Spacewalks Variations

On Oct 31, 5:33 pm, snidely wrote:
[...]
Here's an attempt at a verbal pictu imagine a stack of punch cards
(playing cards have too wide an aspect ratio -- the "cards" are long
and skinny).

Add hinges to opposite long sides so you have a Z-fold (or fan-fold if
you prefer). The "first" long side gets attached to a curtain rod,
and the "last" long side gets anchored in the box.

Looking at pictures like http://www.nasa.gov/images/content/
196032main_iss016e009207_hires.jpg, I'm amazed by how much flimsier
these are than I was thinking -- being used to consumer-grade PVs,
with lots of substrate and lots of support material.

Imagine the punch cards being shaved to at least 1/2 their original
thickness.

In fact, looking in the vicinity of the tear, it makes me think of the
woven/plastic tarp material at the auto supply or camping store.

And the repairs look a lot like a cable ties joined end-to-end to make
a 6-10 foot reach (2-3 meters).

/dps

On Thu, 15 Nov 2007 00:08:56 -0000, snidely
wrote:

On Oct 31, 5:33 pm, snidely wrote:
[...]
Here's an attempt at a verbal pictu imagine a stack of punch cards
(playing cards have too wide an aspect ratio -- the "cards" are long
and skinny).

Add hinges to opposite long sides so you have a Z-fold (or fan-fold if
you prefer). The "first" long side gets attached to a curtain rod,
and the "last" long side gets anchored in the box.

Looking at pictures like http://www.nasa.gov/images/content/
196032main_iss016e009207_hires.jpg, I'm amazed by how much flimsier
these are than I was thinking -- being used to consumer-grade PVs,
with lots of substrate and lots of support material.

Imagine the punch cards being shaved to at least 1/2 their original
thickness.

In fact, looking in the vicinity of the tear, it makes me think of the
woven/plastic tarp material at the auto supply or camping store.

And the repairs look a lot like a cable ties joined end-to-end to make
a 6-10 foot reach (2-3 meters).

/dps


Oh yeah. These are not Earth-grade solar panels with thick tempered
glass and aluminum frames. That Kapton is thinner than Scotch tape...
(although there are at least several layers of it).

Keep in mind that these have been highly optimized, mostly for
performance *per pound*. Durability, size, output power, cost, etc.
Everything is a tradeoff in space.

The amazing thing is that they are streched with, what, 70 lbs of
tension, when fully furled. Given that P6 had other problems after
being retracted after several years, including the frayed retraction
cable, I am rather surprised that they didn't have more problems than
they did.

--
Bob the Tomato