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Article #150Re: nasa-celebrates-successful-mars-landing
From: George Herold
Date: Wed, 08 Aug 2012 12:16
Date: Wed, 08 Aug 2012 12:16
53 lines
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4183 bytes
On Aug 7, 7:57 pm, Jon Kirwan <j...@infinitefactors.org> wrote: > On Wed, 08 Aug 2012 09:42:05 +1000, Adrian Jansen > > > > > > <adr...@qq.vv.net> wrote: > >On 8/8/2012 7:04 AM, Jon Kirwan wrote: > > >>>> Which reminds me of another thing. How do they convect the > >>>> internally generated heat away. I recall hearing about > >>>> multiple power systems, operating around 32V at near 2A. More > >>>> than one. This power must be convected/conducted away -- no > >>>> way they want to radiate it. I wonder if they push it > >>>> (costing more heat) towards a vane or arm and drag it around > >>>> on the surface to get rid of it? > > >>> The atmosphere won't help much. > > >>> Why not? Thermal conductivity of air is pretty much constant till you > >>> get below 1 Torr or so. Wiki says the mean pressure on mars is about > >>> 0.1 psi, which is ~5 torr. > > >> Good point. > > >In earth atmosphere, I understand most heat above around 300K ( 'room' > >temp ) is carried by radiation and convection. Conduction is a minor part. > > >No idea what convection is like at 5 torr in a CO2 atmosphere, but I > >suspect its a lot lower. > > Then that begs the question, again. Perhaps George spoke too > soon. Sure, I'm always putting my foot in my mouth! (I must enjoy the taste of toe jam :^) On Earth once the temp difference is above a few degrees I think convection is the biggest source of heat transfer. But I have no idea of how that changes with pressure. Maybe some day I can build a convectron pressure gauge. The patent on that must be expired. George H. > > I'll go dig. I'm ignorant and don't like the feeling. > > Jon- Hide quoted text - > > - Show quoted text -
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From: George Herold <gherold@teachspin.com>
Newsgroups: sci.electronics.design,aus.electronics,comp.arch.embedded
Subject: Re: nasa-celebrates-successful-mars-landing
Date: Wed, 8 Aug 2012 05:16:57 -0700 (PDT)
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