Atlas SLV-3

The Atlas SLV-3, or SLV-3 Atlas was an American expendable launch system derived from the SM-65 Atlas / SM-65D Atlas missile. It was a member of the Atlas family of rockets.

The Atlas SLV-3 was a stage and a half rocket, built as a standardized replacement for earlier Atlas launch systems, which had been derived from the various Atlas missiles.^[1]

Most space launcher variants of the Atlas up to 1965 were derived from the D-series Atlas ICBM with custom modifications for the needs of the particular mission. The SLV-3 would use a standardized configuration based on the Atlas D missile for all launches with the exception of different widths for the top of the rocket depending on the upper stage being flown.^{[2]: 45–46}

The SLV-3 had thicker gauge tank walls to support the weight of upper stages as well as upgraded engines and removal of unneeded ICBM hardware such as retrorockets. Although the main engines had greater thrust, the verniers were detuned slightly in the interest of improved I_SP (vacuum specific impulse).

Variants of the SLV-3 flew until 2005 when the legacy Atlas was retired from service and replaced by the Atlas V, a completely new vehicle with conventional aircraft-style construction and different engines.^[3]