Is this an April fool's joke that just got published late?

The physics of the "sonic boom" are the same as they ever were!

If people don't want to hear the "boom" then the aircraft will have to be flying sub-sonic!

So, irrespective of it's overall capabilities, if it can't operate profitably at sub-sonic speeds it probably wont operate at all ;)

21 minutes ago, chris_eve said:

Is this an April fool's joke that just got published late?

The physics of the "sonic boom" are the same as they ever were!

If people don't want to hear the "boom" then the aircraft will have to be flying sub-sonic!

So, irrespective of it's overall capabilities, if it can't operate profitably at sub-sonic speeds it probably wont operate at all 😉

 

Huh... its about reducing the sonic boom to a thud. This is NASA that are working on this, and others. The careful shaping of the airframe can indeed reduce the sonic boom to a level that's not a nuisance. 

2 hours ago, Ray Proudfoot said:

@martin-w, so its cruise speed is now just Mach 1.4. That’s 400mph slower than Concorde. 😳 940mph versus 1320-1350mph. Concorde was 44% faster.

 

Boom will fly at Mach 1.7. Its the NASA test vehicle that's Mach 1.4. 

 

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The lack of forward visibility could be its biggest issue. I remember in the early days of Concorde’s design the cockpit forward windows were very small and the US FAA said it wouldn’t be approved unless they were enlarged. Might this be the Achilles’ Heel of Boom? What happens should there be a full electrical failure?

 

Cameras, enhanced vison system. Pretty sure they will be smart enough to have backup systems.

 

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Concorde employed ramps to slow the air into the engines once supersonic. I see no equivalent for Boom. But that’s necessary to avoid engine flameout. They still have major hurdles to overcome before this is viable.

 

 

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Engines[edit]

Boom wants to use moderate-bypass turbofans without afterburners, unlike Concorde's Rolls-Royce/Snecma Olympus. The only available choices are jet fighter engines, which have neither the fuel economy nor the reliability required for commercial aviation. As of November 2016, no engine manufacturer could develop such an engine based on sales of only 10 units. Boom needs to deal with the noise of the high jet speed engine, and the tripled fuel consumption per unit distance and per seat compared with a modern wide-body aircraft.^[26] The International Council on Clean Transportation estimated that a supersonic aircraft would burn at least three times as much fuel per business-class passenger as a subsonic aircraft.^[29]

The engine is intended to be a modified version of the existing turbofan engine design, although it will come with higher maintenance costs.^[5] It was to be selected in 2018, being either a derivative of a commercial engine or a clean-sheet design. It was unlikely a military engine, due to export controls.^[7] The 55-seat airliner will be powered by three 15,000–20,000 lbf (67–89 kN) engines without afterburners, with shorter maintenance intervals than subsonic jets.^[12] A development of an existing commercial engine core, with a new low-pressure spool, is preferred over a clean-sheet design. Larger-diameter fans have higher cruise thrust requirements for a higher fuel-burn and lower range, but are preferred due to their higher bypass and lower take-off noise.^[28]

Intake compression would need a low-pressure core, and derivatives of existing 3–4:1 bypass-ratio turbofans are a compromise between takeoff noise and wave drag, with a good fuel efficiency. Dave Richardson, of Lockheed Martin's Skunk Works, noted that suitable engines with low overall pressure ratio are scarce. Development of 1950s–1960s engines like the GE J79, GE YJ93, GE4, PW J58 or Rolls-Royce Olympus ended when more efficiencies were pursued, and subsequent advances in materials science for much hotter cores are not optimized for long supersonic endurance. The PW JT8D or GE J79 are better suited than current engines, and staggering development costs render new low-bypass-ratio turbofans unlikely.^[30]

In July 2020, the company announced that it had entered into an agreement with Rolls-Royce to collaborate on engine development.^[31]

 

 

Does anyone remember hearing the sonic boom when the Apollo and Space Shuttle vehicles broke the sound barrier around 30 seconds after launch?

No me. All you have to do is increase the engine noise to drown it out! 😁

Test vehicle though, wont be the same engines in the passenger version. 

 

The Boom Supersonic XB-1 engines are installed and running. The company released an update on the flight test program progress, including details on the installation and first test runs of the three General Electric J85 engines on board.

 

https://boomsupersonic.com/flyby/post/start-your-engines

 

 

 

 

 

 

Edited April 24, 20224 yr by martin-w

Martin, I’ve read that blurb twice now and nowhere do I see anything about reducing the speed of the air before it enters the engine intakes. Can fans really cope with air travelling at supersonic speeds?

1 hour ago, martin-w said:

its about reducing the sonic boom to a thud. This is NASA that are working on this, and others. The careful shaping of the airframe can indeed reduce the sonic boom to a level that's not a nuisance. 

And how do they do that? Given the brilliance of the Concorde engineers they must have investigated that and decided it wasn’t possible. Details, it’s all in the details and they seem reluctant to show how that can be achieved. I remain highly sceptical.

2 hours ago, Ray Proudfoot said:

Given the brilliance of the Concorde engineers they must have investigated that and decided it wasn’t possible. Details, it’s all in the details and they seem reluctant to show how that can be achieved. I remain highly sceptical.

You have to bear in mind that back when Concorde was built, there wasn't really any information concerning how a sonic boom might impact on an airliner's commercial viability in terms of being allowed to fly over places where it might cause a noise which people would find cause to complain about, particularly if it cracks windows. So they probably didn't consider the importance reducing its sound signature as a massively important priority.

With hindsight we know this was, and will, be an issue, particularly in these days of snowflakey PC-ness, so there is certainly more motivation to tackle the issue and try to mitigate it than there was in 1969, and there is the technology to do it too. We know this is true of subsonic airliners as well; you used to have airports operating 24/7 with turbojet engines roaring about all over the place; nowadays there are all sorts of noise abatement rules concerning this which limits the times airports can let stuff operate. But if you look at most modern airliners, they have a saw-tooth edge on the engine cowlings to reduce the sound signature, and turbofans are usually quieter too; you don't find anything like that on the earlier generations of airliners.

A sonic boom is a sonic boom of course, caused by the rapid acceleration of air movement similar to a thunderclap. You can't change the laws of physics and stop that being a phenomenon, but you can work with its known causes to mitigate it. With this in mind, there has been considerable research into doing so, for example with NASA/Gulfstream's Quiet Spike test programme, whereby a telescoping boom spike fitted on the nose of an F-15B eases the transition of still air into its acceleration to supersonic speed as the aeroplane penetrates the air mass. This considerably reduces the crack of the sonic boom which the aeroplane produces. Mostly the boom sound is caused by the nosecone and the leading edges of the wings, so how much can be done to alleviate the wings from producing a sound is open to question, but nothing is really impossible to achieve, merely expensive, difficult and not always practical and the fact that they have called the new airliner BOOM tends to indicate they're conceding that it will at least make a bit of a noise. Ultimately though, since high speed air travel is usually the preserve of the rich, who tend to have influence, one suspects this will mean it goes ahead.

Personally, I think they should blame it all on Sonic the Hedgehog. With a name like that, he's the perfect scapegoat.

Edited April 24, 20224 yr by Chock

@Chock, the telescopic boom might help an F-15 but this is a much larger aircraft and the delta wing still has a large leading edge.

I vaguely remember fan blades were considered for the Olympus 593 but it wasn’t possible. Can fans really slow the air to 500mph? The ramps on Concorde did. 1300mph to 500mph in 11 feet. Boom needs to do the same otherwise it could cause engine flameout.

How this develops will be interesting especially when the full-size aircraft is built.

NASA also had a successful test program using a modified F-5E that showed it was possible to modify the sonic boom created.

https://www.nasa.gov/aero/sonic_boom_takes_shape.html

There has also been plenty of research into engine inlet designs for supersonic aircraft as well.

https://www1.grc.nasa.gov/research-and-engineering/inlet-and-nozzle/inlet-technology/

https://www.thedrive.com/the-war-zone/20881/the-yf-23s-air-inlet-design-was-its-most-exotic-feature-you-never-heard-of

While the Concord was impressive, it would be a mistake to assume that we haven't learned a great deal since then.

4 hours ago, Ray Proudfoot said:

And how do they do that? Given the brilliance of the Concorde engineers they must have investigated that and decided it wasn’t possible. Details, it’s all in the details and they seem reluctant to show how that can be achieved. I remain highly sceptical.

 

Ray, you do realise that its NASA that are trying to reduce the sonic boom to a thud. Nothing to do with the Boom supersonic passenger jet. As far as I know, Boom aren't doing anything in that respect. If you realise its NASA trying to achieve this, then perhaps, not satisfied with pretending to land on the Moon, they are now fooling us into thinking they can mitigate a sonic boom. 😁

 

4 hours ago, Ray Proudfoot said:

Martin, I’ve read that blurb twice now and nowhere do I see anything about reducing the speed of the air before it enters the engine intakes.

 

Rolls Royce are designing the engine for the Boom full scale passenger jet. You would need to ask them for details but given its in development and new tech, I doubt they would want to tell you. What I posted, as I said, was for the smaller scale demonstrator. 

1 minute ago, martin-w said:

Ray, you do realise that its NASA that are trying to reduce the sonic boom to a thud. Nothing to do with the Boom supersonic passenger jet.

The two being mentioned in the same article clouded things.

And as I said earlier let’s see how the full-scale aircraft pans out with this technology fitted. Still a lot of issues to overcome.

It might also help to read the Boom FAQ.

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How is Boom dealing with the sonic boom?

Overture will fly at subsonic speeds over land and near coasts, so people on the ground will not be exposed to sonic booms.

Over the ocean, Overture will cruise at supersonic speeds, cutting many flight times in half. Passengers won’t notice when the airplane breaks the sound barrier, which will be inaudible and uneventful.

https://boomsupersonic.com/contact#faq-section

30 minutes ago, Ray Proudfoot said:

the telescopic boom might help an F-15 but this is a much larger aircraft and the delta wing still has a large leading edge.

 

Mounting engines on top of wings, better aircraft bodes and wings designed by computational fluid dynamics, supersonic aerofoil's constructed to induce passive laminar flow, reducing or eliminating the turbulent crossflow on wings that produces shockwaves. All manner of techniques can help.

https://www.machinedesign.com/markets/defense/article/21834005/supersonic-flight-overcoming-the-sonic-boom

 

 

9 minutes ago, martin-w said:

Mounting engines on top of wings, better aircraft bodes and wings designed by computational fluid dynamics, supersonic aerofoil's constructed to induce passive laminar flow, reducing or eliminating the turbulent crossflow on wings that produces shockwaves. All manner of techniques can help.

https://www.machinedesign.com/markets/defense/article/21834005/supersonic-flight-overcoming-the-sonic-boom

I didn’t understand a word of that. I’m out.

You don't need to understand Ray. Just know that there are people that do, at NASA.