SM-65E Atlas

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Atlas-E (SM-65E)
Atlas-E.jpg
Launch of an Atlas-E missile
Function ICBM
Expendable launch system
Manufacturer Convair
Country of origin United States
Launch history
Status Retired
Launch sites LC-11 & 13 CCAFS
OSTF-1, LC-576 & SLC-3, VAFB
Total launches 48
Successes 33
Failures 15
First flight 11 October 1960
Last flight 24 March 1995

The SM-65E Atlas, or Atlas-E, was an operational variant of the Atlas missile. It first flew on 11 October 1960, and was deployed as an operational ICBM from September 1961 until April 1966. Following retirement as an ICBM, the Atlas-E, along with the Atlas-F, was refurbished for orbital launches as the Atlas E/F.[1] The last Atlas E/F launch was conducted on 24 March 1995, using a rocket which had originally been built as an Atlas-E.

As fully operational ICBMs, the Atlas E and F (which differed only in guidance systems) had upgraded engines and inertial control instead of the Atlas D's radio ground guidance. The ignition system was also different from the one used on the D-series, which used a "wet" start, meaning that the propellants were injected into the combustion chamber prior to ignition, and a hypergolic igniter on the fully developed version. The Atlas E/F for comparison used pyrotechnic cartridges and a dry start (ignition coming before propellant injection) for an extremely rapid ignition that required no hold-down time on the pad to prevent combustion instability.

Atlas-E launches were conducted from Cape Canaveral Air Force Station, at Launch Complexes 11 and 13, and Vandenberg Air Force Base at OSTF-1, LC-576 and SLC-3.[1]

The first Atlas E launch attempt was carried out from LC-13 at Cape Canaveral on October 11, 1960. It and the second launch on November 30 both failed due to loss of sustainer engine hydraulic pressure at around one minute into the flights due to valve malfunctions during booster staging. Flight #3 on January 24, 1961 was lost due to an electrical short that disabled the vernier engines. The fourth attempt on February 24 was successful. Another electrical glitch occurred in the fifth Atlas E launch on March 14 which led to premature fuel depletion. The sixth attempt (March 25) failed to stage its booster section because of a valve problem.

After two successful Atlas E flights in May, testing at Vandenberg AFB in California began. On June 7, an attempt to launch Missile 27E from a coffin silo failed when the vehicle suffered combustion instability and exploded at liftoff, putting the pad out of commission for six months. This was followed by another failure at Cape Canaveral two weeks later when a spilled gyroscope caused Missile 17E to go out of control and break up 30 seconds after liftoff.

As the June 1961 accident had curtailed launches at Vandenberg until Complex OSFT-1 could be repaired, subsequent Atlas E flights during the year took place from Cape Canaveral and most of them were successful (Missile 26E in September lost thrust at staging due to another valve problem). But in November, an attempt to launch a biological mission (Missile 32E) with a squirrel monkey named Goliath ended in disaster as the Atlas's sustainer engine and verniers shut down almost immediately at liftoff. The booster engines managed to retain attitude control until a fire broke out in the engine compartment and caused the right booster engine to shut down at T+22 seconds (the left engine continued to operate until missile destruction) followed by loss of electrical power and telemetry. The Atlas began tumbling uncontrollably and was destroyed by Range Safety at T+35 seconds. Goliath, who was in a padded container with no restraints, was recovered from the Atlantic Ocean three days later. A postmortem examination of the monkey found that he had died of multiple head injuries probably caused by impact with the ocean rather than separation of the capsule from the booster. Had the flight succeeded, Goliath would have been sent on a 5000 mile (8045 kilometer) suborbital lob and recovered in the South Atlantic. The accident was found to be the result of an improperly installed pressure transducer that prevented the sustainer LOX regulator from working. Despite these mishaps, the Atlas E was declared operational that month.[2]

The Atlas E and F were phased out of use as operational ICBMs in 1965 and replaced by the hypergolically-fueled Titan II. Decommissioned Atlas missiles were then used for military satellite launches from Vandenberg AFB well into the 1990s, sometimes with solid-fueled upper stages, sometimes not. These Atlases should be not be confused with the Atlas H which flew five times during the 1980s and was a standard Atlas SLV-3 (descendant of the original Atlas D) flown with solid upper stages.

The last-ever failure of an Atlas caused by the booster itself (as opposed to the upper stages or other external factors) was an attempted launch of a military GPS satellite on December 19, 1981 using Missile 76E. The right booster engine shut down seconds after liftoff, causing the Atlas to spin out of control and disintegrate. It then plowed into the ground leaving a burnt crater only a few hundred feet from Launch Complex SLC3E. Since no range safety action had been taken, the common bulkhead between the RP-1 and LOX tanks ruptured at impact, allowing the booster's nearly full fuel load to mix and turn into an explosive gel, which detonated with the force of 20,000 pounds of TNT. Investigation of the booster debris quickly pinpointed the cause of the problem; a botched repair job on a rubber O-ring that caused sealant to plug up ventilation holes in the gas generator, which overpressurized and ruptured shortly after ignition. Escaping flames then burned through a LOX feed line, starving the B-1 engine of oxidizer.

The final Atlas E launch (Missile 45E launched on March 24, 1995) successfully carried a weather satellite aloft for the Air Force. A total of 64 Atlas Es were launched between 1960 and 1995, 30 of them being space launches. 16 launches failed.

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