I hope for this to be a purely engineering based discussion that could shed some light on this question.
Please only respond from an engineering perspective in this thread.
Data:
According to the "AMSAT Fox-1 Systems Engineering Documentation" the satellites were expected to last at least five years. [1]
For each satellite, before there were any issues with the batteries, they were able to power the transponder continuously without going into safe mode. However, once battery issues were encountered, the transponder would turn off unexpectedly while the satellite went into safe mode. Using that cutoff my back of the hand calculations show the following [2]:
AO-92: batteries lasted 35% of their expected lifetime AO-91: batteries lasted 60% of their expected lifetime. AO-85: batteries lasted 87% of their expected lifetime.
I know the batteries used were Nicad. I know they were matched. I believe the issue so far has been that one cell in the set has failed such that the minimum voltage required to run the transponder is not met. Is that last point correct?
So that is the data that I am currently aware of.
I think the next data to procure would be to understand what information was used to project a five year lifetime. Then you could look at the available data about the real satellites (from telemetry for example) to find out if there are any discrepancies that would explain the reduced lifetime.
From my scanning of the "AMSAT Fox-1 Systems Engineering Documentation" I didn't see the battery chemistry mentioned.
However, in addition to the "AMSAT Fox-1 Systems Engineering Documentation" there is a lot of information in the Fox engineering material from past Symposium Proceedings. These are available as PDFs to AMSAT members.
Do people agree that the next steps would be to understand what information was used to project a lifetime of five years?
If so, can anyone tell me, or can anyone go through the past Symposium Proceedings, and lay out what information was used to project a five year lifetime?
If not, what are the better next steps in understanding the reduced battery lifetime?
73, John Brier KG4AKV
1) 2.3 Reliability Requirements 2.3.1 The satellite shall be designed for a minimum 5-year, on-orbit lifetime. " https://www.amsat.org/wordpress/wp-content/uploads/2018/06/AMSAT-Fox-Documen...
2) AO-92 was launched/commissioned in January 2018. AO-92 has had battery issues since this fall such that it can't be used. AO-91 was launched/commissioned in November 2017 and now it too seems to be having the same battery issues. AO-85 was launched October 2015, declared EOM February 2020.
Hi John,
My gut feeling is that it'll be related to the battery chemistry (assuming your statement is correct that the batteries used are NiCd batteries) - not fully discharging a NiCd before recharging it again creates a 'memory effect' (https://en.wikipedia.org/wiki/Memory_effect) of sorts in the battery, and over time reduces the reasonable use life of the battery significantly. I have memories of my father meticulously discharging all his NiCd batteries in a proper discharge unit in order to avoid this, when we used to use them for our radio control toys etc when I was a child.
In contrast, when he picked up some "Rechargeable Alkalines" as he called them, he made the point of explaining to my brother and I that actually these were designed to be recharged after only partial discharge, and quite the opposite was true - one should avoid fully discharging these batteries in order to avoid reducing their lifespan (see https://en.wikipedia.org/wiki/Rechargeable_alkaline_battery). It would seem that this would be a better chemistry type to use for something like a satellite, where whilst in sunlight the batteries can be floated/topped up, than a chemistry such as NiCd where recharging before they hit their minimum threshold causes issues, however the number of cycles required to bring them back to full condition from a deep discharge could also be problematic.
I'm aware we aren't talking about run-of-the-mill AA cells, and are likely talking about some kind of custom size/shape cells instead, but it would seem to me that the chemistry is the cause of the 'early' failures, especially when coupled with the discharge/recharge cycles that the batteries would normally experience when moving between eclipse and sunlight. Of course this doesn't account for any clever software managing the charge cycle, and instead assumes that sunlight = charging and eclipse = discharging, so there's likely to be a lot more at stake than just the chemistry. Still food for thought, though, assuming the initial premise of 'they use NiCd cells' is correct.
73, John (M5ET)
-----Original Message----- From: John Brier [email protected] Sent: 07 December 2020 19:28 To: AMSAT BB [email protected] Subject: [AMSAT-BB] How to determine why Fox satellite batteries failed before projected 5 year lifetime
I hope for this to be a purely engineering based discussion that could shed some light on this question.
Please only respond from an engineering perspective in this thread.
Data:
According to the "AMSAT Fox-1 Systems Engineering Documentation" the satellites were expected to last at least five years. [1]
For each satellite, before there were any issues with the batteries, they were able to power the transponder continuously without going into safe mode. However, once battery issues were encountered, the transponder would turn off unexpectedly while the satellite went into safe mode. Using that cutoff my back of the hand calculations show the following [2]:
AO-92: batteries lasted 35% of their expected lifetime AO-91: batteries lasted 60% of their expected lifetime. AO-85: batteries lasted 87% of their expected lifetime.
I know the batteries used were Nicad. I know they were matched. I believe the issue so far has been that one cell in the set has failed such that the minimum voltage required to run the transponder is not met. Is that last point correct?
So that is the data that I am currently aware of.
I think the next data to procure would be to understand what information was used to project a five year lifetime. Then you could look at the available data about the real satellites (from telemetry for example) to find out if there are any discrepancies that would explain the reduced lifetime.
From my scanning of the "AMSAT Fox-1 Systems Engineering Documentation" I didn't see the battery chemistry mentioned.
However, in addition to the "AMSAT Fox-1 Systems Engineering Documentation" there is a lot of information in the Fox engineering material from past Symposium Proceedings. These are available as PDFs to AMSAT members.
Do people agree that the next steps would be to understand what information was used to project a lifetime of five years?
If so, can anyone tell me, or can anyone go through the past Symposium Proceedings, and lay out what information was used to project a five year lifetime?
If not, what are the better next steps in understanding the reduced battery lifetime?
73, John Brier KG4AKV
1) 2.3 Reliability Requirements 2.3.1 The satellite shall be designed for a minimum 5-year, on-orbit lifetime. "
https://www.amsat.org/wordpress/wp-content/uploads/2018/06/AMSAT-Fox-Documen tation.pdf
2) AO-92 was launched/commissioned in January 2018. AO-92 has had battery issues since this fall such that it can't be used. AO-91 was launched/commissioned in November 2017 and now it too seems to be having the same battery issues. AO-85 was launched October 2015, declared EOM February 2020. ----------------------------------------------- AMSAT-BB mailing list -- [email protected] View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to [email protected] Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org
Each Fox-1 satellite uses 6 Sanyo KR-1400AE NiCd A cells.
Obviously we all hoped that the batteries would last a lot longer. As discussed during the Symposium, the likely cause of battery failure is a higher than planned depth of discharge. Note that AO-92's batteries failed more quickly than AO-91. Since AO-92's evening passes were generally between 9 and 11 pm, AO-92 saw lots of use while in ecilpse. Contrast that to AO-91, where the evening passes were generally after midnight, so it saw less use while in eclipse.
I'm not sure there's much to be learned from the experience with these batteries as NiCd battery technology is now certainly obsolete and will not be used in future AMSAT satellites. AMSAT's GOLF series of satellites will use lithium ion batteries. More information about the progress of GOLF, including the GOLF-TEE status paper from the 2020 Symposium Proceedings, can be found at https://www.amsat.org/greater-orbit-larger-footprint-an-introduction-to-the-...
73,
Paul, N8HM
On Mon, Dec 7, 2020 at 2:41 PM John [email protected] wrote:
Hi John,
My gut feeling is that it'll be related to the battery chemistry (assuming your statement is correct that the batteries used are NiCd batteries) - not fully discharging a NiCd before recharging it again creates a 'memory effect' (https://en.wikipedia.org/wiki/Memory_effect) of sorts in the battery, and over time reduces the reasonable use life of the battery significantly. I have memories of my father meticulously discharging all his NiCd batteries in a proper discharge unit in order to avoid this, when we used to use them for our radio control toys etc when I was a child.
In contrast, when he picked up some "Rechargeable Alkalines" as he called them, he made the point of explaining to my brother and I that actually these were designed to be recharged after only partial discharge, and quite the opposite was true - one should avoid fully discharging these batteries in order to avoid reducing their lifespan (see https://en.wikipedia.org/wiki/Rechargeable_alkaline_battery). It would seem that this would be a better chemistry type to use for something like a satellite, where whilst in sunlight the batteries can be floated/topped up, than a chemistry such as NiCd where recharging before they hit their minimum threshold causes issues, however the number of cycles required to bring them back to full condition from a deep discharge could also be problematic.
I'm aware we aren't talking about run-of-the-mill AA cells, and are likely talking about some kind of custom size/shape cells instead, but it would seem to me that the chemistry is the cause of the 'early' failures, especially when coupled with the discharge/recharge cycles that the batteries would normally experience when moving between eclipse and sunlight. Of course this doesn't account for any clever software managing the charge cycle, and instead assumes that sunlight = charging and eclipse = discharging, so there's likely to be a lot more at stake than just the chemistry. Still food for thought, though, assuming the initial premise of 'they use NiCd cells' is correct.
73, John (M5ET)
-----Original Message----- From: John Brier [email protected] Sent: 07 December 2020 19:28 To: AMSAT BB [email protected] Subject: [AMSAT-BB] How to determine why Fox satellite batteries failed before projected 5 year lifetime
I hope for this to be a purely engineering based discussion that could shed some light on this question.
Please only respond from an engineering perspective in this thread.
Data:
According to the "AMSAT Fox-1 Systems Engineering Documentation" the satellites were expected to last at least five years. [1]
For each satellite, before there were any issues with the batteries, they were able to power the transponder continuously without going into safe mode. However, once battery issues were encountered, the transponder would turn off unexpectedly while the satellite went into safe mode. Using that cutoff my back of the hand calculations show the following [2]:
AO-92: batteries lasted 35% of their expected lifetime AO-91: batteries lasted 60% of their expected lifetime. AO-85: batteries lasted 87% of their expected lifetime.
I know the batteries used were Nicad. I know they were matched. I believe the issue so far has been that one cell in the set has failed such that the minimum voltage required to run the transponder is not met. Is that last point correct?
So that is the data that I am currently aware of.
I think the next data to procure would be to understand what information was used to project a five year lifetime. Then you could look at the available data about the real satellites (from telemetry for example) to find out if there are any discrepancies that would explain the reduced lifetime.
From my scanning of the "AMSAT Fox-1 Systems Engineering Documentation" I didn't see the battery chemistry mentioned.
However, in addition to the "AMSAT Fox-1 Systems Engineering Documentation" there is a lot of information in the Fox engineering material from past Symposium Proceedings. These are available as PDFs to AMSAT members.
Do people agree that the next steps would be to understand what information was used to project a lifetime of five years?
If so, can anyone tell me, or can anyone go through the past Symposium Proceedings, and lay out what information was used to project a five year lifetime?
If not, what are the better next steps in understanding the reduced battery lifetime?
73, John Brier KG4AKV
- 2.3 Reliability Requirements
2.3.1 The satellite shall be designed for a minimum 5-year, on-orbit lifetime. "
https://www.amsat.org/wordpress/wp-content/uploads/2018/06/AMSAT-Fox-Documen tation.pdf
- AO-92 was launched/commissioned in January 2018. AO-92 has had battery
issues since this fall such that it can't be used. AO-91 was launched/commissioned in November 2017 and now it too seems to be having the same battery issues. AO-85 was launched October 2015, declared EOM February 2020.
AMSAT-BB mailing list -- [email protected] View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to [email protected] Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org
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Thank you very much Paul.
I must have missed that during the Symposium.
So overall, do you think the time the satellites were in eclipse and in use was longer than expected?
Otherwise what would explain the higher than planned depth of discharge?
73, John Brier KG4AKV
P.S.
For anyone else looking through the PDF mentioned earlier, the cells mentioned on page 324 were 6x SANYO KR1700AU "A" CELLS, which apparently didn't end up being the actual used cells, as Paul mentioned
On Mon, Dec 7, 2020 at 2:59 PM Paul Stoetzer [email protected] wrote:
Each Fox-1 satellite uses 6 Sanyo KR-1400AE NiCd A cells.
Obviously we all hoped that the batteries would last a lot longer. As discussed during the Symposium, the likely cause of battery failure is a higher than planned depth of discharge. Note that AO-92's batteries failed more quickly than AO-91. Since AO-92's evening passes were generally between 9 and 11 pm, AO-92 saw lots of use while in ecilpse. Contrast that to AO-91, where the evening passes were generally after midnight, so it saw less use while in eclipse.
I'm not sure there's much to be learned from the experience with these batteries as NiCd battery technology is now certainly obsolete and will not be used in future AMSAT satellites. AMSAT's GOLF series of satellites will use lithium ion batteries. More information about the progress of GOLF, including the GOLF-TEE status paper from the 2020 Symposium Proceedings, can be found at https://www.amsat.org/greater-orbit-larger-footprint-an-introduction-to-the-...
73,
Paul, N8HM
Just one comment: Other than AO-91, (and upcoming Fox-1E) we had no telemetry to indicate whether a single battery pair was failing or if they failed "together". Only AO-91 had individual cell pair telemetry. (Pair: There were 6 cells, 2 parallel cells in a 3-series chain).
The 5-year prediction was made before my time at AMSAT. But I do know that the original plan (after AO-51 and for that matter 7) failed, was to design the power system so that if the batteries shorted, we would still run on solar panels. Many of you may have heard that said. But the launch time approached fast before such a design could be realized. And in fact despite the seemingly long times between some launches, the times when we had to be "hands off" on birds was too close to make many changes based on past experience. And of course the first one to go (AO-85) failed long after all the other 4 were either in orbit or frozen.
Burns, WB1FJ
On Mon, Dec 7, 2020 at 3:13 PM John Brier [email protected] wrote:
Thank you very much Paul.
I must have missed that during the Symposium.
So overall, do you think the time the satellites were in eclipse and in use was longer than expected?
Otherwise what would explain the higher than planned depth of discharge?
73, John Brier KG4AKV
P.S.
For anyone else looking through the PDF mentioned earlier, the cells mentioned on page 324 were 6x SANYO KR1700AU "A" CELLS, which apparently didn't end up being the actual used cells, as Paul mentioned
On Mon, Dec 7, 2020 at 2:59 PM Paul Stoetzer [email protected] wrote:
Each Fox-1 satellite uses 6 Sanyo KR-1400AE NiCd A cells.
Obviously we all hoped that the batteries would last a lot longer. As discussed during the Symposium, the likely cause of battery failure is a higher than planned depth of discharge. Note that AO-92's batteries failed more quickly than AO-91. Since AO-92's evening passes were generally between 9 and 11 pm, AO-92 saw lots of use while in ecilpse. Contrast that to AO-91, where the evening passes were generally after midnight, so it saw less use while in eclipse.
I'm not sure there's much to be learned from the experience with these batteries as NiCd battery technology is now certainly obsolete and will not be used in future AMSAT satellites. AMSAT's GOLF series of satellites will use lithium ion batteries. More information about the progress of GOLF, including the GOLF-TEE status paper from the 2020 Symposium Proceedings, can be found at
https://www.amsat.org/greater-orbit-larger-footprint-an-introduction-to-the-...
73,
Paul, N8HM
AMSAT-BB mailing list -- [email protected] View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to [email protected] Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org
Dear all,
This morning I plot the Cell A of the past week and I see three different battery discharge slope during evening pass over Jakarta (around 14:00 - 16:30 UTC)
The leftmost blue line in gray background shows normal discharge during evening pass, followed by slightly steeper decline that tripped the satellite into Safe mode just before TCA over me in Jakarta. The rightmost decline was from last night (16:23 UTC 7 Dec pass) that shows an even steeper decline. This is very discouraging in my opinion.
So, to prevent further deterioration of this cell, would it be possible to command “put into Safe Mode if in Eclipsed” ?
Use the sun sensor to determine sunlight.
73 de Yono - YD0NXX Jakarta, Indonesia - OI33JR
Sent from my iPhone
On Dec 8, 2020, at 11:33 AM, John Brier [email protected] wrote:
Thank you very much Paul.
I must have missed that during the Symposium.
So overall, do you think the time the satellites were in eclipse and in use was longer than expected?
Otherwise what would explain the higher than planned depth of discharge?
73, John Brier KG4AKV
P.S.
For anyone else looking through the PDF mentioned earlier, the cells mentioned on page 324 were 6x SANYO KR1700AU "A" CELLS, which apparently didn't end up being the actual used cells, as Paul mentioned
On Mon, Dec 7, 2020 at 2:59 PM Paul Stoetzer [email protected] wrote:
Each Fox-1 satellite uses 6 Sanyo KR-1400AE NiCd A cells.
Obviously we all hoped that the batteries would last a lot longer. As discussed during the Symposium, the likely cause of battery failure is a higher than planned depth of discharge. Note that AO-92's batteries failed more quickly than AO-91. Since AO-92's evening passes were generally between 9 and 11 pm, AO-92 saw lots of use while in ecilpse. Contrast that to AO-91, where the evening passes were generally after midnight, so it saw less use while in eclipse.
I'm not sure there's much to be learned from the experience with these batteries as NiCd battery technology is now certainly obsolete and will not be used in future AMSAT satellites. AMSAT's GOLF series of satellites will use lithium ion batteries. More information about the progress of GOLF, including the GOLF-TEE status paper from the 2020 Symposium Proceedings, can be found at https://www.amsat.org/greater-orbit-larger-footprint-an-introduction-to-the-...
73,
Paul, N8HM
AMSAT-BB mailing list -- [email protected] View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to [email protected] Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org
Thanks for the info, Yono. That is a very good idea; unfortunately the satellite does not have that kind of command capability. We have learned a lot from the Fox program!
73,
Burns WB1FJ
On Mon, Dec 7, 2020 at 11:58 PM Yono Adisoemarta [email protected] wrote:
Dear all,
This morning I plot the Cell A of the past week and I see three different battery discharge slope during evening pass over Jakarta (around 14:00 - 16:30 UTC)
The leftmost blue line in gray background shows normal discharge during evening pass, followed by slightly steeper decline that tripped the satellite into Safe mode just before TCA over me in Jakarta. The rightmost decline was from last night (16:23 UTC 7 Dec pass) that shows an even steeper decline. This is very discouraging in my opinion.
So, to prevent further deterioration of this cell, would it be possible to command “put into Safe Mode if in Eclipsed” ?
Use the sun sensor to determine sunlight.
73 de Yono - YD0NXX Jakarta, Indonesia - OI33JR
Sent from my iPhone
On Dec 8, 2020, at 11:33 AM, John Brier [email protected] wrote:
Thank you very much Paul.
I must have missed that during the Symposium.
So overall, do you think the time the satellites were in eclipse and in use was longer than expected?
Otherwise what would explain the higher than planned depth of discharge?
73, John Brier KG4AKV
P.S.
For anyone else looking through the PDF mentioned earlier, the cells mentioned on page 324 were 6x SANYO KR1700AU "A" CELLS, which apparently didn't end up being the actual used cells, as Paul mentioned
On Mon, Dec 7, 2020 at 2:59 PM Paul Stoetzer [email protected] wrote:
Each Fox-1 satellite uses 6 Sanyo KR-1400AE NiCd A cells.
Obviously we all hoped that the batteries would last a lot longer. As discussed during the Symposium, the likely cause of battery failure is a higher than planned depth of discharge. Note that AO-92's batteries failed more quickly than AO-91. Since AO-92's evening passes were generally between 9 and 11 pm, AO-92 saw lots of use while in ecilpse. Contrast that to AO-91, where the evening passes were generally after midnight, so it saw less use while in eclipse.
I'm not sure there's much to be learned from the experience with these batteries as NiCd battery technology is now certainly obsolete and will not be used in future AMSAT satellites. AMSAT's GOLF series of satellites will use lithium ion batteries. More information about the progress of GOLF, including the GOLF-TEE status paper from the 2020 Symposium Proceedings, can be found at
https://www.amsat.org/greater-orbit-larger-footprint-an-introduction-to-the-...
73,
Paul, N8HM
AMSAT-BB mailing list -- [email protected] View archives of this mailing list at
https://mailman.amsat.org/hyperkitty/list/[email protected]
To unsubscribe send an email to [email protected] Manage all of your AMSAT-NA mailing list preferences at
https://mailman.amsat.org
AMSAT-BB mailing list -- [email protected] View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to [email protected] Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org
This is a good example of why open source development is so important, especially for a small volunteer organization. A large, complex problem like developing a satellite is a difficult task for a small group of volunteers working countless hours. When the project can be reviewed by dozens of eyes all over the world more progress can be made in less time. We are about to launch a satellite that will most likely have the same issue unfortunately.
Howie AB2S
From: Burns Fishermailto:[email protected] Sent: Tuesday, December 8, 2020 9:01 AM To: Yono Adisoemartamailto:[email protected] Cc: AMSAT BBmailto:[email protected] Subject: [AMSAT-BB] Re: How to determine why Fox satellite batteries failed before projected 5 year lifetime
Thanks for the info, Yono. That is a very good idea; unfortunately the satellite does not have that kind of command capability. We have learned a lot from the Fox program!
73,
Burns WB1FJ
On Mon, Dec 7, 2020 at 11:58 PM Yono Adisoemarta <[email protected]mailto:[email protected]> wrote:
Dear all,
This morning I plot the Cell A of the past week and I see three different battery discharge slope during evening pass over Jakarta (around 14:00 - 16:30 UTC)
The leftmost blue line in gray background shows normal discharge during evening pass, followed by slightly steeper decline that tripped the satellite into Safe mode just before TCA over me in Jakarta. The rightmost decline was from last night (16:23 UTC 7 Dec pass) that shows an even steeper decline. This is very discouraging in my opinion.
So, to prevent further deterioration of this cell, would it be possible to command “put into Safe Mode if in Eclipsed” ?
Use the sun sensor to determine sunlight.
73 de Yono - YD0NXX Jakarta, Indonesia - OI33JR
Sent from my iPhone
On Dec 8, 2020, at 11:33 AM, John Brier <[email protected]mailto:[email protected]> wrote:
Thank you very much Paul.
I must have missed that during the Symposium.
So overall, do you think the time the satellites were in eclipse and in use was longer than expected?
Otherwise what would explain the higher than planned depth of discharge?
73, John Brier KG4AKV
P.S.
For anyone else looking through the PDF mentioned earlier, the cells mentioned on page 324 were 6x SANYO KR1700AU "A" CELLS, which apparently didn't end up being the actual used cells, as Paul mentioned
On Mon, Dec 7, 2020 at 2:59 PM Paul Stoetzer <[email protected]mailto:[email protected]> wrote:
Each Fox-1 satellite uses 6 Sanyo KR-1400AE NiCd A cells.
Obviously we all hoped that the batteries would last a lot longer. As discussed during the Symposium, the likely cause of battery failure is a higher than planned depth of discharge. Note that AO-92's batteries failed more quickly than AO-91. Since AO-92's evening passes were generally between 9 and 11 pm, AO-92 saw lots of use while in ecilpse. Contrast that to AO-91, where the evening passes were generally after midnight, so it saw less use while in eclipse.
I'm not sure there's much to be learned from the experience with these batteries as NiCd battery technology is now certainly obsolete and will not be used in future AMSAT satellites. AMSAT's GOLF series of satellites will use lithium ion batteries. More information about the progress of GOLF, including the GOLF-TEE status paper from the 2020 Symposium Proceedings, can be found at https://www.amsat.org/greater-orbit-larger-footprint-an-introduction-to-the-...
73,
Paul, N8HM
AMSAT-BB mailing list -- [email protected]mailto:[email protected] View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to [email protected]mailto:[email protected] Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org
----------------------------------------------- AMSAT-BB mailing list -- [email protected]mailto:[email protected] View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to [email protected]mailto:[email protected] Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org
On 12/08/20 08:25, Howie DeFelice wrote:
This is a good example of why open source development is so important, especially for a small volunteer organization. A large, complex problem like developing a satellite is a difficult task for a small group of volunteers working countless hours. When the project can be reviewed by dozens of eyes all over the world more progress can be made in less time. We are about to launch a satellite that will most likely have the same issue unfortunately.
Howie,
A corollary to your statement is: too many cooks spoil the broth.
Anyone can join the GOLF software development effort as a volunteer. All one has to do is ask, and be verified as a "US Person". That gets you in the door, so to speak, to look at the software.
However, don't expect that those who have put in the years (decades, in some circumstances) will rewrite the codebase to based on your views, opinions, or concerns, valid or not.
"Open Source" isn't a panacea, nor is it the only solution to complex software development. I support OSS, but I also support not-OSS, depending on my needs. I enjoy earning a living developing systems which I don't then give away to customers for free.
You, and others, have done much to try to discredit the development process that AMSAT has in place. I had hoped that these shenanigans would stop with the end of the election, but I'm proven wrong again.
--- Zach N0ZGO
Back to engineering... It was pointed out to me that AO-85 may have been the only Fox satellite that did not use the Maximum Point Power Tracker (MPPT). [1]
Therefore, for AO-92 and AO-91, the MPPT "definitely more effectively charged the cells compared to the AO-85 linear regulator approach."
This is speculative but "that coupled with anything (faster charging or less deep cycles because it allows more charging opportunities at higher charging rates which is usually a good thing but maybe not with NiCD)" could explain why AO-91 and AO-92 batteries failed sooner than AO-85.
Less deep charge cycles could cause memory issues, as pointed out earlier.
73, John Brier KG4AKV
1) https://github.com/FaradayRF/Fox-1-MPPT
On Tue, Dec 8, 2020 at 9:26 AM Howie DeFelice [email protected] wrote:
This is a good example of why open source development is so important, especially for a small volunteer organization. A large, complex problem like developing a satellite is a difficult task for a small group of volunteers working countless hours. When the project can be reviewed by dozens of eyes all over the world more progress can be made in less time. We are about to launch a satellite that will most likely have the same issue unfortunately.
Howie AB2S
From: Burns Fisher Sent: Tuesday, December 8, 2020 9:01 AM To: Yono Adisoemarta Cc: AMSAT BB Subject: [AMSAT-BB] Re: How to determine why Fox satellite batteries failed before projected 5 year lifetime
Thanks for the info, Yono. That is a very good idea; unfortunately the satellite does not have that kind of command capability. We have learned a lot from the Fox program!
73,
Burns WB1FJ
On Mon, Dec 7, 2020 at 11:58 PM Yono Adisoemarta [email protected] wrote:
Dear all,
This morning I plot the Cell A of the past week and I see three different battery discharge slope during evening pass over Jakarta (around 14:00 - 16:30 UTC)
The leftmost blue line in gray background shows normal discharge during evening pass, followed by slightly steeper decline that tripped the satellite into Safe mode just before TCA over me in Jakarta. The rightmost decline was from last night (16:23 UTC 7 Dec pass) that shows an even steeper decline. This is very discouraging in my opinion.
So, to prevent further deterioration of this cell, would it be possible to command “put into Safe Mode if in Eclipsed” ?
Use the sun sensor to determine sunlight.
73 de Yono - YD0NXX Jakarta, Indonesia - OI33JR
Sent from my iPhone
On Dec 8, 2020, at 11:33 AM, John Brier [email protected] wrote:
Thank you very much Paul.
I must have missed that during the Symposium.
So overall, do you think the time the satellites were in eclipse and in use was longer than expected?
Otherwise what would explain the higher than planned depth of discharge?
73, John Brier KG4AKV
P.S.
For anyone else looking through the PDF mentioned earlier, the cells mentioned on page 324 were 6x SANYO KR1700AU "A" CELLS, which apparently didn't end up being the actual used cells, as Paul mentioned
On Mon, Dec 7, 2020 at 2:59 PM Paul Stoetzer [email protected] wrote:
Each Fox-1 satellite uses 6 Sanyo KR-1400AE NiCd A cells.
Obviously we all hoped that the batteries would last a lot longer. As discussed during the Symposium, the likely cause of battery failure is a higher than planned depth of discharge. Note that AO-92's batteries failed more quickly than AO-91. Since AO-92's evening passes were generally between 9 and 11 pm, AO-92 saw lots of use while in ecilpse. Contrast that to AO-91, where the evening passes were generally after midnight, so it saw less use while in eclipse.
I'm not sure there's much to be learned from the experience with these batteries as NiCd battery technology is now certainly obsolete and will not be used in future AMSAT satellites. AMSAT's GOLF series of satellites will use lithium ion batteries. More information about the progress of GOLF, including the GOLF-TEE status paper from the 2020 Symposium Proceedings, can be found at https://www.amsat.org/greater-orbit-larger-footprint-an-introduction-to-the-...
73,
Paul, N8HM
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This morning I plot the Cell A of the past week and I see three different
battery discharge slope during evening pass over Jakarta (around 14:00 - 16:30 UTC)
<SNIP>
So, to prevent further deterioration of this cell, would it be possible to
command “put into Safe Mode if in Eclipsed” ?
THe occurrence of user load towards ened of eclipse causing a crash can occur anywhere on earth for any given orbit season. But it will always be between midnight and sunrise local time.
So a version of FOX TLM can watch the battery voltages and if low-v cutout is approaching, then the ground station can "jam the uplink" with some channel activityPTT with incorrect PL to prevent the Xponder from coming up? Unorthodox but it is in the wee hours locally an will not have much impact on users). ... If it saves the satellite from reset.
Bob
On 12/7/2020 13:27, John Brier wrote:
I hope for this to be a purely engineering based discussion that could shed some light on this question.
Please only respond from an engineering perspective in this thread.
Data:
According to the "AMSAT Fox-1 Systems Engineering Documentation" the satellites were expected to last at least five years. [1]
It's nice to see this discussion going on, a thank you to those who join in.
I want to comment on the five year expectation. That certainly is/was the goal for the Fox-1 series however there are some things that I think soften that requirement statement, which as Burns mentioned was also made "before my time". Not that I disagree with it. As the overall project was a first, given the reduction down to a 1U CubeSat albeit packed with stuff, there were assumptions made based on data and many times minimal or lack of data. The five years is overall and not specifically based on battery lifetime, in fact operation after the battery died was part of the original napkin and so it was a consideration in the five years as well.
The cells originally scoped were KR1700 and were out of production at the time I joined in 2011. As the years passed and the cells sat awaiting someone who knew matching, by 2014 when we did find someone who could do that it turns out that those cells were by now less capacity than the KR1400. Which were also out of production. Because of the A size form factor designed and being built, we were rather stuck to using old NiCd.
Only five sets were made because of the lack of quantity of those cells. Further newer cells were rejected as opinions of our battery providers was that they were of a much lower quality as intended for "toys" and none would recommend that we put them on our satellites.
The battery circuitry was designed for simple charging, no cycling. I think that given one Fox-1 and an expectation that it would launch right quickly after initial designs, no one understood that it would be years before the batteries flew. I considered the possibility of trying to properly tend the battery cells with Fox-1B and -E but there was really no way to just plug a tender in the umbilical as blocking and voltage reduction diodes would prevent discharge, although you could discharge it using the voltage (DVM) pin, but that would require a specifically wired tender and we determined that the risk was too high. Of course, even AO-85 had not failed yet at that time.
And the cells sit awaiting launch not only in Fox Labs where I could at least charge them, but in the case of AO-85 for 7 months it was untouchable being integrated and out of our hands, prior to launch. AO-91 -B did have a much faster turnaround from the Labs to launch, about 2 months IIRC without looking. AO-92 -D was years from completion to launch although somewhere around 3 months from integration to launch, again by memory on the number.
The basis of the battery cell lifetime was essentially depth of discharge, to keep that at 20% or less per orbit. I do not know the how and why for that decision, sorry, again that was a before my time thing. In any case none of the Fox-1 except AO-95 -Cliff experience that little DOD on a regular basis anyway. Interestingly as this comes about, Fox-1Cliff AO-95 is the one that has become a benchmark in a sense, as it certainly has less than 20% DOD. How its cells behave and how long may be useful for conclusions on this battery behavior "study". Unfortunately being one of the early, actual the second, Fox-1 builds it does not have thee specific cell telemetry either but only total voltage of the battery.
As you see there are a lot of unseen things that you may not all be aware of, although I have discussed them before either in Symposium or Journal columns here and there, and most recently because of what is happening. The five year lifetime as a whole was based on best understanding of what was being done, and the design, but had deviations introduced due to lack of knowledge and time to delivery. And here we are in an era now, where getting a launch to an orbit that even lasts five years might put the EOL on re-entry instead of battery life for Fox-1E.
I appreciate the community discussion of what's going on, I am curious as heck about it but never have time to actually do anything to satisfy that curiosity... While the outcome may not be of use for future satellites given the changes in stored power it is definitely part of AMSAT's purpose to learn and educate from everything we do. And it could be fun! (Maybe Paul will send a commemorative QSO to whoever arrives at the definitive answer first.)
Jerry Buxton, NØJY
Awesome write up Jerry!
I figured the size reduction would have created so many trade-offs, the battery likely being one of them, and your post confirmed (to me) my suspicions.
On Wed, Dec 9, 2020 at 5:52 PM Jerry Buxton [email protected] wrote:
On 12/7/2020 13:27, John Brier wrote:
I hope for this to be a purely engineering based discussion that could shed some light on this question.
Please only respond from an engineering perspective in this thread.
Data:
According to the "AMSAT Fox-1 Systems Engineering Documentation" the satellites were expected to last at least five years. [1]
It's nice to see this discussion going on, a thank you to those who join in.
I want to comment on the five year expectation. That certainly is/was the goal for the Fox-1 series however there are some things that I think soften that requirement statement, which as Burns mentioned was also made "before my time". Not that I disagree with it. As the overall project was a first, given the reduction down to a 1U CubeSat albeit packed with stuff, there were assumptions made based on data and many times minimal or lack of data. The five years is overall and not specifically based on battery lifetime, in fact operation after the battery died was part of the original napkin and so it was a consideration in the five years as well.
The cells originally scoped were KR1700 and were out of production at the time I joined in 2011. As the years passed and the cells sat awaiting someone who knew matching, by 2014 when we did find someone who could do that it turns out that those cells were by now less capacity than the KR1400. Which were also out of production. Because of the A size form factor designed and being built, we were rather stuck to using old NiCd.
Only five sets were made because of the lack of quantity of those cells. Further newer cells were rejected as opinions of our battery providers was that they were of a much lower quality as intended for "toys" and none would recommend that we put them on our satellites.
The battery circuitry was designed for simple charging, no cycling. I think that given one Fox-1 and an expectation that it would launch right quickly after initial designs, no one understood that it would be years before the batteries flew. I considered the possibility of trying to properly tend the battery cells with Fox-1B and -E but there was really no way to just plug a tender in the umbilical as blocking and voltage reduction diodes would prevent discharge, although you could discharge it using the voltage (DVM) pin, but that would require a specifically wired tender and we determined that the risk was too high. Of course, even AO-85 had not failed yet at that time.
And the cells sit awaiting launch not only in Fox Labs where I could at least charge them, but in the case of AO-85 for 7 months it was untouchable being integrated and out of our hands, prior to launch. AO-91 -B did have a much faster turnaround from the Labs to launch, about 2 months IIRC without looking. AO-92 -D was years from completion to launch although somewhere around 3 months from integration to launch, again by memory on the number.
The basis of the battery cell lifetime was essentially depth of discharge, to keep that at 20% or less per orbit. I do not know the how and why for that decision, sorry, again that was a before my time thing. In any case none of the Fox-1 except AO-95 -Cliff experience that little DOD on a regular basis anyway. Interestingly as this comes about, Fox-1Cliff AO-95 is the one that has become a benchmark in a sense, as it certainly has less than 20% DOD. How its cells behave and how long may be useful for conclusions on this battery behavior "study". Unfortunately being one of the early, actual the second, Fox-1 builds it does not have thee specific cell telemetry either but only total voltage of the battery.
As you see there are a lot of unseen things that you may not all be aware of, although I have discussed them before either in Symposium or Journal columns here and there, and most recently because of what is happening. The five year lifetime as a whole was based on best understanding of what was being done, and the design, but had deviations introduced due to lack of knowledge and time to delivery. And here we are in an era now, where getting a launch to an orbit that even lasts five years might put the EOL on re-entry instead of battery life for Fox-1E.
I appreciate the community discussion of what's going on, I am curious as heck about it but never have time to actually do anything to satisfy that curiosity... While the outcome may not be of use for future satellites given the changes in stored power it is definitely part of AMSAT's purpose to learn and educate from everything we do. And it could be fun! (Maybe Paul will send a commemorative QSO to whoever arrives at the definitive answer first.)
Jerry Buxton, NØJY
AMSAT-BB mailing list -- [email protected] View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to [email protected] Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org
Jerry -thanks for that detailed explanation.
One of the challenges I think with the Fox design is the way the manifesting and integrating cubesats may affect battery lifetime in unexpected ways compared to historical experience with spacecraft. As best I recall, in 1992-93, the NiCd batteries used in what became AO-27 and IO-26 were sourced from someone working with SSTL who had NiCd matching down to a science and was able to work with relatively newer cells. I think the SSTL satellites were using the same batteries, and I don't recall supply chain / discontinued product issues Fox had to deal with. Also, AO-27 was accessible to the development team until a few weeks at most before launch when integration of all 6 secondary payloads was completed. I believe there were provisions to keep batteries charged before launch but not 100% certain. In contrast, the realities of cubesat launches almost guarantee a lengthy gap between final spacecraft integration and launch, with no opportunities for battery maintenance. So the requirements for the battery in a future mission might include "shall survive without maintenance for xx months until launch and deployment without adverse effect on battery lifetime" or some such (easy to spec, probably way harder than I know to deliver!).
Managing depth of discharge has been vital for long battery life. AO-27 was managed very aggressively - 15-20 minutes on early in it's life, 4 min at a time today. Something is better than nothing? I'm not suggesting we should have done that with the Fox satellites, I am curious if there is data from SO-50 as it continues to be used heavily and seems fine after 18 years in space. Keep in mind these satellites are larger compared to Fox, have larger capacity cells, less dramatic thermal changes, operate at a higher bus voltage (AO-27 is nominal 10v) and there may be changes between the early-mid 1990s NiCd battery chemistry and manufacture vs. 2010s that individually and in sum affect longevity in space. Tradeoffs are tough design decisions that have to be made to get from something perfect but unbuildable to feasible and flying.
There are a bunch of lessons here affecting all sorts of requirements and resulting engineering tradeoffs and operations decisions - battery capacity and chemistry, supply availability and shelf life before integration, self-discharge, ability to monitor individual cells, ability to manage depth of discharge after assembly and from integration until launch, and managing the battery once in space. More capability also means more circuitry, more software code, and more places something has to be tested and could fail. And have sufficient time in development and test to validate and incorporate good ideas that improve reliability and longevity (we hams may be the only people who would get excited about using satellites 46 years old (AO-7), 27 (AO-27), turning 8 (SO-50), or failed to deploy from the launcher (RS-44)!)
Steve KS1G
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.
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]mailto:[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.
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.
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]mailto:[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]mailto:[email protected]> Sent: Wednesday, December 9, 2020 10:34 PM To: Steve Greene <[email protected]mailto:[email protected]> Cc: AMSAT BB <[email protected]mailto:[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]mailto:[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.
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 stampwould 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.
----------------------------------------------- AMSAT-BB mailing list -- [email protected] View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to [email protected] Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org
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]mailto:[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]mailto:[email protected]> Sent: Wednesday, December 9, 2020 10:50 PM To: Samudra Haque [TTLLC] <[email protected]mailto:[email protected]> Cc: Steve Greene <[email protected]mailto:[email protected]>; AMSAT BB <[email protected]mailto:[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]mailto:[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]mailto:[email protected]> Sent: Wednesday, December 9, 2020 10:34 PM To: Steve Greene <[email protected]mailto:[email protected]> Cc: AMSAT BB <[email protected]mailto:[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]mailto:[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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Just a comment on a couple things said here:
1) It is a great idea to have a 'fallback, sun-only' mode for when the batteries fail. Having remembered the lessons of AO-7 and AO-51, this was the original plan for Fox, but as I may have said, we ran out of time and perhaps space on the bird. (This was not my area of expertise, but I did live close to and talk a lot with Tony AA2TX(SK), who was VPE at the beginning of the project before sadly going silent key).
2) Multiple receivers is also an excellent idea. Golf-TEE will have at least 3 command-capable receivers! Fox birds, even AO-92 and 95, have exactly one. The L-band uplink on AO-92 and 95 is actually a downshifter to the same receiver. We did try commanding 95 via L-band to no avail, by the way.
Thanks for the excellent discussion.
73,
Burns WB1FJ Fox and Golf Flight Software
On Thu, Dec 10, 2020 at 8:07 AM Samudra Haque [TTLLC] < [email protected]> wrote:
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.
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Steve writes:
As best I recall, in 1992-93, the NiCd batteries used in what became
AO-27 and IO-26 were sourced from
someone working with SSTL who had NiCd matching down to a science and was
able to work with relatively
newer cells.
This was possibly Larry Kayser, VA3LK. Larry was involved in the battery selection process for UO-11 where he took about 250-or-so new NiCd batteries and "matched" them to pick the ones to fly on UO-11 and several other satellites. He had a very detailed meticulous process for characterizing each battery cell to decide which cells to put together into the battery pack on the satellite. UO-11's batteries are still working after tens of thousands of charge/discharge cycles. Nobody else's matching process is even close to that.
Unfortunately, after much research, I still cannot find anything that Larry wrote down that describes in detail the steps he followed to "match" the battery cells. I know he plotted many charge/discharge curves for each cell over many different charge/discharge/temperature conditions, and even X-rayed some cells to find other defects, but exactly what conditions he tested and exactly what he did with the charge/discharge curves to "match" the batteries remains somewhat of a mystery.
As far as I know he never published the steps for his methods before he became a silent key. The best, but somewhat cryptic, statement I found from him was that when selecting the cells you want the "best matched" cells for your battey, which are not necessarily the "best" cells that you have. But how exactly do you determine which ones are "best matched" to each other?
If anyone knows ANYTHING about his battery matching methods, please send me whatever knowledge you have however small.
Earlier in a different thread Joe wrote:
What baby steps can we all take together to open up as much information
as we can as soon as we can?
If you do something and it works, especially if it works well, publish your results and your methods to achieve those results so that others can learn and build on your knowledge and experience. And, that's just a start. It's not enough to just publish it on just your personal website, as I recently discovered when I tried to get some not-so-old UO-11 telemetry. The author of that website had become a silent key. The website was no longer on the web, and archive.org had not archived the entire site!
Hard won knowledge has been lost in both cases. We need to do better.
One suggestion would be to keep a living document, updated regularly, with copies online in multiple places, with the lessons learned and knowledge gained, and make it required reading for each new generation of satellite builders. Contact me if you think this is a good idea, or even if you think it's a bad idea.
73, Douglas KA2UPW/5 "Steps down from soapbox...."
On Wed, Dec 9, 2020 at 6:55 PM Steve Greene [email protected] wrote:
Jerry -thanks for that detailed explanation.
One of the challenges I think with the Fox design is the way the manifesting and integrating cubesats may affect battery lifetime in unexpected ways compared to historical experience with spacecraft. As best I recall, in 1992-93, the NiCd batteries used in what became AO-27 and IO-26 were sourced from someone working with SSTL who had NiCd matching down to a science and was able to work with relatively newer cells. I think the SSTL satellites were using the same batteries, and I don't recall supply chain / discontinued product issues Fox had to deal with. Also, AO-27 was accessible to the development team until a few weeks at most before launch when integration of all 6 secondary payloads was completed. I believe there were provisions to keep batteries charged before launch but not 100% certain. In contrast, the realities of cubesat launches almost guarantee a lengthy gap between final spacecraft integration and launch, with no opportunities for battery maintenance. So the req uirements for the battery in a future mission might include "shall survive without maintenance for xx months until launch and deployment without adverse effect on battery lifetime" or some such (easy to spec, probably way harder than I know to deliver!).
Managing depth of discharge has been vital for long battery life. AO-27 was managed very aggressively - 15-20 minutes on early in it's life, 4 min at a time today. Something is better than nothing? I'm not suggesting we should have done that with the Fox satellites, I am curious if there is data from SO-50 as it continues to be used heavily and seems fine after 18 years in space. Keep in mind these satellites are larger compared to Fox, have larger capacity cells, less dramatic thermal changes, operate at a higher bus voltage (AO-27 is nominal 10v) and there may be changes between the early-mid 1990s NiCd battery chemistry and manufacture vs. 2010s that individually and in sum affect longevity in space. Tradeoffs are tough design decisions that have to be made to get from something perfect but unbuildable to feasible and flying.
There are a bunch of lessons here affecting all sorts of requirements and resulting engineering tradeoffs and operations decisions - battery capacity and chemistry, supply availability and shelf life before integration, self-discharge, ability to monitor individual cells, ability to manage depth of discharge after assembly and from integration until launch, and managing the battery once in space. More capability also means more circuitry, more software code, and more places something has to be tested and could fail. And have sufficient time in development and test to validate and incorporate good ideas that improve reliability and longevity (we hams may be the only people who would get excited about using satellites 46 years old (AO-7), 27 (AO-27), turning 8 (SO-50), or failed to deploy from the launcher (RS-44)!)
Steve KS1G
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-
Burns Fisher -
Don KB2YSI -
Douglas Quagliana -
Howie DeFelice -
Jerry Buxton -
John -
John Brier -
KENT BRITAIN -
Paul Stoetzer -
Robert Bruninga -
Samudra Haque [TTLLC] -
Steve Greene -
Yono Adisoemarta -
Zach Metzinger