Category Space Ship One

Clear of White Knight, the pilot armed the rocket engine, flicked the ignition switch, put his head back against the seat, and grabbed the control stick with both hands.

“When you light that rocket motor off, everything literally starts with a bang. There is so much energy associated with that rocket motor. It is like a tsunami sweeps through the cabin and literally takes you away,” said Brian Binnie, the pilot who flew the first and last powered flights of SpaceShipOne.

“You really have nothing in your background or DNA to tell you that what is happening to you is good. You have no basis. Three or four seconds will go by, and you go, ‘Ah, I’m not dead. Therefore, it must be going as they told me it was going to go.’”

The roar from the rocket engine was extremely loud. “The noise is certainly worse right at ignition when you have little forward speed,” explained Binnie. “But as soon as you are supersonic, you are going faster then any sound that the rocket motor makes. It doesn’t really penetrate the cabin a lot. What you hear in the cabin is all the gurgling off the main oxidizer tank that’s right on the other side of the bulkhead from which you’re located. So, you hear that. There is a certain amount of wind noise over the vehicle. A good helmet with reasonable ear protection let the radio come across just fine.”

The force pinning the pilot to his seat just added to the flood of sensations. “The acceleration is fierce. It’s abrupt. It’s sudden. It’s a big slap in the back and whoosh off you go. It is a very dynamic environment, and you are very much holding on for dear life,” Binnie said.

“As it develops, your body readily adjusts to the g’s that you are experi­encing. They are not that high during boost. They are between 3 or 4.” Having been a former navy fighter pilot, Binnie had some experience with some pretty fast starts. The initial kick from a catapult off the deck of an aircraft carrier had some similarity. After 2—2.5 seconds, the acceleration from the catapult was over, but after the same amount of time, SpaceShipOne would still be going and going.

“A catapult shot takes you from 0 to about 150 miles per hour [240 kilometers per hour] in 2 to 2.5 seconds. If you continue that accel­eration rate, which is kind of what the spaceship is doing, you would then go from 150 to 300 miles per hour [480 kilometers per hour] in another 2.5 seconds or the 5-second mark. And at the 8-second mark, you’d be doing not 300 miles per hour but 600 miles per hour [970 kilometers per hour]. And by the 10-second mark, you’d be supersonic.”

The pilot held the control stick with both hands because, as SpaceShipOne moved faster and faster, the forces from the outside air pushed harder and harder against the vehicle and its controls. The pilot had to make sure the nose was coming up right away. Otherwise there was a danger of overspeeding SpaceShipOne and breaking it apart. The “never-exceed” speed was around 260 knots equivalent airspeed (KEAS). A knot is a nautical mile per hour, which is a little faster than a mile per hour. Equivalent airspeed is a measure of how fast a vehicle feels it’s going in terms of the air pres­sure pushing against it. So, this value may seem very low, but SpaceShipOne started out already operating above 85 percent of the atmosphere. The air density was very low to begin with and didn’t exert as much air pressure as if the vehicle were flying at a lower altitude where the air density was higher.

Figure 3.11 shows SpaceShipOne during the initial pull up, also called “turning the corner” or the “gamma turn.” With the feather locked down tight, it was critical for the pilot to keep the wings level during this phase.

“Because our wings are level, that turn results in pointing nose up,” Pete Siebold said. “So, if any portion of the time you roll to a

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Fig. 3.11. Once the rocket engine ignited, the test pilot immediately had to begin to pull the nose of SpaceShipOne up in a maneuver called "turning the corner." By the time the turn upward was complete, SpaceShipOne was already traveling at supersonic speeds. Mojave Aerospace Ventures LLC, video capture provided courtesy of Discovery Channel and Vulcan Productions, Inc.

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non—wings level attitude, instead of going up, you are going to turn to a different heading and not go up. A significant amount of the energy is spent doing that initial turn.

“If there was any time spent non—wings level during this turn, you ran the risk of not making your ultimate goal of 100 kilometers [62.1 miles] at the end of the flight.”

A number of things caused the wing to wander back and forth. Asymmetries in the thrust from the rocket engine and asymmetries that resulted from supersonic shockwaves wanted to knock SpaceShipOne off course.

Melvill added, “And there are wind shears that exceed 100 miles per hour [160 kilometers per hour] going in different directions. So as you go up, it will blow you this way and then it blow you that way. You are not there for long, so you don’t get massive changes, but you are constantly correcting.”

By using an avionics system called the Tier One navigation unit (TONU), the pilot could ensure that SpaceShipOne was wings level and had the proper pitch rate, which was a measure of how fast the nose was rising. For the first 5 seconds, the pilot used the control stick and the rudder pedals to keep the wings level. “You can feel the forces start to build quite rapidly,” Binnie said. “And now your thinking is, ‘Okay, I’m going to keep fighting this thing physically until about 8 or 9 seconds, and then I’m going to transition over to controlling the vehicle with electric trims.’” To do this, the pilot took his left hand off the stick and reached for the rudder trim controller, a big black knob that looked liked a turtle shell.

Binnie explained, “As you are going through transonics, where the vehicle is shocking up asymmetrically, it is still rocking back and forth or more like whipping back and forth. Your job is to try to filter out the oscillatory motion and chase down with the turtle any longer-term disturbance that is driving the nose of the vehicle off trajectory.

“You have high-rate motions but you have a low-rate controller. So, things don’t happen as quickly as you’d like them to. You put in an

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Fig. 3.12. Traveling close to vertical, SpaceShipOne’s hybrid rocket engine burned 76-84 seconds during a spaceflight. At rocket engine shutdown, SpaceShipOne was a little more than half the way up to apogee. Mojave Aerospace Ventures LLC, photograph by Scaled Composites

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adjustment, and you’re going to have to be patient to sort of see it take effect. And that is not the easiest thing in the world to do because you just had your brains scrambled. And everything about you is on high alert, and now you have to be patient and wait for the thing to respond. If you don’t, it is easy to over-control it, and you can get yourself into even more trouble.”

As the pilot was finishing the initial pull up, SpaceShipOne passed the rough transonic transition from subsonic to supersonic.

“You settle in around the 10- to 15-second mark and look out the window. And appreciate that you are no longer horizontal. The nose will appear vertical, but it is not quite there yet,” Binnie said.

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Fig. 3.13. Photographed from inside the cockpit of SpaceShipOne by Brian Binnie near the apogee of 367,500 feet (112,000 meters), the Channel Islands and the Pacific Coast peek through the cloud cover as black sky shrouds Earth. Mojave Aerospace Ventures LLC, photograph by Scaled Composites

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Figure 3.12 shows SpaceShipOne and its contrail during the ascent to space.

As SpaceShipOne continued to ascend and slowly move its nose closer to vertical, the use of the control stick came back. The pilot could again use the mechanical controls to fly, even though it traveled much faster than Mach 1 and was still gaining speed. The air density was too low to create much opposing force but still high enough for aerodynamics to work.

At about the 1-minute mark, the rocket engine went through a liquid-to-gas transition. “This is kind of a wake-up call that you are getting near the end of the boost phase of flight,” Binnie said. “The vehicle shakes and shudders some more. And then the rocket motor valve that you are sitting not too far from has some unusual acoustics
associated with it. It sounds like riding along with a possessed cat. It kind of screeches and howls and complains.”

SpaceShipOne reached a maximum speed of Mach 3.09, or 2,186 miles per hour (3,518 kilometers per hour).This occurred just before burnout while it was still accelerating. But the atmosphere was very thin at this point, so the airspeed was only about 40 knots equivalent airspeed.

The highest altitude for rocket-engine shutdown occurred at

213,0 feet (64,920 meters). The burn lasted 84 seconds. Unlike shutdown inside the thick atmosphere, where thrust no longer kept the pilot pinned to the seat and the deceleration force flung him forward in his seat, shutdown at high altitudes was tame because of the thin atmosphere and because the rocket engine’s thrust had tapered off due to the longer burn duration. SpaceShipOne now coasted upward.

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Fig. 3.14. During the 3.5 minutes of weightlessness, the test pilots were able to take photographs from inside SpaceShipOne’s cockpit. In this photograph, the red-colored thermal protection on the leading edge of the right wing can be seen through one of the porthole windows. Mojave Aerospace Ventures LLC, photograph by Scaled Composites

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“Three wonderful things happen/’recalled Binnie. “The noise goes away. The shaking, the shuddering, the vibration go away, and you become instantly weightless. And the weightlessness is just a pro­foundly exciting and pleasurable experience.”

“Then of course there is that view. You’ve seen it on the cover of magazines and things like that. But when you see it for yourself, it is really breathtaking. The eye is so much more dynamic than a video or a camera. It is yours for the enjoyment.”

As SpaceShipOne rocketed upward, light scattered less and less in the dwindling atmosphere. “You can already see the blue skies turning a much darker, deeper shade of blue and as you continue to watch that, it will deepen and darken and kind of go purplish and then to black,” said Binnie.

Figure 3.13 shows the black sky surrounding Earth in a photo­graph taken by Brian Binnie aboard SpaceShipOne. So where are the stars in the black sky? Above the atmosphere there should be stars galore. Well, they are there. However, a camera cannot catch the stars. Earth is much too bright. To see the stars in a photograph, a much longer exposure time is needed, but then the features of Earth would be totally washed out. This phenomenon can also be observed in the famous “Earthrise” photograph taken by the crew of Apollo 8 as they circled the Moon, where Earth is seen rising above the sur­face of the Moon and no stars can be seen in the background.

Following a ballistic arc, the unpowered spacecraft continued to climb, coasting up while the atmosphere dwindled away. To win the Ansari X Prize, it was necessary to reach an altitude of 328,000 feet (100,000 meters). So, as SpaceShipOne raced toward this height, the pilot enjoyed the effects of zero-g. Without the atmosphere, the drag
caused by the air resistance was no longer a factor causing SpaceShipOne to decelerate. Gravity still had a hold on SpaceShipOne, however, and the spacecraft was not traveling at a high enough veloc­ity to escape the pull of Earth.

Having taken an hour to reach launch altitude and separation, the max­imum altitude when SpaceShipOne reached the top of its climb, or its apogee, occurred about 3 minutes after the rocket engine initially fired off. SpaceShipOne stopped moving up at this point and began to free fall back to Earth. The pilot experienced weightless conditions for approxi­mately 3.5 minutes, which he started to feel once the rocket engine shut down. For comparison, the Space Shuttle took 8.5 minutes to go from its launch pad to its orbital altitude of around 200 miles (320 kilometers).

Shot from space, the photograph in figure 3.14 gives a glimpse from SpaceShipOne’s window of the leading edge of its wing high above desert mountains.

While outside the atmosphere, SpaceShipOne could not use its rudders or elevons to control movement whether it was ascending or descending. Since space is a vacuum, there was no air to provide the lift that these control surfaces required to change the spacecraft’s course. This is the same problem faced by the Space Shuttle, as well as other spacecraft and satellites. Even astronauts during extravehicular activity (EVA), floating outside the International Space Station, need a way to steer themselves around. To maneuver in space, they accomplished this by shooting little jets of gas in a direction opposite to that of the intended motion. So, for example, if a spacecraft needed to move to the right, it shot a puff of gas to the left.

SpaceShipOne was no different. In the airless environment, the pilot had to use the reaction control system (RCS) to maneuver SpaceShipOne.

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Fig. 3.15. In an interview with Ed Bradley for 60 Minutes after the Ansari X Prize spaceflights, Burt Rutan shows the feather configuration and describes how it allowed the safe return of SpaceShipOne to Earth’s atmosphere. Mojave Aerospace Ventures LLC, photograph by Scaled Composites

After he switched the RCS on, he used the control stick and rudder pedals to control thrusters mounted on the fuselage and wings.

“We chose to put a microswitch on the end of the travel, so you had to get your knees out of the way just to do anything at all. You had to move the stick all the way to a stop until it closed the microswitch, opened up a valve, and then the jet worked,” Melvill said.

The rudder petals worked the same way, in that they had to be pushed all the way on the floor to activate the thrusters. So, the thrusters would fire as long as the pilot pressed against the microswitches.

After working two years as the director of Bede Test Center for Bede Aircraft, makers of the BD-5J Microjet, Rutan was ready to go it out on his own. In 1974 he founded Rutan Aircraft Factory (RAF) to continue the development of his first airplane, which he began designing back in college and started flying in 1972, and the develop­ment of brand new designs.

“I name very few of my airplanes,” Rutan said. “Even the VariViggen, my first one, was named by a guy at work. I told him I was going to build something that was a lot like the Swedish Viggen, except that it had the feature of variable camber that changed the loading. He said, ‘Okay, how about VariViggen.’” Rutan simply replied, “Okay.”

Although Burt Rutan is well known for the use of composites, the VariViggen’s only use of composites was a fiberglass cowling. The aircraft was made out of wood, and its wings were aluminum. However, it had what would become a hallmark of Rutan’s—a canard. The canard was a small wing forward of the main wing that enhanced lift, allowed for slower maneuvering speeds, and helped prevent stalling. The VariViggen was powered by a pusher propeller at the back of the aircraft and had vertical fins at the wingtips called winglets, which improved the rate of climb and cruising speed. These two features also reoccurred in many of Rutan’s designs. Figure 1.2 shows some of Rutan’s earliest aircraft.

Rutan had begun construction of the VariViggen in his spare time while still working for the air force, and it took him four and a half years to complete it. With only seventy-five hours on the aircraft, Rutan flew the VariViggen to Oshkosh, Wisconsin, to give the public its first viewing during the 1972 Air Venture, the annual fly-in held by the Experimental Aircraft Association (EAA), which is the premiere aircraft organization for homebuilts and experimental aircraft. The crowd thrilled at the futuristic-looking aircraft.

“When you look at the wide variety of his designs from the VariViggen to SpaceShipOne and everything in between,” said Tom Poberezny, the President of EAA, “Burt has been a design leader. He’s always been creative and pushing the envelope.

“If you attend a forum at Oshkosh, it is always a packed house because people want to find out what’s the latest and greatest in Burt’s fertile mind. And that becomes motivational for people in terms of the excitement of being inside of design theory, design thinking, and innovation.”

Rutan gave the VariViggen the tail number N27VV. Characteristic of Rutan, the tail numbers of his aircraft weren’t arbitrary. All U. S. aircraft begin with N, but the “27” stood for the model number Rutan gave it, and VV obviously stood for VariViggen.

Another revolutionary aircraft made its debut at the 1972 AirVenture. The tiny little Rand Robinson KR-1—at a length of 12 feet 6 inches (3.8 meters), a wingspan of 17 feet 2 inches (5.2 meters), and a weight of 310 pounds (140 kilograms)—generated a lot of strange looks and disbelief. Ken Rand’s homebuilt aircraft had started people talking and thinking a little differently about the way airplanes were built. The outer wing panels, vertical and horizontal tail surfaces, and other parts of the aircraft were made using polystyrene—the same stuff foam coolers and coffee cups are made.

Even though plywood, which is technically a composite because it is made of wood layers glued together, was also used to build the fuse­lage, the KR-1 made use of composites like no other aircraft of its time. Polystyrene is very light, but it is also very weak. So, epoxy and cloth made of Dynel, a synthetic fiber, covered the polystyrene in order to give it the rigidity and strength needed to hold together. The KR-1 had a profound influence on the evolution of large-scale use of composite materials in homebuilt aircraft.

Rutan’s next design, the VariEze, also a pusher prop with a canard and winglets, took him only three and a half months to complete by taking the use of composites to a whole new level. “I didn’t have as a goal to build better, lighter, safer, more affordable composite structures. I saw it as a way that I could take a complex aerodynamic shape and build it quickly and get it into flight test,” Rutan said.

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Fig. 1.2. The early aircraft designs and projects of the Rutan Aircraft Factory (RAF) came in many shapes and sizes, including Voyager, AMSOIL Racer, Quickie, Defiant, VariViggen, Grizzly, NGT, Long-EZ, AD-1, Catbird, VariEze, Boomerang, and Solitaire. Provided courtesy of Scaled Composites

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“The KR-1 was a wooden airplane with Dynel and foam to shape its outer shape. Its primary structure was wood—the fuselage and wings and tail—whereas if you took the wood out of it, it would fall apart. The VariEze was different. Its composite was its primary structure.” The composite Rutan had used was polystyrene foam sandwiched between layers of fiberglass. “I started my composite work with moldless methods that I used on the VariEze and the Defiant and a bunch of our airplanes,” Rutan said. “I did that by copying what they did when they did repairs to molded European sailplanes. European sailplanes were made, and still are, in molds.”

But to fix damage to one of these sailplanes, it wasn’t necessary to go back to the mold. “The brainstorm that I had was, ‘Wait a minute, I could build a whole airplane with these repair methods.’ And that’s how I came up with hotwire wing cores and the hand-carved foam for the fuselage box. And sure enough, I built a whole airplane with­out a mold.” Figure 1.3 shows Rutan with a composite panel during the assembly process.

Rutan originally had no intention to sell the VariEze. He built it as a research aircraft to do more testing with the canard concept. But during its introduction to the public at EAA’s 1975 Air Venture, the public went wild for the design. Rutan responded by slightly enlarging the design and selling the VariEze as a kit airplane, so homebuilders could purchase plans and components to build it themselves.

“The VariViggen, the VariEze, all these designs, were unique in the fact that they were out of character from the type of design that was typical of the day,”Tom Poberezny said. “He breaks the mold every time he does something.” Figuratively speaking, of course.

In 1986, Rutan’s Voyager made the first nonstop flight around the world without refueling. It lifted off from Edwards Air Force Base with its tanks full of 7,011 pounds (3,181 kilograms) of fuel, circumnavigated the globe without once landing, covering a distance of 24,986 miles (42,212 kilometers), and then touched down nine days later at Edwards Air Force Base with 106 pounds (48 kilograms) of fuel to spare.

The amazing strength-to-weight ratio of the graphite fiber and honeycomb composite that Rutan used to build Voyager allowed a wingspan of 110 feet 8 inches (33.8 meters) and a primary structure weighing in at only 939 pounds (426 kilograms). Fuel actually accounted for 72 percent of its gross takeoff weight.

It was hard not to notice Rutan’s design and engineering prowess. And soon NASA, defense contractors, and large aircraft manufacturers began knocking at the door. In 1982, the year construction actually began on Voyager, Rutan founded Scaled Composites to specialize in proto­type development, offering design all the way through flight testing of full-scale vehicles or scaled-down versions and models. Figure 1.4 shows early designs that Scaled Composites worked on, including the

Starship, Pegasus, and the Pond Racer. Scaled Composites built some of these designs from start to finish, but for others the company only contributed to part of the construction.

“Things got more conventional,” explained Rutan. “I mean the way we build airplanes. They are still sandwich. They tend to be more honeycomb core than foam core. They tend to prepreg, and we cure them at higher temperatures. We still do them without the autoclave. And we occasionally come up with a breakthrough in manufacturing methods.”

But the manufacturing processes, while important, were never the driving force. As always, it was the design and the need to fly that drove the manufacturing processes. And after about thirty years from the time Rutan graduated college, he started to wonder what was next. Space was never that far from Rutan’s mind, or reach. In his bookshelf was a fat binder that contained original writings of Wernher von Braun. It was the Mars project. Rutan decided, “‘Damn it! Nobody else is going to do this. I’ll do something for space.’ That didn’t dawn on me until about ’93 that if I focused on suborbital, then I could do something interesting.”

Burt Rutan described the idea of the feather maneuver as the pivotal piece of the puzzle needed for the design of SpaceShipOne. Reentry into Earth’s atmosphere was the most critical point of every spaceflight. By deploying the feather mechanism, referred to as “carefree” and “hands – off,” the aerodynamic drag increased substantially, resulting in very low thermal loads. This was because the spaceship slowed down so quickly in the upper atmosphere that when it reached the thick atmosphere, it was traveling with much less energy. Because there was less energy, there was less heat being generated, and SpaceShipOne didn’t get as hot. On ascent after the boost, as SpaceShipOne continued to slow and close in on apogee, the test pilot put the feather up. “We put the feather up because we want to have as much time as possible to troubleshoot if it doesn’t
go up,” Melvill said. “It goes up with two different pneumatic actuators, either one of which can do the job. They are fed out of two separate high-pressure bottles. And you can put both bottles to one or the other. We had redundancy.”

Going up to space had its challenges, but coming back down was where a space program was truly tested. And the feather was SpaceShipOne’s ticket back home. Figure 3.15 shows SpaceShipOne with its feature in the extended position.

“So, we would put it up as soon as we were out of the atmosphere because if we put it up in the atmosphere, we would start doing loops.”

The rear half of each wing folds upward about a hinge line, looking like a jack-knife. It took less than 20 seconds for the feather to deploy to an angle of 65 degrees, and the pilot watched the instrument panel to make sure it went all the way up.

“As soon as you moved the handle, that unlocked it, and as soon as it was unlocked, you’d hear it,” Melvill said. “Without the motor running, it was very quiet. And you would hear it go konk in the back as it unlocked. As soon as we heard that, you would put the feather up with the handle. There were two handles right next to each other on the left side. The feather took a long time, and it made a noise going up. You could hear the air hissing into the large-diameter actuators.”

After SpaceShipOne reached apogee, going over the top, it began to pick up speed and continued to follow a ballistic arc downward much

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Fig. 3.16. The feather extends and retracts by air-powered actuators, or pistons, that are attached on either side of the fuselage and connected to each side of the wing near their trailing edges. Mojave Aerospace Ventures LLC, video capture provided courtesy of Discovery Channel and Vulcan Productions, Inc.

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like the parabola traced by a ball thrown into the air and as it drops back down to the ground.

The spacecraft had a lift-to-drag ratio of about 0.7 in the feathered configuration, so the descent was nearly vertical, with an angle of attack of 60 degrees. While in space, a video camera mounted in SpaceShipOne’s tail boom captured the image of the feather shown in figure 3.16.

Now as SpaceShipOne transitioned from space to reentry, the atmosphere began to get thicker and thicker. Mach 3.25 was the fastest reached by SpaceShipOne. This corresponded to an airspeed below 160 knots equivalent airspeed.

“You come back a little faster than you go up,” Melvill said. “You get a tremendous amount of g-forces on your body when you are coming back. We were looking at 5.5 g’s on reentry.”

The pilot didn’t wear a g-suit. But he did experience a decelera­tion force above 5 g’s for around 10 seconds. Since the pilot sat upright the entire flight and SpaceShipOne reentered the atmosphere belly first, it was critical for the pilot to train beforehand in order to build up his g-tolerance.

“You see because of the rods and cones in your eyes,” Melvill explained. “They need oxygen-enriched blood to feed them. If the blood gets drained down to where there is not much oxygen – enriched blood behind your eyes, you go blind. You just black out. And you can still hear and think and move the stick. But you can’t see. And that would be hard to fly if you couldn’t see.”

In the feather configuration, SpaceShipOne acted like the conical­shaped shuttlecock, or birdie, used in the sport of badminton. Originally made of feathers and now more commonly made of plastic, the shuttle­cock’s skirt has such high drag compared to its base that after a hit from a racket, the shuttlecock automatically orients itself base-first in the direction of flight. The Scaled Composites team took advantage of the two important aspects of this concept when considering the reentry of SpaceShipOne. The high drag caused rapid deceleration, and the self-aligning tendency ensured the proper orientation.

“You don’t even need to do anything coming back down. It is a ‘carefree’ reentry,” Melvill said. “You could put your hands behind your head and take your feet off the rudder pedals and just wait. And you could reenter in any attitude. You could be tumbling when you reenter. You could be upside-down when you reenter. You could be knife-edge and the feather will turn you around and straighten you out. It happens real slowly.”

A terminal velocity of 60 knots equivalent airspeed is reached in this high-drag configuration. This corresponds to a ballistic coefficient,
calculated by using the weight, drag, and cross-section of SpaceShipOne, of 12 pounds per square foot (psf), compared to that of 60 psf for the early Mercury capsules. A low value of the ballistic coefficient means that the spacecraft will begin to slow down quickly in the thin atmosphere. So, SpaceShipOne experiences only low overall structural and thermal loading. It goes from supersonic to subsonic in about a minute and a half.

“The temperature when we reenter around the airplane is very high,” Melvill said. “It is about 1,200 degrees, but that’s the air temperature against the skin. Because that happens at 100,000 feet [30,480 meters] or more, there is so little air to conduct the heat into the structure. The molecules of air are so far apart because it is only 1 percent, or less, atmosphere up there. So, it takes time for that heat to be conducted into the structure, and we’re through that heating period before it has time to get into our airplane. Burt designed it that way, and that was very clever. He made sure that we wouldn’t spend very much time under the conditions where we could melt the airplane.”

During a presentation at the Experimental Aircraft Association’s 2006 AirVenture at Oshkosh, Wisconsin, Rutan described the differ­ence between the thermal protection system of SpaceShipOne and the Space Shuttle: “You don’t have the problems going Mach 4 that you do going Mach 25.

“On the boost, SpaceShipOne sees temperatures that are too hot for the skin at the nose and on the leading edges. That’s all. To be conser­vative, we protected some of the areas that got relatively hot on reentry. That’s why you see that stuff down under the nose and up underneath the wing. However, our measurements there showed that none of that was required. SpaceShipOne doesn’t need any thermal protection at all for reentry. It only needs several pounds of material for boost.”

In cooperation with the U. S. Air Force, SpaceShipOne reentered into restricted airspace controlled by Edwards Air Force Base. But within the restricted airspace, the Office of Commercial Space Transportation (AST) had designated a location, a box roughly 2.5 square miles (6.5 square kilometers) in size, for SpaceShipOne to come down through during reentry.

This was certainly a piloting challenge because in order to reenter through the box, the pilot already had to be in position on the way up. So not only did the pilot have to make sure the wings were level, the nose was pointed up, asymmetries were compensated for, and the occasional wind shear was counteracted, he had to try to position SpaceShipOne so that once the engine shut down and the atmosphere was gone, it would coast more than 100,000 feet (30,480 meters)

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Fig. 3.17. SpaceShipOne returns from space as a glider and makes a horizontal landing similar to way the Space Shuttle does it. Although not the most efficient glider, SpaceShipOne had a glide range of around 60 miles (97 kilometers). Mojave Aerospace Ventures LLC, photograph by Scaled Composites

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“Our priorities were we wanted to get altitude, and we wanted to leave the atmosphere without a lot of body rates or gyrations,” Binnie said.

The third goal was to come back inside the box. “But controlling the body rates and maneuvering the vehicle to find that box were kind of at odds with each other.”

SpaceShipOne continued to descend with its feather up. This configuration was so stable that in the atmosphere at the higher altitudes, it was easier for the pilot to just leave the feather up, even though SpaceShipOne had performed a safe reentry. However, there wasn’t much control. The pilot couldn’t pitch the nose and roll the wings, but he was able to change the direction that the nose pointed.

“This is something we didn’t feel necessary to test, but it is likely that you could survive a feather-up landing in SpaceShipOne,” Rutan said. “We did not plan to ride it down if the feather didn’t come down. We planned to jump out.”

At an altitude below 70,000 feet (21,340 meters), the feather was retracted and locked. SpaceShipOne, flying subsonically, transformed into a glider.

“I always had the space bug, keep in mind,” Rutan said. “When did I jump in and do it myself? It came in a time when I thought I could do it. And it wasn’t with SpaceShipOne at first. I was going to do a capsule, and launch it from an airplane that did a steep climb and a parachute recovery.” He began sketching out ideas in 1993.

“I was going to build something to fly out of the atmosphere. I’m not saying the things that I originally laid out were easy. They weren’t easy, but they weren’t really innovative. They were pretty straightforward. It didn’t require anything that was new or patentable or breakthrough in nature.”

His first ideas focused on a single-person rocket carried as an external store by a mothership. The carrier aircraft would pull up and then shoot it off like a missile.

“Around 1995 or so, we were designing and starting to build an aircraft called Proteus,” said Doug Shane, the vice president of business development and the first engineer that Rutan hired at Scaled Composites. An award-winning test pilot himself, Shane also became director of flight operations, which is a position he has held at Scaled Composites since 1989. Figure 1.5 shows Shane in Mission Control with Rutan at his side.

Proteus was a utility aircraft designed to fly at high altitudes above

60,0 feet (18,290 meters), but one of its design requirements was to launch a single-person suborbital rocket. Proteus would perform a zoom maneuver at 27,000 feet (8,230 meters), pulling up to 40 degrees to assist the rocket’s trajectory. Figure 1.6 shows the original launch concept with the rocket attached by an offset mounting, and figure 1.7 shows its separation from Proteus.

When Rutan got word of the formation of the X Prize, well before it was called the Ansari X Prize, he decided to change the design from a single-person capsule to a three-person capsule, which was a condition set forth by the X Prize. Figure 1.8 shows the rocket during ascent and the capsule and booster parachuting down after reentry.

The most important part of the design of the spacecraft was the feather, the little protuberances pointed upward away from the blunt end of the capsule. Acting and looking like the “feathers” of a

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Fig. 1.3. Burt Rutan began his pioneering work with composites on the VariEze, the second air­plane he designed and built. In 1975, the VariEze took him three and a half months to construct, whereas his first airplane, the VariViggen, took more than four and a half years. Mojave Aerospace Ventures LLC, photo­graph by Scaled Composites

к________ ) badminton shuttlecock, the design would accomplish two very important things. First, the high drag would decelerate the capsule very quickly, which would tremendously reduce the thermal loading and the dangers of heat buildup during reentry. And second, it would act to self-right and stabilize the capsule, orienting the capsule’s blunt side down no matter what the attitude during initial reentry. Rutan would call this his “carefree” reentry. This allowed the spacecraft to reenter at a near-vertical trajectory. The Space Shuttle, in comparison, had to precisely control its attitude during reentry, too shallow and it would skip off the atmosphere, too steep and it would experience catastrophic heating.

The capsule would then float down over the water. “I wanted to pick it out while it was still under the chute with a helicopter,” Rutan said.

The method was very similar to the way that film canisters ejected from the very first spy satellites were recovered during Project Corona, the joint effort between the Central Intelligence Agency (CIA) and U. S. Air Force. A film canister would parachute down, and an aircraft with a large catch would swoop by and snag it out of the sky.

“My baseline at first was that if it went into the water it was an unexpected failure or emergency. I wanted to grab them and helicopter them back to the launch site,” Rutan said.

Something about a parachute and helicopter blades make it seem like a bit of an odd combination, though, even for Rutan. “When you work with parachute recovery,” Rutan mused, “you take certain generic risks that you just can’t get around. And I thought I could do it. I think it was a much bigger decision that led me to develop something that could survive a steep reentry and land on a runway and not have to be controlled in attitude during reentry.

“That concept, that design, that approach was much more significant.”

So, the ideas of a capsule and a parachute were scrapped. But air launch was still on the table. Scaled Composites would also stick with

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Fig. 1.4. Scaled Composites built complete aircraft as well as components for many vehicles. Just a few of these are Pegasus,

Starship, Triumph, ATTT, ARES, and Pond Racer. Provided courtesy of Scaled Composites

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using the name “feather” even though the final design looked more like a pair of broken wings.

“If you can buy some time in the event of a propulsion problem instead of being this high off the ground when the motor quits or does something funny,” said Shane while sticking his hand out to his side about four feet off the ground, “if you are at 50,000 feet [15,240 meters], you really have a lot more time to deal with it. It gives you an awful lot more options.”

Early models, like those shown in figure 1.9 and figure 1.10, used a high-drag speed brake and large deflecting elevons as the feather mecha­nism for reentry. And Rutan’s team demonstrated several models where the feather worked subsonically. But when it came to supersonic speeds, like those encountered during reentry, they didn’t trim supersonically. In other words, they were uncontrollable. If the center of gravity (CG) was moved back, they would fly okay, but then they became unstable at sub­sonic speeds. A computerized fly-by-wire flight control system might have made them flyable, but the cost was too high and the reliability too low.

This was an enormous setback. Only two manned, winged vehi­cles had made it to space, the X-15 and the Space Shuttle. Both had fatal accidents during reentry. An X-15 had a flight-control failure in 1967, and the Space Shuttle Columbia had a failure of its thermal protection system in 2003. It was necessary to solve this problem before any more forward progress could be made.

“Finally, maybe it was some spicy food he ate late at night or some other kind of epiphany,” Shane said about Rutan. “He suddenly realized that maybe the thing to do would be to pivot part of the wing and the tails on a hinge on the body and provide that high-drag configuration. And that ended up satisfying all the subsonic and supersonic aerody­namic challenges. That was actually a pretty clever concept, and that’s what we went forward with.”

Figure 1.11 shows the new spacecraft design with the feather deployed for “carefree” reentry.

With the wings returned to the normal flight configuration, SpaceShipOne became a glider. The hard part was certainly over, and the pilot had time to take a breath and take in the view again. But his work was not completely over. Figure 3.17 shows SpaceShipOne gliding over the high desert of Mojave.

If SpaceShipOne was off course during the boost phase, it could be far away from where it needed to land. However, the spacecraft had a glide ratio of seven to one. So, SpaceShipOne had glide range of about 60 miles (97 kilometers) after it defeathered. “It’s got an awful lot of capability to deal with poor trajectory,” Doug Shane said.

The pilot also had to resolve a technical glitch with the global positioning system (GPS) receiver. It would drop out or lose its way during spaceflights. “The GPS receiver was never previously tested in that high and in that fast of a flight regime,” Pete Siebold said. “And so it had software difficulties of its own. The GPS receiver was some­thing you buy from a company off the shelf. It just didn’t perform the way it was supposed to.”

In one of the spaceflights, the GPS receiver reset by itself, but for the other two, the pilot had to reset it.

“So, we had to do a power cycle. The avionics go away while it is booting back up, and then it does a realignment of the inertial navi­gation system once it powers up again. But we could live with that fault. We had workarounds,” Siebold said.

The spaceship glided down for 10—15 minutes and was much lighter now that the oxidizer and fuel were burned off. SpaceShipOne was not able to land safely with a full load of oxygen and fuel. The extra weight changed the balance, and it was just too heavy for the landing gear to take. So, for an abort, it would have to dump all the nitrous oxide, but it still had to manage with the remaining mass of rubber.

Although SpaceShipOne did a good job gliding down and getting close to the airport, it did not have all the controls or responsiveness of a typical glider, so its maneuvering when it came to landing was limited. Early in the program, a few landing attempts were almost too short or too long for the runway.

Pete Siebold and Brian Binnie modified the landing technique, allowing SpaceShipOne to easily compensate for coming in too high or too low. “We would fly at 8,500 feet [2,590 meters] above sea level above our touchdown point,” Siebold said. “And we had a 360-degree turn to make back to that point again, and then we would be lined up for the final touchdown on the runway. The original technique allowed you to vary the radius of that turn. If you were too low, you could decrease the radius, and your circumference was your flight path. And if you were too low, you could make up for being low on energy by flying that tight radius. Or you could widen it out.

“We also had one last-ditch effort to make any adjustments, and that was to put the landing gear down. When the landing gear was up,

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Fig. 3.18. Landing proved to be a bigger challenge than anyone had anticipated. There was only one shot at it. SpaceShipOne had to come in at the right altitude and speed or it risked overshooting or undershooting the runway. Mojave Aerospace Ventures LLC, video capture provided courtesy of Discovery Channel and Vulcan Productions, Inc.

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Fig. 3.19. Once SpaceShipOne touched down, steering was very limited. The nose skid and the rear landing gear’s brakes brought the craft to a quick stop, but since it was unpowered, it needed some help to get off the runway. This photograph shows Sir Richard Branson, Paul Allen, and Burt Rutan (left to right) sitting on the tailgate with SpaceShipOne under tow. Dan Linehan

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it was a seven-to-one glide ratio. With the landing gear down, it was a four-to-one glide ratio. The problem was that once you put it down, you couldn’t put it back up. So, you had to be sure that you had sufficient elevation to make the runway.”

SpaceShipOne would spiral in for a landing while reaching key alti­tude points that were provided by the TONU. An energy predictor similar to what was used during boost showed the pilot where SpaceShipOne would be at the key altitudes based on the current turn and descent rates. The pilot would then adjust his speed and turn so that SpaceShipOne would end up at the place it needed to be.

“After we developed that and utilized it, we landed to within 500 feet [150 meters] of a given touchdown point on every subsequent flight. That was real rewarding,” Siebold said.

SpaceShipOne approached the runway at an airspeed of 140 knots indicated airspeed. But in order to put its gear down, it had to perform a special maneuver. “There were other peculiarities with the gear sys­tem,” Siebold explained. “You couldn’t put it out at your normal approach speed. So, the speed at which you flew the pattern was too fast to put the gear out and too fast to land. So, what you had to do was in your turn from base to final, you actually had to pull the nose up, slow the airplane down, put the gear out, dump the nose, with gear extension at 125 knots, and then speed back up to 140 knots.” Figure 3.18 shows SpaceShipOne gliding down to the runway at Mojave Airport.

The pilot had one last challenge to face. As it turned out, it was one that Charles Lindbergh faced seventy-seven years previously in

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Fig. 3.21. The North American X-15 was the only other manned, winged suborbital vehicle. SpaceShipOne shared some similarities with it, but trajectory was not one of them. The high-altitude and high-speed mission trajectories of the X-15 are shown in comparison to the SpaceShipOne trajectory. Mojave Aerospace Ventures LLC, provided courtesy of Scaled Composites

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Fig. 3.20. The X-15 had enough fuel to power its rocket engine for about 2 minutes, so it required a B-52 to lift it to launch altitude. The X-15 flew from 1959 to 1968, posting a top speed of Mach 6.70, or 4,520 miles per hour (7,270 kilometers per hour), and a maximum altitude of 354,200 feet

(108,000 meters) on separate flights. NASA-Dryden Flight Research Center

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Table 3.2 SpaceShipOne’s and X-15 Suborbital Mission Comparison

Program goals

Number of vehicles in program Crew capacity

Number of rocket-powered flights

Combined time of rocket-powered flights (hours:minutes:seconds)

Number of flights above 100 kilometers (62.1 miles/328,000 feet)

1 st stage

Separation altitude Engine type Oxidizer and fuel Maximum engine burn time Trajectory for boost and reentry Maximum airspeed Maximum altitude Weightless time Reentry method Reentry max q Approach airspeed Touchdown airspeed Landing surface

Number of vehicles lost during flight testing Number of fatalities during flight testing

X-15

High speed and altitude 3 1

199*

30:13:49*

2

NASA B-52 carrier aircraft

45.0 feet (13,720 meters)

Liquid

Liquid oxygen and anhydrous ammonia 141 seconds (high-speed mission)

Approximately 40 degrees (high-altitude mission) Mach 6.70

354,200 feet (108,000 meters)

3.5 minutes

Pilot controlled pull-up

1.0 psf (550 KEAS)

270 KEAS

180 KEAS Lake bed 1 1

the Spirit of St. Louis, which had no front windshield. “The visibility out of SpaceShipOne is pretty restricted, and you got these really small windows, and there is no window in front,” Melvill said. “So, when you are lined up with the runway, you can’t see the runway. With a normal airplane, you can look out the front and see the runway.

“This one, the windows were on the sides, and as long as you were turning toward the runway, you could see it through the side win­dow. But as soon as you lined up with the centerline, you couldn’t see it anymore. The whole airport disappeared. So, that was a little bit
disconcerting I think for all of us. That’s why we had a chase plane sit­ting right on the wing calling out how high we were above the ground and basically keeping us straight as well.”

At 100 to 110 knots equivalent airspeed, the main landing gear at the rear hit first, and then the nose skid followed. There was no real way to steer once it touched down. The wooden tip of the nose skid brought it to a smooth, but slightly smoky, stop in front of an ecstatic crowd. Figure 3.19 shows SpaceShipOne being towed from the runway accompanied by Paul Allen, Burt Rutan, and Sir Richard Branson.