The Delta L, Thor-Delta L, or Thrust-Augmented Long Tank Thor-Delta was an American

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 expendable launch system

Expendable launch system

An expendable launch system is a launch system that uses an expendable launch vehicle to carry a payload into space. The vehicles used in expendable launch systems are designed to be used only once , and their components are not recovered for re-use after launch...

 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.

The Delta L was a three stage rocket. The first stage was a Long Tank Thor, a stretched version of the Thor

PGM-17 Thor

Thor was the first operational ballistic missile of the U.S. Air Force . Named after the Norse god of thunder, it was deployed in the United Kingdom between 1959 and September 1963 as an intermediate range ballistic missile with thermonuclear warheads. Thor was in height and in diameter. It was...

 missile, augmented by three Castor-2 solid rocket booster

Solid rocket booster

Solid rocket boosters or Solid Rocket Motors, SRM, are used to provide thrust in spacecraft launches from the launchpad up to burnout of the SRBs. Many launch vehicles include SRBs, including the Ariane 5, Atlas V , and the NASA Space Shuttle...

s. The second stage was the Delta E. An FW-1D solid rocket motor was used as the third stage.

The first launch of the Delta L occurred on 27 August 1969, from Launch Complex 17A

Cape Canaveral Air Force Station Launch Complex 17

Cape Canaveral Air Force Station Space Launch Complex 17 , previously designated Launch Complex 17 , was a launch site at Cape Canaveral Air Force Station, Florida used for Thor and Delta rocket launches between 1958 and 2011....

 at the Cape Canaveral Air Force Station

Cape Canaveral Air Force Station

Cape Canaveral Air Force Station is an installation of the United States Air Force Space Command's 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in the state of Florida, CCAFS is the primary launch head of America's Eastern Range with four launch pads...

. The rocket's hydraulics system malfunctioned, and 383 seconds after launch the Range Safety Officer

Range Safety Officer

In the field of rocketry, Range Safety Officer is a generic term referring to an individual who monitors the performance of rockets in flight, and who is responsible for their remote destruction if it should be judged that they pose a hazard...

 activated the self-destruct system. Neither the Pioneer E nor the TETR payloads achieved orbit. The second, and final, Delta L launch was from Space Launch Complex 2E

Vandenberg AFB Space Launch Complex 2

Space Launch Complex 2 is an active rocket launch site at Vandenberg Air Force Base, in California, USA. It consists of two launch pads. The East pad , which has been demolished, was used for Delta, Thor-Agena and Thorad launches between 1966 and 1972...

 at the Vandenberg Air Force Base

Vandenberg Air Force Base

Vandenberg Air Force Base is a United States Air Force Base, located approximately northwest of Lompoc, California. It is under the jurisdiction of the 30th Space Wing, Air Force Space Command ....

, on 31 January 1972. It successfully placed the HEOS-2 satellite into a highly elliptical orbit

Highly Elliptical Orbit

A highly elliptical orbit is an elliptic orbit with a low-altitude perigee and a high-altitude apogee. It is a type of high Earth orbit....

.