ISS Solar Array Tear - What Next?

[JesseD]

The array is still running at 97% nominal production.  (as per MMT conference yesterday)  The problem is that with the tear, they can't put the normal 75 lbs tension on the array to stabilize and lock it.  hopefully the 'cufflink' fix will work!!

[Jorge]

Iren - 1/11/2007  4:08 PM

Thanks, I though that the russian segment, in the current configuration, could get the power they needed by itself... Then why Zarya's solar panels are retracted?

To provide clearance for the rotation of the S1 and P1 radiators.

[rocketguy101]

Chandonn - 2/11/2007 7:53 AM I would like to interject one observation about ISS from this flight. As some of you know, I'm one of those crazy people who updates his ISS model as the real ISS updates on orbit. On this flight, when P6 moved, it became VERY apparent how much ISS now dwarfs the shuttle. When Discovery undocks and does the fly-around, the shear size of ISS should be much more impressive than on previous flights.

Would it be appropriate for you to post a photo of your model in this thread?  It might help some of us to visualize where everything is in relation to the shuttle, etc.  I know this is for FD activities and updates, but it is hard for alot of us not intimately familar w/ ISS to grasp the size and location of everything, and we won't see the big picture until undock!!

 

[dmgaba]

I'm curious about the expected life-time of the SAW repair.  What analysis has been done about thermal cycling, sun exposure, etc. of the "cuff link" & wire fix?  That is, will it someday be necessary to install more per permanent load-carrying devices in place of the parts to be installed tomorrow?

[Mike_1179]

dmgaba - 2/11/2007  9:59 AM

I'm curious about the expected life-time of the SAW repair.  What analysis has been done about thermal cycling, sun exposure, etc. of the "cuff link" & wire fix?  That is, will it someday be necessary to install more per permanent load-carrying devices in place of the parts to be installed tomorrow?

The SAWs are designed for orbital replacement.  From what I understand, spare blanket boxes can be sent up on a later shuttle flight and stowed on one of the ESPs for installation after the shuttle is retired.  There's still the matter of jettisoning the current array, but that's another problem...

One problem is there are no spare blankets built yet.  The only "replacement" could be the 4A array packed up and ready to go on the S6 truss later next year.  The vendor would have to make up a new one and it would need a ride uphill somewhere in the future.

[ehartwell]

MacGyver challenge: Fix a space station using Sharpie, Ziplock bag, camera, vacuum cleaner, scraps (duct tape allowed).

The winning entry is covered in exquisite detail at collectSPACE,
http://www.collectspace.com/news/news-110207a.html

http://www.collectspace.com/images/news-110207a.jpg" align="right">"How exactly does one assemble a space station saving cufflink from spare parts? Very carefully, as appears to be the case in this, the seven-part instructions that were uplinked to the astronauts, complete with illustrations for key steps. Warning: it's acronym laden (e.g. FOD=foreign object debris, MCC-H=Mission Control Center-Houston) and with the possible exception of the ink marker and two ziplock bags, calls for items not usually found around the house, so it's probably best kids, not to try this at home."

[Zero-G]

There seem to be big concerns about the risk of an electric shock to the astronaut who will work on the SAW in order to fix it. The electrical tension in the SAW is 110 volts, is this right? How many amps does the SAW produce normally? I understand that the electrical power in the SAW cannot be switched off, because, by design, the array starts to generate electricity as soon as it is deployed (that's what it's there for, after all). So, here is my question: Would it not be possible to significantly reduce electrical power generation, maybe even below a safe level, by turning the SAW into a position where either the "backside" of the photovoltaic cells or the small edge of the SAW faces the sun, in order to avoid sunlight hitting the photovoltaic cells? If not, why?

(I am new to this forum and I hope this question has not been answered elsewhere.)

[rdale]

It's not really a concern - everything they've done in planning and toolmaking will insure that won't happen.

But even if it was a real risk, remember the ISS is orbiting. It's always moving with respect to the sun, so the SAW would be swinging around a lot. That makes the repair VERY difficult, because the SSRMS can't swing around in tandem.

So with electrocution not a concern, and no way to stop the sun :>, there's no need to turn the SAW.

[jeklund]

It sounds to me from what I have heard that they think they have the elecricity risk mitigated or understood pretty well, and don't think they need to do anything else.  They do, however need to keep the array in a position that will allow access, and provideplenty of sun for the OBSS sensors.   Dave Wolf sounds like it's not a big worry for him.  

[Speedracer]

Not sure about this, but if they are concerned with Scott getting zapped by juice from the array, then would it not be feasible for him to do the close-contact work during a night pass?  While I'm sure lighting is an issue, the lighting from his helmet should supply enough to work in the area, and the low emission of light from his helmet should be negligible regarding shock potential.

[rdale]

Once again - they aren't concerned about him getting zapped.

In any case, lightning is an issue.

1) He needs to see what he's working on, and what impact(s) it might have downstream.
2) EV2 needs to see him
3) ROBO & EV2 need to see clearances of the arm.

Once again - everything they are doing negates the risk of shock. There's no need to wait for night, and waiting for night is not helpful due to other reasons.

[Mike_1179]

I think everyone is so bent by the "electrocution hazard" because this is something that we can all understand and deal with here on the ground.  The risks for MMOD on their suits are always there when you step outside the hatch, but no one really talks about those because at home you never have to think about your clothes being pierced by something traveling at 12,500 mph.

It's not that much larger of a risk than much of the other risky things here, it just seems that way because we have a risk of electrocution in our homes

[Speedracer]

OK

[Zero-G]

Thanks for the replies. I do understand the SAW cannot swing around a lot during the repair and needs to be stable in an accessible position, but what I meant was a position which points the small edges of the SAW to the sun (instead of the full breadth) for most of the time during orbit, thus reducing power generation significantly. Or the array could be turned in a way that the cells face to earth most of the time.  But, if electric shock is not a concern anymore this may not be necessary anyway.
I know the crew would need as much light as possible to see what they are doing, but why would "plenty of sun for the OBSS sensors" be needed for the SAW repair? I thought they would use the OBSS boom just as a working platform with a foothold, to expand the SSRMS' reach in order to get access to the damaged area. The sensors themselves would not be needed for this task, would they? Besides, the work area (and the sensors) would be in the dark every 45 minutes anyway.

[Mike_1179]

If the sensors get too cold, they may break.  If they break, they can't be used to inspect the orbiter during the late inspection for MMOD after undocking.  

Also, the beta angle is still pretty high, so they will be in sunlight for much more than half an orbit

[chksix]

I hope they are developing an extension for the SSRMS that can be housed on ISS permanently. The need to reach further with the station arm may occur in the future also.

[Avron]

who said - "And Houston, just so you know, it was only one strand that was popped"..

I think we have a very high res pic of that "popped" strand coming down soon..  followed a few days by the actual strand..

(no idea what this is about. All is in the live flight day 13 thread. This thread is defunct now, so locking - James).