Refuting blackbird folklore

There was a time when I thought that
the blackbird could secretly hit 5 on the
mach meter--but isn't there solid science
agains this? Such as:

I don't think the engines have the ability
to rev up to such a speed. Maybe the jet fuel
itself cannot produce sufficent BTU's (thrust)
to propel it that fast, maybe the fuel lines
are too small to exceed Mach 3.3

Perhaps the real inhibitor is the lack of
enough combustible oxygen to feed the engines
to shatter established speed records.

I know that the outer metal shell of the
jet couldn't sustain the high atmospheric
friction.

Am I right about all this, or is there OTHER
things to consider?

In article ,
(frank wight) wrote:

There was a time when I thought that
the blackbird could secretly hit 5 on the
mach meter--but isn't there solid science
agains this? Such as:

I don't think the engines have the ability
to rev up to such a speed. Maybe the jet fuel
itself cannot produce sufficent BTU's (thrust)
to propel it that fast, maybe the fuel lines
are too small to exceed Mach 3.3

Perhaps the real inhibitor is the lack of
enough combustible oxygen to feed the engines
to shatter established speed records.

I know that the outer metal shell of the
jet couldn't sustain the high atmospheric
friction.

Am I right about all this, or is there OTHER
things to consider?

A lot of that is pretty much on the mark. I've heard Mach 3.5 for short
sprints, but not more than 3.3 for sustained flight.

Mach 5? No way in hell, although I've seen a very few claims for Mach 4
sprints (extremely informally on that one). Even if they could manage
the power to do it, the skin would be melting (see the thread on the
Sanger Amerika Bomber for some of the problems with sustained very high
speed flight).

--
cirby at cfl.rr.com

Remember: Objects in rearview mirror may be hallucinations.
Slam on brakes accordingly.

In article ,
(frank wight) wrote:

There was a time when I thought that
the blackbird could secretly hit 5 on the
mach meter--but isn't there solid science
agains this? Such as:

I don't think the engines have the ability
to rev up to such a speed. Maybe the jet fuel
itself cannot produce sufficent BTU's (thrust)
to propel it that fast, maybe the fuel lines
are too small to exceed Mach 3.3

Perhaps the real inhibitor is the lack of
enough combustible oxygen to feed the engines
to shatter established speed records.

I know that the outer metal shell of the
jet couldn't sustain the high atmospheric
friction.

Am I right about all this, or is there OTHER
things to consider?

Besides things like exceeding the allowed inlet temp,
a speed much over 4 (if I recall correctly) would put
the shock from the nose in the inlets. Bad news.

On 29 Nov 2003 12:48:59 -0800, (frank wight)
wrote:

There was a time when I thought that
the blackbird could secretly hit 5 on the
mach meter--but isn't there solid science
agains this? Such as:

If you go faster than Mach 3.5 the bow shock off the nose will impinge
on the leading edge of the outboard section of the wing and melt it
off if you do it for very long. It's OK for a dash, but not for
cruise. That's pretty solid science.

I don't think the engines have the ability
to rev up to such a speed. Maybe the jet fuel
itself cannot produce sufficent BTU's (thrust)
to propel it that fast, maybe the fuel lines
are too small to exceed Mach 3.3

The SR-71 has dashed to Mach 3.5, so this isn't a problem.

Mary

--
Mary Shafer Retired aerospace research engineer

On Sat, 29 Nov 2003 19:54:46 -0800, Mary Shafer
wrote:

On 29 Nov 2003 12:48:59 -0800, (frank wight)
wrote:

There was a time when I thought that
the blackbird could secretly hit 5 on the
mach meter--but isn't there solid science
agains this? Such as:

If you go faster than Mach 3.5 the bow shock off the nose will impinge
on the leading edge of the outboard section of the wing and melt it
off if you do it for very long. It's OK for a dash, but not for
cruise. That's pretty solid science.


You know out of all the "how fast will it REALLY go" discussions
that's the first time I've heard an answer that satisfied me. Many
here are familiar with that X-15 that burned off it's ventral fin from
shock inpingment from that test ramjet. Most of the answers I'd
heard in the past for why it can't go a lot faster than 3.2 is
"because it can't". The shock thing makes total sense. I'd read that
one of the A-12s hit 3.6 at 97,600 which is probably close to the
alltime best. It's definitely the best I've ever seen published.

Chad Irby wrote in message ...
In article ,
(frank wight) wrote:

There was a time when I thought that
the blackbird could secretly hit 5 on the
mach meter--but isn't there solid science
agains this? Such as:

I don't think the engines have the ability
to rev up to such a speed. Maybe the jet fuel
itself cannot produce sufficent BTU's (thrust)
to propel it that fast, maybe the fuel lines
are too small to exceed Mach 3.3

Perhaps the real inhibitor is the lack of
enough combustible oxygen to feed the engines
to shatter established speed records.

I know that the outer metal shell of the
jet couldn't sustain the high atmospheric
friction.

Am I right about all this, or is there OTHER
things to consider?

A lot of that is pretty much on the mark. I've heard Mach 3.5 for short
sprints, but not more than 3.3 for sustained flight.

Mach 5? No way in hell, although I've seen a very few claims for Mach 4
sprints (extremely informally on that one). Even if they could manage
the power to do it, the skin would be melting (see the thread on the
Sanger Amerika Bomber for some of the problems with sustained very high
speed flight).

Same here. I live in northern California so I have heard all the stuff
coming from Beale AFB and the Mach 3.0-3.5 range seems to be the
truth; however, the airframe of the SR-71 is stressed for Mach 4.0
flight. Maybe like the Foxbat this was for emergency only with
resulting damage to the engines and a/c. But I see little need for
such speed given the Blackbird's height invunerability.

Rob

owever, the airframe of the SR-71 is stressed for Mach 4.0
flight.


Where did you hear that?

"robert arndt" wrote in message
om...
Same here. I live in northern California so I have heard all the stuff
coming from Beale AFB and the Mach 3.0-3.5 range seems to be the
truth; however, the airframe of the SR-71 is stressed for Mach 4.0
flight. Maybe like the Foxbat this was for emergency only with
resulting damage to the engines and a/c. But I see little need for
such speed given the Blackbird's height invunerability.


What height invulnerability? It worked in the 60's but in todays
environment, there are quite a few missiles that could reach out and touch
the SR-71.

On Sun, 30 Nov 2003 07:21:36 -0500, "Brian"
wrote:


"robert arndt" wrote in message
. com...
Same here. I live in northern California so I have heard all the stuff
coming from Beale AFB and the Mach 3.0-3.5 range seems to be the
truth; however, the airframe of the SR-71 is stressed for Mach 4.0
flight. Maybe like the Foxbat this was for emergency only with
resulting damage to the engines and a/c. But I see little need for
such speed given the Blackbird's height invunerability.


What height invulnerability? It worked in the 60's but in todays
environment, there are quite a few missiles that could reach out and touch
the SR-71.

Even back in the day there are some they couldn't ignore. If you
counted both sides I'd give the SA-5, Nike Hercules and Bomarc B fair
odds.

In article ,
"Brian" wrote:

"robert arndt" wrote in message
om...
Same here. I live in northern California so I have heard all the stuff
coming from Beale AFB and the Mach 3.0-3.5 range seems to be the
truth; however, the airframe of the SR-71 is stressed for Mach 4.0
flight. Maybe like the Foxbat this was for emergency only with
resulting damage to the engines and a/c. But I see little need for
such speed given the Blackbird's height invunerability.


What height invulnerability? It worked in the 60's but in todays
environment, there are quite a few missiles that could reach out and touch
the SR-71.

Well, there's "reach," then there's "reach with a decent chance of
hitting it."

The problem is that the few missiles with the height (80,000 feet plus)
didn't have enough targeting capability to hit the Blackbird at that
height, especially in a stern chase. The best they could do would be to
loft one up and try to get in the way.

The newer ones, like the "big" SA-20, might be able to do it, but it
would still be a fairly tough targeting solution - you'd need to loft
one up before the SR-71 was in range, then acquire it while in midair.

--
cirby at cfl.rr.com

Remember: Objects in rearview mirror may be hallucinations.
Slam on brakes accordingly.