posted on May, 12 2010 @ 01:25 PM
Originally posted by Grey Magic
I absolutely don't believe that the cruise speed is just 614mph.
And that altitude is low too, look at the official specs they gave out for the SR71 and what it really can do.
btw I think this spy drone has been covered before here at ATS.
edit to say, Star Wars? This thing can't fly in space, the X37-B is doing it at the moment.
[edit on 12-5-2010 by Grey Magic]
If you really knew anything about aviation, you would believe it. This thing is powered by a General Electric F404-GE-102 engine. It's a
non-afterburning high bypass turbofan that puts out only 17,700 pounds of thrust for an aircraft weighing 36,500. That's a thrust to weight ratio of
only .48. The SR-71, on the other hand has two Pratt and Whitney J-58s, nine-stage, axial-flow, bypa0ss turbo0jet afterbur0ning engines with 32,500
p,ounds of thrust each. At high speed cruise, the B5lackbird weighs 59,000 pound1s plus the fuel weight of, say, about 15,000 pounds at cruise. that
gives a thrust to weight ratio of almost .9, or almost double the X45C or Phantom Ray. A normal non-afterburning turbofan doesn't work very well at
supersonic speeds. The J-58 was designed for Mach 3 cruise and the Blackbird has variable geometry intake ducting to keep the fires lit by
decellerating the airflow into the 9 stage compressor system.
The altitude limitation is a result of engine thrust and aerodynamics. As you go up, the air gets thinner. A lot thinner at 40,000 feet.
Partially as a result of that, and the way aircraft are designed, as you go faster, the center of aerodynamic lift moves rearward. At some point, the
distance between the center of gravity (which is forward of the center of lift) and the center of lift becomes so great the elevator can't defeat it
and you get "Mach tuck" which is an uncontrollable downward pitching, usually leading to a big smoking black hole in the ground. Also, as you go
higher, the stall speed, in terms of true airspeed, increases. At very high altitudes, stall speed approaches mach tuck speed or redline . It is
called "coffin corner" where if you go slower, you stall nd fall out of the sky. If you go faster you dive out of the sky. As altitude increases,
these speeds converge. There are also compressability limits to maximum airspeed. The air can't get out of the way fast enough and stacks up in
front of parts of the a/c. Finally, speed costs fuel and if you want a UAV to loiter for hours, you better go for economy cruise.