Author Topic: Thor Booster Variants  (Read 18953 times)

Offline edkyle99

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Re: Thor Booster Variants
« Reply #40 on: 09/08/2016 02:39 AM »
Thor-Agena D used a "standardized" Agena D upper stage that was designed to fly atop Thor, Atlas, and Titan with minimal changes.

Agena D used an improved Bell 8096 restartable engine, still producing 7.26 tonnes thrust but now with higher specific impulse.  It also used a Bell Telephone Laboratories (BTL) 600 radio guidance system. 

Thor-Agena D flew 21 times during 1962 to 1967 from Vandenberg AFB pads 75-1-1, 75-1-2, 75-3-4 and 75-3-5, carrying Keyhole 4 and 5 film return spysats, DSAP Block 1 military weather satellites, Poppy electronic intelligence satellites, and experimental U.S.Navy satellites among others.  Four launches failed, and a fifth placed Poppy 1A/1B in a too-high orbit when Agena failed to cut off as planned.  The satellites still functioned, but the orbit limited data collection.

 - Ed Kyle
« Last Edit: 09/08/2016 02:40 AM by edkyle99 »

Offline Chrup4

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Re: Thor Booster Variants
« Reply #41 on: 09/08/2016 02:25 PM »
Thor-Agena D used a "standardized" Agena D upper stage that was designed to fly atop Thor, Atlas, and Titan with minimal changes.

Yes, the Agena A and B were all custom built for the mission and launch vehicle they were used with; Agena D was an attempt to create one standard configuration. It did improve overall reliability even though quite a few Agena failures still occurred in the mid-to-late 60s.

The Atlases were also custom built for each space mission, although the basic design of them was derived from the Atlas D missile. After the failure of Mariner 1 and five consecutive Ranger probes (plus a string of failed DoD launches from the West Coast), a board of inquiry was established that recommended one standardized Atlas for all space launches, as well as better assembly, checkout, and prelaunch procedures. NASA frequently complained about the poor quality control on Atlases and the numerous repairs and hardware modifications they needed before launch, though some of that no doubt went hand-in-hand with the hapless Convair technicians having to memorize the technical details for about 20 different flavors of Atlas. This eventually led to the Atlas SLV-3, which arrived in 1965 as the Atlas ICBM program was ending and replaced the multitude of earlier Atlas variants. The SLV-3 was basically an Atlas D core with thicker tank walls to support the weight of upper stages, as well as uprated engines.

The Soviet program did the same thing with the R-7; after it was retired from ICBM use, they settled on one standardized model instead of the numerous R-7 models flying pre-1965.
« Last Edit: 09/08/2016 05:06 PM by Chrup4 »

Offline Jim

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Re: Thor Booster Variants
« Reply #42 on: 09/08/2016 02:57 PM »
The SLV-3 was basically an Atlas D core with thicker tank walls to support the weight of upper stages, as well as uprated engines.

There was more to it.  Standardized avionics with different guidance systems for each coast. Standardized electrical interfaces for upper stage or payloads. 

Offline edkyle99

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Re: Thor Booster Variants
« Reply #43 on: 09/13/2016 04:20 PM »
NASA/Goddard couldn't ignore the success of the original twelve Thor-Deltas, so it ordered more.  These featured incremental improvements, introduced pretty much "one at a time".  The method worked.  Only 2 of these 24 Deltas would fail outright.

Delta A introduced MB-3 Block 2 engines that produced 170 klbf liftoff thrust.  Delta A, which flew twice in 1962, also featured a shorter interstage between Thor and Able to shave weight.  The improved Delta actually stood 4 to 5 feet shorter than the original Thor-Delta. 

Delta B, which flew nine times during 1962-64, introduced a 36 inch second stage stretch and improved AJ-10 engine performance.  This variant launched Explorer 17, TIROS 7 and 8, Relay 1 and 2, Telstar 2, and Syncom 1 and 2.  Syncom 1 was the first launch to GTO, though the satellite was lost during its apogee motor firing.  Syncom 2 succeeded, reaching an inclined geosynchronous orbit.     

Delta C added a more powerful ABL X-258 “Altair 2” third stage during its 11 flight, 1963-67 run.  It orbited more Explorers and a string of early solar observatories and weather satellites.  Remarkably, Delta boosted the TIROS 9 and 10 and ESSA 1 weathersats into near sun synchronous orbits - from Cape Canaveral, Florida!  The flight paths doglegged south, crossing Cuba and Panama before the third stage fired over the equator just northwest of South America to complete the insertion. (Delta would not fly from Vandenberg AFB until 1966.)

Delta C1 added an even more potent United Technologies FW-4D third stage motor during its two launches.  Delta 64, the 38th and final Thor-Delta with the 32 inch diameter Vanguard-derived second stage, orbited NASA’s fifth Orbiting Solar Observatory (OSO 5) on January 22, 1969.  This was the final Thor-Delta to fly without strap-on solid motors.  The old Vangaurd stage scored its 37th consecutive "Delta" orbital success on that flight, a relic of the early Space Age surviving to fly even after NASA had launched astronauts atop massive Saturn V boosters a few miles up the Florida coast.

 - Ed Kyle
« Last Edit: 09/13/2016 06:23 PM by edkyle99 »

Offline edkyle99

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Re: Thor Booster Variants
« Reply #44 on: 09/19/2016 02:44 PM »
Thrust Augmented Thor Agena B/D

Thor-Agena was beefed up with the addition of three Thiokol Castor 1 solid rocket motors beginning in 1963.  These "Thrust Augmented Thor" (or TAT) boosters lifted two Agena B, and 61 Agena D, stages with payloads toward orbit from 1963 until 1968.  The Castor 1 motors, derived from the Sergeant missile motor, nearly doubled the liftoff thrust compared to Thor-Agena.  The solids burned for about 40 seconds, with the last dozen seconds comprising a tailoff.  They were jettisoned at T+65 seconds to reach a safe drop zone.  The boosters augmented the upgraded MB-3 Block 3 Thor first stage engine, which itself burned for nearly 150 seconds.

TAT-Agena D would become the most-oft flown U.S. Air Force Thor space launch vehicle.  It could lift roughly 1.5 tonnes to polar orbit, including the Agena stage.  The vehicle's busiest year was 1964, when 20 launches occurred from Vandenberg.

Five pads, 75-1-1, 75-1-2, 75-3-4, 75-3-5, and PA-1-1, a former Atlas Agena pad on the U.S. Navy test facility at Point Arguello (incorporated into Vandenberg as South Vandenberg after 1964), handled TAT Agena D launches. 

For the first time, Keyhole 4A imaging satellites equipped with two film return "buckets" were flown, accounting for the majority of launches.  TAT-Agena D also orbited electronic intelligence satellites, the Quill 1 experimental radar mapping satellite, and three NASA payloads (OGO 2 and 4 and PAGEOS).  TAT-Agena B orbited NASA's NIMBUS 2.   

 - Ed Kyle
« Last Edit: 09/19/2016 08:02 PM by edkyle99 »

Offline Vlong

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Re: Thor Booster Variants
« Reply #45 on: 09/20/2016 01:50 AM »
Ed might like to know that I found a couple of mistakes/omissions on his Space Launch Report failure list.

1. Pioneer launch 8/17/58--"Thor turbopump T+28 seconds, RSO"

This event happened at 77 seconds and there was no RSO action; the Thor destroyed itself.

2. Corona 67 3/24/64--"Failed to orbit"

The Agena suffered a power failure (this happened several times on T-A launches).

3. Corona 99 R&D 9/2/65--"Agena failed, RSO"

This was the famous failure where high wind pushed the booster off its flight path and debris fell on a trailer. The payload, a mishmash of scientific experiments dubbed MPRV, had nothing to do with the Corona program.

4. Corona 108 5/2/66--"Failed to orbit"

The Agena failed to separate from the Thor and the entire vehicle fell into the Pacific Ocean.

5. Corona 141 2/17/71--"Failed to orbit"

This was the launch mentioned earlier in the thread where an improper prelaunch procedure resulted in the Thor experiencing turbopump failure shortly after liftoff.

Offline edkyle99

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Re: Thor Booster Variants
« Reply #46 on: 09/20/2016 03:54 AM »
Ed might like to know that I found a couple of mistakes/omissions on his Space Launch Report failure list.

1. Pioneer launch 8/17/58--"Thor turbopump T+28 seconds, RSO"
[etc.]
Definitely need to update those lists.  I started that project in 1998.  Much of that information has been updated by declassification, etc., since.

 - Ed Kyle

Offline Vlong

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Re: Thor Booster Variants
« Reply #47 on: 09/20/2016 04:26 AM »
Definitely need to update those lists.  I started that project in 1998.  Much of that information has been updated by declassification, etc., since.

The Air Force was vague about DoD mission failures before the '80s, sometimes not even admitting they happened at all. Which makes it all the more strange that the February '71 Thor failure was widely known for years and Astronautix had the full details about it. However, the fact that it was a low-altitude failure would have made it harder to hide than an event that occurred late in the launch.

Also as one more addition, Gambit 20 on 7/12/65. This was reported for years as an Atlas control failure and RSO destruct shortly after liftoff, but it has since been revealed that the sustainer engine accidentally shut down due to a computer malfunction, causing the Atlas to plunge into the ocean some 680 miles downrange.

Offline edkyle99

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Re: Thor Booster Variants
« Reply #48 on: 09/25/2016 06:59 PM »
Thors lofted six ASSET (Aerothermodynamic/elastic Structural Systems Environmental Tests) lifting body reentry experiments on suborbital flights from Cape Canaveral/Cape Kennedy during 1963-65.  These were U.S. Air Force missions that evaluated reusable, maneuverable, re-entry vehicle designs that might be able to fly to a precise landing point on earth.  McDonnell Aircraft of St. Louis built the ASSET vehicles.  The original reason for the program was to support X-20 development, but ASSET continued after X-20 was cancelled.  One of the ASSET reentry vehicles was recovered after parachuting to an ocean landing.  Two other recoveries were attempted.  Significant telemetry hauls were made even when the vehicles were not recovered. 

Single-stage Thors, retired UK IRBMs returned to Tulsa, Oklahoma for refurbishment, performed three of the flights as "DSV-2F" variants.  Two-stage vehicles that also used retired Thor first stages topped by what were essentially Delta B type second stages performed the other three flights, as "DSV-2G/Delta" vehicles.  The Delta second stage was only partially loaded with propellant for a relatively short 50-60 second burn.  The only mission failure occurred during the first DSV-2G launch when the second stage failed to ignite.  The final ASSET launch on February 22, 1965 was the last U.S. Air Force Thor flown from Cape Canaveral.

 - Ed Kyle
« Last Edit: 09/25/2016 07:05 PM by edkyle99 »

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Re: Thor Booster Variants
« Reply #49 on: 09/26/2016 01:43 PM »

3. Corona 99 R&D 9/2/65--"Agena failed, RSO"

This was the famous failure where high wind pushed the booster off its flight path and debris fell on a trailer. The payload, a mishmash of scientific experiments dubbed MPRV, had nothing to do with the Corona program.
 

Well, it wasn't a standard recoverable CORONA but the launch is included in the declassified CORONA documents
as being officially part of the CORONA program, as was 1962's still-very-poorly-documented STARAD. I agree
they had little to do with the rest of the CORONA program.
-----------------------------

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Offline edkyle99

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Re: Thor Booster Variants
« Reply #50 on: 10/05/2016 01:24 AM »
Thor DSV-2J vehicles were retired Thor DM-18A IRBMs that were refurbished for use in ASAT Program 437 and its follow-ons.  A total of 17 of these Thors performed suborbital flights between 1964 and 1975.  The launches were from two Johnston Island launch emplacements originally built for Operation Fishbowl. 

Program 437 Thors were designed to pass within 3 nmi of an orbiting satellite where the missile's 1.44 mT W49 warhead would destroy the satellite.  Test launches were performed with dummy warheads against orbiting U.S. upper stages and satellites.  A total of nine launches took place.  During the initial tests, two Thors would be counted down simultaneously to ensure that at least one would meet the short launch window.  (A sizable staff was required.  Personnel rotated between Johnston Island and a training pad at Vandenberg AFB.)  The ASAT system stood active watch from 1964 until 1970 (longer than Thors had stood IRBM duty), then was placed on disassembled standby until 1975.

Program 437AP (Alternate Payload) carried a camera system rather than a warhead, to photograph orbiting satellites.  The camera and film reentry vehicle was adapted from Corona KH-4.  Only four launches took place during 1965-66, two of which apparently succeeded in photographing orbiting U.S. objects.

After the ASAT program stood down, two one-off launches took place in 1970.  The first, for Program 922 (former 437Y) was an ABM sensor test against a Minuteman 2 RV launched toward Kwajalein.  The Thor shut down 6 seconds early, preventing an intercept, which would not have occurred regardless because, first, the payload and Thor collided after separation and, second, the Minuteman RV failed to separate from its upper stage!  I haven't seen any photos of this Thor, but it was said to have a separable maneuvering payload. 

The second launch, for the High Altitude Program (HAP), was completely successful.  This Thor's heavy payload, which created a simulated nuclear explosion for an on-board X-ray detector to sense, was housed in an Agena-like shroud, which required installation of a special service tower at LE-2.  (I wonder if the tower might also have supported the 922 launch.)  A reentry pod returned film or data or both.

After four years of non activity, Johnston Island hosted two final Thor launches in 1975.  These BMDTTP (Ballistic Missile Defense Test Target Program) launches served as targets for Kwajalein ABM radars.  I haven't seen any photos of these vehicles, but I have read one report that they were in their IRBM configuration.  They were the final suborbital Thor launches.

 - Ed Kyle
« Last Edit: 10/05/2016 02:42 PM by edkyle99 »

Offline Michel Van

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Re: Thor Booster Variants
« Reply #51 on: 10/05/2016 08:13 AM »
so far i know used BMDTTP standard Thor IRBM
also for Operation Fishbowl (High altitude Nuclear bomb test)
https://en.wikipedia.org/wiki/Operation_Fishbowl

Offline edkyle99

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Re: Thor Booster Variants
« Reply #52 on: 10/10/2016 07:19 PM »
Goddard Center adopted solid motor thrust augmentation to Delta about 1.5 years after it was proven by the U.S. Air Force TAT-Agena D.  Adding three Castor 1 SRMs to the DSV-3C Delta C model created "Delta D" (DSV-3D), also known as "Thrust Augmented Delta" (TAD).  The engine skirt and engine section were slightly modified to support the SRM loads.  TAD jumped off its pad with a nearly 2.37 thrust to weight ratio.  This variant only flew twice, but both launches were historic. 

Delta 25 boosted Syncom 3 to GTO on August 19, 1964.  The extra boost allowed for a 16.5 deg GTO.  Syncom 3's own apogee kick motor and thrusters then had enough energy to boost itself into the first-ever geostationary orbit.  The satellite was positioned above the International Date Line, where it relayed coverage of the 1964 Tokyo Olympics.   

Delta 30 performed a similar launch, on April 6, 1965, for "Early Bird", the first commercial communications satellite.  Early Bird, or Intelsat 1, was similar to the first three Syncoms, but provided 240 telephone circuit equivalent service (or one TV channel).  This garbage-can size satellite substantially increased trans-Atlantic circuit capacity, decisively changing how long-range telecommunication service would subsequently be provided.  Early Bird functioned for four years before being retired.

 - Ed Kyle
« Last Edit: 10/26/2016 05:25 PM by edkyle99 »

Offline edkyle99

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Re: Thor Booster Variants
« Reply #53 on: 10/21/2016 12:40 PM »
Thor Burner 1 (originally "Thor Altair"), was developed to orbit Defense Meterological Satellite Program missions (originally Defense Satellite or Systems Application Program) to support NRO Corona missions.  The early DSAP satellites, built by RCA, were derived from the original TIROS spinners.  Scout, intended to launch these satellites, was still struggling at the time (three of five DSAP launches failed), so plans were made to top refurbished retired Thor IRBMs with Scout "Altair" fourth stages and payload "heat shields".  The move was costly for LTV and NASA, which saw eight planned Scout launches canceled.

Two types of motors and heat shields ended up flying atop Thor Burner 1.  The first two, in 1965, used Lockheed/Grand Central Rocket Co. MG-18 motors and 25.7 inch diameter heat shields from the two already built Scouts assigned to the program.  The final four in 1965-66 used UTC FW-4S Altair 3 motors and 34 inch diameter heat shields. 

Douglas Aircraft replaced the Thor guidance section with a shorter, lighter set of adapters and swapped inertial for lighter BTL radio guidance.  The company also added a cold gas attitude control system atop Thor to provide stability during the coast to apogee and the proper attitude for second stage spin-up and separation.  I'm looking for details on this system, which might only have been used by the FW-4S vehicles that went to higher orbits.

Launches took place from VAFB 4300 B6 (former 75-2-6, later SLC 10W) to boost the tiny satellites into sun synchronous orbits.  SAC's 4300 support squadron performed the launches.  Four of the six launches were successful.  The payload heat shield failed to separate during the first launch and the second stage motor failed to start during the fifth flight.

Subsequent "Thor Burner 2" types continued the DMSP launches until 1980, as we shall see.

 - Ed Kyle
« Last Edit: 10/23/2016 02:58 PM by edkyle99 »

Offline edkyle99

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Re: Thor Booster Variants
« Reply #54 on: 10/23/2016 02:33 PM »
I've updated the Thor-Altair (Burner) card and discussion in the previous message.  I wonder if anyone knows more about the cold gas attitude control system that Douglas added atop Thor to allow a coast before second stage spin-up (possibly only for the FW-4S upper stages).  Was this on an adapter section that separated from Thor, or did Thor stay attached during the coast?  Surprisingly little information on the Internet about this. 

There was an Air Force history by Captains Richard L. Geer, James F. Roberts, and Calvin H. Markwood titled “Development of the Burner Space Launch Vehicles,” that was written for the Space Systems Division Air Force Systems Command in 1966, but I can't find it online.

In the NRO weather satellite history by Hall, there is an interesting note by Captain Geer.  He said that Douglas Aircraft Company put the new launch vehicle “on the front burner”, thus the name “Burner". 

 - Ed Kyle
« Last Edit: 10/23/2016 02:45 PM by edkyle99 »

Offline edkyle99

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Re: Thor Booster Variants
« Reply #55 on: 10/26/2016 04:10 AM »
After Thrust Augmented Delta, the next logical step was to take advantage of all that thrust by increasing the second stage mass.  That step, taken in 1965, created Thrust Augmented Improved Delta (TAID).  Douglas borrowed the Able Star tanks, stretched them, and added an improved AJ10-118E engine to create the second stage.  This roughly doubled the burn time compared to the previous Vanguard-based Delta stage, increasing payload to orbit.  The TAID second stages performed a single burn, then provided attitude control during a coast prior to spin-up and separation of the third stage.   

Both Castor 1 and Castor 2 motors could be used with the TAID series.  Castor 2 provided slightly less liftoff thrust but burned slightly longer.  An MB-3 Block 3 Rocketdyne engine powered Improved Delta's Thor first stage.   MB-3-3 improved reliability and a bit more thrust. 

Third stage options included the ABL-258 and FW-4D spin-stabilized solid motors.  With ABL-258, Improved Delta was called "Delta E".  With FW-4D it was "Delta E1".  The rocket was identified as "Delta G" when no third stage was used. "Delta J", with a Star 37D third stage motor, flew once.  (Unflown types included "Delta F/F1", which was Delta E/E1 without SRMs, and "Delta H", which was Delta G without SRMs.)  An Agena-style 65 inch diameter payload fairing topped the rocket, providing much more internal volume than earlier Delta shrouds.

Twenty six TAID launches took place during 1965-71.  Every single one succeeded.  Launches took place from Cape Canaveral and Vandenberg AFB, marking Delta's introduction to the West Coast.

Payloads included Intelsat 2 communication satellites, NASA Explorer and Pioneer satellites, ESSA weather satellites, HEOS 1, ISIS 1-2, and Biosat 1-2.  The Intelsats separated into GTO and raised themselves into GEO.  The Pioneers went into solar orbits.  Most of the Explorers were launched into highly elliptical Earth orbits.  Explorer 35 (IMP-E) inserted itself into lunar orbit after a precise TAID launch.  Delta boosted HEOS 1 into a 440 x 230,000 km x 28.3 deg orbit.  The satellite's apogee kick motor subsequently raised its perigee to 6,800 km.

TAID was the first Delta to sport the soon-familiar "Delta" triangle logo.

 - Ed Kyle
« Last Edit: 10/26/2016 05:16 PM by edkyle99 »

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Re: Thor Booster Variants
« Reply #56 on: 10/26/2016 03:55 PM »
Just wanted to give some thanks for compiling all of this, Ed.  You can really see how Thor became the Delta we know today.

Offline edkyle99

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Re: Thor Booster Variants
« Reply #57 on: 11/01/2016 07:27 PM »
In 1961, Douglas Aircraft proposed a series of Thor upgrades for space launch.  The "Thor Advanced" (Thorad) concept called for a constant diameter airframe that would eliminate the tapered IRBM LOX tank and increase propellant capacity.  Three Sergeant solid motors would augment thrust.  Before Thorad would fly, Douglas would add the solids to a standard Thor to create "Thorad Junior" (better known as TAT Agena-D).  Replacing the MB-3-3 engine with a higher thrust Saturn H-1 engine would create "Thorad B".  These proposals were eventually realized. 

Thorad-Agena D (also Long Tank Thrust Augmented Thor-Agena D), had the constant 96 inch diameter airframe and a 14 foot stretch.  Stage weight increased 45% to nearly 70 tonnes and burn time increased to 218 seconds MECO/227 seconds VECO.  Three Castor 2 SRMs roughly doubled the liftoff thrust provided by the first stage engine.  A new adapter section topped the stage, allowing continued use of the existing transition section and Agena D adapter.  This resulted in a distinctive three-step taper between the first and second stages.

There were 43 Thorad Agena D launches, with three failures, from Vandenberg AFB between 1966 and 1972.  Launches took place from SLC 1W, 1E, 2E, and 3W, the former 75-3-4, 75-3-5, 75-1-1, and PA-1-1.  Payloads included double bucket Keyhole 4A and 4B satellites, Poppy and Strawman signals intelligence satellites, Nimbus weather satellites, OGO 8, and the remarkable SERT 2.

The Nimbus satellites were powered by SNAP-19 RTGs.  On May 18, 1968, Nimbus B was lost when Thorad's control system failed about two minutes into the flight.  Unlike earlier SNAP RTGs, SNAP-19 was designed to survive launch vehicle failure, and it did.  The RTG was eventually salvaged from the Pacific and its nuclear material reused.

Two Thorad-Agena D variants are listed.  SLV-2G (1966-71) used a DSV-2L first stage.  SLV-2H (1969-72) used a DSV-2L-1A first stage. The stages were identical in external appearance.  It is possible that the "1A" was only added to differentiate Thorad-Agena D from Thorad-Delta (which used the DSV-2L-1B stage).  At the time, newly merged McDonnell Douglas was shifting manufacturing from the original Santa Monica Thor factory to Huntington Beach, where the Thorad stages came off a common production line.

Thor 571, launched May 25, 1972, was the final Thorad-Agena D and the last U.S. Air Force Thor-based stage manufactured, although space launches of converted Thor IRBM missiles would continue for several more years. 

 - Ed Kyle
« Last Edit: 11/01/2016 07:32 PM by edkyle99 »

Offline edkyle99

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Re: Thor Booster Variants
« Reply #58 on: 11/15/2016 05:30 PM »
In March 1964, the DMSP program office approved plans to develop a more powerful Thor Burner 2 launch vehicle that still used repatriated Thor IRBMs. 

Burner 2 used a Thiokol Star 37B motor (TE-M-364-2, a modified Surveyor retro-rocket motor) to power the "Burner 2" second stage.  Boeing's Burner 2 stage was built around the Star 37B.  It had a strap-down inertial guidance system and a 3-axis reaction control system, allowing it to coast without spin stabilization. Four 10 kgf hot-gas hydrogen peroxide thrusters performed stage separation, provided pitch and yaw reaction control thrust during the Star 37B motor firing, and completed a vernier maneuver immediately after the Star 37B burn.   Eight 1 kgf gaseous nitrogen cold-gas thrusters on the stage provided pitch-yaw-roll attitude control during coast and performed spacecraft spinup and post-spacecraft separation maneuvers.  Thor Burner 2 was topped by a new Goodyear conical phenolic shroud that enclosed the upper stage and payload.  The unpainted fairing was distinctively vermilion (orange-red) in color. 

Thor Burner 2 flew 12 times from September 16, 1966 to June 8, 1971, carrying 10 DMSP Block 4 and 5A satellites and performing a pair of U.S. Air Force Space Test Program (STP) missions.  All 12 launches were successful.  One of the STP missions, flown on June 29, 1967, used a Star 13A apogee kick motor to insert Aurora 1 and SECOR 9 into a 3,792 x 3,947 km x 90.1 deg polar orbit.

Thor Burner 2A added a third stage and a modified fairing to the Thor Burner 2 design.   A Star 26B motor served as the third stage motor.  The 3-axis Burner 2A control bus was built around the Star 26B.  A Star 37B motor served as the second stage, with the 3rd stage bus providing guidance and control during its burn.  The shroud was extended by the addition of a cylindrical section.  Thor-Burner 2A performed eight launches with DMSP Block 5B and 5C satellites between October 14, 1971 and February 19, 1976. 

The final launch failed because the Thor was not loaded with enough kerosene fuel, causing Thor to burn out a few seconds early.  The upper stages performed their burns, but the end result was insufficient velocity to maintain a stable orbit.  A old mixture ratio typographical error on the LR79 main engine certification testing data sheet was deemed responsible for the improper fuel load.
See:  http://www.thespacereview.com/article/1287/1

 - Ed Kyle
« Last Edit: 11/15/2016 05:40 PM by edkyle99 »

Offline edkyle99

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Re: Thor Booster Variants
« Reply #59 on: 12/02/2016 09:55 PM »
Long Tank Thor Delta

In 1968, NASA gained access to the stretched Long Tank Thor stage already proven as an Agena booster.  Long Tank Thor served as the first stage for Delta Models L, M, N, M6, and N6, which all used the TAID second stage.  L, M, and N used a trio of Castor 2 strap-on solid motors to augment liftoff thrust.  M6 and N6 used six SRMs with three ground-lit and three air-lit.  All motors jettisonned in sets of three beginning after T+90 seconds.

Delta L used the FW-4D third stage motor.  Delta M, the most often-flown Long Tank Thor Delta model,  used the more powerful Star 37D third stage motor.  Delta N did not have a third stage. Deltas M6 and N6 were the six SRM versions (also called "Super Six") of Deltas M and N.

Delta 58, an "N" carrying the Tiros 17 weather satellite from Vandenberg on August 16, 1968, was the first Long Tank Thor Delta (also called "Thorad Delta" or "Long Tank Thrust Augmented Thor Delta").  Altogether, there were twenty-four L, M, N, M6, and N6 flights, with four failures, during 1968-72. They launched eight Intelsat 3, two Skynet 1, two NATO 2, two ESSA, two OSO, and three ITOS/NOAA satellites.  Single launches included HEOS 2, IMP I (Explorer 43), Biosat 3, and TD-1A.

Delta 59, the first "M" with Intelsat 3-1, failed on September 18, 1968 from Cape Kennedy.  The rocket suffered a pitch rate gyro failure that became noticeable about 20 seconds after liftoff.  It began to break up at T+102 seconds.  The range safety officer sent a destruct command 6 seconds later.

Delta 71, another M, left Intelsat 3-5 in a useless orbit on July 25, 1969 when its Star 37D third stage motor either suffered a motor case rupture or a nozzle failure during its burn.

Delta 73, the first Delta L, failed on August 27, 1969 when it attempted to launch Pioneer E from the Cape.  This time the culprit was an unstable high pressure relief valve in the MB-3-3 first stage power pack.  Pressure fluctuations caused a line to rupture and leak hydraulic oil.  First stage main engine gimbal control was lost 213 seconds after liftoff, during the latter portion of the first stage burn.  The second stage separated and ignited, but was too far off course to make up the lost velocity.  Range safety sent a destruct command at T+ 8 minutes 3 seconds.

Delta 86, an N6, failed on October 21, 1971 when its second stage suffered an oxidizer leak.  The stage tumbled out of control after its attitude control system fought the side thrust from the leak.  The control system finally used up its supply of control gas.   

Delta 85, an N, nearly failed after launched from the Cape on September 29, 1971 with OSO 7.  During the AJ10-118E second stage engine's second burn, the stage suffered a control system failure, caused by a nitrogen pressure leak that cascaded into a main engine gimbal thrust vector control (TVC) hydraulic pressure decay.  (The hydraulic pump was run by pressurized nitrogen gas during the coast phase prior to the burn.)  The stage tumbled, but it and OSO-7 still managed to achieve a usable low earth orbit.  Ground crews stablized OSO 7 after it separated, a "save" that allowed it to perform its mission.

Delta 88, launched on March 12, 1972 with Europe's TD-1A science satellite, was the last "N" and the final launch from Vandenberg AFB SLC 2E.  Delta 88 used a transitional Long Tank stage equipped with the first "Universal Boat Tail" - a beefed up aft thrust structure equipped with mounting points for nine solid motors.  The change was part of the transition from Long Tank to Extended Long Tank Delta that began in 1972.

Two transitional Long Tank Thor Delta models flew in 1972-73.  Delta 300 used three Castor 2 strap on boosters and a modified second stage powered by a more-powerful AJ10-118F engine derived from the Titan 3 Aerojet Improved Transtage Engine Program (ITIP).  It burned nitrogen tetroxide and Aerozine 50 (a 50-50 mix of UDMH and hydrazine) rather than the previous nitric acid/UDMH.  Delta 900 used nine Castor 2 boosters (six ground-lit) and the same second stage.  Both models used the Universal Boat Tail.  Neither flew with a third stage. Both used the Delta Inertial Guidance System (DIGS).  Prior Deltas had used radio-inertial guidance. 

Three Delta 300 and two Delta 900 launches took place from Vandenberg AFB.  One (Delta 96) failed to orbit ITOS E from Vandenberg on July 16, 1973 when a hydraulic pump failed 270 seconds after the second stage ignited.  The pump failure led to loss of thrust vector control.  Successes included NOAA 2 and 3, ERTS 1, and Nimbus 5.

Long Tank Thor ended service as an Air Force Agena launcher on May 25, 1972.  The final Long Tank Thor Delta launch occurred several months later on November 6, 1973 when Delta 98, a Delta 300 model, orbited NOAA 3 from Vandenberg's still-active SLC 2W.

Long Tank Thor Summary

During seven years of service, 72 Long Tank Thor launches occurred, boosting 29 Delta and 43 Agena missions.  Long Tank served as the basis for the follow-on Extended Long Tank Delta stage.

 - Ed Kyle
« Last Edit: 12/02/2016 09:58 PM by edkyle99 »

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