Flexjet orders 20 supersonic business jets from from Aerion
 

Beginnings of a new supersonic era?

Notably, if the Aerion AS2 flies at Mach 1.2 at or above FL350, its sonic boom will not reach the ground -- possibly allowing supersonic flights within the continental US and Europe, in addition to oceanic flights and regions with no supersonic restrictions (notably China).

Read more at Reuters

Can someone with more theorical knowledge than I do explains this ?

I also fail to see the interest to fly at M1.2 compared to a Citation X at M.9 at 1/5 th of the price.

Sonic booms and mach 1.2
 

A simple explanation of why the sonic boom does not reach the ground when at Mach 1.2 above FL350 is found here:
Quiet Supersonic - NASA Chases Fleeting Booms | Things With Wings

Cubemaster

Thanks cubemaster. very interesting , we'll see if those "evanescent waves" are acceptable or not to people on the ground , but the schema in the article raise another question : would the reflected wave be perceided by following aircraft flying behind/below ?

It's supposed to cruise at M1.4-M1.5 over water. Still not quite Concorde, though.

Maybe a Tech Log question, but is there a good (technical) reason why Concorde couldn't have done that ?

"It's supposed to cruise at M1.4-M1.5 over water. Still not quite Concorde, though."

it would still spare an hour or two on transoceanic flights, in business world that might be worthwhile

Smells like a PR stunt to me. Mach 1.2-1.5 has huge transonic drag and the massive additional fuel consumption will eat away you range, which is not worth the marginal overall speed increase. At least not for a significant number of aircraft to make the development costs break even.

I wondered when this old chestnut would come around again. Massive airships and personal jet packs will be back again sometime as well....:ugh:

Aerion AS2 will be the first production aircraft to employ a Supersonic Natural Laminar Flow wing, after apparently successful tests with NASA demonstrating an SNLF airfoil at high Reynold numbers suitable for a commercial jet.

A laminar flow wing significantly reduces drag, up to 90% reduction compared to current supersonic wings. The reduction in total drag (including other parts of the aircraft) is more modest -- predicted to be around 20% -- but that's enough to make supersonic flight economical.

Aerion's airfoil was able to simultaneously maintain laminar flow while shaping the sonic boom to enable quiet flight.

If the 12 people that you are flying are paid in the order of $10,000 an hour or more, then the sums may well add up for the companies using seats on such a biz jet as a journey need not take a full working day out. Add continual Internet over SATCOM so work can be done during flight.

You can be sure that the beancounters will have worked out the comparative costs of travel by different means, including down time while traveling.

What might be in the rear half (approximately) of the fuselage? - just something to hang the wings and engines on?

With AS2 an executive might have morning meetings in New York, then head to London to sign a deal, then make it back to New York in time for dinner & daughter's piano recital that evening.

When you're a billionaire, why not?

I know about a couple of people which are looking into a A340 Private Jet. O.K the aircraft is rather cheap, but the cost for conversion and the tco :} or think about what people are willing to paar for the Gulfstream G650
From my point of view the market is there.

Also, whilst there are a couple of jets that cruise at 0.9+, how many actually do it more than once after they see the fuel consumption?

The current "fast" jets are mostly top trump machines themselves.

There are a fair number of "cost is no object" people out there - Boeing has delivered over 200 Boeing Business Jets (including seven 777, nine 787, and eight 747-8) and the cost of the custom interiors is typically similar to the cost of the airframe.
It's long been speculated that the next supersonic passenger aircraft would be a business jet - this would seem to confirm that.
All that being said, I'll believe it when I see it. There are some major regulatory challenges (today's regulations are far removed from what Concorde was certified to), and the greenies will certainly have a hissy fit over the environmental impact and carbon footprint of a supersonic toy.

Every time I see a picture of the Aerion AS2 I think "Douglas X-3 Stilletto". The Stilleto configuration (long skinny fuselage with high polar moments and really short wings) had severe inertial coupling problems at high speeds. Joe Walker barely survived an inertial coupling episode in the X-3. How is Aerion overcoming this problem which is inherent to that configuration?

As the Air and Space Smithonian website says:
Every research aircraft poses a question. Sometimes the answer is "forget it."

The X-3 Stiletto | Air & Space Magazine

http://www.themanufacturer.com/wp-co...AS2-design.jpg
http://www.diseno-art.com/news_conte...Stiletto-6.jpg

Then there was the Lockheed Starfighter.

We've had unstable aircraft with computer-controlled control surfaces for over 40 years, the inherent inertia coupling tendencies will be controlled by that same philosophy.

The X-3 was designed in the late 40s/early 50s and hence couldn't benefit from small lightweight digital computers because they were not developed until 15 or more years later.

Just read the remainder of the X-3 Wikipedia article. Quite sobering. 260kt take-off speed and +/-7g roll-coupled pitch oscillations on the flight where Joe Walker nearly lost control.

The Aerion is real enough - a friend of mine, one of my instructors, is a senior engineer on the project. Lots of interesting stories... (not to be repeated here I'm afraid).

A few years before the X-3 even flew, a NACA engineer by the name of William Phillips had theorized the possibly of inertial roll coupling, provided precise mathematical equations of the phenomenon, and even devised solutions to the problem if it were ever to occur in practice (which of course it did).

I believe part of the solution is to increase pitch and yaw stability by having a larger tail. Stability augmentation (similar to a yaw damper) can also be used.

Don't misunderstand my skepticism. I have no doubt that Aerion is working on this project. What I question is if it will ultimately result in a certified commercial product.
There have been a lot of new aircraft projects that failed to make it past the prototype phase (many didn't even make it that far - including the Boeing SST). The cost and regulatory challenges to a supersonic commercial aircraft are massive. As I've noted the changes to the FAR and JAR/CS since the 1970s will make it incredibly difficult to certify a supersonic capable bis jet.

The company claims 50 letters-of-intent from customers, each with a $250,000 deposit.

This is not the same as aerodynamic instability. This is an inertial instability. It is caused by forces of a rotating mass overpowering the forces of an aerodynamic surface. No amount of computer sophistication can overcome this instability. The aerodynamic control surfaces must be enlarged. Further, look at any relaxed stability aircraft and you will see large control surfaces. Software alone cannot generate the large forces required to maintain control. The software needs powerful control surfaces to work with. Those do not appear to be present on the Aerion AS2.

Indeed. The Starfighter's wing is (roughly) based on the X-3's wing. Lockheed learned much from the X-3 so that the Starfighter had MUCH larger tail surfaces than the X-3 AND it had a ventral strake for additional aero authority. All this appears to be absent on the Aerion AS2.

It is generally recognised that coupling can be ameliorated by,

1. increased directional stability
2. reducing dihedral effect
3. minimising the inclination of the inertia axis at normal flight conditions
4. reducing undesirable aerodynamic coupling
5. limiting roll rate, roll duration, and angle of attack or load factor for performing roll manoeuvres

The typical high speed aircraft has some sort of roll performance limitation by flight restrictions or automatic control device to prevent reaching some critical condition from which recovery is impossible.

I can't think of any manoeuvre on an aircraft such as this where coupling could be an issue, and assume modern flight control computer systems would look after point (5). They won't be doing twinkle rolls. With Airbus part of the team, whatever is the product produced I'm sure you could take it to the bank.

Well if cost is no object and these people are so incredible important they won't have any problem with a 100% VAT paid at the location of manufacture (not some rinky dinky modern day pirate haven place of registration) will they?

No one is that important, although some people might think they are; if Putin and Obama can make do with subsonics and telecoms links so can they.

On a less bitter note, it looks like it might be a bit of a hot ship to handle at low speed, would it be able to get into Citation sized airfields.

The future will tell what will become of this project.
Seem interesting though and I wish all the luck for those involved.
But I couldn't help myself posting this little picture. I Think that some of you will get it and maybe laugh a little!

https://33.media.tumblr.com/391a79e2...MtC1r8g16e.jpg

:8

Edit: Type-o

You can always get an aircraft onto a landing field. Whether it's in a condition to fly out again is another matter.

What sort of altitude are they planning to fly this thing? Concorde was pretty much on its own up at FL600 where it didn't have to worry about other traffic, I'm guessing this will be flying lower

Yes the faster you go, the higher you need to fly.

Since the AS2 won't fly as fast as the Concorde, its optimal altitude should be closer to FL450, with service ceiling around FL510.

Predatory taxation is usually counter productive. When they raised the excise (luxury) tax on yachts here in the US, they stopped producing them here and many thousands of jobs were lost. When they raised taxes on and demonized those who flew in biz jets, many thousands of jobs were lost. The politics of envy are not only ugly, they are self defeating.

What you say does not hold for supersonic flight.
i) The speed of sound is a function of air temperature ONLY.
ii) Temperature remains constant from the beginning of the stratosphere up to 65000 feet, after which the temperature increases again.

Being higher, at fixed IMN, will reduce sigma, which will increase the difference between TAS and EAS. In the fixed temperature region of the stratosphere then, the higher you are, whilst TAS will stay fixed, EAS will go down, reducing aerodynamic loads on the aircraft, and potentially drag and thus fuel burn required.

So the higher the better, so long as it stays within the lower stratosphere, and there may be some value in creeping into the middle stratosphere a bit.

I think, it's late, might come back and check my maths in the morning.

G

Then the manufacturer will move the location to a country that does not have such crippling taxes.

It's a big world.

In supersonic flight, lift-dependent wave drag increases rapidly with Mach speed (by M^2), while some other drag components decrease with altitude. So the faster you go, the higher you need to fly to minimize drag.

Aerion make no mention that I can see of planned altitude capability, though they mention approach speeds will be less than 135 Knots.

An interesting paper on inertia coupling, X-2, X-15 and Space Shuttle

http://www.nasa.gov/centers/dryden/p...ain_H-2106.pdf

I suppose great minds have considered thrusters of some kind to augment aerodynamic controls, and that doesn't work?

The fuel would probably weigh more than bigger control surfaces, and would require more maintenance to keep the thrusters working.

If I remember correctly, one of the first warnings the Columbia crew had of impending doom was the low fuel level in the thrusters that were compensating for a molten wing.

For those questioning the economics, not what you would call overwhelming though.

Supersonic Bizjet Math Makes Sense Now, Says Analyst | Business Aviation News: Aviation International News
You can by not allowing the aircraft to encroach the areas where the instability will manifest itself. Think envelope protection, as used in the Airbus. As I previously posted,In essence, it's not a lot different to the relaxed stability aircraft we have now. A less stable aircraft requires smaller control surfaces, and deflections, to initiate maneuvering; consequently drag and control surface imposed stresses will be reduced and aircraft responsiveness will be enhanced. Since these characteristics will typically make control by the pilot difficult or impossible, an artificial stability will typically be imposed using computers, servos, and sensors as parts of a fly by wire control system.