Legislation contained in the National Defense Authorization Act says the US must come up with alternatives to the Russian-built RD-180 rocket engine, and an American-made from Aerojet Rocketdyne aims to do just that by by 2019. Dubbed the the AR-1, the Aeroject alternative now in testing uses additive manufacturing processes to build critical injector parts for the engine, and Aerojet has invested some $300 million in research and development to this point on the $25 million a pair engines. Tyler Hickman, the team lead at the NASA Glenn Research Center in Cleveland, says the injectors for the motor are one of the most expensive components in the sophisticated engines, and he say 3D printing them save both time and money. You can read the whole story here: http://3dprint.com/51525/3d-printed-...gine-injectors

Here is a picture of the actual hot-fire testing: