[time-nuts] Smithsonian Time/Nav Exhibit
Jim Lux
jimlux at earthlink.net
Mon Jul 1 08:56:31 EDT 2013
I had a chance to go through the Time and Navigation exhibit at the
National Air and Space Museum last week. From a "time" standpoint,
there's probably not much there that time-nuts don't know already, but
it's kind of cool to see cleaned up examples of equipment from days gone
by. (there's an old cesium beam from NIST on display, and a Symmetricom
cesium turned on and counting, but also a lot of old GPS stuff... lots
of Rb and Cs for space)
Quite a lot of the exhibit space was devoted to the problem of air
navigation, which, now that I've seen the exhibit, I can understand what
challenge it was. Over centuries, folks had figured out how to navigate
on ships and on land, but those are inherently slow moving, so you can
do things like take multiple sextant sights and reduce them.
But planes move fast, so you don't have as much time to do it. It took
real guts to be the navigator in the little cockpit out front of the
plane, taking sights with your body out in the wind. And the poor
fellow who was sucked out of a plane when taking sights standing on his
seat and the astrodome blew out.
It was interesting to see how many different schemes were used for
(mostly radio based) nav in airplanes over a fairly short time. Low
Frequency DF, A/N Ranges, VOR, LORAN, etc. I didn't see Omega.
They have an inertial nav unit there from a sub, but not much
explanation of how inertial nav works.
They talk about the DSN (and actually have a 4 bay rack of the old
time/frequency distribution gear on display), but not much discussion
on exactly how we do navigation for deep space.
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