JF Mezei wrote:

On 2017-02-01 21:46, Vaughn Simon wrote:

One thing though, ten identical birds at one time, with all of them
belonging to the same company, sounds like a huge crap shot to me. They
could all be lost in a single launch failure, or (being identical) they
could all share the same technical problem. Putting up a few at a time
via shared launches sounds a whole lot safer.


Iridium is launching a whole bunch of satellites on a limited number of
orbital planes. The 10 were launched on an 86° orbital plane (aka polar
orbit) and would be spaced out on the same plane. So it makes sense to
launch them at same time.


Right. Iridium has gone through and optimized the number of launches
they need to replace their constellation. It turns out to be a number
of 'sets of 10' launches with some 'sets of 4' launches to fill in the
gaps.

The idea is to have enough 'spares' in the build pipeline to be able
to slot them in for a bad launch and be able to use the insurance
money to build replacement birds for later in the launch sequence. So
as long as you stay 10 birds ahead in construction, you're good as
gold.


--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw