SSU Development Thread (3.0 to 4.0)

[STS]

No. Only more work. :lol:

Are you my last boss? :rofl:

 

[GLS]

I've been looking at the Ku-band diagrams DaveS provided (thanks!), and I've found what appears to be an error on lower of the 4 contacts of the Ku DPY/GND/STO switch :facepalm:. It's wired in reverse, so STO deploys and DPY stows.
Anyway, electrical diagrams are SO much easier to interpret than text: there's no connection to the PLB position in the deploy circuitry, so that's settled once and for all.
Also, interestingly the GND position allows the GPCs to command a deploy, but not a stow.

 

[Urwumpe]

I've been looking at the Ku-band diagrams DaveS provided (thanks!), and I've found what appears to be an error on lower of the 4 contacts of the Ku DPY/GND/STO switch :facepalm:. It's wired in reverse, so STO deploys and DPY stows.

I would not be too sure there that there is really an error - can you tell me the page, so I can look? Maybe you just think too directly for the time at which the space Shuttle was created.

 

[DaveS]

I've been looking at the Ku-band diagrams DaveS provided (thanks!), and I've found what appears to be an error on lower of the 4 contacts of the Ku DPY/GND/STO switch :facepalm:. It's wired in reverse, so STO deploys and DPY stows.
Anyway, electrical diagrams are SO much easier to interpret than text: there's no connection to the PLB position in the deploy circuitry, so that's settled once and for all.
Also, interestingly the GND position allows the GPCs to command a deploy, but not a stow.

I read somewhere that the idea behind the GND position was so that MCC could command the antenna through the GCIL. This was never implemented (along with a host of other stuff) so the position serves as an intermediate "OFF" position.

 

[GLS]

I would not be too sure there that there is really an error - can you tell me the page, so I can look? Maybe you just think too directly for the time at which the space Shuttle was created.

It's diagram 15.7, on volume 2.

---------- Post added at 06:32 PM ---------- Previous post was at 06:31 PM ----------

I read somewhere that the idea behind the GND position was so that MCC could command the antenna through the GCIL. This was never implemented (along with a host of other stuff) so the position serves as an intermediate "OFF" position.

Yeah, that position does nothing unless there's there are 4 commands issued (2 per motor).

 

[Urwumpe]

It's diagram 15.7, on volume 2.

Ok, from a quick glance at it, I can confirm that the DEPLOY position corresponds to enabling the coil of the deploy relay (unless the DEPLOYED signal is TRUE), which in turn provides AC currents in deploy order to the motor. For STOW, the system is similar.

 

[GLS]

Ok, from a quick glance at it, I can confirm that the DEPLOY position corresponds to enabling the coil of the deploy relay (unless the DEPLOYED signal is TRUE), which in turn provides AC currents in deploy order to the motor. For STOW, the system is similar.

On the top 3 contacts of the switch yes, but the bottom pair is reversed.

 

[Urwumpe]

On the top 3 contacts of the switch yes, but the bottom pair is reversed.

No, it is not. Possibly it looks just different because the lines are drawn in a different vertical order. If you track the power from switch through logic gates and amplifiers it goes from DEPLOY to DEPLOY coil with the third microswitch, while it goes from DEPLOY to inhibiting STOW with the fourth microswitch.

 

[GLS]

No, it is not. Possibly it looks just different because the lines are drawn in a different vertical order. If you track the power from switch through logic gates and amplifiers it goes from DEPLOY to DEPLOY coil with the third microswitch, while it goes from DEPLOY to inhibiting STOW with the fourth microswitch.

Then we are looking at different diagrams.
I not only tracked but I painted the lines, and the bottom line out of the switch "block", a stow signal, goes to a tristate buffer that activates the deploy coil K37.

 

[Urwumpe]

Then we are looking at different diagrams.
I not only tracked but I painted the lines, and the bottom line out of the switch "block", a stow signal, goes to a tristate buffer that activates the deploy coil K37.

I see a different path here.

coil K37 is only activated by switch in GND or MDM LF1. You need K37 and K27 for deploying the DA by motor 2.

As small logic table

Position | Microswitch | Effect
DEPLOY|3|K27 energized, Tristate K27 is Lo-Z
DEPLOY|4|Tristate for K2 is Lo-Z =>K2 (Stow) = (<BOOM STOW ENABLE II>and not <STOWED>)
GND|3|Tristate K27 is Lo-Z => K27 (Deploy) = <V54K0014W>:<LF1> and not <DEPLOYED>
GND|4|Tristate K2 is Lo-Z => K2(Stow) = Not <DEPLOYED>
STOW|3|Tri-State K25 is Lo-Z => K25(Stow) = (<BOOM STOW ENABLE I> OR <DIRECT STOW>) and not <STOWED>
STOW|4|Tri-State K37 is Low-Z => K38(Deploy)=<V54K0004W>:<LF1> and not <DEPLOYED>

 

[GLS]

I see a different path here.

coil K37 is only activated by switch in GND or MDM LF1. You need K37 and K27 for deploying the DA by motor 2.

As small logic table

Position | Microswitch | Effect
DEPLOY|3|K27 energized, Tristate K27 is Lo-Z
DEPLOY|4|Tristate for K2 is Lo-Z =>K2 (Stow) = (<BOOM STOW ENABLE II>and not <STOWED>)
GND|3|Tristate K27 is Lo-Z => K27 (Deploy) = <V54K0014W>:<LF1> and not <DEPLOYED>
GND|4|Tristate K2 is Lo-Z => K2(Stow) = Not <DEPLOYED>
STOW|3|Tri-State K25 is Lo-Z => K25(Stow) = (<BOOM STOW ENABLE I> OR <DIRECT STOW>) and not <STOWED>
STOW|4|Tri-State K37 is Low-Z => K38(Deploy)=<V54K0004W>:<LF1> and not <DEPLOYED>

I keep looking, and to me the switch wires (just until the tristate buffers) are switched on the K2 and K37 coils. I'll try to post an image with colors...

 

[Urwumpe]

I keep looking, and to me the switch wires (just until the tristate buffers) are switched on the K2 and K37 coils. I'll try to post an image with colors...

Yes, but for understanding how the motors behave you also need the signals from the EA-1.

 

[GLS]

Here it is: https://imgur.com/download/N7jvoZB
So, I think the bottom blue and red wires are switched, because the blue (deploy) can be bypassed by the Direct Stow switch (doesn't make sense)...

---------- Post added at 08:46 PM ---------- Previous post was at 08:45 PM ----------

Yes, but for understanding how the motors behave you also need the signals from the EA-1.

Yes, those stow signals are just for the stow, not for deploy

---------- Post added at 08:48 PM ---------- Previous post was at 08:46 PM ----------

I think all 3 wires on the bottom contact are switched....

---------- Post added at 08:49 PM ---------- Previous post was at 08:48 PM ----------

Red should be yellow,
yellow should be blue,
blue should be red.

 

[Urwumpe]

I think all 3 wires on the bottom contact are switched....

I still think they are correct that way. Just compare them to the second - they are mirroring each other.

---------- Post added at 11:35 PM ---------- Previous post was at 10:57 PM ----------

And now, I think you are right - I have backtracked from the motor relays to the switches and painted the lines in two colors: Red for deploy relays, blue for Stow relays.

Only the fourth group of contacts is inverse.

I apologize, I was 99% sure that it must work out that way and that it just appears strange because the second deploy relay in series is powered on by EA-1. But I was wrong. It can't work according to the plan. Who mails NASA that their drawing is wrong?

 

[GLS]

I still think they are correct that way. Just compare them to the second - they are mirroring each other.

---------- Post added at 11:35 PM ---------- Previous post was at 10:57 PM ----------

And now, I think you are right - I have backtracked from the motor relays to the switches and painted the lines in two colors: Red for deploy relays, blue for Stow relays.

Only the fourth group of contacts is inverse.

I apologize, I was 99% sure that it must work out that way and that it just appears strange because the second deploy relay in series is powered on by EA-1. But I was wrong. It can't work according to the plan. Who mails NASA that their drawing is wrong?

No need to apologize, although I was out of arguments... "there's the diagram, what more can I say?". :lol:
I don't think NASA cares... specially now that they don't own the hardware. It's another to add to the list of NASA screw-ups. Happily nobody died from this one.

 

[DaveS]

No need to apologize, although I was out of arguments... "there's the diagram, what more can I say?". :lol:
I don't think NASA cares... specially now that they don't own the hardware. It's another to add to the list of NASA screw-ups. Happily nobody died from this one.

Actually they still do own Atlantis. Only ownership of Discovery and Endeavour were transferred.

 

[Urwumpe]

No need to apologize, although I was out of arguments... "there's the diagram, what more can I say?". :lol:
I don't think NASA cares... specially now that they don't own the hardware. It's another to add to the list of NASA screw-ups. Happily nobody died from this one.

I think it means that we should be very careful with those drawings and check them for consistency.

And what do you think about adding an errata document to the References of SSU?

 

[GLS]

I think it means that we should be very careful with those drawings and check them for consistency.

And what do you think about adding an errata document to the References of SSU?

I always try to have things make (some) sense in my head. I also do what I later found out to be Gene Kranz's method for learning diagrams: paint the lines.
I just changed the line colors to correct the error. If it helps I could upload it to the references folder, but right now I can't steer away from this antenna business.

 

[Urwumpe]

I always try to have things make (some) sense in my head. I also do what I later found out to be Gene Kranz's method for learning diagrams: paint the lines.
I just changed the line colors to correct the error. If it helps I could upload it to the references folder, but right now I can't steer away from this antenna business.

No problem. I just thought about making a small text file for the start, since it is only one error. Should we find more, we should make it a PDF.

 

[DaveS]

GLS: How far along are with the Ku band system? I'm looking forward to having a new system to learn.