[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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