By Tom Demerly for ALERT 5.
It flew at nearly Mach 7, seven times the speed of sound and twice the speed of a rifle bullet. The speed record it set 47 years ago today still stands today.
It flew so high its pilots earned Air Force astronaut wings: 280,500 feet or 53.1 miles above the earth.
It pioneered technologies that were used on the SR-71 Blackbird, the space shuttle and the reusable spacecraft in Richard Branson’s future Virgin Galactic passenger space program.
And it killed test pilots in an era before redundant flight control systems and modern safety protocols for hypersonic flight.
It was the North American X-15. Today is the 47th anniversary of its fastest ever manned, powered flight.
The X-15 could be the most ambitious and successful flight test program in aviation history. Apollo astronauts flew it. It challenged the paradigms of aerospace design well beyond the limits of any prior program, including Chuck Yeager’s sound barrier busting Bell X-1. The X-15 program sits alongside the Wright Flyer as an aviation milestone. So much progress was made so quickly in the face of such great risk with such rudimentary technology that no other development program, with the exception of the Apollo missions, has come close.
10:30 Hr.s Local, Tuesday, 3 October, 1967. Edwards Air Force Base, Mojave Desert, California.
After the awkward and tedious process of donning his pressure suit, Air Force test pilot William J. “Pete” Knight, clambers up a custom made ladder and lowers himself into the cramped cockpit of X-15A-2 aircraft number 56-6671. Half a dozen men helped Knight get ready for his flight this morning, testing life support equipment and helping him into his bulky pressure suit. His first astronaut type flight helmet attached to his pressure suit didn’t work with his aircraft communications system, so technicians have replaced it with a backup pressure suit helmet. Communication checks are normal now.
The X-15A-2 rocket plane is mounted between the number 5 engine and the fuselage under the right wing of “Balls 8”, a massive Boeing NB-52B mothership. Today it’s flown by Air Force Col. Joe Cotton and Lt. Colonel Bill Reschke Jr. The launch aircraft has a sprawling 185-foot wingspan and eight jet engines. It was originally a B-52 strategic bomber built for dropping hydrogen bombs on the Soviet Union if the Cold War ever got hot. The bizarre pairing of aircraft, the little X-15 nestled under the right wing of the giant silver and red B-52, is parked at the beginning of runway 04R/22L, a 3 mile long × 300 foot wide strip of reinforced concrete with an additional unpaved 2 miles for emergencies. Other than the sounds of vehicles coming and going it is quiet and still at Edwards Air Force Base in the wide expanse of the Mojave Desert.
This X-15 is different than the only other two aircraft of the same type. The other two X-15’s are painted black and have a yellow NASA band on their vertical stabilizer with U.S. Air Force markings on the fuselage and wings.
The X-15 Pete Knight is strapping himself into is an “X-15A-2”. It has no exterior markings. It is covered with a milky white ablative coating to resist heat and carries a pair of giant anhydrous ammonia tanks under its fuselage. The rocket plane is made of a special, ultra strong alloy called “Inconel-X”. As Inconel-X heats up it actually becomes stronger. The X-15A-2 burns a volatile mixture of deadly ammonia and liquid oxygen as fuel. When ignited, its single XLR99 engine burns 7 tons of fuel in just over a minute and generates half a million horsepower, nearly 60,000 pounds of thrust. By comparison a modern day F-16 fighter generates about 30,000 pounds of thrust in full afterburner.
Today’s flight profile has one objective: speed. It is an attempt to set a maximum manned-flight speed record. The X-15 will be a piloted projectile blasting through a violent acceleration from 500 MPH to nearly 5,000 MPH in only 75 seconds. Six times the speed of sound. On the downside of this flight profile the X-15A-2 will decelerate so violently that a rearward-facing crash pad is installed in the canopy, in front of the pilot, so Pete Knight’s helmet can slam into something soft as the friction of the atmosphere slows the plane after its explosive fuel burns out.
Test pilot Pete Knight is hot inside the X-15A-2 cockpit. The desert sun in the Mojave is unrelenting. The cockpit is pressurized with nitrogen gas and Knight is breathing oxygen fed to him through his spacesuit. In an emergency Knight needs to get the X-15A-2 below mach 4 and 120,000 feet to use his rudimentary ejector seat to escape. His chances of surviving an ejection in that corner of the performance envelope are slim. Outside that envelope, where the X-15A-2 will fly today, they are zero.
A little over a month later, on November 15, 1967, USAF test pilot, Major Michael J. Adams will die when his X-15 enters a violent spin at mach 5 and disintegrates under crushing G-loads. Wreckage is strewn over 60 miles and two states. He is remembered as the first fatality of the U.S. space program.
Knight communicates with ground control and the crew of his NB-52B mothership over his radio as he prepares for his record setting mission. Checklists are read and verified, engines on the NB-52B are started and the aircraft taxis heavily onto the long runway with a following group of crash, fire and support trucks trailing behind. Two chase planes, a “Century Series” F-104 Starfighter and an F-100 Super Saber, prepare to take off to follow and observe the mission until separation. A second set of chase aircraft will be in the air to receive the X-15A-2 as it decelerates back toward Edwards for landing at the end of the flight. Two sets of chase aircraft are needed, one pair at the start of the flight and one at the end. Nothing in the air can follow the X-15A-2 through its flight, not even a missile. Nothing is fast enough.
The sky is brilliantly clear, arcing dark blue up into a vaulting space that seems to dare the test pilot strapped into the milk white missile-plane. It is a deadly empty space where physics are a cruel arbiter. The “surly bonds of earth” are comfortable and safe by comparison. The vast test range where the mission is being flown covers three states, Utah, Nevada and California. Knight will hurtle across these states in a blur only seconds long covering well over a mile per second.
The take-off roll is long and oddly slow looking. The NB-52B wallows into the air with an unusual flight attitude, black smoke settling rearward from its screaming engines. Knight is a passenger inside the X-15A-2 for the moment, calmly reviewing procedures and checklists and re-checking his flight profile and navigational range card strapped to the right leg of his spacesuit. It is about 13:40 local time.
The climb to launch altitude takes time. Chase aircraft close in on the NB-52B/X-15A-2 pairing in preparation to conduct visual checks of flight control actuations prior to launch. A local NOTAM, or Notice to Airmen restricts all civilian air traffic from the area.
The white X-15A-2 is not as attractive as its black predecessors. It looks almost like a mock-up, not a real aircraft, since the paint appears blotchy and hastily applied. The giant ammonia tanks look like an afterthought strapped to the pasty missile-plane. Despite all the planning, training and preparation the X-15A-2 looks more like something preparing for a crash test than the threshold of a new aviation speed record.
Even with meticulous preparation, planning and checks the X-15 missions were often filled with unexpected incidents. On an earlier flight, test pilot Scott Crossfield’s X-15 cockpit filled with smoke while it was still mated to the NB-52A. Almost immediately after radioing the crew inside the NB-52A mother ship about the smoke in his cockpit, Crossfield’s radio in the X-15 went dead. The implication of a burning X-15 filled with highly explosive ammonia and liquid oxygen attached to the wing of a B-52 caused the crew to consider dropping the X-15, not knowing if Crossfield was still alive or already incinerated in a deadly cockpit fire that would touch off a massive explosion any second. Crossfield told the NB-52A crew earlier, if there was any question, “Drop me”, since “There is one of me, and four of you.” Oddly, the smoke in Crossfield’s cockpit cleared and the radio began functioning again. The mission proceeded as normal.
The central risk of the X-15 concept, especially when it was chasing altitude records, was that it crossed from atmospheric flight to non-atmospheric near space flight. Those two regimes are vastly different. One has air, the other doesn’t. In the atmosphere aircraft steer by using control surfaces over which air moves. Move part of the flight control surface as air is moving over it, and the plane moves. In near-space the rules change entirely. There is, effectively, no atmosphere or air moving over flight control surfaces. The aircraft uses miniature rockets mounted in the nose and tail to control its yaw, pitch and roll. In 1967, it was an imprecise science. In the atmosphere the stubby wings and small control surfaces of the X-15 had little purchase. In near space they had none.
Once at drop altitude of 45,000 feet final checklists and systems checks were completed. There was a countdown. The X-15 was released at precisely 14:31:50.9 local time. It dropped at a slight angle from under the wing of the NB-52A, quickly rolled level, dropped further then ignited its engine.
A brilliant white contrail lanced forward of the lumbering NB-52A and the supersonic chase planes struggled to try to keep pace with the X-15. They were quickly left behind. The white trail traced a curve upward, upward, vaulting away into the western sky. Blue sky gave way to black. And there was a concussive explosion.
The sound barrier is broken when a succession of shockwaves accumulate on the nose of a projectile. Or aircraft. When they are compressed enough, the explosion happens. Like the crack of a bullet. There are often two sonic booms. In this case, there is no record. But over the next 75 seconds Pete Knight accelerates past the sound barrier- and keeps on accelerating. Mach 2…3…4… There is no secondary sonic boom as Mach speed accumulates. No dramatic acknowledgement of a new speed frontier being crossed.
Mach 5.
Five tons of anhydrous ammonia and liquid oxygen have burned in a barely controlled explosion 15 feet behind Knight’s ejector seat. Two tons remain.
Mach 5.5.
A by-product of speed in the atmosphere is friction, and a by-product of friction is heat. Pete Knight’s X-15A-2 begins to melt. The leading edge of the wings glow at over a thousand degrees. Even at high altitude the air molecules can’t get out of the way fast enough to dissipate heat. So chunks of Knight’s X-15 begin to burn and fall off. Big chunks. During flight, shock waves burn through the leading edge of the lower ventral fin igniting a series of small fires in the engine housing. Near the explosive nitrogen tanks.
Mach 6.
Knight already has the throttle advanced to the forward stop. One of two things will happen; he will complete his fuel burn and set a new speed record by a massive margin…
He passes through Mach 6.5.
Or, he will disintegrate as the accumulation of heat causes a massive structural failure of his airframe that will result in an instantaneous explosion of any unburned fuel. It’s unlikely much wreckage will be found.
Mach 6.6.
A big part of the X-15A-2’s ventral fin ignites and burns completely through. It flies off the aircraft, tracing a bright, burning arc to the desert floor.
Mach 6.7.
Fuel burn complete. Flight profile nominal. Powered flight terminated, ballistic flight initiated. Knight is still alive and at the controls of the world’s fastest glider. The X-15A-2 had reached its maximum velocity, a new manned flight speed record by a huge margin. It arcs over the Nevada-California border, over a mile a second, leading edges still glowing from heat. Accumulated heat detonates the separation charges on the dummy scramjet carried for test purposes. It explodes away from the X-15A-2 over Edwards bombing range as Knight decelerates through Mach 1 and 32,000 feet, more charred junk toppling to earth. Knight continues to descend, burning fragments dropping off the aircraft as he flies. The relentless forces of physics reel in ambition once again. But only after history is made.
Somewhere east of Edwards Air Force Base the second set of recovery chase aircraft find Knight as he descends and decelerates to enter the landing profile. The X-15A-2 is charred. There are visible holes burned through the ventral tail. Would the landing gear still function? Had the single nose wheel tire melted from the heat? The rear landing gear on the X-15 was a pair of stubby, ski-like skids designed for one-time use.
Knight extends his nose wheel, landing skids, speed brakes and sets flaps for landing. A chase pilot confirms that the landing gear appear intact. He touches down at 14:40:07 local time on Rogers Dry Lakebed runway 17/35. A billowing plume of dust erupts behind his two rear skids as the X-15A-2 slides to a stop on the 7.5-mile long runway. The flight lasted 8 minutes and 16 seconds and covered over 213 miles of the western United States. Knight’s rocket engine only burned for a fraction more than 2 minutes and 20 seconds of the flight.
William J. “Pete” Knight’s speed record remained unbroken by any winged craft until the space shuttle Columbia’s reentry from space on April 14, 1981. His speed record still remains intact for a non-orbital aircraft.
Pete Knight had become the fastest pilot to fly inside the atmosphere in powered, controlled flight. A record that officially remains today.
The massive achievement of the X-15 program, both speed and altitude records, would pave the way to the moon and the space shuttle program. Its technology dividend is truly immeasurable, touching everything from the GPS constellation to cell phone communications and even the idea of civilian space travel.
Knight was awarded the Harmon International Aviator’s Trophy in 1969 for his record setting flight by then-President Lyndon Johnson. Following his test flight program in 1968 Bill Knight transferred to an active combat unit and flew 253 combat missions over Vietnam in the supersonic F-100 Super Sabre. For Knight, flying the Super Sabre after the X-15 must have felt like going from a dragster to a dump truck.
Pete Knight left the Air Force and began a political career in 1984. He eventually became the first ever elected Mayor of Palmdale, California. Under Knight’s term Palmdale was the fastest growing city in the United States. He was later elected as a Republican Senator for the 17th District of California.
In an odd footnote Knight wrote legislation in California called “Proposition 22” that banned same-sex marriage. But one of Knight’s sons, David, was gay. David Knight defied his father and married his same-sex partner during a loophole period of the law in San Francisco. Proposition 22 was later repealed in California after being judged unconstitutional.
Air Force Test Pilot, speed record holder and decorated combat fighter pilot William J. Knight died in 2004 at the age of 74. His manned, atmospheric speed record still stands. That we know of.
The actual X-15A-2 flown by Knight was restored after the flight and returned to the original black paint scheme but never flown again. It is now an artifact in the Air Force Museum at Wright-Patterson AFB in Dayton, Ohio.
The Tactical Air Network 
FYI – your figures “280,500 feet or 29.5 miles above the earth” don’t add up. At 280,500 feet altitude, Knight would have been a little over 53 statute miles up, which would have been high enough to qualify for the USAF Astronaut Badge back then (50 statute miles req’d), but not enough today (100KM required).
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Thank you Kupe. Your calculations are absolutely correct and we edited the text to reflect your observation. Appreciated Sir.
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Which beggs the question why the americans still use antiquated british measuring units.
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You mean as opposed to using a French system based on an erroneous calculation of the diameter of the Earth?
Dunno. Possibly because the bare assertion that a measuring system uses decimal divisions makes it “scientific” is about a scientific as a Neil deGrasse Tyson lecture. It certainly seems scientific if you say it quickly and don’t think about it.
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I will give you a reason why it should be used vs why the US uses it. Most of it is reproducable without fancy instrumentation. A ‘pint is a pound, the world a’round’ and their ilk susprsingly are the basis for much of the measures in the old English system. It fit a world of physical objects.
Were we to have a societal breakdown, some measurement system other than the metric system would probably arise, again based on simple observational measures lackng any instrumentation.
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There is an old adage that the boundary between the traditional British measure and the metric system also marked the boundary between freedom and tyranny. But most of the Anglo-sphere has succumbed to MKS, as they have succumb edge to so many of the petty tyrannies emerging from the Continent.
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If the Lord had wanted us to use the metric system, He would’ve had 10 apostles instead of 12! ; )
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Because we can…but also because we fly vertical in knots… Air mass glide ratio made easy. We used knots (indicated and true) in the Eurocopter X3 when I got the chance to fly it.
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I had to dive in 6 feet of water before I fathomed it out!
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Right U R
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In typical Air Force fashion, the plane had to be restored in a manner that would have Air Force painted on it. Sad.
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What you want on it. Us Navy ? Get real
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I would have left it ‘as-is’ after that flight, to the extent that safety & preservation would allow. (But perhaps it was expected to fly again some day.)
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When it rolled to a stop, it was a piece of junk.
Leaving it in that condition for display would have induced a lot of food for thought in every observer along the lines of:
OMG, what kind of men flew that?
It would have been a unique display piece.
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It should have been left just like it was when it landed so all could see just how close he came to death. Now it just looks like any other X15A
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The ablative material had to be removed anyway to inspect the airframe and fully examine the damage, which was extensive and far more than just the tail fin. There was serious heat damage to several parts of the airframe/systems including those in the the chine and tunnel areas ahead of the wing that didn’t show from the outside. This is what eventually grounded the airplane.
They U.S.Navy’s role in the X-15 program was comparatively minor, they were part of the original test program and only had one pilot who flew it a few times.
The memory’s fading (prior to this piece I haven’t done any reading on the X-15 program in years), but I think it was a Cmdr. Peterson who was the only USN X-15 pilot and he had left the program before the mid-point of the X-15s career.
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Look at the photo of Pete kneeling in front of the X-15, it has U.S.AIR FORCE painted on then.
The X-15 program was a USAF/NASA/U.S.Navy program from inception.
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How does the part about his gay son lend any credit to the story. Why is it mentioned?
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Shawn, it’s interesting you ask this question since I asked it myself when I was writing this. I nearly left it out since it wasn’t related to the X-15 flight, and this story is about the X-15. However, it is also about pilot Pete Knight, a man who lead a remarkable and notable life. In the interest of balanced reporting I ultimately decided to include it, since it was a noteworthy aspect of Knight’s life following his work on the X-15 and his political career. It is, as I mentioned in the article, a footnote.
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Tom, it’s not a “noteworthy aspect of Knight’s life following his work on the X-15 and his political career” as you state in the article. It’s a painful matter between a personal bias and his son and truly discredits the rest of the article. What was “nearly left out”, should have been left out. The obvious posturing of “it is also about pilot Pete Knight” is blatantly false. If it were true, what about his wife, or wives, his life in politics or his other achievements that went unattended in this article. It appears your agenda became too important, more important than the article you intended to write about. It was not “in the interest of balanced reporting”. You went off topic, simply put.
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You should have left that out. Period.
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If I remember correctly, I cast a vote for Rep. Knight on my very first ballot as an 18 year-old. His district included Agua Dulce, CA, where I grew up. I did know (but had forgotten) that he authored Prop 22. I didn’t know about his son. Thought it was interesting as a footnote, FWIW.
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To the author: How can Maj. Adams be considered the first casualty of the space program in November 1967, when the crew of Apollo 1 was lost in January 1967?
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Buddy, excellent question. I can’t provide an “official” answer, but I will provide an idea of why this may have shown up in my research. The Apollo 1 astronauts, Ed White, Roger Chaffee and Gus Grissom, died in a tragic and terrible accident on the ground. While this does not diminish in any way the gravity of their loss and the significance of their sacrifice, some references list X-15 pilot Major Michael J. Adams as the first astronaut “killed in flight”.
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A bit over-written and open to question with the obvious errors, such as the wrong number of nose wheel tires… A fun read, but questionable.
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Oh! You are SOOOOOO SMART! Thank you for visiting us troglodytes before you return to your tower made of smart people tomes!
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This was an excellent article. I appreciate it exactly as written. The additional facts concerning his life after this historic flight are quite salient for me and help to complete the picture of the man behind the flight.
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Great read, your writing style really painted the picture of what it was like to be there on the day.
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Great story and compelling read. An adventure that all Americans ought to read.
Thanks!
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I didn’t know that nitrogen was explosive! (mach 5.5)
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At that temperature, anything can be explosive ifvthe pressure vessel is compromised.
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Reblogged this on Heritage Valley Views and commented:
When men were men and it didn’t matter how much fuel you used to get the job done.
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The F-4 had proven that with enough power, a barn door can fly.
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A very attractive and heavily armed barn door. Watch it!
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This article is by far the most interesting thing I have read on Facebook.
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Men were Men and the USA was way beyond the rest. Those Days…. GREAT
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I knew of the controversies regarding Prop 22 here in California. I did not know anything about Knight’s stellar service to the country until this article. Thanks.
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Thabk you for a compelling and well-written article. I learnt so much that I didn’t know before.
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Living in Dayton, Ohio, I have had the pleasure of visiting the National Museum of the United States Air Force on numerous occasions. I have touched that aircraft. Now I have a better idea of it’s history.
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Really nice story. I like the present era and communication technology in that good stories slowly come to surface, not longer hidden by “secret” stamping.
Two things I miss: at what stage the external tanks were dropped and were they ever found back?
Plus I noted the large cut-out in the B52’s flaps to accommodate the fin. I wonder what were the effects on landing and how they coped with that.
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I’m not sure the explanation of a sonic boom is accurate–when an aircraft goes supersonic, the bow wave of compressed air that normally accumulates in front of the fuselage and wings becomes attached to the aircraft. As speed increases, the shock wave travels aft on the wings but remains attached, which is why supersonic flight requires aircraft engineering design that allows the flight controls to function in a substantially altered aerodynamic environment. If you looked at the jet/rocket plane from the side, that shockwave extends aft, upward and downward for significant distances–all the way to the earth’s surface, in fact–and the “boom” one hears on the ground is the passing of the wave across the point the observer is standing. My point is, it’s not an “explosion” per se, it’s the passing of a “wall’ of differential pressure that manifests itself as noise–the “boom,” like seeing an explosion in the distance and then feeling/hearing the overpressure/”bang” seconds later.
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Absolutely right. The author does not understand what a sonic boom is. He seems to think it is a one-time event that happens at the moment Mach 1 is crossed. Not true at all. Once the Mach is exceeded it is a continuous event that only seems momentary to observers on the ground because it is passing. Spend a few minutes in the pits at a rifle range with bullets cracking overhead and you’ll understand.
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Truly when men were men……The US will never be like this again, mainly because White American men are no longer in control of the country. “Diversity” rules the day today and forever more, with open borders and more and more so called “immigrants” flooding our shores. The US is being dumbed down and in fact, has already happened. Thug culture is the new American ethos. Also the political establishment in DC doesn’t want to be a sovereign nation anymore, they worship globalism and equal outcomes (socialism). USA – kaput.
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No thanks to Обама and the Demo☭rats!
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Very informative article. I would like to know how the speed was “clocked” Successive times over two points of known separation? Mach No is all relative, being dependent on temperature. Indicated speed is a function of air density. These would have fluctuated wildly! Maybe it was tracked on radar? Thanks for the article.
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Nice article. I enjoyed it. We still have what it takes. It’s buried under all the horded junk of a multicultural, metrosexual, feel good all the time society, that elected President Obama to two terms.
Doug Santo
Pasadena, CA
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“It pioneered technologies that were used on the SR-71 Blackbird…”
Since the SR-71 was introduced several years before this, were these pioneering technologies later added to the then-mature SR-71?
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I was stationed at Edwards between 1963 thru 1965. Your article was very good, but i thought you could have mention some of the other pilots who flew the X-15. Joe Engle was the youngest to fly this remarkable aircraft, Milt Thomptson, Scott Crossfield to name a few…..
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The “Pint a pound” comment made me smile. Long time since that was the case… still, RE: metric vs. English units, I guess there are two types of countries in the world: Those who use the metric system, and the one who put a man on the moon.
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There are 8 pints in a gallon and a gallon of water weighs approximately 8 pounds. Ergo, a pint of water weighs approximately one pound.
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RE: metric vs. english units, the english system still works and as long as you can measure repeatably and accurately compared to a known standard, what difference does it make?
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Today, with computers, calculators and the like, probably none Jim. But hey I lived a good chunk of my life without them. So what is half of 0.833333333? Most kids today could not do that without a calculator. That’s 5/6ths. Simple solution is 5/12ths. We are taught that decimal measurements are more accurate, nope. Same logic is applied to the metric system. Accuracy has nothing to do with the units of measurement and everything with the observational acuity of the recorder.
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I was stationed at Edwards from 1959 to 1968, working for Northrop Aircraft and then the USAF. It was Pete Knight that gave me my first supersonic airplane ride, as an engineering observer in a T-38. I remember that flight vividly; he pulled so many g’s that my nose was continually running into my mask! The date was 17 Jan 1962, according to the plaque in my office. Pete was a real gentleman, and fun to be around. After his X-15 record, he was known as “Speedy Pete” around Base Operations, but his demeanor treated that flight like just “another day at the office.”.
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This is an incredible insight. Thank you very much for sharing it Sir. Appreciated. Tom D.
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I think it’s kind of amazing that when one of the X-15s made a hard emergency landing and broke in half they just welded it back together and flew it again, but Pete Knight’s X-15 was so badly damaged from the heat and shock waves it was retired. Those babies were all steel, very tough. Not tough enough for Mach 7.
BTW, neither Prop 22 nor Prop 8 “banned” anything. They just closed loopholes and reaffirmed what was alredy clearly defined in the Cal constitution. (Thanks for trying Pete.)
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I believe that engines are numbered from the left to the right (from the pilot’s seat. Therefore since the X-15 is mounted on the right side of the fuselage, it would be between the fuselage and the number 5 engine, not number 4.
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I believe you’re correct, L-19
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Huh. I thought they were right to left. Thank you guys. I will fix that today. Appreciated. Tom D.
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L-19 Pilot, I jumped back in the editor and fixed that based on your observation. Thank you Sir. Appreciated.
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Tom…I had the privilege of interviewing Senator Knight on several occasions. He was truly an amazing man.
Another story about him occurred in 1967 when he was piloting the X-15 through 107,000 feet. His electrical system failed and he had no onboard systems to guide him. He continued at over mach 4 to a higher altitude and managed to bring the aircraft down to a safe landing by old-fashioned “seat-of-the-pants” flying.
Here is a link to raw footage of an interview I had with him in 2001 at the NASA Dryden Flight Test Center during the introduction of the X-34 vehicle.
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This is fantastic! Thank you Sir. Appreciated.
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Fascinating and interest article about an aviation milestone. Political comments are inappropriate and just dumb here.
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Not at all Frankie! It’s on every American’s mind.
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What a guy and what a pioneer. 47 years ago my 1950 plymouth would do 80 mph flat out, mach 6.7 is just a tad faster. Do we still have what it take to be the leader of the pack? YES!! Pioneers are still out there but it will be private industry that takes the lead. Lets get on with it.
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This was a very good article that describes a single record flight in less than 15min. The editors were kind enough to change it as comments brought forth a few mistakes. I grew up in Wichita, KS with aviation being our main source of income, which it still is, and grew up reading about our Aviation Pioneers from the Wright brothers to our current status…riding Russian rockets to space 😦 Our family has felt the loss of test pilots personally over the years. Each one of them knew the risks, but continued to strap in, and take to the skies. One in particular knew the airplane would kill him, and made it his mission to sacrifice himself so that others wouldn’t have the same fate. It may seem odd to those who aren’t familiar with test pilots, but that’s just how they live. The aircraft would go on to serve our country’s Naval flight training program for many years… it is the T-34C. Sacrifices weren’t made in vain, and sometimes that comes with the territory…anyone who flies knows the risks. Each time I takeoff there’s always a risk, whether going cross country, or even just staying in the traffic pattern. It’s what happens during that unexpected situation that makes the difference in the outcome of the flight. These guys are the tip of the spear when it comes to new innovations in aviation and space flight. Not many people have the courage to put their life on the line anymore. For those that do, I commend you on the highest level of respect. Maybe someday we will be back at the forefront of aviation/space in ALL fields! Ad Astra Per Aspera
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Thanks for the article!
There is a short NASA video on youtube that has closeups of the post flight aircraft: http://youtu.be/wHuBsBOF4R8
A main problem with the metric system is it’s lack of a unit between a meter and a cm. The foot is the perfect distance for aviation altitude. One thousand feet is perfect with respect to altitude measurement precision capability, especially above 30K and pre 1960. To get the same number of flight levels with even spacing you would have to have folks flying at odd altitude increments like 8333 meters.
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Trout, there are several less common metric prefixes that are not often used in all types of measurements.
Between one-thousandths and one thousand, the prefixes are:
milli- for 1/1000
centi- for 1/100
deci- for 1/10
none for the unit itself
deca- for 10
hecto- for 100
kilo- for 1000
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Thanks TigerNut,
I think you are confusing decimal with metric. Those prefixes are used for many non-metric units: Megabyte, Kiloton, Gigahertz. In any case, that doesn’t solve the problem: 8333 meters or 83330 decimeters isn’t any better. The meter is too long for a host of reasons. While we’re at it, some might say the km is too short. The nautical mile, being based on a minute of arc, is optimum for navigation. It has even been ‘accepted’ as an SI unit, but it is not ‘metric.’ Maybe they need to ‘accept’ the foot too!
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Another common misconception about hypersonic heating is that it is from friction when is is actually from compression of the air around the leading edges.
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Interesting. Trying to square that with Bernoulli’s Principle. I know that the principle changes above .3 Mach, but not sure how.
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In 1966, I was with architect Jim Fetridge in Palmdale, CA, when I designed the new headquarters building for the Society of Experimental Test Pilots. Don’t know if it was ever built, though, as I went to Washington, DC, to design two buildings for the USAF “Seek Dawn” program, constructed in Udorn Thani in northern Thailand and Da Nang, South, Vietnam. Used to watch the Blackbird pass over my home on its approach to EAFB. Now sharing with others the FAA’s Wright Brothers Master Pilot Award, and proud member of the QBs, and with 21,000 hours under the seat belt and harness, I’m still sorry that I never knew Mach 1. And, yes, at 83-years I still fly. Hats off to a really great article of days gone by.
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A great article and why all the negative comments this many years in the past? We shouldn’t be arguing about units of measurement – we should be appreciating what this gentleman did for aviation. When you come back from a mission – any mission, with pieces of your airplane missing,you have exceeded what the normal pilot would expect. Why don’t we jus celebrate what was done? I have flown T-33s, T-37s, T-38s, F-102s, F-100s, A-7s and F-16s and my hat goes off to this individual.
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Great article! Thank you. I believe equal time should have been extended to Pete’s second son,Steve, who currently holds Pete’s seat as a Calif. Senator and is running for Buck McKeon’s vacated US Congressional seat.
However, in all fairness neither son should have been mentioned in this article…..It’s all about Pete…..For Pete’s sake.
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Thanks for putting this article together. It’s too easy to forget the great events and people of the past. They remind us of the great heights to which men and their machines may rise, rather than convincing us we’re victims.
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i was in Palmdale at that time so much going on with all the test planes SR71 and many others the flying wing earlyer >B1 bomber later Loochead with the C5A largest plane at that time then came the L1011 what a history
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GOOD JOB TOM. REALLY HIT THE HIGH POINTS OF AN EXCITING FLIGHT AND SIGNIFICANT PART OF MY PROFESSIONAL CAREER.
JOHNNY ARMSTRONG
This is a first person version of Pete’s Max Mach Flight. Suggest you visit my web page to also see the photos. I have a few comments about your text and will expand on later.
Purpose of the flight was to expand the envelope to mach 6.5 with the Dummy Scramjet engine.
Was not a dedicated attempt to set a max speed record.
The external tanks was Lox on the left and Anhydrous Ammonia on the right to extend the engine burn time.
The airplane was 29 inches longer (between the body tanks) to contain a tank of hydrogen for the real scramjet test that was planned.
The sprayed on ablative material was initially pink but was found to be sensitive to LOX so a white coating was sprayed over it.
It was the dummy scramjet that fell off the airplane not the fin.
There was no “ballistic” portion on this flight, stayed under aerodynamic control.
In my book the real hero flying by Pete was on the flight that he had a total power failure that you mentioned. Perhaps I will add comments on that another time.
Regards to all,
Story from the book “Flight Testing at Edwards”
EXPANDING THE X-15 ENVELOPE TO MACH 6.7
by Johnny Armstrong
On October 3 1967 the X-15A-2 research aircraft achieved a maximum Mach number of 6.72 piloted by Major Pete Knight. The events that led up to the flight really began five years earlier when, on its 31st flight, the number two X-15, S/N 66671, suffered major damage during an emergency landing at Mud Lake, Nevada.
X-15 #2 Crash Landing at Mud Lake
Ten months prior to that emergency landing I had returned to Edwards as a civilian employee for AFFTC. Following my four years at Edwards in flight test engineering wearing the AF blue, I had accepted a job with NASA at Huntsville Alabama during which time I had worked on flight test of the Saturn rocket vehicle. Then near the end of 1961 I was contacted to see if I would be interested in returning to Edwards to work on the X-15. That was an easy yes. I had been missing airplanes so much that I would run out of the house to see the Southern Airways DC-3 fly over. So here I was back at Edwards working as the AFFTC flight planner on one of the most exciting programs of all times.
The ship 2 X-15 had entered the three-ship X-15 program in September 1959. In 1961 it had flown nine flights reaching a maximum Mach number of 6.04 and a max altitude of 217,000 feet.
X-15 crash landing at Mud Lake
NASA pilot Jack McKay had just launched from the B-52 mothership at 45,000 feet, lit the YLR-99 rocket engine and was on his way when Pete Knight, who was the flight communicator in the NASA control room, radioed for him to check his throttle position. Jack verified it was at the full throttle position and Pete advised him that the engine was only putting out 30 percent thrust.
This kind of situation is exactly why all X-15 flights were launched within gliding distance of a suitable dry lakebed. When Pete radioed that it was going to be a Mud Lake landing, Jack began a preplanned series of actions to make an emergency landing. He shutdown the engine and set up the turning pattern to Mud Lake, jettisoning the anhydrous ammonia and liquid oxygen propellants along the way. Due to several of Mr Murphy’s law things adding together, the strut of the left main landing gear failed on touchdown resulting in the aircraft turning sideways and then rolling upside down trapping Jack in his seat with his head next to the lakebed surface. Prior to rolling over Jack had had the forethought to jettison the canopy. The emergency crew that was pre-stationed at the site immediately moved into action. The Air Force helicopter pilot had the good judgment to hover over the X-15 blowing away the pungent fumes of the anhydrous ammonia still venting from the aircraft. The ground crew was able to dig a hole in the lakebed to provide enough clearance to extract Jack from the cockpit and get him on the way for medical attention. Jack would live to fly the X-15 again but he was an inch shorter due to crushed vertebra.
Six months after the Mud Lake landing accident a contract was signed with North American to repair and modify the aircraft to an advanced configuration to accomplish future experiments. The modified aircraft was returned to Edwards in February 1964 and made its first flight in June of that year. The main modification to the aircraft was the addition of two jettisonable external tanks to hold added engine propellant to provide a Mach 8 capability. This additional performance was desired for testing of a hypersonic ramjet engine then under development by NASA Langley. The airplane had also been lengthened by 29 inches to add room for a tank to provide hydrogen fuel for the ramjet engine. Other modifications included additional hydrogen peroxide tanks for propellant turbopumps for the longer engine burn time of about an additional 60 seconds, an openable hatch behind the cockpit for a star tracker experiment, and a modified canopy windshield. Additionally, an ablative coating was developed to be applied to the aircraft to protect the structure from the higher heating that would be encountered during the higher Mach number flights.
X-15A-2
The envelope expansion effort began with Flight 43 when Major Rushworth flew the first flight with external tanks. Consistent with the incremental approach of an envelope expansion program this flight was flown with the external tanks empty. Now there was a new constraint for the X-15 flight. The launch point not only had to be the necessary distance from Edwards depending on the max Mach to be flown, and also within gliding distance of a prepared dry lakebed runway, but also had to have a suitable area for the tanks to impact upon being jettisoned after they were empty. For this flight the X-15 was launched near Cuddeback dry lake about 60 miles North of Edwards on a heading that would result in the external tanks impacting on the Edwards bombing range. The flight was flown at 50 percent thrust to slow the acceleration. The flight went about as planned with the tanks being jettisoned at Mach 2.2 and 70,000 feet. The tanks impacted on the bombing range. The recovery chute system work properly for the ammonia tank and it was recovered in repairable condition. The LOX tank recovery chute did not deploy and the tank was destroyed on impact. With this flight the handling qualities of the X-15 with external tanks were verified to be adequate although somewhat worse than the simulator. It also validated the tank ejection and separation.
We See No Flow
Now we were ready to fly with full external tanks to Mach 6.0. It was to be the 45th flight of ship 2. It was also going to be last flight for Major Rushworth who had received his orders for his next assignment. (Rushworth flew more flights in the X-15 than any other pilot; a total of 34.) In retrospect, with twenty-twenty hindsight, flight 45 was destined for failure. The propellants were pumped to the engine from the internal tanks of the X-15 and the propellants in the external tanks were just pressure transferred into the internal tanks. From simulation studies we knew that the pilot would lose control of the X-15 rather rapidly if one of the tanks failed to transfer propellant. This was simply due to the moment that would be produced about the roll axis that could not be counteracted by the X-15 roll control that was produced by the differential deflection of the horizontal tails. We developed procedures in the simulator to be followed if one of the tanks failed to feed after launch. It essentially consisted of immediately setting up at conditions of angle of attack and dynamic pressure where tanks separation was predicted to be good. This consisted of first shutting down the engine, maintaining angle of attack to let the dynamic pressure decrease below 400 psf and then pushing over to low angle of attack and jettisoning the tanks. Then a landing would be made at Mud Lake. We practiced this over and over and over again in the simulator with Jack McKay serving as NASA 1, the flight controller. A few seconds after launch we would simulate the failure and Jack would make the canned call “we see no flow” and Rushworth would then initiate his abort actions.
We knew that the instrumentation available to establish that the tanks were feeding was an indirect indication, but it was felt that adequate pre-launch test would validate the instrumentation. This instrumentation was a pressure transducer across an orifice in the helium lines that pressurized each of the external tanks. (We had better instrumentation under development but it was not available for this flight.) We had verified the pressure transducer operation during a planned captive flight with propellants in the external tanks. At the four-minute-to-launch point on flight 45 we verified that the pressure sensors were working satisfactorily by jettisoning a small amount of propellant. After launch on flight 45 the ammonia-helium pressure did not respond. As a result, 18 seconds after launch Jack announced over the radio the dreaded call, “We see no flow on Ammonia Bob.” Bob immediately began setting up to jettison the tanks. He reduced the throttle to minimum thrust and pushed over to the desired 6 degrees angle of attack then hit the tank jettison switch. He forgot that he had not shut down the engine and proceeded to do so. The tanks separated cleanly although at much higher dynamic pressure than desired. The emergency landing at Mud lake was as routine as an emergency landing in an X-15 could be. Post flight analysis led to the conclusion that the fuel was, in fact, feeding from the ammonia tank properly. I carried the lesson learned from this flight with me for the rest of my active flight test career. Do not make critical flight decisions on inadequate/marginal instrumentation!
The next flight (49) was flown with the ventral fin on to Mach 5.2. It was primarily to familiarize Pete Knight with the handling qualities in this configuration that would be flown on the following flight with external tanks. Flight 50 was the first successful flight with propellant in the external tanks. Improved propellant transfer sensors (paddle switches) were installed for this flight. The flight was flown as planned and reached a max Mach of 6.3. Flight 51 was flown to evaluate the aircraft’s handling qualities with a dummy ramjet installed on the fixed portion of the lower ventral fin. The dummy ramjet was jettisoned during final approach as was normal for the movable lower rudder due to lack of adequate ground clearance for landing. The flight was flown without external tanks and reached a Mach number of 4.8. Next was a flight with the ablative coating and dummy ramjet installed but without external tanks. The flight was flown to Mach 5 and the ablative generally performed as expected although there were indications of high heating in the lower ventral fin adjacent to the ramjet that we did not fully appreciate until the next flight. The ablative coating was refurbished and the aircraft prepared for its “all up” flight with external tanks, ablative coating, and dummy ramjet.
Fastest airplane flight of the Century
All was ready on the morning of 3 October 1967 as Col Joe Cotton started each of the eight engines on the NB-52B mothership affectionately named “Balls Eight” from its S/N 008. Pete had already been in the small cockpit of the X-15 for over an hour performing the pre-flight checks with the ground crew led by Charlie Brown and Larry Barnett and a host of test support personnel in the NASA control room. After takeoff of the B-52/X-15 with Maj Cuthill following in an F-104 as chase 1, it took about 50 minutes to reach the launch point abeam Mud Lake approximately 170 nautical miles north of Edwards.
X-15A-2 Launch
” I reached up and hit the launch switch and immediately took my hand off to go back to the throttle and found I had not gone anywhere. It did not launch. So I probably just got my hand off of it, because I reached up and hit it again and it launched the second time. Launch was very smooth this time.”
As the X-15 was falling from the B-52 he lit the engine and locked on to 12 degrees angle of attack. He was pushed back into his seat with 1.5 g’s longitudinal acceleration. The X-15 rounded the corner and started its climb. During the rotation as normal acceleration built up to 2 g’s Pete had to hold in considerable right deflection of the side arm controller to keep the X-15 from rolling to the left due to the heavier LOX in the left external tank. When the aircraft reached the planned pitch angle of 35 degrees his scan pattern switched from the angle of attack gage to the attitude direction indicator and a vernier index that was set to the precise climb angle. The climb continued as the fuel was consumed from the external tanks, then at about 60 seconds he reached the tank jettison conditions of about Mach 2 and 70,000 feet. He pushed over to low angle of attack and ejected the tanks. He was now on his way and would not be making an emergency landing at Mud Lake. “We shut down at 6500 (fps), and I took careful note to see what the final got to. It went to 6600 maximum on the indicator. As I told Johnny before, the longest time period is going to be from zero h dot getting down to 100 to 200 feet per second starting down hill after shutdown.” Final post flight data recorded an official max Mach number of 6.72 equivalent to a speed of 4534 miles per hour. From there down Pete was very busy with the planned data maneuvers and managing the energy of the gliding X-15. He approached Edwards higher on energy than planned and had to keep the speed brakes out to decelerate. On final approach he pushed the dummy ramjet eject button and landed on Rogers lakebed runway 18. He indicated he did not feel anything when he activated the ramjet eject and the ground crew reported they did not see it. Pete said that he knew something was not right when the recovery crew did not come to the cockpit area to help him out of the cockpit, but went directly to the back of the airplane. Finally when he did get out and saw the damage to the tail of the X-15 he understood. There were large holes in the skin of the sides of the fin with evidence of melting and skin rollback. Now we are talking Inconel-X steel that melts at 2200 degrees F. Later analysis would show that the shock wave from the leading edge of the ramjet’s spike nose had intersected the fin and caused the aerodynamic heating to increase seven times higher than normal. So now maybe we knew why the ramjet was not there
.
X-15 dummy ramjet search
“I did not feel anything when I pushed the button for the ramjet. I understand that there were people saw that it did come off and others say that they never saw it, so I don’t know where it is.” So said Major Pete Knight during the postflight debriefing.
The flight records indicated that the ramjet instrumentation ceased functioning 25 seconds after the engine was shutdown and the airplane reached Mach 6.72. So at about Mach 6 during the deceleration/glide the burn through had taken place. The obvious conclusion then was that the ramjet departed at that time and had gone it’s merry way from over 90,000 feet to the desert floor below; over 100 miles from Edwards.
Lower Ventural Heat Damage
Later that afternoon as several of us were reviewing the data records we noted an abnormal decrease in the sensitive longitudinal acceleration trace (indicating a sudden decrease in drag). Although it was a small change, it was instantaneous. We decided to go on the assumption that this could be where the ramjet departed the airplane. Correlating the time of day with the flight parameters we found that it was at about the 180 degree point during the turn over the south area of Rogers Lake bed at about Mach 1.0 and 32,000 feet. The airplane was in a 57 degree left bank and, more importantly, pulling 1.6 g. Now I was confident that this could have been the time that the dummy ramjet began it’s independent trajectory. So next, I time-correlated the radar data and found the spot where this event occurred and the heading of the aircraft at the time. This then was the Initial Conditions of the ramjet flight. Next, I drew a line on a map along the heading at the time I suspected it separated from the X-15. I could say that I did a detailed calculation of the drag coefficient for a tumbling ramjet, then a 5th order curve fit of the potential trajectory, corrected for winds; – but actually I just made an engineering estimate (guess) at a downrange distance. It turned out that the estimated resting place was right on the Edwards AFB bombing range. Placing a mark on the map at my selected impact point, I then drew a line perpendicular to the estimated track. Next I pick out some recognizable ground reference points on the map. As it turned out I selected the Rocket Base on Lehman Ridge west of Rogers Dry Lakebed and a mountain peak in the San Bernardino mountains.
Dummy Ramjet Impact Site
Now it was time to present my theory to the team. There were many disbelievers of the theory who felt the dummy ramjet was way up north of Edwards. However, Bill Albrecht, the NASA Operations Engineer in charge of X-15A-2, was willing to humor and trust me. We contacted Joe Rief, the AFFTC airfield manager, and got permission to go wandering out on the bombing range. Bill and I got in a NASA radio equipped carryall van, radioed Eddie Tower, and headed out on the range. We drove east on the road on the bombing range with me looking for that general area where I had drawn the line on the map. We finally stopped the van and we walked down the road until I could hold my arms out and line up the Rocket Base and the mountain peak. At that point, I had Bill head North-East along my magic line and I headed South-West.
Shock! disbelief! glee! cold chills up my spine! …. after walking only about 200 yards, I saw the ramjet lying on the sand in between the tumble weed bushes in two major pieces.
I hollered with excitement to Bill but he was out of hearing range. So I ran back to the road and got his attention and we managed to back track to where I had seen it. There was a depression in the sand back up the track where it made first contact before coming to rest. We gathered up the nose cone and the machined conical steel pressure probes that were the very leading edge of the ramjet and headed back to the van.
The main body of the dummy ramjet was too large and heavy for us to return. It was almost quitting time at NASA when we carried our trophy up to the pilot’s office. I strutted around like the hen that laid the golden egg. Fitz Fulton, I recall was favorably impressed. The next day Albrecht and I went back out to the site to direct a Huey helicopter to the location. A cable was attached to the main part of the ramjet and it was flown back to NASA.
Inspection of the ramjet revealed that it also had major melting and damage due to the high aerodynamic heating in the area where it attached to the ventral fin. In addition, 3 of the 4 explosive bolts that held the ramjet on had been fired, undoubtedly due to the high temperature. The fourth bolt had structurally failed; which was apparently all that was securing the ramjet on the X-15 from about Mach 6 down to Mach 1.
Dummy Ramjet Damage
The X-15 program winds down
There was major damage to the structure of the fixed lower ventral fin from excessive aerodynamic heating due to shock wave impingement from the nose of the dummy ramjet. The aircraft was trucked to North American Aviation at LAX to be repaired, however it was to never fly again. Six months after the Mach 6.72 flight of ship 2 the Number 3 X-15 crashed near Randsburg, California killing Major Mike Adams. Over the next year the number 1 X-15 flew eight more flights with the last flight occurring on 24 October 1968, the 199th flight of the X-15 program. Several attempts were made to fly the 200th flight but to no avail. On 20 December Pete Knight was in the cockpit of the X-15 under the wing of Balls Eight ready to taxi to the runway when a freak snow storm moved over Edwards and the flight was cancelled. Thus ended the flying portion of the most successful X-plane program in history, however the analysis of the research data from the program continued for many years afterward.
How did I get involved in all this? RPRT. I was fortunate to be the Air Force flight planner during this time period on the X-15 program. I got to develop the flight plan using the X-15 man-in-the-loop simulator, train the pilots and then participate in the control room during the flight. Throughout my flight test career RPRT was good to me and allowed me to participate in some major flight test events and programs. It also presented me with the opportunity to work with some of the top people in the flight test community and this thing we called the test team. The AFFTC/NASA FRC X-15 team was one of the best. RPRT? – RIGHT PLACE RIGHT TIME.
X-15A-2 in USAF Museum sm
The above photo includes the X-15A-2, the X-24B, and the Martin SV-5J labeled like the X-24A. See the X-24B Runway Landing story to understand. Photo is from the National USAF Museum web page.
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Great tale, thank you Tom. Enjoyed the comments about metric/imperial measurements.
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What a great story! (I flew 3,000 hrs in the RCAF, then 29.5 years for Air Canada, and NEVER “lost” an engine in 21,000 hrs.)
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The entire story line was fantastic….that is until the very end, where someone decided that a politically negative footnote was worthy of print. That’s sad, gentlemen.
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I don’t know that the note at the end is negative. There is no judgement on the information- only the information itself, reported objectively and without judgement. Any judgement as to the positivity or negativity is left to the reader.
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Incredible story about a remarkable man. Sad so much of the comments are so nit picky and whinney. Sound like a bunch of momma boys bitching. Just stop and pay respect to one of the most remarkable explorers in our lifetime.
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Like another commenter questioned, I would like to know how the speed at Mach 6.7 was measured.
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By multiple radar measurements from several radar stations gave his velocity over ground, combined with the outside air temp. & density.
That’s why these speed numbers usually get adjusted after a flight as the numbers get crunched finer & finer.
Plus he had his own inboard equipment that gave a rough number.
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Thanks!
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