[meteorite-list] MIND BLOWING

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Sat, 14 Jul 2007 19:28:59 -0500
Message-ID: <009401c7c677$244a85a0$ac2ee146_at_ATARIENGINE>

Hi, Pete, Michael, List,

    The first thing I thought of was... Mars, just like
you. But the air thereabouts is awful thin. I guess
it's calculator time.
    The density (or pressure) of the Mars atmosphere
is only about 1/100 of the Earth's. How a wind "feels"
to an object in its path is dependent on the density of
the wind (the number of molecules per unit volume)
and the velocity of the wind. The momentum of the
wind is the density (really the mass of the molecules in
the wind added together) times the velocity of the wind.
So, an object on Mars will encounter wind with 1/100
the momentum of wind on the Earth traveling at the
same velocity. That means the wind on Mars has to be
traveling a 100 times faster than the wind on Earth to
have the same momentum.
    However, the kinetic energy content of the wind is
dependent on the velocity of the wind squared (or
E = (M x V x V)/2, so the wind on Mars only has
to travel about 10 times as fast to make up for the
difference in density.
    Mars atmosphere is mostly CO2, a heavy molecule.
It's not the same as the Earth's atmosphere. The details
are the density of the atmosphere at the surface of Mars
is only 81 times smaller than Earth's. Therefore, to "feel"
the force of a breeze on Mars of the same force as on Earth,
we would require 9 times the wind velocity (square root
of 81). For example, to "feel" a light breeze of about 10
miles/hr on Earth, would require "hurricane speed" winds on
Mars of 90 miles/hr.
    It's obvious from the video that these walkers require
as much wind as they can get, here on Earth, or they wouldn't
be walking on a windy beaches! Here's another complication.
The gravity on Mars is only 38% of Earth's, so it only takes
38% of the force to lift a "foot" up. The walker only "weighs"
38% of what it would on Earth. Maybe a "Mars Walker" would
only require a wind about 5.5 times faster than an Earth wind
to get the same motive force. [The "mass" is the same but
the force of Martian gravity only resists its motion 38% as
much as Earth's gravity does. However, the inertia is the
same on both planets, something to remember when you
go for a walk on Mars.]
    The gravity may be less, but a Mars Walker would need
to carry a lot of extra mass: solar panels for the cameras,
radios, experiments, and other instruments, and weigh means
more force and energy is needed. My guess is that a Mars
Walker is a difficult and marginal thing. What I need now is
a long term weather report on Martian wind speeds... from
all over the planet.


Sterling K. Webb
------------------------------------------------------------------------------
----- Original Message -----
From: "Pete Pete" <rsvp321 at hotmail.com>
To: <mlblood at cox.net>; <meteorite-list at meteoritecentral.com>
Sent: Saturday, July 14, 2007 5:32 PM
Subject: Re: [meteorite-list] MIND BLOWING


Very cool, Mike, and I see a relevance to the List - lightweight, wind
powered...NASA should drop dozens of these all over Mars for surveillance of
any type!

Cheers,
Pete


From: Michael L Blood <mlblood at cox.net>
To: Meteorite List <meteorite-list at meteoritecentral.com>
Subject: Re: [meteorite-list] MIND BLOWING
Date: Sat, 14 Jul 2007 13:48:35 -0700

Dear meteorite friends,
         This is so mind blowing I am sending it to the meteorite
list even though it is not related to meteorites. I encourage
you to check it out!
         My apologies to anyone offended by a non-meteorite
related post - but before you start kicking and screaming,
please check this out:

http://www.glumbert.com/media/kineticsculpture

         Best wishes, Michael
Received on Sat 14 Jul 2007 08:28:59 PM PDT