This is my "What If..." alternate reality build.
I DID NOT MAKE THE AMAZING SR-71! All credit goes to the creator for that.
(Update: The original seems to no longer exist, it's lineage is of FA1pKa, and the version I uploaded does have that still as the "url=" in the xml file. Unfortunately I cannot properly give credit due to that!)
All I did was fine tune it even further -- giving it more refined lines, enabling smoothing on specific parts, fixing this and that, leveraging modern SP capabilities -- and then went about adding my version of an Ultra-High Bypass Fan (aka Propfan) to it.

Our Timeline: SR-71A "Blackbird " created by Lockheed-Martin's Skunkworks division and used by the United States Air Force (USAF)
Alternate Reality: ZR-81F "Blackgoose" created by Jockheed-Marvin's Lazyskunk division and used by the United Citizens Air Force (UCAF)

What if... things were a bit different?

What if we didn't get the amazing SR-71 with those incredible hybrid RAMJET engines?

That's where this project started; however, my original plan was going to be "What if jet engines were never developed but we still came up with all the aircraft designs, only they were propeller-driven engines?"
It was my intention all along to use the Ultra-High Bypass Fan in this, but for whatever reason it hadn't "clicked" that, despite using the blades for propulsion, it was still 'powered' by what we can define as a jet engine.

Nevertheless, this was a fun project, and while I did TRY IT with the Jet fully disabled, only the Props doing the work, it was unfortunately limited by SP Physics to only roughly 755MPH (level flight) at just about any altitude -- depending on how much HP I gave to them of course. While that is still >Mach 1 at around 12000ft, it's not even close once you get to cruising altitude where you have to go much faster to be supersonic... yet I was still being held back by that same barrier.

As such, it is a true UHBF in that it still employs the power of a Jet Engine in a fashion :)

At low altitude, it still is held back by that barrier, but... once you climb passed 23000ft, you better make sure you're not taking a drink, because cue the lateral G's! (Anyone familiar enough with SP knows that there are various altitudes in the game where air resistance changes; I'm aware of 0-12000ft, 12K-23K, and 23K-40K [approximate altitudes, in Feet])
From there it's a steady, and quick, increase up to over 1100MPH, where it eventually tops out at around 1150ish at 40K-45Kft altitude. It'll happily fly much higher, but not quite as fast.

So everything said and done, those Lazyskunk Division engineers knew exactly what they were doing.... or they just got really lucky. Eitherway, it still looks awesome and is fun to fly!

Liberties were taken on paint scheme, since it IS alt reality here. Landing Gear was adjusted from where the original's was, and there was a MINOR change to the wing section at the extreme back, to provide a little extra clearance for the UHBF setup. Otherwise I kept the rest of the dimensions as the original author had, aside from snugging up some panels to remove micro-gaps, and moving some of the styling panels closer to the body just to improve looks. I also disabled Drag on all of those surfaces that would be "paint", or "smooth", but were protrusions in SP in order to accomplish the same visuals. (I did adjust the Yaw rotator speed, slowing it way down, to not be so 'jerky' if using keyboard)

Landing Gear was re-done visually to appease my own desires.
However, function was changed from its original "AG2+VTOL", to now simply be "Gear" toggled, which is way nicer. No AG are used as a result.

Flying:

TAKEOFF
-Spawn in
-Give it 3-seconds to "settle".
-Apply a small amount of Trim Down (for nose-up)
-Full-Throttle
-Around 450MPH it should lift off on its own, otherwise, adjust trim some more OR gently tap Pitch to get the nose up.
...GENTLY... as to not run the blades into the tarmac!
-Climb to your desired altitude, at whatever angle of attack you desire. 90deg vert is fine, it doesn't care. It will not stall out, too stronk! ;)

LANDING:
(just remembered I forgot to add a 'chute just-in-case; sorry!)
-Throttle back to ~20%
-Come in VERY shallow (level). Use Trim if you need. Only want the nose up a tiny bit.
-Cut throttle to 0% just before you reach the runway to coast in; approx 200MPH
-When you've almost touched down, mash the Brakes to deploy AIr Brakes to slow down enough and touch down completely. OR if you're already touched down, mash the Brakes to stop.

Included is a variant of this UHBF engine assembly on a test stand (NOT connected to the plane, so you don't even have to remove it to fly!)
Its size and power are not the same as what's on the "Blackgoose", but that's setup to be easily added to a build, such as a small commercial jet.
Select the gold fuselage block connecting to the weapon strut and then open the Attachment Editor (in the curved-arrow menu), then "Delete All". You can now remove the test-stand assembly.

From there you can click and drag the jet-engine to move everything, and make a Sub-Assembly with it.
There are 6 parts:
-One JE90
-2 Fan Hubs, 8 blades each
-1 Fuselage Intake (hidden inside)
-2 Weapon Struts functioning as the attachment point to mount it on your craft. (Feel free to use whatever you'd like inside of those)

I've already set them to "Disable Aircraft Collisions" so that nothing should explodes on you!
Jet power is at "5", and each Prop Hub is set with 1000HP. Pitch is Fixed. Both props spin in the same direction. (Although on Blackgoose, each side spins inwards, to combat torque-roll).

ENJOY!