The Delta 4000 series was an American

expendable launch system An expendable launch system (or expendable launch vehicle/ELV) is a launch vehicle that can be launched only once, after which its components are either destroyed during reentry or discarded in space. ELVs typically consist of several rocket sta ...

which was used to conduct two

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 a p ...

al launches in 1989 and 1990. 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. Although several variants were put forward, only the Delta 4925 was launched. The designations used a four digit numerical code to store information on the configuration of the rocket. It was built from a combination of spare parts left over from earlier Delta rockets, which were being retired, and parts from the

Delta II Delta II was an expendable launch system, originally designed and built by McDonnell Douglas. Delta II was part of the Delta rocket family and entered service in 1989. Delta II vehicles included the Delta 6000, and the two later Delta 7000 va ...

6000-series, which was just entering service. The first stage was the MB-3-III powered

Extended Long Tank Thor Extension, extend or extended may refer to: Mathematics Logic or set theory * Axiom of extensionality * Extensible cardinal * Extension (model theory) * Extension (predicate logic), the set of tuples of values that satisfy the predicate * E ...

, previously flown on the 1000-series. Nine Castor-4A solid rocket boosters were attached to increase thrust at lift-off, replacing the less powerful

Castor-4 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 ...

boosters used on the 3000 series. The

Delta-K The Delta-K was an American rocket stage, developed by McDonnell Douglas and Aerojet. It was first used on 27 August 1989 as the second stage for the Delta 4000 series. It continued to serve as the second stage for subsequent variants of the ...

was used as a second stage. A

Star-48B 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 ...

PAM-D The Payload Assist Module (PAM) is a modular upper stage designed and built by McDonnell Douglas (now Boeing), using Thiokol Star-series solid propellant rocket motors. The PAM was used with the Space Shuttle, Delta, and Titan launchers and carri ...

was used as a third stage, to boost payloads into

geosynchronous transfer orbit A geosynchronous transfer orbit or geostationary transfer orbit (GTO) is a type of geocentric orbit. Satellites that are destined for geosynchronous (GSO) or geostationary orbit (GEO) are (almost) always put into a GTO as an intermediate step f ...

. Both Delta 4000 launches occurred from Launch Complex 17B at

Cape Canaveral , image = cape canaveral.jpg , image_size = 300 , caption = View of Cape Canaveral from space in 1991 , map = Florida#USA , map_width = 300 , type =Cape , map_caption = Location in Florida , location ...

. The first launched Marco Polo 1 for

BSkyB Sky UK Limited is a British broadcaster and telecommunications company that provides television and broadband Internet services, fixed line and mobile telephone services to consumers and businesses in the United Kingdom. It is a subsidiary of ...

, and the second launched INSAT 1D for the

Indian Space Research Organisation The Indian Space Research Organisation (ISRO; ) is the national space agency of India, headquartered in Bengaluru. It operates under the Department of Space (DOS) which is directly overseen by the Prime Minister of India, while the Chairman ...

. Both were successful.

References

{{Thor and Delta rockets Delta (rocket family)