The Delta-P is an American

rocket A rocket (from , and so named for its shape) is a vehicle that uses jet propulsion to accelerate without using any surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely ...

stage Stage, stages, or staging may refer to: Arts and media Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly Brit ...

, developed by McDonnell Douglas and TRW, first used on November 10, 1972 as the second stage for the Delta 1000 series. It continued to serve as the second stage for subsequent

Delta 2000 The Delta 2000 series was an American expendable launch system which was used to conduct forty-four orbital launches between 1974 and 1981. It was a member of the Delta family of rockets, sometimes called Thorad Delta. Several variants existed, ...

and

Delta 3000 The Delta 3000 series was an American expendable launch system which was used to conduct 38 orbital launches between 1975 and 1989. It was a member of the Delta family of rockets. Several variants existed, which were differentiated by a four ...

flights for 17 years, with its last usage on February 8, 1988. It is propelled by a single TRW

TR-201 The TR-201 or TR201 is a hypergolic pressure-fed rocket engine used to propel the upper stage of the Delta (rocket family), Delta rocket, referred to as Delta-P, from 1972 to 1988. The rocket engine uses Aerozine 50 as fuel, and dinitrogen tetrox ...

rocket engine, fueled by

Aerozine 50 __NOTOC__ Aerozine 50 is a 50:50 mix by weight of hydrazine and unsymmetrical dimethylhydrazine (UDMH), developed in the late 1950s by Aerojet General Corporation as a storable, high-energy, hypergolic fuel for the Titan II ICBM rocket engines ...

and

dinitrogen tetroxide Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russian rocket engineers) as amyl, is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium ...

, which are

hypergolic A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. The ...

. The Delta-P traces its heritage to the

Apollo Apollo is one of the Twelve Olympians, Olympian deities in Ancient Greek religion, ancient Greek and Ancient Roman religion, Roman religion and Greek mythology, Greek and Roman mythology. Apollo has been recognized as a god of archery, mu ...

Lunar Module The Apollo Lunar Module (LM ), originally designated the Lunar Excursion Module (LEM), was the lunar lander spacecraft that was flown between lunar orbit and the Moon's surface during the United States' Apollo program. It was the first crewed s ...

's Descent Propulsion System. The TR-201 engine is the Descent Propulsion System modified to be a fixed thrust engine. The Descent Propulsion System was first fired in flight during the

Apollo 5 Apollo 5 (launched January 22, 1968), also known as AS-204, was the uncrewed first flight of the Apollo Lunar Module (LM) that would later carry astronauts to the surface of the Moon. The Saturn IB rocket bearing the LM lifted off from ...

mission, in a

low Earth orbit A low Earth orbit (LEO) is an geocentric orbit, orbit around Earth with a orbital period, period of 128 minutes or less (making at least 11.25 orbits per day) and an orbital eccentricity, eccentricity less than 0.25. Most of the artificial object ...

test on January 22, 1968. As the supply of these surplus Apollo engines was depleted, the Douglas/Aerojet Delta-K upper stage was introduced in the

program. The Delta-K was then exclusively used on the second stage for the Delta 4000, Delta 5000, and subsequent

Delta II Delta II was an expendable launch system, originally designed and built by McDonnell Douglas, and sometimes known as the Thorad Delta 1. Delta II was part of the Delta rocket family, derived directly from the Delta 3000, and entered service in ...

References

* Rocket stages {{rocket-stub