On Wed, 08 Oct 2003 01:51:35 GMT, Jim Thomas
wrote:

I hadn't read this post at my last reply. This description sounds
accurate for the Streak Eagle flights. I'm still not sure that the
aircraft accelerated through Mach 1 in vertical flight; it sure could
have, if it did so during an Immelman!

Jim Thomas

Guy Alcala wrote:

Ed Rasimus wrote:

Now, let's put to bed this idea of accelerating through the mach
straight up. While modern jets with greater than 1-to-1 T/W ratios can
accelerate through the vertical, I sincerely doubt the mach claim. Too
much is going on with drag curves, deteriorating performance with
altitude, losses in engine efficiency, etc. I think only heavy lift
rockets accelerate through the mach in near vertical, but they
transition out of vertical fairly early in the flight trajectory and
may not be vertical either.


Oh, I don't know. While not a stock production a/c, the Streak Eagle was
certainly capable of doing so [From Jeff Ethell's book on the F-15]:

"The 3,000m record flight was piloted by Maj Roger Smith. With a
thrust-to-weight ratio at release of over 1.6 to 1 the 'Streak Eagle' lifted
off the ground after a roll of only 400ft, approximately seven airplane
lengths. Smith quickly raised the landing gear and maintained nearly level
flight while accelerating to approximately Mach 0.6. The aircraft was then
rotated by a 5g pullup to a near vertical climb attitude. The Eagle
accelerated during this climb to Mach 1 and reached the specified 3,000m
altitude in 27.57 seconds.
Guy

---remainder of detail on a great aeronautical achievement snipped--

First, let me note that I'm a political scientist by education and a
military aviator by choice. I'm not an engineer or mathematician (but
I did stay in a Holiday Inn Express last night.....)

As I recall, the first integral of velocity is acceleration. The
second integral would be rate of change of acceleration. Therefore
(without doing the math), if one were accelerating horizontally at a
high rate and then transitioned into the vertical, the addition of the
gravity vector to drag--i.e. directly in opposition to thrust, would
result in a rapid decay of the second integral--positive rate of
change of acceleration. Acceleration would slow down, although still
be increasing speed; merely at a slower rate of increase. Therefore
you might pass through the Mach while in the vertical. Note also that
the relationship between the Mach and IAS is shifting rapidly as
altitude increases. Mach 1 becomes a lower and lower IAS.

The "fastest way to Mach II" used to be the Rutowski profile. Takeoff
and accelerate to .9 mach on the deck. Hold .9 mach and transition to
climb until .9 mach intersects some airspeed (I think it was about 400
or 450 kts, but am not sure--it was a long time ago.) Then hump over
to allow the aircraft to accelerate to 1.2 M. This usually took place
at around FL 210 and resulted in a slight descent to about FL 180. At
1.2 M, establish that IAS and maintain the climb on IAS until reaching
Mach 2--usually around FL 450. The amazing thing was the sensation of
"the faster you go, the faster you go faster!" The acceleration on
takeoff from about 400 kts IAS until reaching .9 near 600 kts was a
kick!

My point remains. If you established vertical at a given subsonic IAS,
then selected reheat, I continue to doubt that the aircraft could
accelerate through the mach. It's an entirely different dynamic
situation than the Streak Eagle profile.