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[AZ-Observing] Re: Mercury

From: "Workman, Brian (AZ76)" <brian.workman@xxxxxxxxxxxxx>
To: "'az-observing@xxxxxxxxxxxxx'" <az-observing@xxxxxxxxxxxxx>
Date: Mon, 26 Jul 2004 07:28:54 -0700

 
> CAPE CANAVERAL, Fla. (AP) - NASA is about to embark on its hottest 
> mission ever, to Mercury. The Messenger spacecraft, to be launched 
> next week, will be blasted by up to 700-degree heat as it orbits the 
> tiny planet closest to the sun - so close that it would be as though 
> 11 suns were beating down on Earth.

OK this is a bit pedantic, but one of my pet peeves is seeing junk like this
in an official press release. It should say "700-degree _temperatures_".
Heat is energy and as such is measured in calories or Joules, and even that
is not very useful. The thermal engineers who designed and analyzed the
Messenger spacecraft undoubtedly dealt in "heat flow" (which is really
power)in units of Watts (or btu/hr but nobody uses btu/hr). 

The 700 degree number is virtually meaningless and is an artifact of the
design of the heat shield. The instruments themselves will be maintained
under 100 degrees I'm sure. The very same spacecraft could have been
designed so that the heat shield was at 100 degrees or 1000 degrees, it is
just a matter of how that heat is routed and dissipated to protect the
instruments.

The folks at NASA who write this stuff ought to know better. Writing like
this misleads the public and fosters erroneous concepts.

Sorry for ranting but I feel much better now.
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Follow-Ups:

[AZ-Observing] Re: Mercury
From: Jeff Hopkins

[AZ-Observing] Re: Mercury

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