Toward the end of the last century, U.S. development of large liquid-propellant rocket engines had come to a complete standstill. As pointed out by then-NASA Administrator Dan Goldin, the only such engine developed by the U.S. in the previous three decades had been the space shuttle main engine (SSME). Thus was the stage set for the introduction of Russian rocket technology. In April 1992, the president of Russian engine developer Energomash visited General Dynamics Space Systems Division (GDSSD), builder of the venerable Atlas vehicle that had launched our first astronauts into orbit. He told division president Mike Wynne that for $100,000 Energomash would design and develop for the Atlas a half-scale derivative of the RD-170, which was a 1.7-million-lb-thrust liquid oxygen (Lox)-kerosene first-stage engine for Zenit and Energia. Since Atlas 2’s three Rocketdyne MA-5A engines, with a combined thrust of only 490,000 lb, were barely able to get the Atlas-2 off the pad, Wynne understandably jumped at the chance to obtain access at such low cost to Russia’s proven oxygen-rich closed-cycle technology in an engine that would deliver 860,000 lb of thrust at 15-20% higher efficiency than the MA-5A. Thus was born the RD-180, which first flew on an Atlas 3 in 2000. In 1997 GDSSD successor Lockheed Martin (LM) ordered 101 RD-180s from Energomash for about $1 billion and negotiated an exclusive agreement for U.S. sales. But LM’s biggest customer for the subsequent Atlas 5 was the USAF, which was not happy with relying on a Russian-built engine for half its Evolved Expendable Launch Vehicle fleet. So Energomash teamed with Pratt & Whitney to create a U.S. company, RD Amross, to duplicate RD-180 production. However, Amross had great difficulty getting the detailed specifications for materials and machining processes, because although the Russian documentation was truly meticulous (each part had a ‘passport’ that accompaniedit through every step in manufacture), it was very different from U.S. practice. Moreover, much of the detailed materials information and ‘tricks’ of the machining processes were in the heads of the skilled Russian workmen, to which Amross did not have access. So although Amross remains the U.S. marketing agent for Energomashproduced RD-180s, it never achieved the desired U.S. manufacturing capability. Nevertheless, the RD-180’s great success (43 flawless launches on Atlas 3 and 5) stimulated Orbital Sciences to file suit last June against United Launch Alliance, which had inherited parent LM’s exclusivity agreement for RD-180s. Orbital would like the RD-180 for its new Antares launcher, which currently uses a derivative of the other mainstream Russian Lox-kerosene engine, the NK-33, modified and currently being sold by Aerojet-Rocketdyne as the AJ-26. But where are the U.S. engines in this now highly restricted field of opportunity?The only current candidates are Rocketdyne’s remodeled SSMEs slated for the new Space Launch System and the RS-68s currently used on Boeing’s Delta 4. But both these are fueled by liquid hydrogen, which has operational limitations compared with kerosene. The only new Lox-kerosene prospects on the horizon are the current attempt by Aerojet Rocketdyne and Dynetics to resurrect the half-century-old Apollo-era F-1, and the far-future million-lb-thrust AJ-1E6 engine concept being promoted by Aerojet Rocketdyne for the eventual upgrade of the yet-to-be-born SLS. Not much of a heritage for a once-dominant U.S. technology. Could it be because there’s only one U.S. liquid-propellant rocket company left? Jerry Grey Editor-at-Large