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Re:Re:Re: Re: The hard questions..



On Fri, 20 Feb 2004 13:19:16 -0800
Phil Karn <karn@ka9q.net> wrote:
> This sounds appealing, but the difficulty is that our modern
> spacecraft are now so totally dependent on their onboard computers
> that any power interruption (such as by an eclipse with open-circuited
> batteries) knocks the spacecraft out of commission until its computer
> can be manually reloaded and restarted from the ground. If an eclipse
> happens on every orbit, as it often does, it becomes rather
> impractical to keep the spacecraft going with a few volunteer command
> stations.
> 
> Perhaps a new computer design that carries flight software in a 
> non-volatile memory and can boot and run automatically after a
> power-on reset would be the way to go. As I understand it, this is how
> the Mars Rovers operate so as to not have to run their PowerPC
> computers all night. They have ultra-low-power clocks that run
> continuously that start the computers at the appropriate times, plus
> they can start when sunlight appears on the solar panels.
> 
> The transponder power amplifiers would also have to be carefully 
> designed to avoid pulling the bus voltage low even for a moment, as
> that would cause a computer reset.

One thing I've been wondering is how well do the large value "backup"
capacitor work in space.  I was just thinking possibly using one to
power either the processor or at least the configuration ram during the
eclipse.

Another option would be to power the 5V processor bus off both batteries
through diodes where the voltage drop wouldn't matter as much and power
the transmitters using relays.
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