Re: Mars in two weeks?

From: Doug Jones (
Date: Sat Jan 06 2001 - 20:53:58 MST

Jeff Davis wrote:
> >Today mix technology offers the capability of reliably supporting
> >divers to depths beyond 2000 fsw and some believe the technology
> >may eventually be extended as deep as 5000 fsw.
> So, wrap a person in a carbon-fiber-reinforced cloth pressure vessel (to
> save weight) filled with water to a depth of one foot, and equipped with
> the appropriate scuba-like pressurized-gas breathing apparatus (or perhaps
> liquid-breathing apparatus), and you can likely expose them to an
> acceleration of 70 g's. This is based on the fact that at 70 g's, the
> hydrostatic pressure at the bottom of that one foot of water is the same as
> at a depth of 2300 feet of seawater.

Two errors here: hydrostatic head is proportional to acceleration, so
one foot of water at one gee would be like 70 feet of water at one gee
(I know whereof I speak, I was the keeper of the wheel dynamics
spreadsheet for Rotary Rocket). Secondly, while the bulk density of a
body is about 1, the lungs and other air filled spaces are <<1, and
would experience very strong buoyancy effects. At more than 25 gees
this would be likely to cause tearing of lung tissue. Also, the
hydrostatic pressure at the lowest point in the lungs would be far
higher than the gas pressure in the lungs leading to edema as liquids
leak through the walls of the alveoli. In tests, healthy subjects
immersed in water were able to take about ten gees for about fifteen
minutes before losing consciousness.

Doug Jones
Rocket Plumber, XCOR Aerospace

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