Orbital spaceflight

An orbital spaceflight (or orbital flight) is a spaceflight in which a spacecraft is placed on a trajectory where it could remain in space for at least one orbit. To do this around the Earth, it must be on a free trajectory which has an altitude at perigee (altitude at closest approach) above 100 kilometers (62 mi) (this is, by at least one convention, the boundary of space). To remain in orbit at this altitude requires an orbital speed of ~7.8 km/s. Orbital speed is slower for higher orbits, but attaining them requires higher delta-v.

The expression "orbital spaceflight" is mostly used to distinguish from sub-orbital spaceflights, which are flights where apogee of a spacecraft reaches space but perigee is too low.

Orbital launch

Orbital spaceflight from Earth has only been achieved by launch vehicles that use rocket engines for propulsion. To reach orbit, the rocket must impart to the payload a delta-v of about 9.3–10 km/s. This figure is mainly (~7.8 km/s) for horizontal acceleration needed to reach orbital speed, but allows for atmospheric drag (approximately 300 m/s with the ballistic coefficient of a 20 m long dense fueled vehicle), gravity losses (depending on burn time and details of the trajectory and launch vehicle), and gaining altitude.

Spaceflight

Spaceflight (also written space flight) is ballistic flight into or through outer space. Spaceflight can occur with spacecraft with or without humans on board. Examples of human spaceflight include the U.S. Apollo Moon landing and Space Shuttle programs and the Russian Soyuz program, as well as the ongoing International Space Station. Examples of unmanned spaceflight include space probes that leave Earth orbit, as well as satellites in orbit around Earth, such as communications satellites. These operate either by telerobotic control or are fully autonomous.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other Earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft—both when unpropelled and when under propulsion—is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

John Glenn

John Herschel Glenn, Jr. (born July 18, 1921), (Col, USMC, Ret.), is a former Marine Corps aviator, engineer, astronaut, and United States senator. He was selected as one of the "Mercury Seven" group of military test pilots selected in 1959 by NASA to become America's first astronauts and fly the Project Mercury spacecraft. On February 20, 1962, Glenn flew the Friendship 7 mission and became the first American to orbit the Earth and the fifth person in space, after cosmonauts Yuri Gagarin and Gherman Titov and the sub-orbital flights of Mercury astronauts Alan Shepard and Gus Grissom. Glenn is the earliest-born American to go to orbit, and the second earliest-born man overall after Soviet cosmonaut Georgy Beregovoy. Glenn received the Congressional Space Medal of Honor in 1978, and was inducted into the U.S. Astronaut Hall of Fame in 1990. With the death of Scott Carpenter on October 10, 2013, Glenn became the last surviving member of the Mercury Seven.

Glenn resigned from NASA on January 16, 1964, and the next day announced plans to run for a U.S. Senate seat from Ohio. But injury from a bathtub concussion caused him to withdraw from the race in March. He retired from the Marine Corps on January 1, 1965. A member of the Democratic Party, he finally won election to the Senate in 1974 and served through January 3, 1999. With the death of Edward Brooke on January 3, 2015, Glenn became the oldest living former United States Senator.

Orbital mechanics

Orbital mechanics or astrodynamics is the application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft. The motion of these objects is usually calculated from Newton's laws of motion and Newton's law of universal gravitation. It is a core discipline within space mission design and control. Celestial mechanics treats more broadly the orbital dynamics of systems under the influence of gravity, including both spacecraft and natural astronomical bodies such as star systems, planets, moons, and comets. Orbital mechanics focuses on spacecraft trajectories, including orbital maneuvers, orbit plane changes, and interplanetary transfers, and is used by mission planners to predict the results of propulsive maneuvers. General relativity is a more exact theory than Newton's laws for calculating orbits, and is sometimes necessary for greater accuracy or in high-gravity situations (such as orbits close to the Sun).

Mercury-Atlas 6

Mercury-Atlas 6 (MA-6) was the third human spaceflight for the U.S. and part of Project Mercury. Conducted by NASA on February 20, 1962, the mission was piloted by astronaut John Glenn, who performed three orbits of the Earth, making him the first U.S. astronaut to orbit the Earth.

The Mercury spacecraft, named Friendship 7, was carried to orbit by an Atlas LV-3B launch vehicle lifting off from Launch Complex 14 at Cape Canaveral, Florida. After four hours and 56 minutes in flight the spacecraft re-entered the Earth's atmosphere, splashed down in the Atlantic Ocean and was safely taken aboard the USS Noa.

The event was named an IEEE Milestone in 2011.

Crew

Backup crew

Preparation

After the successful completion of the Mercury 5 flight that carried Enos, a chimpanzee, in late November 1961, a press conference was held in early December. Reporters asked NASA's Robert Gilruth who would be the first U.S. astronaut in orbit, piloting Mercury 6. He then announced the team members for the next two Mercury missions. John H. Glenn was selected as prime pilot for the first mission (Mercury 6), with M. Scott Carpenter as his backup. Donald K. Slayton and Walter M. Schirra were pilot and backup, respectively, for the second mission, Mercury 7.