Thor (rocket)

The first Thor-IRBM (# 101) before takeoff in Cape Canaveral, Florida (January 25, 1957)

Thor Able I with Pioneer 1

Thor Able star

The Thor ( PGM-17 Thor ) was a single-stage ballistic medium - range missile ( Intermediate Range Ballistic Missile , IRBM for short ) developed and produced in the USA . It was powered by liquid oxygen and RP-1 , a type of kerosene. It was 19.8 meters long and 2.44 meters in diameter. The takeoff mass was 49,900 kilograms (before ignition).

development

The development of the Thor began in 1954 with studies for a rocket with a range of 2,400 km , whereby one of the specifications was that this should fit into a C-124 transporter. The development contract for the Thor missile was signed with the Douglas Aircraft Company in December 1955. Development ended in July 1956, the first production model of the Thor missile was delivered to the US Air Force at Cape Canaveral Air Force Station in Florida. The tests ran for eleven months. The Thor missile program thus had the shortest test period from its presentation to handover to an American missile program.

The first four Thor test starts (from January 25, 1957) were failures. These early failures were followed by intensive studies with several subsequent successful launches. The missile entered the USAF's active inventory in September 1958, making it the world's first medium-range missile to be operational.

The Thor was declared operational in 1959 and assigned to Strategic Air Command . The rocket was also deployed in Great Britain between 1959 and 1963, where it was subordinated to the Royal Air Force .

With the development of better missiles, the Thor was retired in 1963 as a weapon system in its originally intended role as a ballistic missile. In contrast, individual missiles of this type were kept in readiness as anti-satellite weapons as part of program 437 until 1975 .

Use as a launcher

Already at an early stage of development it was noticed that the Thor is well suited as a base for a satellite launcher. The first launch of the Thor in the role of a launcher took place on April 23, 1958 (local time), but ended in an explosion. It was then used intensively for space travel , where it later formed the basis for the Delta family . The Thor rocket as the first stage rocket was used with different upper stages for launching different payloads:

• Thor Able: Thor with the upper stage of the Vanguard missile, launched e.g. B. early space probes of type Pioneer , first start on April 23, 1958 (false start), Last start April 1, 1960, a total of 16 starts
  • Thor Able with Vanguard second stage
  • Thor Able I with Altair solid propulsion as a third stage
  • Thor Able II / III / IV with two-stage engines that are further improved compared to the Able
  • Thor Able II M1 was an Able II with Altair solid propulsion as a third stage
• Thor Ablestar: improved Thor Able, mainly for military payloads, first launch on April 13, 1960, last launch August 13, 1965, a total of 19 launches, 14 of them successful
  • Thor Able-Star: Version with significantly increased fuel supply for the upper level
  • Thor Able-Star 2: Version with improved first stage (Thor DSV 2A instead of Thor DM 21)
• Thor Delta: improved Thor Able, mainly civil payloads: e.g. As TIROS , Telstar , later simply Delta called
• Thor Agena : multiple ignitable upper stage, predominantly military payloads: e.g. B. Discoverer , Keyhole , a total of 365 pieces built
  • Thor Agena A: with Agena upper stage of the Atlas rocket, first launch January 21, 1959, last launch September 13, 1960
  • Thor Agena B: Version with doubled fuel supply and slightly improved engine Bell 8061 or later Bell 8069, first start October 26, 1960, last start May 15, 1966, started 45 times, 9 false starts
  • Thor Agena D: standardized version of the Agena B for different payloads, first launch June 28, 1962, last launch January 17, 1968
  • Thrust Augmented Thor Agena B / D: Thor Agena B / D reinforced with three Castor-1 solid rockets on the thrust frame of the first-stage engine
• Thor Burner: modified medium-range missile with a small solid upper stage, mainly used to launch military DMSP weather satellites, from May 20, 1965 to February 19, 1976 from the SLC-10 launch complex in Vandenberg, a total of 24 launches with two failures
  • Thor Burner 1: with Star 20 solid fuel propulsion
  • Thor Burner 2: with Star 37 solid fuel drive as the second stage and Star 13 solid fuel drive as the third stage
  • Thor Burner 2A: with Star 37B solid fuel drive as the second stage and Star 26B solid fuel drive as the third stage

To increase performance, the Thor Agena and Thor Delta were reinforced with three additional small auxiliary missiles. This made it almost twice as strong as the original Thor.

The Long Tank Thor (Thorad Agena D SLV 2G or 2H) was an extended version of the Thor first stage, which started for the first time in the summer of 1966. It was 21.5 meters long and could hold 20% more fuel. The diameter was also 2.44 meters. It was used between August 9, 1966 and May 25, 1972 a total of 43 times (with two false starts) to launch military keyholes and some civilian satellites (e.g. OGO 6 ). The payload was 2 tons in low orbit.

In 1960 the first Thor Delta, an improved Thor missile, was introduced. The name was officially shortened to Delta to differentiate it from the military variations that continued to bear the Thor name.

This rocket was launched from Vandenberg Air Force Base until 1972, putting both military and civilian satellites into orbit.

Technical specifications

The basis of all Thor missiles is the first stage of the ICBM. This is equipped with a Rocketdyne LR79-NA-9 (also known as SD-3 or MB-3) that can be swiveled hydraulically about two axes with 760 kN vacuum thrust, which was also used in the Atlas and Juno II. In addition, two smaller Vernier engines of the type LR-102, each with 4.54 kN thrust and nozzles inclined by 6 °, provide roll control. The fuel tanks (oxygen tank below, kerosene tank above) were each composed of two half-shells, which had a wall thickness of 6.35 mm. For the launch vehicle, this first stage was supplemented with various upper stages - for example the Able, various Agena versions and later also the Vanguard. This created a large number of versions from which the later Delta rocket emerged.

	Thor IRBM	Thor Able IV	Thor Agena A	Thor Able star	Thor Burner 2A	Thor AT Agena D	Thorad Agena D SLV2H
length	19.8 m	27.0 m	25.8 m	24.6 m	22.9 m	29.3 m	33.4 m
diameter	2.44 m
Takeoff mass	49.9 t	52.0 t	53.1 t	53.0 t	51.8 t	71.0 t	85.1 t
Payload LEO	W-49	120 kg (40 kg ESC)	250 kg	150 kg	770 kg (300 kg SSO)	1500 kg (650 kg SSO)	2,000 kg (750 kg SSO)
stages	1	3	2		3
1st stage
Engine	Rocketdyne LR-79-7						Rocketdyne MB-3-3
Start thrust	667 kN						765 kN
fuel	RP-1 / LOX
Burn time	165 s			164 p	165 s		215 s
Takeoff / empty mass	49.34 / 3.12 t	49.34 / 3.12 t	49.34 / 3.12 t	48.35 / 2.95 t	49.34 / 3.18 t	49.34 / 3.12 t	71.51 / 3.72 t
length	18.4 m		19.2 m	18.4 m			21.4 m
diameter	2.44 m
2nd stage
Engine		Aerojet AJ-10	Bell 8048	Aerojet AJ-10-104	Thiokol TE-M-364-2	Bell 8081	Bell 8086
thrust		34.3 kN	68.95 kN	35.1 kN	44.5 kN	71.2 kN	71.2 kN
fuel		UDMH / nitric acid			HTBP	UDMH / nitric acid
Takeoff / empty mass		2.27 / 0.82 t	3.79 / 0.89 t	4.47 / 0.59 t	0.72 / 0.065 t	6.82 / 0.67 t
Burn time		115 s	120 s	296 s	42 p	240 s
length		6.57 m	4.73 m	5.88 m	0.84 m	7.09 m	6.23 m
diameter		0.84 m	1.52 m	1.40 m	0.84 m	1.52 m	1.52 m
3rd stage						booster
Engine		Allegheny Ballistics X-248			Thiokol TE-M-442-1	3 × M-33-20-4	3 × TX-354-5
thrust		12.45 kN			34.63 kN	450.3 kN	474 kN
fuel		Firmly			Firmly	Firmly	Firmly
Takeoff / empty mass		250/39 kg			261/23 kg	3,850 / 535 kg	4,470 / 695 kg
Burn time		38 p			18 s	37 p	40 s
length		1.55 m			0.66 m	5.72 m	7.75 m
diameter		0.46 m			0.66 m	0.79 m	0.79 m

Others

The first stage of the Delta II, a Thor XLT

The first stage of today's Delta II is still a Thor version. It's called Thor XLT (E x tra Extended L ong T ank) . This has been extended so much to enlarge the tank that the Delta II cannot take off with a full tank without the solid fuel booster.

See also

• List of nuclear surface-to-surface missiles

Web links

Commons : Thor  - album with pictures, videos and audio files

• Detailed information about the Thor from Bernd Leitenberger
• Early Thor + Atlas Space Launchers at Norbert Bruges

Individual evidence

1. ↑ Eugen Reichl: The rocket type book. Motorbuch-Verlag, Stuttgart 2007, ISBN 978-3-613-02788-6 .