Scott Kellogg writes:
> The maximum listed speed for a man wearing a grav belt is 300km/hr.
> Why? Drag? Skydivers travel MUCH faster than that.
Nope, actually they travel a lot slower. The accepted terminal
velocity for a falling human body is around 120 MPH (200 kph).
I asked a friend of mine who dives (sky *and* SCUBA) and he says
that with normal jump suits (which are deliberately loose and floppy
to retard rate of descent) the average velocity for a jumper is more
like 90 MPH (the idea being that you get to stay in the air longer
if you fall slower).
> Case: I forget when it was done, but sometime back in the 50's-60's they
> were experimenting with high altitude ejection. I remember hearing a guy
> talk about setting the world record for the highest parachute jump on some
> documentary or other. He said that on the way down he actually went
> supersonic. When he got into the thicker atmosphere, he slowed way, way
> down before he pulled the chute.
The worlds record for the highest parachute jump was set on August
16th, 1960, but Capt. Joseph Kittinger Jr. USAF, when he said, "Lord,
take care of me now." and stepped out of a pressurized, high-altitude
balloon suspended gondola at an altitude of 102,800 ft. over White
Sands Missile Range near Alamogordo, New Mexico. The total length of
the jump, from bail-out to touchdown was 13 minutes and 45 seconds.
Kittinger freefell from 102,800 ft. down to 96,000 ft., at which point
he deployed a 6 ft. stabilization 'chute to keep from tumbling. The
atmosphere is so thin at that altitude that he continued to accelerate
for another 6,000 ft. before hitting a peak velocity of 614 MPH, which
is 90 percent the speed of sound at that altitude (90,000 ft.), and
is 83 percent the speed of sound at sea level. At 17,500 ft., 4 minutes
and 38 seconds after he began the jump, he deployed his main canopy and
floated to the ground.
To the best of my knowledge, this record stands today. No skydiver in
history has broken the sound barrier in freefall.
Next, James Johannesson writes (w.r.t. Scott Kellogg's comments on
imaging assassination targets from orbit):
> A great idea, but wouldn't an atmosphere cause problems with this sort
> of stuff (i.e. shots from orbits for assassination)?? But does that mean
> then that the range of a Laser Rifle is increased on Vaccuum worlds since
> it doesn't have any resistance because of atmosphere (what about dense
> worlds??) Any comments from the Physics majors out there on the mechanics
> of laser/bullet fire in other than normal (i.e. earth-like conditions??)
Atmosphere *does* screw up long laser shots, as evidenced by the results
of the SDI MIRCL (Midrange InfraRed Chemical Laser) tests in the early 80's.
Even at a range of < 20 miles, there was significant beam diffusion and
energy loss. In addition to airborne crud (dust, pollen, bugs, ultra-
light pilots, etc.) which block and scatter the beam, there is the problem
of the clear atmosphere itself. Under the stimulation of a high-energy
laser, the air in the path of the beam heats to an energized plasma state,
which then presents the same sort of problems as airborne particles. The
main problem is defocusing of the beam (the assumption being that a large
enough power source can pump a laser beam of such high energy that any
energy loss in transit will still leave enough punch to toast the target
at the other end). Current ground-based laser research is attempting to
overcome this beam diffusion by using computer-controlled variable geometry
mirrors. As the beam is diffused in the atmosphere, that beam scatter is
automatically measured by the computer and the mirror's geometry is modified
to correct for the diffusion. Success so far has been only moderate,
according to de-classified documents on the research. (FYI, Tom Clancy
covers this subject a fair amount, in layman's terms, in his novel
_A_Cardinal_in_the_Kremlin_.)
> I mean, when you think of it, when your using a shotgun in a dense
> atmosphere, wouldn't the range be shorter??? Is this thought of in the
> game mechanics? I don't think so..........
It probably does affect thh range , but unless that atmosphere has the
consistency of Campbell's Cream of Potato soup, and you are firing at
a target at long range++, it shouldn't make any difference.
Later,
- Mark C.