Mach, Knots Indicated Airspeed (kias), and Feet: weird aeronautical units?
Last I checked, those were standard on both sides of the ocean, unless
you're in Russia.

Indicated airspeed and mach ratios are the two most important factors to
consider! The glider needs to reach a specific Indicated Airspeed in order
to produce adequate lift, which in the extremely thin Martian air would be
an extremely fast True Airspeed. The minimum Indicated Airspeed needed is
open for debate, but it certainly is significantly faster than 40 kias, due
to slow-speed-buffet limits in the extremely thin air. We are also limited
by the Mach Ratio, which for a conventional high-aspect ratio glider is
quite low, nowhere close to 0.85 Mach-limited swept-wing subsonic jets. So,
without asking a Boeing-McDonnell-Douglas Engineer to help me with the math,
I think it's pretty safe to say that the minimum speed required of our PW-5
would be significantly faster than the maximum allowable speed; Hence, our
glider no worky-worky.

-Chris




"Robert Ehrlich" wrote in message
...

Sorry, your calculations with weird units don't have an obvious meaning to
my metric educated mind. I never thought of indicated airspeed, only tried
to
evaluate the ratio of true airspeeds on Mars and the earth to ensure
similar
(e.g. best L/D) flight conditions. My idea was that the speed of sound,
while
affected by the change in conditions, should not be affected by a very
important
factor. The factors involved are absolute temperature, molecular weight of
the
gas(es) and gamma (Cp/Cv). Gamma depends only on the atomicity. While I
don't
know exactly what are the components of the martian atmosphere, I guess it
is
not methane or CO2, but rather diatomic gases with molecular weigth near
O2 and
N2 as found on the earth. As all this is under a square root, changes must
be
huge to become significative, same thing for temperature. Halving the
temperature
on earth only decreases the speed of sound by a factor 0.7, and this is
pretty
cold.

So 10 times the gliding speed on the earth is about the speed of sound on
the earth,
if the reduction of gravity and wing loading gives a factor that overrides
the change in the speed of sound, subsonic soaring may be possible on
Mars.