NASA astronaut Suni Williams watches as Aerojet Rocketdyne test team engineers direct the test-firing of an RL10 engine at the company's facility in West Palm Beach, Florida. The engine will be one of two used for the Centaur upper stage during a United Launch Alliance Atlas V mission to launch Boeing's CST-100 Starliner on a flight test carrying a crew. The engine was test-fired as part of acceptance testing to confirm the engine is ready for flight. Photo credit: NASA/Dimitri Gerondidakis #nasa #explore #ULA #Boeing #Starliner #AtlasV #astronaut #space #commercial #crew #progress