True, but not a deal killer in my mind. I was investigating utility of a relatively less SWaP solution to add to the on-board options for backup power from a catastrophic event.

 

Samudra N3RDX

 

From: KENT BRITAIN <[email protected]>
Sent: Thursday, December 10, 2020 1:45 AM
To: John Brier <[email protected]>; Samudra Haque [TTLLC] <[email protected]>
Cc: Steve Greene <[email protected]>; AMSAT BB <[email protected]>
Subject: Re: [AMSAT-BB] Re: How to determine why Fox satellite batteries failed before projected 5 year lifetime

 

I have worked on several energy harvesting projects, but it's that 140-150 dB Path Loss

from the Earth to LEO that is quite the hurdle.   One solar cell the size of a postage stamp

would give you many orders of magnitude more power.    Kent WA5VJB/G8EMY

 

 

On Wednesday, December 9, 2020, 9:56:12 PM CST, Samudra Haque [TTLLC] <[email protected]> wrote:

 

 

Thanks John, appreciate it.

 

I’ve been thinking that it should be almost mandatory to put up RF power receivers (converters) on all small space vehicles that have little to no redundancy in EPS, battery and solar plants. Too many missions have suffered because of battery/solar issues. It’s not like there are no transmitters beaming carriers to a space vehicle/smallsat for command purposes – and it’s not like there are no big antennas being used to do that. So why not tap some of excess power (energy) of the carrier that would be tracking the bird in flight when in view of the ground stations? It’s amazing what the newest gen of power converters and harvesting systems can do. I’m looking at the calcs right now. Superb.

 

From: John Brier <[email protected]>
Sent: Wednesday, December 9, 2020 10:50 PM
To: Samudra Haque [TTLLC] <[email protected]>
Cc: Steve Greene <[email protected]>; AMSAT BB <[email protected]>
Subject: Re: [AMSAT-BB] Re: How to determine why Fox satellite batteries failed before projected 5 year lifetime

 

QSL

 

On Wed, Dec 9, 2020, 22:49 Samudra Haque [TTLLC] <[email protected]> wrote:

I wonder if this response will get out, if anyone sees this please QSL.

I wanted to shift my e-mail address and move to my personal one, and requested delisting several times and was confirmed (several times) and … still get emails from AMSAT-BB.


Well, the discussion on batteries/life/mission expectations is obviously interesting to me. But where the batteries ever characterized for discharge / charge in (LEO) cold and (LEO) hot temperature ranges?

 

I’m well into modeling wireless power beaming systems from ground to space currently for scenarios where batteries are kaput, from LEO to deep space. If anyone is interested?

 

Samudra N3RDX

 

From: John Brier <[email protected]>
Sent: Wednesday, December 9, 2020 10:34 PM
To: Steve Greene <[email protected]>
Cc: AMSAT BB <[email protected]>
Subject: [AMSAT-BB] Re: How to determine why Fox satellite batteries failed before projected 5 year lifetime

 

Between Jerry's post and yours I have learned a lot and have more to think about. Thanks so much.

 

Just a couple thoughts:

 

Just thinking out loud here... Depth of discharge means how far into the discharge cycle you let the cells go right? Considering memory, if you only let them go to a specific percentage aren't you guaranteeing memory will be created? I guess if you never plan to go beyond a specific point it doesn't matter, and extends the life apparently. Interesting.

 

The other difference between AO-27 and SO-50 and the Fox birds is that the Fox birds had a continuous carrier once the transponder was activated, for up to a minute even without use, IIRC. So that could cause a deeper depth of discharge.

 

I also would love to know more about SO-50. It seems like a mystery. It just works, it never is commanded into a different mode, and it's been going for almost 18 years apparently. Amazing. When that one goes, it will be even more disappointing.

 

Again, thank you very much Jerry and Steve for your informative posts.

 

73, John Brier KG4AKV

 

On Wed, Dec 9, 2020 at 7:55 PM Steve Greene <[email protected]> wrote:

Jerry  -thanks for that detailed explanation. 

Disclaimer: The information contained in this communication may be privileged, and is intended for the use of the above named addressee(s). If you are not the intended recipient(s), do not use or rely upon it. Instead, please inform the sender and then delete it. Thank you.

 

Disclaimer: The information contained in this communication may be privileged, and is intended for the use of the above named addressee(s). If you are not the intended recipient(s), do not use or rely upon it. Instead, please inform the sender and then delete it. Thank you.

 

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