There are an infinite number of possible orbital planes in low Earth orbit,
and ISS occupies only one. It is prohibitively expensive, fuel-wise, to
change planes once in orbit. Requiring that all manned spacecraft be able
to abort to ISS is tantamount to demanding that all manned missions be
planned for ISS in the first place. It is thinking such as yours that got
the Hubble servicing mission cancelled. It is thinking such as yours that
would prevent us from ever returning to the Moon, or travelling to Mars.



Yep. I can see the ISS has only one orbital plane. So, what is so wrong,
to require all manned spacecraft be able to abort to the ISS? Demanding
that all mannned missions be planned in some way for ISS? Hubble is
near it's end. And who's planning a return to the moon, or a trip to
Mars?
'Prohibitvely' expensive? Here's who died during STS-107:
Rick D. Husband
William C. McCool
Michael P. Anderson
David M. Brown
Kalpana Chawla
Laurel Blair Salton Clark
Ilan Ramon
Jules F. Mier, Jr.
Charles Krenek

Put as many words you want in front of 'expensive'. I don't care about
the hardware cost. How can you tally, those lives, vs. cost? Send them
up; then give them a lifeboat.