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Thor was the United States's first operational ballistic missile. It was deployed with thermonuclear warheads in the U.K between 1959 and 1963. It went on to spawn a string of space launch vehicles. Its decendants fly to this day as the Delta series of rockets.
Development of the Thor was initiated by the US Air Force in 1954
as a Tactical Ballistic Missile. The goal was a missile system that
could deliver a nuclear warhead over a distance of 1150 to 2300 miles
with a CEP of 2 miles. This range
would allow Moscow to be hit from a launch site in the U.K
The initial design studies were headed by Cmdr. Robert Truax
(US. Navy) and Dr. Adolph K. Thiel (Ramo-Wooldridge Corp, formerly
Redstone Arsenal). They refined the specs to an IRBM with:
Initial development as an IRBM
On November 30, 1955 three companies were given one week to bid on the
project: Douglas, Lockheed, and North American Avation.
They were asked to create "a management team that could pull together
existing technology, skills, abilities, and techniques in 'an
unprecedented time.'" On December 27, 1955 Douglas Aircraft
Corporation was awarded the prime contract for the airframe and
integration. The Rocketdyne division of North American Avation
was awarded the engine contract, AC Spark Plug the primary inertial
guidance system, Bell Labs the backup radio guidance system, and
General Electric the nose cone/reentry vehicle.
Douglas further refined the design by choosing bolted tank bulkheads (as opposed to the initially suggested welded ones) and a tapered fuel tank for improved aerodynamics. The engine was developed as a direct descendant of the Atlas MA-3 booster engine. Changes involved removal of one thrust chamber and a rerouting of the plumbing to allow the engine to fit within the smaller Thor boat-tail. Engine tests where being performed as of March 1956. The first engineering model engine was available in June, followed by the first flight engine in September. Engine development was complicated by serious turbopump problems. Early Thor engines suffered from what was known as "Bearing Walking', whereby the turbopump bearings rotate axially within their housing, causing it to wear out and the bearings to seize.
Thor test launches were to be from LC17 at Cape Canaveral. The
development schedule was so compressed that plans for the Atlas bunker were used to allow the completion of the facility in
time. Nevertheless pad LC17-B was just ready for the first test
flight.
The first flight of the Thor IRBM was on 25 January 1957. The first
airframe, number 101 was delivered in October of the previous year.
The vehicle reached a apogee of 6" whereapon contamination destroyed a
LOX supply valve causing the engine to lose thrust. The Thor slid
backwards through the launch ring and exploded on contact with the
thrust deflector. Serious pad damage occurred.
The second Thor flight (102) lasted 35 seconds after an April 1957 launch.
It was ended by a range safety officer who acted on faulty data from a
readout which showed the missile heading inland over florida.
Thor vehicle 103 (May 1957) exploded on the pad during tanking due to
a faulty main fuel valve resulting in tank overpressurization leading
to tank rupture.
Thor vehicle 104 (Aug 1957) broke up after 92 seconds due to a loss of
guidance.
Thor vehicle 105 (20 September 1957), 21 months after the start of
construction, flew 1100 miles downrange. Estimated range without the
extra load of the R&D instrumentation was 1500 miles.
1957 saw five more flights, the longest of which covered 2700 miles.
All sixty of the Thor missiles deployed in Great Britain were based at above-ground launch sites. The missiles were stored horizontally on transporter-erector trailers and covered by a retractable missile shelter. To fire the weapon, the crew electronically rolled back the missile shelter and then, using a powerful hydraulic launcher-erector, lifted the missile to an upright position. Once it was standing on the launch mount, the missile was fueled and fired. The entire launch sequence took about 15 minutes. When the launch control officer pressed the firing button, the main engine ignited with a roar. It burned for almost 2-l/2 minutes, boosting the missile to a speed of 14,400 feet per second. Ten minutes into its flight the missile reached an altitude of 280 miles, close to the apogee of its elliptical flight path. At that point the reentry vehicle separated from the fuselage and began its descent down toward the target. Total flight time from launch to impact was about 18 minutes.
Thor was noted as forming a good basis for a space launch vehicle
early in its development.
The first space launch type of mission Thor was asked to perform was
the testing of the Atlas reentry vehicle. For these three tests a
Thor core stage was topped by a second stage named Able using the
Aerojet AJ-10-40 engine from the Vanguard second stage. The first
such launch, 116, was lost due to turbopump failure of the main
engine. The results of two succeeding attempts are unknown to this
author.
Thor vehicle 127 was a three stage Thor-Able-Star. The Able stage
from the Atlas reentry vehicle tests was upgraded (to become the Able
I) and topped with a third stage consisting of an unguided Altair
X-248 solid rocket motor. The mission was to place the 84lbs Pioneer
spacecraft into lunar orbit where it would take pictures of the lunar
surface with a TV camera. The mission ended prematurely at 77 seconds
after launch due to yet another turbopump failure.
Thor formed the core of the Thor-Agena vehicle used to launch the
United State's first spy satellites as part of the Corona program.
In January of 1959 the newly formed National Aeronautics and Space Administration released a report entitled "The National Space Vehicle Program". This report addressed the nation's space launch needs.
"Our approach up to this time has been much too diverse in that we fire a few vehicles of a given configuration, most of which have failed to achieve their missions, and then call on another vehicle to take the stage. In this situation no one type of vehicle is tested with sufficient thoroughness and used in enough firiing to achieve a high degree of reliability"
The report proposed four vehicles to form the core of the U.S. spacefleet:
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|1 || 13may60 9:16pm gmt. || Payload: echo 1. pad 17a. Good first stage. second stage attitude control system failure. vehicle destroyed.
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|2 || 12aug60. || good flight. echo 1A placed into 1035 mile, 47degree inclination orbit.
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|3 || 23nov60. || Tiros 2. good lfight.
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|4 || || explorer 10. placed into elliptical 138,000 mile orbit. 78lbs.
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|5 || 12july61. || tiros 3.
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|6 || 16aug61. || explorer 12 Energentic Perticle Explorers. EPE-1. highly elliptical orbit.
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|7 || 8feb62. || tiros 4.
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|8 || 7mar62. || OSO-1 (orbiting solar observatory). 345 mile, 33 degree orbit.
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|9 || 26apr62. || Ariel 1. Ariel 1 was seriously damaged by Starfish Prime
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|10 || 19jun62. || tiros 5
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|11 || 10jul62. || Telstar 1. Also damanaged by Starfish Prime.
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|12 || 18sep62. || tiros 6
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13. EPE2
Launch Pad
First Launches
Deployment
Thor was deployed to the UK starting in August 1958.Noteworthy Thor IRBM flights
Thor becomes a launch vehicle
Thor and the Corona program
Thor becomes Delta
NASA let the original Delta contract to Douglas in April of 1959 for 12 vehicles of this design:
Eleven of the twelve initial Delta flights were successful. The total project development and launch cost came to $43 million, $3 million over budget. An order for 14 mour vehicles was let before 1962.Early Delta flights
Delta Evolution
Delta A
Block II MB-3 engine, 170,000lbf vs. 152,000lbf.
14. EPE3Delta B
15. 13dec62. Relay 1, second nasa communications sat. nasa's first active one.
16. 13feb63. pad 17b. Syncom 1. Thiokol Star 13B solid rocket as apogee kick motor.
20. july63? Syncom 2. Geosyncronous orbit, but inclined 33degrees due to the limited performance of the Delta.Delta C
Thrust Augumented Thor
The Thrust Augumented Thor, or TAT, was developed to handle the growing recon sats of the Corona program. It added three Castor solid rocket strapon boosters--each providing 53,000lbs thrust--to the standard Thor core stage. The boosters were lit on the ground and jettisoned after burnout.Delta D
25. 19aug64. Syncom 3. First true Geosyncronous sat.
26. Intelsat 1Delta E
First Delta E. 6nov65. launches GEOS 1.Delta G
1. 14dec66. biosatellite 1.
2. 7sep67. biosatellite 2Delta J
4jul68. Explorer 38.Long Tank Thor
Delta L
Delta M
Delta N
'Super Six'
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