On Apr 16, 8:30*am, Pat Flannery wrote:
Orion can carry six astronauts, Soyuz only three.
So you need two Soyuz to evacuate the whole ISS crew, but only one Orion.

Once Dragon (or one of its competitors) comes online, Russia would
presumably scale back its Soyuz flights so that there is only one
Soyuz docked to the station at any given time. Between one Dragon (7
crew) and one Soyuz (3 crew) I don't see a problem with evacuating the
six people on ISS.

Once upon a time there was a requirement for a dedicated ISS lifeboat
since crew transfer was originally to be handled by Shuttle. Since
the orbiter can't loiter at the station for six months, a separate
vehicle was needed for emergencies. Concepts ranged from (seriously)
confiscating two unflown Apollo vehicles from museums, refurbishing
them and docking them to the station, to the X-38. With the
replacement of Shuttle with vehicles that can be parked at the station
for the duration of its crews' mission, there doesn't seem to be a
need for a dedicated lifeboat.