Jerry Stuckle wrote in news:m35chg$mlv$1@dont-
email.me:

What would cause the superconductors to warm up? They have no
resistance, so it wouldn't be from internal means. And kept shaded,
there would be very little external heat applied.


Not much, maybe. I just figured that their state would not be stable, that it
would take very little, from any source, to heat them to the point where the
problem started getting rapidly worse. Maybe it wouldn't be an issue if the
superconductor were 'hot' enough. -196°C is 77°C above absolute zero, so
maybe some of them will always stay cold enough with nothing but shade.

Heat sources might be unexpected though. If a thin wire got hit my a
micrometeorite, it would likely get stretched and heated pretty fast. So the
question might be what kind of margins exist for safe operation.