RL10 test paves the way for future Starliner flights
Inside a vast vacuum chamber in West Palm Beach, Florida, Aerojet Rocketdyne tested one of the RL10 engines that will carry the first Boeing CST-100 Starliner spacecraft into orbit. This successful test run was conducted to evaluate the engine’s performance prior to shipping it to the United Launch Alliance (ULA) facility in Decatur, Alabama, for integration with the Atlas V upper stage.
Three NASA astronauts assigned to the Commercial Crew program—Eric Boe, Sunita Williams, and Barry “Butch” Wilmore—watched frost and icicles build up on the engine bell and components as cryogenic liquid hydrogen and liquid oxygen flowed through the system during the six-minute firing. The test included a shutdown and restart in vacuum, which will occur during an actual mission. According to Boe, “Today’s test was just amazing and from what it looked like, it looked flawless.”
The venerable RL10 engine, which has powered launch vehicle upper stages since the 1960s, had not been “human rated” until now. However, in the next two years, it will be serving as the upper-stage engine for both the CST-100 flights as well as NASA’s Orion spacecraft aboard the Space Launch System.
Human rating of rocket engines generally means including backup systems for additional reliability as well as high-quality standards for construction. The difference between human-rated and non-human rated engines is sometimes more art than science. However, the goal of standards like NASA Procedural Requirement (NPR) 8705.2b is to provide guidance to ensure that extra bit of safety NASA desires before sending astronauts into space.
Over 500 RL10s have been built and over 400 missions have flown the engine successfully—including the Voyager 1 and New Horizons spacecraft. As Matthew Bullivant, Aerojet Rocketdyne’s lead engineer for RL10 integration put it, “The last thing for RL10s to do is put people into space.”
The astronauts expressed great enthusiasm after the test. Butch Wilmore said, “My first impression was that everything was by the book and the team showed great attention to detail, which is what you have to do in this business, otherwise bad things happen.”
The first flight test of CST-100, which will not carry a crew, is scheduled for 2017. According to Space News, the first crewed flight has been delayed until 2018 in response to some technical issues and requirement changes.
NASA’s Commercial Crew astronauts are upbeat about the program’s progress and the RL10. Suni Williams, who flew to the International Space Station twice, said, “When you go through the whole process, seeing the test and seeing the professionals out here building the engines, there was no doubt the test would be a success.”
Video Courtesy of NASA Kennedy
Bart Leahy is a freelance technical writer living in Orlando, Florida. Leahy's diverse career has included work for The Walt Disney Company, NASA, the Department of Defense, Nissan, a number of commercial space companies, small businesses, nonprofits, as well as the Science Cheerleaders.