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Supersonic Business Jets Advancing?  
User currently offlineA342 From Germany, joined Jul 2005, 4683 posts, RR: 3
Posted (4 years 5 months 5 hours ago) and read 5457 times:

Flightglobal, providing coverage from EBACE, has a very interesting article:

http://www.flightglobal.com/articles...upersonic-business-jet-action.html

"Gulfstream and Aerion have begun to hone their designs for a supersonic business jet (SSBJ), reigniting aspirations for a programme launch or demonstrator build in the near rather than far term."

So what chances do you see for a project going forward in the next few years? Let the speculation begin!   


Apart from that, I have a question regarding the nacelle Gulfstream tested. In that diagram, where is the fan of the engine? Unless they have (incorrently) hidden it in the engine core, I can't find it.  


Exceptions confirm the rule.
18 replies: All unread, jump to last
 
User currently onlineprebennorholm From Denmark, joined Mar 2000, 6461 posts, RR: 54
Reply 1, posted (4 years 5 months 3 hours ago) and read 5288 times:

Quoting A342 (Thread starter):
have a question regarding the nacelle Gulfstream tested. In that diagram, where is the fan of the engine?

They don't show any engine detals in the diagram.

The nacelle diagram shows in the front half the inlet which is "slowing down" the inlet to subsonic speed.

In the back half the diagram shows the whole engine - including fan and everything - as one red block.

The proposed engines - RR Tay and PW JT8D - will never work with air hitting the fan at supersonic speed. Therefore the "slow down inlet".



Always keep your number of landings equal to your number of take-offs, Preben Norholm
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 2, posted (4 years 5 months 3 hours ago) and read 5239 times:

Quoting prebennorholm (Reply 1):
The proposed engines - RR Tay and PW JT8D - will never work with air hitting the fan at supersonic speed. Therefore the "slow down inlet".

Essentially all normal supersonic jets slow the incoming air to subsonic prior to the fan face. If it works for fighters and the Concorde, it'll work for the SSBJ's.

Tom.


User currently offlineA342 From Germany, joined Jul 2005, 4683 posts, RR: 3
Reply 3, posted (4 years 4 months 4 weeks 1 day 10 hours ago) and read 4765 times:

Quoting prebennorholm (Reply 1):
In the back half the diagram shows the whole engine - including fan and everything - as one red block.

I guessed that, but I was confused by the "bypass flow", which normally refers to air which flows through the fan, but not through the engine's hot-section.
So essentially, in this nacelle, we have two bypass flows.

But now what's the purpose of the flow which bypasses the engine entirely?


Anyway, I believe Gulfstream and Aerion would be well-advised not to use old engine designs such as the Tay and JT8D. For a demonstrator, it would be OK. But a production airframe should use newer technology.
Maybe a BR725 derivative with a smaller fan and two instead of three LPT stages?



Exceptions confirm the rule.
User currently offlinePyrex From Portugal, joined Aug 2005, 4024 posts, RR: 28
Reply 4, posted (4 years 4 months 4 weeks 23 hours ago) and read 4467 times:

Quoting A342 (Thread starter):
So what chances do you see for a project going forward in the next few years? Let the speculation begin!  

I did my Master's thesis on the preliminary design of an engine for a supersonic business jet, taking the Aerion and the Gulfstream (or what was already known of them by then) as the base platforms for my specifications. I graduated in 2005...



Read this very carefully, I shall write this only once!
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 5, posted (4 years 4 months 4 weeks 21 hours ago) and read 4320 times:

Quoting A342 (Reply 3):
Anyway, I believe Gulfstream and Aerion would be well-advised not to use old engine designs such as the Tay and JT8D. For a demonstrator, it would be OK. But a production airframe should use newer technology.

You don't use new technology for the sake of using new technology, you have to have a reason. There is no way in heck that an SSBJ will ever sell enough frames to justify its own unique engine design; that means they have to use something off the shelf. There are relatively few commercial engines out there suitable to the task, but the Tay and JT8D would work, they're cheap, they're readily available, and they're reliable. Sounds like a major winner on the trade study to me.

The *only* issue with those engines in general is fuel burn, but the mere notion of an SSBJ means you don't care about fuel burn in the first place, so it's a totally moot point.

Tom.


User currently offlinecpd From Australia, joined Jun 2008, 4879 posts, RR: 38
Reply 6, posted (4 years 4 months 4 weeks 20 hours ago) and read 4253 times:

Quoting tdscanuck (Reply 2):
Essentially all normal supersonic jets slow the incoming air to subsonic prior to the fan face. If it works for fighters and the Concorde, it'll work for the SSBJ's.

Hence what he was saying, that you've essentially repeated. Did you have anything more to add, in addition to his statement?

I however believe that the SSBJs will never ever be viable in the current world climate where even efficient business jets are unacceptable for any kind of use (bad PR). It's unacceptable to drive a luxury car at the moment, do so and you'll be shouted at by other motorists with multiple expletives along with "banker...." etc. A biz-jet is the ultimate sin.

I don't believe dispensation will be given to them for supersonic overflight of populated land, the restrictions should remain in place. It will be political suicide for any administration to give dispensation for a small bunch of wealthy elite travelers to roar over land at high speed, at the expense of others.

Additionally, if the technology is available to make a plane go faster, then that technology can also be used to make it fly further, and more economically at a lower speed. That's what the majority of people want. An SSBJ would have been built long ago if their were sufficient demand. They are a nice little PR tool though, a great way of attracting attention to your company.

Is it possible to have a fixed inlet for these engines? Something like the apparent designs mooted by BAe or Aerospatiale for AST3 and Alliance 200-300 passenger SST airliners.

Still, it'll be interesting to see what Preston Henne and his people at Gulfstream can come up with. They've done some good things so far with G650.

[Edited 2010-05-06 22:13:22]

User currently offlineA342 From Germany, joined Jul 2005, 4683 posts, RR: 3
Reply 7, posted (4 years 4 months 4 weeks 14 hours ago) and read 3997 times:

Quoting tdscanuck (Reply 5):
You don't use new technology for the sake of using new technology, you have to have a reason.

Apart from fuel burn, that would be noise and emissions, plus spare parts. Fast forward two decades, those issues could be major problems for the Tay or JT8D, IMHO.

Quoting tdscanuck (Reply 5):
There is no way in heck that an SSBJ will ever sell enough frames to justify its own unique engine design

Certainly not totally unique. As I metioned, a derivative which keeps at least the high-pressure section of an existing engine would be fine.

Quoting tdscanuck (Reply 5):
The *only* issue with those engines in general is fuel burn, but the mere notion of an SSBJ means you don't care about fuel burn in the first place, so it's a totally moot point.

Ah, but you also want range.  



Exceptions confirm the rule.
User currently online2175301 From United States of America, joined May 2007, 1072 posts, RR: 0
Reply 8, posted (4 years 4 months 4 weeks 14 hours ago) and read 3977 times:

Quoting cpd (Reply 6):

I have to say that I disagree with much of your views.

Yes, while current opinion is that some things are out of vogue. The pendulum will swing back on those views in a couple years.

I think there is a real chance of a low pressure - low noise SS allowance for overland flights. It may take a while - but I think it will be in-place in a decade from now.

As far as the market for the plane. There will be a market (my guess would be 50 - 100 planes). With success in the business market I project that their could even be a larger SS a decade past that (perhaps up to 25 - 30 seats); and then limited routine passenger flights between selected cities. I do not think that there would be any sustainable use for a 50+ seat SST in the passenger market. But I do think that a 25-30 seater could find enough people on selected routes who would be willing to pay the very premium price required to support a SST (and perhaps it would be a 15 - 20 seater).

Have a great day,


User currently offlinerfields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 32
Reply 9, posted (4 years 4 months 4 weeks 10 hours ago) and read 3746 times:

I don't see a market for this concept in the US or Europe - but the Middle East and Asia might be a market. Those are some long distances where the speed would have a direct benefit.

The restrictions on super-sonic travel over populated areas may not even exist in those areas, or it could be lifted much easier than Europe and the US.

I have not heard much about NIMBY protests in Saudi Arabia, Iran, Pakistan, India, Cambodia, China, etc...


User currently offlinecpd From Australia, joined Jun 2008, 4879 posts, RR: 38
Reply 10, posted (4 years 4 months 3 weeks 6 days 23 hours ago) and read 3458 times:

Quoting A342 (Reply 7):
Apart from fuel burn, that would be noise and emissions, plus spare parts. Fast forward two decades, those issues could be major problems for the Tay or JT8D, IMHO.

First thing is that more strict noise limits will soon be enforced in a lot of airports (and ones that don't have the restrictions might add them).

For instance, Boeing 727, AN-124 and other loud planes will not be able to operate from Australian Airports soon - they will be too noisy. If the SSBJ is as loud as that, then it will not be able to arrive at Australian airports. Sydney in particular is a major business jet destination - witness the regular large numbers of large business jets coming and going (Global Express, G450, G550, Falcon 900, Falcon 7X, Citation X, BBJ, etc).

[Edited 2010-05-07 19:17:15]

User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 11, posted (4 years 4 months 3 weeks 6 days 23 hours ago) and read 3424 times:

Quoting cpd (Reply 6):
Did you have anything more to add, in addition to his statement?

Yes. Apparently, it wasn't clear. The point was that it's not just the Tay and JT8D ("the proposed engines") that need to decelerate air to subsonic prior to the fan face...that's a "feature" of all turbojets and turbofans, not a unique property to those particular engines.

Quoting cpd (Reply 6):
Is it possible to have a fixed inlet for these engines?

Yes, although you pay a price by having worse performance when you're off the inlets' design speed.

Tom.


User currently offlinePackcheer From United States of America, joined Nov 2008, 333 posts, RR: 0
Reply 12, posted (4 years 4 months 3 weeks 6 days 22 hours ago) and read 3384 times:

Could the advances of a supersonic business jet not be used at subsonic speeds to reduce drag and improve range? Then the supersonic aspect becomes an advantage when out over oceans, etc.


Things that fly, Girls and Planes...
User currently offlineThirtyEcho From United States of America, joined Dec 2001, 1653 posts, RR: 1
Reply 13, posted (4 years 4 months 3 weeks 6 days 22 hours ago) and read 3329 times:

There is more to this than engines. I try to avoid politics on this site at all costs but I think that the first American corporation that buys or leases an SSBJ is going to get seized by the government and broken up into tiny pieces. If it is a company that got bailout funds then folks are going to go to jail.

That isn't my sense of justice, necessarily, but it is the current climate.


User currently offlineairbazar From United States of America, joined Sep 2003, 8413 posts, RR: 10
Reply 14, posted (4 years 4 months 3 weeks 5 days 23 hours ago) and read 3004 times:

Quoting rfields5421 (Reply 9):
The restrictions on super-sonic travel over populated areas may not even exist in those areas, or it could be lifted much easier than Europe and the US.

I didn't think those restrictions applied to private jets, only commercial.


User currently offlinejeb94 From United States of America, joined Oct 2004, 602 posts, RR: 5
Reply 15, posted (4 years 4 months 3 weeks 5 days 17 hours ago) and read 2818 times:

Quoting cpd (Reply 10):
First thing is that more strict noise limits will soon be enforced in a lot of airports (and ones that don't have the restrictions might add them).

For instance, Boeing 727, AN-124 and other loud planes will not be able to operate from Australian Airports soon - they will be too noisy. If the SSBJ is as loud as that, then it will not be able to arrive at Australian airports. Sydney in particular is a major business jet destination - witness the regular large numbers of large business jets coming and going (Global Express, G450, G550, Falcon 900, Falcon 7X, Citation X, BBJ, etc).

The AN-124 isn't any louder really than a C-5 or 747. Yes I've heard them take off. As for a pair of JT8D-217/219 engines for the SSBJ, they probably won't be any louder on take-off than the MD-80, which is quieter than a 727. As for the supersonic overflight of land bans, they were put in place due to the sonic booms produced by Concorde. A big part of it was politics. If these aircraft don't produce much, if any, boom then it'll be lifted. Large corporations still need corporate jets as they are time and money savers. Even the US congress knows this, despite their political grandstanding. At the same time as they were blasting the automakers for using corporate jets they were trying to force the US Airforce to buy five corporate jets for congressional use.


User currently onlinerangercarp From United States of America, joined Nov 2009, 144 posts, RR: 0
Reply 16, posted (4 years 4 months 3 weeks 5 days 13 hours ago) and read 2639 times:

Quoting ThirtyEcho (Reply 13):
the first American corporation that buys or leases an SSBJ is going to get seized by the government and broken up into tiny pieces. If it is a company that got bailout funds then folks are going to go to jail.

As long as they don't fly them to Washington to testify before congress about their failing company few people will ever notice and fewer still will care.



iwgbtp!
User currently offlinerwessel From United States of America, joined Jan 2007, 2353 posts, RR: 2
Reply 17, posted (4 years 4 months 3 weeks 3 days 19 hours ago) and read 2191 times:
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Quoting airbazar (Reply 14):
I didn't think those restrictions applied to private jets, only commercial.

In the US, it's basically a blanket ban on supersonic flight over the US, or near enough to the coast that the sonic boom can reach land. See FAR 91.817. In fact the regs actually ban the operation of any aircraft capable* of supersonic flight over or near the US, unless there are specific flight limitations in place, and known to the crew, to ensure that the aircraft does not actually exceed Mach 1. The normally allowed exceptions are basically only for limited types of test flights (see 91.B). Anything else would require a special exception.


*defined has having an MMO greater than 1.0 - so it doesn't include subsonic aircraft that have been tested in a dive to a slightly supersonic speed.


User currently offlinedw747400 From United States of America, joined Aug 2001, 1260 posts, RR: 1
Reply 18, posted (4 years 4 months 3 weeks 3 days 18 hours ago) and read 2142 times:

We're getting into a situation where the top of the corporate market is separating into two distinct categories. The first is seeking the ultimate in comfort, either through converting existing airliners or buying BBJ/ACJ aircraft new. A380s and 747-8Is in VIP configs show that some value size and comfort above all else.

The second category is based in performance. For lack of a better term, these jets are meant to be practical. Obviously at the top of the market the are hardly utilitarian, but the goal is to transport VIPs long distances in the shortest possible time. After all, corporate aviation is all about supporting those who view their time as worth a lot of money. You can reduce travel time by being more direct (longer range) or going faster. The G650 is the champion in this category (or soon will be).

The second category is where the SSBJ fits in. Shaving 30%+ off travel time is a huge deal in this market. The value that the users of top-end jets put on their time is so high, the extra costs of an SSBJ aren't really a factor.

Quoting cpd (Reply 6):
I however believe that the SSBJs will never ever be viable in the current world climate where even efficient business jets are unacceptable for any kind of use (bad PR).

The orderbook for the G650 certainly doesn't suggest that the market is drying up. The US market is still surprisingly strong for the biggest Gulfstream ever-- some folks want the top of the line no matter what.

Quoting cpd (Reply 6):
An SSBJ would have been built long ago if their were sufficient demand. They are a nice little PR tool though, a great way of attracting attention to your company.

The business jet market is evolving, and continues to support more and more expensive aircraft. As technology improves, the price of performance decreases. When these two trends intersect, you'll see the SSBJ.

Quoting A342 (Reply 7):
Apart from fuel burn, that would be noise and emissions, plus spare parts. Fast forward two decades, those issues could be major problems for the Tay or JT8D, IMHO.

The lower bypass ratio of the early engines is better for supersonic flight. Whether it is easier/cheaper to adapt the engine to the airframe or it just performs better at supersonic speed, I'm pretty confident the designers have a good reason for sticking with older engines. they may be easier to work with and/or cheaper to operate, but your second point still stands. Parts support could be a problem.



CFI--Certfied Freakin Idiot
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