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For educational purposes
Chuck Yeager’s flight through the “sound barrier” in the X-1 set the stage for the U.S. experimental X-program, a systematic exploration of new ideas and obstacles in aviation.
Pilots flew at the edge of technical knowledge in untried, untested aircraft.
Featured Aircraft:
- Grumman X-29
Chuck Yeager’s flight through the “sound barrier” in the X-1 set the stage for the U.S. experimental X-program, a systematic exploration of new ideas and obstacles in aviation.
Pilots flew at the edge of technical knowledge in untried, untested aircraft.
Featured Aircraft:
- Grumman X-29
Category
📚
LearningTranscript
00:01Hi, I'm Neil Armstrong. Join me for an adventure through time.
00:57The first supersonic flight set the state of the United States.
00:59The next stage for the successful X-Series. This program established U.S. leadership in aviation technology.
01:08Experimental aircraft created once again a sense of adventure and daring.
01:13Pilots flew at the cutting edge of technology, taking risks to fly untried, untested, and unknown aircraft.
01:30World War II fighter pilots unknowingly learned of a dangerous phenomenon associated with transonic flight when they dove their airplanes
01:39from high altitude.
01:40Many aircraft were lost through structural failure.
01:53Aircraft like the Spitfire and the sleek P-38 Lightning were capable of dive speeds near Mach 1.
02:00In the early 1940s, many thought an invisible barrier would shatter any craft that reached the speed of sound.
02:07It was called the sound barrier.
02:11What pilots and their aircraft were experiencing was compressibility.
02:15In a dive, the aircraft could be traveling as fast as seven-tenths the speed of sound.
02:21The air's speed over the wing could exceed the speed of sound.
02:25As the aircraft flew increasingly faster, the air in front of it compressed and caused violent buffeting.
02:34Wind tunnel technology was not far enough advanced for supersonic testing, so novel research methods were tried.
02:42For example, small test models were attached to the wing of a P-51 Mustang, where air speeds reached Mach
02:501.2 during dives.
02:52The research data was useful, but limited.
02:55Rockets and jet engines presented possibilities for safer testing at much higher altitudes.
03:01And so during World War II, the American X program was born.
03:07Great Britain was extremely active in transonic research.
03:11The de Havilland Swallow, a small jet, was designed to set a new world air speed record and break the
03:16sound barrier in the summer of 1946.
03:19At about Mach 0.875, it pitched violently out of control and was lost.
03:25Its fine British test pilot, Geoffrey de Havilland, the designer's son, was killed.
03:30Accidents like de Havilland's did not discourage American attempts at beating this transonic dilemma.
03:37Bell Aircraft Corporation began non-powered flight testing of its XS-1 for the National Advisory Committee for Aeronautics, later
03:46known as NASA.
03:48The basic design of this new aircraft was different.
03:52It was intentionally shaped like a .50 caliber bullet.
03:56Because it was known, the shape was very stable at supersonic speeds.
04:02There were three X-1s, each slightly different in design.
04:07Hung in the bomb bay of a B-29 Stratofortress, X-1s were dropped from an altitude of roughly 35
04:13,000 feet.
04:20They were powered by four rockets, each ignited separately by its pilot after launch.
04:30After more than half a dozen earlier flights, getting closer and closer to Mach 1,
04:35on October 14, 1947, test pilot Chuck Yeager became the first man to fly supersonic in the X-1.
04:46The B-29 climbed to altitude, then Yeager descended from the mothership and squirmed into the tiny cockpit of the
04:54X-1.
05:00At 20,000 feet, the X-1 was dropped, and the four rocket chambers were ignited in sequence.
05:08He reached Mach 1.06 at an altitude of 43,000 feet for about 20 seconds.
05:17The feared sound barrier was broken.
05:22His X-1, Glamorous Glenis, named after his wife, landed safely on the Muroc dry lake bed in California.
05:31Yeager reported the X-1 flew so well, there were few indications other than by the Mach meter that he'd
05:37flown supersonic.
05:38It was a crucial flight. The X-1's successes would breed a whole family of X aircraft.
05:53There were the second generation X-1s, A through E, that would study speeds above Mach 2 and altitudes beyond
06:0190,000 feet.
06:07By 1956, testing was well underway on the X-2, an aircraft designed to explore another unknown, the effect of
06:16swept wings on supersonic flight.
06:18Like the X-1, it had developed out of research into the problem of compressibility.
06:25Test pilot Pete Everest took the X-2 close to Mach 3.
06:29It was an aerodynamically dicey area for the design.
06:41Reaching Mach 3.2 just two months later, pilot Mel Apt was killed failing to parachute from his escape capsule
06:49in time.
06:50Insufficient planning, not the aircraft, was blamed for the accident.
06:56The aircraft had experienced a predicted but largely unknown phenomenon called roll divergence, and then tumbled out of control.
07:04The use of steel alloys and high-speed, high-altitude design came out of X-2 research.
07:20The X-3 was intended as a total departure from earlier X aircraft, but was instrumental in understanding the roll
07:28phenomenon that resulted in the X-2 crash.
07:31The Douglas Stiletto X-3 looked rackish enough to do the job.
07:36It was designed to take off and land under its own power, rather than be air-launched, and fly at
07:42Mach 2 for extended periods.
07:52Lacking its intended engines, it failed in that mission.
07:56Nevertheless, it demonstrated the tendency of supersonic designs to yaw and pitch while in a roll.
08:03Uncontrolled, the result can be disastrous, as it was in the X-2.
08:08Many more X aircraft were to come, but the X-1 flight of Chuck Yeager in 1947 was a major
08:15turning point in aviation history.
08:27The American X program of the 50s and 60s was a special time in the history of research aircraft.
08:34Former test pilot Milt Thompson is the top engineer at NASA's Dryden Flight Research Center in California.
08:41Ted Ayers is its deputy director.
08:42Neil Armstrong talked with Thompson and Ayers about that prolific age of experimentation they were part of.
08:50Well, the X airplanes were really unique.
08:52They were designed to investigate a specific kind of problems.
08:57For example, the X-1 was to look into breaking the sonic barrier.
09:02How about some of the others that come to mind? What were their purposes?
09:06Well, as you probably know better than I do, there were a series of aircraft that followed the X-1
09:13that were more conceptual kinds of aircraft.
09:19They had unique configurations like the X-3, the X-4, the X-5.
09:24And there they were really looking at that configuration to see if it was something that could be used in
09:31an operational aircraft to see how well that concept...
09:36For example, the X-5 was a first test, I guess, of a variable sweep airplane.
09:41And at that point in time there had never been one.
09:44Certainly the X-5 was a forerunner for variable sweep, but there were so many things about the implementation of
09:50variable sweep that had to be looked at.
09:52And the X-5 was not efficient from the standpoint that when you move a wing aft, then the aerodynamic
10:00center moves and it causes a lot of problems from stability and control and trim.
10:05And so there were follow-on research activities that came out of the X-5 that said you could, in
10:11fact, design a variable sweep wing that didn't have this big shift and cause all these big trim changes.
10:16And a lot of that was done in the wind tunnel.
10:18So you had the X-5 kind of setting the stage and then a lot of analytical and wind tunnel
10:22work that refined the use of the variable sweep and ultimately ended up on the F-14, the F-111,
10:29and some of the other variable sweep airplanes flying today.
10:33We've seen a lot of cases where the flight data disagrees with what was predicted.
10:40And theoretically then the wind tunnel people have to go back and modify their procedures or their equipment to try
10:48and predict more accurately what's going to happen in flight.
10:52In flight tests, you fly to see if something works. In flight research, you also look at why it works.
11:06Some of the most interesting experimental aircraft looked at vertical takeoff and landing, or VTOL, and VSTAL, vertical short takeoff
11:15and landing.
11:18The Ryan X-13 VertiJet was built to be the first jet VTOL, examining not only design but propulsion systems
11:26as well.
11:27It proved jet VTOL flight was possible.
11:30In 1957, test pilot Pete Girard lifted away from the special launch platform, moved to level flight, and circled the
11:39field only to find the launch trailer was not ready for landing.
11:43Fortunately, there was a backup platform, and the transition was made back to vertical flight with a resultant safe landing.
11:53The Bell aircraft X-14 series took VTOL flight another step.
11:58Its design involved vectored thrust that caused phenomenal difficulties with air recirculation near the ground.
12:05That made stability control a problem, but overall it proved safer than the tail-sitters that preceded it.
12:12The Hiller X-18 looked at the possibilities of tilting the wings from vertical to forward flight of a VSTAL
12:20or VTOL aircraft and the problems associated with it.
12:23It was a short-lived project with very few flights, but it did provide valuable data.
12:32In the mid-60s, the Bell Aerospace Textron X-22A proved without question the viability of VTOL aircraft.
12:40The first flight of the X-22A was March 17, 1966.
12:46Two were built.
12:47They were powered by four General Electric shaft turbine engines mounted in pairs at the root of each aft wing.
12:53The X-22 proved the worthiness of a ducted fan propulsion system.
12:59Flight tests continued with successful takeoffs and landings and forward speeds reached 100 miles per hour.
13:05Then August 8 of that year, the unexpected happened.
13:14The cause of the crash was later determined to be the total failure of the dual hydraulic system.
13:19The crew escaped unhurt, but the aircraft was not repairable.
13:26The second X-22A continued testing.
13:29It reached test speeds of 225 miles per hour.
13:33It was the first VSTAL aircraft to test the LORAS system, which gave pilots precise airspeed references near zero velocities.
13:41The device was a major breakthrough for use on helicopters and other VSTAL aircraft, especially when operating in close quarters,
13:49on carriers, in other tight spaces.
13:51The X-22A provided an excellent test bed for a variety of VTAL systems.
14:03Not all experimental aircraft of the period were in the government's X program.
14:07Aircraft makers did their own testing.
14:10For example, in the 1970s, Bell Aircraft Company began designing the XV-15 tilt rotor.
14:16It was used to demonstrate that the VTAL concept would work for the Military Assault Transport V-22 Osprey.
14:28The Bell Boeing Osprey is a multi-role transport and rescue craft with two Allison T-406 turboshaft engines.
14:37These drive propellers for horizontal flight, which tilt upward, acting as rotors in hover.
14:43The Osprey, like the British Harrier jump jet, is the practical result of experiments in vertical flight.
14:54The early X-Series of aircraft in the 50s and 60s investigated areas of aircraft research never before explored.
15:01In the decades to come, the program would reach into outer space.
15:10The experimental program is a systematic exploration of fresh ideas in aviation.
15:16The X-1, supersonic flight.
15:19X-4, flying wing.
15:21X-5, variable sweep wing.
15:24X-14, vertical takeoff.
15:26X-15, hypersonics.
15:30The Grumman X-29, with its forward swept wings, represents things to come.
15:37The X program proves that the future of aviation is limited only by our ability to dream and dare to
15:44take new challenges.
15:51Various research aircraft in the American X program are referred to as test beds.
15:56A test bed is a conventional or specially created aircraft used to demonstrate technology advances.
16:02One of the most unique is an aircraft that looks like a fighter.
16:06It's the Grumman X-29A.
16:09Its design displays a wide array of technologies.
16:12Its fuselage and wings are made from advanced graphite composites that are lightweight and stronger than stainless steel or titanium.
16:20It has super critical wings with variable curvature and a new control on the trailing edges of its wings called
16:26flapper arms to make that happen.
16:28Its close coupled canards or front wings are entirely moveable and control air over the main wings giving the X
16:36-29 extreme agility whether flying slow or fast.
16:40The X-29 is a major leap in aeronautical engineering and the development of more nimble and fuel efficient fighter
16:47aircraft.
16:56It uses fly-by-wire computer adjusted electronic control of the movable flying surfaces with input from the pilot or
17:04autopilot.
17:05The X-29A's computers make 40 adjustments per second to keep it from tumbling out of control.
17:15Test pilot Steve Ishmael flies the X-29A for NASA research and comments on its handling and performance.
17:24This airplane is a collection of aerodynamic and flight control experiments that have all been grouped together into the X
17:33-29.
17:33The major thrust of the experiment is the forward swept wing which was to give the airplane hopefully as good
17:41a performance as a comparably aft swept wing.
17:44The forward swept wing is supposed to have less drag from about .85 Mach to 1.1, 1.2 Mach.
17:53So it would allow a fighter to maneuver in that region which is very, very characteristic of those types of
18:01airplanes with less fuel required or smaller volume of the airplane.
18:05This is a very small airplane relative to fighters even though it's not designed to have a mission.
18:09But the forward swept wing tends to make the airplane more efficient in that region.
18:18The canard is a separate experiment from the forward swept wing.
18:22In this airplane it complements the forward swept wing very much so.
18:27Basically it is the primary way that we pitch the airplane and balance the airplane.
18:33Because it is a canard, which means it's a forward surface, it makes the airplane very unstable in terms of
18:40pitch.
18:41And that is what also introduced one of the major flight control experiments because of the instability of the pitch
18:47axis of the airplane.
18:50It has to have very strong control power.
18:53That's what keeps the airplane flying in the direction you want it to.
18:57Well, because you have that very strong control power, then if you did not have the computers making checks on
19:03what G you're pulling,
19:05you could pull many more G's than the airplane is structurally capable of.
19:08With the computers you feel like you really have a lot of help flying the airplane and most importantly I
19:16guess the airplane is very easy to fly.
19:25What lies ahead is the most ambitious X program ever conceived.
19:30It's the X-30, a national space plane capable of trans-atmospheric travel,
19:36a vehicle able to take off and land at airports under its own power and operate in Earth orbit at
19:41hypersonic speeds.
19:43It does not yet exist, but is already what fascinates people like Milt Thompson, Ted Ayers and Neil Armstrong.
19:51The goal of course is to get the price of a ticket for a supersonic transport across the ocean comparable
19:56with today's 747 prices.
19:59But it will be a player I think in opening up the Far East and people who want to travel
20:05fast.
20:05The aerodynamics and the propulsion systems have improved so much over the Concorde generation that we're looking at airplanes now
20:13that are very efficient.
20:15There are problems. The big problem is the environment. What is this doing in terms of ozone depletion?
20:21Are we in fact injecting chemicals from the exhaust into the ozone? And that's a high priority.
20:28Like new aircraft concepts before it, the X-30 will require technological breakthroughs in airframe, materials and systems.
20:35The design of the aircraft will be closely linked to what powers it. And that may be more than one
20:41system.
20:41Ramjets may assist it on takeoff and landing. And then air-breathing scramjets using hydrogen fuel will have to do
20:48what ramjets cannot,
20:49process supersonic air and mix it with oxygen for thrust to multiple Mach speeds.
20:55Next, rocket motors will propel it to 17,500 miles per hour and earth orbit, 30 times faster than a
21:03jetliner.
21:04The wide fuselage will act as a wing and have to incorporate the engine inlets and exhaust.
21:10The skin of the aircraft will have to allow for repeated use and high temperatures, calculated to be 5,000
21:17degrees Fahrenheit on re-entry.
21:22Much of the technology and ability to build such an aircraft is already at hand.
21:28But no wind tunnel or airplane exists that can duplicate the speeds the X-30 will reach.
21:34The development of the X-30 means that another adventure has begun.
21:44Join me next time for First Flights.
21:47.
21:48...
22:01.
22:11.
22:13You
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