The F/A-18 isn't supersonic in those videos.
Yeah, we figured that out. I thought you were implying it was, since we were talking about shock waves. There are none in your video, except
possibly a weak shock attached to the horizontal stabilizer due to Prandtl-Glauert instability, but even that is hardly definitive.
Supersonic flight over ConUS is illegal except for testing.
No, actually there are established corridors for routine and even commercial supersonic flight. Nobody uses them much except the military, for obvious reasons. But surely the San Francisco Bay would not be in them, unless a special permit was issued. It could have been for an airshow, in theory...
The condensation wave and disturbance in the water surface is due to air flow over the airplane getting close to sonic. True supersonic flight would have the condensation begin -ahead- of the plane. The pilot would be concerned.
The last bit is wrong. Condensation ahead of the plane can only happen in subsonic flight, and will only happen very near the dew point. At supersonic, the wave cannot possibly precede the aircraft.
This is Darryl Greenamyer's Red Baron F-104 at Mach 1.28 flying over Mudd Lake Nv , October 1977.
Note the shallow angle of the Mach waves, with the first beginning at the nose, the rest from parts of the airplane.
The angle of the wave at Mach 1.00000 would be vertical at the nose, and departs from the vertical as the Mach gets higher.
The angle of the wave can be used to compute the speed.
And had the dreaded humidity been there...
Right. Exactly at Mach 1, assuming the shock is a
very strong one, the aircraft is basically keeping pace with previously generated waves. Thus the part of the bow shock travelling a tiny angle downward will eventually hit the ground just after the aircraft passes overhead. But again this requires a very strong shock. You can't really see this effect in your photos because the F-104 throws a relatively weak one, especially much higher than Mach 1. The effect is strongest at exactly Mach 1, and can be enhanced through maneuver.
The strongest effect, however, is the bow shock traveling straight to the ground, along the shortest path. This defines the trailing edge of the shock cone, and is at an angle of
θ = tan
-1 M, where M is the Mach number. This shock is a sharp expansion shock and normal to the ground, and therefore quite easy to see.
This also defines the minimum wing sweep for a supersonic aircraft. The aircraft must fit within its own shock cone, or else it incurs tremendous drag and thermal stress at speed. The only exception to this general design principle I can think of is the Space Shuttle, which is designed to dissipate speed through those mechanisms in the first place. [/GALCIT grad]
