If Congress had coughed up the money to keep Project Apollo
going into 1973-1974 [Apollo 18, Apollo 19, Apollo 20], then
it is quite likely that an Apollo crew would have died...
from radiation poisoning.

Most likely it would have been Apollo 18 that would have faced
such a tragedy....due to a solar flare.
I believe August, 1973 was to be the month that NASA
'wished' it could have carried out such a mission.
[Jim Oberg may disagree with this viewpoint]

But we know now that in August of 1973 there was a
potentially deadly solar flare that month.
The hypothetical Apollo 18 crew would have suffered
an agonizingly slow death if it's crew had been blasted
by its effects. [The Skylab crew was 'safe' within
Earth's magnetosphere at the time].

Sad to say, NASA has said little about Project Orion
and the threat it faces from solar flares.