First thing 1.31 was Challenger Shuttle. 1.35, my Gen. 2 final upgrade. 1.4? My Gen. 3. Which was very close to SCS in fact. Pretty much the immediate predecessor. So what of 1.5? Of course... a successor to SCS.
The intermediate generations were not linear with the SCS line, but rather diversified. So, Gen. X (yes, it will be my 10th generation of shuttles...) will be a linear descendant of SCS.
