LOT #50054 |
Starting Bid: $50,000
Thiokol XLR99 Rocket Engine for the North American X-15....
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Description
Powering the Fastest Winged Aircraft in History: Thiokol XLR99 Rocket Engine for the X-15
Thiokol XLR99 Rocket Engine for the North American X-15. An
exceptionally rare Thiokol XLR99 liquid-fueled rocket engine
developed for the North American X-15 hypersonic research aircraft
program jointly funded by NACA (later NASA), the United States Air
Force, and the United States Navy. Developed in the late 1950s, the
XLR99 was the world's first fully throttleable man-rated liquid
rocket engine and among the few large liquid-fueled rocket engines
ever installed in a piloted aircraft. Measuring approximately 6
feet long and 30 inches in diameter, the engine produced
approximately 57,000 pounds of thrust at sea level and more than
60,000 pounds at altitude.The XLR99 powered the X-15 research aircraft during its historic flight test program from 1959 to 1968. Across 199 powered flights, the X-15 program established major advances in hypersonic and spaceflight research and contributed directly to later American space programs including Mercury, Gemini, Apollo, and the Space Shuttle.
On October 3, 1967, X-15 pilot Major William "Pete" Knight flew the X-15A-2 to Mach 6.7 (approximately 4,520 mph), establishing the fastest speed ever achieved by a crewed winged aircraft, a record which remains unbroken. Five X-15 pilots earned astronaut wings during the program, including future Apollo 11 commander Neil Armstrong.
Constructed from high-temperature nickel superalloys including Inconel-X, the XLR99 employed regenerative cooling and thermal barrier coatings to withstand the extreme temperatures generated during operation.
The present engine retains substantial original structure including the regeneratively cooled nozzle section, injector assembly, manifold hardware, and multiple original serialed subassemblies. Visible markings include:
"CHAMBER INJECTOR ASSY. NO. C308238-AM / SERIAL NO. 42"
"C308381 FN / S/N 140"
These markings are consistent with documented aerospace manufacturing and serialized propulsion-system component practices of the period. The engine exhibits oxidation, thermal discoloration, and handling wear consistent with age and fired aerospace hardware.
An extraordinary artifact from the dawn of hypersonic flight and the Space Age, representing one of the most historically significant rocket propulsion systems ever built.
Only available to bidders in the U.S., export restrictions and special shipping arrangements apply.
Auction Info
2026 July 23 - 24 Space Exploration Signature® Auction #6340 (go to Auction Home page)
Proxy Bidding Ends
July
23rd
Thursday
10:50 am CT
Auction Dates
July
23rd-24th
Thursday-Friday
Proxy Bidding Time Remaining
19 Days
2h 8m 12s
Bids + Registered Phone Bidders: 0
Lot Tracking Activity: 42
Page Views: 673
Buyer's Premium per Lot:
25% of the successful bid (minimum $49) per lot.
This lot is in: 1 -
Signature® Floor Session (Live Floor, Live Phone, Mail, Fax, Internet, and Heritage Live):
(Lots 50001-50277) - 11:00 AM Central Time, Thursday, July 23, 2026.
[Proxy bidding ends ten minutes prior to the session start time. Live Proxy bidding on Heritage Live now starts within 2 hours of when the auction opens for proxy bidding and continues through the live session.]
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Additional Location Info:
Heritage Auctions - Dallas
2801 W. Airport Freeway
Dallas, TX 75261
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