The first time I did OS, there was a slow party starting up the original start that we bypassed by doing the RPM (or is it Remorse, I can never remember) start. They made it to Library Ledge by dark, and as we were walking out by headlamp we saw them rapping (by headlamp) straight down the face. From the evidence of their bail, it does seem like you can back off Outer Space with just one rope, as long as you don't mind leaving your whole rack behind.