Thanks for the link. I didn't know they had a special test model ever get that high. A regular service duty, nah.
I agree, unless you strip a regular service tail of all unnecessary equipment it might do it, but then it would no longer be a line tail.
As an ex fuel guy I wonder what kind of mixture they were using. The SR-71 had to use JP-6 instead of JP-4 which needs more oxygen. All regular planes use JP-8 now. It's amazing they can change up the mixture to make it weigh less or have different vapor pressures.
At that time the USAF used JP-4 primarily. At high altitude the fuel freeze point becomes an issue. JP-4 has an extremely low freeze point (-58C) which is pretty good! Better than Jet A-1, JP-8 or JP-7 which the SR-71 used (-43C.) I’m not sure what the OAT is at 100,000 probably -40C on a standard day. You would have to cruise around a long time to affect your fuel temperature in your tanks. However, I don’t know much about aviation fuel or high altitude performance. The highest I ever cruised around at was 42,000 feet. A few times using JP-8 during the winter our fuel in the tanks dropped below freezing and began to clog up the filters, scary! We had to descend and accelerate to get the temperatures back to normal until the fuel warmed up and stopped bypassing the Filters and allowing ice crystals into the MECs.
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