Space Forum / Space Flight / January 2006

Sounds like she might be thinking about one of those vertical
wind-tunnels skydivers use to perfect their freefall technique.

 > We were discussing "Space Cadets" in work today, and someone asked
if they

If you figure out how to do that, you'll have Mr. Gates cleaning your
bathroom.  Anti-gravity is (at least with our current knowledge of
physics) impossible.  We may discover otherwise eventually, but at least
for now your "anti-gravity chamber" is just made up.  Unless you fly on
one of the parabolic zero-G flights...

In sci.space.tech Paul O'Neill <news-x@lazyeyedpsycho.cjb.dot.net.retro.com> wrote:

You can put someone in a tower, and drop them in a sealed chamber,
and get some time weightless.
But...
The worlds tallest building is ~500m high.
To fall that far, from rest takes about 10 seconds.

But you'd have to cut a couple of seconds off that, for decelleration
time, to avoid excessive employee turnover.
So, 8 seconds, or maybe 16 seconds, if you start at the bottom, accellerate
up, freefall, then come back down.

But in all, not a whole lot of time.

There is no known technology to negate gravity.  In fact, gravity
is so little understood that nobody really knows how it works.

What you can do is set up situations where you counteract gravity.
You can do that in the airplane flying parabolas, in a swimming pool
where you make the student weight exactly what they displace in
water, or in things like parachute towers where the wind updraft
counterbalances your fall.

There was a segment on American Hotrod where Boyd took the crew
out to the drop tower at Perris Airport in the LA area, and let
each of the crew members take a turn parachuting.

-john-

Yes, a drop tower would "squish" a person at the bottom -- how severely
would depend on how rapid the deceleration was.  Come to think of it,
there's a new amusement ride that does pretty much the same thing.

I'd bet she is either confusing vacuum with microgravity, thinking of
broadcasts from orbit, or is one of the UFO-believers who thinks the moon
landing was faked.  Occam's razor says antigravity would be far more
impressive than landing on the moon.

/kenw

Ken Wallewein
K&M Systems Integration
Phone (403)274-7848
Fax   (403)275-4535
kenw@kmsi.net
www.kmsi.net

in a vertical free fall, they can be stopped gradually in the same
number of seconds, and over the same distance, by subjecting them to
2g.  So they don't have to be smashed at the bottom.  But you would
need a very tall tower indeed to get more than a few seconds of free
fall.  Doing it in my head (so I may be wrong) I get about 18000 meters
for a 60 sec free fall.  Plus 18K more for braking.

I think she saw footage of the vomit comet that was poorly explained by
the announcer.

You lost; they exist all right.

Take a sturdy enough box, crawl inside, and have some other people lift
it, then drop it. Alternatively, have them push it over the edge of a
table. From the time the box lost contact with the helpers' hands / the
table till it hits the floor, it will have the same acceleration as that
of gravity, and inside there will be no percieveble gravity. There's the
anti gravity chamber.... Thinking about it, it's probably safer just to
jump from that table, but then there's no chamber.

The drop towers are higher variants of the same, with the added feature
of a brake, so you won't get killed at the bottom. Airplanes can fly in
trajectories that effectively cancel gravity (perception) for a minute
or so (again, it's cheaper to pull out before the plane hits the
ground). Spaceships in orbit can follow such a trajectory until the
passenger has been convinced and just wants to go home.

Soren

You win.  There is no such thing.

No, because drop tower canisters are generally much too small for a
person.  How much force is squishing the contents at the bottom depends
on how it's designed.

Of course many amusement parks have drop towers designed for people, but
these are open, not giant vacuum chambers like scientific drop towers.  
And you don't float about in them, you're strapped into a chair.

That (or the commercial equivalent -- check out
<http://www.nogravity.com/>) is the only way of simulating microgravity
without actually being in orbit.

Henry's guess about skydiving training chambers is a good possibility,
though.  Of course you're not actually weightless in those; you're just
held up by a very strong wind, as long as you maintain your body in the
correct position.

Best,
- Joe

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NASA's Glenn Research Center (formerly Lewis Research Center) in
Cleveland, Ohio has a drop tower for simulating 2.2 seconds of zero-G.
This is just a large vertical tunnel that has the air pumped out of it
in which a test capsule is dropped.  It's actually quite a bit more
sophisticated than that but the point is that the zero-G is simulated
by an object in free fall.  More info at:
http://exploration.grc.nasa.gov/drop2/

Martin