Aerion SBJ

Rhinocrates

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lowboom

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There are a lot of challenges that come with a Mach 4 commercial aircraft that are not constraints for a military aircraft. Some that come to mind; Chapter 14 community noise certification, mutual inlet unstart, certifying the inlet control system, rotor burst, material allowables development, fuel availability (can’t use standard jet fuel), ozone depletion, 250 kt restriction on operations below 10,000 ft, taxi in and taxi out times, turnaround time issues due to the airframe temperature. The Breguet range equation would indicate that the MTOW of the AS3 would be exceptionally high.
 

Moose

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Sudden and disappointing, considering the Boeing and Berkshire partnerships. Usually this kind of suddenness suggests something untoward, though not always.

I guess all eyes go back to Boom.
 

DrRansom

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Their design seemed more challenging than Boom but also more politically and economically reasonable. Based on this, one would have to expect Boom to go down soon.
 

Archibald

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Rhinocrates

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That's sad. I see Bigelow Aerospace laid off all its staff just over a year ago too when things looked like they'd turn out well in just a little more time too.

Can we blame COVID for this latest calamity? There's a lot of reporting on how the super-rich have actually increased their wealth substantially, so maybe not. The highest echelon of luxury cars are usually a good barometer of financial optimism and they seem to back this up with Bentley posting record profits for example. On the other hand, COVID lockdowns have encouraged people to find alternatives to face-to-face meetings and that could be a cultural change that would affect the business travel market long-term.

This sudden rush to build brand new facilities before any attempt to produce something was quite suspicious.

I hate to be cynical because they seemed so serious, but I guess that's a red flag: announcing ever-more ambitious plans and major changes in configuration when you still don't have tangible hardware working. The Mach 4 'AS3' proposal fits this. Lilium certainly comes to mind with its proposed eleventy-seven seats and a jacuzzi super-duper model which is obviously aimed at generating buzz among potential investors rather than actually progressing towards viable hardware. If I was in Lilium's position, I'd work on a subscale single- or two-seater that doesn't catch fire and sell it in a limited run at ridiculously high prices to early adopters.

I'm also thinking of the parallel discussion that's going on about Spacex versus Blue Origin. Lots of expl- I mean 'wide-area landings' in the early stages, and plenty of redesigns, but always something to demonstrate and most importantly, resilience and determination enough to build again right away. It's a version of the classic 'build a little, fly a little' ethos of aerospace development. Though in this case, there's quite a lot of the Silicon Valley cultural model that's supported Tesla - consumers expect delays and continually improved iterations because it makes them feel a part of the design process and hence the 'family' of the brand.

Sorry about all the blithering about 'culture', but I used to teach in areas related to design and marketing and haven't fully recovered - and I'm reminded of an esteemed contributor's quote from Sidney Camm that aircraft have four dimensions: length, width, height and politics.

Then again, there's just luck.
 
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Archibald

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This sudden rush to build brand new facilities before any attempt to produce something was quite suspicious.

And the Mach 4 project, too - I said it on top of that page: that was insane. And it will remain so for others.

If you want to "fly" very fast across the globe, don't go airbreathing inside the atmosphere: the sonic boom and the heat barrier are unforgiving.
It would rather put a rocket in the tail of a bizjet and fly suborbital, point to point. No atmosphere, no sonic boom, no heat barrier, no complex airbreathing engines.

Present day technologie would allow a turbofans-and-rocket spaceplane to fly a 7000 to 12 000 km ballistic hop at 6 km/s or 7 km/s with 10 mt or 20 mt of payload - enough for a large bizjet or an Hercules -class cargo transport.

Very basic rocketry and ballistics could do the job. Musk has been smart enough to see that Starship without BFR underneath could very much become a "suborbital 747" or a "ballistic A380".

It is in fact a very simple calculation. Propellant mass fraction 0.85 ; specific impulse of a non-LH2 prop combination: 330 to 380.
End result: 6.5 km/s. Next step: how far can you go on ballistics / suborbital with 6.5 km/s ? answer: 10 000 km.

1-(36/240) = 0.85

9.81*345*ln((240)/(36)) = 6420 m/s

For an all-rocket ballistic vehicle like Starship.

Now, pushing to mach 1 using turbofans can add 1100 m/s; to mach 2: 1600 m/s and to mach 3: 2000 m/s.

Of course if you use turbofans you need other bits of aircraft around it (wings, tail, undercarriage...); making difficult to stick with the mach 0.85 propellant mass fraction.

9.81*345*ln((240)/(36))+2000 = 8420 m/s - tantalizing close from orbit, but not orbit because it would need 9200 m/s.
Add 12 mt of payload: 9.81*345*ln((240+12)/(36+12))+2000 = 7612 m/s with 12 mt of payload.

Whatever, even when failing to orbit, the document below tell us (page 20 - 30 of the pdf) : a ballistic range of 12 000 km is possible, plenty enough to fly between continents.


A very good read, in passing.
 
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LowObservable

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Aerion's jet got slower and heavier with every design iteration. It's about saving time, and block time savings were unimpressive at "boomless" M=1.2, or on long trips where Aerion has to take a fuel stop and the subsonic can fly direct. And along with this you get a cabin that's positively cramped (and likely loud) compared with the latest GS and GX and the Falcon X, and you may lose access to smaller airports.

The market has changed since the early 2000s: the biggest time saving is at the supersonic's maximum range, which for Aerion was transatlantic. The Asian market, almost nonexistent when Aerion started, does not care much about transatlantic. Ground hassles are worse: nobody wants a fuel stop and everyone wants their discreet, convenient airports (Teterboro or Biggin Hill). You could argue in 2004 that you were unproductive sitting on the airplane - now you can be fully connected anywhere.

The market today may be more about convenience on the ground and privacy and security in flight than about speed. Privacy in particular, for anyone who has any public reputation, now that everyone with a phone and Twitter is part of the paparazzi.

It's very hard to break into the top-end business. GX started 30 years ago and succeeded because there was only one competitor and they were established just below Gulfstream. Now, the three players have all known the markets - big corporations and very rich people - for decades and generations. And since the market isn't wholly rational, that's a decisive advantage.
 
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Archibald

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Aerion's jet got slower and heavier with every design iteration. It's about saving time, and block time savings were unimpressive at "boomless" M=1.2, or on long trips where Aerion has to take a fuel stop and the subsonic can fly direct. And along with this you get a cabin that's positively cramped (and likely loud) compared with the latest GS and GX and the Falcon X, and you may lose access to smaller airports.

The market has changed since the early 2000s: the biggest time saving is at the supersonic's maximum range, which for Aerion was transatlantic. The Asian market, almost nonexistent when Aerion started, does not care much about transatlantic. Ground hassles are worse: nobody wants a fuel stop and everyone wants their discreet, convenient airports (Teterboro or Biggin Hill). You could argue in 2004 that you were unproductive sitting on the airplane - now you can be fully connected anywhere.

The market today may be more about convenience on the ground and privacy and security in flight than about speed. Privacy in particular, for anyone who has any public reputation, now that everyone with a phone and Twitter is part of the paparazzi.

It's very hard to break into the top-end business. GX started 30 years ago and succeeded because there was only one competitor and they were established just below Gulfstream. Now, the three players have all known the markets - big corporations and very rich people - for decades and generations. And since the market isn't wholly rational, that's a decisive advantage.

A very informative and interesting post, thank you !

or on long trips where Aerion has to take a fuel stop and the subsonic can fly direct

Frack, it is just like Concorde vs 747 on transpacific flights; Concorde had to stop in French Polynesia and this was enough for a direct flight 747 to prevail.

This won't encourage Dassault bringing back their 1999 SSBJ design from the graveyard. They must be jubilating, and think Mach 0.92 is plenty enough.
 

Reaper

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Honestly I was never sure if Aerion was ever really alive in the first place.
 

LowObservable

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Aerion had a remarkable ability to raise money and attract partners, probably because the design was technically feasible - but in the end they could not generate high confidence that it would sell.

Archibald - Honestly when Dassault unveiled the Falcon X, I thought it was bad news for Aerion.
 

Archibald

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Honestly I was never sure if Aerion was ever really alive in the first place.

"Alive but unconscious" - "just like Gerald Ford" (Airplane ! - sorry, couldn't resist the lame joke).


probably because the design was technically feasible

Honestly when Dassault unveiled the Falcon X, I thought it was bad news for Aerion.

Aerion exactly found themselves in the same situation as Dassault SSBJ back in 2000 - a perfectly fine design without a viable engine.
I heard a long time ago they wanted to use old' JT8D because they were low bypass turbofans of the first generation - just after the last civilian turbojets which themselves derived from Phantom era turbojets - supersonic ones !

That was a smart idea but not viable if only because of the old engine noise, pollution, and high fuel consumption.

Note that Dassault started the SSBJ in 1997 with similar (and equally ill-placed) hopes : "common, there must be a way to turn a F414 or M88 into a decent civilian supersonic CIVILIAN turbofan !".

Hell, no: it proved an impossible task.

I remember at the time it made me thought of Ferrari building road cars and F1 V12s - yet they were always separate lines of development because F1 engines have exciting but extremely brief lives.

I think the end of Aerion clearly show how hard it will be to get a decent supersonic bizjet engine - no existing engine can do the job and a clean sheet of paper design just burst the economic case of supersonic bizjets, barely 500 to 1000 airframe.

Dassault couldn't pull it out despite being a very robust company, an old and diversified one - one foot firmly planted in Mirages and Rafales, the other in subsonic bizjets. And even for them, the cost of a whole new engine would have sunk the SSBJ and in turn, the Falcon line, and perhaps the company: Dassault is too small to afford such a white elephant, Airbus A380 style.
In comparison, Aerion was a brand new company with none of the above: it was predictible the engine problem would kill them sooner or later. And since they had no Falcon or Mirage sales to provide money besides the supersonic bizjet program... they sunk with it.

Waiting to see how Boom and the others will tackle the issue. At least their subscale bird look awesome; smart way of attracting investors, to have a prototype flying.
 
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Archibald

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As usual with aerospace companies, there are many different breeds of them - all the way from SpaceX to Blue Origin to Virgin to Rocketplane Kistler, Bigelow and Excalibur Almaz (ranked by achievements and honesty - somewhat).

No idea where Aerion stood - but anything below Blue Origin, starts smelling pretty bad.
 

LowObservable

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Supersonic propulsion basics. Jet engines compress air, which makes it hot, and do so according to the internal aerodynamic design (pressure ratio).

However, in flight, the air also gets slowed down in the inlet (we'll stick with the conventional fiction that the engine's static and the air's moving) which also makes it hot - the faster, the hotter. That pressure/temperature rise is then multiplied by the engine's pressure ratio, so the back end of the compressor gets really hot.

High-pressure-ratio fighter engines at supersonic speed consequently run into high compressor-exit temperatures, which tend to be a limiting factor on performance (engine gonna melt) and are tolerable because max levels are seen only for a few minutes in the sortie. When Dassault started talking about cruising for hours with M88s at M=1.8 the Snecma guys pulled a weary face and said ce n'est pas aussi simple comme ca, mon vieux. The Dassault guys said oh m***e and that was that.

That's also why the F-16/79 was faster than the F100-powered standard model, why F-4s and Lightnings are faster than today's fighters - because the engines have lower pressure ratio. The EJ200 has a lower OPR than the F414, sacrificing low-end SFC but gaining high-speed performance. That's why pre-compressor cooling works too.

Early on, Aerion thought that they could just about get away with using the JT8D-200 - because it's a relatively low-OPR engine (it started as the J52) and had a high enough BPR to squeak through the noise rules. Sadly that design did not close.

Concorde too had a low-OPR engine, matched to a complex and finely tuned inlet. It was hell to develop, came closer than anyone wanted to admit to not working at all, was noisy Alfa Foxtrot and horribly inefficient at low speeds (so required fuel reserves ate your lunch on range).

GE's engine for Aerion took advantage of the fact that today's high-efficiency engines run hot too. Throttle it back a bit. Add an LP system with just enough BPR to get by on noise. But the limit was still M=1.4 and that wasn't enough to sell the airplane. RIP.

As the great GRE remarked (with colossal understatement) when someone observed that flying on Concorde was no different from any other jet: "That was the difficult bit."
 

Archibald

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Early on, Aerion thought that they could just about get away with using the JT8D-200 - because it's a relatively low-OPR engine (it started as the J52) and had a high enough BPR to squeak through the noise rules. Sadly that design did not close.

This. Exactly. You said it better and with fewer words than my little self. I'll be curious to know why, it did not close ?
 

sienar

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New airframe + new engine = failure. How many times has this succeeded, especially recently.

IMHO a baby swing wing sst, ala the boeing 733 makes the most sense. Possible to keep within the required noise envelope without needing an all new engine. Possible to get ok fuel burn sub-sonically. And perhaps most importantly the ability for billionaires to go from NYC to wherever they're used to flying their gulfstreams into. For ages the mantra has been ~300 airframes for a ssbj that is a transoceanic, major destination machine. But how much larger would the market be if that SSBJ can fly every route the larger bizjets can?

Of course a ~4% weight penalty is pretty bad. And the FAA likely makes it a no-go no matter what.
 

Archibald

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New airframe + new engine = failure. How many times has this succeeded, especially recently.

IMHO a baby swing wing sst, ala the boeing 733 makes the most sense. Possible to keep within the required noise envelope without needing an all new engine. Possible to get ok fuel burn sub-sonically. And perhaps most importantly the ability for billionaires to go from NYC to wherever they're used to flying their gulfstreams into. For ages the mantra has been ~300 airframes for a ssbj that is a transoceanic, major destination machine. But how much larger would the market be if that SSBJ can fly every route the larger bizjets can?

Of course a ~4% weight penalty is pretty bad. And the FAA likely makes it a no-go no matter what.

In a few words: CARREIDAS 160. Herge ( and Roger Leloup) you visionaries... !
 
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Zoo Tycoon

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Concorde too had a low-OPR engine, matched to a complex and finely tuned inlet.

There’s no bypass
OPR is "overall pressure ratio". You are thinking by-pass ratio.
[/QUOTE]

Sorry for the confusion, my reply was made in a bit of a hurry at this end.

A few figures to support Low Observability point;- Concorde/Oly 593 OPR subsonic 15.5:1 whereas Supersonic @ M2 its a whooping 80:1. By way of a comparison a B777 with a GE9X has an ORP of 60:1.

The matching of engine to intake to airframe is super critical, which is real problem for the maxim don’t test fly a new airframe and new engine together....... this is not like the sixties where there were a good number of minimal alteration supersonic candidates engines. It’ll be interesting to see what Boom does.
 

DrRansom

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LO - from the OPR discussion, it seems as if there are two implications:
1. Efficient supersonic cruise only happens at the Mach 1.8 to Mach 2 range, or above. Otherwise the tradeoffs are just not worthwhile.

2. Following from 1, the low-boom designs are a technological dead-end and the best approach is a near pure over-water design with high aerodynamic efficiency.
 

Archibald

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I see... not only they are ugly, but they have speed constraint ?
 

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Maybe the reason behind Aerion surprise announcement (safeguarding any impact on shares rates that will have resulted from the news below) :
GE Aviation did not elaborate beyond acknowledging that work had ceased on the Affinity, but it did note that it remains involved in the supersonic realm with the delivery last year of its F414-GE-100 engine for the NASA X-59 Quiet Supersonic Technology demonstrator. The company handed over two of the 13-foot-long engines, including one that would serve as a backup.
 

TomS

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Maybe the reason behind Aerion surprise announcement (safeguarding any impact on shares rates that will have resulted from the news below) :
GE Aviation did not elaborate beyond acknowledging that work had ceased on the Affinity, but it did note that it remains involved in the supersonic realm with the delivery last year of its F414-GE-100 engine for the NASA X-59 Quiet Supersonic Technology demonstrator. The company handed over two of the 13-foot-long engines, including one that would serve as a backup.

I suspect it's the other way around -- GE stopped work on Affinity because Aerion quit supporting it and there are no other potential customers.
 

lowboom

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The AS2 garnered much praise for its design. That praise should be restricted to aesthetics. The airframe design was never going to work in today’s regulatory environment. Those familiar with the impact of wing sweep and aspect ratio on lift curve slope and takeoff climb-out lift to drag ratio would instantly recognize that the design was not practical. In order to meet Chapter 14 noise regulation Aerion would need to further increase the bypass ratio of the Affinity engine resulting in an significant increase operating empty weight (OEW) and hence increase in MTOW that already exceeded 150k. Teterboro has a 100k GW limit. From a cruise efficiency perspective the propulsion airframe integration was very poor. Aerion no doubt had many smart engineers on their team and I am confident they did a good job of optimizing the configuration, but the basic concept was doomed to failure. The “millions” of CFD runs they performed were just ‘lipstick on a pig’. Sorry to have to be blunt, but this is not a case of inadequate propulsion technology; it is a case of a lack of appreciation for the challenges of meeting the community noise requirements and configuring the airframe (and engine) accordingly.
 

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Boom Supersonic has bigger issues than Aerion. To start, the market size for an SST is very dependent upon the operating economics. Contrast this to the metric of TVI (traditional value index) for a business jet which is (rangexspeedxcabin volume)/TOFL; which is more performance focused. On top of this, and contrary to what Blake Scholl says, the pandemic will have a negative impact on premium travel demand on commercial flights. Boom still faces the stringent community noise challenge that Aerion faced and they too will find that a very high BPR is required. This drives up OEW and MTOW, but rather than paying for this with poor operational flexibility like Aerion it will manifest itself as either very limited design range or very high fuel burn. This in turn reduces the number of routes that the aircraft can be operated on profitably. The reduced market size has the cyclical effect of increasing the cost of goods sold due to high amortization of very high non-recurring costs which further degrades the operating economics, the market size, etc etc. It is a vicious spiral of business death. Keep in mind that start-ups can publish whatever numbers they want with no accountability in the short term. What is amazing is how little due diligence VC’s perform given their resources.
 
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