What is the straight-and-level altitude record for a heavier-than-air winged/lifting-body aircraft?

Question

There are many variants of the flight altitude record. The highest on the list is SpaceShipOne but rocketry isn't really "flight" in the sense of aerodynamic lift. What is the highest altitude for which:

1. The flight at a reasonably constant speed and altitude "straight and level". It is not in free-fall, so the "cabin" feels about 1g.

2. It is "heavier-than-air" and supported by lift rather than buoyancy. The engine thrust's vertical component is much less than the weight of the aircraft, so the wings or lifting body have to support the craft.

3. The speed is slow enough that centrifugal effects are negligible (i.e. it is not in orbit). This is the case below about 2.5 km/s (about mach 8).

The highest on the list that may qualify is in a Mikoyan-Gurevich MiG-25 at about 36000 meters. However, it is not clear if this was at the top of a parabolic arc initiated at a lower altitude. The highest (including unmanned) that surely fulfills the above requirements is the Helios HP01 at almost 30000 meters. Edit: this number isn't reliable or believable.

Helios HP01, although very light, is a very low-power craft that only uses propellers. One would think (sc)ramjet-powered craft would win due to the high speeds needed to generate lift in such extremely rarefied air. Is this the case?

Answer 1

As of writing this, the official (as verified by FAI) "altitude in horizontal flight" category record goes to the SR-71 on 28 Jul 1976 at an altitude of 25 929 m (85 069 ft).

Second place is 24 463 m (80 259 ft) in a YF-12A, and third place is 22 670 m (74 377 ft) in a E-166 (modified Ye-152).

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For more: www.fai.org

Answer 2

Ymb1 mentioned the highest verified horizontal flights. Adding to their answer however, the following planes reportedly went higher:

• Brian Carroll said he flew an English Electric Lightning to 87,300 ft (26.6 km) MSL. From his description it seems it wasn't a zoom climb but an aerodynamic/horizontal flight:

"I once had an F-53 Lightning up to 87,300 feet over Saudi and it was really on a knife edge. Both engines remained alight, but were very touchy, and getting down to a more reasonable and sane altitude needed delicate handling. Earth curvature was visible and the sky was quite dark." Source

• The unmanned solar-driven propeller plane AeroVironment/NASA Helios reportedly achieved a peak altitude of 96,863 ft (29,523 m) MSL and spent more than 40 minutes above 96,000 feet. Since the Helios didn't shoot any images at its alleged peak altitude and having a maximum speed of 23.5 kts, these altitudes sound unbelievable, especially for a propeller plane.

• The unmanned scramjet NASA X-43A is said to have flown around 110,000 ft (33.5 km) MSL at almost Mach 10. Hence those would be the current horizontal altitude and airspeed records for a non-rocket airplane.

Answer 3

As far as one can trust NASA to be a reputable source, an A-12 registration 60-6932 operated by CIA flew at 90000ft on 14 August 1965.

There are unofficial accounts that the altitude record of A-12 is actually 94000ft (by A-12 and later SR-71 pilot Ken Collins), but I was unable to verify this. I am inclined to believe this may very well be true, as the 90k is a bit too round and nice of a number, and many of the documents concerning A-12 are still classified or even destroyed, as the Oxcart program was a very sensitive subject in its own time. It was deliberately intensely hushed out as the airforce variant SR-71 took over in late 60's, and as a less secretive and not as "politically incorrect" technological marvel, the "family model" was a perfect posterboy for intelligence supremacy of the U.S. It did not, however, match the performance of the smaller and lighter A-12.

Click here to download the NASA document containing information on the altitude records of the blackbirds (and more).