Spaceflight Insider

RL10 test paves the way for future Starliner flights

Commercial Crew Program (CCP) astronauts visit Aerojet Rocketdyne to see RL10 engine test.

Commercial Crew Program (CCP) astronauts visit Aerojet Rocketdyne to see RL10 engine test. Photo Credit: NASA / Dimitri Gerondidakis

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.

An RL10 engine stands in a vacuum chamber at Aerojet Rocketdyne's test stand in West Palm Beach, Florida. Photo credit: NASA/Dimitri Gerondidakis

RL10 engine. (Click to enlarge) Photo Credit: NASA / Dimitri Gerondidakis

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.”

NASA astronauts Barry "Butch" Wilmore, from left, Eric Boe and Suni Williams survey an RL10 engine as it stands in a vacuum chamber at Aerojet Rocketdyne's test stand in West Palm Beach, Florida. Photo credit: NASA/Dimitri Gerondidakis

From left: NASA astronauts Barry “Butch” Wilmore, Eric Boe, and Suni Williams survey an RL10 engine as it stands in a vacuum chamber at Aerojet Rocketdyne’s test stand in West Palm Beach, Florida. Photo Credit: NASA / Dimitri Gerondidakis

NASA astronaut Eric Boe 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. Credits: NASA/Dimitri Gerondidakis

NASA astronaut Eric Boe 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. Photo Credit: NASA / Dimitri Gerondidakis

NASA astronauts Suni Williams, from left, Eric Boe and Barry "Butch" Wilmore listen as an Aerojet Rocketdyne engineer details the injector plate of an RL10 engine.

NASA astronauts Suni Williams, from left, Eric Boe, and Barry “Butch” Wilmore listen as an Aerojet Rocketdyne engineer details the injector plate of an RL10 engine. Photo credit: NASA / Dimitri Gerondidakis

Commercial Crew Program (CCP) astronauts visit Aerojet Rocketdyne to see RL10 engine test.

NASA astronaut Eric Boe 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. Photo Credit: NASA / Dimitri Gerondidakis

Video Courtesy of NASA Kennedy

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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.

Reader Comments

Development for the RL-10 engine began in the 1950s. In that it is still flying illustrates how government impedes progress. Though the RL-10 is a fine engine, it is utterly obsolete. Its craftsmanship manufacturing methods make the engine wildly expensive. It should have been replaced decades ago.

Numerous attempts in the past and present have been made to replace RL-10 with something modern. The RL-60, Raptor, RL-10B-X, MB-60, Next Generation Engine (NGE), BE-3U, and XCOR to name a few.

The lack of vision, political will or just general bureaucratic inertia has keep this ancient engine flying and it is a testament to a broken system.

I believe AJR had prior engines that they could have offered, and stopped development on. No business case, no vision, whatever it may be. Pointing at the government is overly simplistic, and disregards the other factors that likely were in play.

Ultimately though, yes it can come down to “We don’t want it” stopping a product. And that’s Business 101, don’t spend money on something that isn’t wanted.

Richard Sommery-Gade

Lack of funding developed a make do reality, which is why our flights now originate from Russia for the most part. Political insanity is hurting us in too many ways.

David A Greenidge

I’m just a space nerd and not an engineer. What would a better engine look like?

Dave, that is a very complex question that can be scratched on in many written pages. To put it simply it depends on what you want. The RL-60 project of the early 2000s offered an easier to manufacture engine with less parts that was man rated with 65 Klbf as a replacement for the RL10.

More revolutionary is Advanced Cryogenic Evolved Stage that utilizes a lightweight internal combustion engine to use propellant boil-off to operate the stage including production of power, maintaining stage attitude and keeping the propellant tanks pressurized, eliminating the need for hydrazine fuel and liquid helium.

Another possibility is the Raptor or BE-3. Both engines use Methane as fuel and are reusable and constructed with modern manufacturing methods.

By the way David here is a reference and status update on the RL-60 engine prior to the program being shelved: http://www.alternatewars.com/BBOW/Space_Engines/RL60.pdf

It discusses its improvements over the RL-10.

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