Here MiG-25 goes again... mixture of old 70-80'es data.

The story about burning engines is from that date. The published story is
that test-pilot Bezevec on the pre-production MiG-25R went beyond M3 because
he was painted by Hawk missile radar. In that time '25 was still in
test-phase with limited max speed endurance and when arrived to Egypt it was
just cleared from 3min flight to 8min. While in Egypt, it was cleared
further to 40 min up to unlimited when necessary. MiG-25 engines have
Chekunov's electronical system for fuel and engine RPM management-the FADEC
forerunner. There was a MiG-25 version that could "normally" travel up to
M3.2 known as MiG-25M, but was abandoned late in development in favour of
MiG-25MP (known as MiG-31 today). However, it was this MiG25M prototype that
under a "official" name tangled with F-15 Streak Eagle in speed, height and
speed to height records.

Cruising speed (in terms of best range/perfomance/economics) is around 2.500
km/h, NOT M 0.85-it is another blunder or a mix-up with MiG-31 (MiG-25
RB-15-300 engines are awfully inefficient subsonically). Another mix-up or
disinformation is that MiG-25 cannot travel more than M 2.3 with four R-40
missiles-actually, it can carry them up to the placarded (M 2.83) limit
(MiG-25P/PD/PDS interceptors) or even four 500kg bombs (RB/RBS/RBT
recce/strike versions) up to that speed. The speed of the MiG-25 at
low-level is limited by a pressure that is simply too high at such low
altitudes, so the temperature at the inlet (as well as in the engine) raises
above limits.

Although MiG-25 looks ordinary and extremely "boxy", its shape is very
efficient for high-mach regime. It is a different approach than one in
SR-71. While SR-71 had fuel tanks that got sealed by the airfame stretching,
MiG-25 has inboard tanks separated from the airfame-just like a car fuel
reservoirs (with a difference that it's tanks are pressured, filled with
inert gas and cooled).

MiG-25 can produce up to 5g (or 5.5) in supersonic regime. Sustained
altitude is around 20,000 m. SR-71 can manage around 2g (which is no
discredit, because it was not necessary for SR-71 to turn better).

Now, comparing MiG-25 and SR-71 is comparing apples and oranges. MiG-25
project was initialized to -counter- a Blackbird (not Valkirye as many
sources described!). Later (but early in develoment), it was "split" to
produce both inteceptor and recce variant . SR-71 is strategic recce
aircraft (although it evolved from A-12 that further produced a basis for
both SR-71 recce aircraft and YF-12 interceptor). MiG-25 is quite limited in
range, SR-71 is not. SR-71 had much wider and sophisticated recce equipment
than MiG-25R and could travel at M3+ until ran out of gas. MiG-25 was
produced massively (in order of around 600 aircraft), SR-71 just a handful.

Nele

NULLA ROSA SINE SPINA


Ragnar wrote in message ...

"Vello Kala" wrote in message
...
Aircraft Speed Altitude Mach Number
SR-71 Blackbird 2,275 mph
(3,660 km/h) 80,000 ft
(24,385 m) Mach 3.35
MiG-25 2,110 mph
(3,390 km/h) 42,650 ft
(13,000 m) Mach 3.2


This data is from Aerospaceweb. Question: SR-71 looks like alien plane,
have
very special design (incl tanks what start to keep fuel on flight
only)etc
etc. Mig-25 looks as pretty usual plane. But difference in speeds is
relative minor, expecially if to look at what altitude it is reached. How
it
is possible? Do anybody have more data? Say, about SR-71 performance at
40
000 feet?

You only think the engine performance is similar. The SR-71 could maintain
Mach 3-plus for several hours at a time, but the MiG-25 could do mach 3.2
for only about 5 minutes before burning the engines up.