If I recall that story correctly, this manual wasn't simply the result of working out math, like an artillery firing manual; it was the result of empirical expe

If I recall that story correctly, this manual wasn't simply the result of working out math, like an artillery firing manual; it was the result of empirical experimentation with no known pattern to it. The resulting trips certainly took them well across the universe and IIRC they weren't even entirely sure they were in the "same" universe because they were so far away they'd never correlated two known locations before.