[amsat-bb] Re: The Moon is our Future
John B. Stephensen
kd6ozh at comcast.net
Fri Jul 3 13:48:09 PDT 2009
HEOs are illuminated 99% of the time and LEOs are illuminated 50% or more of the time with eclipses by the earth lasting only 45 minutes. Thermal inertia can keep the temperature from swinging too far in either direction. Since the satellite is in a vacuum, heat can only be radiated away as in a Dewar flask. On the moon, the eclipse lasts for 2 weeks so more cooling occurs. During the other 2 weeks, heat from the electronics and solar illumination must be radiated away. Every lander that I have seen has a few spindly legs so there won't be much heat conduction to the moon's surface.
However, I'm not an expert on thermal design. When I was designing a 70 cm receiver for AMSAT, others did the thermal analysis. Nothing behaves in space as it does on Earth as there is no convection cooling.
Building a prototype that works on Earth for project like this is only a few percent of the effort required. Treating it as a radio club project won't be effective as people need to sign up for a 5-year project. If your making an add-on to a NASA project you have to fit into their shedule, design to their specifications, produce the documentation that they need, travel to their test facilities and pass their tests. There are also legal requirements (ITAR) when working on space-related projects.
----- Original Message -----
To: John B. Stephensen
Cc: i8cvs ; Jack K. ; AMSAT-BB ; kg4zlb at gmail.com
Sent: Friday, July 03, 2009 19:57 UTC
Subject: Re: [amsat-bb] Re: The Moon is our Future
John B. Stephensen wrote:
A more meaningful appoach for an exercise like this is to start with DC
power input for the entire package. Receivers consume power and transmitters
(especially linear ones) are inefficient and the efficency goes down with
increasing frequency. On the moon, you also have to heat the electronics at
night to prevent failure.
What difference is there and why if there is any a difference of shadow cold on the moon, vs shadow in orbit? If anything i would think you would get some thermal radiation heating from the soil. wjereas in space you don't get this benefit.
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