Doc Searls and a few other acolytes of flight were guests of Intel for a ride on the Zero-G flight experience. Here’s Doc, presumably praying to Saint Spew, the patron Saint of Puke, before the flight:
I never knew a military aviator who enjoyed zero or negative G forces. In fact, most engines’ oil pumps are not specified for more than 1 negative G. Not that it kept us from trying zero Gs in a C-130, while otherwise bored, flying from one place in Vietnam to a similar-looking other place. In those halcyon days, each aircraft dashboard sported a quaint plexiglass map holder, about 6″ by 9″. Meant to hold a Jeppesen approach plate book, it was one half of a terrific Zero-G indicator. The other half was a pencil. I kid you not.
The trick was to drop the pencil into the map holder and start the one maneuver that’s obvious after a few moments’ reflection. In order to attain the maximum weightless time, you want to spend as much time as possible pushing the controls forward into the zero G range. You could do this starting from a high altitude and just push the controls forward, but you’ll get more weightless time if you start at a medium altitude at high speed and then pull the aircraft up at a couple of positive Gs to set up for the negative G phase. From the nose-up position, the pilot pushes the controls forward until the Zero G state is reached. That’s where the pencil in its lucite cage came in.
I’m sure the folks at Zero-G Corp have more sophisticated instruments, but none more direct or accurate; or more analogue. But some subtlety is required. Surely unlike the Zero G 727’s instruments, as the pencil rises from the bottom of the holder, one must gently release a bit of the forward pressure, since it obviously required a slightly negative G force to move the pencil off the bottom of the map holder. I describe this distinction so my pilot friends don’t point out my oversights.
That’s it. Just keep the pencil in the center of the map holder as long as possible. In the Zero Gravity Corp’s Boeing 727, that lasts about 30 seconds. In the C-130, we probably pushed the limits a little further, though we did not have the range of airspeed available to their 727. Here’s how the profile looks using their 727:
It’s really a matter of the airspeed and altitude available to you. In an SR-71, I’ll bet you could get close to a minute of weightlessness, by starting at 60,000 feet and Mach 2.5, arcing up to 85,000 feet or so and pulling it out when pointed straight down at about 35,000 feet, which is where most real men would be staining their tutu.
So that’s it. 2/3 of the people “lose it”, literally, on the Vomit Comet. And that’s why I never want to experience Zero Gs again. Few smart people do it twice.