Lockheed A-11, A-12, M-12, YF-12, & SR-71 Blackbirds

[Mossie]

Right.  The SR-71 was the fastest aircraft that has ever flown (maybe) & also one of the most important types in the Cold War gathering huge amount of intelligence on the Warsaw Pact countries & thei allies.  So how could you make it better?

My sceneraio is this;  Blackbird, a 1950's design is still doing stirling work, but by the end of the seventies the USAF & CIA are well aware that the aircraft are starting to age.  It's apparent that advancements in aerodynamics, electronics, materials, avionics & stealth could extend the life of the SR-71 well into ninties & even beyond.  Due to the cancellation of Aurora, the urgent need for an improved Blackbird is progressed & the Skunkworks are ordered to design & build a SR-71C (or should that be D?).

So what changes would be made?  I guess vast advances in speed wouldn't be required as there's still nothing much that can touch it (or is there?), but a few extra mach points might useful when avoiding MiG-25/31's or advanced SAM's & it was even known to run into the odd Viggen over Sweeden.  Upgraded or new engines maybe?  More advanced avionics would help, as well new sensor packages.  Changes to the airframe, new alloys or even heat resistant composites?  New aerodynamics?  Anything else?

[Zen]

Stick with titanium IMO, the airframe however could do be complete revision, Valkyrie was more advanced for mach 3 cruising, by its use of semi-compression waveriding.
Probably could take a machine upto mach4 or even 5 like the P.42 studies.

IMO focus on mach3.5, as this allowes for a variable bypass aft-fan tubofan for the engine. In turbofan mode the engine is rather more efficient and quiet, as you progress up the speed duct more air to the core until mach2 and then begine transition to ramjet.
Studies I'm aware of for SST's showed the aft-fan arrangement was optimal for mach3.5 too high for a civie airliner to be affordable, but for a recce platform......

[jcf]

The fastest 'powered' aircraft to fly was the X-15-A2. The space shuttle becomes the fastest aircraft of any type when it glides back to earth.
The X-15 used large amounts of Inconel in the structure, the shuttle uses carbon-carbon in the highest heat areas, so... maybe your developed SR-71 would incorporate features of both?

Jon

[fallenphoenix]

suppose this goes without saying but a glass cockpit would be an idea, GPS to replace the aastro inertial nav systems, new ECM maybey do away with the GIB due to more advanced computers etc.
TBH I cant really see to many major external changes though ok just for the hell of it modern FBW system so we do away with the vertical stabs?

Craig  :dum:  

[Mossie]

Okay, by fastest I meant 'operational', or at least known operational aircraft.

Budget wise, I think we can assume a big one here.  In an eighties Cold War scenario with strategic recconisance being taken very seriously by the US Military & Ronnie in charge, a big black budget might have been thrown at it.  The cost to develop & maintain the current spy satelite network I can only guess at but I believe it would have been huge.  If you believe Aurora is out there, the cost to develop a new hypersonic aircraft would probably have cost more than a new Blackbird.  Part of the reason I mentioned only increasing the mach range by a few points was to avoid developing a completley new powerplant, to reduce costs & risk.  But apart from that I guess anything goes budget wise.

Talking about engines, I was thinking of an upgrade to or derivative of the J58's, there's nothing much to compete with it I guess.

Glass cockpit, yes, but in the eighties timeframe sense of a mixture of HUD's, MFD's & traditional gauges.  I'm being quite specific to this time frame as I believe this is the most likely period for a program of this kind, also we could go on forever with equipment fits!

I can't see the  vertical stabs being completley removed, even with a hefty FBW system.  They are the only real control at high speeds, the Blackbird is almost ballistic without them.  I can see them being reduced in size though, possibly more of a blended shape & canted further inwards to improve stealth?  Canards are a possibilty, although they were wind tunnel tested in early development & it was found that they didn't give any advantage.

Materials wise, Inconel or other alloys are a possibility.  Carbon-Carbon I think lacks the impact resistance for a military aircraft?  Large amounts of titanium would still be likely, especially if commanality was an issue.  Depends I suppose on wether it would be a complete new build or upgrade of existing airframes.

Any ideas on reducing the IR signature?  Would it even be worth it, being that you'd have to get it down very low to avoid detection & with a combination of the engines & airframe heating, would it be possible?

[tinlail]

Reaction jet control system with rocket booster for high speed dash, over target.

Maybe a clever person could just figure out how to turn the J58 in to a rocket-jet with an oxidizer injecter. Going to need to figure out where to put more fuel tanks however.

[Burncycle]

I like some of these ideas!

Speaking of, I really like the idea of a craft like the Dynasoar as a recce platform. Sorties would be very expensive and turnaround time would be huge... but it would have had a place for time critical targets until Recce satellites matured.

You'd be traveling much faster than any airplane, and could provide better resolution than the satellites by dipping into the atmosphere over the target area then thrusting back out into orbit.

[jcf]

Okay, by fastest I meant 'operational', or at least known operational aircraft.


Materials wise, Inconel or other alloys are a possibility.  Carbon-Carbon I think lacks the impact resistance for a military aircraft?  Large amounts of titanium would still be likely, especially if commanality was an issue.  Depends I suppose on wether it would be a complete new build or upgrade of existing airframes.

Last I checked both were very 'operational', just not 'militarily'.  

Carbon-carbon impact resistance evidently depends on the nature of the particular composite as the term covers a wide range of possibilities, its not all the same as what is used on the Shuttle.
Anyhow, to what impacts are you referring? Weapons? At those speeds any hit would probably cause massive airframe failure regardless of material.

Cheers, Jon

[elmayerle]

Masking the IR signature of a Mach 3+ vehicle is pretty much a waste of time, just the air friction heats the airframe enough.  I could see going with an improved J58 using later aerodynamic analysis methods to get more power out of the same engine envelope.  Similarly, the existing engine is something of a turbo-ramjet and I could see taking things a bit further, for higher speed or higher altitude operations, by going to a turbo-ram-rocket configuration.  I don't know that I'd make too many material substitutions, save where it'd improve reliability or significantly reduce weight.  One thing, though, the inlets will require some redesign if you're going for a higher speed regime in air-breathing mode as I think they're only good up to Mach 4 or so.

[tinlail]

One thing, though, the inlets will require some redesign if you're going for a higher speed regime in air-breathing mode as I think they're only good up to Mach 4 or so.

My understanding is that the aerodynamic of the airframe limit the top speed to 3.6 beyond that the shockwave off the nose interferes with the engine inlets. Reportedly inlet tempeture limits the plane to about 3.2. Which is why I suggested rockets to get out of aerodynamic flight operation. see http://www.sr-71.org/blackbird/manual/

Of course how the SR-71 would handle "reentry" back in aerodynamic flight is a damn good question, and not something I would want to be the first to try.

[Madoc]

Folks,

Another thing to remember about the SR-71 is that it was not stressed for any sort of aggressive maneuvers.  Straight ahead and really, really fast was about it.  No sharp high G turns or such else you'd wrap the airframe around itself.

So, if you wanted to do something like atmospheric reentry - replete with its higher G loading and maneuvering requirements - you'd have to substantially beef up the airframe.  And that'd cut down your payload fraction, slow your acceleration, and boost your fuel consumption...

Madoc

[tinlail]

Very True.  the manual recomends single digits for AoA, at high speeds
However all what-if tend to deal with relaxing a single constrain on an airplane development (technology, politics, money)

The SR-71 was developed pretty much to the edge of all constaints as much as possible.  That is what makes it such a nifty plane. A really spiffy digital autopilot is realistic but not a interesting model.

[Mossie]

Carbon-carbon impact resistance evidently depends on the nature of the particular composite as the term covers a wide range of possibilities, its not all the same as what is used on the Shuttle.
Anyhow, to what impacts are you referring? Weapons? At those speeds any hit would probably cause massive airframe failure regardless of material.

Jon, carbon-carbon I'm not too familiar with, but I guess if you used the type of carbon fibre from say, motor sports that has to withstand high impacts you'd something much more resistant than the stuff they use on the Shuttle?  For impacts I was thinking more of accidents, more than a third of A-12/YF-12 & SR-71 airframes were lost, the price of operating at the edge I guess.   If something fails you don't want it exasperated by fragmenting parts being ingested in to those engines.

  Masking the IR signature of a Mach 3+ vehicle is pretty much a waste of time, just the air friction heats the airframe enough.

Thought as much Evan, too hot to bother, it's going to light up on any IR detection system!

  Folks,

Another thing to remember about the SR-71 is that it was not stressed for any sort of aggressive maneuvers. Straight ahead and really, really fast was about it. No sharp high G turns or such else you'd wrap the airframe around itself.

Yeah Madoc, my idea was for it to operate in a very similar way to SR-71, the upgrades being more to increase service life, ease of operation, ease of maintainance & safety.  Extra mission fits might be very useful too.  Performance improvements would be a bonus if they could be eased in with the rest, for instance picking up a bit of extra speed due to reduced weight where the focus was on reducing airframe stress.  But if folks have other ideas (I really like Burncycles idea of a Dynasoar type re-entry vehicle, if not in line with my own thoughts) please post them!

EDIT, sorry, hit post while I was only half way through!!! :dum:  :dum:  :dum:  

[kitnut617]

Some time ago I read an article about the X-15 and how they were 'popping' in and out of the atmosphere on a regular basis, I can't find where I read that now but this book might be a good one to read.
http://history.nasa.gov/x15/cover.html
As already mentioned, the fuselage was made strong enough for these operation plus it used reaction controls when at these altitudes.  It didn't have any fragile tiles that could break on re-entry either.

I would imagine the next recon platform would be made to 'skim' just outside of the atmosphere in the same way.  I had a thought a derivitive the X-15 could have been used, a typical operation would have it dropped from a B-52, say over Norway, then pick it up in Hawaii or something like that.

[Archibald]

An interesting airbreathing X-15 concept from 1969.
SERJ is basically a ramjet with a separate fan for take off and low speeds.
The fan is masked at high speed, allowing mach 4+
http://www.up-ship.com/apr/extras/serjx15.htm (from Orionblamblam Aerospace Project Review)