Northrop HL-10
Northrop · Lifting Body Research · USA · Early Jet (1946–1969)
The Northrop HL-10 was a NASA lifting-body research aircraft built to test a delta-planform alternative to the half-cone M2-F2. The designation reads HL for "horizontal landing" and 10 for the tenth lifting-body shape that NASA Langley had wind-tunnel-tested. One airframe was built by Northrop in 1966; it flew 37 times between December 1966 and July 1970, and reached the highest speed (Mach 1.86, 1,228 mph) and altitude (90,303 ft) of any lifting body ever flown. The aircraft is preserved on a pylon at the entrance to NASA Armstrong Flight Research Center at Edwards AFB.
Aerodynamically the HL-10 was a flat-bottomed, rounded-top delta with three vertical fins — outboard tip fins canted outward and a centreline fin. The shape gave a higher subsonic lift-to-drag ratio (about 4:1) than the M2-F2's half-cone (about 3:1), making approach handling more forgiving. Like the rest of the Edwards lifting-body fleet the HL-10 was carried aloft under the right wing of NASA's NB-52B mother ship, dropped at about 45,000 ft, and either glided to landing or — on the powered flights — fired its Reaction Motors XLR-11-RM-13 four-chamber rocket engine (8,000 lbf, the same powerplant that pushed Yeager through Mach 1 in the X-1).
NASA test pilot Bruce Peterson made the HL-10's first glide flight on 22 December 1966; on this flight the aircraft developed severe lateral oscillation and Peterson barely managed to recover. The airframe was grounded, the outer tip fins were modified with reshaped leading edges and inward camber, and the next flight came 15 months later in March 1968 — the lateral instability had been fully cured. NASA pilots Bill Dana, John Manke, Pete Hoag, and Air Force pilot Jerry Gentry flew the rest of the programme. Manke's 27 February 1970 flight reached Mach 1.86; Hoag's 18 February 1970 flight reached the 90,303 ft altitude record.
The HL-10's quietest contribution may also be its largest. NASA used it in the late 1960s to evaluate a powered-landing technique — adding a small turbojet (later replaced by a hydrogen-peroxide thruster) so the pilot could correct a long approach. The technique was rejected for spacecraft application; the data convinced engineers that a deadstick lakebed-style approach was both achievable and preferable, which is exactly what the Space Shuttle Orbiter went on to do for thirty years. The HL-10 made its final flight on 17 July 1970 and was retired with the rest of the lifting-body fleet as the Shuttle programme moved into hardware development.
For Kids — a shorter, friendlier version
The Northrop HL-10 was a special research plane built for NASA in 1966. It had a very unusual shape — flat on the bottom and rounded on top, like a flying wedge. Three fins stuck up from its body to help it stay stable in the air.
The HL-10 was a "lifting body." That means its body shape created lift, just like a wing does. NASA wanted to learn if a plane shaped like this could fly and land safely. The name HL stands for "horizontal landing," and 10 means it was the tenth lifting-body shape NASA tested in a wind tunnel.
To get into the sky, the HL-10 was carried up under the wing of a big NASA plane called the NB-52B. It was dropped from about 45,000 feet up. Then it either glided down or fired its rocket engine to go even faster and higher.
The HL-10 flew 37 times between 1966 and 1970. It reached a top speed of nearly twice the speed of sound and climbed to over 90,000 feet high. That made it faster than any other lifting body ever flown. It is smaller than a school bus but holds a giant place in aviation history.
Today the HL-10 sits on a display stand at NASA Armstrong Flight Research Center in California. Anyone visiting can see this record-breaking aircraft up close.
Fun Facts
- The HL-10 reached a top speed of 1,228 miles per hour — nearly twice the speed of sound!
- It flew higher than 90,000 feet, which is about 17 miles above the ground.
- The HL-10 is faster than any other lifting body ever built and tested.
- It was carried into the sky under the wing of a giant NASA plane before being dropped and flown on its own.
- The HL-10 flew 37 times over just four years between 1966 and 1970.
- Its flat bottom and rounded top helped it glide better than earlier lifting-body designs.
- The rocket engine used on the HL-10 had four separate chambers that fired to push it through the sky.
- Today the HL-10 sits on a pylon outside NASA Armstrong Flight Research Center so visitors can see it.
Kids’ Questions
What is a lifting body?
A lifting body is an aircraft where the body itself acts like a wing. Its special shape pushes air in a way that lifts the whole craft up. You don't need big wings sticking out to fly!
How did the HL-10 get into the air?
The HL-10 could not take off on its own from the ground. A big plane called the NB-52B carried it up under its wing. Then the HL-10 was dropped and either glided or fired its rocket engine.
Why was the HL-10 important to NASA?
NASA wanted to know if a wedge-shaped craft could fly and land safely. The HL-10 proved it could, and it set speed and altitude records for lifting bodies. What scientists learned helped with future spacecraft designs.
Where can I see the HL-10 today?
The real HL-10 is on display at NASA Armstrong Flight Research Center at Edwards Air Force Base in California. It sits on a tall stand near the entrance so visitors can spot it right away.
Variants
- HL-10 (s/n NASA 804)
- Single airframe built. First flight 22 December 1966 (Bruce Peterson, glide). Reshaped tip fins after first flight cured lateral instability. 37 total flights through 17 July 1970. Preserved at NASA Armstrong, Edwards AFB.
Notable Operators
- NASA
- Sole operator. The HL-10 was owned by NASA and flown by NASA Flight Research Center pilots Bruce Peterson, Bill Dana, John Manke, Pete Hoag, plus USAF pilot Jerry Gentry on detached duty. Air-launched from NASA's NB-52B Stratofortress mother ship over Edwards AFB.
Frequently Asked Questions
How fast did the Northrop HL-10 fly?
Mach 1.86 (1,228 mph) on 27 February 1970, with NASA pilot John A. Manke at the controls. This is the highest speed any lifting-body aircraft has ever reached.
How high did the HL-10 fly?
90,303 ft on 18 February 1970, with USAF Major Pete Hoag at the controls. This is the lifting-body altitude record and remains unbroken.
What does HL-10 stand for?
HL stands for "horizontal landing" — the aircraft's distinguishing feature compared with capsule-style spacecraft of the era. The 10 refers to the tenth lifting-body shape evaluated in NASA Langley's wind tunnels during the early-1960s configuration studies.
How is the HL-10 different from the M2-F2/F3?
The M2-F2/F3 uses a half-cone shape with the flat surface up; the HL-10 uses a flat-bottomed delta with the flat surface down. Subsonic L/D is higher on the HL-10 (4:1 vs. 3:1), which made it easier to fly on approach. Both were built by Northrop and flown by the same group of NASA pilots.
Where is the HL-10 today?
On permanent display on a pylon at the main entrance to NASA Armstrong Flight Research Center at Edwards AFB, California (NASA Armstrong fact sheet).
Sources
See Also
- Northrop M2-F2 / M2-F3 — Sister NASA lifting body (half-cone planform)
- NASA M2-F1 — Lightweight wood-and-tube predecessor
- Martin Marietta X-24A — Air Force lifting-body counterpart
- Space Shuttle Orbiter — Production glide-back spacecraft
- North American X-15 — Contemporary NASA hypersonic research aircraft