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Quiet supersonic planes
Posted by: freeradical
Date: October 31, 2019 03:27PM
Is this for real?

Quote


In partnership with NASA, the Lockheed Martin Skunk Works team is solving one of the most persistent challenges of supersonic flight – the sonic boom. NASA awarded Lockheed Martin Skunk Works a contract in February 2016 for the preliminary design of X-59, designed to reduce a sonic boom to a gentle thump.

In 2018, Lockheed Martin Skunk Works was selected for the design, build and flight test of the Low-Boom Flight Demonstrator (LBFD). The X-59 aircraft will collect community response data on the acceptability of the quiet sonic boom generated by our design, helping NASA establish an acceptable commercial supersonic noise standard to overturn current regulations banning supersonic travel over land. This would open the door to an entirely new global market for aircraft manufacturers, enabling passengers to travel anywhere in the world in half the time it takes today.

X-59 is designed to cruise at 55,000 feet at a speed of about 940 mph and create a sound about as loud as a car door closing, 75 Perceived Level decibel (PLdB), instead of a sonic boom.

[www.lockheedmartin.com]
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Re: Quiet supersonic planes
Posted by: Paul F.
Date: October 31, 2019 03:33PM
Probably... though it's the first I've heard of this particular project.
There are several aircraft makers in the last decade or so that have flirted with the idea of a 21st century supersonic passenger aircraft. Other than operational costs like fuel, the biggest stopping point has been routes they'd be allowed to fly. If a demonstrator project like this can open up routes, and the problems of fuel and maintenance costs can be managed.... we'll have a second generation of supersonic transport!

My idea has always been, "drive it HIGHER". Thanks to the inverse-square law, and thinner air, sonic booms from altitudes above 100,000 feet would be similarly greatly reduced. Of course, flying at 100,000 feet brings its own set of problems...



Paul F.
-----
A sword never kills anybody; it is a tool in the killer's hand. - Lucius Annaeus Seneca c. 5 BC - 65 AD
----
Good is the enemy of Excellent. Talent is not necessary for Excellence.
Persistence is necessary for Excellence. And Persistence is a Decision.

--

--

--
Eureka, CA
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Re: Quiet supersonic planes
Posted by: jdc
Date: October 31, 2019 03:44PM
Its a real program, but no plane built yet.



----


Edited 999 time(s). Last edit at 12:08PM by jdc.
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Re: Quiet supersonic planes
Posted by: ztirffritz
Date: October 31, 2019 03:52PM
As Paul mentioned, there are several companies currently working on supersonic passenger/business jets.

[boomsupersonic.com]

[www.aerionsupersonic.com]

[www.spikeaerospace.com]
Spike specifically claims a 'low sonic boom'



**************************************
MacResource User Map: [www.zeemaps.com]#
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Re: Quiet supersonic planes
Posted by: Will Collier
Date: October 31, 2019 04:44PM
Quote
Paul F.
Probably... though it's the first I've heard of this particular project.
There are several aircraft makers in the last decade or so that have flirted with the idea of a 21st century supersonic passenger aircraft. Other than operational costs like fuel, the biggest stopping point has been routes they'd be allowed to fly. If a demonstrator project like this can open up routes, and the problems of fuel and maintenance costs can be managed.... we'll have a second generation of supersonic transport!

My idea has always been, "drive it HIGHER". Thanks to the inverse-square law, and thinner air, sonic booms from altitudes above 100,000 feet would be similarly greatly reduced. Of course, flying at 100,000 feet brings its own set of problems...

Besides which, while a sonic boom is not nothing, but it's far from the only noise a high-powered jet makes. Take it from somebody who's lived near fighter jets for about the last 25 years, they don't have to be supersonic to be really loud on takeoff and landing....
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Re: Quiet supersonic planes
Posted by: mrlynn
Date: October 31, 2019 04:48PM
Quote
Will Collier
Quote
Paul F.
Probably... though it's the first I've heard of this particular project.
There are several aircraft makers in the last decade or so that have flirted with the idea of a 21st century supersonic passenger aircraft. Other than operational costs like fuel, the biggest stopping point has been routes they'd be allowed to fly. If a demonstrator project like this can open up routes, and the problems of fuel and maintenance costs can be managed.... we'll have a second generation of supersonic transport!

My idea has always been, "drive it HIGHER". Thanks to the inverse-square law, and thinner air, sonic booms from altitudes above 100,000 feet would be similarly greatly reduced. Of course, flying at 100,000 feet brings its own set of problems...

Besides which, while a sonic boom is not nothing, but it's far from the only noise a high-powered jet makes. Take it from somebody who's lived near fighter jets for about the last 25 years, they don't have to be supersonic to be really loud on takeoff and landing....

Any reason why supersonic passenger planes couldn't have subsonic modes for take-off, landing, and low-level flight?

/Mr Lynn



"Hillbilly at Harvard"
Honky-tonk Country and Bluegrass
Founded in 1948 by Pappy Ben Minnich
Saturdays 9am - 1pm Eastern
WHRB-FM, Cambridge, MA
Streaming at [www.WHRB.org]
Be there!

The HAH weblog: [hillbillyatharvard.wordpress.com]

Topical weblog: [walkingcreekworld.wordpress.com]

On the river in Saxonville.
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Re: Quiet supersonic planes
Posted by: Will Collier
Date: October 31, 2019 04:56PM
Quote
mrlynn
Quote
Will Collier
Quote
Paul F.
Probably... though it's the first I've heard of this particular project.
There are several aircraft makers in the last decade or so that have flirted with the idea of a 21st century supersonic passenger aircraft. Other than operational costs like fuel, the biggest stopping point has been routes they'd be allowed to fly. If a demonstrator project like this can open up routes, and the problems of fuel and maintenance costs can be managed.... we'll have a second generation of supersonic transport!

My idea has always been, "drive it HIGHER". Thanks to the inverse-square law, and thinner air, sonic booms from altitudes above 100,000 feet would be similarly greatly reduced. Of course, flying at 100,000 feet brings its own set of problems...

Besides which, while a sonic boom is not nothing, but it's far from the only noise a high-powered jet makes. Take it from somebody who's lived near fighter jets for about the last 25 years, they don't have to be supersonic to be really loud on takeoff and landing....

Any reason why supersonic passenger planes couldn't have subsonic modes for take-off, landing, and low-level flight?

/Mr Lynn

No, because they certainly will be subsonic in those flight modes. Besides the obvious safety issues, because the speed of sound is higher at lower altitudes and thus it takes more energy and fuel to go supersonic, even military high speed jets rarely get above the Mach under, say 20,000 feet except in dire circumstances.

There's a supersonic corridor above the Appalachian Mountains north of Atlanta for F-22 flight tests. It avoids populated areas, but if you're in south Cobb County, you still know when one takes off or lands.
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Re: Quiet supersonic planes
Posted by: space-time
Date: October 31, 2019 05:29PM
We had MIGs go supersonic over my hometown (200k) all the time.
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Re: Quiet supersonic planes
Posted by: Will Collier
Date: October 31, 2019 05:30PM
Quote
space-time
We had MIGs go supersonic over my hometown (200k) all the time.

Where was that?
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Re: Quiet supersonic planes
Posted by: Lew Zealand
Date: October 31, 2019 05:40PM
I think s-t used to live in Romania?
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Re: Quiet supersonic planes
Posted by: JoeH
Date: October 31, 2019 05:51PM
Quote
Will Collier
Quote
Paul F.
Probably... though it's the first I've heard of this particular project.
There are several aircraft makers in the last decade or so that have flirted with the idea of a 21st century supersonic passenger aircraft. Other than operational costs like fuel, the biggest stopping point has been routes they'd be allowed to fly. If a demonstrator project like this can open up routes, and the problems of fuel and maintenance costs can be managed.... we'll have a second generation of supersonic transport!

My idea has always been, "drive it HIGHER". Thanks to the inverse-square law, and thinner air, sonic booms from altitudes above 100,000 feet would be similarly greatly reduced. Of course, flying at 100,000 feet brings its own set of problems...

Besides which, while a sonic boom is not nothing, but it's far from the only noise a high-powered jet makes. Take it from somebody who's lived near fighter jets for about the last 25 years, they don't have to be supersonic to be really loud on takeoff and landing....

They can be loud enough just flying over. There is an ANG unit in Westfield flying F-15C's. They fly over this area regularly at least 10,000 feet up and are definitely a loud rumble. Occasionally they do training at lower altitudes, that is very loud.
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Re: Quiet supersonic planes
Posted by: Will Collier
Date: October 31, 2019 05:57PM
Quote
JoeH
Quote
Will Collier
Quote
Paul F.
Probably... though it's the first I've heard of this particular project.
There are several aircraft makers in the last decade or so that have flirted with the idea of a 21st century supersonic passenger aircraft. Other than operational costs like fuel, the biggest stopping point has been routes they'd be allowed to fly. If a demonstrator project like this can open up routes, and the problems of fuel and maintenance costs can be managed.... we'll have a second generation of supersonic transport!

My idea has always been, "drive it HIGHER". Thanks to the inverse-square law, and thinner air, sonic booms from altitudes above 100,000 feet would be similarly greatly reduced. Of course, flying at 100,000 feet brings its own set of problems...

Besides which, while a sonic boom is not nothing, but it's far from the only noise a high-powered jet makes. Take it from somebody who's lived near fighter jets for about the last 25 years, they don't have to be supersonic to be really loud on takeoff and landing....

They can be loud enough just flying over. There is an ANG unit in Westfield flying F-15C's. They fly over this area regularly at least 10,000 feet up and are definitely a loud rumble. Occasionally they do training at lower altitudes, that is very loud.

Yep. I lived under the Tyndall AFB approach for about four years. After a while I didn't even notice, though.
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Re: Quiet supersonic planes
Posted by: freeradical
Date: October 31, 2019 06:01PM
Jet noise is the sound of freedom.


grinning smiley
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Re: Quiet supersonic planes
Posted by: Paul F.
Date: October 31, 2019 06:01PM
I've been at an Air Show when F-15's took off. And C-130's, and a B-29, and B-17, P-38... F-18's, F-16's... and ones I've forgotten.

Even with some of those on afterburner, without a doubt, the LOUDEST aircraft I've ever heard on takeoff was a WWII torpedo bomber... I THINK it was a TBM Avenger, but it may have been some other model. Louder than I though possible for a prop aircraft, OR a jet aircraft for that matter.

The sonic boom is important, but yes, so is the engine noise.



Paul F.
-----
A sword never kills anybody; it is a tool in the killer's hand. - Lucius Annaeus Seneca c. 5 BC - 65 AD
----
Good is the enemy of Excellent. Talent is not necessary for Excellence.
Persistence is necessary for Excellence. And Persistence is a Decision.

--

--

--
Eureka, CA
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Re: Quiet supersonic planes
Posted by: freeradical
Date: October 31, 2019 06:03PM
Prop aircraft can be very loud.

I understand that the tips of the propellers on the TU-95 have a supersonic linear velocity.
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Re: Quiet supersonic planes
Posted by: space-time
Date: October 31, 2019 06:05PM
Quote
Will Collier
Quote
space-time
We had MIGs go supersonic over my hometown (200k) all the time.

Where was that?

Bacau, Romania.

Edit: that was before 1989. I don’t think they are allowed to do that these days, I don’t recall hearing the sonic boom last time I was there.



Edited 1 time(s). Last edit at 10/31/2019 06:07PM by space-time.
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Re: Quiet supersonic planes
Posted by: Ombligo
Date: October 31, 2019 06:37PM
The double sonic booms (one from the nose, one from the wings) was how I knew the Space Shuttle was landing. The approach was over my house and something like 80,000 feet. The thing had to do a serious dive to get from that altitude at my house to ground level at Kennedy - about 100 miles away.



“No persons are more frequently wrong, than those who will not admit they are wrong.”
-- François de La Rochefoucauld
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Re: Quiet supersonic planes
Posted by: Thrift Store Scott
Date: October 31, 2019 06:39PM
Quote
space-time
We had MIGs go supersonic over my hometown (200k) all the time.

Same with F-4s here in Birmingham when the Viet Nam war was still going on. If you saw one but didn't hear it at all as it went streaking by overhead, you knew to brace yourself for the sonic boom that was sure to follow. They were loud, sure, but the... I suppose the correct word is "concussive" effect of a sonic boom in the air is what really got your attention.



Lie to me if you must, but don't lie to me and insult my intelligence in the same sentence.

Resist the Thought Police: George Orwell's book 1984 was meant as a warning, not an instruction manual.

"Political correctness is just intellectual colonialism and psychological fascism for the creation of thought crime" - Steve Hughes

Stop and think about this: If you're able to shout the words "I CAN'T BREATHE!!!" at considerable volume, then you have just proven to anyone listening that you can indeed breathe.

"I don't see color, I just see ugly" - Joe Jitsukawa



Edited 1 time(s). Last edit at 11/01/2019 03:49PM by Thrift Store Scott.
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Re: Quiet supersonic planes
Posted by: freeradical
Date: October 31, 2019 06:46PM
Quote
Ombligo
The double sonic booms (one from the nose, one from the wings) was how I knew the Space Shuttle was landing. The approach was over my house and something like 80,000 feet. The thing had to do a serious dive to get from that altitude at my house to ground level at Kennedy - about 100 miles away.

When I was in the service, I worked with a guy who had a special duty assignment maintaining the Instrument Landing System where the shuttle landed. He said that it flew the Glideslope's second course with "true sensing". If a Glideslope is set up with a 3 degree glide angle, you get a course at 6 degrees with false sensing, and then another course with "true sensing" at 9 degrees.

It came in like a stone.

[en.wikipedia.org]
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Re: Quiet supersonic planes
Posted by: mrlynn
Date: October 31, 2019 08:58PM
Quote
Will Collier
Quote
mrlynn
Quote
Will Collier
Quote
Paul F.
Probably... though it's the first I've heard of this particular project.
There are several aircraft makers in the last decade or so that have flirted with the idea of a 21st century supersonic passenger aircraft. Other than operational costs like fuel, the biggest stopping point has been routes they'd be allowed to fly. If a demonstrator project like this can open up routes, and the problems of fuel and maintenance costs can be managed.... we'll have a second generation of supersonic transport!

My idea has always been, "drive it HIGHER". Thanks to the inverse-square law, and thinner air, sonic booms from altitudes above 100,000 feet would be similarly greatly reduced. Of course, flying at 100,000 feet brings its own set of problems...

Besides which, while a sonic boom is not nothing, but it's far from the only noise a high-powered jet makes. Take it from somebody who's lived near fighter jets for about the last 25 years, they don't have to be supersonic to be really loud on takeoff and landing....

Any reason why supersonic passenger planes couldn't have subsonic modes for take-off, landing, and low-level flight?

/Mr Lynn

No, because they certainly will be subsonic in those flight modes. Besides the obvious safety issues, because the speed of sound is higher at lower altitudes and thus it takes more energy and fuel to go supersonic, even military high speed jets rarely get above the Mach under, say 20,000 feet except in dire circumstances.

There's a supersonic corridor above the Appalachian Mountains north of Atlanta for F-22 flight tests. It avoids populated areas, but if you're in south Cobb County, you still know when one takes off or lands.

I meant, any reason why SSTs couldn't use engines that were quiet at low (subsonic) speeds?

/Mr Lynn
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Re: Quiet supersonic planes
Posted by: Bixby
Date: October 31, 2019 09:50PM
I've always thought this was highly informative and engaging video on landing the space shuttle: https://www.youtube.com/watch?v=Jb4prVsXkZU
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Re: Quiet supersonic planes
Posted by: Thrift Store Scott
Date: October 31, 2019 11:36PM
Quote
mrlynn
Quote
Will Collier
Quote
mrlynn
Quote
Will Collier
Quote
Paul F.
Probably... though it's the first I've heard of this particular project.
There are several aircraft makers in the last decade or so that have flirted with the idea of a 21st century supersonic passenger aircraft. Other than operational costs like fuel, the biggest stopping point has been routes they'd be allowed to fly. If a demonstrator project like this can open up routes, and the problems of fuel and maintenance costs can be managed.... we'll have a second generation of supersonic transport!

My idea has always been, "drive it HIGHER". Thanks to the inverse-square law, and thinner air, sonic booms from altitudes above 100,000 feet would be similarly greatly reduced. Of course, flying at 100,000 feet brings its own set of problems...

Besides which, while a sonic boom is not nothing, but it's far from the only noise a high-powered jet makes. Take it from somebody who's lived near fighter jets for about the last 25 years, they don't have to be supersonic to be really loud on takeoff and landing....

Any reason why supersonic passenger planes couldn't have subsonic modes for take-off, landing, and low-level flight?

/Mr Lynn

No, because they certainly will be subsonic in those flight modes. Besides the obvious safety issues, because the speed of sound is higher at lower altitudes and thus it takes more energy and fuel to go supersonic, even military high speed jets rarely get above the Mach under, say 20,000 feet except in dire circumstances.

There's a supersonic corridor above the Appalachian Mountains north of Atlanta for F-22 flight tests. It avoids populated areas, but if you're in south Cobb County, you still know when one takes off or lands.

I meant, any reason why SSTs couldn't use engines that were quiet at low (subsonic) speeds?

/Mr Lynn

A sonic boom is when an object travels faster than the speed of sound which causes a cone-shaped shock wave to radiate backwards from the object, that shock wave exhibits a concussive effect when it reaches the ground. The engines themselves play no direct part in a sonic boom.

Aircraft engines today are dramatically quieter than they were when the Concorde was designed so they're not really the problem, the sonic boom itself is.



Lie to me if you must, but don't lie to me and insult my intelligence in the same sentence.

Resist the Thought Police: George Orwell's book 1984 was meant as a warning, not an instruction manual.

"Political correctness is just intellectual colonialism and psychological fascism for the creation of thought crime" - Steve Hughes

Stop and think about this: If you're able to shout the words "I CAN'T BREATHE!!!" at considerable volume, then you have just proven to anyone listening that you can indeed breathe.

"I don't see color, I just see ugly" - Joe Jitsukawa
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Re: Quiet supersonic planes
Posted by: mrbigstuff
Date: October 31, 2019 11:46PM
When I lived near Otis Air Force base for a time, I am pretty certain that I saw (and felt) the loudest sound I had ever heard until that time (and until this day). I don't know what it was but I had to drop what I was holding and cover my ears. when I looked up all I saw was black covering the sky (I was very close to the base and it was LOW).
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Re: Quiet supersonic planes
Posted by: Carnos Jax
Date: November 01, 2019 01:52AM
Quote
Thrift Store Scott
Quote
mrlynn
Quote
Will Collier
Quote
mrlynn
Quote
Will Collier
Quote
Paul F.
Probably... though it's the first I've heard of this particular project.
There are several aircraft makers in the last decade or so that have flirted with the idea of a 21st century supersonic passenger aircraft. Other than operational costs like fuel, the biggest stopping point has been routes they'd be allowed to fly. If a demonstrator project like this can open up routes, and the problems of fuel and maintenance costs can be managed.... we'll have a second generation of supersonic transport!

My idea has always been, "drive it HIGHER". Thanks to the inverse-square law, and thinner air, sonic booms from altitudes above 100,000 feet would be similarly greatly reduced. Of course, flying at 100,000 feet brings its own set of problems...

Besides which, while a sonic boom is not nothing, but it's far from the only noise a high-powered jet makes. Take it from somebody who's lived near fighter jets for about the last 25 years, they don't have to be supersonic to be really loud on takeoff and landing....

Any reason why supersonic passenger planes couldn't have subsonic modes for take-off, landing, and low-level flight?

/Mr Lynn

No, because they certainly will be subsonic in those flight modes. Besides the obvious safety issues, because the speed of sound is higher at lower altitudes and thus it takes more energy and fuel to go supersonic, even military high speed jets rarely get above the Mach under, say 20,000 feet except in dire circumstances.

There's a supersonic corridor above the Appalachian Mountains north of Atlanta for F-22 flight tests. It avoids populated areas, but if you're in south Cobb County, you still know when one takes off or lands.

I meant, any reason why SSTs couldn't use engines that were quiet at low (subsonic) speeds?

/Mr Lynn

A sonic boom is when an object travels faster than the speed of sound which causes a cone-shaped shock wave to radiate backwards from the object, that shock wave exhibits a concussive effect when it reaches the ground. The engines themselves play no direct part in a sonic boom.

Aircraft engines today are dramatically quieter than they were when the Concorde was designed so they're not really the problem, the sonic boom itself is.


To possibly shed some additional light on the situation with some educated speculation on my part, while engines have dramatically improved in efficiency since the days of the Concord, part of the reason why it (and many fighters today) are loud during takeoff, is due to the use of afterburners. And the reason they use these is because those engines tend to be pure turbojets or low bypass turbofans. Such engines are best for supersonic air speeds. But they can’t produce as much thrust as the high bypass turbofans used on today’s airliners. Then again high bypass turbofans are no good for supersonic travel.. there may need to be some innovation in this area. Maybe some kind of hybrid design that route air through the core of the engine only as the speed increases.
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Re: Quiet supersonic planes
Posted by: Article Accelerator
Date: November 01, 2019 01:58AM
Quote
freeradical
Prop aircraft can be very loud.

I understand that the tips of the propellers on the TU-95 have a supersonic linear velocity.

I hope not. That would be a dangerous condition.

[tinyurl.com] (links to wikipedia)
[en.wikipedia.org]
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Re: Quiet supersonic planes
Posted by: freeradical
Date: November 01, 2019 02:05AM
Quote
Carnos Jax
To possibly shed some additional light on the situation with some educated speculation on my part, while engines have dramatically improved in efficiency since the days of the Concord, part of the reason why it (and many fighters today) are loud during takeoff, is due to the use of afterburners. And the reason they use these is because those engines tend to be pure turbojets or low bypass turbofans. Such engines are best for supersonic air speeds. But they can’t produce as much thrust as the high bypass turbofans used on today’s airliners. Then again high bypass turbofans are no good for supersonic travel.. there may need to be some innovation in this area. Maybe some kind of hybrid design that route air through the core of the engine only as the speed increases.


Quote

Truly game-changing breakthroughs in US fighter engines are nearly in hand. After more than a decade of labor by Air Force Research Laboratory and engine-makers Pratt & Whitney and General Electric Aviation, increases in speed and range, reduced dependency on tankers, and a menu of new tactics are just some of the advantages coming in the next few years.

By 2021, engineers are expected to have built and tested flightworthy engines that could, for example, give new fighters 30 percent more range than they have today, produce enough spare power to fire directed energy weapons, or run cool enough to improve stealth. Besides those advantages, new engines could provide great benefit to the F-35 strike fighter, allowing it to sustain high-speed flight at treetop altitudes, something it can’t do today. The work is advanced enough that, given a green light, a new development program with a short execution time line could be launched and start producing new power plants by the early 2020s.

So significant are the improvements that the new engine technology effort has been exempt from recent budget cuts, to quicken the pace that the new power plants can be deployed in the inventory.

“We’ve gained tremendous insight from our experience designing engines for the F-22 and the F-35, which are truly a generation ahead,” said Pratt & Whitney’s James Kenyon, senior director of advanced programs and technology, in a 2016 news release. Subsequent development—funded by the Air Force, Navy, and in-house—have yielded “tremendous progress” since 2012 and “we’re eager to move into the next phase of adaptive engine development,” he said.

That next phase is the Adaptive Engine Transition Program, or AETP, a five-year project that began last summer with $1 billion contracts each to Pratt & Whitney and General Electric Aviation. It will refine and mature technologies developed in the Adaptive Engine Technology Development program, launched in 2012 and concluding this year.

The term “adaptive” refers to an engine that can change its internal geometry to be efficient in a variety of missions and flight conditions.


[www.airforcemag.com]
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Re: Quiet supersonic planes
Posted by: JoeH
Date: November 01, 2019 02:29AM
Quote
Article Accelerator
Quote
freeradical
Prop aircraft can be very loud.

I understand that the tips of the propellers on the TU-95 have a supersonic linear velocity.

I hope not. That would be a dangerous condition.

[tinyurl.com] (links to wikipedia)
[en.wikipedia.org]

Actually quite true. The TU-95 is not the only plane to have flown with propellor tips in the supersonic regime, probably just the one flown over the largest number of years. Its turboprops have 8-bladed contra-rotating propellors.

As for the Scimitar bladed propellors, development of those came years later as suitable materials to construct them became available.
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Re: Quiet supersonic planes
Posted by: Ombligo
Date: November 01, 2019 04:09AM
Quote
Bixby
I've always thought this was highly informative and engaging video on landing the space shuttle: https://www.youtube.com/watch?v=Jb4prVsXkZU

Wait, this isn't an instructional video documentary on how to land a shuttle? - [www.youtube.com]



“No persons are more frequently wrong, than those who will not admit they are wrong.”
-- François de La Rochefoucauld
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Re: Quiet supersonic planes
Posted by: mrlynn
Date: November 01, 2019 07:12AM
Thanks Carnos Jax and freeradical, for addressing my question (which was in response to Will Collier's point that, besides sonic boom, SSTs would be too loud at and near airports).

The answer is clearly some kind of hybrid engine(s) that could switch from low-speed high-speed modes. As I recall, a British company was working on a combination turbo-fan and ramjet to address these concerns.

Or an SST could conceivably carry two kinds of engines, which of course would add a lot of weight.

/Mr Lynn
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Re: Quiet supersonic planes
Posted by: Will Collier
Date: November 01, 2019 07:36AM
Quote
mrlynn
Thanks Carnos Jax and freeradical, for addressing my question (which was in response to Will Collier's point that, besides sonic boom, SSTs would be too loud at and near airports).

The answer is clearly some kind of hybrid engine(s) that could switch from low-speed high-speed modes. As I recall, a British company was working on a combination turbo-fan and ramjet to address these concerns.

Or an SST could conceivably carry two kinds of engines, which of course would add a lot of weight.

/Mr Lynn

Yeah, I have a hard time imagining that being feasible. But the internal adaptive engine, if the Pratt folks can pull that off it'll really be something.

One thing mentioned up in the thread worth noting, afterburners certainly do make a lot of noise (and use a lot of fuel), but you don't see them used on takeoff in modern fighters any more except in "hey look at this cool thing" at airshows. F-15, F-16 and F/A-18 were basically the last generation for that.
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Re: Quiet supersonic planes
Posted by: MrNoBody
Date: November 01, 2019 08:33AM
Grew up near a NAS, Navy & Marines flew the F-4 Phantom II going out to sea in
practice runs and then back to base later. Back then, doing Mach @ lower altitude
was not the big deal it is now! Flew so low you could count the rivets on the belly.

Sonic Boom is one of those challenges that science will probably solve in the future.
They've developed 'stealth helicopters' and effective sub-sonic sniper rifles (using the
.300 AAC Blackout round). No telling what the brainiacs @ DARPA will come up with next secret smiley



39°36'17"N 75°44'43"W

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Re: Quiet supersonic planes
Posted by: Article Accelerator
Date: November 01, 2019 12:54PM
Quote
JoeH
Actually quite true.

Yep, I read that:

[en.wikipedia.org]
"The Tu-95 is one of the loudest military aircraft, particularly because the tips of the propeller blades move faster than the speed of sound."


Sheesh…
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Re: Quiet supersonic planes
Posted by: Ombligo
Date: November 01, 2019 07:31PM
The Tu-95 had a passenger version, the Tu-114 which was used by Aeroflot. It used the same engines, with the same noise. No noise-canceling headphones either.



“No persons are more frequently wrong, than those who will not admit they are wrong.”
-- François de La Rochefoucauld
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Re: Quiet supersonic planes
Posted by: mrlynn
Date: November 01, 2019 07:49PM
Quote
Ombligo
The Tu-95 had a passenger version, the Tu-114 which was used by Aeroflot. It used the same engines, with the same noise. No noise-canceling headphones either.

Way back in 1968 I flew on an Aeroflot jet (not a prop-jet) from Moscow to Tashkent. It was pretty clearly a converted military plane, and noisy as all get out. Pressurization wasn't great either; they gave us hard candies to suck.

/Mr Lynn
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