I specificly said the MAJORITY of the time, not all the blackbird's operational time.Simply not true, which you would know if you'd have studied SR-71 operations more closely. There was at least one incident where an SR-71 "accidentally" strayed deep into Soviet airspace and PVO went NUTs trying to intercept it.
You are reffering to the belenko's story. Well, I'm well aware of his "work", however, some of the things he "said" were proven wrong(like the actional radius or the engine overrpm problems). What he said for sure we will never know. Maybe some things were "corrected"...Who gives a shiit if YOU find it unworthy of discussion? A mig-25 pilot stated emphatically that the SR-71s closure rate was simply too great for the Mig25s onboard fire control computers to calculate.Unless YOU are a Mig25 pilot, your opinion on this matter is QUITE irrelevant to the stated facts.
Regardless, Mig-25s lacked the performance(specifically the range) to intercept blackbirds anyway, so it's irrelevant.
Now the Mig-31 is an entirely different story, but you said Mig25
MiG-25 had the option of using a rather large fuel tank to increase its range. And you should also remeber that even civilian traffic radar maneged to track blackbird 500 km away. If this would be the same for the russian military radars, I think that MiG-25(or better to say MiGs) would have more than enough time to position itself in the optimum intercept position even if it meant that at the time the migs were on the ground(they can reach altitude of 20 000 m in some 3-4 minutes fully loaded). So, by the time MiGs reach the disigned altitude, blackbird will be some 300-400 kms closer(at speeds of Mach 3 or greater, and I've added some time for the take-off of the MiGs which is quite doubtfull since probably there were atleast some foxbats on patrol duties). Offcourse, the blackbird could easily change the course, but that would mean its mission could not be completed, and that was exactly what the MiGs were used for. If the MiGs were serious, Blackbird would find itself in problems. The R-40, carried by the MiG is a mach 4+ rocket, and I believe its range is around 25-30 miles. Jamming the MiG would also be quite difficult, since its radar could pretty much fry the electronical installations of a smaller city(one note here also, some people have said that during the operation desert storm in the early 90's, possibly the only aircraft which could get some kind of an radar echo at smaller distances from an F-117 was the Iraqi MiG-25, due to its powerfull radar).Doesn't matter. It's an issue of Kinematics. The Mig's simply lacked the legs(the range) to get into proper intercept positions in time.
In my first post on this subject I also wrote some quotes from the MiG-25/31 books that stated that there were even more powerfull engines available at the time, that would have given the MiG greater speed(up to Mach 3.5) and range. The russians, however, were confident that the MiG was quite able of doing the designed mission, and USAF was quite aware of it also, as no flights were made in the close proximity of MiG-25 bases(even after Belenko "switch sides").