LIVE: STS-120 Flight Day 10 - MT/OBSS Ops - EVA-4 Preps

[steve_slitheen]

ckiki lwai - 1/11/2007  7:54 PM

mwfair - 1/11/2007  7:45 PM

As stated in the MSB, the array can't be safed, the cells produce voltage when light shines!  However, they have 45minutes of no light, so can Scott touch the array during orbital night?

Your question got answered
He says the protection is adequate so he sees no reason not to continue the activities in daylight

edit:spelling

So what kind of voltages and currents are we talking about here?

[DwightM]

ShuttleDiscovery - 1/11/2007  10:43 AM

Chris Bergin - 1/11/2007  7:42 PM

Right now, no EVA-5, undock FD14. If the repair is not successful, look at consumables, maybe do a short EVA-5.

I guess there can be less time between EVA-4 and 5 as it's by Peggy and Yuri, correct?

They aren't referring to the original EVA-5 in this case, they're talking about a repair follow-up if the initial repair isn't successful.  As for who would go, that would be TBD.

[kimmern123]

Yes, that's the plan, with a late afternoon landing.

[mwfair]

I find this whole topic of the problem at hand, this repair, and especially this briefing,  to be a good counterpoint to the cry for 'robotic exploration only'.  Seems to me this sort of situation is inevitable in any complex mission.  
Looking at the procedures sent to ISS for fabricating the cuff links, its amazing to see how much general use equipment and kits full of random parts are stored on station.  hundreds of pounds of stuff waiting, just like I have in my garage, 'in case I might need it someday'.  Seems like that sort of thing is neglected by many analyses of 'better' systems for VSE.  I for one easily forget how much contingency is needed in any mission design.

[hutchel]

steve_slitheen - 1/11/2007  3:02 PM

ckiki lwai - 1/11/2007  7:54 PM

mwfair - 1/11/2007  7:45 PM

As stated in the MSB, the array can't be safed, the cells produce voltage when light shines!  However, they have 45minutes of no light, so can Scott touch the array during orbital night?

Your question got answered
He says the protection is adequate so he sees no reason not to continue the activities in daylight

edit:spelling

So what kind of voltages and currents are we talking about here?

I heard him say - think it was 100 VDC - no mention of AMPS though - Remember Volts don't kill Volts with sufficient AMPs kill.

Lee

[ChrisC]

ngilmore - 1/11/2007  2:53 PM
Since the SRMS can normally take out the OBSS

Stop right there, it can't.  Lately this is FAQ #1   Do some searching in this forum or the web in general.  Hint:  PMA2 and Destiny obstructions.

FAQ #2 is "why is Harmony in a temporary location?"  :/

[AnimatorRob]

ngilmore - 1/11/2007  2:53 PM

Robotic ops: SSRMS to move from work station 8 to work station 3. Will pick up OBSS. Will hand off to SRMS so it has power. Will translate back to work station 8. Will pick up OBSS from SRMS.

My question: Since the SRMS can normally take out the OBSS, and since according to this plan it can hand off to the SSRMS at work station 8, why does the SSRMS mobile transport have to move back and forth in the first place. What constraint prevents the SRMS from taking the OBSS out on its own?

I would have to guess there are clearance problems with grasping the OBSS with SRMS while docked.

- Oops, Chris beat me to it.

[uko]

Probably this is explained somewhere already, but I cant find it.. so I wonder where are the holes, they push the cufflinks thru? I dont remember seeing any holes in the solar array blankets, so do they cut the holes themselves?

[Chris Bergin]

uko - 1/11/2007  8:33 PM

Probably this is explained somewhere already, but I cant find it.. so I wonder where are the holes, they push the cufflinks thru? I dont remember seeing any holes in the solar array blankets, so do they cut the holes themselves?

We have a big set of super hi res images on L2 showing how this will be done. I'll share one here:

[mwfair]

hutchel - 1/11/2007  2:12 PM

steve_slitheen - 1/11/2007  3:02 PM

So what kind of voltages and currents are we talking about here?

I heard him say - think it was 100 VDC - no mention of AMPS though - Remember Volts don't kill Volts with sufficient AMPs kill.

Lee

True, but I = V/R.  In this case, R is 100kohms on a good day for human body, up to 1000 ohms for someone who's been sweating.  This could result in up to 100mA, which is enough to cause a muscle spasm.  
They aren't joking when they talk about not touching the array.  Thats why they are using 18 inch needle nose pliers, taping everything, and not even thinking about moving from one side of the solar blanket to the other (hence to cuff links).

[mwfair]

Chris Bergin - 1/11/2007  2:38 PM

uko - 1/11/2007  8:33 PM

Probably this is explained somewhere already, but I cant find it.. so I wonder where are the holes, they push the cufflinks thru? I dont remember seeing any holes in the solar array blankets, so do they cut the holes themselves?

We have a big set of super hi res images on L2 showing how this will be done. I'll share one here:

The existing holes can also be seen (almost, they are obscured by the glare and low contrast) in the  hi-res images of the tear, e.g in post 206351.  (Thanks, Rich, I hadn't seen them till you pointed them out.)

[swhitt]

Remember Volts don't kill Volts with sufficient AMPs kill.

True, but I = V/R.  In this case, R is 100kohms on a good day for human body, up to 1000 ohms for someone who's been sweating.  This could result in up to 100mA, which is enough to cause a muscle spasm.  

Scott will be insulated inside the space suit. The bladder alone would take the hit, let alone the layers of mylar and other materials. While human shock is important to prevent, I don't think it is the main issue.

The problem I would think is spiking the control circuits of the suit, or the spike travelling down the OBSS and tagging the SSRMS control circuits.

Then who knows how far up the chain the burnouts would be.

Shut down the suit and the SSRMS and you have a totally different problem.

[Mike_1179]

mwfair - 1/11/2007  3:44 PM

Chris Bergin - 1/11/2007  2:38 PM

uko - 1/11/2007  8:33 PM

Probably this is explained somewhere already, but I cant find it.. so I wonder where are the holes, they push the cufflinks thru? I dont remember seeing any holes in the solar array blankets, so do they cut the holes themselves?

We have a big set of super hi res images on L2 showing how this will be done. I'll share one here:

The existing holes can also be seen (almost, they are obscured by the glare and low contrast) in the  hi-res images of the tear, e.g in post 206351.  (Thanks, Rich, I hadn't seen them till you pointed them out.)

The holes were used to keep the blankets in their boxes during launch.  Back on the ground, the blankets were folded up in the boxes like an accordian.  There were holes along the blankets that lined up when they were folded and these holes are reinforced with aluminum.  When in the boxes before launch, a large pin was placed through the boxes and through these holes in the folded blankets to take up and shear loads from the vibration of launch.  One of the first steps before they were unfurled was to retract these pins.

It's just lucky that the blankets have metal-reinforced holes in each panel that were made to faciliate a launch restraint.  I guess it's lucky the same way that they have an OBSS to use as a work platform too...

[MKremer]

uko - 1/11/2007  2:33 PM

Probably this is explained somewhere already, but I cant find it.. so I wonder where are the holes, they push the cufflinks thru? I dont remember seeing any holes in the solar array blankets, so do they cut the holes themselves?

It was mentioned in yesterday's briefing - there are pins in the blanket boxes that fit thru the holes to help stabilize the folded blankets during launch. Then those pins are permantly retracted before the blanket box is unlatched and extended once the array is installed.

[stockman]

Ok I have a question on the repair effort spacewalk planned for saturday. Its apparent that one of the astronauts will be on the boom doing the physical threading of the cufflinks as they are called with the array. My question is what is the Role of the second spacewalker throughout this period? Is he simply a passive observer for safety sake or is there an integral role for him to play during this repair? Thank you in advance

[steve_slitheen]

Lee[/QUOTE]

True, but I = V/R.  In this case, R is 100kohms on a good day for human body, up to 1000 ohms for someone who's been sweating.  This could result in up to 100mA, which is enough to cause a muscle spasm.  
They aren't joking when they talk about not touching the array.  Thats why they are using 18 inch needle nose pliers, taping everything, and not even thinking about moving from one side of the solar blanket to the other (hence to cuff links).[/QUOTE]

OK, but what's the resistance of a spacesuit?  Surely the astronaut is well insulated by the suit, and the suit surface is dry.  Or is it conductive?

[DaveS]

steve_slitheen - 1/11/2007  9:03 PM
OK, but what's the resistance of a spacesuit?  Surely the astronaut is well insulated by the suit, and the suit surface is dry.  Or is it conductive?

It's conductive as there's a number of metal surfaces both on the outside and inside of the EMU.

[DwightM]

stockman - 1/11/2007  12:03 PM

Ok I have a question on the repair effort spacewalk planned for saturday. Its apparent that one of the astronauts will be on the boom doing the physical threading of the cufflinks as they are called with the array. My question is what is the Role of the second spacewalker throughout this period? Is he simply a passive observer for safety sake or is there an integral role for him to play during this repair? Thank you in advance

EV2 will play a critical role during SSRMS ops & the repair to watch guidance & clearance issues.  It's unlikely he'll be doing much else.

[sqoops]

DwightM - 1/11/2007  4:10 PM  

EV2 will play a critical role during SSRMS ops & the repair to watch guidance & clearance issues.  It's unlikely he'll be doing much else.

Aren't two EVs always required anyway, in the frightening case one must assist another?

[swhitt]

DaveS - 1/11/2007  1:10 PM
It's conductive as there's a number of metal surfaces both on the outside and inside of the EMU.

Yes, but are they connected? If they are electrically connected, then they would be thermally connected as well. That would kind of negate one of the purposes of the suit wouldn't it?

Insulated metal surfaces do not conduct electricity.

I think the water cooling would conduct, but only if there is a leak inside the suit.