I found this on sci.military, and it might be of interest to the vehicle/
a-c design crowd. It looks like the Traveller method of speed as a direct
function of TtW is bogus.
- -bertil-
sci.military (moderated) #16537 (8 more) (1)--(1)
From: Henry Spencer
[1] Re: Mig-25
Date: Mon Mar 2 05:15:54 1992
Organization: U of Toronto Zoology
>From [email removed] (Henry Spencer)
>From [email removed] (Phoenix)
>BTW, how come Mig-29, with only 2 18400 lbs thrust engine could
>achive the speed of Mach 2.4, I mean, I always thought the fighter
>speed has something to do with it's Thrust:Weight ratio, but
>what I seen is that some plane with lower than 1.0 ratio could
>fly faster than a F-16 (Mach 2.1+)...
The top speed of a fighter is set by any of several considerations.
Simply running out of power is only one possibility. The reason the
F-16 is limited to about Mach 2 maximum is that efficient engine
operation at higher speeds requires variable geometry in the air intakes,
omitted on the F-16 because it costs weight, money, and reliability.
Another common limitation is overheating in some area -- the canopy,
the nose structure, or the engine, for example. Heating starts to
become troublesome shortly after Mach 2, and beyond about Mach 2.5
you need drastic measures like wholesale use of titanium.
With good aerodynamics and variable intakes, the T:W ratio doesn't need
to be all that high to run you up against thermal limits. The F-106
set a world absolute speed record at circa Mach 2.5, and several other
fighters of that vintage routinely hit temperature limits in that
vicinity while still accelerating fiercely. If memory serves, even the
SR-71's T:W ratio is nowhere near the F-16's.
- --
The X Window system is not layered, and | Henry Spencer @ U of Toronto Zoology
it was not designed. -Shane P. McCarron | [email removed] [email removed]