SR-71 Blackbird / Aurora

Originally posted by MooMix3
Is there a point on making slower planes? Mach 2.5+ down to mach 1.8? I guess the Raptor does have better handling and control though, even when it flies at an angle of 110�!

That doesn't really make sense? Are you saying the Raptor has good handling going backwards at a 70 degree incline.

If you think the U.S. government is going to tell you the honest truth about the performance of its top-end surveillance and fighter aircraft, you are out of your freakin' mind.

All we know is what they want us to know.

Originally posted by Murcielago

Originally posted by MooMix3
Is there a point on making slower planes? Mach 2.5+ down to mach 1.8? I guess the Raptor does have better handling and control though, even when it flies at an angle of 110�!

That doesn't really make sense? Are you saying the Raptor has good handling going backwards at a 70 degree incline.

Ya, i think thats right that it goes backwards at 70�

I did some searching and the plane is newer than I thought. So i guess it cant be beat yet. They could have made a better plane with the F-23 though but it isnt as good as the F-22.

Originally posted by Majic
If you think the U.S. government is going to tell you the honest truth about the performance of its top-end surveillance and fighter aircraft, you are out of your freakin' mind.

All we know is what they want us to know.

That is what i mean by the Air force not wanting us to know about some things the raptor can do cuz the raptor can cruise and mach 1.6 without afterburner and only 1.8 with after burner yeah right even though the raptor produces more thrust than any other US fighter ever produced.
The raptor can produce 35.000LB of thrust the F-15 can produce 23.770LB and the Raptor only weight 3.000 pounds more than the F-15 so trust me the Raptor can do mach 2 with no problem.

westpoint the raptor wastn designed for speed.
it was designed with speed in mind, the raptor is designed for manouverability and stealth but they wanted good speed and other elements if your looking for speed then the YF23 is your ticket.

Westpoint, the figures you quoted about the thrust and weight comparison between the Raptor and F-15 (I am assuming for this purpose that they are accurate) are the clincher in why the Raptor would continue to accelerate in a vertical climb but thrust to weight ratio is only a part of the complex equation that determines whether it can reach MACH 2 or not. The Harrier for example has one of the Highest thrust to weight ratios around yet is not even capable of going supersonic in level flight. The drag factor increases rapidly the faster you go relative to certain design specifics, out of all proportion to the actual gain in speed so speaking hypothetically the thrust needed to push 'plane x' from Mach 1.6 to Mach 2 could be many times more than is required to push 'plane y' over the same speed range even if both aircraft are the same size and weight purely because of aerodynamic drag which in 'plane x' was less of a design priority than with plane y which has been specifically designed to fly at Mach 2 or higher. Does that make sense to you? If not its probably the way I've tried to explain it.

So also although internal weapons are much more stealthy and much less draggy than external weapons, accomodating them causes the aircraft designer to trade off against aerodynamic efficiency of the airframe itself at high mach numbers. Although this does not affect the aircrafts subsonic or transonic performance or its agility it can induce sufficient drag to prevent Mach 2-2.5 from being reached where a similarly powered fighter with external weapons BUT a smaller cross section would have no trouble.

This principle has been well known since the fifties and was the reason that aircraft like the F-102 were replaced with fighters carrying external weqapons in the first place, ie comparison between this and the F-104 and Lightning shows the two fighters with external missiles both being faster on similar power. Design techniques today are so much more sophisticated than they were back then so maybe this HAS been solved with the Raptor, but if it can't reach Mach 2 then this may explain why not.

Yes my numbers on the thrust and weight are correct and what you are saying does make sense but from that same website I got this while reading about the spec of the Raptor.

Performance estimates give the F-22 a speed of Mach 1.5 in non-afterburning supercruise mode, and a speed of Mach 2.0 or above with afterburner. Service ceiling is thought to be over 15 kilometers (50,000 feet) and the maximum range is believed to be over 3,000 kilometers (1,860 miles). Flight tests demonstrate that the F-22 combines good handling characteristics with very high maneuverability

Click here if you want to check the website out.

waynos: Excellent exposition on how thrust-to-weight ratio is not the only determining factor for maximum speed and climb rates.

Indeed, on the extreme end of that: if you put a very powerful engine behind a cardboard box, you would probably be very unsatisfied not only with its maximum speed, but with most of its flight characteristics as well.

What else is there that can go straight up after takeoff? Could the B-2 Spirit go straight up?

Just about aerodynamics of Raptor: it must be very good, otherwise it couldn't go over Mach 1 without afterburner!

And what's use of aircraft with efficient aerodynamics if you can't use it to carry anything. (carrying things externally is bad for aerodynamics)

And about top speeds, it's not only about maximum thrust and plane's aerodynamic, design of motor affects greatly (its efficiency at different speeds), also aerodynamics of air intakes is one other. (remember variable geometry air inlets)

www.grc.nasa.gov...

Just wanted to celebrate my first thread to have 50 posts and my first to have 1000 views! I also made this post to bring it to the top of the Aircraft Project page to get more people to see this

Grats and yay to MooMix3 on the big 50/1000!

Sympathy bump to the thread and general clinking of champagne glasses for all who helped lift this baby off the ground.

Kudos to various contributors for thoughtful input on aerodynamics and the performance of various airframes.

Of course, I still insist that the real specs on any military project will not be made available for public consumption. That would just be silly.

I mean, c'mon peoples!

Lots of things are mentioned here, one was the SR-71, it would do Mach 3.2 normally, and a bit over 80 000 ft. It can go a lil bit quicker and a little higher, but required special permission to do so, certainly not near Mach 3.5 and 90 000, they'd run into many issues, increased heat load on the airframe, the intake shock passing back into the inlet causing an "unstart" for a couple things. During one A-12 test flight one of the pilots landed with only a few quarts of hydraulic fluid left and a lot of wiring burnt to a crisp after accidentally going too quick.

In a similar way the F/A-22 Raptor has a lot of excess power and its top speed is limited by materials reasons in the airframe. Militarily there has been a trend for slightly slower top end speeds anyway. It is a Mach 2 class aircraft, can go slightly faster than Mach 2 in afterburner but an overspeed warning comes up as there's so much excess thrust. Supercruise speeds can vary between Mach 1.4 and Mach 1.7, the sweet spot being Mach 1.5.

It is not drag limited nor power limited, to a certain extent the faster it goes the faster it wants to go, scary. There's a fine line between speed and a useful combat radius though, in a mixed subsonic/supersonic mission its total combat radius is only about 410nm, subsonic it will probably go out to 700nm, it all depends on the mission profile desired. Hope this helps.

Originally posted by MPJay
...they'd run into many issues, increased heat load on the airframe, the intake shock passing back into the inlet causing an "unstart" for a couple things.

I think windscreen was one those which would start to take damage from heat when flying too fast too long.

This unstart could occur also in lower speed if inlet spike would be in wrong position.
Should the shockwave be expelled from the inlet, a condition known as an "Unstart" occurs. Unstarts have been known to be so violent as to crack the pilots helmet from the severe yaw of the aircraft. If unchecked, the resulting yaw is described by SR-71 pilots as though the nose and tail are trying to swap ends.
www.wvi.com...

Well, almost remembered it right.

The fastest published speed of the SR is Mach 3.5. There are several factors that limit the speed of the SR. One is the shock waves generated by various parts of the plane, at around Mach 3.6-3.8 the shock wave off the nose of the aircraft narrows enough to go into the engine, while there is the inlet spike (which slows the air to subsonic before it enters the engine), the shock wave bypasses the spike and causes the engine to unstart.

Second, the heat generated by the plane moving through the atmosphere. Even titanium has it's limits, and the heat generated by the SR brings the fuselage to the brink. It was discovered during a Lockheed Skunk Works study to see how much money and development it would take to get the SR to go faster than it's designed top speed (mach 3.2-3.5) that the metal divider between the windshield was heating up so much above mach 3.5 that it was affecting the integrity of the windshield, and at that point they had stretched the glass technology to the maximum.
www.neworegontrail.com...

[edit on 20-7-2004 by E_T]

I would just like to add that I saw a SR71 take off from Mildenhall(UK) in the 80's,It was during an airshow -The ground literally trembled beneath your feet when it throttled up it's engines ...A truly spectacular experience. Just as a footnote the LOUDEST Aircraft I've ever heard (After the SR71 ) are the EE Lightning and the Avro Vulcan

I wish I could have seen an S/R-71 takeoff but I wasn't so luck Just thought you might want to know the Saturn V rockets that took us to the moon made the second loudest sound ever made by man it was second only after a nuclear bomb explosion but im sure the blackbird ranks pretty high.

i don't know anything about sr-71 blackbirds gettin replaced by the aurora, but i know that blackbirds sure are sweet planes!

What about a carbon ceramics type of skin like the space shuttle that can withstand heats greater than you would find at mach four or mach five so why cant they uses those types of materials?

Any and all information you'd want about the SR-71 is available online, after the aircraft was retired the flight manual was declassified and is available online.

www.sr-71.org...

Just do a little reading and you'll see that although it flew fast, flew high it had limitations like any other airplane. Mach 3.17 was the high end cruise, it would do Mach 3.2 if pushed and under extreme duress, it needed special permission to do so it would do Mach 3.3 "if the limit CIP of 427 Deg C is not exceeded"

So rumors of Mach 3.5 to 4 are totally false.