The same can be said about Armstrong’s continued involvement in the X-15 program. Twice during Karen’s illness—on December 20, 1961, and January 17, 1962—Armstrong piloted the rocket plane, his third and fourth of seven X-15 flights overall. Both flights came off without any hitch, at least not in Armstrong’s performance. Preparing for an X-15 flight took high intensity from everyone involved, but no one felt the pressure like the pilot. Furthermore, the X-15 flight scheduled for December 1961 with Armstrong at the helm was to be the first run of the number-three aircraft. Already the X-15-3—or more precisely, the plane’s powerful new XLR-99 rocket engine—had a checkered history. On June 8, 1960, during what was supposed to be a final ground test by the contractor, the XLR-99 exploded on its test stand. “It was the biggest bang I’d ever heard,” said North American pilot Scott Crossfield. “Fortunately for me and the airplane, the explosion blew the forward section—the tanks and the cockpit—out of the major part of the blaze. The firemen were right on their toes and they moved in to blanket the tanks and the fire area with foam.” At first everyone thought the rocket engine had blown. As is often the case, the first impression was wrong. As soon as all the scattered parts could be found and cooled down enough to touch, a disenchanted group of engineers mostly from North American began a thorough investigation into what caused the explosion. Eventually the investigators determined that a frozen regulator, a faulty relief valve, and a rapid buildup of back pressure caused the center structure of the X-15’s ammonia tank to ram and smash open the control system’s hydrogen peroxide sphere. Not until the entire pressurizing and pressure release systems were thoroughly analyzed, redesigned, tested, and retested could another pilot step into the X-15 cockpit. By the time Armstrong got into the plane in mid-December 1962, the first flight of X-15-3 had been delayed by sixteen months, at a cost of $4 million.
The long delay and extra cost heightened anxiety over Armstrong’s flight. “There’s always concern about whether there had been damage that you didn’t recognize,” Armstrong admits, “but the engine went back to the plant and got torn apart and reassembled.” Following a new round of engine ground testing, Neil had every reason to think that the X-15-3’s problems, at least those causing the June 1960 explosion, had been solved.
Rebuilding the aircraft gave North American the opportunity to update the newest X-15 airplane’s research equipment and outfit it with the MH-96 “black box” that Armstrong had been helping Minneapolis-Honeywell to develop for the program. Flight testing the innovative adaptive control system became the primary purpose of Neil’s December 1961 flight.
The flight was scheduled to launch on December 19 but was aborted when instrumentation involving the X-15’s ball nose did not read correctly, so it got pushed back to the next day. The flight (number 3-1-2 and the forty-sixth in the program) was not without problems. Immediately upon being dropped by Major Jack Allavie from his B-52 over Silver Lake east of Death Valley, all three axes of the new stability augmentation system on the MH-96 disengaged and “a severe right roll occurred with accompanying yaw and pitch excursions.”
Armstrong recalls that the failure did not cause him much trouble: “One of the aspects of the MH-96 was its reliability. It was a system designed to run for 76,000 hours between failures.” As it turned out, the system experienced a blip a lot sooner—at the very start of Neil’s flight. Armstrong managed to reset the system on the first try, “so it wasn’t really a problem” once he recovered from the strong right roll. “That was a medium-speed flight,” Neil explains. “I think it was faster than I had ever flown before, though,” up to a speed of Mach 3.76, or 3,670 mph. “The flight followed a carefully programmed order, principally to check out the operation of the MH-96, and I’m sure no one wanted to go to extreme flight conditions, extreme loadings, on the system on the first flight.”
Armstrong observed that the MH-96 system produced at least one unconventional flight characteristic: “Most airplanes have what is called ‘speed stability,’ that is, you set it at 250 knots, it tends to stay at 250 knots. But with the MH-96 flight control system, which was a rate-command, attitude-hold system, it had no affinity for staying at a particular speed. It tended to stay at its particular angle, but if the thrust did not match the drag, the plane would either speed up or slow down, whichever was appropriate, without any apparent signal to the operator.”
Air-launched at 14:45:50 Pacific time, Armstrong landed the X-15 a little less than ten and a half minutes later, after flying a distance of 150.9 miles. The highest altitude reached was 81,000 feet, which was not as high as Armstrong had gotten in several of his F-104 zooms. With Major Daniels, LCDR Petersen, and Major Rushworth flying chase, Armstrong brought the X-15-3 down gingerly onto Rogers Dry Lake just southwest of Boron. “Although skid contact seemed quite gentle,” Armstrong wrote in his pilot’s report, “nose wheel touchdown and impact seemed to be somewhat harder than that of previous flights in #1 airplane. [Neil never flew X-15-2.] It was attempted to keep the run-out along the painted right hand stripe of the runway. With a light to moderate left cross wind, the airplane finally veered to the right of the painted stripe and could not be returned.”
Armstrong’s next X-15 flight came on Wednesday, January 17, 1962, a week and a half before Karen Anne’s death. The flight was again to evaluate the MH-96 system and was the first time for Armstrong past Mach 5. It was also the first time he ever flew above 100,000 feet. In fact, he surpassed both marks, with a speed of Mach 5.51 and an altitude of 133,500 feet.
“I think it went pretty much on plan,” Neil relates. Launched by a B-52, this time over Mud Lake to the north of Edwards, the X-15-3 traveled a distance of 223.5 miles in a little less than eleven minutes before touching down safely on Rogers Dry Lake at 12:11:01 in the afternoon. Throughout the flight, Armstrong gave the X-15’s sidestick quite a workout. Flying chase with Petersen and Rushworth were Captain Henry C. “Hank” Gordon, one of the air force pilots later to be named along with Neil for the Dyna-Soar program, and Captain James McDivitt, future commander of the Gemini IV and Apollo 9 space missions.
His X-15 flight on January 17, 1962, was Armstrong’s last flight of any kind until a week after Karen’s funeral, when on February 6 he took an F5D up over Edwards for a low L/D approach. In the entire month of February, Neil flew only three other days, on the twelfth, thirteenth, and sixteenth. The first two of these days involved flights in an F-104, one for “pilot proficiency,” and the last another low L/D approach in an F5D. Armstrong worked on Dyna-Soar in Seattle from February 26 to March 20.
Upon returning to work at Edwards on Monday, March 23, Armstrong immediately began to prepare for his next X-15 flight (flight 3-3-4), scheduled for five days later. Most of his flying leading up to the twenty-eighth involved “touch-and-go” landings in an F-104. These flights amounted to practice landings of the X-15. When the day for the actual X-15 flight arrived, clouds and hazy overcast limited visibility, pushing the schedule back one day. On March 29, the X-15’s stable platform heat exchanger iced up, and a faulty fire detector caused the plane’s fire warning light to pulse intermittently. The following day, the launch panel in the B-52 showed a potential problem involving the rocket engine’s cooling gas, leading to a stressful abort at zero seconds in the countdown. The day after that, the MH-96 analyzer failed during a preflight check.
Not until the morning of Wednesday, April 5, did Armstrong manage to make the flight (flight 3-3-7). Then, just as he was being dropped at altitude above Hidden Hills north of Death Valley (across the Nevada line), his rocket engine did not ignite. “Before lighting the engine, or attempting to light the engine, I’m sure that some malfunction lights lit up,” Armstrong recalled in his postflight debriefing later that day, “but I did not see any light. All I saw was the igniter pressure go to zero and silence.”
In an X-15, there was only time enough for one relight. The remaining time until touchdown was required to complete the jettison of the propellants. If a second reli
ght was attempted, the X-15 would still have some propellants in the tanks at landing, which, in Armstrong’s words, “was not desirable.” He recalls what “sure seems like a long time the second time for that engine to light up.”
Accelerating to a top speed of Mach 4.12, Neil thundered up to 180,000 feet. It was the first time he had reached a high enough altitude to fully integrate the MH-96 reaction controls. The test flight spanned 181.7 miles in a little over eleven minutes before landing at Rogers Dry Lake.
The airplane still had not been flown to the point of testing the MH-96 system limit, or “g limiter,” in part designed by Armstrong, to prevent the pilot from exceeding 5 g’s, and he “felt the obligation to demonstrate every component and aspect of the MH-96.”
It was this commitment that led to Armstrong’s making what some came to feel was his biggest pilot error in the X-15 program.
Flight 3-4-8 occurred on Friday, April 20, 1962. Armstrong remembers, “It was the highest I’d ever gone”—to 207,500 feet, an altitude that remained his highest until Gemini VIII. “The views were spectacular. The system ran pretty well up there. The reaction control systems were operating satisfactorily ‘across the top.’ It kept a good attitude reference. Everything worked well. It was well outside the atmosphere so that we were flying completely on reaction controls. Aerodynamic controls were completely ineffective, like flying in a vacuum.”
Coming down from peak altitude, part of the flight plan was to check out the g limiter. Armstrong explains, “I thought I got the g’s high enough, but it was not kicking in. That was my job, to check out that system.”
Armstrong let the X-15 nose up just a little, causing it to balloon to a high enough altitude—roughly 140,000 feet—where “the airplane returned to the wings-level attitude with essentially no sideslip. At about fifteen or sixteen degrees angle of attack and four g, I elected to leave the angle of attack in that mode and I was hoping that I would see the g limiting in action. We had seen g limiting on the simulator operation at levels approximately four g to four and a half g and it wasn’t obvious that we were not having any g limiting, so I left it at this four-g level for quite a long time hoping that this g limiting might show up. It did not, and apparently this is where we got into the ballooning situation.”
Over the radio, “NASA 1” back at the main flight control center told Neil rather emphatically, “We show you ballooning, not turning. Hard left turn, Neil! Hard left turn!” “Of course I’m trying to turn,” Neil explains forty years after the flight, “but nothing’s happening. I’m just on a ballistic path and I get over on to a very steep bank angle trying to pull down into the atmosphere. But the aerodynamics are not doing anything. The plane’s going to go where it’s going to go. It’s on a ballistic path. They’re telling me on the ground to ‘Turn!’ but that’s not any help to me. They could see on the instruments that my servos are at full stabilizer turning position. I rolled over and tried to drop back into the atmosphere, but the aircraft wasn’t going down because there was no air to bite into.
“I had no reason to suspect that ballooning would cause any trouble, because I had fiddled around with this lots of times in the simulator and never, never had any kind of problem with bouncing out like that.”
Eventually the X-15 fell back down into the atmosphere where Armstrong was able to start making the turn. But by that time, Neil recalls, the airplane had gone “sailing merrily by the field”—at a speed of Mach 3! By the time he rolled into a bank, pulled up the angle of attack, and started to turn back in a northeasterly direction toward Edwards, Armstrong found himself approaching Pasadena. Neil was forty-five miles south of Edwards and still above 100,000 feet. (Subsequent Edwards lore suggesting that Neil flew the X-15 as far south as the Rose Bowl seems an exaggeration, since forty miles south of Edwards is substantially north of the Rose Bowl. Downward visibility was very limited for the X-15 pilot, so Neil did not know how far south he got.)
“It wasn’t clear at the time I made the turn whether I would be able to get back to Edwards. That wasn’t a great concern to me because there were other dry lakes available. I did not want to go into another one, but I certainly would if I had needed to. My easiest choice was to land at a lake called El Mirage, and I could easily get there. The only other alternative at that point would have been Palmdale municipal airport, and I didn’t want to get into their traffic pattern.” So Armstrong committed himself to trying for Edwards: “After I got on the track—the northbound track for Edwards—it was clear that I was going to be able to try to go in. I’d have to make a ‘straight in.’”
Neil: I have the home base in sight, Joe [Walker].
NASA 1: What is your visual estimate of the location?
Neil: Looks like I’m pretty, in pretty bad shape for the south lake bed.
NASA 1: You’re at eight degrees alpha [angle of attack].
Neil: Affirmative. And I’m going to jettison [auxiliary fuel] now.
Chase: What altitude, Neil?
Neil: Got 47,000.
NASA 1: Yes, we check that. Have you decided what your landing runway is yet?
Neil: Let me get up here a little closer. I can definitely…see the base now.
NASA 1: Yep.
Neil: Check head bumper [at the top of the ejection seat]. I’m 41,000 feet.
NASA 1: We’re 26 miles to the south lake and have you at 40,000.
Neil: Okay.
NASA 1: Stop jettison on the peroxide.
Neil: Rog. Okay, the landing will be on runway 35, south lake and will be [a] straight-in approach. I’m at 32,000, going to use some brakes to make it. Okay, I’m about, approaching, pretty hard to tell from here. [At this point Armstrong is using speed brakes to reduce energy, which in retrospect confirms that his return to South Base could not have been as close a call as some people at Edwards later suggested.]
Chase: Okay, I’ve got you now. I’m one o’clock to you.
Neil: Okay.
Chase: Don’t know if I will be with you, though. [The chase was not sure he could rendezvous before Neil landed, since he had been in position to join up for a landing on the north, rather than south, lake bed.]
Neil: Okay, going to use some brakes to get in. Okay, the ventral is armed and the brakes are in. [At the rear end of the X-15 were vertical stabilizers placed above and below the fuselage; these were the ventral and dorsal fins. Prior to landing, the ventral fin needed to be jettisoned by triggering explosive bolts. Had Armstrong jettisoned the ventral even earlier, he would have reduced the drag and extended his glide time.] I’m landing on 35 and I’m about fifteen miles out from the end now. Peroxide-low light is out, on again, source is 1,600 pounds. I’m 290 knots.
Chase: Coming up on your left.
Neil: Okay, I haven’t got hold of you yet. And a little brakes here. I’m going back to pressurize. Going to land in sort of the middle of the south lake bed. Brakes are in again, 280 [knots].
Chase: Henry [Gordon], I’ll take the left side if you want me to.
Chase: Rog.
Neil: You want to call the ventral jettison, Henry?
Chase: Okay.
Neil: Little shorter than I thought.
Chase: You can punch it [the ventral] off any time you want to, Neil, for drag.
Neil: Oh, I should have done that before, shouldn’t I?
Chase: Yep. Start your flaps down now. Off. Okay, you’re well in, go ahead and put her down. Very nice, Neil.
NASA 1: The posse will get there shortly.
Chase: In about thirty minutes! [A sarcastic reference to the fact that all the recovery vehicles were up at the original landing site on the north lake bed.]
H-21 [helicopter]: We’ll be there, Neil.
Armstrong’s X-15 flight of April 20, 1962, established X-15 program records for the longest endurance (12:28:07) and for longest distance (350 miles, ground track). Local Edwards lore still relates that Armstrong was trekking right down amid the Joshua trees as he made his landing on the southern
tip of Rogers Dry Lake; in fact, the jest was that the Joshua trees were passing by above Neil. But that was a gross exaggeration devised by the boys in the chase planes, the only ones close enough to Neil’s set-down point to know exactly where it occured.
Fellow NASA test pilot Bruce Peterson was situated on the north lake bed waiting to send up locator flares. “Neil was supposed to land on runway 18 [“18” was short for 180-degrees heading] on the north lake bed,” Peterson relates. “Then I heard on the radio that he was going to go to the south lake, so I got in my vehicle and I must have been doing a hundred miles per hour, racing down that lake bed to see if I could get to the south lake bed and throw some flares. I watched him come in and looking across the lake, you can’t see relative distances. But I knew he was close to the edge of the lake.”
One of the engineers who monitored the flight, John McTigue, remembers “later kicking myself in the backside because I didn’t tell Neil to get rid of the lower ventral, because that would have reduced the drag some. But it was the only airplane that the little old lady in Pasadena had ever seen come roaring above her, the X-15!” Though he did not see Neil’s landing, McTigue heard that Armstrong barely made it back to South Base. Gathering for the postflight debriefing, McTigue heard Joe Vensel, the head of FRC flight operations, ask pilot Forrest Petersen, “How far was Neil from the Joshua trees?” Petersen thought for a moment and said, “Oh, probably a 150 feet or so.” A wry smile coming to his face, Vensel asked, “Were the trees to his right or left?!”
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