The Delta M or Thor-Delta M was an American expendable launch system used for thirteen

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...

al launches between 1968 and 1971. It was a member of the

Delta Delta commonly refers to: * Delta (letter) (Δ or δ), a letter of the Greek alphabet * River delta, at a river mouth * D ( NATO phonetic alphabet: "Delta") * Delta Air Lines, US * Delta variant of SARS-CoV-2 that causes COVID-19 Delta may also ...

family of rockets. The Delta M had a three-stage configuration. The first stage was the Long Tank Thor, a stretched version of the

Thor Thor (; from non, Þórr ) is a prominent god in Germanic paganism. In Norse mythology, he is a hammer-wielding god associated with lightning, thunder, storms, sacred groves and trees, strength, the protection of humankind, hallowing, an ...

missile, previously flown on the

Delta L The Delta L, Thor-Delta L, or Thrust-Augmented Long Tank Thor-Delta was a US expendable launch system used to launch the Pioneer E and TETR satellites in 1969 (failed) and HEOS satellite in 1972. It was a member of the Delta family of rockets. T ...

. Three

Castor-2 The Castor family of solid-fuel rocket stages and boosters built by Thiokol (now Northrop Grumman) and used on a variety of launch vehicles. They were initially developed as the second-stage motor of the Scout rocket. The design was based on the ...

solid rocket boosters were attached to the first stage to increase thrust at lift-off. A Delta E was used as the second stage, and the third stage was a

Star-37D The Star is a family of US solid-propellant rocket motors originally developed by Thiokol and used by many space propulsion and launch vehicle stages. They are used almost exclusively as an upper stage, often as an apogee kick motor. Three Star 3 ...

solid rocket motor A solid-propellant rocket or solid rocket is a rocket with a rocket engine that uses solid propellants (fuel/oxidizer). The earliest rockets were solid-fuel rockets powered by gunpowder; they were used in warfare by the Arabs, Chinese, Persia ...

. On the final flight, six boosters were flown instead of three, in a configuration known as the Delta M6, or "Super Six." All thirteen launches were made from Launch Complex 17A at the

Cape Canaveral Air Force Station Cape Canaveral Space Force Station (CCSFS) is an installation of the United States Space Force's Space Launch Delta 45, located on Cape Canaveral in Brevard County, Florida. Headquartered at the nearby Patrick Space Force Base, the statio ...

(CCAFS). The first launch carrying Intelsat III F-1 on 18 September 1968, was a complete failure when the first stage began suffering abnormal pitch gyrations starting at T+20 seconds. The booster maintained a stable attitude until around T+100 seconds when it pitched over and began to break up from structural loads. As the Delta was also headed back towards land,

Range Safety Officer In the field of rocketry, range safety may be assured by a system which is intended to protect people and assets on both the rocket range and downrange in cases when a launch vehicle might endanger them. For a rocket deemed to be ''off course' ...

sent the destruct signal at T+108 seconds. It was bound for a Geostationary transfer orbit above the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

and be in operation in time to relay broadcasts of the next month's

1968 Summer Olympics The 1968 Summer Olympics ( es, Juegos Olímpicos de Verano de 1968), officially known as the Games of the XIX Olympiad ( es, Juegos de la XIX Olimpiada) and commonly known as Mexico 1968 ( es, México 1968), were an international multi-sport eve ...

Mexico City Mexico City ( es, link=no, Ciudad de México, ; abbr.: CDMX; Nahuatl: ''Altepetl Mexico'') is the capital city, capital and primate city, largest city of Mexico, and the List of North American cities by population, most populous city in North Amer ...

. The fifth launch on 25 July 1969, Intelsat III F-5 suffered a rupture of either the third stage casing or nozzle and ended up in an unusable orbit. Of the thirteen launches, twelve carried

geosynchronous A geosynchronous orbit (sometimes abbreviated GSO) is an Earth-centered orbit with an orbital period that matches Earth's rotation on its axis, 23 hours, 56 minutes, and 4 seconds (one sidereal day). The synchronization of rotation and orbital ...

communications satellites A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. C ...

. The thirteenth, which was the final flight and the only one in the Delta-M6 configuration, placed

Explorer 43 Explorer 43, also called as IMP-I and IMP-6, was a NASA satellite launched as part of Explorer program. Explorer 43 was launched on 13 March 1971 from Cape Canaveral Air Force Station (CCAFS) (restored to its old name of Cape Canaveral in 1974 ...

into a

highly elliptical orbit A highly elliptical orbit (HEO) is an elliptic orbit with high eccentricity, usually referring to one around Earth. Examples of inclined HEO orbits include Molniya orbits, named after the Molniya Soviet communication satellites which used them ...

References

Delta (rocket family) {{rocket-stub