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Thor-Able II Transit 1A.jpg
Launch of the Transit 1A satellite on a Thor-Able II
Function Expendable launch system
Sounding rocket
Manufacturer Douglas/Aerojet
Country of originUnited States
Height26.9 metres (88 ft) - 27.8 metres (91 ft)
Diameter2.44 metres (8 ft 0 in)
Mass51,608 kilograms (113,776 lb)
Payload to 640km LEO 120 kilograms (260 lb)
Associated rockets
Family Thor
Derivatives Thor-Ablestar
Comparable Luna
Launch history
Launch sites LC-17A, Canaveral
Total launches16
First flight24 April 1958
Last flight1 April 1960
Notable payloads Pioneer
First stage – Thor
Engines1 LR79-7
Thrust758.71 kilonewtons (170,560 lbf)
Specific impulse 282 seconds (2.77 km/s)
Burn time165 seconds
Fuel RP-1/LOX
Second stage – Able
Engines1 AJ-10
Thrust34.69 kilonewtons (7,800 lbf)
Specific impulse 270 seconds (2.6 km/s)
Burn time115 seconds
Third stage (optional) – Altair
Engines1 X-248
Thrust12.45 kilonewtons (2,800 lbf)
Specific impulse 256 seconds (2.51 km/s)
Burn time38 seconds
Fuel Solid
Thor-Able at the Air Force Space & Missile Museum LC-26B Thor-Able.jpg
Thor-Able at the Air Force Space & Missile Museum

The Thor-Able was an American expendable launch system and sounding rocket used for a series of re-entry vehicle tests and satellite launches between 1958 and 1960. It was a two stage rocket, consisting of a Thor IRBM as a first stage and a Vanguard-derived Able second stage. On some flights, an Altair solid rocket motor was added as a third stage. It was a member of the Thor family and an early predecessor of the Delta. [1] [2]

Expendable launch system Launch system that uses an expendable launch vehicle

An expendable launch system is a launch vehicle that uses disposable components to carry a payload into space. ELVs typically consist of several rocket stages that are discarded sequentially as their fuel is exhausted and the vehicle gains altitude and speed. Most satellites and human spacecraft are currently launched on ELVs, with advantages including the possibility of cost savings through mass production, a greater payload fraction, and extensive development history.

Sounding rocket Rocket carrying scientific instruments

A sounding rocket, sometimes called a research rocket, is an instrument-carrying rocket designed to take measurements and perform scientific experiments during its sub-orbital flight. The rockets are used to carry instruments from 30 to 90 miles above the surface of the Earth, the altitude generally between weather balloons and satellites; the maximum altitude for balloons is about 25 mi (40 km) and the minimum for satellites is approximately 75 mi (121 km). Certain sounding rockets have an apogee between 620 and 930 miles, such as the Black Brant X and XII, which is the maximum apogee of their class. Sounding rockets often use military surplus rocket motors. NASA routinely flies the Terrier Mk 70 boosted Improved Orion, lifting 600–1,000-pound (270–450 kg) payloads into the exoatmospheric region between 60 and 125 miles.

Satellite Human-made object put into an orbit

In the context of spaceflight, a satellite is an object that has been intentionally placed into orbit. These objects are called artificial satellites to distinguish them from natural satellites such as Earth's Moon.



Sixteen Thor-Ables were launched, nine on sub-orbital re-entry vehicle test flights and seven on orbital satellite launch attempts. Six launches resulted in failures, in which three of those failures were the result of an Altair upper stage added to the rocket to allow it to launch the spacecraft onto a trans-lunar trajectory. All sixteen launches occurred from Cape Canaveral Air Force Station Launch Complex 17A. [3]

A sub-orbital spaceflight is a spaceflight in which the spacecraft reaches outer space, but its trajectory intersects the atmosphere or surface of the gravitating body from which it was launched, so that it will not complete one orbital revolution.

Orbital spaceflight Spaceflight where spacecraft orbits an astronomical body

An orbital spaceflight is a spaceflight in which a spacecraft is placed on a trajectory where it could remain in space for at least one orbit. To do this around the Earth, it must be on a free trajectory which has an altitude at perigee above 100 kilometers (62 mi); this is, by at least one convention, the boundary of space. To remain in orbit at this altitude requires an orbital speed of ~7.8 km/s. Orbital speed is slower for higher orbits, but attaining them requires greater delta-v.

Altair (rocket stage) Solid-fuel rocket

The Altair was a solid-fuel rocket with a fiberglass casing, initially developed for use as the third stage of Vanguard rockets. It was manufactured by Allegany Ballistics Laboratory (ABL) as the X-248. It was also sometimes called the Burner 1.


The Thor-Able vehicle had a stronger airframe than the standard Thor IRBM and had the inertial guidance system replaced by a radio guidance package mounted on the Able stages. It saw its first test on April 23, 1958 when Vehicle 116 was launched from LC-17A with a biological nose cone containing a mouse named MIA (Mouse In Able). At 7:10 PM EST, the Thor's engine roared to life and drove the Able stage and its tiny passenger into the evening sky. Two minutes and fifteen seconds after launch, at an altitude of 50 miles (80 km), the Thor exploded and sent the hapless rodent into the Atlantic Ocean instead of space. The cause of the failure was traced to a turbopump bearing coming loose and resulting in pump shutdown and instant loss of thrust. With no attitude control, the Thor pitched down and its LOX tank ruptured from aerodynamic loads. On July 9, Thor 118 lifted off for a second attempt with a mouse named MIA II. The booster, including the unproven Able stage, performed successfully and the biological nose cone was driven back into the atmosphere for splashdown in the South Atlantic, but recovery crews failed to locate the capsule and it sank into the ocean. A third attempt was made on July 23. The press refused to call the mouse by the name of MIA III, so she was instead christened "Wickie", after a local female news reporter who had covered the space program at Cape Canaveral. Unfortunately, Wickie was no more lucky than her predecessors when recovery crews once again failed to locate the capsule after splashdown, but telemetry data confirmed the mouse's survival from liftoff through reentry and proved comprehensively that living organisms could survive space travel. Attention now turned to Thor-Able 127 and Pioneer 0, the world's first lunar probe. This flight took place on August 17, but ended embarrassingly when the Thor exploded 77 seconds into the launch due to another turbopump malfunction. After an Atlas missile test a month later also failed due to the turbopumps, the Air Force Ballistic Missile Division quickly replaced the pumps in all of their missiles and this problem did not repeat itself again.

On October 10, Pioneer 1 was launched on Thor 130. The second stage shut down too early and the probe did not have sufficient velocity to escape Earth's orbit. It reentered the atmosphere and burned up 43 hours after launch.

Pioneer 2 was launched November 8 and reentered the atmosphere less than an hour after launch when the third stage failed to ignite.

The next six Thor-Able flights were suborbital tests for the Air Force (January 23, February 28, March 21, April 8, May 20, and June 11, 1959). All of these were successful except the first one, which failed to stage due to an electrical problem and fell into the Atlantic Ocean.

On August 7, Explorer 6 (a scientific satellite) was launched on Vehicle 134 and successfully orbited.

On September 17, Transit 1A failed to orbit due to the third stage again failing to ignite.

On November 3, Pioneer 5 was successfully launched. Intended originally as a Venus probe, technical delays caused it to be launched after the 1959 Venus window had closed so that it was instead sent into heliocentric orbit.

The final Thor-Able launch orbited Tiros 1 on April 4, 1960.

The Able upper stage name represents its place as the first in the series, from the Joint Army/Navy Phonetic Alphabet. [4]

Able (rocket stage)

The Able rocket stage was a rocket stage manufactured in the United States by Aerojet as the second of three stages of the Vanguard rocket used in the Vanguard project from 1957 to 1959. The rocket engine used nitric acid and UDMH as rocket propellants. The Able rocket stage was discontinued in 1960. The improved Ablestar version was used as the upper stage of the Thor-Ablestar two stage launcher. The Ablestar second stage was an enlarged version of the Able rocket stage, which gave the Thor-Ablestar a greater payload capacity compared to the earlier Thor-Able. It also incorporated restart capabilities, allowing a multiple-burn trajectory to be flown, further increasing payload, or allowing the rocket to reach different orbits. It was the first rocket to be developed with such a capability and development of the stage took a mere eight months.

See also

Thor (rocket family) American rocket family

Thor was an American space launch vehicle derived from the PGM-17 Thor intermediate-range ballistic missile. The Thor rocket was the first in a large family of space launch vehicles that came to be known as Delta. The last derivative of the Thor was retired in 2018, which was the first stage of the Delta II.

Related Research Articles

Pioneer 0

Pioneer 0 was a failed United States space probe that was designed to go into orbit around the Moon, carrying a television camera, a micrometeorite detector and a magnetometer, as part of the first International Geophysical Year (IGY) science payload. It was designed by the United States Air Force (USAF) as the first satellite in the Pioneer program and was one of the first attempted launches beyond Earth orbit by any country, but the rocket failed shortly after launch. The probe was intended to be called Pioneer, but the launch failure precluded that name.

<i>Pioneer 1</i>

On October 11, 1958, Pioneer 1 became the first spacecraft under the auspices of NASA, the newly formed space agency of the United States. The flight was the second and most successful of the three Thor-Able space probes.

Cape Canaveral Air Force Station Spaceport on Cape Canaveral, Florida

Cape Canaveral Air Force Station (CCAFS) is an installation of the United States Air Force Space Command's 45th Space Wing.

PGM-17 Thor first operational ballistic missile deployed by the U.S. Air Force

Thor was the first operational ballistic missile deployed by the U.S. Air Force (USAF). 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 (IRBM) with thermonuclear warheads. Thor was 65 feet (20 m) in height and 8 feet (2.4 m) in diameter. It was later augmented in the U.S. IRBM arsenal by the Jupiter.

Delta (rocket family) Rocket family

Delta is an American versatile family of expendable launch systems that has provided space launch capability in the United States since 1960. More than 300 Delta rockets have been launched with a 95% success rate. Only the Delta IV remains in use as of 2019. Delta rockets are currently manufactured and launched by the United Launch Alliance.

PGM-19 Jupiter ballistic missile

The PGM-19 Jupiter was the first nuclear tipped, medium-range ballistic missile (MRBM) of the United States Air Force (USAF). It was a liquid-propellant rocket using RP-1 fuel and LOX oxidizer, with a single Rocketdyne LR70-NA rocket engine producing 667 kN of thrust. It was armed with the 1.44 megaton W49 nuclear warhead. The prime contractor was the Chrysler Corporation.

Explorer 2 was to be a repeat of the Explorer 1 mission. However, due to a failure in the rocket during launch, the spacecraft did not reach orbit.

Cape Canaveral Air Force Station Space Launch Complex 17 rocket launch site

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

Juno II American space launch vehicle used during the late 1950s and early 1960s

Juno II was an American space launch vehicle used during the late 1950s and early 1960s. It was derived from the Jupiter missile, which was used as the first stage.

Delta E American expendable launch system

The Delta E, or Thor-Delta E was an American expendable launch system used for twenty-three orbital launches between 1965 and 1971. It was a member of the Delta family of rockets.

The Burner and Burner 2 rocket stages have been used as upper stages of launch vehicles such as the Thor-Burner and Delta since 1965. The currently available Burner 2 is powered by a Star 37 solid rocket motor. Thor Altair and Thor Burner were mainly used for US military meteorological programs (DMSP), although they also launched technological satellites.

Atlas-Able American expendable launch system

The Atlas-Able was an American expendable launch system derived from the SM-65 Atlas missile. It was a member of the Atlas family of rockets, and was used to launch several Pioneer spacecraft towards the Moon. Of the five Atlas-Able rockets built, two failed during static firings, and the other three failed to reach orbit.

The Thor DSV-2 was a series of sounding rockets, test vehicles, and anti-satellite weapons derived from the Thor Intermediate-range ballistic missile. It was also used as the first stage of several Thor-derived expendable launch systems


The Thor-Delta, also known as Delta DM-19 or just Delta was an early American expendable launch system used for 12 orbital launches in the early 1960s. A derivative of the Thor-Able, it was a member of the Thor family of rockets, and the first member of the Delta family.

Delta B

The Delta B, or Thor-Delta B was an American expendable launch system used for nine orbital launches between 1962 and 1964. A derivative of the Thor-Delta, it was a member of the Delta family of rockets.

Delta C

The Delta C, or Thor-Delta C was an American expendable launch system used for thirteen orbital launches between 1963 and 1969. It was a member of the Delta family of rockets.

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.

Delta N

The Delta N or Thor-Delta N was an American expendable launch system used for nine orbital launches between 1968 and 1972. It was a member of the Delta family of rockets, and the last Delta to be given an alphabetical designation - subsequent rockets were designated using a four digit numerical code.


  1. Krebs, Gunter. "Thor Able". Gunter's Space Page. Retrieved 2008-11-10.
  2. Wade, Mark. "Delta". Encyclopedia Astronautica. Archived from the original on 2013-05-22. Retrieved 2008-11-10.
  3. Lethbridge, Cliff. "Thor-Able Fact Sheet". Cape Canaveral Rocket and Missile Programs. Spaceline. Archived from the original on 2007-06-13. Retrieved 2008-11-10.
  4. Helen T. Wells; Susan H. Whiteley & Carrie E. Karegeannes. Origin of NASA Names. NASA Science and Technical Information Office. p. 5.