Re: the apex of a trajectory versus free fall

On Fri, 27 Apr 2007 10:00:39 -0500, Andy Resnick
<andy.resnick@xxxxxxxxxxx> wrote:

I am one of the lucky ones to have flown on the Vomit Comet, and here's
how it goes:

You are lucky. I appreciate your descriptio;n. I'm glad I asked my
question.

And I'm glad to hear my misconception was normal. At least something
about me is normal.

Each day consists of about 40-50 parabolic arcs, and the total flight
lasts for about 2-3 hours. IIRC, it was 10 arcs in one direction, the
plane turns around, 10 arcs back, the plane turns around again... etc.

Each arc lasts about 3 minutes- a 2+ minute climb which is experienced
as a 2-g acceleration followed by 30 seconds of reduced gravity. The
climb is when most people actually vomit- moving your head confuses your
brain. Sometimes the turn is combined with a climb.

When the apex of the climb is approached, the engines are cut back and
the plane goes nose-down. "reduced gravity" begins here, and the pilot
has three basic options, decided on prior to the flight. The plane can
go for 0-g, 0.16-g (lunar) or 0.3-g (Martian). There's an accelerometer
and readout, and the pilot controls the rate of downward fall (the
engines are cut back, not off) to keep the desired acceleration within
bounds. This period lasts for about 30 seconds, at which point the
engines are brought back up, and the plane begins to climb. Total
vertical distance covered is about 20k feet. My personal experience is
that "lunars" are more disorienting than free-fall.

The misconception that 0-g is acheived for part of the climb and through
the apex is normal, but incorrect due to air drag on the plane. The
transition from 0-g to 2-g (and back) occurs within a second or so, so
safety is a concern- people like to goof around in free fall, but one
should not be upside-down, over electrical equipment, or otherwise
misoriented at the end of the dive. Apparently, the russians have a
version of the Super Guppy for cosmonaut training, and it's a problem if
someone shoots 'up' toward the top of the cabin, a good 30 feet above
the floor, and can't get back down in time.


If you are inclined to email me
for some reason, remove NOPSAM :-)
.

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