SM-65B Atlas

Atlas B (SM-65B)

Atlas B before the launch of SCORE (USAF)
Function	Prototype ICBM Expendable launch system
Manufacturer	Convair
Country of origin	United States
Launch history
Status	Retired
Launch sites	LC-11, LC-13 & LC-14, CCAFS
Total launches	10
Successes	6
Failures	4
First flight	19 July 1958
Last flight	4 February 1959

The Convair SM-65B Atlas, or Atlas B, also designated X-12 was a prototype of the Atlas missile. First flown on 19 July 1958, the Atlas B was the first version of the Atlas rocket to use the stage and a half design with an operational sustainer engine and jettisonable booster section, in addition to an operational guidance computer. Unlike later Atlas models, the Atlas B used explosive bolts to jettison the booster section.

Ten flights were made. Nine of these were sub-orbital test flights of the Atlas as an Intercontinental Ballistic Missile, with five successful missions and four failures. The seventh flight, launched on 18 December 1958, was used to place the SCORE satellite into low Earth orbit, the first orbital launch conducted by an Atlas rocket.

The B series test program took a considerable amount of delays and frustration, not in the least because the Atlas B was far more complicated than the prototype Atlas A, in fact the first launch would feature all hardware systems found on an operational Atlas, including the sustainer engine, separable booster section, guidance computer, Azusa tracking system, detachable nose cone, and more. The first flight article missile, 3B, was originally planned for launch in May 1958, but the date was set back by endless hardware difficulties, both with the missile itself and the newly-opened LC-11. In addition, Atlas 3B could not be cleared for flight until a successful firing run of Missile 2B was performed at the Sycamore Canyon test stand, which was also experiencing nonstop technical issues. The launch of a third Soviet satellite in April also put further pressure on program planners. Finally on July 19, Missile 3B was launched. Engine start proceeded normally and the launcher release system functioned well. The Atlas performed well until T+21 seconds when the programmer attempted to initiate the pitch and roll maneuver. At this point, the missile began swerving from side to side uncontrollably and finally broke up at the forward end of the LOX tank at T+43 seconds, the thrust section and part of the RP-1 tank remaining in one piece until impact with the ocean. Even before the flight was terminated, technicians had determined the cause of the failure - ground crews had forgotten to power on the yaw gyro during prelaunch preparations. To prevent a recurrence of this, Convair began equipping the gyroscope packages with motion sensors to ensure proper operation, something that would eventually become a standard part of guided missile control systems. Atlas 3B was considered "partially successful" because all other systems had functioned properly until missile destruction.