Space Station Circuit Breaker Again Fails

[najab]

By MARCIA DUNN, AP Aerospace Writer <br /><br />CAPE CANAVERAL, Fla. - For the second time in just under a year, a circuit breaker failed on the international space station Wednesday, shutting down one of the gyroscopes needed to keep the orbiting outpost steady and pointed in the right position. <br /><br />The circuit breaker was a new one put in by spacewalking astronauts last summer. <br /><br />In a repeat from one year ago, the latest failure left the space station with only two functioning gyroscopes, the bare minimum needed for control, NASA said. This time, though, the problem could affect NASA's plans to launch Discovery to the station in mid-May after a two-year grounding of the shuttle fleet. The space station must be steady for a shuttle to dock. <br /><br /><br /><br />Yahoo! News link.

 

[CalliArcale]

I thought the station went into free drift before the Shuttle docks? No gyros, no thruster firings; just float passively and let the Shuttle catch it on its ODS.<br /><br />Now, obviously you do want it to be lined up favorably before you go into free drift, and you definintely need attitude control for that. But you can do that with Zvezda's thrusters too. (Although this really reminds me of the silly cost-cutting decision to cancel the Propulsion Module.) <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[mrmorris]

<font color="yellow">"...they had another circuit breaker failure<br />...Elektron ... and now is back down this morning. <br />...the toilet on ISS is broken "</font><br /><br />What will be very interesting to me if Bigelow is successful at creating a commercial space station is how MTBF will compare with that of the equipment on the ISS. Will equipment created without all of the reams of government specifications be <b>less</b> reliable, or <b>more</b> reliable? <br /><br />Only time will tell...

 

[shyningnight]

I suspect some of each.. (more reliable and less reliable).<br /><br />HOPEFULLY, the main difference will be that failed components will be able to be replaced, reengineered and replaced again, on a REASONABLE schedule rather than waiting years to be fixed.<br /><br />As you say.. only time will tell.<br /><br />Paul F.

 

[natrium]

Wouldn't it be easier if the circuit breaker would be located *inside* the ISS and not outside?<br /><br />Imagine you had to climb onto the roof of your house each time you had to reset a circuit breaker...

 

[CalliArcale]

I believe the circuit breaker is in the same module as the CMGs themselves -- the Z1 truss structure. This is a non-pressurized module located on the zenith ("top") side of the Unity node. Z1 contains the gyros and the various wiring neccesary for delivering power from the solar arrays to the station; it also carries ammonia coolant between the station and the radiators. There are also data connections. Lastly, it serves as a structural link between the pressurized modules and the truss which, when completed, will be the literal backbone of the station's power generation capabilities.<br /><br />So the circuit breakers can't be located in the pressurized section because their module doesn't *have* a pressured section. It's one of the consequences of modular design. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[nacnud]

The Z1 truss does not provide a structural link between the main truss and the habitable modules, the main truss is mounted on the destiny module, sorry to be picky but I was surprised to find that out because I thought the Z1 truss was mounted to the main truss as well.<br /><br />The Z1 truss hold the gyros and the P6 solar panel.<br />

 

[SpaceKiwi]

IIRC (and I frequently don't) the Z1 and attendant solar panels are to be relocated to the main truss at some point in future station construction, thereby freeing up the port on Unity for something else which escapes my memory at the mo'.<br /><br />I suspect that may be why the circuit breakers are located with the CMG's, rather than running cables from the Z1 into Unity and mounting the CB's there. ie, because the Z1 was always going to have 2 mounting points on ISS. <div class="Discussion_UserSignature"> <p><em><font size="2" color="#ff0000">Who is this superhero?  Henry, the mild-mannered janitor ... could be!</font></em></p><p><em><font size="2">-------------------------------------------------------------------------------------------</font></em></p><p><font size="5">Bring Back The Black!</font></p> </div>

 

[natrium]

Thanks for the explanation!

 

[SpaceKiwi]

Here's a couple for you ......<br /><br />Will the Z1 still house the CMG's, or are they going with the P6 to the main truss?<br /><br />Is there a usuable docking port underneath the Z1 mount-point on Unity, or is that area 'solid' because the Z1 was always going to live there?<br /><br />What happened to Z0?<br /><br /><br />(that last one was tongue-in-cheek) <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p><em><font size="2" color="#ff0000">Who is this superhero?  Henry, the mild-mannered janitor ... could be!</font></em></p><p><em><font size="2">-------------------------------------------------------------------------------------------</font></em></p><p><font size="5">Bring Back The Black!</font></p> </div>

 

[erioladastra]

"IIRC (and I frequently don't) the Z1 and attendant solar panels are to be relocated to the main truss at some point in future station construction, thereby freeing up the port on Unity for something else which escapes my memory at the mo'"<br /><br />Yes, P6 will be moved to the end of the Port truss, 15A I believe is the latest schedule.

 

[nacnud]

patatus <br /><br />Do you know if there are any free available plans/CAD models of the ISS anywhere. I was thinking that it would be far easier to understand what is happening on the ISS and how it is put together with decent reference matieral like this or this?