In article .com,
Ed Kyle wrote:
Other commercial launchers typically perform upper
stage burns at either perigee or apogee. What is
different about Zenit 3/DMSL?

This isn't the first time Sea Launch has used a somewhat puzzling mission
plan. My suspicion is that there are some obscure constraints on the
third stage which somehow dictate this. (There are some constraints on
fuel mass -- e.g., there has to be at least 2t left in the tanks for the
final restart, for some reason -- but they don't explain this.)
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |