SP-4220 Wingless Flight: The Lifting Body Story






[41] For the 350-mile trip from Edwards Air Force Base to the NASA Ames Research Center at Moffett Naval Air Station in Sunnyvale on the southern end of the San Francisco Bay, we removed the "elephant-ear" elevons from the M2-F1 and loaded the vehicle on a flat-bed truck. The ten-foot width of the lifting body on the truck's bed caused it to be classified as a wide load, requiring two escort vehicles, one in front and one in back of the truck. The M2-F1 created some sensation along the route. The drivers had a lot of fun talking about it to the people who crowded around them on stops along the way, wanting to see it up close.

The NASA Ames Research Center is located in the heart of Silicon Valley, a few miles down the road from Stanford University. Moffett Naval Air Station had been the western operational base for Navy dirigibles in their heyday. The Navy dirigible Macon was a flying aircraft carrier, launching and recovering prop-driven fighter airplanes from its belly. The Navy was very proud of its dirigible fleet until two disasters happened: the Shenandoah crashed in an East-coast wind storm, and the Macon went down in the ocean off Monterey, California. Two hangars that housed these dirigibles still exist at Moffett. These hangars and the NASA Ames wind tunnel-its return section as tall as a ten-story building-are such prominent structures that they can be seen for miles by ground or air.

A bank of very large fans driven by electric motors generates the "wind" in the test section of the tunnel. Routed to the facility are power lines and a special substation. Operating the wind tunnel in those days required special coordination with the Edison Electric Company because of the need to have operators on standby to turn on extra generators when the tunnel was in use. To avoid conflict with peak daytime industrial electrical needs, wind-tunnel tests were often scheduled during night hours.

While it could take months or even years to get tests scheduled for this tunnel, Al Eggers had assigned a priority to the M2-F1 wind-tunnel tests. We had two weeks to conduct them. We had put together a test team consisting of both Vic Horton's hardware people and some of the analysis team. Horton participated in some of the data analysis, co-authoring with Dick Eldredge the M2-F1 flight and wind-tunnel lift/drag results. 1



M2-F1 mounted in the Ames Research Center's 40 x 80-foot Wind Tunnel for testing.

M2-F1 mounted in the Ames Research Center's 40 x 80-foot Wind Tunnel for testing. (NASA photo A-30506-15, also available as NASA photo EC97 44183-3)


[43] While the NASA Ames crew operated the tunnel, our crew from the NASA Flight Research Center worked with the M2-F1- quite a different sort of adventure for a bunch of desert rats used to airplanes that fly in open sky over miles of sand and rock. I found a trailer park nearby where I could park my small travel trailer for the two weeks, having brought my wife and our two daughters along as well.

The inside of the wind tunnel was an awesome sight, especially at night. One night, as the M2-F1 team was preparing for a test, I took my family on a tour of the tunnel. We boarded an open-cage elevator on the ground floor, then rose through a darkness of steel beams and unlit open spaces to the floor of the dimly lit test section. The tunnel was a huge closed-circuit system in the shape of a race track, its entire length being about half a mile. Soot from engines stained the walls, making the interior of the tunnel dark and dingy, adding an eeriness to the atmosphere. My wife, Donna, said the tunnel would be a wonderful place to make an Alfred Hitchcock movie.

When we were ready to begin wind-tunnel testing, we had the M2-F1 hoisted high overhead by a crane, then lowered through a large hatch in the top of the test section. The vehicle sat 20 to 25 feet off the floor on top of three tapered poles resembling stilts that were mounted on a turntable balanced on the tunnel's floor, the M2-F1 attached near its landing gear to the poles.

What we did in testing the M2-F1 was unique, something that probably couldn't be done now due to NASA's emphasis upon safety. We didn't have remote controls on the M2-F1, even though most wind-tunnel models of vehicles have them. To move the testing along more rapidly, we talked the NASA Ames wind-tunnel crew into letting us take turns sitting in the cockpit, setting the pilot's controls at different settings by using plywood form boards. By keeping someone in the cockpit during the testing, the wind tunnel could be kept running, with necessary control changes made by the person in the cockpit. Otherwise, it would have taken a long time to get the tunnel's wind speed stabilized each time we started up again after shutting down the tunnel to make a change in control setting, angle of attack, or sideslip.

Ed Browne, Dick Eldredge, Milt Thompson, and I tried out the cockpit for size. I found it scary sitting up there over 20 feet off the ground inside a plywood barrel-like vehicle perched atop three spindly poles inside a dark cavern, shaking around as a windstorm screamed past at 135 miles per hour. I then decided that the best use of my time would be directing the tests in the safe confines of the wind tunnel control room. With the wind-tunnel operators and I peering at the wind tunnel pilots through thick windows in the tunnel walls, they felt like some kind of biological laboratory specimens under scrutiny.

We had an intercom system set up for communicating between the cockpit and the control room-a much better way to communicate, we felt, than holding up messages scribbled on paper to be read through the vehicle's canopy, especially when asking for help during sudden attacks of claustrophobia or because of a final call of one's bladder for relief. Whenever the wind tunnel pilots moved the controls or the wind [44] velocity increased, they could feel the vehicle move as the poles supporting it flexed, an experience they all found disconcerting until they got used to it.

Milt Thompson, however, even wanted to conduct another wind tunnel test. As he said years later, "I tried to get them to attach a rope to it and let me actually try to fly it in the tunnel, but they wouldn't go along with that."2 What Milt had wanted to do was sit in the cockpit of the M2-F1 set on its wheels on the floor of the tunnel, the tow-line tied upstream of the vehicle. However, the tunnel's crew was not very enthusiastic about Milt's suggestion, saying they could see the tow-line breaking and Milt and the M2-F1 ending up plastered against the turning vanes at the end of the tunnel. Even offering to attach slack safety lines during his "flight" did not keep the tunnel's crew from turning thumbs-down on Milt's request.

Before we started the formal data-gathering part of the tunnel tests, Milt found excessively large stick forces at aft stick positions while sitting in the cockpit and moving the controls around at different air speeds and body angles in the airstream. To minimize hinge moments, we had designed the outer elevons' pivot points to be slightly forward of the elevons' center of pressure. However, the trailing-edge body flap had been hinged at its leading edge, producing large hinge moments and stick forces. Using the wind-tunnel's fabrication shops, Vic Horton and his crew attached stand-off aluminum tabs on the body flap to help hold up the trailing edge, alleviating force on the stick. While the tabs didn't entirely eliminate the stick force, Milt considered it enough lessened to be tolerable.

There was another problem involving a phenomenon called a "Kármán vortex" that can also occur behind large trucks on the highway. A driver in a car at certain distances behind a truck in calm wind conditions sometimes can feel a "Kármán vortex" as the airstream whips back and forth. With the M2-F1, at certain airspeeds in the tunnel, a low frequency beat was being fed back to the vehicle's control stick. After taping tufts of yarn around the aft body and control surfaces of the M2-F1, we discovered that a large, oscillating Kármán vortex was coming off the body's base and beating against the body flap. 3

The NASA Ames resident aerodynamicist, experienced in vortex flows, suggested that if we could change or disturb the base pressure slightly, we might be able to break up the single large vortex into a bunch of much smaller ones that would not beat so badly on the flap control surface. Once again, Vic Horton's crew went back into the shop, this time making two aluminum scoops and mounting them at the base on each side of the vehicle's body. The idea was to scoop air from the sides of the body into the cavity behind the base, thus increasing the base pressure and, we hoped, destroying the Kármán vortex. Milt climbed back into the cockpit, and we tested the M2-F1 [45] with the scoops. It worked. Having made two aerodynamic fixes to the vehicle, we were ready for the formal data-gathering portion of the wind-tunnel tests.

Dick Eldredge took the first shift, sitting in the cockpit and setting the controls with the plywood form boards. We were on a roll that day, cranking out data faster than we had before. Earlier, we had lost three days of our scheduled time in the wind tunnel while waiting anxiously as the tunnel's crew repaired its balance-data measuring system. After Eldredge had spent two hours in the cockpit, we asked him over the intercom if he would like someone else to take over. He declined. We asked him again every two hours until we had tested for eight hours straight with Eldredge in the cockpit, knowing he had only some water with him in the cockpit. Finally, after eight hours, Eldredge admitted that he was getting hungry and needed to go to the bathroom.

Data from the tunnel's measuring system came to us on tabulated sheets showing side, vertical, and aft force measurements as well as moments of roll, pitch, and yaw. The sheets also provided air speed, angle of attack, and sideslip. The M2-F1 "pilot"-whoever happened to be sitting in the cockpit during the test-also made notes regarding the control settings. We then correlated the data from the notes with that from the tunnel's measuring system.

The analytical team members hand-plotted on graph paper every single data point, using a room downstairs that had been set up for us. Hundreds of hours were involved in this work, each of us on the analytical team-Ken Iliff, Bertha Ryan, Harriet Smith, and myself-doing our share of the work. I think even Milt Thompson plotted a few points.

Whenever I saw the hardware crew had completed a task, I put its members to work plotting data as well. Once, when I did this, I didn't make myself too popular. They had been entertaining themselves with a game during a work lull, while the tunnel's crew was doing calibration checks on the measuring system. One by one, they were running across the tunnel floor, up the side of the curved floor, and putting a chalk mark as high on the wall as they could reach, the object of the game being to see who could make his mark the highest. After watching them for awhile, I had said, "If you guys aren't doing anything, come on down and help us plot data." Obviously, plotting data wasn't nearly as much fun as the game they had been playing, but they helped us anyway. A few years later, those marks were still on the tunnel's walls. Now, over thirty years later, I have often wondered if those marks are still there. If they are, they are probably covered up with additional layers of soot by now.

Some aspects of the good old days weren't so good, and one of them was having to spend those hundreds of hours hand-plotting data. Today, most wind tunnels have fully automated data systems with final plots rolling out of the machine soon after a tunnel test is finished. Today's engineer can analyze the data as it comes from the tunnel tests, modifying the test program in real time if an aerodynamic quirk shows up.

When our two-week stint at the NASA Ames wind tunnel ended, we packed up our data and trucked our little lifting-body vehicle back to its hangar at the NASA Flight Research Center. When we replaced the data in our simulator, based on the small-scale wind-tunnel tests, with the new data from the full-scale tests, we saw a difference. [46] We knew that the only way to confirm the flight potential of the M2-F1 was to move on at once into actually flying it.


Gearing Up for Flight-Testing the M2-F1


Immediately after returning to the NASA Flight Research Center, we began planning how to move directly into air-towing the M2-F1 into flight. The tow-plane we decided to use was NASA's R-4D utility aircraft, a Navy version of the Air Force's C-47, both being military versions of the legendary DC-3. Fondly dubbed the "Gooney Bird," the Douglas C-47 aircraft played a significant role during World War II as a glider tug during campaigns in Sicily, Normandy, and elsewhere. Now, the Gooney Bird was about to enter aviation history again as the tow-plane for the first lifting-body vehicle.

NASA's Gooney Bird was being used in several other ways, mostly as a transport aircraft. It had long been used at the Flight Research Center to shuttle people to and from Ames in support of joint activities. It was also being used in the on-going X-15 program to ferry people and equipment between Nevada lakebed emergency-landing sites and remote radar-tracking stations.

For a while we couldn't find a glider tow-hook for the Gooney Bird. Of World-War-II vintage, this device was no longer in the military inventory. Finally, Vic Horton scrounged up one from a surplus yard in Los Angeles. We had no more than attached it to the tail of our Gooney Bird and run the release-line control up to the cockpit of the M2-F1, however, than we began to see dark clouds gathering over the lifting-body project as other people at the Flight Research Center began to believe that we were actually serious about flying the M2-F1.

First, Joe Vensel, local NASA Chief of Flight Operations, said that we couldn't fly the M2-F1 without installing an ejection seat. Eldredge and I told Vensel that we wished he had come up with this requirement when we were designing the vehicle. Fortunately, since the pilot sat at the center of gravity in the M2-F1, we found that we could add the ejection seat without unbalancing the lifting body. However, when we added the ejection seat and instrumentation, the M2-F1's weight rose to 1,250 pounds. To fly, the heavier vehicle required higher airspeeds than we had anticipated.

Because of this change, Dick Eldredge, Meryl DeGeer, and I went back over the structural load capacity of the M2-F1. We found that the most critical part of the structural design was the bending moment at the base of the vertical tails. The most severe flight condition, consequently, would be a high-speed dive in which the vehicle was forced into a high sideslip angle with the roll control (elevons) put in the wrong direction, adding to that bending moment. Using the simulator, we found that the only way a pilot could encounter that dangerous condition would be by attempting an aerobatic roll. A placard we added to the instrument panel in the cockpit clearly defined this limitation in four words: "No Aerobatic Roll Maneuvers."

At that time, the Weber Company was in the process of developing what we needed, a zero-zero ejection seat-that is, an ejection seat that operates even with the [47] aircraft on the ground standing still (at zero altitude and zero velocity). The company was modifying a lightweight seat designed for the T-37 jet trainer to use a rocket rather than a ballistic charge for ejection. Joe Vensel came up with funds from his operations budget to pay Weber for this ejection seat to install in the M2-F1.

Very likely, the M2-F1 used one of the first zero-zero ejection seats ever made. Since Weber had not yet fully demonstrated the seat at the time, we arranged for a series of tests at the south lakebed where ejection seats were generally tested. Meryl DeGeer and Dick Klein worked with Weber in demonstrating and testing the seat.

Dick Klein constructed a plywood mockup of the M2-F1's top deck and canopy through which to fire a dummy sitting in the ejection seat. This dummy was fired up six times in the ejection seat. On each of the first five times, something went wrong and we had to make an adjustment.

Meryl DeGeer remembers Milt Thompson watching one of these tests. After the dummy and the seat smashed through the M2-F1 canopy mockup with rocket burning bright, the dummy separated from the seat at the top of the trajectory. The seat safely descended to the ground on a special parachute that Weber had added to save the seat for use in future tests. But the dummy, with its parachute still unopened, went sailing through the air head-first like Superman, its arms flapping.

As the dummy arched toward the ground, DeGeer glanced around at Milt Thompson. His face contorted, Milt was shouting at the dummy, "Flare! Flare! Damn you, flare!" The dummy ignored him and kept on flapping its arms as if trying to fly. The dummy crashed headlong into the bushes. Only then did its parachute flare open.

Everything worked well on the sixth test of the ejection seat, and the seat was installed in the M2-F1 without repeat testing to prove reliability. A year later, in 1964, a pair of the updated version of this seat was installed in the NASA Lunar Landing Research Vehicle (LLRV), the same seat that saved the lives of astronaut Neil Armstrong and pilot Joe Algranti when control systems failed in the Lunar Landing Training Vehicle at Johnson Space Center during training missions for landing on the moon.

Next, Thomas Toll, Chief of the Research Division, began to have serious doubts about flying the M2-F1. A respected but conservative researcher who had transferred to the NASA Flight Research Center from NASA Langley in Virginia, Toll had been one of the men responsible for the concept of the X-15. He felt that as long as we weren't flying the M2-F1 more than a few feet off the ground on car-tow, the data return was likely worth the effort, cost, and risk. Merely flying the M2-F1 on car-tow, he believed, would be a good learning tool for sharpening engineering skills in aerodynamics and stability and control, and it was also possible that the car-tow flights might even produce some useful data on lifting bodies. 4

However, we were now thinking about flying the M2-F1 to high altitudes behind a tow-plane and that, he felt, was quite another matter. His serious misgivings seemed mostly to have to do with the fact that Milt Thompson had encountered a dangerous [48] lateral oscillation the first time he flew the M2-F1 on car-tow. Toll did not believe that any potential return in air-tow flight data was worth the risk to the pilot.

Toll had two other main reasons for opposing air-towing the M2-F1 into flight. First, he felt that the very low wing- or body-loading at which we were flying was not representative of a potential full-scale spacecraft, for an actual spacecraft the size of the M2-F1 would most likely weigh 10,000 to 15,000 pounds, ten times the weight of our M2-F1. Secondly, we weren't using any of the automatic control features, such as rate damping or automatic stabilization, that probably would be used in a spacecraft.

Paul Bikle tried to reason with Toll, assuring him that he felt it was worth the risk and that he would like to have Toll's endorsement. But Toll refused, going on record as refusing to endorse the planned M2-F1 air-tow operation. When Bikle went ahead and gave us the green light to proceed without the concurrence of NASA Headquarters or his own Chief of Research Engineering, he essentially was making a decision that could put his career with NASA on the line.

What Bikle did was an act of the kind of courage that I had never before seen in a manager. Essentially, he risked his career to support something that he believed in. There are basically two kinds of courage in the aerospace industry: the courage of test pilots who risk their lives, and the courage of managers who risk their careers to support decisions they believe are right, even when others disagree strongly. In his book The Right Stuff, Tom Wolfe was correct to immortalize pilot as heroes.5 On the other hand, program managers are responsible not only for the pilots who have "the right stuff" but also for the people involved in the program who have "the real stuff," as Wolfe labels it. When test pilots pay the ultimate price while risking their lives to test new aircraft, history remembers them as heroes who gave their all to aeronautical research. However, when program managers make a challenging decision simply because they believe it is the right thing to do, they risk being labeled failures or going down in history as bumbling idiots.

Today's program managers rarely encounter such risk, many of them using the bureaucratic process to build up walls that protect their careers. Today's manager can avoid risk by having decisions made by committees or by dividing programs into enough parts that it's not clear who is responsible for what. Another strategy that some program managers use to avoid risk is to be involved only with low-risk portions of a program, handing off high-risk portions to other managers who, if the program fails, can always defend themselves from blame by saying they were ordered to do the job. If the program succeeds, then the original program manager can step back into the picture and take credit for the successful venture by claiming it was his or her idea all along.

Paul Bikle would not have done well in today's managerial environment. He lacked the political imperative needed to work the system in his favor. He was so open and honest that everyone knew exactly what he was thinking-except when he was [49] playing cards with the crew during lunch. That he was so open and "readable" was a trait that worked well for those working under him, for they knew where he stood. But it wasn't a trait that helped him in dealing with the hierarchy that developed gradually over him at NASA Headquarters.

Long after the lifting-body program was over, when Milt Thompson had retired as a research pilot and entered management at the Flight Research Center as its Chief Engineer, we talked about the episode with the Chief of Research Engineering back in 1963 and how people in different positions can view the same situation very differently, depending on their positions. As a research pilot, Milt Thompson had the reputation of being a wild and crazy guy who would take every calculated risk that his bosses would allow. But when he became a manager, he became very conservative, not allowing other pilots to take the same kinds of risks that he had taken as a pilot. In this sense, a manager is rather like the father who won't let his son ride motorcycles even though he had done so when he was a young man. As a manager, Milt Thompson said he could fully appreciate the position taken by the Chief of Research Engineering in vetoing the M2-F1 flight tests. He conjectured that if he had been in the Chief's position, he might also have questioned the rationale for the M2-F1 flights.


Gooney Bird Meets Flying Bathtub: First Air-Tow, 16 August 1963


After the ejection seat had been installed in the "Flying Bathtub," Milt Thompson made a few more tests on car-tow, adjusting to the heavier weight and checking out the flight instrumentation system. We did as thorough a flight readiness review as we could before moving into air-towing the lifting body, wanting to make sure there wasn't something we were overlooking.

One day while we were still getting ready to begin air-tows, Milt said to me privately, "Dale, I have complete confidence in you to make the right decisions. I'm putting my life in your hands." That was the best and most sincere compliment I have ever received during my career.

By now, George Nichols and Glynn Smith, instrumentation technicians who had joined the lifting-body group of volunteers, had installed the instrumentation needed to radio data to the ground. Since the M2-F1 was an extremely simple glider with no onboard electronic systems, data from only 15 sensors would be sent to the ground. (By contrast, data from 400 to 500 sensors was transmitted by radio during a typical X-15 mission.) In the M2-F1, the sensors would transmit air data, including airspeed, altitude, angle of attack, and angle of sideslip; vertical, side, and longitudinal accelerations; gyro data, including roll, pitch, and yaw rates; and control position data from the single elevator, two rudders, and two elevons.

Stability and control flight data would be transmitted by radio back to the antennae on the roof of the main NASA building that housed the control room, 10 miles from the lakebed take-off site. Here, Ken Iliff, Bertha Ryan, and Harriet Smith would [50] watch plotting recorders equipped with ink pens generating traces of the data received from the measuring sensors aboard the M2-F1. The data would also be recorded on tape for analysis after the flight. Also in the control room during the flight would be the mission controller, research pilot Bill Dana, who, exactly two years later, would pilot the M2-F1 for the first time and then spend a total of ten years as a lifting-body pilot. But for the first air-tow flight of the M2-F1 on 16 August 1963, he would be on the ground, serving as that all-important link between the pilot in the cockpit and the engineers in the control room.

Developed for the X-15 program, the control room at the NASA Flight Research Center also contained two large plotting boards that drew the track of the aircraft on maps of the surrounding terrain, based on data received by the radar-tracking dish antenna atop the building. The control rooms later built at the NASA Johnson Space Center in Houston, Texas, for the first human space programs (Mercury, Gemini, and Apollo) were patterned after this control room at the NASA Flight Research Center.

For the first air-tow of the M2-F1 behind the Gooney Bird, we set up for take-off at the extreme south end of Runway 17, the longest lakebed runway on Rogers Dry Lake at Edwards AFB. We really didn't know how well the M2-F1 could make turns behind the Gooney Bird. An additional advantage of using the longest runway was that, if the tow-line broke or released, Milt could glide straight ahead, making a landing on the lakebed, Runway 17 using only half the length of the 15-mile-long lakebed. Piloting the Gooney Bird would be NASA X-15 pilot Jack McKay.

The plan was that when the Gooney Bird reached the north end of Rogers Dry Lake, McKay would make a large circle counterclockwise over the lakebed while rising to an altitude of 12,000 feet. Once there, the M2-F1 would be released off the tow-line. Vic Horton would observe the M2-F1 flight from the small Plexiglas dome atop the Gooney Bird, watching the M2-F1 in tow behind the Gooney Bird and keeping McKay advised on what was happening with it. I would be monitoring the flight from a radio van at the take-off site.

At seven o'clock on the morning of 16 August 1963, the winds were dead calm on the ground and only about five knots at 12,000 feet. A ladder was needed for boarding the M2-F1. Milt was assisted by the crew chief, Orion B. Billeter, since considerably care was needed to avoid stepping on the thin wooden skin of the vehicle's upper body deck. Once Milt was strapped into the ejection seat, his helmet radio was checked out. Then, the canopy was lowered and secured in place, and the ladder was pulled away. After the tow-line was hooked to the M2-F1, Billeter pulled on it while Milt checked the release hook. The procedure was repeated with the tow-line and release on the Gooney Bird.

NASA pilots Don Mallick (who would fly the M2-F1 four months later) and Jack McKay started and checked out the Gooney Bird's engines. Before take-off, McKay tried to avoid blasting Milt with too much dust from the lakebed. Ready to go, Milt gave a thumbs-up. After checking with the Edwards AFB control tower, the base's ambulance and fire truck, and McKay in the Gooney Bird, mission controller Bill Dana gave the go ahead for take-off.



M2-F1 in tow behind R4D <<Gooney Bird>>, with the nose positioned high so the tow plane is visible through the nose window.

M2-F1 in tow behind R4D "Gooney Bird", with the nose positioned high so the tow plane is visible through the nose window. (NASA photo E63 10962)


Gently easing the throttles forward on the Gooney Bird, McKay began to roll slowly down the lakebed. The Gooney Bird accelerated until its tail lifted off the ground. Very gently Milt lifted the M2-F1 off the ground exactly as he had done during the car-tows, slowly climbing on the end of the 1,000-foot tow-line until the M2-F1 was about 20 feet higher than the Gooney Bird and he could see the tow-plane through the nose window between his feet. He had to be fairly precise in maintaining position to keep the tow-plane in sight through the small nose window. The Gooney Bird gently lifted off the ground, Milt flying the M2-F1 in perfect formation behind and above the tow-plane.

After a few minutes of climbing, Milt radioed that the M2-F1 was very solid and that it was easy to hold high-tow position behind the Gooney Bird. Because we hadn't installed a pilot-adjustable pitch trim system, however, he had to hold back pressure on the stick. We had omitted doing that, just to keep it simple. The trim tabs we'd installed on the body flap during the wind-tunnel tests would trim out most of the stick forces in free flight but not on tow.

McKay held to a speed of 100 miles per hour as the Gooney Bird climbed to 12,000...



M2-F1 being air towed. Notice the side windows above the nose gear for increased visibility near touchdown.

M2-F1 being air towed. Notice the side windows above the nose gear for increased visibility near touchdown. (NASA photo EC63 229)


....feet. Over the radio, Milt said that he was beginning to relax and enjoy the flight. Nevertheless, he still had to give constant attention to keeping the Gooney Bird in sight through the nose window of the M2-F1. The Gooney Bird made three large circles over the northern lakebed during the twenty minutes taken to climb to 12,000 feet. By this point, NASA pilot Fred Haise was flying alongside Milt in a T-37 jet trainer as a chase-observer.

The plan was for Milt to release the M2-F1 from the tow-line at this elevation while heading south over the northern portion of the lakebed. He was to make a 180-degree turn to the left, make a practice landing flare at about 9,000 feet altitude, and then push over and continue another 180-degrees to the left in order to line up on Runway 18, heading south. The average rate of descent was about 3,600 feet per minute, giving Milt about six minutes to learn to fly the M2-F1 before having to make the crucial one-shot landing maneuver.

Unlike the normal landing of an airplane, landing the M2-F1 was more like pulling out of a dive. A pushover maneuver had to be done at about 1,000 feet to build airspeed up to about 150 miles per hour, followed by a flare at about 200 feet altitude from a 20-degree dive. The flare maneuver would take about 10 seconds, leaving three to five seconds for the pilot to adjust to make the final touchdown. Milt had the option of hitting a switch to fire a rocket motor, giving him five to six more seconds to adjust sink rate before touchdown.

Watching from the ground, it seemed that the M2-F1 literally fell out of the sky. Since the vehicle had come level while Milt was making his practice landing at altitude, he radioed that he was going for the real one. Bill Dana, whose call sign was "NASA 1," confirmed that the practice landing had also looked good on the charts in the control room. Having made strip chart overlays earlier while Milt was practicing [53] landings on the simulator, Ken Iliff, Bertha Ryan, and Harriett Smith had been able to do real-time comparisons while Milt was doing his practice landing maneuver.

However, if Milt hadn't been able to achieve level flight during the practice landing, our ground rules were that he was to eject, letting the M2-F1 crash. We considered the M2-F1 cheap enough to be expendable. Such a ground rule wouldn't sell in today's flight-testing of expensive airplanes, former NASA pilot and astronaut Fred Haise recently told me.

Our ground vehicles were parked well to the side of Runway 18, opposite Milt's planned landing point. It was scary watching him dive for the ground, and I held my breath. Milt leveled out, making a picture-perfect landing at the planned touchdown spot without using the rocket. I finally remembered to breathe as he rolled straight ahead and turned off the runway, coasting to a stop. All of us, including Paul Bikle, surrounded the M2-F1 while Orion Billeter helped Milt out of the lifting body. We were one bunch of happy people as we stood there, shaking Milt's hand. Later, the debriefing room was wall-to-wall smiles as Milt described a flight that went exactly as planned.

We had a party that night at my house, but it bore no resemblance to the typical wild X-15 parties of heavy drinking that Milt Thompson described in his book, On the Edge of Space6. Since the X-15 program involved most of the personnel of the Flight Research Center in some way, X-15 parties were always held at Juanita's, then the biggest bar in Rosamond, just outside the western boundary of Edwards AFB. Almost exclusively stag, the X-15 parties were mostly attended by NASA's ex-military pilots, aircraft crews, and flight planners. Research engineers seldom were seen at X-15 parties. As Milt relates in On the Edge of Space, most of the X-15 parties continued at Juanita's for four or five hours, then moved to one or more of the bars in Lancaster.

Unlike the X-15 program, the lifting-body program had research engineers steering its path from the very beginning. After success with the M2-F1, additional lifting-body vehicles would continue to be designed and built throughout the twelve years of the lifting-body program, involving the cooperation and teamwork of research and design engineers at three NASA centers (including Ames and Langley) as well as the research engineers at contractors Northrop and Martin.

The lifting-body program was also the first program at the NASA Flight Research Center significantly influenced by women engineers. Bertha Ryan and Harriet Smith not only played major roles in the development of the M2-F1 but continued to do so with other lifting-body vehicles, by which time other women at the NASA Flight Research Center were also involved in the program. After-wards, Harriet Smith moved on to project management at the NASA Flight Research Center, while Bertha Ryan opted to remain in research engineering, later designing missiles for the Navy at the China Lake Naval Weapons Center, about 50 miles north of Edwards AFB. Since the days of the lifting-body program that ended in 1975, women have increasingly entered the world of aerospace technology, so that now it is common to see women in engineering, as part of flight crews, and as pilots and astronauts.

[54] The successful flight of the M2-F1 was a special triumph for us, a little team of "amateurs" pulling off a big one. Despite having Paul Bikle's full backing, many of the "professionals" on the X-15 program had continued to consider the M2-F1 a high-risk project due to our lack of experience. Of course, it's a little hard to have much experience when doing something that has never been done before. We matured at once after that first flight, rapidly moving up in credibility and status.

A few weeks after the successful flight of the M2-F1, on 3 September 1963, aviation news reporters first viewed the craft at the NASA Flight Research Center. The M2-F1 quickly became a hot item in aviation periodicals.

While a few people at NASA Headquarters were aware of the lifting-body project by about a week after the historic first flight of the M2-F1 in mid-August, they didn't pay much attention to it, mainly because we hadn't requested any money for the program. However, the NASA administrator in Washington, D.C., James E. Webb, remained unaware of the successful first flight of a lifting body until, while testifying before a congressional committee, he was asked about it by a congressman who, having read about it in the press, wanted to know if NASA was starting a new multi-billion-dollar space program that Congress neither knew about nor had approved. Bikle's phone began ringing immediately after this incident, which obviously had been embarrassing for the administrator. When Webb found out that we had spent only $30,000 on the program and that there was no billion-dollar plan in the making, things cooled down and we were allowed to continue with our M2-F1 flight tests.


December 1963: Peterson, Yeager, and Mallick Fly the M2-F1


After Milt's first flight, the M2-F1 became very operational. As a simple glider, it had no systems to maintain, except the research instrumentation system. A part-time crew chief could easily keep the M2-F1 on flight status. The Gooney Bird was available most of the time to us as a tow-plane because it was being flown almost every day on support missions for other programs and had a full-time crew chief.

Milt Thompson flew the M2-F1 on its first sixteen flights in 1963-five in August, two in September, six in October, and three in November. These flights were made specifically to define the craft's aerodynamics and stability and control characteristics. Flight research is most valuable when the data is used, as it was in these first flights, in comparison with wind-tunnel test results in correcting or completing aspects of design and prediction based on those results.

After these flights, Paul Bikle and Milt Thompson decided it was time to start checking out other pilots in the M2-F1, beginning with Bruce Peterson and Colonel Chuck Yeager. A NASA test pilot and a former Marine Corps pilot, Bruce Peterson had served along with Milt Thompson in 1962 as one of two project pilots on the paraglider research vehicle, or Paresev, program that was designed to evaluate the use of an inflatable flexible wing in the space program as a way by which astronauts could leave a spacecraft and return to Earth in a vehicle capable of making an airplane-like landing. The similarity with the M2-F1 is that both vehicles were gliders towed into....



M2-F1 pilots (Chuck Yeager in cockpit, Bruce Peterson to his left, and Don Mallick) being checked out by Milt Thompson (on stool).

M2-F1 pilots (Chuck Yeager in cockpit, Bruce Peterson to his left, and Don Mallick) being checked out by Milt Thompson (on stool). (NASA photo E63 10628)


....flight by winged aircraft, and both programs were excellent examples of Paul Bikle's low-cost and do-it-quick approach. Paul Bikle wanted his old friend, Chuck Yeager, then head of the USAF Test Pilots School at Edwards AFB, to fly the M2-F1 and give his assessment of the vehicle before other Air Force pilots were allowed to fly it. 7

During the last week in November, Peterson and Yeager were initially checked out with the M2-F1 on extensive car-tows up to an altitude of 20 feet. Thompson scheduled both for flights in air-tow by the Gooney Bird on 3 December, using a five-mile-long lakebed runway so that there would be nothing critical about where touchdown occurred on the runway so long as a good flare was made to keep from breaking the M2-F1 in hard landing. With Bill Dana and Don Mallick piloting the tow-plane, Peterson and the M2-F1 were towed aloft to 12,000 feet in the first flight of the day. Peterson released the tow-line, making a very good landing on the lakebed. However, the M2-F1 had landed some distance from the van containing Milt Thompson and Chuck Yeager, which was sitting beside the runway.

[56] Next, it was Yeager's turn to have his first lifting-body flight. Naturally competitive, Yeager suggested going for a spot landing on the runway just opposite the van parked beside the runway. Dana and Mallick towed Yeager aloft, as they had Peterson. Yeager opened up the flight envelope on the M2-F1, flying both faster and slower in his practice landing maneuver at altitude than had Milt. Then, he dove the M2-F1 at the lakebed in a steeper angle than Milt had used, leveled out, and made a greased-on landing in front of the van. Climbing out of the M2-F1, Yeager exclaimed, "She handles great!" 8

It was a beautiful, but cold, December morning. The winds were still calm, and the Gooney Bird had been climbing very well in the cold weather. Milt suggested that Peterson and Yeager each get two more flights in for the day. Responding to Yeager's challenge, Peterson set up in his second flight to touch down just in front of the van.

What Peterson and the rest of us didn't realize was that we engineers had made a little mistake. Since Milt had started flying the M2-F1 in August and the weather had been quite warm whenever he flew the vehicle that fall, we had serviced the shock struts in the main landing gear with a standard viscosity oil. That was fine for Milt's earlier flights. However, on this early December morning, after two flights to altitude in temperatures below freezing, the oil had hardened to the consistency of molasses.

When Peterson landed the M2-F1, the landing gear was rigid, the struts immobized by the thickened oil. At touchdown, the main wheels separated from the vehicle and bounced across the lakebed, as shown in the film of the landing made by the forward-looking camera mounted behind the pilot's head. The four bolts connecting the wooden shell to the inner steel tubing also tore out, dropping the wooden shell about six inches until it settled around Peterson in the cockpit.

Not injured, Peterson was the brunt of jokes about this landing for years afterwards. Structural repairs were easily made to the M2-F1. The original Cessna 150 landing gear was replaced with the more rugged gear of a Cessna 180. Different struts were added with multi-viscosity oil. Before continuing flights nearly two months later in late January 1964, we expanded the research data system to measure more parameters for extraction of aerodynamic derivatives.

The first flights of the new year were made on the morning of 29 January, with Bruce Peterson, Milt Thompson, and Chuck Yeager each making one flight. Yeager said he was having a ball flying the vehicle. The next morning, NASA pilot Don Mallick checked out in his first and only lifting-body flight after Yeager made his third and last flight in the M2-F1. 9

During the briefing session before the day's flights, I had denied Yeager's request to be allowed to roll the M2-F1. He believed that he could make a perfect barrel roll in the little lifting body. I explained that Dick Eldredge and I had designed the M2-F1 to weigh 800 pounds and fly at a slower speed, not knowing the vehicle would [57] have to grow in weight to 1,250 pounds by adding an ejection seat, heavier instrumentation, and a landing rocket. I also explained that we weren't that confident in analyzing loads in a roll maneuver, for not only were there bending moments from side loads in sideslips, but loads also were transmitted to the vertical tails from the asymmetrical "elephant ears" attached to them. In short, we couldn't be sure the tail would remain intact during a roll, given the vehicle's heavier weight.

Yeager didn't try to roll the M2-F1 on his last flight that morning. As experience later showed, however, Yeager likely could have barrel-rolled the vehicle successfully that morning, for over a year later the M2-F1 was rolled unintentionally in two flights and the tail remained intact. Although Yeager never flew a lifting body after his third flight in the M2-F1, he remained very enthusiastic about the concept, exerting a good deal of influence in encouraging the Air Force to develop the rocket-powered lifting bodies, the X-24A and X-24B, and the jet-powered X-24J.


Serious Research Flying, 1964-1965


After January 1964, we settled down into a year of serious research flying. Milt Thompson and Bruce Peterson often alternated as pilot, the M2-F1 flown about twice a month, as quickly as the research analysis team could digest data from one flight and plan the next. We made a total of twenty-five flights, ten of them by Peterson.

Working together, Ken Iliff, Bertha Ryan, and Harriet Smith had put together a planned program for extracting data from three basic types of flight maneuvers-the steady state, quasi-steady state, and dynamic. In a typical steady-state maneuver, for example, the M2-F1 would be flown straight ahead and stabilized at different airspeeds in the glide, resulting in data for Jon Pyle and Ed Saltzman on lift, drag, and elevator trim. In a typical quasi-steady-state maneuver, the pilot would put the M2-F1 into a gliding wind-up turn and gradually tighten the turn, increasing the "G" load (gravitational pull) by increasing back stick pressure, allowing lift, drag, and trim data to be measured at higher airspeeds and with structural deflections, if any.

In a typical dynamic maneuver, the pilot would stabilize the M2-F1 in a steady glide and then pulse one control at a time, with the pulse usually in a doublet. For example, if the goal was to get data on aileron characteristics, the stick would be moved to the right and held, moved to the left and held, then returned to neutral and held fixed by the pilot. Then, the vehicle would be allowed to oscillate with controls frozen by the pilot. This maneuver would be repeated for several airspeeds or angles of attack, researchers extracting aileron characteristics from the doublet portion of the maneuver and airframe characteristics from the final portion of the maneuver involving oscillation with controls frozen. This maneuver was also done for defining yaw control by rudder and pitch control by stick fore and aft.

For the aerodynamic characteristics of the M2-F1 to be defined completely, Thompson and Peterson had to perform almost 100 maneuvers. With only about six [58] minutes available as the M2-F1 glided down from 12,000 feet, the pilots used flight cards to squeeze in as many maneuvers as possible before having to set up for landing. Each flight averaged four maneuvers during those six minutes.

Aerodynamicists define the characteristics of a given airplane shape by the use of aerodynamic derivatives coming from three types of air forces: those caused by wind flow direction, angle of attack, and angle of sideslip; control deflections; and rotary motions. While there was plenty of wind-tunnel data on the M2-F1 to compare with flight data on the first two types of air forces, there was no wind-tunnel data for the third, those air forces caused by rotary motions of the vehicle. The first two types could be evaluated easily in the wind tunnel with the model held stationery on strings or pedestals. However, the third type can be evaluated only by using elaborate mechanisms to rotate the model rapidly in all axes (roll, yaw, and pitch). No attempt was made at NASA Ames to obtain this type of dynamic or damping data during the wind-tunnel testing of the M2-F1, not only because of the huge expense involved in developing the mechanisms, but especially because of the lack of confidence in this type of wind-tunnel data, the elaborate mechanisms interfering with the airflow around the model.

We "guesstimated" the rotary data that we put into the simulator along with the other data resulting from wind-tunnel measurements. Often, these "guesstimates" turned out to be off by a factor of three or four since, at the time, we didn't have good techniques for estimating aerodynamic rotary damping derivatives. Ken Iliff and Larry Taylor put their heads together, trying to come up with a solution.

They decided to convert Taylor's garage at his home in Lancaster into a wind tunnel for measuring rotary derivatives, using the original small-scale model of the M2-F1 that I had built. Taylor built a long box with a five-horsepower electric fan in one end, plus straigtening vanes and a special test section in the middle. They sealed the garage door so the entire garage could be used to return the air to be recirculated through the box inlet, thus making it a more efficient closed-loop tunnel. Taylor also designed and rigged a balance system composed of strings, pulleys, and a very sensitive string tension measuring device so the M2-F1 model could be rolled, yawed, or pitched at different rates. Of course, lightweight household objects hanging in the garage had to be anchored to keep them from blowing around in the garage. These at-home wind-tunnel tests provided the data for the simulator estimates and for comparison with actual flight data.

Iliff and Taylor also applied a trial-and-error technique, originated by Dick Day on the X-2 project, that used the analog flight simulator for extracting derivatives in flight. They changed settings on the simulation one at a time until they got time histories of dynamic maneuvers from the simulator to match up with those recorded from flight. Although this was a long and tedious process with limited accuracy, it was the only way we knew at the time for doing this task with analog systems. Harriet Smith was primarily responsible for extracting derivatives from the M2-F1 flight data, using this technique with the analog simulator. In 1965, Smith published a report entitled "Evaluation of the Lateral-Directional Stability and Control Characteristics Of the [59] Lightweight M2-F1 Lifting Body at Low Speeds," showing the flight results with wind-tunnel comparisons. 10

Iliff and Taylor also had new tools coming into use by which to sharpen their trade, for the digital computer revolution was in full swing by this time. Within a few years, they developed a new computer technique called "the maximum likelihood estimator," by which dynamic-maneuver flight data could be input into a digital computer to produce aerodynamic derivatives-a technique producing very accurate results so long as the flight data used is high in quality and accuracy. In fact, "the maximum likelihood estimator" that Iliff and Taylor originated during the lifting-body era at the NASA Flight Research Center is currently being used by flight-test organizations in the United States and in various countries around the world. 11


Aerobatics in the Flying Bathtub


Over the next two years, 1965 and 1966, the M2-F1 was used primarily to checkout and familiarize more pilots with the lifting body, including NASA pilots Bill Dana and Fred Haise and Air Force pilots Joe Engle, Jerry Gentry, and Don Sorlie. By this time, flying the M2-F1 was also a kind of preparatory task undertaken by pilots who hoped later to fly the M2-F1's heavyweight successor, the M2-F2. The M2-F1 made 53 air-tow flights during 1965 and 1966, and by the time the first lifting body was retired from flight in August 1966, it had been flown by ten pilots about 400 times by car-tow and approximately 100 times by air-tow. Fred Haise and Joe Engle flew the M2-F1 only on car-tows to 25 and 30 feet in altitude on 22 April 1966, their experience with the lifting body cut short due to their being selected as astronauts for NASA space missions.

Milt Thompson and Vic Horton developed a formal lifting-body pilot checkout procedure that required each pilot to make 24 car-tows before his first air-tow flight. The first three car-tows involved nose-gear steering with tow-line releases at up to 45 [60] miles per hour. The next six car-tows involved nose-wheel rotations up to 60 miles per hour. The final fifteen car-tows involved doing lift-offs at up to 95 miles per hour to familiarize the pilot with roll control with elevons and yaw control with rudders. Although the number of car-tows required seemed excessive to the pilots, Milt Thompson felt the requirement was necessary to minimize the risk of injury to a pilot or damage to the vehicle during car- and air-tows.

Before moving on to air-tows, the pilots were also familiarized with the flare portion of lifting-body flight by means of a three-degrees-of-freedom simulator and a shadow-graph presentation. This pre-flight procedure included familiarizing the pilots with the capabilities of the landing-assist rocket.

On 16 July 1965, it was Captain Jerry Gentry's turn to get checked out in the M2-F1. An Air Force test and fighter pilot who later made the first flight of the Air Force's X-24A and then flew missions in Vietnam, Gentry found flying the M2-F1 on air-tow to be challenging.

The lifting body was hooked by tow-line onto the Gooney Bird, and the takeoff began. Gentry lifted the M2-F1 into formation above and behind the Gooney Bird on the end of the 1,000-foot tow-line. Then, the Gooney Bird, piloted by Stan Butchart, lifted off. At about 200-foot altitude, while Gentry was climbing, something began to go wrong. Gentry began making small roll inputs to correct the right and left positions of the lifting body relative to the Gooney Bird, his corrections growing larger and larger. All at once, we had another pilot-induced oscillation in the making.

As the amplitude of the oscillation increased, so did the urgency of radio contacts with Gentry:

"Level your wing..."

"Level your wings!"





As the Gooney Bird slowly climbed to 300 feet above the lakebed, Vic Horton was watching the M2-F1 through the tow-plane's observation dome, the rocking motion of the M2-F1 growing larger and larger. He watched in horror as the M2-F1 rolled belly-up and disappeared from sight below the tail of the Gooney Bird. Both Gentry and the safety monitor aboard the Gooney Bird released the tow-line, realizing the situation was completely out of control. Vic Horton was convinced that he'd next see pieces of the M2-F1 scattered across the lakebed, which, had it happened, could have been the end of the lifting-body program.

When it was released from the tow-line, the M2-F1 was inverted with its nose high and traveling at approximately 100 knots airspeed, or about 115 miles per hour. The probability of recovery from that condition was virtually zero. During a normal landing, with the vehicle straight and level, the flare would be initiated at that 300-foot altitude at a stabilized speed of 120 knots, or 138 miles per hour. Theoretically, at least, it was impossible to get the nose down in time to pick up the speed needed to....



M2-F1 dummy ejection seat test setup at South Edwards.

M2-F1 dummy ejection seat test setup at South Edwards. (Air Force photo JN-043-1, available as NASA photo EC97 44183-4)


....accomplish flare. Fortunately, Gentry ignored theory and, after release from the tow-line, completed the barrel roll, touching down on the lakebed at the bottom of the roll...all in nine seconds. It was a hard roll that broke the landing gear but it produced no other damage or injuries, except to Gentry's pride.

Gentry was so upset that he insisted on trying another flight immediately. Other members of the operation, including the instructor pilot, were in such a state of shock at the time that they agreed to try again, even though the M2-F1 was obviously listing heavily to one side due to its broken landing gear. Luckily, cooler heads had observed the entire incident from the office of the Director of Flight Operations. A stern call came over the radio to "knock it off and get back in here."

During the next thirteen months, while Gentry practice more car-tows, the repaired M2-F1 was flown six times by Milt Thompson and Bruce Peterson. On 17 August 1966, Gentry got his second chance at a checkout flight on the M2-F1. None of us expected history to repeat itself, but it did. We watched in shock as the same sequence of events rapidly developed, a low-amplitude lateral oscillation beginning immediately after liftoff, rapidly building to greater than plus or minus 180 degrees. Once again the tow-line was released with the M2-F1 upside down at 300 feet above the lakebed. Gentry must have found something familiar about the episode, for this time he released the tow, completed the barrel roll, came wings level, ignited the landing rocket, and made a perfect landing.

[62] The second time around there was no damage to the vehicle, but Bikle apparently had had enough. "That's it!" he said. Bikle saw towing as a special problem with the M2-F1, believing that in future we should look into launching lifting bodies from bombers. Bikle stuck by his decision, grounding the M2-F1 permanently. With that, the first lifting-body vehicle was retired from flight.

Gentry later was able to prove to Bikle, Thompson, and Lieutenant Colonel Don Sorlie, the official boss of the Air Force's lifting-body pilots, that his problems in the M2-F1 were caused simply by a lack of visibility. Being much shorter than the other pilots affected his eye position in the cockpit of the M2-F1 considerably, so much so that after the lifting body and the Gooney Bird left the ground on tow, he could see neither the Gooney Bird nor the horizon through the nose window, making it humanly impossible to control the vehicle's attitude

Recalling the event years later, Gentry said with a laugh, "Oh, hell, I was upside down twice on tow. As soon as I could figure out which way the roll was going, I put stick in with the roll and went on around. When I got momentarily to wings-level, I punched off. Barely had time to release the tow, flare, and whump. The second time it happened, I said, 'Well, I've been here before.' I'd gotten good enough at it that I even glided for a few seconds." 12

Whether Gentry would be allowed to continue flying lifting bodies in future phases of the program rested entirely on the ruling of Bikle and Thompson after conferring with Sorlie. They decided to allow Gentry to continue with the rocket-powered lifting bodies. In 1992, in his acceptance speech at a Test Pilots' Walk of Honor awards ceremony in Lancaster, Gentry expressed appreciation for Bikle and Thompson's decision. While he was flying the lifting bodies, Gentry was the project pilot on the F-4E and later did flight tests on other aircraft including the F-4C/D, F-104, F-111, and F-5.


Significance of the M2-F1 Program


The M2-F1 program proved to be the key unlocking the door to further lifting-body programs, including the current Shuttle spacecraft and several other vehicles currently in-progress, such as the X-33. Flight tests of the M2-F1 supplied the boost in technical and political confidence needed to develop low lift-to-drag-ratio, unpowered, horizontal-landing spacecraft.

Technical reports written by the engineers who were part of the M2-F1 program also were important, establishing the lifting-body as a concept. For example, "Flight-Determined Low-Speed Lift and Drag Characteristics of the Lightweight M2-F1 Lifting Body" by Victor W. Horton, Richard C. Eldredge, and Richard E. Klein compared wind-tunnel and flight data to establish the fact that a lifting body with a maximum lift-to-drag ratio of 2.8 measured in-flight could be landed successfully and [63] repeatedly by an unassisted pilot.13 Furthermore, the findings of the M2-F1 stability-and-control engineering team-Ken Iliff, Bertha Ryan, Harriet Smith, and Larry Taylor-demonstrated that a radically-shaped flying machine such as the M2-F1 did not need automatic control augmentation to have acceptable and even good handling qualities, a conclusion confirmed in Harriet J. Smith's "Evaluation of the Lateral-Directional Stability and Control Characteristics of the Lightweight M2-F1 Lifting Body at Low Speeds." 14

In the 1960s, the lifting-body concept was so tentative in the minds of space planners that the M2-F1 program seemed destined to have pronounced effect on the direction taken afterwards in space vehicles, the potential for development of horizontal-landing spacecraft fairly much dependent upon our success. Any one of three different effects could have followed from the three major outcomes possible for the M2-F1 program:

First, the M2-F1 program could have halted after the car-tows at very low altitudes, as would have happened had Paul Bikle agreed with the then Chief of Research Engineering at the NASA Flight Research Center. Had this happened, the expressed lack of confidence in the flight concept could have prevented the later acceptance of any proposed follow-on lifting-body programs, which, in turn, could have slowed or prevented the later development of a horizontal-landing spacecraft such as the current Shuttle.

Second, if we had had a serious accident with the M2-F1 in which a pilot was injured seriously or killed, it isn't likely that any additional lifting-body flight-test programs would have taken place, making even less likely the later development of today's Shuttle and other horizontal-landing spacecraft.

Third, the M2-F1 program could be an adventure in success and open the door for future lifting-body programs. Fortunately, this is exactly what happened. And the door remains open for generations yet to come of the progeny of the original lifting body, the lightweight M2-F1.



1 Victor W. Horton , Richard C. Eldredge, and Richard E. Klein, Flight-Determined Low-Speed Lift and Drag Characteristics of the Lightweight M2-F1 Lifting Body (Washington, D.C.: NASA TN D3021, 1965).

2 Wilkinson, "Legacy of the Lifting Body," p. 54.

3 On the Kármán vortex, see Michael H. Gorn, The Universal Man: Theodore von Kármán's Life in Aeronautics (Washington, D.C.: Smithsonian Institution Press, 1992), pp. 23-24.

4 For Toll's position, Hallion, On the Frontier, p. 151.

5 Tom Wolfe, The Right Stuff (New York: Ferrar, Strauss, Giroux, 1979).

6 Thompson, At the Edge of Space, pp. 71-73.

7 For further information on the Paresev program, see Hallion, On the Frontier, pp. 137-140; Lane E. Wallace, Flights of Discovery: 50 Years at the NASA Dryden Flight Research Center (Washington, D.C.: NASA SP-4309, 1996), pp. 131-133.

8 Quoted in Hallion, On the Frontier, p. 152.

9 The three flights include only the air tows, not those in the M2-F1 towed by the Pontiac.

10 Harriett J. Smith, Evaluation of the Lateral-Directional Stability and Control Characteristics of the Lightweight M2-F1 Lifting Body at Low Speeds (Washington, D.C.: NASA Technical Note D-3022, 1965).

11 Another name for "maximum likelihood estimator" is parameter estimation, which can also be described as a series of mathematical procedures developed by Dryden researchers to extrace previously unobtainable aerodynamic values from actual aircraft responses in flight. This contribution allowed flight researchers for the first time to compare certain flight results with predictions. A discussion of this technique appears in Lawrence W. Taylor and Kenneth W. Iliff, "A Modified Newton-Raphson Method for Determining Stability Derivatives from Flight Data," paper presented at the Second International Conference on Computing Methods in Optimization Problems, San Remo, Italy, Sept. 9-13, 1968. On this matter, see also Kenneth W. Iliff, "Parameter Estimation for Flight Vehicles, " Journal of Guidance, Control, and Dymanics, vol.12 (Sept.-Oct. 1989): 609-22.

12 Wilkinson, "Legacy of the Lifting Body," pp. 54-55.

13 Victor W. Horton , Richard C. Eldredge, and Richard E. Klein, Flight-Determined Low-Speed Lift and Drag Characteristics of the Lightweight M2-F1 Lifting Body (Washington, D.C.: NASA TN D3021, 1965).

14 Harriett J. Smith, Evaluation of the Lateral-Directional Stability and Control Characteristics of the Lightweight M2-F1 Lifting Body at Low Speeds (Washington, D.C.: NASA Technical Note D-3022, 1965).