Martin Marietta X-24A / X-24B
Martin Marietta · Lifting Body Research · USA · Early Jet (1946–1969)
The Martin Marietta X-24 was the third pair of heavyweight piloted lifting bodies flown at NASA Dryden between 1969 and 1975 — alongside the Northrop M2-F2/M2-F3 and Northrop HL-10. The same airframe served as both the X-24A and, after extensive rebuilding, the X-24B; together they made 64 flights and contributed the final piece of the lifting-body data set that the Space Shuttle Orbiter's approach-and-landing programme drew on.
The X-24A had a bulbous, ovoid "bathtub" shape with three vertical fins (one centreline, two outboard). It was built for the joint USAF/NASA PILOT programme to evaluate piloted reentry from a SV-5D Martin X-23 PRIME capsule shape. First flight came on 17 April 1969 with USAF Maj. Jerauld Gentry; 28 flights followed through 4 June 1971. Top speed: Mach 1.6, ceiling 71,400 ft. Like the M2-F2/M2-F3 and HL-10, the X-24A was air-launched from NASA's NB-52B mother ship at 45,000 ft and landed unpowered on Rogers Dry Lake.
The X-24B was the same physical airframe with a completely new fuselage shell built around the original cockpit and engine — a long, flat-bottomed delta planform with sharper leading edges and a much higher hypersonic lift-to-drag ratio than the X-24A's bathtub shape. First flight 1 August 1973 with USAF Lt. Col. Mike Love; 36 flights through 26 November 1975. The X-24B reached Mach 1.76 and 74,100 ft. Most importantly, on 5 August 1975 USAF Maj. Mike Love made the first runway landing by a lifting body — touching down on the concrete strip at Edwards rather than on the lakebed, exactly as the Shuttle would later do at Kennedy Space Center.
The X-24B's runway landings — a precision deadstick approach from 60° glide slope, flared at the last moment to roughly 200 mph touchdown — proved that the Space Shuttle could be landed unpowered on a conventional runway. The data set was used directly in the Shuttle's Approach and Landing Test programme with Enterprise in 1977. The X-24B is preserved at the National Museum of the United States Air Force at Wright-Patterson AFB; an X-24A mockup (the X-24A airframe was destroyed in the rebuild) is also on display at the museum.
For Kids — a shorter, friendlier version
The Martin Marietta X-24 was a strange experimental American plane shaped like a bathtub with wings. It was a 'lifting body' — a plane that gets lift from its body shape instead of from regular wings. The X-24 helped NASA test ideas for the Space Shuttle.
The same plane flew as the X-24A and then was rebuilt as the X-24B. Together the two versions made 64 flights between 1969 and 1975. The pilot sat in the front of the bathtub shape. Three small fins on top kept the plane stable.
The X-24A had a chubby oval shape with three vertical fins. After 28 flights, the plane was rebuilt with a sleeker shape and renamed the X-24B. The X-24B had a flat-bottomed wedge shape that looked even more like a small spacecraft.
The X-24's top speed was faster than the speed of sound. It is about as long as a city bus. Both X-24 versions were dropped from a B-52 mother plane at high altitude. The X-24 helped prove that the Space Shuttle could glide safely back to a runway after returning from space.
Fun Facts
- The X-24 was shaped like a flying bathtub with wings.
- It was a lifting body — a plane that gets lift from its body shape, not from wings.
- The same X-24 flew first as the X-24A and was later rebuilt as the X-24B.
- Together the X-24A and X-24B made 64 flights between 1969 and 1975.
- Both X-24 versions were dropped from a B-52 mother plane at high altitude.
- The X-24 helped prove that the Space Shuttle could glide back to a runway.
Kids’ Questions
What is a lifting body?
A lifting body is a plane that gets its lift from the shape of its body, not from regular wings. Most planes have thin wings sticking out to the sides. A lifting body has a fat body shaped to push air down and lift up. This idea is useful for spacecraft that need to come back through the atmosphere, because thin wings would burn off during reentry.
How did the X-24 help the Space Shuttle?
The Space Shuttle returned from space as a glider — it had no engines for landing. NASA needed to know that a heavy, stubby spacecraft could really glide safely to a runway. The X-24 and other lifting bodies like the M2-F2 and HL-10 proved it could be done, giving NASA the confidence to fly the Space Shuttle in 1981.
Variants
- X-24A
- Bulbous "bathtub" lifting body, 1969-1971. 28 flights, top speed Mach 1.6, ceiling 71,400 ft. Airframe rebuilt as X-24B in 1972. Mockup displayed at the National Museum of the USAF.
- X-24B
- Same airframe, new fuselage shell. Long flat-bottomed delta planform, 1973-1975. 36 flights, Mach 1.76, 74,100 ft. First lifting-body runway landing 5 August 1975. Preserved at the National Museum of the USAF.
Notable Operators
- United States Air Force
- Funded the X-24 programme through the Flight Dynamics Lab at Wright-Patterson AFB. USAF test pilots — Gentry, Love, Manke, McMurtry — flew most of the envelope-expansion sorties from Edwards AFB.
- NASA
- Co-sponsored the programme and supplied the NB-52B mother ship. NASA Dryden test pilots John Manke and Bill Dana flew several sorties; the data fed straight into the Space Shuttle approach-and-landing flight envelope.
Frequently Asked Questions
What does PILOT stand for in the X-24 programme?
Piloted Low-speed Tests — the joint USAF/NASA programme that evaluated whether a lifting-body re-entry capsule could be controllably flown to a runway landing rather than requiring parachute splashdown. Ran from 1963 to 1975. Both X-24 configurations were the airborne test articles.
How was the X-24B different from the X-24A?
Same airframe under the skin — the original cockpit, engine (XLR-11 rocket), and main systems were retained. The X-24B added a completely new long, flat-bottomed delta-planform outer fuselage that gave a much higher hypersonic lift-to-drag ratio. Visually the two are unrelated; mechanically they share most internal components.
What was the first lifting-body runway landing?
USAF Maj. Mike Love landed the X-24B on the concrete runway at Edwards AFB on 5 August 1975 — the first time any lifting body had touched down on a conventional runway rather than a lakebed. The flight demonstrated that the Space Shuttle could perform a deadstick runway landing at Kennedy Space Center.
What powered the X-24?
A Reaction Motors XLR-11-RM-13 four-chamber liquid-propellant rocket — 8,000 lbf — burning liquid oxygen with an ethyl alcohol fuel. The same engine type that powered the original Bell X-1, the M2-F3, the HL-10, and several other lifting-body and rocket-aircraft programmes.
Where can I see the X-24 today?
Both the X-24B (real airframe) and an X-24A mockup are on permanent display at the National Museum of the United States Air Force at Wright-Patterson AFB, Ohio (museum site).
Sources
See Also
- Northrop M2-F2 / M2-F3 — Sister NASA lifting body (half-cone planform)
- Northrop HL-10 — Sister NASA lifting body (delta planform)
- NASA M2-F1 — Lightweight predecessor; proved lifting-body concept
- Space Shuttle Orbiter — Production glide-back spacecraft
- Martin Marietta X-23 PRIME — Predecessor sub-orbital lifting-body capsule