This story was updated at 3:00 p.m. ET.
As the Fourth of July holiday weekend approaches, American families may be preparing for barbecues, picnics and days at the beach. But what about taking a trip high into the sky and experiencing what it would feel like to be in space, on the moon, or on Mars?
At least one family will be doing just that ? spending part of their Independence Day weightless. Sound farfetched? These types of "family vacations" may soon be more commonplace than you think.
This weekend, Alan Stern, Associate Vice President at the Southwest Research Institute (SwRI), is taking his wife and three children aboard Zero Gravity Corporation's G-Force One aircraft to experience what it feels like to be in an environment of true weightlessness.
Stern is leading a new project at SwRI that looks into the science applications of such aircraft and other next-generation suborbital space vehicles, and is taking part in the flight as part of that venture. [10 Private Spaceships Becoming Reality]
A weightless family affair
Stern is a veteran planetary scientist and former NASA science chief, and currently serves as the principal investigator for NASA's New Horizons probe headed for Pluto. He has flown on weightless flights several times and hopes that the Zero-G experience will give his family a small taste of what his own experiences were like.
"None of my kids or my wife is in the space world, and I thought this was something that I'd like to do for them, and do as a group," Stern told SPACE.com.
Currently, Zero-G flights depart from three primary locations: Las Vegas, Nev., Cape Canaveral, Fla., and Titusville, Fla. The company also occasionally schedules flights in other cities, including Seattle, Wash., Los Angeles, Calif., Washington, D.C. and New York.
Flights start at $4,950 per person, and while that figure is significantly less than seats on suborbital flights, it is still a hefty amount. Stern himself said that he would not normally be in a position to afford five tickets for the Zero-G experience, without the involvement of his research firm. But, as the industry expands, and as demand grows, the cost of these flights could go down.
The morning of the flight, all 36 passengers will register and meet for a safety briefing and 45-minute training session. They will receive instructions on safety issues and what to expect from the flight.
Stern and his family will depart from Dulles International Airport in Washington, D.C.
The flight plan, with a modified Boeing aircraft, is comprised of a series of 12-15 parabolic arcs, which mimic various states of microgravity. The skilled pilots perform these aerobatic maneuvers at different altitudes and at different angles in order to create the "pulls" of the various gravitational states.
"The first parabola is a Martian parabola, which will give the flyers a 35-second period of Martian gravity," Peter Diamandis, one of the company's three founders, told SPACE.com. "So, they'll go from 1 G (the amount of gravity measured on Earth) to 1/3 G."
The next two parabolas replicate lunar gravity (1/6 G), so the passengers can experience what it feels like to walk on the moon. Subsequently, the aircraft will execute a series of 12 parabolas at zero gravity. Passengers on board will be able to perform basic experiments and fun activities while weightless.
Zero-G was founded by Peter Diamandis, founder and chairman of the X Prize Foundation, veteran astronaut Byron Lichtenberg and NASA engineer Ray Cronise.
It took the trio 11 years to obtain Federal Aviation Administration (FAA) approval to fly what are known as commercial parabolic flights aboard their G-Force One aircraft ? a special, modified Boeing 727-200.
Zero-G flew its inaugural commercial flight in October 2004, solidifying its position in the extreme tourism industry as one of the only commercial enterprises that provides zero gravity flights that are available to the general public. In 2008, the Virginia-based firm Space Adventures ? which offers suborbital, orbital and lunar spaceflights ? purchased the company.
The flights have attracted some celebrity passengers as well, among them Martha Stewart and famed astrophysicist Stephen Hawking.
"Since we launched in 2004, we've flown over 6,000 people in Zero-G," Diamandis said. "It's wonderful to have it up and operating. The main challenge is having people know that it's real and available to them. A lot of people don't know it's an option that they have."
In addition, the company provides services for science research and development. In January 2008, NASA awarded a contract to Zero-G to provide commercial parabolic flights for scientific work. The company has, however, been met with some criticism over its services from a NASA oversight group.
In response to the NASA audit, Zero-G officials said the company has delivered a safe, reliable and cost-effective service to the space agency and "remains committed to continuing to improve its microgravity quality and looks forward to working with NASA to make the Microgravity Flight Services program a model for success in future partnerships with the commercial space industry."
Still, extreme tourism is a relatively new phenomenon. And while Zero-G's flights never leave Earth's orbit, the commercial enterprise is part of a larger paradigm of the expanding horizon of private-sector space efforts and commercial spaceflight.
Reaching for the stars
In a recent poll conducted by the Pew Research Center, 1,546 adults (18 years of age or older) living in the continental U.S. expressed how they envisioned life in the year 2050. The results of the survey revealed that 53 percent believe that over the course of the next 40 years, ordinary people will travel in space.
And, that is certainly within the realm of possibility, said Bretton Alexander, president of the Commercial Spaceflight Federation.
"We have ordinary, rich citizens flying in space now, but very few of them because they are very expensive," Alexander told SPACE.com. "For the ordinary person of more modest means, it might be a couple decades, but it certainly should be in the next 40 years. In my mind, it's not if it's going to happen, it's when."
In fact, Space Adventures and Zero Gravity, Corp., aren't alone in their space tourism endeavors. British billionaire Sir Richard Branson is planning to launch space tourists on suborbital spaceflights aboard a spacecraft called SpaceShipTwo ? the first of which is already built and undergoing shakedown tests.
Other private companies have plans for commercial spacecraft, rockets and ? in the case of hotelier Robert Bigelow's Bigelow Aerospace ? private space stations.
And when it happens, Stern believes that commercial spaceflight has the potential to be revolutionary.
"I hope that commercial spaceflight is the equivalent for human spaceflight as the PC revolution was for computing," Stern said. "Computing used to be big machines, and no one could afford them except for government, and computing was hard, rare and distant. Then, in the '90s, it became ubiquitous."
Spaceflight could experience the same transformation. But, the exact manner of that transformation is more difficult to predict.
"Tourism is the first application, but it's probably not the best or the last," Stern said. "When personal computers exploded on the scene, people thought of computers in the home as a way to do number crunching, keep files or play games. Nobody had an inkling of how we use the web today. I think spaceflight may go through the same thing."
Not just a joyride
Still, space tourism is only a part of commercial suborbital and orbital spaceflight. An equally valuable and potentially even more lucrative option is in providing flights for science and educative purposes.
Zero-G is already strongly committed to this burgeoning market, and currently has a partnership with Northrop Grumman as well as with NASA. With suborbital and orbital flights, in particular, these commercial operations could help fill any gaps created after NASA retires its space shuttle fleet.
"The business base actually goes beyond tourism," Alexander explained. "It's the research flights that will really open up the realm of space for more activities. And I think you'll see that same model with orbital space tourism."
One small step
And from there, the possibilities for growth are seemingly limitless.
"The capabilities may start with NASA, but then you have foreign governments, sovereign markets and other countries that didn't develop human spaceflight capabilities that will buy a ride," Alexander said. "Then you have research markets, pharmaceutical companies, manufacturing companies, so it's anybody's guess as to which of those markets are going to be drivers in how big they are."
Still, while this type of growth and expansion is not far from Stern's mind, the focus of this weekend's Zero-G flight for him is to provide an extraordinary experience for his family.
"I hope I open peoples' eyes to the possibilities that are out there," Stern said. "I think my kids ? 30 to 40 years from now, they'll probably look back, and their friends will be amazed that they got to fly in zero gravity so early."
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Visit SPACE.com on Friday, July 2 to get a first-hand account from the Stern family as it prepares for its Fourth of July zero gravity vacation.