Forum: Technology

bigbird2 wrote:

I think a 10-12 passenger jet powered by two F414 flying at mach 1.8 is possible. Not sure it meets commercial flying load. The proposed Aerion uses smaller thrust engine. (2× Pratt & Whitney JT8D-219 turbofans, 19,600 lbf (87.19 kN) each)

You have a decent choice, except that the MIL (maximum non-AB power) of the F414 is considerably less than the JT8D-219. The JT8D would have better take-off and noise performance IMO as it has almost 3x the amount of mass flow. The deciding factor would be the usable thrust at MACH 1.6 / 40K feet. This would greatly depend on the inlet/nozzle configuration. The For a small SBJ it may work just fine; seems Dassault has been barking up that tree too.

F414-GE-400
(MIL) 14,700lbs @ 0.840 lb/HR/lb st
(MAX) 22,000lbs @ 1.850 lb/HR/lb st
BPR 0.27
OPR 30
Mass flow 172lbs/sec

F414BJ

Quote:

Though merely a study programme, Dassault has selected an unaugmented version of the F414 (F414BJ) for its proposed supersonic business jet. The engine for this application would be rated at about 57.8 kN (13,000 lb st), but GE does not at present have plans to build and test such an engine.

JT8D-219
(MIL) 19,600lbs @ 0.737 lb/Hr/lb st
(MAX) *same as MIL, no AB fitted*
BPR 1.74
OPR 19.4
Mass Flow 488lbs/sec (221 kg/s)

Quote:

In 2004, Aerion announced that the engines would be flat-rated for takeoff at sea level at 80 kN (18,000 lb st); in 2005, this flat-rating was upgraded to 87.2 kN (19,600 lb st), able to power the SBJ to Mach 1.6 without afterburning.

I still highly doubt super-sonic airline or biz-jet travel will NOT enter main-stream any time soon due to the high costs involved. Two Cents

Keep 'em flyin' Thumb

TEG

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Elite 1K Joined: May 26, 2005 - 08:39 PM Posts: 1496

That_Engine_Guy wrote:

I still highly doubt super-sonic airline or biz-jet travel will NOT enter main-stream any time soon due to the high costs involved. Two Cents

Totally agree with you on airliners, just too damn expensive. Drag goes up with the square of velocity and too many people want the cheapest fare possible, no exceptions.

Business jets though, that may be different. Someone who owns a G550 has already very loudly stated they value time over money, having a supersonic private jet that has a 50% or 100% higher fuel burn may not be a deal breaker. Also add in the prestige of saying your jet can bust the Mach, there are some rich folks who spend silly amounts of cash just to have a yacht that's 1' longer for bragging rights.

But I suppose the real question is, is there ENOUGH demand to support such an aircraft.

For long range hauls - such as trans-oceanic flights - I see value for the faster run. Maybe not for just any crowd, V.I.P. crowds only.

bigbird2 wrote:

[I think a 10-12 passenger jet powered by two F-414 flying at mach 1.8 is possible. Not sure it meets commercial flying load. The proposed Aerion uses smaller thrust engine. (2× Pratt & Whitney JT8D-219 turbofans, 19,600 lbf (87.19 kN) each)

http://en.wikipedia.org/wiki/Aerion_SBJ

I believe you´re a bit optimistic. 6 maybe 8 passengers would maybe be possible if you can get them to accept a small cabin. I saw a study made by one of the old aerodynamic pros at our company and with two RM12 engines (RM12 is based on F404) it would be able to haul 6 passengers (with creditcards and toothbrushes) across the atlantic at more than M=1.5 (don't remember the exact figure)

If you use the JT8D you have the problem with slenderness, since it's a pretty big engine. The same guy made studies of an SSBJ with two RM8B engines (An JT8D with BPR of 1 and an afterburner) but I don't remember any performance figures.

And then you have the problem with the sonic boom, economy etc. But the SSBJ airplane shure looked good!

That_Engine_Guy wrote:

You have a decent choice, except that the MIL (maximum non-AB power) of the F414 is considerably less than the JT8D-219. The JT8D would have better take-off and noise performance IMO as it has almost 3x the amount of mass flow. The deciding factor would be the usable thrust at MACH 1.6 / 40K feet. This would greatly depend on the inlet/nozzle configuration. The For a small SBJ it may work just fine; seems Dassault has been barking up that tree too.

Thrust is not everything, the increased diameter of the JT8D means a less slender airplane wich means more wavedrag, and I'm not sure it can be offseted. And more thrust means more fuel that gives you heavyer structure meaning that you needs to scale up the wing etc.
The only thing that is non scaleable is the passengers.

bigbird2 wrote:

yeah but SR-71 needed 4-5 air refueling in typical mission.

And Concord was a big commercial fail. After 70's oil shock it was pretty much over. Few nickles gas price change/gal means the ticket price changes by a thousand bucks. (ticket price in 2000 was $8000) At current gas price, it would be probably around $12K one way. It wouldn't make it economically no matter how marvelous that plane was. It needed to be 3-4 times more fuel efficient. Even today it's still nearly impossible to do. The shape of the wing is just not efficient for taking off. Think mig-21 or Mirage made out of lead. A supersonic that size probably would be a modified B-1B, with variable geometry wing to increase fuel efficiency during slow speed.

Not quite.
British Airways made Concorde into a commercial success, just ask business flyers about prices.... Concorde MADE money it didnt lose it. I recently saw a tv show about Concorde`s early days with the airline, where it operated at a loss, but they turned it around.

SR-71 may have needed 4-5 refuelings, but it flew across the planet. At Mach 3.2 the B.Bird could rocket along for nearly 2,600 nm before coming down to gas up. 4-5 refuelings makes for 10,400 to 13,000 nm. With the planet only being 20,000nm around, that leaves the Blackbird being based a quarter of the globe away. And talk about valuing time over money, LA to DC in an hour... Take out the camera bay and put in seats, you only have to charge $100,000/ticket and make them wear space suits!

Forum: Technology

Concorde and Supercruise