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ISS ATU's (communication panels) need water cooling? Why?



 
 
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  #11  
Old February 20th 10, 05:48 AM posted to sci.space.station
J. Porter Clark[_2_]
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Posts: 11
Default ISS ATU's (communication panels) need water cooling? Why?

"Jorge R. Frank" writes:

Porter Clark used to post here... maybe he will de-lurk.


Huh? Whazza?

ATU power consumption when in full power mode is about 28 W.
This is just enough so that we can't count on ambient air to
keep it cool in zero G. All of the flight ATUs are on cold
plates. The mount in the Cupola is unusual in many ways.
There's a flight rule that allows the ATUs to run for some
period of time (IIRC, 30 minutes) without cooling water running.

The ATU was originally designed to allow for either cold plate
cooling or for ambient airflow at some rate and temperature.
That's why it has pin-fin heatsinks on the outside. However,
Boeing never found a good way to make the airflow method work in
any of their elements, and so it was abandoned.

ATUs sitting open in a rack in one G don't get hot enough to
need any help cooling, although the rack we usually put them in
for testing has fans in it.

The ATU features were the result of requirements from many
groups of people, and so it has a lot of buttons for features
that most people don't use--probably about like your office
phone or cell phone. Usually, the crew just leaves them
configured in the Big Loop (with S/G 1) and they go to other
loops as they need. There is a way to call from one ATU to
another, but the crew isn't even trained to use it nowadays.

The ATUs were designed in the late 1980s. They were fairly
advanced in those days, but they are big and bulky by today's
standards. They do work, however. We have had two ATU failures
on orbit; they were both in the same location in the Airlock.

The Airlock is the only element with 3 ATUs. The reason
the Airlock needs 3 is that 2 of them are used for hardline
connections to two EVA-suited crewmen. This was a cheaper
solution than the creation of a unique interface box just for
the suits.

  #12  
Old February 20th 10, 05:11 PM posted to sci.space.station
David Spain
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Posts: 2,901
Default ISS ATU's (communication panels) need water cooling? Why?

(J. Porter Clark) writes:

"Jorge R. Frank" writes:

Porter Clark used to post here... maybe he will de-lurk.



Thanks Jorge.

Huh? Whazza?

ATU power consumption when in full power mode is about 28 W.
This is just enough so that we can't count on ambient air to
keep it cool in zero G. All of the flight ATUs are on cold
plates. The mount in the Cupola is unusual in many ways.
There's a flight rule that allows the ATUs to run for some
period of time (IIRC, 30 minutes) without cooling water running.


Hi Porter,

Thanks for getting back to us!

I linked to your website on Angelfire after an intensive Google
search in response to a question by Jordan Hazen about the
ATU having water lines running to it.

Since the ATU in the cupola shares an equipment bay with several
other electronics modules (such as the one that controls the station's
robotic arm, etc.) I was wondering if you could tell us if the cold
plates are shared between the modules in the cupola or if there are
separate water lines running to each, such as one for the ATU, another
for the robotic arm controller [I have no handy acronym for that :-)]
etc, or if they share a common cold plate which water cools for
everything in the cupola?

What is that connector at the top of the ATU, designed for immortals
;-), actually for?

As regards the rear cabling, I'm guessing:

1. Left-most multipin connector looks like it loops pins to
possibly +V or GND. I'm assuming this is the addressing connector
and the connections are unique per ATU? In practice does this
allow an ATU to be swapped with any other ATU in case you have
a failure and can afford to sacrific one less used? Has that
ever happened on the ISS?

2. The middle connector has the 3 fiber optic communications links.
So what is up with that 3rd fiber? From your caption it sounds like
it is dark? Does it not exist in the flight configuration?

3. The bottom right connector is power? Are you running a standard
voltage on the ISS? Curious to know if it's 48VDC?

The ATU was originally designed to allow for either cold plate
cooling or for ambient airflow at some rate and temperature.
That's why it has pin-fin heatsinks on the outside. However,
Boeing never found a good way to make the airflow method work in
any of their elements, and so it was abandoned.


Does the cold plate attach on the finned side of the ATU?

ATUs sitting open in a rack in one G don't get hot enough to
need any help cooling, although the rack we usually put them in
for testing has fans in it.

The ATU features were the result of requirements from many
groups of people, and so it has a lot of buttons for features
that most people don't use--probably about like your office
phone or cell phone. Usually, the crew just leaves them
configured in the Big Loop (with S/G 1) and they go to other
loops as they need. There is a way to call from one ATU to
another, but the crew isn't even trained to use it nowadays.

The ATUs were designed in the late 1980s. They were fairly
advanced in those days, but they are big and bulky by today's
standards. They do work, however. We have had two ATU failures
on orbit; they were both in the same location in the Airlock.


Yeah not much outside the telecom space and high end computers
used fiber optic in that time-frame. Any insight into what
caused those failures?


The Airlock is the only element with 3 ATUs. The reason
the Airlock needs 3 is that 2 of them are used for hardline
connections to two EVA-suited crewmen. This was a cheaper
solution than the creation of a unique interface box just for
the suits.


That makes good sense. Your photo site seems to be depicting
interoperability testing between the Russian comm gear and
NASA's, among other things. Was that the case?

If Jordan has any further questions, I'll defer them to him.

It was great to get to actually write you here, many, many
thanks for getting back to us.

Dave
  #13  
Old February 20th 10, 11:59 PM posted to sci.space.station
J. Porter Clark[_2_]
external usenet poster
 
Posts: 11
Default ISS ATU's (communication panels) need water cooling? Why?

David Spain writes:

(J. Porter Clark) writes:


Since the ATU in the cupola shares an equipment bay with several
other electronics modules (such as the one that controls the station's
robotic arm, etc.) I was wondering if you could tell us if the cold
plates are shared between the modules in the cupola or if there are
separate water lines running to each, such as one for the ATU, another
for the robotic arm controller [I have no handy acronym for that :-)]
etc, or if they share a common cold plate which water cools for
everything in the cupola?


The ATUs use the smallest ("-5") coldplates in the inventory.
As far as I know, nothing else uses them or even has the
same bolt pattern. The three ATUs in the airlock share one
big coldplate. None of the other ATUs share coldplates with
anything else. I don't know much about the ATCS plumbing,
except that Node 2 is unusual in that it has two completely
separate water loops. I was under the impression that the
coldplates are generally connected in series in any given area.
If I get a chance, I'll actually look at some diagrams. What is
the reason for asking?

The acronym you're searching for is RWS, Robotic Work Station.

What is that connector at the top of the ATU, designed for immortals
;-), actually for?


It's a test connector for factory use. The Harris documentation
gives names to the pins, but that's about it.

As regards the rear cabling, I'm guessing:


1. Left-most multipin connector looks like it loops pins to
possibly +V or GND. I'm assuming this is the addressing connector
and the connections are unique per ATU? In practice does this
allow an ATU to be swapped with any other ATU in case you have
a failure and can afford to sacrific one less used? Has that
ever happened on the ISS?


That is the address connector. The addresses correspond to
locations. You can swap ATUs from one place to another. As far
as I can remember, we've never swapped any audio boxes on orbit,
but we did swap that one ATU in the Airlock with a "new" unit
twice. None of the other audio boxes have failed, although
there have been some unexplained hiccups that have been cleared
by power cycling.

2. The middle connector has the 3 fiber optic communications links.
So what is up with that 3rd fiber? From your caption it sounds like
it is dark? Does it not exist in the flight configuration?


The ATU has 4 fiber optic connections: 2 in, 2 out. Redundant
buses. A common connector for both buses violates separation
of redundant paths, but not too much. 8-) We couldn't figure
any good reason for an ATU cable to have exactly 3 fibers.
Admittedly, it was a test cable of uncertain origin.

3. The bottom right connector is power? Are you running a standard
voltage on the ISS? Curious to know if it's 48VDC?


Like most Freedom-era boxes, and a good many later ones, it runs
on 120 VDC. ISS using 120 VDC instead of 28 VDC or something
else is of long and tedious history.

Does the cold plate attach on the finned side of the ATU?


No, it goes on the bottom, which is smooth and unpainted. The
fins (really pins) are on the sides.

Yeah not much outside the telecom space and high end computers
used fiber optic in that time-frame. Any insight into what
caused those failures?


I'd have to do some digging; it's been long enough for my aging
memory to forget. IIRC, they were from parts failures inside
the units. Because the first two units we put into that one
location both failed, albeit in somewhat different ways, we
spent some time proving that the location wasn't the problem and
that we wouldn't be wasting time and money installing a third
ATU there.

The Airlock is the only element with 3 ATUs. The reason
the Airlock needs 3 is that 2 of them are used for hardline
connections to two EVA-suited crewmen. This was a cheaper
solution than the creation of a unique interface box just for
the suits.


That makes good sense. Your photo site seems to be depicting
interoperability testing between the Russian comm gear and
NASA's, among other things. Was that the case?


Yes. The "Joint" Airlock was designed to be used with the
Russian and U.S. EVA suits. We were testing the hardline and RF
communication with both types of suits. All of the voice comm
with these suits ultimately goes through the ISS (U.S.) audio
system, so we were doing a dev test to make sure that everything
worked together. We ran many tests like that from 1994 to 2001.

The disappointing thing about the Airlock Mockup testing was
that the program decided not to fly some hoses or cables that
are necessary to use the Orlan in the Airlock. Therefore, much
of that compatibility testing was ultimately wasted. I do not
know if this situation was ever corrected.

If Jordan has any further questions, I'll defer them to him.


It was great to get to actually write you here, many, many
thanks for getting back to us.


My pleasure.
  #14  
Old February 21st 10, 02:20 AM posted to sci.space.station
David Spain
external usenet poster
 
Posts: 2,901
Default ISS ATU's (communication panels) need water cooling? Why?

(J. Porter Clark) writes:

...
anything else. I don't know much about the ATCS plumbing,
except that Node 2 is unusual in that it has two completely
separate water loops. I was under the impression that the
coldplates are generally connected in series in any given area.
If I get a chance, I'll actually look at some diagrams. What is
the reason for asking?


I was curious to know how the cooling to the cuploa was done where
there is a lot of equipment crammed into a small space with the windows
preventing plumbing and cabling runs any way you like and not a lot of
opportunity for ducting either.

The acronym you're searching for is RWS, Robotic Work Station.


Thanks!


What is that connector at the top of the ATU, designed for immortals
;-), actually for?


It's a test connector for factory use. The Harris documentation
gives names to the pins, but that's about it.


In other words, it's like that button with the label "DON'T EVER PUSH!"
;-)

Like most Freedom-era boxes, and a good many later ones, it runs
on 120 VDC. ISS using 120 VDC instead of 28 VDC or something
else is of long and tedious history.

OK, I *won't* ask, I'll wait for Jorge to write about it someday!
;-)

...


BTW, whatever happened with that hat? You didn't take into a
restaurant you didn't like did you? :-)

Dave
  #15  
Old February 21st 10, 06:26 AM posted to sci.space.station
Jordan Hazen[_2_]
external usenet poster
 
Posts: 12
Default ISS ATU's (communication panels) need water cooling? Why?

In article ,
J. Porter Clark wrote:
ATU power consumption when in full power mode is about 28 W.
This is just enough so that we can't count on ambient air to
keep it cool in zero G. All of the flight ATUs are on cold
plates. The mount in the Cupola is unusual in many ways.
There's a flight rule that allows the ATUs to run for some
period of time (IIRC, 30 minutes) without cooling water running.

The ATU was originally designed to allow for either cold plate
cooling or for ambient airflow at some rate and temperature.
That's why it has pin-fin heatsinks on the outside. However,
Boeing never found a good way to make the airflow method work in
any of their elements, and so it was abandoned.

ATUs sitting open in a rack in one G don't get hot enough to
need any help cooling, although the rack we usually put them in
for testing has fans in it.

The ATU features were the result of requirements from many
groups of people, and so it has a lot of buttons for features
that most people don't use--probably about like your office
phone or cell phone. Usually, the crew just leaves them
configured in the Big Loop (with S/G 1) and they go to other
loops as they need. There is a way to call from one ATU to
another, but the crew isn't even trained to use it nowadays.

The ATUs were designed in the late 1980s. They were fairly
advanced in those days, but they are big and bulky by today's
standards.


Thanks for all the interesting details.

I found a NASA photo showing the Cupola ATU in question just before
installation (taken around the same time as the video shown earlier?),
with its cold-plate and mounting bracket attached:

http://spaceflight.nasa.gov/gallery/...130e009537.jpg

This provides good frame of reference for the size and bulk. At least
they're not quite so *deep* as those non-flight units pictured in the
test rack on your web site.

They do work, however. We have had two ATU failures
on orbit; they were both in the same location in the Airlock.

The Airlock is the only element with 3 ATUs. The reason
the Airlock needs 3 is that 2 of them are used for hardline
connections to two EVA-suited crewmen. This was a cheaper
solution than the creation of a unique interface box just for
the suits.


Ah. I'd guessed as much from following the attached cables in
downlinked imagery...

--
Jordan.
  #16  
Old February 21st 10, 07:00 AM posted to sci.space.station
Jordan Hazen[_2_]
external usenet poster
 
Posts: 12
Default ISS ATU's (communication panels) need water cooling? Why?

In article ,
Jordan Hazen wrote:

Thanks for all the interesting details.

I found a NASA photo showing the Cupola ATU in question just before
installation (taken around the same time as the video shown earlier?),
with its cold-plate and mounting bracket attached:

http://spaceflight.nasa.gov/gallery/...130e009537.jpg

This provides good frame of reference for the size and bulk. At least
they're not quite so *deep* as those non-flight units pictured in the
test rack on your web site.


And after being mounted, in the lower-right corner of this image:

http://spaceflight.nasa.gov/gallery/...130e009694.jpg

It looks deeper from that angle. I wonder if those water loops will
be tucked more out of the way later, or if other equipment-- maybe the
robotic workstation when it's finally moved?-- will end up in front of
them).

--
Jordan.
  #17  
Old February 22nd 10, 10:09 PM posted to sci.space.station
Jeff Findley
external usenet poster
 
Posts: 5,012
Default ISS ATU's (communication panels) need water cooling? Why?


"David Spain" wrote in message
...
(J. Porter Clark) writes:
Like most Freedom-era boxes, and a good many later ones, it runs
on 120 VDC. ISS using 120 VDC instead of 28 VDC or something
else is of long and tedious history.

OK, I *won't* ask, I'll wait for Jorge to write about it someday!
;-)


It's been discussed in the sci.space groups in the past. Here's a hint: I
remember seeing posters in the EE building at Purdue talking about the 20kHz
power system for Freedom...

Here's a hit at NRTS:

http://ntrs.nasa.gov/search.jsp?N=13...ll&Ntt=2 0khz

Computer modeling and simulation of a 20kHz ac distribution system for
Space Station

Author(s): Tsai, Fu-Sheng; Lee, Fred C.
Abstract: A computer model of a 20 kHz, ac distribution testbed
for Space Station is presented. The system consists of six resonant
inverters, a one-hundred-meter transmission line, and three load
receivers: a dc receiver, a ...
NASA Center: NASA (non Center Specific)
Publication Year: 1987
Added to NTRS: 2004-11-03
Accession Number: 88A11827; Document ID: 19880024600

Granted the above isn't a history, but it does show how extreme the
"research" part of R&D was for portions of the Freedom program. Freedom
provided for lots of research "sandboxes" for people to play in. Not
surprisingly, when costs soared, schedules slipped, and NASA was forced to
redesign the station, many of these "sandboxes" quickly disappeared.

Jeff
--
"Take heart amid the deepening gloom
that your dog is finally getting enough cheese" - Deteriorata - National
Lampoon


 




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