Re: A venerable workhorse
"But if NASA needs to replace the SOFA jet, they can just chop the fuselage of any large twinjet, and get the same effect."
Not quite. The SP has a _huge_ tail in order to cope with engine-out conditions (shorter distance between engine and empenage == smaller moment of force unless the rudder is made bigger)
That huge tail requires a bunch of structural mods at the back end of the aircraft. You can't just shorten an aircraft and plonk on a larger rudder. (unlike lengthening one, where the larger tail is normally left intact as it's too expensive to resize it)