Category Space Ship One

Similar to the Bell X-l, as shown in figure 6.6, which in 1947 was the first aircraft to break the sound barrier, SpaceShipOne used elec­tric, motor-driven control surfaces to maneuver. After SpaceShipOne
broke the speed of sound during test flights, the subsonic flight con­trols no longer functioned efficiently.

“Once you are supersonic, the control system that you normally use to fly the airplane doesn’t work anymore,” Melvill said. “Because it is a mechanically controlled airplane, there is no hydraulic system like there is on an F-16 or F-l 8. It is just cables and pushrods. You are just not strong enough to move the controls at that point. So you just revert to using the trim switches.”

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Fig. 6.6. Because the forces pushing against the control surfaces of the X-1 were so strong while flying at supersonic speeds, the pilot could not use conventional mechanically linked flight controls. The control surfaces had to be electrically controlled and moved using electric motors. SpaceShipOne used a similar system for flying above Mach 1. NASA-Dryden Flight Research Center

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Many aircraft have trim controls that help the pilots maintain course by slightly altering control surfaces. By changing a trim setting, a pilot can fine-tune the control surfaces, so less force has to be applied to the control stick and rudder pedals in order to stay on course. SpaceShipOne uses trim controls in a somewhat similar way during supersonic flight.

A switch on the top of the control stick activated electric servos that pivoted the entire horizontal stabilizer on each side of SpaceShipOne for pitch trim. In figure 6.7, a close-up of a tail boom shows the numeric scale that indicates the amount of deflection for the horizontal stabilizer as set by the pilot.

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Fig. 6.7. Triangular strakes were added in front of the horizontal stabilizers, which were also enlarged, to improve the aerodynamics of SpaceShipOne. The numbers to the right of the strake show the amount of trim or deflection of moveable horizontal stabilizers. Mojave Aerospace Ventures LLC, photograph by David M. Moore

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A knob at the pilot’s left side called the “turtle” activated the lower half of each rudder, giving yaw trim. “Yawing the airplane caused it to roll because of the high wing and the swept leading edges,” Melvill said. “We actually didn’t use the roll trim. It was too powerful. We used yaw trim to roll the plane. If it was rolling off to the left, you would yaw it to the right.”

The lower rudders were synced and moved in the same direction, unlike the upper rudders used in subsonic flight. “The geometry is such that they go out a lot and in just a little bit,” Rutan added. “But they never work opposite.”

Trimming was also used to restrict the movement of SpaceShipOne during test flights. For example, when Mission Control monitored the trajectory of SpaceShipOne, they would instruct the pilot to make trim changes in order to help him stay on course.

More than midway through the burn, the atmosphere became so thin that the supersonic flight controls were no longer needed. The pilot was able to control SpaceShipOne with subsonic flight controls, even though it was flying much faster than the speed of sound, because the rarified air produced little opposing force. When SpaceShipOne fully left the atmosphere, the pilot then switched over to the RCS.

After a little less than three months, SpaceShipOne was ready to return to the air again, with Pete Siebold at the controls. However, its rocket engine would be quiet during this test flight.

“It was after the famous 11P flight, which resulted in significant damage to the aircraft on the hard landing,” Siebold recalled. “It was

in one respect what we would call a functional check flight after any major modifications to the airplane. We wanted to go fly it in a semi – benign environment and try and shake down any of the problems that we may have overlooked or additional problems that had been created due to the modifications.

“The other reason was we made some modifications to the aero­dynamic shape. We added the thermal protection to the aircraft. If you look at the artwork of that flight, it shows the red leading edges and shows the TPS addition. That actually changed the wing shape slightly and the aerodynamic shape. So, we wanted to go and fly that and see if there were any ill effects to that modification for the flight.”

Siebold started off his second time flying SpaceShipOne at an altitude of 48,500 feet (14,780 meters), which was the highest point that White Knight ever released SpaceShipOne. Scaled Composites had originally planned on releasing SpaceShipOne from an altitude of 50,000 feet (15,240 meters). However, White Knight had a very difficult time flying this high and too frequently had come out of afterburners or flamed out altogether at an altitude even below this one. The lower launch altitude did actually work in SpaceShipOne’s favor.

During powered flight, the first thing that SpaceShipOne had to do was “turn the corner” as soon as it possibly could, but the higher the altitude, the less air there was for the wings to bite into in order to make a quick turn upward. So, in terms of utilizing the energy from the rocket engine as efficiently as possible, launching below 48,000 (14,630 meters) feet gave better overall performance, since SpaceShipOne would spend more time pointing up than over.

However, since Siebold wasn’t concerned with lighting off the rocket, he wanted all the altitude he could get for the glide flight. “There were some minor glitches,” he said. “The thermal protection system started cracking at low temperatures, and I think there was actually a formulation change made between that flight and the actual powered flight.”

But the thermal protection system (TPS) wasn’t the only system being checked out. Siebold also evaluated the reaction control system (RCS) that would be used to maneuver SpaceShipOne while in the absence of the atmosphere. This and other testing worked out smoothly, and SpaceShipOne touched down safely, even in the presence of a strong crosswind.

Because there is no atmosphere in space, the flight control systems that ordinarily allow an aircraft to move through the air do not work for spacecraft moving through space. Rudders, elevators, and ailerons only work because air moves over them. With no air, they are useless.

In order to maneuver in space, spacecraft take advantage of a simple physics law discovered by Sir Isaac Newton:for every action, there is an equal and opposite reaction.

Without considering a spacesuit, for example, if a person was in space and blew through a straw, the air would move out the straw in one direction and the person would move in the opposite direction.

Figure 6.8 shows an astronaut with a hand-held reaction control system (RCS). To move, he just points the opposite direction, releases a puff of gas, and off he goes in the direction he wants. This, by the way, is the same principle by which a rocket engine works. The RCS thrusters are just miniature rocket engines.

( ■ >1 Fig. 6.8. In Gemini 4, astronaut Ed White made the first U. S.

spacewalk. To maneuver during his 23-minute extravehicular activity

(EVA), he used a hand-held self maneuvering unit (HHSMU) that shot

little bursts of gas, which allowed him to move around. This device

worked similar to the way SpaceShipOne’s reaction control system works.

NASA-Johnson Space Center

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The Space Shuttle uses a fuel of monomethylhydrazine (MMH) and an oxidizer of nitrogen tetroxide (N204) for its RCS. These pro­pellants react together spontaneously once in contact. As long as each chemical is stored safely separate, they provide the orbiter a simple, reliable, precise, and powerful RCS.

SpaceShipOne had limited time in space and was much less massive than the Space Shuttle. The force generated by these expensive and toxic chemicals was not required. So, puffs of air were sufficient to maneuver SpaceShipOne in space.

After the aerodynamic control authority was gone, the pilot used the RCS to help slow down or null any rotation that had developed while exiting the atmosphere. Each wingtip had roll thrusters, and along the top, bottom, and sides of the fuselage were pitch and yaw thrusters. Each of these thrusters was essentially a port from which high-pressure air could be expelled, and each thruster had a backup. Redundant 6,000-psi bottles of air powered the RCS. By fully extend­ing the rudder petals and the control stick, the pilot maneuvered SpaceShipOne by triggering microswitches that turned the appropriate thrusters either full-on or full-off.

The RCS was also used to get into position for reentry. Scaled Composites had confidence that the feather would self-right SpaceShipOne. However, they did not want to start off upside-down if they didn’t have to.

Tier One Navigation Unit

The pilot had to fly a specific trajectory carefully during a mission. If he deviated, he risked not only failing to reach the target altitude but also missing the prescribed reentry area or, in the extreme case, being too far away from the landing site.

“The aircraft itself was completely manually controlled,” Pete Siebold said. “So, the only feedback the pilot had to how the airplane was flying was through the avionics system.”

It was necessary to develop an avionics system, called the Tier One navigation unit (TONU), for SpaceShipOne. “There really was nothing available within our budget and nothing available off the shelf that suited our needs. So, we had to go develop it ourselves,” Siebold said. The system navigation unit (SNU) and the flight director display (FDD) were the two primary components that made up the TONU.

“We had contracted a company to basically develop the hardware portion of the nav system,” Siebold said. “They built the boxes and put the computers in. They were initially responsible for developing the software of the navigation system as well. However, we ended up making major modifications to that software at the end of the program to make it perform the way we needed it to perform. On the display side, we wrote all the software for the entire program from the beginning.” Aside from being a test pilot, Siebold was the engineer behind most of the software design. Fundamental Technology Systems (FTS), also an Ansari X Prize competitor, provided the hardware and initial software to Scaled Composites.

Acting as the brain of the TONU, the SNU incorporated both a global positioning system (GPS) and an inertial navigation system (INS). It sent guidance and navigational information to the pilot, who saw it on the liquid crystal display (LCD) screen of the FDD in glass- cockpit-type fashion. The SNU navigates along the primary flight axes in six degrees of freedom: the translations of left/right, forward/back, and up/down and the rotations of yaw, roll, and pitch.

Close-ups of the FDD are shown in figure 6.9 and figure 6.10, which also show the similarity between the cockpits of SpaceShipOne and White Knight.

Fly-by-wire was not an option. Siebold said, “It wasn’t warranted for the complexity of this program. Fly-by-wire adds a whole order of magnitude to the whole vehicle development costs. And we really wanted to keep this as simple as possible in order to make this affordable for everybody. That is really the backbone of this program. If you can make it as simple as a Volkswagen, then everybody can afford it. If it needs to be as complex as the Space Shuttle, then nobody can afford it. We really had to push really hard toward making it affordable from the onset.”

The data available to the pilot is based on several modes that correspond to the different phases of flight for SpaceShipOne. Figures 6.11 to 6.14 show various FDD modes, including a boost, a reentry, and a glide. In these modes, the pilot is given trajectory guidance with respect to a detailed map that tracks the position of SpaceShipOne. The FDD automatically stepped through the different modes while flying the mission, but a control allowed the pilot to manually move through the modes in the unlikely event he needed to do so.

Siebold said, “We had the initial boost portion. So, that was the pull up. Then it transitioned to a pseudo-boost mode were every­thing zoomed in and allowed you to track your final target, fly that

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Fig. 6.9. A close-up of the flight director display (FDD) for SpaceShipOne is shown in this photograph. The FDD was part of the Tier One navigation unit (TONU) and provided the test pilot with instruments similar to the way a glass cockpit does for an airliner.

Mojave Aerospace Ventures LLC, photograph by David M. Moore

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Sometimes SpaceShipOne nearly pointed straight up, and sometimes it was upside-down. The attitude, or orientation, of SpaceShipOne in flight was key flight information provided on the FDD. “It showed you whether or not you are at wings level,” Siebold explained. “One unique aspect of the display was that as you pitched the nose up, when the horizon on the display disappeared, it still gave you situa­tional feedback to tell you what attitude the aircraft was in.”

A second key piece of flight information was the velocity vector. “What that tells you,” Siebold said, “is the direction in which you are currently flying—the direction in which your velocity is currently heading. That was depicted on the screen with what we called the green apple. It was a green circle with a tail and two wings pointing out of it.” So, with the pilot knowing how SpaceShipOne was oriented and how it was moving in flight, the FDD offered two other bits of crucial flight information. These were the location of the optimum trajectory, represented by the “red donut,” and where SpaceShipOne was with respect to it, which was the “green apple.”

In a presentation at NASA Ames, Doug Shane had given the follow­ing succinct description: “The goal is to take that green velocity vector and put it right over that red donut, because that is the flight-director cue. And that gets you to the reentry point that you want. Very simplemindedly, your task is only to get those two circles closed up as quickly as you can. And that establishes essentially a vertical trajectory and gives you the best performance that you can get.”

In addition, the SNU monitored and recorded how the systems of SpaceShipOne were performing and fed this information to the FDD, where it was displayed. “It acted as a caution/warning/advisory system,” Siebold said. “It told you if there is any parameter out of limits, or if

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Fig. 6.10. The inside of White Knight’s cockpit, shown here, is remarkably similar to the cockpit of SpaceShipOne. Even the instrumentation and controls are nearly identical, with the obvious exception that SpaceShipOne has rocket-engine controls and White Knight has jet-engine controls. Since White Knight started flying about a year before SpaceShipOne, this allowed Scaled Composites to build up confidence in the instruments prior to flying SpaceShipOne. Also, White Knight could be used as a trainer for SpaceShipOne. Mojave Aerospace Ventures LLC, photograph by Scaled Composites

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there is anything out of limits that would cause you to abort the flight. We had a small list of parameters that if they ever exceeded some allowable range, they’d flash a big red sign that said ‘abort.’”

During the rocket engine burn, things happened fast. There was not a lot of time to make decisions. The TONU did not automatically control SpaceShipOne. “The pilot still had to look at the information, digest it, and make the appropriate decision with that information,” Siebold said.

Data that the SNU collected then displayed to the pilot on the FDD was also transmitted real-time to Mission Control on the ground by a radio frequency (RF) telemetry downlink. In Mission Control, the data reduction system (DRS) collected, processed, and stored all the trans­mitted data and made it accessible to everyone in Mission Control.

Why did the desert tortoise cross the runway? Now that Scaled Composites planned a longer burn, it could no longer fly under the radar of the FA A. Scaled Composites needed a commercial launch license, and the Office of Commercial Space Transportation (AST) of the FAA required Scaled Composites to do an environmental impact report as part of the application process.

Doug Shane explained, “One of the caveats that came back with that [application] is before taking off in White Knight and before landing in SpaceShipOne, we had to do a sweep of the Mojave runway for desert tortoises. And if we found a desert tortoise, we couldn’t move it. We couldn’t touch it. We couldn’t talk to it. We couldn’t negotiate with it. We couldn’t threaten it. We couldn’t bribe it in any way.

“What we had to do was call the desert tortoise control specialist from Ventura County, about a three-hour drive away, and let them come and negotiate some kind of a successful conclusion.”

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Flight Test Log Excerpt for 12G

Date: 11 March 2004

Flight Number Pilot/Flight Engineer

SpaceShipOne 12G Pete Siebold

White Knight 49L Brian Binnie/Matt Stinemetze

Objective: The twelfth flight of SpaceShipOne. Objectives included: pilot proficiency, reaction control system functionality check, and stability and control and performance of the vehicle with the airframe thermal protection system installed. This was an unpowered glide test.

(source: Mojave Aerospace Ventures LLC, provided courtesy of Scaled Composites)

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Fortunately, Scaled Composites got their license, no tortoises made runway excursions, and flight 13P was a go. Pete Siebold, who would have the controls of SpaceShipOne for the second power flight, recalls, “That was the first time that we flew basically at our heavy weight. First time we put all the nitrous on board. The airplane was fully ballasted to be a representative weight for the spaceflights. It was part of that incremental weight expansion.”

Right upon release from White Knight at 45,600 feet (13,900 meters) and 125 knots, though, SpaceShipOne ran into problems. “We pulled the nose up to maintain our speed, and we realized that the wings at that weight and speed could not lift the vehicle,” Siebold said. “So, the wings were stalling earlier than anticipated. So, there was this problem that we were faster than we wanted to be to light the rocket, which would result in an overspeed.

But we also didn’t want to abort the flight, because we had some really questionable handling qualities if we dumped all the nitrous to our landing weight. It would send our CG dangerously far aft.”

Flight Test Log Excerpt for 13P

Date: 8 April 2004

Flight Number Pilot/Flight Engineer

SpaceShipOne 13P Pete Siebold

White Knight 53L Brian Binnie/Matt Stinemetze

Objective: The second powered flight of SpaceShipOne. Forty seconds motor burn time. Handling qualities during boost, through transonic and supersonic. Reaction control system functionality inflight and feather configuration stability during transonic reentry. Evaluation of radar tracking capability.

(source: Mojave Aerospace Ventures LLC, provided courtesy of Scaled Composites)

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Fig. 8.5. Nearly four months after the first rocket-powered flight test, Pete Siebold ignited the rocket engine of SpaceShipOne for 40 seconds and reached an apogee of 105,000 feet (32,000 meters). He hit a top speed of Mach 1.6 on the boost and Mach 0.9 on the way down. Mojave Aerospace Ventures LLC, video capture provided courtesy of Discovery Channel and Vulcan Productions, Inc.

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Fig. 8.6. SpaceShipOne reached a third of the way up to the Ansari X Prize goal of 328,000 feet (100,000 meters). This was all part of the incremental testing plan. Although not able to test the feather while moving supersonically, Pete Siebold was high enough to test the reaction control system (RCS). Mojave Aerospace Ventures LLC, video capture provided courtesy of Discovery Channel and Vulcan Productions, Inc.

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Ignition was delayed by two minutes as Mission Control tried to decide whether to abort the flight or just to go ahead with the burn.

“One of the benefits we had in delaying was we went to a lower altitude, which would allow us to turn the corner much faster, which minimized the risk of overspeed in starting the flight at a higher than expected airspeed,” Siebold said.

After dropping for more than a mile, Siebold lit the rocket engine at 38,300 feet (11,670 meters). Figure 8.5 shows Siebold during the pull-up after rocket engine ignition.

SpaceShipOne was moving at Mach 1.6 when Siebold shut down the rocket engine after a 40-second rocket burn. The rocket plane reached an apogee of 105,000 feet (32,000 meters), which was about a third of the distance SpaceShipOne needed to climb for the Ansari X Prize. On descent, SpaceShipOne experienced Mach 0.9 while feathered.

The flight overall was a success. Burn duration increased signifi­cantly from the 15 seconds of the first rocket-powered flight.

“We also were able to demonstrate that we could maintain control during the pull-up, which was something on 11P that was sort of in question. Brian was fighting the vehicle trying to keep the wings level. So, overall, I think the only objective that we weren’t able to meet was the supersonic feather reentry” Siebold said.

Figure 8.6 shows Siebold flying SpaceShipOne back to Mojave.

At 28 feet (8.5 meters) in length, 8.8 feet (2.7 meters) in height, and 27 feet (8.2 meters) in width, which is the distance between the tips of SpaceShipOne’s horizontal stabilizers, the spacecraft is only slightly smaller than the Bell X-l. Table 4.1 shows a size comparison between SpaceShipOne, the X-l, the X-l5, and the Space Shuttle. Although the width of SpaceShipOne is slightly wider than the wingspan of the North American X-l5, it is about half the length of the X-l5. Every time SpaceShipOne flew, it had a different weight. The final spaceflight was
the heaviest, with an empty weight of 2,646 pounds (1,200 kilograms) and maximum weight of 7,937 pounds (3,600 kilograms).The weight advantage of SpaceShipOne was clear when compared to the gross weights of 12,250 pounds (5,557 kilograms) and 38,000 pounds (17,237 kilograms) for the X-l and X-l5, respectively.

During the test flight, the TONU displayed a readout from the energy altitude predictor during the boost phase. Developed by aerodynamicist Jim Tighe, it worked by making calculations based on factors like SpaceShipOne"s speed and thrust. The pilot used this to decide when to turn off the rocket engine because SpaceShipOne was roughly half the distance to apogee after rocket-engine shutdown. For the second half, it coasted the rest of the way up.

The pilot needed a way to ensure he didn’t run the rocket engine too long or too short. The initial powered flights relied on a timer, but using the energy altitude predictor yielded much better results. By looking at the readout of the energy altitude predictor, the pilot had a very good idea of the altitude SpaceShipOne would reach if the rocket engine shut down at that exact moment.

For example, the energy altitude predictor may have read 200,000 feet (60,960 meters), but in actuality, SpaceShipOne may have only been at an altitude of 80,000 feet (24,380 meters). So, if

SpaceShipOne shut down the rocket engine at that precise moment, it would coast to an apogee of about 200,000 feet (60,960 meters). This would be 128,000 feet (39,010 meters) short of the Ansari X Prize requirement. Therefore, the pilot wouldn’t have shut down the rock­et engine at this point, but he would have waited until the energy alti­tude predictor read at least 328,000 feet (100,000 meters).

Nearly one full year since flight testing began, SpaceShipOne was on the verge of making a spaceflight. One critical piece of infor­mation was missing, though. “The object of that flight was to do a supersonic feathered reentry,” Mike Melvill said. “We needed that data before we could go beyond that.” Figure 8.7 shows SpaceShipOne mated up to White Knight in preparation for the third powered flight.

Ten seconds after releasing from White Knight at 46,000 feet (14,020 meters), Melvill lit off the rocket engine. Figure 8.8 shows a dramatic rearward view of the rocket engine’s fiery plume and exhaust.

“During the boost after he reached the vertical part of the trajec­tory, the avionics display started flickering and then went blank,” Doug Shane said. “We all had good displays in the ground station. And Mike said, T looked out the window, and we were going pretty much straight up. So, I stayed with her.’ Gotta love a guy like Mike. Of course it came back on as soon as the motor shut down.”

The rocket engine burn duration was set by a timer. As Melvill looked out the windows to navigate, SpaceShipOne boosted to 150,000 feet (45,720 meters) and Mach 2.5, and then its rocket engine shut down. SpaceShipOne

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Flight Test Log Excerpt for 14P

Date: 13 May 2004

Flight Number Pilot/Flight Engineer

SpaceShipOne 14P Mike Melvill

White Knight 56L Brian Binnie/Matt Stinemetze

Objective: The third powered flight of SpaceShipOne. 55 seconds motor burn time. Handling qualities during boost and performance verification. Reaction control system use for reorientation to entry attitude. Supersonic feather stability and control.

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Fig. 8.7. The photograph shows SpaceShipOne being prepared for its third rocket-powered test flight. SpaceShipOne had made its very first test flight just about a year earlier. The main goal of this test flight was to evaluate the performance of the feather at supersonic speed. Mojave Aerospace Ventures LLC, photograph by David M. Moore

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Fig. 8.9. SpaceShipOne reached an apogee of 211,400 feet (64,430 meters), and the video camera in the tail boom recorded the feather in the extended position. While high above Los Angeles, SpaceShipOne was technically not in space, even though the curvature of Earth can be clearly seen. However, the curvature is somewhat exaggerated due to the auto focus lens used. Mojave Aerospace Ventures LLC, video capture provided courtesy of Discovery Channel and Vulcan Productions, Inc.

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reentry just as expected. It actually descended more smoothly at supersonic speeds than it did at subsonic speeds. Figure 8.9 shows SpaceShipOne above Earth, with Los Angeles and the California coast­line in the background.

Back on the ground, engineers traced the avionics malfunction to a dimmer, a small electrical component. And since the thermal protection data looked good, Scaled Composites felt that SpaceShipOne performed well enough to continue forward.

The construction of SpaceShipOne really began with the building of the fuselage. Without its wings and tail attached to the fuselage, SpaceShipOne looks like a stubby little rocket. Figure 4.5 shows the crew compartment in the forward section of the fuselage, the oxidizer tank in the middle section, the rounded pressure bulkhead that separates the crew compartment from the oxidizer tank, and the rocket engine in the aft section. The maximum outer diameter of the cylindrical

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Fig. 4.5. The cutaway drawing shows the crew positions in the cockpit of SpaceShipOne. A pressure bulkhead separates the crew from the rest of the rocket engine. The oxidizer tank mounted at the center of the fuselage has the rocket engine CTN (case/throat/nozzle) attached directly to it. Mojave Aerospace Ventures LLC, provided courtesy of Scaled Composites

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Fig. 4.6. A first step in the assembly was to build the carbon fiber/epoxy composite subassemblies that made up the fuselage. The subassemblies were bonded together, except for the nose cone, which was a detachable emergency escape hatch. Mojave Aerospace Ventures LLC, photograph by Scaled Composites

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fuselage is 60 inches (152 centimeters). It is a monocoque design, which means that the fuselage hull provides most of the structural support and load bearing for the spacecraft. However, the rocket engine obviously exerts a tremendous amount of force. So, the oxidizer tank is actually a very important structural member as well.

SpaceShipOne was put together much the same way a small plastic model airplane is put together. Beginning with a bunch of individual parts, they are assembled piece by piece. Woven layers, also called plies, of carbon fiber and epoxy were the primary materials used to make most of the lightweight composite parts of SpaceShipOne. These parts were used to build the fuselage, the wings, and the tail booms.

The whole process began by designing the parts using three – dimensional computer-aided design (CAD). The designs were then fed into an automated computer numerical control (CNC) machine to carefully shape the parts by whittling down foam blocks. Even though these foam parts precisely resembled the actual composite parts, they did not share the same strength, durability, resilience, and imperviousness to temperature. The foam parts were used to create molds that would then be used to create the actual composite parts to build SpaceShipOne.

After the molds were created, lay-up began. Here the composite material was built up layer by layer. Once enough material was added and the layers were to the proper thickness, the parts were vacuum-bagged and oven-cured. The vacuum-bagging process is basically what it sounds like. A part is covered with an airtight bag, which is evacuated by a pump. What this does is remove air from in between the layers and volatile compounds that are in the epoxy, which have become unwanted byproducts. The more thoroughly they are removed, the stronger the composite will be. The oven-curing enables the epoxy to properly set and achieve the desired properties. After the parts for SpaceShipOne were cured, assembly began.

Although the materials may have changed, the building technique was not unlike that used to build European sailplanes over the past forty or fifty years.

The primary structure of the fuselage is made up of only a few very large subassemblies. Figure 4.6 shows the nose cone and cabin section. The subassemblies have edges that fit to one another. They are then fastened with a jig and chemically bonded together. The subassemblies

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Fig. 4.7. Piece by piece, the exterior of SpaceShipOne took shape, like the building of a plastic model airplane. As construction proceeded, the wings were attached to the fuselage, and all the wiring, plumbing, linkages, and other components were installed inside. Mojave Aerospace Ventures LLC, photograph by David M. Moore

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Fig. 4.8. Because the cockpit was pressurized and SpaceShipOne faced extreme conditions in space, the walls of the fuselage provided double containment. In between the "shell within a shell" was an insulating layer that also improved the structural strength of the fuselage. Mojave Aerospace Ventures LLC, photograph by David M. Moore

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Fig. 4.9. This photograph shows the early stages of construction for the aft section of SpaceShipOne. A pressure bulkhead will be put in place at about the location of the opening in the fuselage to separate the oxidizer tank from the cockpit. Mojave Aerospace Ventures LLC, photograph by David M. Moore

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together form the inner hull or shell of SpaceShipOne. This inner shell is still not strong enough to support the spacecraft.

The nose cone is attached to the rest of the fuselage a little differ­ently. The nose cone is the primary escape hatch. Its edge is keyed so that it can lock and unlock from the fuselage with a quick little turn.

Figure 4.7 shows the cabin section that is forward of the pressure bulkhead in various stages of construction. Figure 4.8 shows the top of the cabin section after even more assembly, and figure 4.9 shows the aft section where the wings mount.

The next step in building the fuselage was to add a core of honey­comb material on top of the inner shell. Nomex, made by DuPont, was used as the honeycomb core. Not only is the honeycomb core lightweight, it offers high strength and it is heat and fire resistant. The honeycomb core, however, cannot serve as the outer layer. It needs further covering. So, panels called skins, manufactured using this composites process, were attached to the honeycomb core. The fuselage is a shell within a shell. The process of adding succes­sive layers creates what is known as a sandwich structure, as the fuselage hull is viewed in cross-section. Figure 4.10 shows an example of a sandwich structure. Another way to look at this is that the fuselage hull is a thick composite made up of several thin composites.

Honeycomb Sandwich Structure

After the assembly of the composite parts, SpaceShipOne resembled a spacecraft, but the job was far from over. “The hard part is stuffing all the systems in it and making sure that they are mounted properly,” Rutan said.

Initially the fuselage ended at the throat of the rocket-engine nozzle. During the flight tests, a fairing was added to extend the fuselage to the rim of the nozzle in order to improve aerodynamics.

Inside the cockpit, mixed between the circular windows, ports, door, and escape hatch, the pilot had all the instruments and controls he needed for all the various phases of flight. Figures 6.15 to 6.17 show views of the instruments and controls at the front of the cock­pit, to the left side of the pilot, and to the right side of the pilot, respectively. The instruments and controls are identified by their numbered callouts given from these figures.

The pilot used the control stick (33) and the rudder pedals (7 and 12) to fly subsonically and to maneuver using the RCS (15,38, and 41).

But for supersonic flight, trims (31,35, and 36) and backups (55) were used. The controls for the rocket engine included switches and a timer (34, 42, and 49—52).The feather was operated using valves and levers (1, 3, 39, 40, 43, and 44).

Cameras on the tail, on the fuselage, and in the cockpit (56) provid­ed video that was also an important source of data during flight testing. Mission Control used one of the cameras to monitor the feather and rocket engine in real-time. Two of the more unexpected things found in the cockpit were the ping-pong ball (8), which was used to provide a good visual during weightlessness, and the “Q-tip” (63), which the pilot used to wipe down excess moisture from the windows.

The controls for the ECS (13, 16, 17, and 64-69), battery (18—22), landing gear (45 and 53), radios (30), and other systems were also close at hand. However, important instruments like the air­speed indicator, Machmeter, altimeter, and energy altitude predictor were all displayed on the FDD of theTONU (11), and airspeed and altitude were also backed up on the Dynon (10).

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Fig. 6.11. One of the components of the Tier One navigation unit (TONU) was the flight director display (FDD). Like the glass cockpit of an airliner, the FDD showed many of the important instruments and readouts used by the pilot to fly SpaceShipOne. An initialize mode of the FDD is shown with SpaceShipOne lined up on Runway 30 of Mojave Airport. Mojave Aerospace Ventures LLC, provided courtesy of Scaled Composites

Fig. 6.12. As SpaceShipOne rockets to space, a boost mode is shown on the FDD. By closing together the red circle and green circle, the pilot achieved optimum trajectory. The pilot could also view the status of the rocket engine and oxidizer tank. Mojave Aerospace Ventures LLC, provided courtesy of Scaled Composites

Fig. 6.13. The FDD shows a reentry mode before SpaceShipOne returns to Earth’s atmosphere. The position of the feather, the operation of the reaction control system (RCS), and the condition of their pressurization sources are displayed. Mojave Aerospace Ventures LLC, provided courtesy of Scaled Composites

Fig. 6.14. After reentry and the feather is retracted, SpaceShipOne glides back to Mojave Airport. The test pilot used a glide mode on the FDD to help ensure SpaceShipOne reached the runway at correct position and speed. Mojave Aerospace Ventures LLC, provided courtesy of Scaled Composites

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Feather bottle low: A and В

Wing against stops and wing ТЕ locked

down indicators

Feather position

Launch separation controller

Spaceship “Armed” indicator

Mothership “Armed” indicator

Left rudder pedal

Ping-pong ball

Backup GPS navigation display Dynon backup altitude indicator FDD (flight director display) of theTONU (Tier One navigation unit)

Right rudder pedal Cabin altitude gauge

Landing pattern attitudes: normal and emergency (gear down)

RCS bottle pressure warning lights: A and В ECS bottle pressure warning lights: A and В Cabin pressure low warning light Battery voltage Bus tie A battery Selector switches В battery

Video transmit power TONU power

Trim circuit breakers: left stabilizer, right stabilizer, yaw, and backup trim Backup rate display

Stabilizer boost Damper heat

Circuit breaker panel indicators Communication/navigation panel: two radios, transponder, and intercom selector panel Pitch trim

Red button not used Pilot roll /pitch control stick Rocket motor fire Roll trim Yaw trim

FDD page control switches

RCS A enable switches Feather actuator Feather unlock RCS В enable switches Rocket motor arm

Feather lock pressure valves: A and В (the yellow feather lock valve also doubles as gear down emergency assist)

Feather actuator pressure valves: A and В

Landing gear handle

Nose cone release handle

Nitrous oxide dump valve

Backup dump (through main valve)

Rocket motor controller power: A and В buses Rocket motor controller reset

Motor armed indicator, main oxidizer valve commanded open indicator, and nitrogen pressure low indicator Rocket motor burn time controller Landing gear down indicators: left, nose, and right Lamp test

Backup trim (stabilizer) panel

Lipstick camera, forward cabin (focused on pilot)

Dry air feed line (vents between window panes to prevent fogging) GPS antenna (attached to window)

4-inch opening for fine cabin pressure relief valve

Fine cabin pressure relief valve (this is the storage location)

Emergency cabin pressure dump port (this is the storage location)

Oxygen control panel

“Q-tip”

Secondary cabin pressure bottle valve

Primary cabin pressure bottle valve

Pressure regulator and gauge

Defog control valve (for between window panes)

Cabin make-up air

Dehumidifier fans and CO2 scrubber fan switches 4-inch opening for emergency cabin pressure dump port

photo by Eric Long and Mark Avion, National Air and Space Museum, Smithsonian Institution

At 6:47 a. m. PST on June 21, 2004, White Knight lifted off from Mojave’s Runway 30, as shown in figure 8.10, to the cheers of twelve thousand spectators. Several days earlier, Mojave Airport officially became Mojave Air and Space Port after receiving its launch site operator license. It would have been another typical windy desert early morning with the Sun still not fully awake, except for a gangly looking airplane toting a stout little rocket plane on the first part of its journey to the hopeful reaches of space. Figure 8.11 shows the mated pair spiraling up to the launch altitude.

At an altitude of 47,000 feet (14,330 meters), White Knight could no longer guide SpaceShipOne any further and cut the rocket craft free to continue the quest on its own.

“You release the back pressure, and then the airplane starts to climb,” Mike Melvill said. “And at that point you must have the motor running. You unguard the switch that turns the elec – trons on to the ignition system, and you unguard the switch that fires it.

“A rocket motor doesn’t start off like a jet engine. It starts off as hard as it is ever going

Flight Test Log Excerpt for 15P

Date: 21 June 2004

Flight Number Pilot/Flight Engineer

SpaceShipOne 15P Mike Melvill

White Knight 60L Brian Binnie/Matt Stinemetze

Objective: First commercial astronaut flight by exceeding 100 kilometers (328,000 ft).

to be right there. The first time it lights, it is going as strong as it will ever be. In fact, it gets weaker as you go along. The initial kick on your back is very strong—more than 3 g’s. Your eyeballs go in at 3 g’s. And then you make about a 4-g turn. And you do that by just pulling back on the stick. In only 9 or 10 seconds, you are supersonic. You are supersonic about two-thirds of the way through that turn. And then you can’t use the stick anymore. You have to use the trim. So, that transition is something you have to learn in the simulator.”

But before completion of the pull-up, severe wind shear rolled SpaceShipOne to the left. As Melvill tried to regain wings level, SpaceShipOne rolled 95 degrees to the right and then 90 degrees to the left. He soon got control and had SpaceShipOne flying vertical, as in figure 8.12. But he ended up far off course.

A minute into the burn, as the oxidizer ran low in the tank, it began to transition from a liquid to a gas. The roar of the rocket engine made a drastic change. “As it starts sucking gas, it chugs,” Melvill explained. “And it goes boom, boom, boom, boom, boom, boom, boom, boom, boom, like that as it is going up. It really rattles your head. It doesn’t do that for too long. But it is disconcerting the first time it happens. I didn’t know what the heck that was all about.”

But the rocket engine wasn’t finished with its mischief. “The rubber that is on the inside of that thing has got ports in it, pie­shaped ports that run the whole length of the rubber fuel. So, as you are burning all the surfaces of the inside of each of these pie-shaped ports, they are coming together. You end up with a plus – sign—shaped piece of rubber that is very thin that runs the whole length of the machine. It will break off eventually and go out the back. That must have broken off and got sideways in the nozzle or something because it made a tremendous bang. It really rattled the airplane. I thought the whole tail had fallen off the airplane.”

To improve the airflow around the rocket engine for this flight, a fairing was added, which extended from the back of the fuselage over the sides of the nozzle. But heat from the rocket engine caused it to buckle. It was necessary to modify the design slightly for the next flight. It was unlikely the source of the sound Melvill heard.

Melvill seriously wondered if he’d be able to make it back, but Mission Control could see that the tail booms were just fine from the live video feed of the onboard camera. Unfortunately, Melvill didn’t have the capability to view this imagery. A failure of the primary pitch trim control, which Melvill needed while moving at supersonic speed, also occurred while the rocket engine blasted away. This only

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Fig. 8.10. As White Knight fired up its engines and began taxiing to the runway, it rounded the corner, around the control tower, to find a crowd of twelve thousand well-wishers lined up along the flightline. At 6:47 a. m. on June 21,2004, SpaceShipOne began its first journey into space. Tyson V. Rininger

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Fig. 8.12. Mike Melvill ignited the rocket engine, "turned the corner," and blasted nearly straight up. The rocket engine burned for 76 seconds and shut down at 180,000 feet (54,860 meters). After reaching a maximum speed of Mach 2.9, SpaceShipOne coasted the rest of the way up to space. Tyson V. Rininger

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minutes of weightlessness, he released two handfuls of M&Ms into the cockpit to float around in zero gravity. Mojave Aerospace Ventures LLC, video capture provided courtesy of Discovery Channel and Vulcan Productions, Inc.

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deepened his worry. However, he was able to get pitch trim control back by switching to the backup.

Melvill obviously had his hands full, and he wasn’t finished battling the rocket engine. He said, “The thrust is supposed to be right down the centerline. The nozzle is an ablative nozzle. It would burn away, and if it burns away a little bit on one side compared to the other side, you can end up with a yaw going on or a pitch. It burned like about a half a degree from being straight.

“Full rudder would only just deal with a half a degree from asym­metry in the thrust. I put the rudder on the floor, but it still went sideways across the ground. It is just amazing how quickly you go from one place to another if that happens.”

By this point, the good-luck horseshoe pin that Sally Melvill pinned to her husband’s flight suit just before the flight must have weighed five pounds.

“Poor trajectory control drew the airplane way far downrange. It spent an awful lot of energy going downrange rather than straight up where you want it to go,” Doug Shane said.

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seconds. The shadow of the feather on SpaceShipOne quickly moved position as SpaceShipOne’s orientation to the Sun rapidly changed. Mojave Aerospace Ventures LLC, screen captures provided courtesy of Discovery Channel and Vulcan Productions, Inc.

Boosting SpaceShipOne to Mach 2.9 (2,150 mile per hour or 3,460 kilometers per hour), the rocket engine cut off at 180,000 feet (54,860 meters) after firing for 76 seconds. SpaceShipOne coasted toward space, but concern rapidly grew whether or not it would reach the Ansari X Prize goal of 328,000 feet (100,000 meters).

Paul Allen could only watch and wait as the Mission Control staff tracked SpaceShipOne’s progress. “You’ve got a human being in a very small projectile that is going straight up at Mach 3,”Allen said, “and me pacing around behind the scenes going, ‘I just want Mike to get back on the ground safely.’ And you got an altimeter that just zips around as SpaceShipOne accelerates upward during the engine burn. And then it starts coasting. The altimeter is just wrapping itself around itself as fast
as it can, and then it starts slowing. You are wondering if SpaceShipOne is going to get high enough, and then it did but barely.”

Before reaching apogee, Melvill raised the feather in preparation for reentry. Gravity was calling SpaceShipOne back, and the spacecraft crept up slower and slower until it finally stopped. Measurements of the altitude were being taken from several different sources, and for a moment, there was nothing but uncertainty. SpaceShipOne did beat the mark by just a fraction, making it to 328,491 feet (100,124 meters), but substantially short of its targeted 360,000 feet (109,700 meters).

Despite the problems Melvill faced in the cockpit, he had a few moments to enjoy the 3.5 minutes of weightlessness. While in zero-g, he wanted to give a good demonstration of the weightless

experience. From a zipped pocket on the left arm of his flight suit, Melvill grabbed two handfuls of M&Ms, which he had bought on the way to the airport earlier that morning, and cast the multicolored candies out into the cockpit. Figure 8.13 shows Melvill in the cockpit with M&Ms floating about.

“The sky was jet black above, and it gets very light blue along the horizon. And the Earth is so beautiful, the colors of the Earth, the colors of the high desert, and along the coastline. And all that fog or low stratus that’s over L. A. looked exactly like snow. The glinting and the gleaming of the Sun on that low cloud looked to me exactly like snow,” recounted Melvill at a press conference after the spaceflight.

“And it was really an awesome sight. I mean, it was like nothing I’ve ever seen before. And it blew me away. It really did.”

Figure 8.14 shows video frames, at three-second intervals, of SpaceShipOne, with its feather extended, as it races through space over

Earth. In just a matter of seconds, it moves from one side of Earth to the other. Notice how the shadows change position as the orientation of SpaceShipOne rapidly changes with respect to the Sun. By the last frame, the Sun is behind the portside tail boom.

With the pitch trim control anomaly resolved, all Melvill had to do was let SpaceShipOne’s feather handle the “carefree” return into the atmosphere. SpaceShipOne hit 5.0 g’s while reaching Mach 2.9 during reentry.

“We started out over Boron and wound up directly over the top of the Palmdale VOR [VHF omnidirectional radio beacon]. That is a long way south, right out of the restricted area,” Melvill said. In fact, SpaceShipOne reentered over Palmdale Airport at 65,000 feet (19,810 meters), some 30 miles (48 kilometers) south of Mojave Air and Space Port.

“It was perfectly safe to be flying as an airplane or glider out there,” Doug Shane said.

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Fig. 8.17. In a surprise presentation, Patti Grace Smith, the FAA’s associate administrator for Commercial Space Transportation, awarded Mike Melvill the first-ever commercial astronaut wings. In flying SpaceShipOne above 328,000 feet (100,000 meters), Melvill satisfied the primary Tier One goal of getting to space. Now it was time to set the sights on the prize. Mojave Aerospace Ventures LLC, photograph by David M. Moore

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SpaceShipOne had better than a 60-mile (97-kilometer) glide range. It defeathered at 57,000 feet (17,370 meters) and started to glide back to Mojave.

“I got back to Mojave at 40,000 to 50,000 feet [12,190 to 15,240 meters]. I think we could make it from L. A., LAX probably, if we ended up really off course,” Melvill said.

Doug Shane would eventually get a call from the FAA for a meeting. Palmdale was the location of the air traffic control center responsible for all of Southern California. When Shane met with the FAA, an official enthusiastically said Scaled Composites could have all of LA Center’s airspace, no questions asked. All it would cost is one ride.

Figure 8.15 shows SpaceShipOne coming in for a perfect landing after a tumultuous spaceflight. As the spacecraft came to rest, completing only its fourth powered flight, Melvill, who had worked for Burt Rutan since 1978 and been Rutan’s first employee, became the first commercial pilot of a vehicle to and from space. The Scaled Composites team became the first nongovernment space program to
successfully send a human to space. And figure 8.16 shows Burt Rutan and Paul Allen congratulating Melvill on accomplishing a true milestone of flight. Also waiting to congratulate Melvill was Apollo astronaut Buzz Aldrin, who welcomed him to the club. Melvill became only the 433rd person in space since Cosmonaut Yuri Gagarin was the first to reach space in 1961. This works out to an average of ten new people to reach space per year since the very start of human spaceflight.

During a presentation shortly after the spaceflight, the FAA had a surprise for Melvill. “I am very pleased and honored to present, for the very first time, these FAA commercial astronaut wings to Mike Melvill in recognition of this tremendous achievement,” said Patricia “Patti” Grace Smith, associate administrator for the Office of Commercial Space Transportation.

Figure 8.17 shows Melvill with his astronaut wings standing next to Paul Allen and Patti Grace Smith. “I wasn’t expecting anything like that,” said Melvill. “It was really a thrill.”

The FAA now issues astronaut wings to any member of a crew, including passengers, on a spacecraft that exceeds an altitude of 50 miles (80.5 kilometers) during a spaceflight. The 50 miles (80.5 kilometers) was an arbitrary boundary traditionally used by the U. S. military. Internationally, the bar is higher, and the accepted boundary of space, which was used for the Ansari X Prize, is set by the scientifically based Karman Line of 100 kilometers (62.1 miles).

The primary goal of the Tier One space program set by Burt Rutan and Paul Allen had been achieved once SpaceShipOne returned safely to Mojave after reaching space. To that end, SpaceShipOne was optimized for altitude, not payload. Any unnecessary weight would have adverse­ly impacted performance. So, even though SpaceShipOne made it past the Ansari X Prize altitude goal, the passenger requirement wasn’t met.

Scaled Composites had much to think about now that the focus of Tier One was ready to change. Their first spaceflight had not gone entirely as planned, but the Ansari X Prize was now legitimately within reach. Yes, SpaceShipOne had made it to the altitude required by the Ansari X Prize—with only a few hundred feet to spare. Serious problems were encountered, however, and SpaceShipOne wasn’t even hauling the extra weight of a payload. It was necessary to review the spaceflight data and evaluate and repair the damage to SpaceShipOne. Corrective action was required to ensure these mishaps would not repeat and that the performance was improved to meet the demands of the Ansari X Prize.

The Ansari X Prize was to expire in half a year. Within that time, Scaled Composites had to fly two qualifying flights. Six months sounds like a lot of time, but margins of error for spaceflight are razor thin. For the challenges they faced—risking a test pilot’s life and possibly derailing the drive for private spaceflight for many years if something catastrophic occurred—six months were more like six weeks. The need for an additional powered flight before making an attempt at the Ansari X Prize had to be considered.