The flight will begin from NASA’s Kennedy Space Center in Florida. The journey consists of parabolic trajectories (kinda like rollercoaster rides up and down high peaks and low valleys) at around 9,100 meters (30,000 feet, or about 5.7 miles) above the Earth’s surface.

Each parabola-shaped ride will go up to a peak height and then drop in free-fall so that passengers such as Hawking will experience weightlessness (similar to astronauts in orbit about the Earth) for about twenty seconds. At that time, passengers will be able to float about the padded interior of the aircraft. (In fact, NASA astronauts experience weightlessness in similar flights before going out into space.)

The operational base of Zero Gravity Corporation (often called ZERO-G) is Dania Beach, Florida (south of Fort Lauderdale) and its headquarters is Santa Monica, California. The company operates commercial weightless flights that are similar to NASA flights with its KC-135 airplane—humorously and often times accurately [as from this writer's personal experience] referred to as the “Vomit Comet”.

A parabola begins when the aircraft begins to climb at about 7,300 meters (24,000 feet) above the Earth's surface at an angle of about 45 degrees. The airplane reaches its maximum altitude of about 9,750 meters (32,000 feet), at which time the pilot points the airplane’s nose down toward the Earth at an angle of about 30 degrees.

Around 15 parabolas will be provided in the cost of the flight, usually of three types. These types include parabolas that simulate the gravity on Mars (about 38% of the gravity felt on the Earth), on the Moon (about 17% of Earth’s gravity), and weightlessness (about 0% of Earth’s gravity—like in orbit about the Earth). Passengers pay approximately $3,500 for a ticket to ride. Most flights last about two hours.

This flight for Hawking holds special interest for disabled persons because it will be the first for a quadriplegic (a person paralyzed from the neck down). Hawking has lost nearly all neuromuscular control to his body because of the degenerative motor neuron disease called Amyotrophic Lateral Sclerosis (ALS). He is restricted to a motorized wheelchair that contains a computer with a voice synthesizer, which allows him to speak.

Please note that when passengers such as Hawking are weightless (experience zero-gravity) they are ‘actually’ falling toward the Earth (like skydivers) so they do not resist the force of gravity as much as when one is standing  on the Earth’s surface. Astronauts weightless in orbit about the Earth are also falling toward the Earth, but their forward motion, such as in the Space Shuttle, is so great that they continue to go around the Earth rather than fall to its surface.

The home Web page of Zero Gravity Corporation is: http://www.gozerog.com/home_full1.aspx.

The home Web page of Professor Steven Hawking is: http://www.hawking.org.uk/home/hindex.html.

The Web page of How Stuff Works explains weightlessness in more detail: http://science.howstuffworks.com/weightlessness.htm.

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