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Boom Technology Overture M2.2 SST

Zoo Tycoon

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The problem area is not the first stages of the compressor. You are far from the limits there of the usual metals used (no-one is using aluminum in engine compressors). The normal material used is titanium for the first stages and then Ni alloys, where the creep limit is at 700°C. This is the real limit, this is why you use low compression engines for fast SSTs.

https://leehamnews.com/2018/10/12/bjorns-corner-supersonic-transport-revival-part-10/

Yes the basic problem is creep at elevated temperature.

The Olympus engine started it life, aimed at the subsonic Vulcan, with Al alloy LP blades. When it evolved to the Supersonic (limited duration) TSR2 it adopted steel blades for the LP first stage with LP Titanium blades in the stages behind it, and the first few HP stages, where you are correct the latter stages of which used nickel alloys. There are other reasons for a steel LP first stage if you have Ti behind;- best chop up anything incoming rather than risk it detaching the Ti blades behind and setting the whole lot alight.

When further developed again for Concorde super cruise capability, the engine was “zero staged“ whereby a steel bladed LP fan added at the front. Following a series of Titanium fires within the compressor, the titanium blade stages were progressive swapped to steel, I understand at least for the whole LP, maybe the forward HP stages as well.

The Titanium fires were a result of the extended operating times at high temperature, the blades creep excessively, the tips rub on the casing, and the local friction generates sufficient heat to ignite the Titanium. Not a problem for most supersonic dash applications.Of course the stators remained Ti.

When a titanium compressor fire occurred the results were spectacular;- the engine was quite literally cut in two. To remove it, tubes were welded across the gap to restore the basic integrity such that the could be lifted out.

I was told this problem has been also observed on the very few other engines specifically intended for Super cruise flight, e.g the J58, the but I’ll honest and say I’ve never seen detail of the blade material.
 
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TomS

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sferrin said:
F101 has a 2:1 bypass ratio as I recall, but is out of production, and probably more engine than they need.

Minus the burner, it might not be far off. They're going to have to be able to take off and climb out on partial engine thrust to hit the noise targets, so they might need something that big.

It could actually make sense. The older AvWeek article on Boom said they were looking at two cores -- one military and one civilian, as the possible basis for their new engine. The F101 core evolved into the CFM56, so they might be thinking about reversing that evolution, refanning a modern CFM56 core into a lower-bypass design.

Circling back to this. It seems RR are the powerplant partner so whatever they're using will end up coming out of the RR stable somehow.

I see some articles referring to the Overture engines being in the 15-20k lbf thrust range. That seems low to me; that is similar to the engines like the BR700 family used in long-range bizjets like Global Express or Gulfstream G700. Just adding one more engine in that size range isn't going to get a 45-seat aircraft to Mach 2.2. Or am I being dense?
 
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galgot

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The demonstrator has a quite « reasonable » nose length compare to the Low Boom Flight Demonstration Aircraft or some JAXA sst research concepts. At least it doesn’t look like a Pinocchio .
Was it found these extra long noses concepts not that efficient for sonic boom reduction ?
 

TomS

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The demonstrator has a quite « reasonable » nose length compare to the Low Boom Flight Demonstration Aircraft or some JAXA sst research concepts. At least it doesn’t look like a Pinocchio .
Was it found these extra long noses concepts not that efficient for sonic boom reduction ?

This aircraft isn't trying for boom reduction, so its nose doesn't tell us anything about the effectiveness of boom reduction techniques.

Given that the X-59 is still being built with quite a long nose, NASA and Lockheed still think it's a viable approach.
 
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riggerrob

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... The world will at this time wake up from its Covid-19 lethargy and the public will want to focus on fast, snap of fingers kind of things. We are probably heading toward a new short decade again of the roaring twenties, with attention grabbed by futile things (but is that new?). ...
"

Good point dear Tomcat VIP,
As soon as COVID19 subsides, the rich and powerful have one more excuse to avoid rubbing elbows with the "great un-washed." This time their alibi is avoiding infectious diseases. Video-conferencing is fine for middle managers, but far too vulnerable to "hacking" for the most sensitive negotiations. Powerful people need to be able to discuss a wide variety of "politically incorrect" options before signing contracts. Powerful people still want to meet face-to-face - in privacy - to discuss the most "sensitive issues." They also want to meet a few hours ahead of their competition. Supersonic Business Jets provide those opportunities, but only the wealthiest will be able to afford to travel at SS speeds.
They will stash their SSBBJs in stealthy hangars, at quiet airports like White Plains and only launch after sunset. A variety of electronic "dazzlers" will confuse the cameras of nosey "papparatzi."
 
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TomS

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... The world will at this time wake up from its Covid-19 lethargy and the public will want to focus on fast, snap of fingers kind of things. We are probably heading toward a new short decade again of the roaring twenties, with attention grabbed by futile things (but is that new?). ...
"

Good point dear Tomcat VIP,
As soon as COVID19 subsides, the rich and powerful have one more excuse to avoid rubbing elbows with the "great un-washed." This time their alibi is avoiding infectious diseases. Video-conferencing is fine for middle managers, but far to vulnerable to "hacking" for the most sensitive negotiations. Powerful people need to be able to discuss a wide variety of "politically incorrect" options before signing contracts. Powerful people still want to meet face-to-face - in privacy - to discuss the most "sensitive issues." They also want to meet a few hours ahead of their competition. Supersonic Business Jets provide those opportunities, but only the wealthiest will be able to afford to travel at SS speeds.
They will stash their SSBBJs in stealthy hangars, at quiet airports line White Plains and only launch after sunset. A variety of electronic "dazzlers" will confuse the cameras of nosey "papparatzi."

Overture isn't a bizjet; it's way too big for that. It's more like taking the whole front section of a 777 (10 First class and 40-odd Business class seats) and flying it at Mach 2.

The worrisome thing is what happens to economy if all the business class seats are flying supersonic. Because those business class seats are subsidizing the economy seats. Put those passengers on their own plane and the tickets for the rest of us get way more expensive.
 

merriman

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... The world will at this time wake up from its Covid-19 lethargy and the public will want to focus on fast, snap of fingers kind of things. We are probably heading toward a new short decade again of the roaring twenties, with attention grabbed by futile things (but is that new?). ...
"

Good point dear Tomcat VIP,
As soon as COVID19 subsides, the rich and powerful have one more excuse to avoid rubbing elbows with the "great un-washed." This time their alibi is avoiding infectious diseases. Video-conferencing is fine for middle managers, but far to vulnerable to "hacking" for the most sensitive negotiations. Powerful people need to be able to discuss a wide variety of "politically incorrect" options before signing contracts. Powerful people still want to meet face-to-face - in privacy - to discuss the most "sensitive issues." They also want to meet a few hours ahead of their competition. Supersonic Business Jets provide those opportunities, but only the wealthiest will be able to afford to travel at SS speeds.
They will stash their SSBBJs in stealthy hangars, at quiet airports line White Plains and only launch after sunset. A variety of electronic "dazzlers" will confuse the cameras of nosey "papparatzi."

Wow! And I thought I was a glass-half-full sort of guy. However, I fear riggerrob is more right than wrong. Here comes Illuminati Air, boy's and girls.
 

fredymac

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I thought they were targeting ticket prices in the neighborhood of business class. That said, I can imagine the billionaires who currently buy full size airliners and convert them to private use might switch to a more cramped but supersonic alternative. They trade off a 2nd living room and guest suite for less time in the air. The airport parking apron that services Davos will tell.
 

TomcatViP

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They can also double as corporate airplanes, as Boom's CEO suggested in their presentation, moving teams for face to face meeting and prototypes/products around the world for increased productivity.
 
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NUSNA_Moebius

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sferrin said:
F101 has a 2:1 bypass ratio as I recall, but is out of production, and probably more engine than they need.

Minus the burner, it might not be far off. They're going to have to be able to take off and climb out on partial engine thrust to hit the noise targets, so they might need something that big.

It could actually make sense. The older AvWeek article on Boom said they were looking at two cores -- one military and one civilian, as the possible basis for their new engine. The F101 core evolved into the CFM56, so they might be thinking about reversing that evolution, refanning a modern CFM56 core into a lower-bypass design.

Circling back to this. It seems RR are the powerplant partner so whatever they're using will end up coming out of the RR stable somehow.

I see some articles referring to the Overture engines being in the 15-20k lbf thrust range. That seems low to me; that is similar to the engines like the BR700 family used in long-range bizjets like Global Express or Gulfstream G700. Just adding one more engine in that size range isn't going to get a 45-seat aircraft to Mach 2.2. Or am I being dense?

Sea level static thrust numbers don't paint a full picture. Intake and nozzle matter immensely for supersonic flight. The GE's Affinity is a pretty good example of the kind of direction RR will have to go for Overture. However, Affinity is designed to be efficient for transonic and up through about M1.5 without relying on advanced intake systems as per Aerion's specifications. RR's solution is likely to have less bypass and further intake, fan, and nozzle optimization a la the Olympus.
 

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Sea level static thrust numbers don't paint a full picture. Intake and nozzle matter immensely for supersonic flight. The GE's Affinity is a pretty good example of the kind of direction RR will have to go for Overture. However, Affinity is designed to be efficient for transonic and up through about M1.5 without relying on advanced intake systems as per Aerion's specifications. RR's solution is likely to have less bypass and further intake, fan, and nozzle optimization a la the Olympus.

Thanks. Any guess what the likely core would be? Affinity seems to be a CFM56 core, as far as we know.
 

NUSNA_Moebius

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Sea level static thrust numbers don't paint a full picture. Intake and nozzle matter immensely for supersonic flight. The GE's Affinity is a pretty good example of the kind of direction RR will have to go for Overture. However, Affinity is designed to be efficient for transonic and up through about M1.5 without relying on advanced intake systems as per Aerion's specifications. RR's solution is likely to have less bypass and further intake, fan, and nozzle optimization a la the Olympus.

Thanks. Any guess what the likely core would be? Affinity seems to be a CFM56 core, as far as we know.

It is. It's got the right pressure ratio to be friendly with supersonic speeds. The Leeham article posted earlier goes in depth on the details. Dual broad chord fan rotors and a very optimized mixer and plug nozzle are very key for Affinity.
 

TomS

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Thanks. Any guess what the likely core would be? Affinity seems to be a CFM56 core, as far as we know.

It is. It's got the right pressure ratio to be friendly with supersonic speeds. The Leeham article posted earlier goes in depth on the details. Dual broad chord fan rotors and a very optimized mixer and plug nozzle are very key for Affinity.

I guess my real question for this thread is what is the RR equivalent. Can the BR700 core be tweaked to work or are they going to need something else?
 

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What is going to be the landing speed for it? It looks like it will land pretty fast... I'm talking about the scaled-down prototype? Why slats are such a no-no for high-speed airplanes if I'm not mistaken neither the sr-71, Mig-31, Concorde has slats.
 

NUSNA_Moebius

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What is going to be the landing speed for it? It looks like it will land pretty fast... I'm talking about the scaled-down prototype? Why slats are such a no-no for high-speed airplanes if I'm not mistaken neither the sr-71, Mig-31, Concorde has slats.

Leading edge heating and expansion would be a difficult prospect without a full wing structure and skin to transfer heat into.
 

galgot

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A Concorde B variant was supposed to have some :
baircraft-jpg.6656

2707 too... But then, don't know much about it.
Maybe doing it in composite makes it difficult too ?
 
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TomS

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What is going to be the landing speed for it? It looks like it will land pretty fast... I'm talking about the scaled-down prototype? Why slats are such a no-no for high-speed airplanes if I'm not mistaken neither the sr-71, Mig-31, Concorde has slats.

From their website, they talk about the landing gear ABS brakes being able to safely handle landings with an approach speed of up to 185 knots. So that's the upper bound; I assume actual approach speeds would be lower. Normal airliner speeds are typically around 140-150 knots, to that's not radically different.

The issue is that to get that slow, that will be very nose high on landing. Hence the need for video cameras to see the runway.
 

sferrin

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... The world will at this time wake up from its Covid-19 lethargy and the public will want to focus on fast, snap of fingers kind of things. We are probably heading toward a new short decade again of the roaring twenties, with attention grabbed by futile things (but is that new?). ...
"

Good point dear Tomcat VIP,
As soon as COVID19 subsides, the rich and powerful have one more excuse to avoid rubbing elbows with the "great un-washed." This time their alibi is avoiding infectious diseases. Video-conferencing is fine for middle managers, but far to vulnerable to "hacking" for the most sensitive negotiations. Powerful people need to be able to discuss a wide variety of "politically incorrect" options before signing contracts. Powerful people still want to meet face-to-face - in privacy - to discuss the most "sensitive issues." They also want to meet a few hours ahead of their competition. Supersonic Business Jets provide those opportunities, but only the wealthiest will be able to afford to travel at SS speeds.
They will stash their SSBBJs in stealthy hangars, at quiet airports line White Plains and only launch after sunset. A variety of electronic "dazzlers" will confuse the cameras of nosey "papparatzi."
And they'll be escorted to their planes by Ryan Reynolds.
 

riggerrob

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The issue is that to get that slow, that will be very nose high on landing. Hence the need for video cameras to see the runway.

A simple transition because it is a minor variation on the "synthetic vison" systems already offered on the latest version of Gulfstream biz jets. The latest avionics include "synthetic vision" that combines visual, infrared and artificial images of runways all projected onto a heads up display.
Not is this a new idea. Back in 1993, I worked on a NASA project to test under-nose video cameras to land a two-seater F-104 Starfighter. This was supposed to lead to a simplified forward fuselage for an American SST. By "simplified forward fuselage" I mean none of the downward hinged nose cones as installed in the Concorde or Concordski airliners.
 

riggerrob

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Approach speed is very important for business jets. because the slower the approach speed, the shorter the runways they can use. Energy increases with the square of the velocity, doubling the approach speed quadruples the length of runway needed for braking. Big tires - with fancy anti-lock brakes - are great in theory, but border on useless on wet or icy runways. Thrust reversers can help reduce braking distance, but are not much good at steering the airplane to stay on the runway.
Shorter runways mean a far wider variety of runways, making it ever more difficult for competitors to guess where they will land.
 

TomcatViP

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See how the fuselage is perched on that landing gear: they are going to use a lot of aero braking (safer now with FBW), hence a lot less than 4 time runway length needed (drag has here a square factor vs normal brakes that are only marginally proportional to speed only).

Great anecdote for the 104 ;)
 

TomS

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A simple transition because it is a minor variation on the "synthetic vison" systems already offered on the latest version of Gulfstream biz jets. The latest avionics include "synthetic vision" that combines visual, infrared and artificial images of runways all projected onto a heads up display.
Not is this a new idea. Back in 1993, I worked on a NASA project to test under-nose video cameras to land a two-seater F-104 Starfighter. This was supposed to lead to a simplified forward fuselage for an American SST. By "simplified forward fuselage" I mean none of the downward hinged nose cones as installed in the Concorde or Concordski airliners.

Yep. I'm actually surprised none of the bigger widebodies ever adopted this idea. Seems like it could be useful for them as well.

Approach speed is very important for business jets. because the slower the approach speed, the shorter the runways they can use. Energy increases with the square of the velocity, doubling the approach speed quadruples the length of runway needed for braking. Big tires - with fancy anti-lock brakes - are great in theory, but border on useless on wet or icy runways. Thrust reversers can help reduce braking distance, but are not much good at steering the airplane to stay on the runway.
Shorter runways mean a far wider variety of runways, making it ever more difficult for competitors to guess where they will land.

Very true. But Overture isn't meant as a business jet. It's meant for scheduled airliner service between relatively major airports. At 170,000+ pounds, it's too big for reliever airports where a lot of biz-jets operate. If it's flying to New York City, for example, it's not going into Teterboro, it's going to JFK. And because it's only supersonic over water, it's pretty much exclusively for international flights. There aren't many (any?) plausible segments inside the US that are dense enough to support multiple all-business flights per day, flown overwater, and long enough to really benefit from supersonic speeds.
 

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Is the demonstrator designed XB because it’s not a government X plane?
 

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I am not aware of any government regulation restricting the use of the "X" designation. "XB" probably just sounded cool to the company boss.
 

TomS

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Is the demonstrator designed XB because it’s not a government X plane?

There are no rules for private aircraft designations. It's called XB-1 because that's what the company wanted to call it, and thought would be useful for marketing. Presumably "XB" is short for "Boom Experimental" but they didn't have to call it that.
 

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A Concorde B variant was supposed to have some :
baircraft-jpg.6656

2707 too... But then, don't know much about it.
Maybe doing it in composite makes it difficult too ?
why Concorde B needs such a devices? to reduce approach speed? to enhance L/D in subsonic area?

is there any sources to propose the idea?
 

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riggerrob

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Consider how little of earth's dry surface is inhabited. Vast areas of Northern Canada, Siberia, Central Asian "Stans," Western China, North Africa, Himalayas, Australia and all of Antarctica are very thinly populated. SSTs still want to fly supersonic over those regions to shorten Great Circle Routes.
When I worked at CFS Alert, we routinely saw sub-sonic airliners cruising over-head, but rarely heard them. Propigation of sonic booms is far more complicated than civilians have been told. For example, when Concordes flew into New York, some detractors - living well up the coast - claimed that they could hear booms reverberating between different layers of clouds/weather fronts.
OTOH some of those NIMBY complaints were totally bogus because they phoned in every time a Concorde was scheduled to land at JFK ... even when it was grounded in Europe by weather or repairs.
Hah!
Hah!
 

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SSTs could save heads of state and business leaders hundreds of thousands of dollars per year in security costs. The less time they spend outside of guarded compounds, the fewer roving agents they need. This is also where ability to land on a wide variety of short runways helps, allowing them to land closer to destinations - reducing ground travel time - and leaving terrorists guessing at when or where they will arrive.
Currently, security teams often send out "spoofer" security agents to alternate airfields to distract assassins. By the time bad guys have determined where the executive landed, he/she is already ensconced in a well-guarded hotel.
 

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Too much Martini can kill too. Less time spent in the air with the press watching you is more time in the privacy of a comfy hotel suite. We haven't yet invented sober politicians :rolleyes:
 

TomS

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SSTs could save heads of state and business leaders hundreds of thousands of dollars per year in security costs. The less time they spend outside of guarded compounds, the fewer roving agents they need. This is also where ability to land on a wide variety of short runways helps, allowing them to land closer to destinations - reducing ground travel time - and leaving terrorists guessing at when or where they will arrive.
Currently, security teams often send out "spoofer" security agents to alternate airfields to distract assassins. By the time bad guys have determined where the executive landed, he/she is already ensconced in a well-guarded hotel.

Not sure how it saves on these expenses at all. Time spent on the ground is driven by the trip agenda -- how many people are there to see, how long are the events, etc. Getting there faster won't change that calculation at all.
 

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sferrin said:
F101 has a 2:1 bypass ratio as I recall, but is out of production, and probably more engine than they need.

Minus the burner, it might not be far off. They're going to have to be able to take off and climb out on partial engine thrust to hit the noise targets, so they might need something that big.

It could actually make sense. The older AvWeek article on Boom said they were looking at two cores -- one military and one civilian, as the possible basis for their new engine. The F101 core evolved into the CFM56, so they might be thinking about reversing that evolution, refanning a modern CFM56 core into a lower-bypass design.

Circling back to this. It seems RR are the powerplant partner so whatever they're using will end up coming out of the RR stable somehow.

I see some articles referring to the Overture engines being in the 15-20k lbf thrust range. That seems low to me; that is similar to the engines like the BR700 family used in long-range bizjets like Global Express or Gulfstream G700. Just adding one more engine in that size range isn't going to get a 45-seat aircraft to Mach 2.2. Or am I being dense?
An engine for Mach 2.2 is a very different engine to one for M0.9 (bizjet engine). To fly at M2.2 you need an engine with a very high specific thrust (extremely low bypass ratio). In fact, the only way to get your takeoff noise (which requires a low specific thrust = high bypass ratio) and an engine that works at M2.2 cruise is to make a variable cycle (= variable bypass ratio) engine. It will be the first for a commercial airliner, in fact, the first in operational use in the world as the military variable by-pass ratio engines from GE and PW are in a research stage right now. But given the solid funding and technology basis of the Boom project, it will of course be achieved. RR as a technology partner has the spare cash to fund it as well.
 

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https://paxex.aero/2020/07/boom-supersonic-rolls-royce-engine-partnership/

It is not a new technology engine, it is a new design engine. You’ve got knobs on an engine like bypass ratio and pressure ratio and they’re set in certain places for the 787 and you want to set them in different places for this airplane. It is moving the knobs, it is not let’s invent variable cycle or something that’s never been certified before.

Now, it's possible as the article says, that this will turn out to be impossible. But for right now, Boom definitely seems the possibility of something a lot less demanding that a new core and a variable cycle engine. A lot can be done with inlet and nacelle design, especially since they are really only trying to optimize for a single point performance, unlike the multiple points where military engines are trying to work. Having lots of excess thrust so they can take off at partial power seems like a simpler, if less efficient, solution.
 

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https://paxex.aero/2020/07/boom-supersonic-rolls-royce-engine-partnership/

It is not a new technology engine, it is a new design engine. You’ve got knobs on an engine like bypass ratio and pressure ratio and they’re set in certain places for the 787 and you want to set them in different places for this airplane. It is moving the knobs, it is not let’s invent variable cycle or something that’s never been certified before.

Now, it's possible as the article says, that this will turn out to be impossible. But for right now, Boom definitely seems the possibility of something a lot less demanding that a new core and a variable cycle engine. A lot can be done with inlet and nacelle design, especially since they are really only trying to optimize for a single point performance, unlike the multiple points where military engines are trying to work. Having lots of excess thrust so they can take off at partial power seems like a simpler, if less efficient, solution.
The engine that does this (except using a fixed inlet instead of a multi-chock inlet) is the GE Affinity. It flies between M0 and 1.4. The problem for the Boom project is its leaders who didn't know better put the bar at 10% faster than the Concorde, that had the luxury of a straight jet (and the consequential take-off noise). You can't handle the Ram drag at M2 unless you can limit the amount of air mass that enters the engine. It's physics, every engine designer knows about it. This is why the Tu-144 changed from a bypass engine to a straight jet during its development.

The engine is the key problem for an SST, especially if you want to go above M1.6. This is where fixed inlets don't work anymore and you have a real problem with normal cores, let alone a non-military low-pressure system. Boom has been at it for four years now and has made progress on every other account. On the engine side, they are still "studying possible solutions, and if an existing core can be used". The reason is what every serious engine designer knows, you can't solve it with a fixed design. Not today with the noise standard we have.
 
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riggerrob

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If Boom Technologies are smart, they are developing bleed air systems to divert ram air away from the compressor face.
Perhaps Boom had internal doors that they are afraid to reveal to competitors.
The second generation of Boom will probably have electro-magnetic, plasma systems to steer air away from the compressor face.
 
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