Henry:
We agree with respect to the horse you seem to be beating.
I am making a still larger point: dense spacecraft constellations intended
to last millennia are a bet against the Black Swan. It does not matter how
resilient such a system design might be, eventual failure is statistically
near certain.
Bill
On Tue, Mar 3, 2020 at 12:59 PM Henry Spencer <hspencer@xxxxxxxxxxxxx>
wrote:
On Tue, 3 Mar 2020, William Claybaugh wrote:
It looks to me that this scheme does not require a stupid mistake to
create a runaway chain reaction. It appears to initiate upon *any*
mistake, ever.
I was addressing a somewhat higher level: the stupid mistake is even
attempting such a scheme without incorporating generous margins against
such a perfectly-foreseeable problem.
Relying on a complete absence of errors is not realistic -- one of the
stupid mistakes we've made in spaceflight is building systems that fail
unless everything is done perfectly. What can be done is to fairly
reliably catch errors before they do harm, design the system so it can
usually tolerate the ones that slip through, have ways of limiting the
damage when even that fails, and learn from those cases so repetitions are
caught earlier. This is done, routinely, in many real-world technical
fields; it is not some unsolved mystery that is beyond our grasp. The
fact that we so seldom do things that way in space is our stupid mistake,
not a law of nature.
For example, any scheme with so many objects in similar orbits probably
wants a fast-response capability to *clean up* the debris from an
accidental collision, so it *doesn't* cause a runaway chain reaction.
(NB, in solar orbit, "fast" typically means months, not minutes. Even so,
yes, this probably means that the first responders need propulsion systems
that free them from constraints like launch windows -- it can't be done
with chemical rockets but there's nothing impossible about it.)
Kinda looks like a bad bet to me....
I quite agree that if it were built the way we usually build space systems
today, it would be a bad bet. But assuming that a project on this scale
would never even *try* to do better is silly.
Henry