Thor-Ablestar

Short description: American expendable launch system

Thor-Ablestar

The launch of a Thor-Ablestar 2 with a Transit satellite.

Function| Orbital carrier rocket
Manufacturer| Douglas / Aerojet
Country of origin| United States
Size
Height| 29 metres (95 ft)
Diameter| 2.44 metres (8 ft 0 in)
Mass| 53,000 kilograms (117,000 lb)
Stages| 2
Capacity
Payload to 1100km LEO| 150 kilograms (330 lb)
Associated rockets
Family| Thor
Comparable| Delta
Launch history
Launch sites| LC-17, Cape Canaveral Air Force Station
LC-75-1, Arguello
Total launches| 19
Successes| 12
Failures| 5
Partial failures| 2
First flight| 13 April 1960
Last flight| 13 August 1965
First stage – Thor
Engines| 1 MB-3-1
Thrust| 760.64 kilonewtons (171,000 lbf)
Specific impulse| 285 sec
Burn time| 164 seconds
Fuel| RP-1/LOX
Second stage – Ablestar
Engines| 1 AJ-10
Thrust| 36.02 kilonewtons (8,100 lbf)
Specific impulse| 280 sec
Burn time| 296 seconds
Fuel| HNO3/UDMH

The Thor-Ablestar, or Thor-Able-Star, also known as Thor-Epsilon [1] was an early American expendable launch system consisting of a PGM-17 Thor missile, with an Ablestar upper stage. It was a member of the Thor family of rockets, and was derived from the Thor-Able.

The Ablestar second stage was an enlarged version of the Able, which gave the Thor-Ablestar a greater payload capacity compared to the 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.[2]

Two versions were built; the Thor-Ablestar 1, with a DM-21 Thor and an AJ-10-104 second stage engine, and the Thor-Ablestar 2, which had a DSV-2A Thor first stage, and an uprated AJ-10-104D engine on the second stage.[1] Thor-Ablestar 1 launches occurred from LC-17 at Cape Canaveral Air Force Station , and Thor-Ablestar 2 rockets were launched from LC-75-1 at Vandenberg Space Force Base and is now designated SLC-2.

## Launches

Nineteen Thor-Ablestar were launched between 1960 and 1965, of which four failed, and a fifth resulted in a partial failure, as only one of two payloads separated from the upper stage.[2]

The first failure was the launch of Courier 1A, an experimental communications satellite, on 19 August 1960 when the first stage shut down 30 seconds earlier than planned and was destroyed by the Range Safety officer. On 30 November, another launch involving a Transit satellite failed in practically identical fashion. This episode nearly created an international incident as parts of the Thor landed in Cuba. War was threatened. Cuban leader Fidel Castro subsequently sold off the Thor's engine to the Soviets and the Chinese received its thrust vectors, which ended up proving valuable to the latter's development of a ballistic missile capability. To prevent this from happening again, future Thor Ablestar launches had their flight paths modified to avoid passing over Cuba.

The launch of a Transit satellite on 22 February 1961 was successful, but its companion Lofti satellite failed to separate from the second stage.

On 29 June 1961, a Thor-Ablestar successfully inserted a Transit-4A into orbit, but two hours later the Ablestar exploded for unknown reasons into hundreds of pieces, which remained in orbit. This is the first known artificial object to break up unintentionally in space.[3]

The third launch failure occurred on 24 January 1962 when the second stage produced insufficient thrust to achieve orbital velocity for several piggybacked satellites.[4] The fourth and final failure was the launch of an Anna geodetic satellite on 10 May 1962 when the second stage completely failed to ignite.

Date/Time

(UTC)

| S/N  | Launch Site  | Payload  | Function  | Outcome

|
|
|
|
|

1960-04-13

12:02:36

| Thor 257

Ablestar 002

| CCAFS LC-17B  | Transit 1B  | Navigation  | Success, maiden flight of Thor-Ablestar
1960-06-22

05:54

| Thor 281

Ablestar 003

| CCAFS LC-17B  | Transit 2A, GRAB-1 (Solrad 1)  | Navigation, ELINT  | Success
1960-08-18

19:58

| Thor 262

Ablestar 004

| CCAFS LC-17B  | Courier 1A  | Communications  | Failure (Premature first stage cutoff. RSO T+150 seconds.)
1960-10-04

17:50

| Thor 293

Ablestar 005

| CCAFS LC-17B  | Courier 1B  | Communications  | Success
1960-11-30

19:50

| Thor 283

Ablestar 006

| CCAFS LC-17B  | Transit 3A, GRAB-2 (Solrad-2)  | Navigation, ELINT  | Failure (Premature Thor cutoff. RSO. Debris fell in Cuba.)
1961-02-22

03:45

| Thor 313

Ablestar 007

| CCAFS LC-17B  | Transit 3B, LOFTI-1 | Navigation, Technology  | Success
1961-06-29

04:22

| Thor 315

Ablestar 008

| CCAFS LC-17B  | Transit 4A, Injun 1, GRAB-3 (Solrad 3)  | Navigation, Ionospheric, ELINT  | Success
1961-11-15

22:26

| Thor 305

Ablestar 009

| CCAFS LC-17B  | Transit 4B, TRAAC  | Navigation  | Success, Transit Research and Attitude Control
1962-01-24

09:30

| Thor 311

Ablestar 010

| CCAFS LC-17B  | LOFTI-2, SECOR, GRAB-4 (Solrad 4), Injun 2, SURCAL 1  | Technology, Geodesy, ELINT, Ionospheric, Calibration  | Failure (second stage insufficient thrust)
1962-05-10

12:06

| Thor 314

Ablestar 011

| CCAFS LC-17B  | ANNA 1A  | Geodesy  | Failure (second stage failed to ignite)
1962-10-31

08:08

| Thor 319

Ablestar 012

| CCAFS LC-17A  | ANNA 1B | Geodesy  | Success, final flight of Thor DM-21 Ablestar
1964-04-21

18:50

| Thor 379

Ablestar 014

| VAFB LC-75-1-1  | Transit 5BN-3, Transit 5E-4  | Navigation  | Failure
1964-10-06

17:04:21

| Thor 423

Ablestar 016

| VAFB LC-75-1-2  | OPS 5796 (Transit O-1),

Dragsphere 1, Dragsphere 2

| Navigation  | Success
1964-12-13

00:08:10

| Thor 427

Ablestar 017

| VAFB LC-75-1-2  | OPS 6582 (Transit O-2), Transit 5E-5  | Navigation  | Success
1965-03-11

13:39

| Thor 440

Ablestar 018

| VAFB LC-75-1-1  | OPS 7087 (Transit O-3), SECOR 2  | Navigation, Geodesy  | Success
1965-06-24

22:35

| Thor 447

Ablestar 019

| VAFB LC-75-1-1  | OPS 8480 (Transit O-4)  | Navigation  | Success
1965-08-13

22:11

| Thor 455

Ablestar 020

| VAFB LC-75-1-1  | OPS 8464 (Transit O-5), Dodecapole 2, Tempsat 1,Surcal 5, Long Rod 1, Calsphere 2  | Navigation, Calibration  | Success, final flight of Thor-Ablestar

## See also

* List of Thor and Delta launches (1960–1969)

## References

1. ↑ 1.0 1.1 Krebs, Gunter. "Thor Able-Star". Gunter's Space Page. http://space.skyrocket.de/doc_lau/thor_ablestar.htm.
2. ↑ 2.0 2.1 Wade, Mark. "Delta". Encyclopedia Astronautica. http://www.astronautix.com/lvs/delta.htm. Retrieved 30 November 2008.
3. ↑ Orbital Debris: A Chronology. NASA JSC. January 1999. p. 18. http://ston.jsc.nasa.gov/collections/TRS/_techrep/TP-1999-208856.pdf. Retrieved 13 February 2016. "Two hours after separating from the U.S. Transit 4-A satellite, its Able Star upper stage becomes the first known artificial object to break up unintentionally in space. The cause of the explosion is unknown. The event produces at least 294 trackable pieces, more than tripling the number of known satellites of Earth."
4. ↑ "A-Okay So Far: Glenn, Atlas Ready". The Gazette. Associated Press (AP) (Montreal, QC): p. 1. 25 January 1962. https://news.google.com/newspapers?id=5Y4jAAAAIBAJ&sjid=z50FAAAAIBAJ&pg=2294,3815135.

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