Atlas Rocket: WD-40 Balloon Tanks, John Glenn's Orbit and Russia's RD-180

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WD-40, short for water displacement, 40th formula, was created to keep the Atlas missile's bare, unpainted steel from rusting on the humid launch pads of Cape Canaveral. Convair, a division of General Dynamics, built Atlas as an intercontinental ballistic missile and flew its first successful test in December 1957. It used a stage-and-a-half design: two outboard booster engines and a center sustainer, all burning RP-1 kerosene and liquid oxygen, fired together at liftoff, and the boosters dropped away partway up. The hull was a balloon tank of thin stainless steel with no internal framework, held rigid only by internal pressure, so empty tanks had to be filled with pressurized nitrogen to keep from collapsing. Liquid oxygen boils off and cannot sit fueled in a silo for months, and the last Atlas ICBM squadron came off operational alert in 1965.

In December 1958 the SCORE mission put an entire Atlas weighing nearly 9,000 pounds into orbit with a recorded Christmas greeting from President Eisenhower, the first human voice relayed from space. The Atlas LV-3B carried John Glenn's Friendship 7 into orbit in February 1962. With the hypergolic Agena upper stage, Atlas launched classified CIA and National Reconnaissance Office spy satellites, the Ranger Moon probes and Mariner 2 to Venus; with the liquid hydrogen Centaur, it sent Surveyor landers to the Moon and Mariner missions to Mars. Retired missiles were refurbished for 30 years, launching Block 1 GPS satellites from 1978 to 1985, with the last flying in 1995. The Atlas III and Atlas V used a single Russian RD-180 from NPO Energomash, and the Atlas V switched to a rigid Common Core Booster. After the 2014 annexation of Crimea, Congress restricted RD-180 use, pushing United Launch Alliance to Blue Origin's methane-fueled BE-4 and the new Vulcan rocket.

• Liquid oxygen boils at minus 297 degrees Fahrenheit, so fueling an Atlas for launch was too slow for a quick-response weapon.
• SCORE stood for Signal Communication by Orbiting Relay Equipment, and the shiny orbiting Atlas was visible to the naked eye.
• The Agena's hypergolic propellants ignite on contact, letting the stage shut down, coast and restart reliably in space.
• The Atlas V launched the Mars Reconnaissance Orbiter, the New Horizons probe to Pluto and the Curiosity rover.
• ULA announced the Atlas V's retirement in 2021 with enough stockpiled RD-180 engines for its remaining 29 launch contracts, and Atlas V Heavy and Phase II concepts were scrapped.