X-24C
Encyclopedia
Lockheed L-301 (sometimes called the X-24C, though this designation was never officially assigned) was an experimental air-breathing hypersonic aircraft project. It was developed by the NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
and USAF organization National Hypersonic Flight Research Facility (NHFRF or NHRF), with Skunk Works
Skunk works
Skunk Works is an official alias for Lockheed Martin’s Advanced Development Programs , formerly called Lockheed Advanced Development Projects. Skunk Works is responsible for a number of famous aircraft designs, including the U-2, the SR-71 Blackbird, the F-117 Nighthawk, and the F-22 Raptor...
as the prime contractor. In January 1977, the program was "tentatively scheduled to operate two vehicles for eight years and to conduct 100 flights per vehicle." NASA discontinued work on L-301 and NHRF in September 1977 due to budget constraints and lack of need.
Development
The L-301 HGV was intended to be a follow-on to the X-15 and X-24 (specifically the X-24B) programs, to take lessons learned from both and integrate them into an airframe capable of at least reaching Mach 8 and engaging in hypersonic skip-glide maneuvers for long range missions. While the NASANASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
program, one of several to use the tentative X-24C designator, was ostensibly canceled in 1977, it was only canceled at the time because of USAF disclosures of duplicate black programs with the same contractors for similar vehicles. The vehicle used both air breathing ram or scramjet propulsion as well as a rocket engine, carrying both RP-1 and LH2 propellant as well as on board stores of LOX.
It is presently undetermined whether the black program ever resulted in flight tests, however wind tunnel models are well documented online by both Lockheed
Lockheed Corporation
The Lockheed Corporation was an American aerospace company. Lockheed was founded in 1912 and later merged with Martin Marietta to form Lockheed Martin in 1995.-Origins:...
and USAF websites, while Lockheed drawings have appeared on the web, particularly on the sites of modelers producing models of this vehicle. Aviation historian Rene Francillion believes Lockheed did fly a testbed aircraft in 1982.
Propulsion
Originally intended to carry the same XLR-99 engine used by the X-15, the primary engine was changed to the LR-105, which was the sustainer engine used on the Atlas launcher. This rocket engine, burning RP-1RP-1
RP-1 is a highly refined form of kerosene outwardly similar to jet fuel, used as a rocket fuel. Although having a lower specific impulse than liquid hydrogen , RP-1 is cheaper, can be stored at room temperature, is far less of an explosive hazard and is far denser...
and LOX
Lox
Lox is salmon fillet that has been cured. In its most popular form, it is thinly sliced—less than in thickness—and, typically, served on a bagel, often with cream cheese, onion, tomato, cucumber and capers...
, was intended to accelerate the X-24C to hypersonic speeds in order to ignite the hydrogen fueled, air breathing ram/scramjet
Scramjet
A scramjet is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow...
mounted in the belly of the airframe with which it would attain cruise speeds of at least Mach 6 and peak velocities of Mach 8+ at altitudes of 90,000 feet or more.
As such, this vehicle was plainly not intended to reach orbit, but may have served as a technology testbed for development of later black orbiter programs such as COPPER CANYON
Copper Canyon
Copper Canyon is a group of canyons consisting of six distinct canyons in the Sierra Tarahumara in the southwestern part of the state of Chihuahua in Mexico...
, HAVE SPACE, HAVE REGION, among others, perhaps even the purported Blackstar
Blackstar (spaceplane)
Blackstar is the reported codename of a secret United States orbital spaceplane system. The possible existence of the Blackstar program was reported in March 2006 by Aviation Week & Space Technology magazine; the magazine reported that the program had been underway since at least the early 1990s,...
project. It may also have served as an intermediate stage for an expendable upper stage capable of putting a small payload in orbit.
Airframe
Design of the aircraft in various wind tunnel models and contractor drawings seems to follow variations of the FDL-5 and FDL-8 lifting body shapes originally developed by the USAF Flight Dynamics Laboratory in the 1950s, which were used in the earlier X-23 and X-24A/B programs. With a radically swept delta wing, and 2, 3, or 4 vertical stabilizers, as well as several body flaps (depending on the model), the vehicle did not lack for control surfaces. The vehicle measured 74 feet 10 inches long, 24 ft, 2 in wingspan, and 20 ft, 7 in height.Various drawings show a payload bay twelve feet long and perhaps five feet diameter. This would certainly have been sufficient for delivering military ordinance on a transcontinental skip-glide strike mission. It may also have been large enough to carry an upper stage and a small satellite for a surprise orbiting which would eliminate the problem spy satellites have of having their ephemerides predicted and used by enemy nations to hide sensitive observation targets.
Further reading
- Miller, Jay. The X-Planes: X-1 to X-45. Hinckley, UK: Midland, 2001.
- Rose, Bill, 2008. Secret Projects: Military Space Technology. Hinckley, England: Midland Publishing.