Interesting Altitude Attempt.
I did a quick internet search and I think the official altitude record for an air breathing aircraft taking off from the ground is held by a modified F-104 Starfighter at around 103,000 Ft. This was set in the early 60's and I guess indicates some potential for rich guys or companies to set some new records in this area. Record setting attempts get somewhat muddied regarding altitude, powerplant, [airbreathing or rocket] and other issues. Apparantly, NASA'S rocket propelled Starfighters were reaching around 120'000Ft in the mid sixties, but they had thrusters to control pitch and roll at high altitude. The air breathing aircraft would start their record breaking attempts from a high mach level flight probably around 35'000 t0 40'000 ft then pitch up an optimum angle [maybe 45 deg?] then continue upwards to an engine flame out point [guessing around 65'000ft] then coast upwards from there. Interestingly, the Starfighter took the high altitude record away from a Navy F-4 Phantom. [around 98'000ft] The low altitude record is even more muddy, but I think a modified F-104 Starfighter holds this at around 988mph. [Daryl Greenamayer] I'm not sure how low the low altitude record has to be[how low is low?] but it is very difficult to overpower the air resistence at low altitude so the older small wing high speed fighters are probably hard to beat in this regard. I recall a good book [not Thud Ridge] where a USAF pilot was describing his exit from North vietnam at low level in an f-105 Thunderchief. Hard on the deck and pounding on the throttle, 1000mph indicated airspeed! So the F-104 has a rival and maybe someone will prove it some day! As for the record in the Vigilante, I would consider it a good contender for a high altitude attempt, [for real !] However, stability is a real concern at these altitudes. Regards.