My first major contribution was with Kearfott a division of General Instrument. I worked in the prototype lab building new designs of gyro systems. I also built the prototype for the first depth recorder for small boats.

Then I moved on to Reaction Motors a division of Thiokol Chemical. There I worked with a number of rocket engines. The most memerable to me was the development of the X-15 engine that I worked on from start to finish.

This was a very secret project and when I took this picture, I could have been arrested for bringing a camera to work.
We were very excited when we got up to 13 "shock diamonds".
Shock Diamonds are the bright spots in the exhaust caused by the sound waves reacting with the exhaust gasses.
You can easily see the first four in the above picture. The rest are hard to see as they blend with the sky.
X-15 Engine at the US Air Force Museum at Wright Patterson AFB, Dayton Ohio

The XLR99 was the first large, "man rated," throttleable, restartable liquid propellant rocket engine. The throttle setting could be varied from about 25 percent to 100 percent of thrust, and the restart capability allowed it to be shut down in flight with the assurance that power would again be available later, if needed. The XLR99 was one of the rocket engines used in the X-15 manned research aircraft which was capable of propelling man to the fringes of space.

Developed and built by Reaction Motors Division of Thiokol Chemical Company, the XLR99 could deliver up to 57,000 lbs. of thrust, or the equivalent of about 500,000 horsepower. The propellants for the XLR99 were liquid oxygen (LOX) and anhydrous ammonia, fed into the engine by turbine pumps powered by hydrogen peroxide at a flow rate of more than 10,000 lbs. per minute.

The XLR99 engine had a rated operating life of one hour, after which it could be overhauled and used again, though operating times twice that long were demonstrated in tests. Since the basic X-15 carried fuel for about 83 seconds of full-power flight, and the X-15A-2 carried fuel for more than 150 seconds of full-power flight, each XLR99 was theoretically capable of between 20 and 40 flights before overhaul.

In common with other large scale liquid fueled rocket engines, the walls of the XLR99's thrust chamber were constructed of hollow tubing so that fuel could be routed through the tubes to cool the chamber walls before being burned in the engine. The basic weight of the engine is 910 lbs.

Link to: XLR11 Bell X-1, Republic XF-91 Engine
Link to: More X-15 Information
Link to: How the engine works

The X-15 is perhaps the most ambitious aircraft ever created. It was built to push the limits of flight and explore the possibilities of space travel. During its research program the aircraft set unofficial world speed and altitude records of 4,520 mph (Mach 6.7 on Oct. 3, 1967, with Air Force pilot Pete Knight at the controls) and 354,200 ft (on Aug. 22, 1963, with NASA pilot Joseph Walker in the cockpit).

The WADC helped develop the aircraft in coordination with NACA, the Air Force, and the Navy. In the course of its flight research, the X-15's pilots and instrumentation yielded data for more than 765 research reports.

The X-15 had no landing gear, but rather skidded to a stop in a 200 mph landing on skis. It had reaction controls for attitude control in space, and was a major step on the path toward space exploration. Much of what was learned on the X-15 was applied to the Space Shuttle.

The X-15 program, however, was concerned with much more than just dazzling, ultra-performance records. It generated nearly 800 technical reports on research stimulated by the airplane's development and flight tests, and it had a profound impact on America's manned space program. It demonstrated, for example, that pilots could ably perform under the stresses of hypersonic accelerations, as well as the weightlessness of space. In doing so, it clearly documented man's ability to pilot a rocket-boosted vehicle out of the atmosphere and then perform a lifting reentry upon its return. While offering palpable evidence that piloted reusable spacecraft were a genuine near-term possibility, it was also used as a test bed for a variety of other space-related experiments. The celestial navigation equipment ultimately destined for use in the Apollo program, for example, was first tested on the X-15. Generally considered to be the most productive effort of its kind in history, the X-15 program remains, to this day, the high-water mark for flight research worldwide.

    Specifications of the X-15
      Span: 22 ft. 3 in.
      Length: 50 ft. 3 in.
      Gross weight = 31,275 lbs
      Empty weight = 11,374 lbs
      Engine: Reaction Motors XLR-99 rocket engine, 57,000 lbs. thrust

    PERFORMANCE
      Maximum speed: Mach 6.72, 4,520 mph. (unoffical record by X-15 No. 2)
      Range: Over 250 miles (flight path distance)
      Service Ceiling: 354,200 ft. (unoffical record by X-15 No. 3)

    Total flight time in the program:
      30 hr. 13 mm., 49.2 sec
      Total time above Mach: (cumulative)
      Mach 1: 18 hr. 23 mm. 11.6 sec
      Mach 2: 12 hr. 13 mm. 50 sec
      Mach 3: 8 hr. 51mm. 12.8 sec
      Mach 4: 5 hr. 57 mm. 23.8 sec
      Mach 5: 1 hr. 27 mm. 15.8 sec
      Mach 6: 1 mm. 16.8 sec

    The Pilots
      The 12 pilots of NASA, the Air Force, Navy, and North American Aviation who flew in the
      program are listed in the order of their first flights, along with their total flight numbers.
        A. Scott Crossfleld, NAA, 14 flights
        Joseph A. Walker, NASA, 25 flights
        Robert M. White, USAF, 16 flights
        Forrest S. Petersen, USN, 5 flights
        John B. McKay, NASA, 29 flights
        Robert A. Rushworth, USAF, 34 flights
        Neil A. Armstrong, NASA, 7 flights
        Joe H. Engle, USAF, 16 flights
        Milton 0. Thompson, NASA, 14 flights
        William J. Knight, USAF, 16 flights
        William H. Dana, NASA, 16 flights
        Michael J. Adams, USAF, 7 flights

    The Aircraft Now
      The No. 1 X-15, with a serial number of 56- 6670, is publicly displayed in the National Air and Space Museum, Washington, D.C., next to the Wright Brothers Flyer and the Spirit of St. Louis, flown by Charles Lindbergh.

      The No. 2 X-15, with a serial number of 56- 6671, is publicly displayed at the Air Force Museum, Dayton, Ohio. It is displayed in its original configuration, without the external fuel tanks, though it retains the fuselage extension. The aircraft was delivered to the museum in October 1969.

      The No.3 X- 15, which carried a serial number of 56-6672, was destroyed in a crash on Nov. 17, 1967. The pilot, Air Force Maj. Michael J. Adams, was killed when he lost control in space and was not able to recover.

X15 now residing in the Smithsonian in Washington DC

Rear view complete with engine. The Bell X-1 is in the upper right

Ok, now I know where two of the engines are. We delivered three.
We built a few more but managed to blow up some of them.
I asked where the third engine was. They looked it up on the Intetnet and guess what?
They showed me this web page. I said "Hi, That's my web site".

April 18, 2005
While on vacation I visited the Pima Air and Space Museum in Tucson Arizona
and there next to a mockup of the X-15 was the third engine.
It had been donated with only the information on the plaque so I was able to
enjoy going back about 50 years and explain to the tour guides how it worked.

November 2005, I have just learned that another engine is on display at
Teterboro Airport in New Jersey. (No picture)

February 2006, E-Mail from the Director of the Museum at Edwards Air Force Base

Stumbled on your site while Googling some X-15 stuff. Very interesting and nicely done.
Wasn't sure if you knew that we have two complete XLR-99s (Ser Nos 106 and 107) and a number of thrust chambers in our collection here at the Air Force Flight Test Center Museum at Edwards AFB, CA. We were fortunate enough to get the maintenance and inspection logs on each engine so we could match up which flights each was used on. We had three complete engines at one time but sent one to the Smithsonian.
S/N 107 was used on Joe Engle's and Milt Thompson's first flights, Engle's astronaut wings flight, and it set an unofficial world speed record of Mach 5.92 on 27 Jan 62. We have 107 mounted on a trailer so we can haul it around to airshows and other aerospace events.
S/N 106 had a very distinguished career on the X-15 program from its acceptance in Jan 61 to its last flight in Nov 66. It was used on the first flight of X-15 #3 in Dec 61; on the first powered flight of the #2 X-15 modified to the the X-15A-2 configuration in June 1964; on the first X-15A-2 flight with full external fuel tanks in Jul 66; and-during its last flight on 18 Nov 66-it was used to set an unofficial world's absolute speed record of Mach 6.33 (4250 mph) with William J. "Pete" Knight at the controls. It reached a maximum altitude of 249,000 feet. This engine is on display in our museum.
For more information see the Edwards AFB public site at www.edwards.af.mil Click on "About Edwards" then "Museum" and select the "XLR99 Exhibit."

    Best Regards, DOUG NELSON, Director, AFFTC Museum
    (661) 277-8050 * DSN 527-8050 - "Keepers of the Right Stuff"

If Edwards has 106 and 107 and they gave 105 to the Smithsonian (may be hard to get the S/N as it's in the airframe hanging from the ceiling). That would be the three that completed the contract plus Tuscon, Andrews, Teteboro and the one that we blew up. That would account for 101 through 107 and should be all of them.

September 2006 Update. At the Reaction Motors 15th Biennial Reunion I learned from Ken Gaddis, one of the project engineers, that 10 engines were built. I don't know if the one that blew on the tie-down test at Edwards due to a valve malfunction was recovered. The third X-15 was destroyed in a crash and I have been told that we blew more than one in testing. This would mean that the six that I have listed above are all the ones still in existance.

I have included here the 2006 Reaction Motors Rocket Newsletter rminews06.pdf 16mb.

The 16th Biennial Reunion is scheduled for September 28, 2008 at Zeris Inn, Mountain Lakes, NJ.

I plan on expanding the Reaction Motors information on this site.
Any information you can contribute would be greatly appreciated by everyone.

Here are some links of interest.

  • Reaction Motors in New Jersey
  • "POWER FOR PROGRESS": Reaction Motors, Inc., 1941-1972
  • Viking Rocket


    If you have gotten this far on this page then you must be really interested.
    I have started a page on How the Engine Works [CLICK HERE]

    		•
    Has any one seen this engine?
    No, it's not missing. We just can't find out what it is other than a YLR-48.
    If anyone recognizes it, please let me know. Thanks

    Here are some pictures of the XLR-11 Engine





    X-15 launched


    X-15 in MicroSoft Flight Sim 2004