||It has been suggested that Atlas SLV-3, Atlas LV-3B and Atlas-Agena be merged into this article. (Discuss) Proposed since October 2013.|
Launch sequence of an Atlas D ICBM test, April 22, 1960
Expendable launch system
|Country of origin||United States|
|Launch sites||LC-11, 12, 13 & 14, CCAFS
|First flight||April 14, 1959|
|Last flight||November 7, 1967|
The SM-65D Atlas, or Atlas D, was the first operational version of the U.S. Atlas missile. Atlas D was first used as an intercontinental ballistic missile (ICBM) to deliver a nuclear weapon payload on a suborbital trajectory. It was later developed as a launch vehicle to carry a payload to low Earth orbit on its own, and later to geosynchronous orbit, to the Moon, Venus, or Mars with the Agena or Centaur upper stage.
The Atlas D testing program began with the launch of Vehicle 3D from LC-13 on April 14, 1959. At liftoff, the LOX fill/drain valve failed to close, resulting in a steady oxidizer leak and loss of pressure to the propellant feed system. The right booster engine was thus starved of oxidizer and so only reached 75% thrust level. In addition, LOX spilling down the side of the missile exploded on contact with the engine, damaging it. The Atlas lifted and flew at an oblique angle until T+26 seconds when an explosion in the boattail caused the right booster engine to separate from the vehicle. The burning missile pitched over and with all control lost, the Range Safety Officer issued the destruct command at T+35 seconds.
On May 18, Atlas 7D was prepared for a night launch. The test was conducted with the Mercury astronauts in attendance in order to showcase the vehicle that would take them into orbit, but 60 seconds of flight ended in another explosion, prompting Gus Grissom to remark "Are we really going to get on top of one of those things?". This failure was traced to improper separation of a pin on the right launcher hold-down arm, which damaged the B-2 nacelle door and caused helium pressurization gas to escape during ascent. Around one minute into the launch, the RP-1 tank lost pressure and the intermediate bulkhead between it and the LOX tank ruptured, causing the complete destruction of the missile.
Atlas 5D (June 6) destroyed itself a minute and a half into the flight due to another episode of tank pressurization being lost and the RP-1 bulkhead reversing itself and rupturing, but this time caused by a valve failing to close after separation of the booster engines. The fifth test on July 29 was successful, and after another flight on August 11, the Atlas D was reluctantly declared operational. Subsequent tests in the fall and winter all performed well including the first Atlas launch from Vandenberg Air Force Base on September 9, although the launch of a boilerplate Mercury capsule on Atlas 10D (Big Joe) in September was a partial success because the booster engines failed to separate.
With this string of successful Atlas tests, including twin launches from Cape Canaveral and VAFB within hours of each other on January 26-27, 1960, NASA, Convair, and the Air Force were lulled into a sense of security that ended on March 13, 1960 when Atlas 51D suffered combustion instability and was destroyed by Range Safety only three seconds after liftoff. A second disaster occurred on April 8 when 48D experienced the same problem, but this time failed to make it off the pad before exploding, severely damaging it in the ensuing holocaust. With two launch facilities now in need of repair, attention shifted to LC-12 where Atlas 56D flew over 9000 miles with an instrumented nose cone, impacting the Indian Ocean.
On May 6, 1960 Atlas 23D lifted from 576B-1, a coffin silo, at VAFB and began experiencing abnormal pitch gyrations within 10 seconds of launch. After about 20 seconds, the missile started tumbling out of control upon which the RSO sent the destruct command. The next flight, 74D (July 22) broke up 70 seconds into its flight due to another control malfunction. Missile 33D (September 29) failed to stage its booster section and 81D (October 13) destroyed itself a minute into launch after the LOX tank overpressurized and ruptured the intermediate bulkhead. Eventually, it was discovered that the Atlas silos at VAFB had been constructed improperly with two pad umbilicals attached to the wrong location. This had caused the gyroscope packages in Missiles 23D and 74D to short out and led to other malfunctions in Missiles 33D and 81D.
The majority of failures after this point were high altitude or partial. Atlas 91D's successful launch on January 23, 1961 concluded the R&D phase of the Atlas D program. After an operational test in March 1963 (Missile 102D) suffered another control failure and RSO destruct shortly after liftoff, it was noted that the vehicle used a Type B gyro canister and all previous Atlases with them (Missiles 3B, 23D, 74D, and 17E) had failed as well. Another two missiles in VAFB's inventory were found to have these gyroscope packages, so they were promptly replaced with spares from the Mercury program and no guidance or control problems affected them during their flights.
Most Atlas D launches were sub-orbital missile tests; however several were used for other missions, including orbital launches of manned Mercury, and unmanned OV1 spacecraft. Two were also used as sounding rockets as part of Project FIRE. A number were also used with upper stages, such as the RM-81 Agena, to launch satellites.
The Atlas D was deployed in limited numbers as an ICBM due to its radio guidance while the fully operational E and F-series missiles had inertial guidance packages and a different ignition system that allowed faster engine starts.
Atlas Ds used for space launches were custom-built for the needs of the mission they were performing, but when the Atlas was retired from missile service in 1965, Convair introduced a standardized Atlas vehicle (the SLV-3) for all space missions. Remaining D-series missiles were flown until 1967 for suborbital tests of reentry vehicles and a few space launches.
A total of 116 D-series missiles (not including vehicles used for space launches) were flown from 1959-67 with 26 failures.
The warhead of the Atlas D was originally the G.E. Mk 2 "heat sink" re-entry vehicle (RV) with a W49 thermonuclear weapon, combined weight 3,700 lb (1,680 kg) and yield of 1.44 megatons (Mt). The W-49 was later placed in a Mk 3 ablative RV, combined weight 2,420 lb (1,100 kg) The Atlas E and F had an AVCO Mk 4 RV containing a W-38 thermonuclear bomb with a yield of 3.75 Mt which was fuzed for either air burst or contact burst. The Mk 4 RV also deployed penetration aids in the form of mylar balloons which replicated the radar signature of the Mk 4 RV. The Mk 4 plus W-38 had a combined weight of 4,050 lb (1,840 kg).
- Encyclopedia Astronautica - Atlas