The 550th Strategic Missile Squadron (550 SMS) is an inactive United States Air Force unit. It was last assigned to the 310th Strategic Aerospace Wing, stationed at Shilling AFB, Kansas
The 550 SMS was equipped with the SM-65F Atlas Intercontinental ballistic missile (ICBM), with a mission of nuclear deterrence. The squadron was inactivated as part of the phaseout of the Atlas ICBM on 25 June 1965.
Activated in late 1942 as a B-17 Flying Fortress heavy bomb squadron, trained under Second Air Force. Deployed to England in the European Theater of Operations (ETO) during June 1943, assigned to VIII Bomber Command as a strategic bombardment squadron. Participated in the air offensive over Nazi Germany and Occupied Europe until German capitulation in May 1945. Personnel demobilized in England and returned to the United States; squadron reassigned to Second Air Force and was programmed to be re-equipped with B-29 Superfortresses for deployment to Pacific Theater. Japanese capitulation led to units inactivation in September 1945, being neither manned or equipped.
Effective 15 September 1947, the squadron was activated at Selfridge Field, Michigan. Having been allotted to the organized reserves, with assignment to Second Air Force, Air Defense Command, it was redesigned as a B-29 very heavy bombardment unit on 25 August. In August 1948, the squadron was assigned to the Tenth Air Force, which in December, became a part of the Continental Air Command. On 1 December 1948 it was again reassigned to Air Defense Command where it remained on reserve service until being inactivated on 27 June 1949 due to budget restrictions.
Reactivated in 1961 as a Strategic Air Command SM-65F Atlas ICBM launch squadron, stationed at Shilling AFB, Kansas and assigned to the 310th Bombardment (later Strategic Aerospace) Wing on 1 July 1961. The activation of the 550th SMA along with the 551st Strategic Missile Squadron at Lincoln AFB, Nebraska, on April 1, 1961, marked the first standing up of Atlas F units. The squadron was assigned twelve missiles, based in a 1 x 12 configuration: twelve independent widely dispersed launch sites comprised the missile squadron. In June 1962, the first operational sites for the Atlas F ICBMs were accepted by SAC and in September the squadron was declared operational. In the following month during the Cuban Missile Crisis, the 550th received orders to maintain all 12 missiles on alert status.
The Atlas F was the final and most advanced version of the Atlas ICBM and was stored in a vertical position inside underground concrete and steel silos. When stored, the Atlas F sat atop an elevator. If a missile was placed on alert, it was fueled with RP-1 (kerosene) liquid fuel, which could be stored inside the missile for extended periods. If a decision was made to launch the missile, the missile was raised to the surface and the liquid oxygen tank was filled. The launch would occur shortly after completion of this process. (see below for site details).
The exposure on the surface that this procedure entailed was the great weakness of the Atlas F. It was exposed and vulnerable during this time. The Titan II and Minuteman missiles could be launched from within their silos, thereby eliminating this vulnerability. Also, since the Titan did not use a cryogenic fuel or oxydizer, and the Minuteman was a solid fuel rocket, they could be stored fully fueled and ready to launch within a very few minutes.
On December 1, 1964, the first Atlas F missile at Shilling was removed from alert status in favor of the more advanced LGM-25C Titan II; squadron was inactivated on 25 June 1965. Missile sites were later sold off to private ownership after demilitarization.Constituted as 550th Bombardment Squadron (Heavy) on 25 November 1942
Activated on 1 December 1942
Inactivated on 28 August 1945
Re-designated 550th Bombardment Squadron (Very Heavy) on 25 August 1947
Activated in the reserve on 15 September 1947
Inactivated on 27 June 1949
Re-designated 550th Strategic Missile Squadron, and activated, on 22 July 1960
Organized on 1 April 1961
Inactivated on 25 June 1965
385th Bombardment Group, 1 December 1942 – 28 August 1945
ETO Fuselage Code: HG
Second Air Force, 15 September 1947
Tenth Air Force, 1 July 1948
First Air Force, 15 August 1948
Tenth Air Force, 1 December 1948 – 27 June 1949
Strategic Air Command, 22 July 1960
310th Bombardment (later Strategic Aerospace) Wing, 1 April 1961 – 25 June 1965
B-17 Flying Fortress, 1942–1945
B-29 Superfortress, 1947-1949.
SM-65F Atlas Missile, 1961–1965
Operated twelve missile sites of one missile at each site (12 total):