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In 1954, the USAF issued a Request for Proposals for an Intermediate
Range Ballistic Missile capable of carrying a thermonuclear bomb 1,500 miles
-- the distance from England to Moscow. The Douglas Aircraft
Company came up with a design that used the warhead and guidance system
already in development for the Atlas missile. For propulsion it used the
engine from the Navaho cruise missile, which at the time was "the only one
available." Since the missile would be deployed from England, security
during transporting was a major design consideration, so the Douglas design
was only sixty-five feet long, permitting it to fit inside a Douglas C-124
Globemaster II for tightly controlled movement to and from launch sites.
In August 1956, only seven months after Douglas received the contract, the
first missile was ready to fly. It was named the Thor.
By September 1957, Thor had successfully flown to a
range of 1,250 miles while heavily weighted down by instrumentation. The
first operational Thors were deployed in England by the end of 1958 and
remained there until August 1963.
The Thor evolved through several 3-stage and 4-stage
configuration, for use in many roles, including space exploration, military
testing, scientific exploration, and strategic reconnaissance.
Its first application in the area of space
exploration was in August 1958 in a failed attempt to launch the first
Pioneer lunar probe. During 1962, several Thors were also used for
high-altitude tests of nuclear weapons, and were launched from Johnston
Island in the south Pacific to detonate above the atmosphere. |
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Thor Able. The second stage of
the ill-fated Vanguard rocket, the Aerojet AJ-10, was "jury-rigged" to the Thor
to form Thor-Able. Thor-Able tested a heat shield for use on the Atlas ICBM.
Thor-Able-Star had a solid propellent
third stage motor, which flew the earliest American lunar attempts, known as Pioneer; and
in 1960 a Thor-Able orbited TIROS-1 (Television and Infrared Observation Satellite), the
world's first weather satellite.
The first Thor-Delta flew on 13 May 1960 but
failed due to a problem with attitude control in the second stage. Three months later, on
12 August, the Echo 1 reflight was a total success, as a 100-foot diameter aluminized
mylar balloon inflated in orbit, providing a reflective surface so that two-way voice
signals could be bounced from ground stations on the west and east coasts. The passive
communications experiment of Echo 1. A constitutes the first communications
satellite in history.
Thor Agena (shown above) Another Thor upper
stage was the Lockheed-built Agena, which was the booster for the Corona (a.k.a.
Discoverer) program, the United States' first spy satellite. The Corona reconnaissance
spacecraft was launched into polar orbit to take photographic swaths as it passed over the
Soviet Union. Corona was designed to collect its exposed film in a heat-resistant
"bucket" at the nose. This bucket would then reenter over the Pacific Ocean to
be recovered in the air by a passing aircraft. Strange as this sounds, the Corona program
was very successful over the years, beginning with Discoverer XIV as it was snatched in
midair by a C-119 cargo plane on 18 August 1960. It provided the earliest photos of the
USSR's Plesetsk rocket base. Thor-Agenas (shown above) also boosted Echo
2 (passive communications), Nimbus 1 (weather), and Alouette 1 (Canada's first satellite),
among others.
Thor was last launched in 1972. |
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