Associate Editor

T minus 1 hr 20 min: After a week in quarantine and the short ride to the launch tower, and after scratching your initials in the frost on a nearby 18-in. liquid-oxygen supply line, you are seated horizontally and strapped in. The crew compartment hatch is closed. No turning back now, you think, feeling fear and exhilaration and hearing only the creaks of the launch vehicle as you go through the preflight onboard checklists. The pressure suit becomes uncomfortable and you start to ache, a mixture of your sitting position and your nervous anticipation.

T minus 2 min 0 sec (T-02M00S): You close your visor. Only your rapid breathing pierces the quiet.

T-00M21S: The gimbal test initiates, where shuttle main-engine nozzles are swiveled in a final check. You feel the vibrations and know that launch is only seconds away.

T-00M6.6S: Main-engine startup. All three main engines power up, the vibrations increase, and you hear the rumble.

T-00M00S: Liftoff! Solid rocket boosters add their thrust, pinning you down in your seat with a hard jerk. Everything pops and booms around you. The simulators couldn't do this, you think. Should I be hearing all these noises?

You see the ice sparkles - breaking off of the thrusters - outside the window.

T+8M00S: The escape fuel is spent, and the loud roar and quakes are replaced by a hum and a gentle vibration. Outside the window, blue turns to black and the earth reveals itself as a shimmering ball of infinite colors. No picture can do this justice.

To experience the thrill of space travel, you can pursue a university technical degree, be accepted into the U.S. astronaut program, train for years, and possibly get a seat on a shuttle mission. Or, you can do the next best thing and plunk down $52 at Walt Disney World Resort to ride its newest Epcot attraction: Mission: SPACE.

Mission: SPACE - conceived, designed, and developed by Walt Disney Imagineering - is set several decades into the future at the International Space Training Center. "Astronauts in training" board capsules that hang from the arms of four independent centrifuges. Sophisticated hardware and software, high-fidelity visuals and audio, and special lighting, perfectly synchronized with capsule motions, simulate what it feels like to launch into deep space. "It's an amazing experience," says Senior Show Producer Bob Zalk, Walt Disney Imagineering. "In fact, it's out of this world. Guests will certainly say this ride is unlike any other experience they have had before."

And indeed, Mission: SPACE is a first-of-its-kind: Its sophisticated human-centrifuge technology, though used extensively to train pilots and astronauts, is a first for theme parks. "The centrifuges are designed to create a sense of sustained gs such as you would feel on a Space Shuttle launch," explains Imagineer Edward Fritz, technical director. The systems also have planetary, pitch, and roll motion. "Add to this special effects and a visual system that gives riders the perception of depth, and we've created an immersive environment that makes people feel as if they are actually in outer space."

Living the high life

There's no denying the folks at Disney are brilliant storytellers. Mission: SPACE is a doozy. Astronaut wannabes begin their journey in the Space Simulation lab where they get a taste of what it's like living in zero gravity: The lab houses a 35-ft rotating gravity wheel. Also on display is a 25-ft graphic of the Mission: SPACE futuristic X-2 rocket illustrating how advanced rocket-propulsion technology works, and an Apollo-era lunar rover, courtesy of the Smithsonian's National Air and Space Museum.

Guests are then assigned a role to play during the mission as commander, pilot, navigator, or engineer. Next comes the preflight corridor. Once loaded and buckled in, riders blast off. A Capsule Communicator (Capcom) guides astronauts through their flight, assigning tasks to assist in a safe landing on Mars. At the end of the mission, guests head to the Advanced Training Lab, home to various interactive games and displays.

More fact than fiction

What transpires took years to perfect. Some of the biggest design challenges, says Fritz, came as early as 1998. "We had this great idea for a space attraction but it was tough to turn it into hard numbers that engineers could work from," he explains. "To get there we went to NASA. We rode on some of their centrifuges and installed makeshift audio and video equipment to see how it would all come together. But we still had to sit down and turn hundreds of sheets of blank paper into numbers and requirements engineers could use as a basis of design. We made some calculations, mocked some things up, and nailed it."

Because the ride is in Epcot, its story had to be based in fact, not science fiction. Enter NASA. Disney Imagineers worked with more than 25 space experts there and from its Jet Propulsion Laboratory, including five astronauts. "Anytime we had a question with any of the science behind the attraction, we would call NASA," says Imagineer Sue Bryan, senior show producer. "They've given us an enormous amount of support, even providing data from satellites and orbiting spacecraft, including Mars Odyssey and Global Surveyor. So what Mars guests see out of the cockpit windows includes real landforms created from height data and photographic imagery."

Disney, being in the storytelling business, likes ride mechanics to maintain a certain mystery. It keeps the details close to its vest (particularly before the ride opens, which is the case as this is written), but Imagineers did provide some hints. For example, one ride system, they say, has more computing power than a Space Shuttle. Each system has two primary computers on board controlling all ride and show functions. Add to that 30 motion-control computers which control capsule altitude during the flight, and a show-control computer which operates the interactive functions within each capsule. The futuristic X-2 rocket design is based on advanced propulsion technology which could conceivably blast astronauts into space, says Disney.

And of course, the ride owes a lot to sophisticated human-centrifuge technology.

Vision and motion unite

One company well versed on the topic of human centrifuges is Environmental Tectonics Corp. (ETC), Southampton, Pa. (www.etcusa.com). Experts in the field of aviation physiology, the company is a major supplier of aeronautical equipment (including human centrifuges able to produce up to 25 gs) to the militaries of the U.S. and many other nations.

In 1999 the company branched out to include the entertainment field, forming Entertainment Technology Corp. (EnTCo). At The Ride Works, as it's called, engineers design, develop, and manufacture motion-based simulators which provide sustained gs and 360° motion in as many as four axes. ETC's advanced technology and extensive knowledge of how the human body responds to motion provides a glimpse into what makes Mission: SPACE tick.

Amusement-ride technology depends on matching up and sustaining visual and motion cues to keep riders from losing lunch. Traditional "fun machines" such as roller coasters have a limited linear range of motion. They jerk riders one way and back the other, pulling maybe 3.5 gs but only for a fraction of a second. These conflicting inputs to the visual and vestibular (inner-ear) systems are what cause motion sickness. "We live in a six-degree-of-freedom environment and there's little effort in most entertainment rides to correlate g vectors," says William Mitchell, president, CEO, and chairman of ETC. "The human body really doesn't perceive its position other than from its visual system and kinestatic pressure, such as the pressure on the feet. We do, however, perceive acceleration, so in ride systems using the correct acceleration vector reduces motion sickness and gives riders proper perception."

The g vectors of the human body are Gz (up and down the body), Gx (into and out of the chest), and Gy (through the shoulders). Imagine driving a race car: On the straightaways you feel a heavy positive or negative Gx component when accelerating or decelerating. The Gy component hits in the turns and the Gz component comes in the corners.

In entertainment centrifuge technology, the objective is to control the g vectors created by the centrifuge. "By controlling the acceleration and deceleration of the central hub, and pitching and rolling the gondolas that carry passengers, we can control vectors and thus the sensations they feel," explains EnTCo's Dave Mitchell, director of sales and marketing. "For example, to create a free-fall feeling while the rider is in a seated position, we point forces upward on the body. To create a feeling of acceleration, such as an accelerating automobile, forces are pointed directly into the center of the chest."

Creating safe and controlled simulated environments is ETC's forte. That's obvious from its latest ride platform: A multiple-arm centrifuge called Big Mac. Big Mac can accelerate riders to as much as 2.6 gs sustained, with 360° continuous pitch and roll motion. All manner of visual and audio bells and whistles inside the gondolas put riders in the drivers' seats of any number of adventures. To ensure high-motion fidelity, ETC uses state-of-the-art design tools including FEA, kinematic and dynamic modeling, 3D modeling, and critical-system safety-hazard analysis tools. In one Big Mac ride system, gondolas hang in their pitch axes and are attached to individual roll yokes, which mount via a bearing system to a central arm structure with roll drives, says ETC. A gear reducer and electric motor drive the arm structure. Pitch and roll drives make it possible to direct the g vector in ±X, ±Y, and ±Z directions. All these mechanics and high-tech visuals combine to create truly realistic simulated experiences that may be the leading edge of an entirely new generation of thrill rides.


Where flight simulation and thrill rides meet

The transition from pilot-training simulators to thrill-ride systems is not a huge leap, but demands careful consideration in many areas, especially safety. That's according to William Mitchell, president, CEO, and chairman of Environmental Tectonics Corp., Southampton, Pa.

The biggest difference in designing systems for flight-crew simulation versus those for the entertainment industry involves the magnitude of the experience, he says. "The entertainment world, due to the demographics of who would be in the ride, limits forces to about 3 gs, whereas a pilot can be exposed to forces as high as 9 gs in simulation," he says. "That would be life-threatening for the normal human."

In the virtual-reality ride market, ETC's situational-awareness efforts are geared to prevent motion sickness or spatial disorientation. "Here we try to eliminate those experiences while in the flight-simulation market we may be trying to specifically create them as part of a training program," says Mitchell. "Today's high-performance military aircraft (the parent company contracts with air forces around the world for pilot training) can easily pull 9 gs at rates exceeding 10 gs/sec. A pilot not properly equipped and trained would quickly lose control of the aircraft and would not survive."

Such pilot training includes plenty of elements that have found their way into the entertainment systems produced by ETC.

"The pilot trainee sits in a cockpit or gondola environment and the fidelity of that cockpit, or how well we replicate the experience to be achieved, is a great factor in transporting the individual from one reality to another," says Mitchell. "We focus on the visuals, the out-the-window visual system and instrument-display system, how well they replicate the real world."

Details to be tackled here include a satisfactory update rate of the visual system or pixel count/frame. Proper texturing of that leads to a higher fidelity experience. The next step is combining visuals with the correct force inputs, which provide physiological stresses to the occupant or pilot. The key is to make that integration seamless, which the simulation market traditionally has failed to do, according to Mitchell.

"Simulation technology used to employ motion cueing, providing simulator occupants with a cue that tells them they are moving in one direction, and then supporting that cue with the visual scene," he explains. "But the technology could not sustain that motion and instead occupants would feel unnatural jerks, and the system just washed it out. When that happens, the body subconsciously perceives the fact that the experience is not real, leading to motion sickness. ETC's goal has been in correcting that mistake by providing sustained video and motion inputs."