Interesting discussion. For my $.02:
1. Consider a sun synchronous orbit to go along with the solar-only approach. No eclipse to worry about, though I'm not sure how many years such an orbit could be maintained before it slides one way or the other, e.g. what happened to AO-27 in reverse. So, you would still need to design for eclipse, just not operate there.
2. You don't get max power out of the cells all the time - it depends on sun angle. And solar cells degrade over time, and they fail too. Having a battery in the loop can be a very good thing, e.g. what happened to PCSAT. Perhaps a compromise, use some of those new mega capacitors? I understand that they are not space-rated yet, but perhaps "we" could help in that regard...
3. Not to burst your bubble, but I believe one of the cubesats recently launched uses a no-battery design.
4. We know AO-40's power system has failed, or at least is not capable of powering the bird. I haven't heard that we know cause vs effect; another "urp" of from the rocket system, or leaking nasty stuff all over the wires could be the cause. The battery itself could be just fine. But, I agree that there's a lot of mass and volume that could be used for other things on a small bird.
Greg KO6TH
----Original Message Follows---- From: "Margaret Leber" [email protected] To: [email protected] Subject: [amsat-bb] Re: Future radical satellite designs Date: Sun, 8 Jul 2007 10:05:41 -0400
On 7/8/07, Patrick McGrane [email protected] wrote:
Hello maggie- I hate it when people snip or take things out of context. Go back to the original entire email to absorb the reason. thanks,
patrick
I did read the whole thing.
The challenges to amateur secondary payloads on commercial or military spacecraft have been discussed here at length in the past. *My* comment was that a standalone bird *designed* without battery-powered transmitters might be an interesting approach.
As it stands now we have several birds on-orbit designed with larger battery systems (that have subsequently failed) that come up in various random control system states when they come out of eclipse. These birds only transmit when in sunlight anyway; what if we designed one that way on purpose? Now *that's* a "radical satellite design".
The payload weight that would have gone to bigger batteries to power transmitters during eclipse could be used for other equipment. A smaller (more reliable? certainly simpler and cheaper) auxiliary battery system could keep the control systems alive during eclipse. A lot of work is being done with ultra-low-power processor chips for mobile applications these days.
Imagine if AO-40 had used this approach (admittedly not at all in-line with the elaborate something-for-everyone AO-40 design philosophy); it might still be usable. As it is, when the complex power system failed, we lost the whole bird. And the only hope of recovering it is the outside chance that it might fail *again*.
-- 73 de Maggie K3XS Editor, Phil-Mont Mobile Radio Club Blurb - http://www.phil-mont.org Elecraft K2 #1641 -- AOPA 925383 -- ARRL 39280 _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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