NOT FOR PUBLICATION
PLEASE PASS TO SCIENCE EDITOR
Dear Science Editor,
You are undoubtedly aware that the latest shuttle mission (STS-100)
carried up a manipulator arm for the International Space Station (ISS).
Despite the impression that AP wires and NASA PAO releases might leave
in your mind, this arm was designed and built in SI ("metric") units.
The URL that follows is for a NASA web page
http://spaceflight.nasa.gov/station/assembly/elements/mss/subsystems.html
and the web pages provided by the builder (MDRobotics) corroborate the
units of measurement actually used.
I, for one, would appreciate anything you can do to counter the
misimpression people might receive from the "English" materials you're
using in publishing AP wires. If you'll check the page above, you'll
see that the arm is 17.6 m long and carries a manipulator that is 3.5 m
long. The power values given are in watts, which are SI ("metric"), of
course. The loads shown are in newtons (N); 1 N is the force needed to
lift and hold a small apple of mass 100 g (0.100 kg). So the tip load
is essentially the force that would be needed to lift a large man on
Earth's surface.
Further down, the mass handling capability is listed as 116,000 kg
which NASA obligingly converts (to too many digits) as 255,736 pounds.
The conversion of kilograms to metric tons (tonnes) is easy of course
since 1 metric ton equals 1000 kg; it is 116 metric tons in this case.
You should note that the NASA page uses the term "weight" in lieu of
"mass", which is rather colloquial and more appropriate for commerce
than for technical matters. Also, the operation speeds shown are of
course in SI ("metric") but the formatting is improper. They should be:
Unloaded: 37 cm/s (or "centimeters per second" -- no / symbol)
Station Assembly - 2 cm/s [This is a NASA typo; it should be 6 cm/s]
EVA Support - 15 cm/s
Orbiter - 1.2 cm/s
I sincerely hope that the Post and Courier can exert some local
influence on what is published in its pages to avoid publishing
misleading materials. Let's honor our Canadian neighbors by not dumbing
down the units of measurement they (and the NASA specifications) used.
More importantly, let's make sure that our readers and their children
know that modern science, engineering, and commerce are done in the
International System of Units (SI), also known as "the modern metric
system". Charlestonians are smart enough to understand those units.
sincerely,
James R. Frysinger
--
James R. Frysinger University/College of Charleston
10 Captiva Row Dept. of Physics and Astronomy
Charleston, SC 29407 66 George Street
843.225.0805 Charleston, SC 29424
http://www.cofc.edu/~frysingj [EMAIL PROTECTED]
Cert. Adv. Metrication Specialist 843.953.7644
