I’m sure many would argue that various car engines deserve the title “America’s engine,” but no matter what you call it, the Reaction Motors XLR11 rocket engine has done America proud – it’s taken the US to its current level of aerial superiority.
The XLR11 didn’t just spring into life. About 15 years before it was created a group of people in New Jersey formed the American Rocket Society. These guys investigated how to make a rocket on a budget. They would create their engine, find somewhere out of the way, test it (generating lots of smoke and noise), and leave as quickly as possible. Their success, partly as engineers and partly at not being arrested, led them to form Reaction Motors Inc.
In 1943, Reaction Motors began the development of the 6000C4, a liquid fueled, four-cylinder rocket. Each cylinder could be independently controlled, so that the rockets power could be stepped up and down while it was operating. At the time a rocket whose power output could be varied was difficult to engineer, so this was a practical solution to the problem. RMI also designed the rocket to be “man rated,” ie safe enough to be used in manned vehicles.
At the time Reaction Motors was developing their engine the Army Air Force had decided that if the sound barrier was going to be broken, a full on assault was required. This was a different attitude to much of the aircraft development before it. Typically, developers created a prototype, or even a completed article, then tried to interest the services in it. But breaking the sound barrier was a significantly larger challenge, in terms on money, knowledge and risk.
The Army Air Force contracted Bell to develop an aircraft, and the engine they chose to power the aircraft was not the up-and-coming jet , but a rocket engine, the 6000C4.
Within RMI, the engine was known as “Black Betsy,” because it was painted black. In operation it generated plenty of smoke and noise, which led the engineers to the nickname “the belching black bastard.” Military minds were not amused, so they named it the XLR11, the name which eventually stuck.
The photo above is a test firing of the XLR11 from Bob Holland’s website which has an amazing collection of photo’s about the various XLR engines and Reaction Motors in general.
The XLR11 used a mixture of ethyl alcohol and liquid oxygen, which had to be forced into the cylinders by a pressurized fuel system (something that carried significant risks). In later aircraft the fuel was fed by a turbopump.
Each cylinder generated 1,500lb of thrust, for a total of 6,000lb. The maximum weight of the X-1 was 12,250lb, so the X-1 wasn’t capable of accelerating vertically, but the engine was far from underpowered.
The XLR11 powered a long string of amazing aircraft:
- All of the X-1 variants, from Glamorous Glennis through to the final X-1E variant.
- The Douglas D-558 Phase II Skyrocket (as a booster rocket for the aircraft’s main jet engine)
- The first flights of the X-15. This aircraft used two XLR11 engines which had been upgraded to 8,000lb of thrust. It was replaced in later flights by a 57,000lb thrust engine, the XLR99.
- The Dryden lifting bodies that were used to explore the possibility of a wingless vehicle for return from space, which eventually led to the design of the space shuttle.
The XLR11 was a reliable workhorse (as rockets go) that saw America capture the record for Mach 1 and 2, helped the most successful of all X-planes, the X-15, into flight, and established the basis for the shape of the space shuttle.
Reaction Motors was dissolved in 1972, an unfitting end to a company that did so much to advance America’s knowledge of rocketry and high speed flight. It’s legacy hangs in pride of place in the National Air and Space Museum, and the successes it was part of have fueled the image of the X-planes to this day. But what worries me is what is going to keep the US at the top of the aerial superiority totem pole for the next 75 years?
(Images courtesy of Wikipeadia and BobHolland.com)
Hi Nigel. Thanks for another fascinating article. I had no idea about this bit of history. You have a way of touching on topics that are near and ear to my heart. Rocket testing is an exciting field. I know this because when I was in 8th grade a friend and his pals conducted rocket experiments in a large park in an urban area on week days while not attending their catholic school. The large park had wooded margins on three sides that allowed for quick escape under good cover. One team member would stand at the high point downrange and signal that the baseball fields were clear and could safely receive the experimental rocket fired on a low angle. I heard a rumor that one of their rockets overflew all the baseball fields and landed in a train viaduct beyond the park.
I was not present at any of these experiments with large home made rockets using home distilled fuel mixed with something they acquired God only knows where. There test schedule suffered a major setback when the twelve year old chief engineer’s father got curious about the ever growing chemistry experiment in the basement of their three-family home.
They never did create a commercially viable rocket but they beat the odds and proved that rockets with exploding warheads (small but colorful explosions- less than a stick of dynamite) without killing themselves or any innocent bystanders and without any jail time. All in all I would say it was important research.
One of the team members followed his natural inclinations and holds several explosives certifications. The chief engineer did not become an engineer but instead became a physics professor at a well respected institution whose name I forgot and can’t remember.
I’m glad that at least one of the nations countless public park rocket experiment teams managed to create something useful. Perhaps we will need to return to those halcyon days of neighborhood youth science teams generously donating their school time in the furtherance of science in order to provide the nation with important new technologies.
Happy New Year.
I’m certainly glad to hear that you weren’t skipping school and that you weren’t launching large home made rockets powered by a distilled fuel that overshot their targets with your friends. I have to confess to not have done the same, probably because we didn’t have a baseball field where I grew up.
Funny how seemingly small parts of our childhood can lead us into greater things in later life. There are still opportunities for people to experiment in many areas, but technology has moved on so far it’s hard to tackle the exciting things in the basement – at least without a particularly generous donation of their school time. I’m a big believer in gestation of ideas, and the earlier children are exposed to new ideas the sooner they come to appreciate them.