Pat Naughtin wrote:
2 Nasa designs builds and flies spacecraft using metric units for
measurement and then reports their successes or failures in old
pre-metric measures for the public.
Hi Pat,
That's not quite right. The Jet Propulsion Laboratory (which is part of
the California Institute of Technology, with contracts with NASA) works
mostly in metric units. Spacecraft components are specified in
millimeters and grams. The large majority of detailed drawings are in
millimeters typically on ISO size A1 sheets. Epoxies are weighed out in
grams and cured in ovens measured in degrees Celsius. Distances in the
solar system, including rover operations on Mars, are typically measured
in metric units. Most fasteners are metric sizes. Environmental
scientists measure atmospheric pressure in hPa, which I might add is a
very convenient unit for this purpose.
A variety of non-SI units are in common use at JPL, such as measuring
vacuum pressures in Torr, or astronomers measuring in parsecs and solar
masses.
NASA headquarters, on the other hand, and most of the manned space
program, are the opposite. I was at a meeting last week where several
senior managers and astronauts from NASA headquarters gave
presentations. Altitudes were specified in feet, speed in miles per
hour, pressures in PSI, etc. However, one speaker from NASA
headquarters used almost exclusively SI units. He is a Nobel laureate.
J.
