Alan Boyle reports on the inaugural services of Zero Gravity Corporation, an entity that’s been attempting to offer weightless flights to the general public in the US for over a decade. It was held up by FAA regulations.

In full disclosure, I attempted to start a business like this about that long ago, but couldn’t raise the money to get started. We did offer service for a brief time in a much smaller aircraft, but never managed to expand beyond that, though we had plans to do exactly what Zero G has done, using cargo 727s that could be quickly converted on a daily basis using pallets. But had I known what travails Peter Diamandis and company would have to go through, I probably wouldn’t have even made the attempt, and I’m probably lucky that I didn’t have to go through it at all.

I want to take exception to a quote that Alan has in his piece, however:

Cosmic Log reader Ayanna Bryan provides a cautionary note:

“As someone who has gone on parabolic flight several times for research purposes, let me assure you that most people do indeed get sick. And it’s not just nausea. There are other forms of motion sickness that are very unpleasant and sometimes disturbing.

Some people remain sick for several hours after the two-hour flight. Unless medicated (which has its trade-offs: comfort in-flight for discomfort 6 hours later), the normal human vestibular system is easily affected by sharp changes in gravitational level. Some fliers still get sick after taking the Scopolamine/Dexedrine medication. Some people even ‘freak out,’ for lack of a better term, once they experience the effects of increased and then decreased gravity.

I hope fair warning is given to paying customers, and I hope the preflight training is good enough to meet Air Force standards. Otherwise someone could get seriously hurt.”

As someone who has done extensive research in this business, let me point out that this comment is completely spurious. Research flights have a specific goal in mind–research. Comfort of participants is a distant second to that goal. They don’t call NASA’s airplane the “Vomit Comet” for nothing, but there’s no reason to think that such unpleasant side effects can’t be avoided.

For one thing, people who don’t have to perform research can use much more effective anti-nauseants than scope-dex. For another, since the purpose of a NASA research flight is to get as much research in as possible, the plane basically flies, and gets in as many parabolas as possible, until it’s either low on fuel, or until everyone on board has green gills, and no more productive activity is possible. That won’t be the case on these flights, in which the goal is to provide an enjoyable and exciting customer experience. There will be far fewer parabolas, and they will be developed gradually, with low-gravity maneuvers preceding the weightless ones.

If Zero G makes a significant number of people sick, it will be because they’re doing something wrong, not because it’s an intrinsic feature (or in this case, bug…) of the experience. Sadly, this is just the type of misinformation that makes it so difficult to raise money for space tourism ventures.

[Monday morning update]

Clark Lindsey has similar thoughts, and provides a little tutorial on weightlessness, but it requires one bit of clarification.

The “zero g” effect produced by these flights, just like in orbit, is an apparent one. Earth’s gravitational pull doesn’t change and remains as strong as ever. (It decreases as 1/(distance squared) as you move away from the planet.)

Over the top of the parabola, both you and the plane are falling together. You are no longer being pressed against the floor of the plane, which is usually keeping you at a fixed distance from the earth via the lift of its wings. (In the valleys of the trajectory, the plane is having to decelerate and reverse you from the speed gained during the falling portion of the parabola. So you feel higher g force in that case.)

In orbit, the same principle applies except you and the vehicle are falling around the earth because your rocket produced enough horizontal speed to keep you from hitting the ground as you fall. That is, the curve of your falling trajectory matches the curve of the earth.

This last sentence is true only for a circular orbit–it’s not true in general. For suborbit, or elliptical (or hyperbolic trajectories), there’s no relationship between the trajectory and the earth’s curvature. But this is not required for free fall.

Essentially, what you feel when you feel “gravity” is the force of some other object (such as your chair if sitting, or the floor if standing or walking) supporting your weight against it. In a free-fall trajectory, the airplane is basically “flying around you,” following the path that you would take if you’d simply been launched from a cannon (in vacuum), so it never contacts you and can thus not give you any feeling of weight by supporting you against the force.

One more subtle point. What we call a parabola in so-called parabolic flight isn’t a true parabola, mathematically, precisely because of the curvature of the earth. If we were using a flat earth model, in which gravity were a constant, (as Galileo assumed when he first started doing calculations for his pioneering work in ballistics), then it would be a parabola. In reality, it’s a small section of a non-circular ellipse (that is, a suborbit would be an orbit with an extremely low perigee, if the earth didn’t get in the way). However, over the distances involved in subsonic aircraft, flat earth is a reasonable approximation, and the difference between the trajectory and a true parabola are inconsequential, and probably unmeasurable.

[Update at noon eastern]

Here’s a space.com article that describes the (overly onerous, in my opinion) FAA approval process for the flights.

Incidentally, I don’t buy the notion that Zero G can really patent the idea of using cargo airplanes during the day for this that fly at night–it seems almost as silly to me as Amazon’s single-click system. I doubt if that would stand up in court very long.

Whether it does or not, though it looks like the real barrier to entry to this is the FAA certification process (though now that there’s a precedent for the Special Type Certificate it may be easier for a competitor to come in than it was for Zero G, should the market prove robust enough to support one). Space enthusiast Peter Diamandis should welcome this, even if Zero G investor and executive Peter Diamandis doesn’t…