Cubdriver

To give a solid answer to your question really requires having been there, since the test pilots and engineers were the people who knew the most about it. Milt Sills, Doug Hazelwood, and Ellis Brady are some key players in the development but it took no less than 500 engineers to get it all worked out.

Something to remember is that Cessna had been working very seriously on advanced subsonic business jets since the late 1970s when they determined their best selling airplane was the Citation line. To improve the product and expand market share they asked for and received help from Richard Whitcomb, the famous NASA aerodynamicist to design an advanced wing to go on the Citation III. This airplane acted as a basis for the VI, VII and the Ten. Knowledge and expertise on how to make business jets was improved upon throughout the 1980s at Cessna. When the bottom fell out of the piston market Cessna wisely changed its sales strategy to making only business jets. By the time the 80s went out they were doing so well they were looking for ways to grab even more of the business jet market. Hence the idea for a fast intercontinental business jet, which was the Ten.

Published pictures of the test prototype airplane in green epoxy primer at flight trials appears in Jeff Rodengen's book. I recommend the book, available for about $30 here. I am sure there are better resources, but this one is well referenced and has a chapter devoted to the Ten.

To really get the scoop on how the Ten was designed is limited by it being proprietary information, but the principles of aircraft design can be understood from books like Richard Shevell's Fundamentals of Flight. You could also go through old Flying and Aviation Week magazine articles if you had access to a good library and some time to do it. Rodengen's book has a list of magazine articles to help in the search. Much of the technology used in the Ten, if not all of it is addressed in engineering textbooks and not much of it is exotic. After all, high quality business jets and aircraft of all descriptions had been around for decades before the Ten came about.

It was a state of the art business jet in 1996, and is still rather remarkable today. As with any well engineered product, its excellence comes from a unique combination of innovation, timing, quality, and hard work to make something wonderful come together.

UAL T38 Phlyer

cubdriver's explanation is quite plausible, although he did make a typo--it should be 0.07, not 0.7.

One of the problems with supersonic airplanes is that jet engines do not like supersonic air. I won't go into the aerodynamic reasons other than to say the maximum coefficient of lift, whether that be your wing, or your compressor blades, goes down by about 50% when supersonic.

Give supersonic air to a jet engine, and they like to compressor stall. Violently. Like blades exploding through the side of the engine case.

That is why supersonic military aircraft either have a smaller intake area than the area of the compressor-face (fixed inlet jets like the T-38, F-18A or C, or F-16), or a variable-geometry inlet like the F-15, Super Hornet, or F-4.

Fixed-inlets reduce takeoff thrust, but allow supersonic flight. Rough tradeoff for a business jet.

Variable geometry inlets are heavy, complex, and maintenance-intensive. Not good for a business jet.

And, you don't "break" the sound barrier--if you are above mach, you are continuously breaking it. Drag does not go down when you go faster than Mach--it still increases, although the steepness of the curve flattens a little.

Bottom line--if the Citation X could cruise at Mach 1.05, you might save 30 minutes on a 10 hour trip--but at double the fuel cost.

So maybe you would actually have to land and refuel, thereby losing all the time you supposedly saved.

By the way, due to the huge trim changes involved when going transonic/supersonic (center of lift goes to 50% chord, on ANY airplane), you need an all-trimable tail, as most jets have. IE, the horizontal stab must move as well as the elevator. (Fighters just have a one-piece all moving slab). So, while the airframe may be slightly super capable, the limiting factor is usually the engine inlet, and overall economy of operation.

the King

That and the fact that the drag increase in the transonic range is a stiff penalty for all that speed. It would be inefficient in terms of either fuel or maintenance (as UAL T38 pointed out). Flying much faster than Mach 1 is more efficient, if you can get there.

Cubdriver

.07 margin it is. Too much late night typing!

One more clarification to make is that, although the airplane could go supersonic and did according to test pilots, its max speed in a reliable sort of way was only M.99. Subtract the M.07 margin for certification and you have M.92, the published top-speed for the Ten. Supersonic was only possible in a controlled dive. It is technically a supersonic airplane by a little bit, but it just doesn't have thrust to do it reliably for reasons mentioned by Phyler and is not designed to do it regularly.

Drag curves rise steeply around M=1 but come down after about M=1.4 as noted by the Prandtl-Glauert Rule. "Breaking the sound barrier" is a colloquial expression from times prior to 1947 when Chuck Yeager had yet to go faster then the speed of sound and collect the flight test data. It turns out to be an apt term because drag rise near and around the speed of sound is very steep, coming down steeply in the S/S range as it went up in high subsonic range.

Supersonic aircraft can cruise efficiently at reasonably low drag levels, but it is hard to design an airplane to get to the supersonic regime in the first place, very few customers are willing to pay the additional cost. There is a steep drag rise around M=.85 hence the cruise speed of most airplanes is somewhat below that figure. To design an airplane that can cruise at high subsonic speeds requires aerodynamic tinkering for a relatively small gain in speed. It can be done, and many airplanes have the requisite drag reduction features to make it possible.

But it is not true that drag stays high in the supersonic regime- it is surprisingly low. Drag comes back down to subsonic levels by about M=1.4. For reference, see John D. Anderson's Aircraft Performance and Design or one of the other good textbooks. As far as fuel burn is concerned, thrust specific fuel consumption is very fairly constant with speed. This explains why the Concord cruised at M=2 and why recent fighter jets are optimized for high speed cruise (F-22/ F-35).

UAL T38 Phlyer

Don't have my text with me, but I believe the drag-drop you mention is the Coefficient of Drag. That is why I said the slope of the drag rise decreases.

Problem is, the total drag is still increasing.

I've been Mach 1.85. I guarantee you, when we came out of burner, it felt like I had slammed on the brakes. And that was at 52,000 ft. The drag I felt was worse at 1.8 than it was at 1.2.

Interestingly, supersonic airplanes' top-speeds seems to be more a function of their maximum indicated airspeed capability, ie, form-drag. The Phantom would do about 600 indicated on the deck in burner (500 ft AGL). Take it to 40,000, and you could get 500-550 indicated. That would be about Mach 1.4 or 1.5. Take it to 50,000, and the same 500 indicated was about 1.85.

The Concorde did Mach 2.0 because is cruised at (I think) abot 350 indicated, which would be about Mach 2 at 60,000.

III Corps

Jump seated a few times on Concorde and got to fly the sim for a while.. surprised at the initial cruise altitude coming across the pond was in the low 40s and we cruise climbed to about 52 or so. Never got near 60,000.

Some of the old 'white glove' captains preferred to hand fly Concorde all the way while others did use the autopilot. The F/E was the busiest making sure the fuel shift took place at the proper pace. Colder than ISA and Concorde could accelerate faster than the fuel shift and warmer than ISA, the fuel shift could occur faster than the acceleration. The whole idea was to make sure there were NO flight control deflections which translated to drag. And with an engine loss at Mach 2, it wasn't that big a deal to handle (at least in the sim) but the big problem was moving fuel forward to ensure proper CG for handling as the airplane slowed.

No speedbrakes on Concorde but the inboards could be reversed in flight.

Damn nice machine.. and a very interesting design. Amazing thing is the Brits and the French were able to work together to design it, build it and fly it.

FWIW, the Capt I flew with had more than 5000hrs at Mach 2...one of the original guys who checked out on Concorde. School was about 6 months long two IOEs, one for 'normal ops' and one for cold wx/light weight ops.

Cubdriver

Correct... CD. According to the graphs CD drops precipitously after M1.4. I am sure the total drag felt in the cockpit is quite a bit, as you claim.

rickair7777

In US airspace, > M1.0 is flat-out illegal at any altitude...the underlying reason is noise abatement. Several manufacturers are exploring super-sonic biz jets which will be designed to spread the shock wave out so as to not generate a sonic boom (more like a "sonic rumble"). However, the law doesn't clearly allow for "quiet" supersonic flight, so they will have to get the law changed before they are in business.

The military is exempt of course, although they go to great lengths to minimize sonic booms in poulated areas.

There is no technical reason that prevents supersonic flight at sea-level, it just takes more power and structural strength, and aerodynamic design features...many fighters can do it. It's easier at high altitudes due to lower drag and the fact that the speed of sound decreases as altitude increases.

III Corps

rickair7777, Aerion says it has orders for its SSBJ and its competitor says it is close to orders.

Aerion believes it will be able to operate over the US above Mach 1 with the right atmospheric conditions . Due to the aerodynamics, Aerion also says it will be able to operate efficiently regardless of super or subsonic.

The modified F-5 used in some of the NASA testing is now at a museum in Florida. It is not airworthy.

Back when Douglas, Boeing and others were looking at the SST, most were around M 2.5-2.8 for sustained cruise as I remember. They could have targeted a higher mach with resulting higher costs for design, engine, etc but they found the real limiting factor for such a design was not speed but rather turn-around time. It took x amount of time to turn the machine around and thus going .xx faster really didn't pay for the additional complexities.

7576FO

*area rule reduces drag by smoothing the rate of change of the longitudinal cross section area of the total airplane. To do this the belly fairing was carefully shaped and the fuselage is concave at the pylons.

The X3 after the X1 X1a and X2 was to go Mach 3. It couldn't even break mach 1 because of Area rule.
The coke bottle shape, or the fuselage is concave to draw the shock wave closer in to the wing root.