wrote in message
...

All those failure modes and more can happen just as easily with
Progress, Soyuz or ATV. The HTV and future spaceraft like SpaceX's
Dragon only need to approach with the grapple range area of the SSRMS,
and hold still rather than continue to close in order to accompish a
docking. Once grappled, the spacecraft is inert and can be berthed on
a CBM port at the leisure of the station crew. So it seems to me to be
a far safer mode of docking a craft to the station, not less so. It
also confers a weight savings (no docking mechanism) and reduction in
systems complexity.

Also, docking with APAS is fairly violent when compared to the planned
grapple and (CBM) berthing procedure. I'm not sure about the other Russian
docking mechanisms, but I'd guess that they're fairly violent as well. You
need a certain amount of force to trip the "soft dock" latching mechanisms.

Both good things, plus we retain the ability to
move station racks and other bulky cargo through the large CBM
hatches. A capability that will be lost sadly when shuttle and the
MPLMs are retired.

Lost, but perhaps not for long. Space-X's Dragon plans to use CBM's and
should provide something like 7 to 10 cubic meters of cargo return
capability.

Jeff
--
beb - To paraphrase Stephen Colbert, reality has an anti-Ares I bias.