sister orbiters.

American Shuttle Orbiters docked with the ISS via PMA-2, attached to the forward port.

Both these antennae allowed for communication directly with the Earth, permitting Viking 1 to continue to work long after both orbiters had failed.

Columbia landing at Edwards Air Force Base following STS-28 Despite refinements to the orbiter's thermal protection system and other enhancements, Columbia would never weigh as little unloaded as the other orbiters in the fleet.

During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space.

Endeavour (OV-105) was built to replace Challenger (using structural spare parts originally intended for the other orbiters) and delivered in May 1991; it was first launched a year later.

Enterprise, which was used for atmospheric test flights but not for orbital flight, had many parts taken out for use on the other orbiters.

Fiberglass was used for the leading edge panels in place of the reinforced carbon–carbon ones of spaceflight-worthy orbiters.

Final status Out of the five fully functional shuttle orbiters built, three remain.

However, orbiters such as the Space Shuttle and many artificial satellites appear to move from west to east.

Most of this equipment was later incorporated into the other three orbiters during out-of-service major inspection and modification programs.

NASA maintains warehoused extensive catalogs of recovered pieces from the two destroyed orbiters.