Thor is the first operational ballistic missile propagated by the US Air Force (USAF). Named after the Norse lightning god, it was deployed in Great Britain between 1959 and September 1963 as a medium range ballistic missile (IRBM) with thermonuclear warheads. Thor is 65 feet (20 m) in height and 8 feet (2.4 m) in diameter. It was then added in the US IRBM warehouse by Jupiter.
Large families of space launch vehicles - Thor and Delta rockets - are derived from Thor designs. Delta II is still in active service by 2017 and with Atlas and Titan's retirement in the mid-2000s is one of the last surviving "legacy" launch vehicles in the US fleet, derived from the Cold War-era missile system, the other being the Minotaur IV which comes from MX Peacekeeper.
Video PGM-17 Thor
Design and development
Fearing that the Soviet Union would deploy long-range ballistic missiles before the US, in January 1956, the USAF began to develop mid-range ballistic missiles, 1,400 miles (2,400 km). The program runs quickly, and in the first three years, the 20 first Air Force squadrons began operating in the UK. The British deployment carries the codename 'Project Emily'. One of the advantages of the design is that, unlike Jupiter IRBM, Thor can be carried by the USAF cargo aircraft at the time, which makes its deployment faster. Launch facilities can not be transported, and must be built on site. Thor is a measure of pauses, and once the first generation of ICBMs based in the US becomes operational, Thor missiles are quickly retired. The last of the missiles was withdrawn from operational standby in 1963.
A small number of Thors, converted into "Thrust Augmented Delta" launchers, remained in operation in the anti-satellite missile role as Program 437 through April 1975. The missile is based on Johnston Island in the Pacific Ocean and has the ability to destroy satellites in low Earth orbit. With prior warning of upcoming launches, they could destroy Soviet spy satellites soon after orbital insertion. These missiles remain stored, and can be reactivated, although the W-49 Mod 6 warheads were all unloaded in June 1976.
Maps PGM-17 Thor
Initial development
The development of Thor was started by USAF in 1954. The goal is a missile system that can deliver nuclear warheads as far as 1,150 to 2,300 miles (1,850 to 3,700 km) with CEP as far as 2 miles (3.2 km). This range will allow Moscow to be hit from the launch site in the UK.
The initial design study was led by Cmdr. Robert Truax (US Navy) and Dr. Adolph K. Thiel (Ramo-Wooldridge Corporation, formerly of Redstone Arsenal). They refine the specification to IRBM by:
- The distance is 1,750 miles (2,820 km) Diameter
- 8Ã, ft (2.4 m), length 65Ã, ft (20 m) (so it can be carried by Douglas C-124 Globemaster)
- Weight of gross takeoff of 110,000 pounds (50,000 kg)
- The propulsion provided by half the Atlas propulsion engine coming from Navaho (largely due to the lack of alternatives at this early date)
- maximum speed 10.000 mph (4.5Ã, km/s) during upstream upstream
- Inertial guidance system with radio backup (for low vulnerability to enemy interference)
Like Atlas, Thor uses a vernier machine for roll control; they flank the main engine instead of on the missile side.
On November 30, 1955, three companies were given one week to bid on the project: Douglas, Lockheed, and North American Aviation. They were asked to create "a management team that could incorporate technology, skills, abilities, and techniques that existed in 'unprecedented time.' On December 27, 1955, Douglas was awarded a major contract for airframe and integration. The Rocketdyne Division of North American Aviation was awarded a contract machine, the AC Spark Plug main inertial guidance system, Bell Labs backup radio guidance system, and General Electric, the cone/reentry vehicle.
Douglas further refined the design by selecting a locked tank seal (as opposed to initially welded) and a tapered fuel tank to improve aerodynamics. This machine was developed as a direct derivative of the Atlas MA-3 thruster engine. Changes involve the removal of a single chamber and a change of pipeline to allow the engine to enter into the smaller thor part of the thrust. The engine test was performed in March 1956. The first engine model engine was available in June, followed by the first aircraft engine in September. Engine development is complicated by serious turbo problems. Early Thor engines suffered "cushioning", a phenomenon that occurs in altitude as the air thins, causing lubricating oil at the foaming pump and pushing the bearings out of their sockets. When this happens, the turbopump will stop, end the engine impulse. The early Thor test in 1957 used an early version of the LR-79 Rocketdyne engine with a conical thrust room and 135,000 pounds of thrust. By early 1958, it had been replaced by an enhanced model with a bell-shaped chamber and 150,000 pounds of thrust. Thor fully developed IRBM has a thrust of 162,000 pounds.
First launch
The launch of the Thor test is from LC-17 at Cape Canaveral Missile Annex. The development schedule is very solid so plans for Atlas bunker are used to allow timely completion of the facility. However, the LC-17B pad has just been ready for the first test flight.
The first ready flight, Thor, Missile 101, arrived at Cape Canaveral in October 1956. It was established at LC-17B and underwent several propellant loading/disassembling exercises, static burning tests, and a one-month delay while the broken relay had been replaced. The launch finally took place on January 25, 1957. Thor almost failed immediately on takeoff because the engine lost its thrust, fell back onto the pad, and exploded. The engineer could not determine the cause until he saw the prelaunch preparation film showing the crew dragging the LOX filler hose through the sand area. It was concluded that the debris had entered LOX and was contaminated, causing valve failure.
Thor 102 was launched on April 20th. Booster performs normally, but incorrect console readings cause Safety Officer Range to believe that it is heading to the mainland and he starts a 35 second destruction sequence to launch. It was found that the cable tracer console reversed, causing Thor's path to display as opposed to where the missile was headed; the short flight increases the confidence that the plane will fly.
Thor Third launch (Missile 103) did not come out of the pad and exploded four minutes before the planned launch. The damaged valve allows LOX tank pressure to rise to an unsafe level; the accident is also a technician error that does not pay attention to pressure gauges. LC-17B consequently should be fixed for the second time in four months.
Misil 104, launched August 22 of the newly opened LC-17A, broke off at T 92 seconds due to a decrease in signal strength from the programmer, causing the engine to dreadlocks to be true. The guidance system tries to compensate, but ultimately produces an uncontrolled yaw maneuver that causes excessive structural load.
Thor 105 (September 20), 21 months after commencement of construction, flies 1,100 miles (1,800 km) downrange. No telemetry equipment is included in this missile and the heavy savings allow it to reach a total of 1,500 miles (2,400 km).
The 107 (October 3) missile crashed back to LC-17A and exploded at launch because the gas generator valve failed to open.
Missile 108 (October 11), exploded about T 140 seconds without prior warning. Engineers are confused about the cause of the failure. After the first launch of Thor-Able failed six months later due to a confiscated turbopump, it was concluded to be the cause of death 108, although the missile lacks sufficient instrumentation to determine the exact nature of the failure.
Thor's last three tests during 1957 were all successful. 1958 begins with a back-to-back failure. Thor 114 was destroyed by a Range Safety of 150 seconds at launch when the power loss coaching system and the Thor 120 engine died a little under two minutes after takeoff. The telemetry system has experienced power failure during launch, so the reason for cutting the machine can not be determined satisfactorily.
On April 19th, Missile 121 crashed back into LC-17B and exploded, leaving the pad unfeasible for three months. A fall of the fuel line is believed to have been the culprit.
On April 22, Missile 117, carrying the first upper Able stage, lost the thrust and broke off at T 146 seconds due to turbo failure.
The Jupiter, Thor, and Atlas missiles all use the Rocketdyne LR-79 engine variant and all three have failed to launch due to the marginal turbine design. There are two separate problems with the pump. The first is a discovery during testing in Huntsville that lubricating oils tend to foam at high altitudes when air pressure decreases. The other is the vibration of the pump shaft from the operating speed of nearly 10,000 RPM will cause the bearing out of its sockets, so the pump suddenly creeps up. The Army has delayed the launch of Jupiter for four months until turbo issues can be solved, and as a result no more pump failures affect the program.
General Schreiver rejected the idea of ​​sending Thor and Atlas missiles back to the factory and decided that he would only allow modifications on the ground so as not to delay the testing program. He agreed to install the fix for the lubricant problem, which included pressing the turbopump gearbox and using oils with different viscosities that were less susceptible to foaming, but not the modified bearing follower. Six Thor and Atlas launches respectively failed during February-April 1958, though not all of them could be attributed to turbo problems. Then there was no turbopump failure over the next four months, leaving the Air Force with a sense of overconfidence that roughly ended when Thor-Able 127, carrying the world's first lunar probe, exploded during launch on August 17th due to turbo failure. A month later, Atlas 6B also suffered turbopump failure, and after this, the Air Force surrendered and agreed to replace the turbopump on all their missiles, after which there was no more launch failure due to turbo problems. The required modifications to the missile will take only a month and do not cause delays in either the Thor-Able 1 or Atlas 6B flights, so the failure is ultimately associated with poor program management.
Five Thor tests were successfully carried out in June-July 1958, the latter carrying a rat named Wickie on a biological mission; the capsule sinks into the ocean and can not be recovered. Thor 126 (July 26) loses 50 seconds of thrust at launch when the LOX valve is accidentally closed. The vehicle fell and broke off the aerodynamic load. Then on July 30, a tragic accident occurred at the static Thor test booth in Sacramento, California when the LOX valve failed, causing a fire that burned six Douglas technicians, three of whom later succumbed to their injuries.
The Phase II test with the initial Spark Plug AC initial directive began December 7 with the first successful flight on 19 December 1957.
The operational variant of the Thor, DM-18A, began to be tested in the fall of 1958, but Missile 138 (5 November) was out of control shortly after take-off and had to be destroyed. Nevertheless, Thor declared operational and testing now start at Vandenberg Air Force Base on the West Coast when Missile 151 flew successfully on December 16th. On December 30, a close repetition performance of the November 5th failure occurred when Missile 149 lost control and crushed 40 seconds during launch.
After running a successful launch during the first half of 1959, Missile 191, first launched by the Royal Air Force crew, suffered other damage controls when it was launched from the VAFB. This time, the missile pitch and roll program fails to activate and continues to fly straight up. The launch crew initially did nothing because they reasoned that Earth's rotation would gradually pick it up from the ground and they wanted to keep collecting data for as long as possible. Eventually nevertheless, they become nervous about it exploding or streaking, so the destructive command is sent about 50 seconds to the launch. Highland winds cause debris to land in the town of Orcutt near the base. After Thor 203 repeated the same failure four weeks later, the investigation found that the culprit was a safety wire intended to prevent the tape control in the programmer from inadvertently off while assembling the vehicle. The wire will usually be cut after the programmer's installation in the missile, but technician Douglas has forgotten this important step, so the tape can not be rolled and the pitch and roll sequence is not activated. Another 23 Thor missile tests were conducted during 1959, with only one failure, when Missile 185 on December 16, the launch of the second RAF, broke up due to damage control.
Service competition with Jupiter
The Jupiter missile, a joint venture with Chrysler and Redstone Arsenal in Huntsville, Alabama, was originally developed for a submarine launch, but would involve a very risky situation of liquid-fuel rockets stored at the submarine's boundaries. In 1956, the Polaris program was proposed instead, featuring solid-state SLBMs that were much lighter and safer to store. The Navy quickly turned to Polaris and overthrew Jupiter, who was later transferred to the Army as a surface missile.
With two almost identical IRBM capabilities, the Army and Air Force are at loggerheads with each other as it is clear that only one of the two will ultimately achieve operational status. Jupiter's pilot program, which started two months after Thor, went much more smoothly and was spared from an accident like the Thor 103 blast as it was mostly used by experienced rocket team Wernher von Braun. The turbo problem that hit early Rocketdyne machines was also completed in Jupiter much earlier than the Air Force missiles.
Jupiter's program is more successful as well because testing and preparation are much better, for example, each missile is given full-time static shootings in Huntsville before shipping. A static strike for the Thor test was only opened in May 1958, where the missile launch record was standing on four successes and nine failures, including four pad explosions. In comparison, there were only three failures of Jupiter when May 1958 ended (only eight launches occurred against Thor thirteen) without an explosive pad. Thors were given PFRF (Pre Flight Readiness Firing) before launch; this is between 5-15 seconds simply because the launch facility is not designed for full firing duration as a static test booth. Missile 107 has not been given PFRF at all and its release ends with a blast pad.
Thanks to thorough testing conducted in Huntsville, Jupiter missiles mostly arrive at CCAS in ready-to-fly conditions while Thors usually require extensive repairs or modifications before launch.
The panic that plagued the United States after the Soviet Sputnik 1-2 launch in late 1957 caused Defense Secretary Charles Wilson, in his last act before leaving his post, to announce the opposite that both Thor and Jupiter will go into service. It is a fear of Soviet ability and also to avoid political reactions from layoffs in the workplace that would result in either Douglas or Chrysler if either of the two missiles were canceled.
Implementation
The spread of IRBM's fleet to Europe proved more difficult than expected, as no NATO member other than the United Kingdom accepted the offer to place Thor missiles on their land. Italy and Turkey agree to accept Jupiter missiles. Thor was deployed to Britain beginning in August 1958, operated by 20 squadrons of RAF Bomber Command under US-British double key control. The first active unit was the No. 77 RAF Squadron at RAF Feltwell in 1958, with the remaining units becoming active in 1959. All was disabled in September 1963.
All 60 Thor missiles stationed in the UK are based at the launch site above ground. The missiles are stored horizontally in an erector-carrier trailer and covered by a missile shield that can be opened. To fire weapons, the crew used electric motors to roll back the missile shelters, essentially a long warehouse mounted on a steel rail, then using a powerful hydraulic launcher to lift the missile into an upright position to launch. After standing on the launch mountain, the missile was triggered and could be fired. The entire launch sequence, from starting to roll back the missile shield to the ignition of the rocket engine and take-off, takes about 15 minutes. The main engine burn time is almost 2.5 minutes, increasing the missile to a speed of 14,400 ft/s (4,400 m/s). Ten minutes away, the missile reaches a height of 280 miles (450 km), close to its elliptical flight path. At that point the vehicle re-enters separate from the missile body and begins to descend towards the target. Total flight time from launch to impact target is about 18 minutes.
Thor was originally deployed with G.E. Vehicle re-entry Mk 2 'heat sink'. They are then converted into a sleek G.E. Mk 3 ablative RV. Both RVs contain a thermonuclear warhead W-49 with a 1.44 megaton explosion.
The IRBM program was quickly overtaken by the Air Force ICBM program and made redundant. In 1959, with Atlas well on its way to operational status, Thor and Jupiter became obsolete, although both remained operational as missiles until 1963. In retrospect, the IRBM program is a poorly understood idea because it relies on NATO allied cooperation, most of them not want to have nuclear missiles on their lands, and also be surpassed by the ICBM program, but continue for political reasons and a desire to retain labor in their respective assembly plants.
Thor's lasting legacy is not as a missile, but its use as the basis for the Thor/Delta spacecraft family into the 21st century.
Important flights
- June 2, 1962, Bluegill flight failed, tracking lost after launch, Thor and nuclear device destroyed.
- June 19, 1962, Starfish flight failed, Thor and nuclear device destroyed 59 seconds after launch at a height of 30-35,000 feet (9.1-10.668.0 m).
- July 8, 1962, the Thor 195 missile launched the Mk4 rickety vehicle containing the W49 thermonuclear warhead to a height of 250 miles (400 km). The warhead was detonated with a yield of 1.45 Mt TNT (6.07 PJ). This is a Starfish Prime show from the Operation Fishbowl nuclear test series.
- July 25, 1962, failed flight Bluegill Prime, Thor and nuclear devices destroyed on the launch pad, which is contaminated with plutonium.
Launch vehicle
The Thor rocket is also used as a space launch vehicle. It was the first in a large family of space launch vehicles - Delta rockets. The descendants of Thor fly to this day as Delta II and Delta IV.
Operator
Former operator
- United States
- United States Air Force
- RAF South Ruislip
- 705 Strategic Missile Wing (1958-1960)
- United Kingdom
- Royal Air Force
- The RAF Bomber Command
see Project Emily Stations and Squadrons
Specification (PGM-17A)
- Family: Thor IRBM, Thor DM-18 (single stage LV); Thor DSV-2J (rocket 1st stage), Thor DM-21 (rocket 1st stage), Thor DSV-2D, E, F, G (suborbital LV), Thor DSV-2J (orbital launch vehicle).
- Overall length: 19.82 m (65.0 ft)
- Span: 2.74 m (9.0 ft)
- Weight: 49,800 kg (109,800 pounds)
- Empty weight: 3,125 kg (6,889 lb)
- Thrust (vac): 760 kN
- Push Lift (sl): 670 kN (150,000 lbf)
- Isp: 282 s (2,77 kNa, s/kg)
- Isp (sl): 248 s (2,43 kNa, s/kg)
- Burn time: 165 d
- Core diameter: 2.44 m
- Maximum reach: 2,400 km (1,500Ã mi)
- Ceiling: 480 km (300 mi)
- Warhead
- A W49 burst on Mk. 2 vehicles reentered
- warhead mass: 1,000 kg (2,200 pounds)
- Result: equals 1.44 megaton TNT (6.02K)
- CEP: 1 km (0.62 mi, mi)
- Boost Propulsion: Liquid fueled rocket, LOX and Kerosene.
- Engine:
- Rocketdyne LR79-NA-9 (Model S-3D); 666 kN (150000 lbf)
- Vernier: 2x Rocketdyne LR101-NA; 4.5 kN (1000 lbf) each
- Properties: LOX/Kerosene (Propeller Thor kerosene is referred to as 'RP1' by RAF user)
- Thrust (vac): 760 kN
- Isp: 282 s (2,77 kNa, s/kg)
- Isp (sea level): 248 s (2.43 kNa, s/kg)
- Burn time: 165 d
- Mass Engine: 643 kg
- Diameter: 2.44 m
- Room: 1
- Space Pressure: 4.1 MPa
- Area Ratio: 8.00
- Thrust to Weight Ratio: 120.32
- Country: USA
- First Flight: 1958
- Last flight: 1980
- Flown: 145.
- Comments: Designed for amplifier applications. Gas generators, pump-feeds
- Guide: Inertia
- Maximum speed: 17,740 km/h (11,020 mph)
- US Dollar Development Expenses: $ 500 million
- Recurring dollar value: $ 6.25 million
- Total Total Created: 224
- Total Development Created: 64
- Total Production Built: 160
- Flyaway Unit Fee: US $ 750,000 in 1958 dollars
- Launches: 59
- Failure: 14
- Success Rate: 76.27%
- Date of First Launch: January 25, 1957
- Date Last Launch: November 5, 1975
Also see
- Project Emily
- Strategic Air Command
- Thor (rocket family)
- Thor-Able
- Thor-Agena
- Thor-Delta
Related list
- List of US military aircraft
- Missile list
References
External links
- Thor from Encyclopedia Astronautica
- Thor's IRBM History Site
- The History of the Delta Launcher's Vehicle
- The British missile launch site on the Secret Bases website
- UK Distribution Thor in Lincolnshire
- Maxwell Hunter, "Father of Thor Rocket"
- "YouTube contemporary film from Thor missiles at North Pickenham"
Source of the article : Wikipedia
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