Thor was a US space

launch vehicle A launch vehicle is typically a rocket-powered vehicle designed to carry a payload (a crewed spacecraft or satellites) from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multistage ...

derived from the

PGM-17 Thor The PGM-17A Thor was the first operative ballistic missile of the United States Air Force (USAF). It was named after the Thor, Norse god of thunder. It was deployed in the United Kingdom between 1959 and September 1963 as an intermediate-range b ...

intermediate-range ballistic missile An intermediate-range ballistic missile (IRBM) is a ballistic missile with a range (aeronautics), range between (), categorized between a medium-range ballistic missile (MRBM) and an intercontinental ballistic missile (ICBM). Classifying ball ...

. The Thor

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 ...

was the first member of the

Delta Delta commonly refers to: * Delta (letter) (Δ or δ), the fourth letter of the Greek alphabet * D (NATO phonetic alphabet: "Delta"), the fourth letter in the Latin alphabet * River delta, at a river mouth * Delta Air Lines, a major US carrier ...

rocket family of space launch vehicles. The last launch of a direct derivative of the Thor missile occurred in 2018 as the first stage of the final

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 ...

Thor-Able

Pioneer I on the Launch Pad - GPN-2002-000204

Thor was first used as a launch vehicle during the testing program of the warhead reentry vehicle for the Atlas missile. For these three tests a Thor core stage was topped by the Able second stage. Able used the Aerojet AJ-10-40 engine from the

Vanguard The vanguard (sometimes abbreviated to van and also called the advance guard) is the leading part of an advancing military formation. It has a number of functions, including seeking out the enemy and securing ground in advance of the main force. ...

second stage. The first such launch, 116, was lost on 23 April 1958 due to a turbopump failure in the main engine. The recovery of the reentry vehicles on the succeeding two attempts were not successful. Three

mice A mouse (: mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...

, one on each vehicle, died in these tests. The Able stage from the Atlas reentry vehicle tests was upgraded to become the Able I with a third stage consisting of an unguided Altair X-248 solid-fuel rocket motor. A Thor Able I was used in an attempt to place the 84 lb (38 kg) Pioneer 0 spacecraft into lunar orbit where it would take pictures of the lunar surface with a TV camera. The mission ended prematurely at 73.6 seconds after launch on 17 August 1958 due to a turbopump failure. On 7 August 1959, a Thor-Able was used to successfully launch Explorer 6, the first satellite to transmit pictures of Earth taken from orbit.

Ablestar

Ablestar was a

liquid-propellant rocket A liquid-propellant rocket or liquid rocket uses a rocket engine burning liquid rocket propellant, liquid propellants. (Alternate approaches use gaseous or Solid-propellant rocket , solid propellants.) Liquids are desirable propellants because th ...

stage burning hypergolic propellants fed from gas-pressurized propellant tanks. It was used as the

upper stage A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own Rocket engine, engines and Rocket propellant, propellant. A ''tandem'' or ''serial'' stage is mounted on top of anoth ...

, and provided improved performance. On 13 April 1960, a Thor-Ablestar launched Transit 1B, the first experimental satellite of what eventually became the

Global Navigation Satellite System A satellite navigation or satnav system is a system that uses satellites to provide autonomous geopositioning. A satellite navigation system with global coverage is termed global navigation satellite system (GNSS). , four global systems are op ...

. On 22 June 1960, a Thor-Ablestar launched the first

Galactic Radiation and Background Galactic Radiation and Background (GRAB) was the first successful United States orbital surveillance program, comprising a series of five Naval Research Laboratory electronic surveillance and solar astronomy satellites, launched from 1960 t ...

(GRAB) electronic intelligence (ELINT) satellite for the

United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...

. These now-declassified satellites operated under a cover story of providing solar radiation data and included an electronics package to detect Soviet air defense radar signals. GRAB-1 was the world's first successful

reconnaissance satellite A reconnaissance satellite or intelligence satellite (commonly, although unofficially, referred to as a spy satellite) is an Earth observation satellite or communications satellite deployed for military or intelligence applications. The ...

, preceding the first Corona mission to return film (Discoverer 14 on August 18) by almost two months. On 29 June 1961, the Ablestar stage used to launch

Transit 4A The Transit system, also known as NAVSAT or NNSS (for ''Navy Navigation Satellite System''), was the first satellite navigation system to be used operationally. The radio navigation system was primarily used by the U.S. Navy to provide accurat ...

, which became the first object to unintentionally explode in space, creating at least 294 trackable pieces of

space debris Space debris (also known as space junk, space pollution, space waste, space trash, space garbage, or cosmic debris) are defunct human-made objects in spaceprincipally in Earth orbitwhich no longer serve a useful function. These include dere ...

Thor-Delta

The Delta second stage was derived from the Able second stage. Members of the

rocket family derived from the Thor-Delta continue to launch satellites and space probes. By 1969, the Thor core was being used regularly both in Delta vehicles and in the USAF Standard Space Launch Vehicle (SLV-2), with thrust augmentation and a variety of upper stages.

Thor-Agena

Together with the Agena upper stage, Thor was the booster of the

Thor-Agena Thor-Agena was a series of orbital launch vehicles. The launch vehicles used the Douglas Aircraft Company, Douglas-built Thor (rocket family), Thor first Multistage rocket, stage and the Lockheed Corporation, Lockheed-built RM-81 Agena, Agena ...

vehicle used to launch the early Corona (also known as "Keyhole" and "Discoverer") satellites from

Vandenberg AFB Vandenberg Space Force Base , previously Vandenberg Air Force Base, is a United States Space Force Base in Santa Barbara County, California. Established in 1941, Vandenberg Space Force Base is a space launch base, launching spacecraft from the ...

. These were the first photographic spy satellites, used for photographic surveillance of the

Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

, China and other areas. Thor-Agenas were used as launch vehicles for Corona satellites from June 1959 through May 1963. The Thrust Augmented Thor (TAT) was developed to handle the growing satellites of the Corona program. It added three Castor solid-fuel rocket strapon boosters—each providing 53,000 lbf (236 kN) thrust—to the standard Thor core stage. The boosters were lit on the ground and jettisoned after burnout. The Thrust-Augmented Long Tank Thor/Agena incorporated modifications allowing 49,000 lb (22,000 kg) more propellant and was capable of sending payloads ranging from 1400 to about 2800 pounds into polar circular orbits.

Thorad-Agena

The Thorad-Agena (pictured) was developed from Thor. It used a Long Tank Thor to launch an Agena-D upper stage.

References