What engine will power the next commercial supersonic jetliner? For Boom Supersonic it is all about finding the right core. CEO Blake Scholl spoke recently at the joint Wings Club/IATA Aviation Day USA event, sharing his vision for the return of supersonic commercial flight. But the big question – what engine will power the 55 seat, Mach 2.2 jet – was not touched in the presentation. After his time on stage Scholl acknowledged that the power plant remains a significant open item but also believes it is a relatively easy challenge to address.
Scholl expects to make a down-select on Boom airliner engine choice next year, choice between "derivative" of civil engine, or "clean-sheet design" #avgeek #DAS17
— Tim Robinson (@RAeSTimR) November 13, 2017
Three engine vendors are currently participating in process to potentially deliver Boom’s new power plant. Scholl didn’t specifically name them but w can assume that Rolls Royce, Pratt & Whitney and GE are the companies he’s talking about. He also emphasized that the “core” of the engine ultimately selected will almost certainly be from an existing, in service commercial engine, “[T]here are multiple existing cores we can reuse.” That’s a massive savings in development costs and time as well as certification effort.
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.
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Using an existing core helps ease the process, but that doesn’t mean it is easy. One need only look at the ongoing challenges with the A320neo engines to recognize that these newer designs, while more efficient and more powerful and quieter and otherwise amazing are also more complex systems than ever. Delivering the rock-solid, reliable product demanded of commercial air transport is not a trivial task and even just minor “tuning the knobs” of these designs can bring about significant challenges. Given Boom’s stated plans of a certified aircraft operating in commercial service by 2023 any challenges are risky, but especially engine challenges.
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Boeing is familiar with those challenges as well. With a stated goal of the 2025 timeframe for entry-in-service of the still-theoretical NMA aircraft Boeing also faces doubts from its potential airline customers about meeting that target. While delivering the new fuselage and wing should be relatively easy for the company – even with the ovoid body shape – the power plant is also a challenge for the NMA. Flight Global notes that those vendors are quiet about their possible participation in the Boeing project as well.
CFM International, Pratt and Whitney (P&W) and Rolls-Royce are all competing to supply engines to the NMA. CFM has not provided details of its proposed architecture, P&W plans a scaled up version of its geared turbofan (GTF) and Rolls-Royce the so-called UltraFan with a reduction gear. …
All three engine manufactuers are tight lipped about the status of their NMA engines that, coupled with some of the delays meeting deadlines for current aircraft programmes, raise questions about their ability to deliver on time for the proposed Boeing widebody.
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Scholl also addressed the range challenges the current design faces. Capped at 4,500 nautical miles most transpacific routes require a refueling stop somewhere along the way. His travel time estimates – 5.5 hours between San Francisco and Tokyo, for example – account for those stops and he’s already talking up possible locations to meet those needs.
It is not like you go to the gate and get off and back on or change planes. You land, the fuel truck comes, you taxi to the other end of the runway. It is like a pit stop.
Anchorage is a well suited waypoint for Tokyo or Seoul. It even covers Beijing, Shanghai and Taipei well enough. Hong Kong is a stretch too far, however. Anchorage is also very familiar with the “gas-and-go” business; the airport long served both passenger and cargo flights in that role. It will remain to be seen if US immigration policy can be adjusted to allow for the passengers to remain on board rather than clear at Anchorage as their point of entry to the US, though that’s a very small issue many years away still.
In the South Pacific Tahiti is well positioned to connect traffic between the US mainland and Australia. Honolulu offers a smaller diversion distance but sits on the edge of allowable range to Sydney and too far from Melbourne to work for the design spec.
Would you rather have an 11 hour flight to Tokyo that doesn’t refuel or 5.5 hours with a bump in the middle? I think a lot of passengers will choose the latter which is we we talk about doing those routes.
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Ted Shevlin says
Skeptical, but please let it be so. My cousins’ house is right under the curved departure path of JFK’s 31L in the Rockaways, and growing up, I saw and heard so many Concordes departing that airport. You could always tell when it was a Concorde and not a regular plane overhead.
I spent my whole childhood wanting to fly that thing and unfortunately became a frequent flier two years after its retirement. Total bucket list item to reach Mach 2.
Seth Miller says
I’m 100% with you, Ted. Every time I go into one of these conversations with Blake Scholl (the CEO) I express professional skepticism and personal fan-boy like hope that it’ll happen.
But the professional in me looks at the engine issues here and says, “How are they really going to get something designed and built and in production fast enough to meet this incredibly aggressive timeline?” Especially when the market appears so small.
Ted Shevlin says
Agreed on all points. I work in software — same kind of situation: a retrofit of that complexity can be done, but that timeline sounds way too aggressive. (And if they did get it done in time, I almost wouldn’t want to be among the first flying it!)
Well, from one fanboy to another, let’s hope he succeeds *at some point*.
Bernie Leighton says
The worst part of the nostalgia about the sound is half the reason the Concorde was so loud was the afterburning Olympus 593. Boom wants to use some sort of medium bypass engine with no afterburner. I can get them a bunch of D-30s if they want medium bypass and no afterburner. Every other engine I can think of that ascribes to such a ratio is relatively low thrust. Having said that, a telephone style ringing over a high-pitched whine would be a memorable noise out of JFK!
Matt Doernhoefer says
So Boom has a problem. They’re going to need a custom engine job no matter how they look at it. The High and Ultra-high bypass turbofans that GE, CFM, P&W et al are putting out are not usable for supersonic flight. Boom itself came out and said they’re going to need a medium-bypass or even a variable cycle engine (https://blog.boomsupersonic.com/why-we-dont-need-an-afterburner-a4e05943b101). Best case scenario, they can re-purpose the F-135 or F-136 engine from the F-35 program. Ideally, they want something that can super-cruise for both fuel efficiency and execution purposes and hit M2.2. They might be better served with a variable ramjet along the lines of the old J-58 Blackbird engines but that brings with the need for JP-7 fuel instead of Jet-A (JP-5). The J-58 was designed in the 60’s, so I imagine we could come up with something more clever these days. It would be a good start for a clean-sheet core design.
Seth Miller says
But they’ve also explicitly said they don’t want afterburner (too much noise/fuel burn for too little extra speed) and that getting a military model converted to civilian is a logistical problem they don’t want to cross. Scholl’s comments to me about “turning knobs” to tune the settings on the engine came across as someone trying to oversimplify the challenges faced in a way that would be easy to explain but also not necessarily be easy to implement. I think I made that connection in the piece but I’ll accept criticism if I missed there.
I’ll keep asking them these questions the couple times a year I have the opportunity. Eventually either they’re going to announce a vendor and we’ll get to dig deeper on that front or they’ll miss a milestone and some of the shine will start to come off. But all the true aerospace reporters I know are asking the same questions and shaking their heads at the same non-answers. In the meantime he keep raking in publicity appearances and selling the sexy dream of supersonic.
Matt Doernhoefer says
The J-58 hasn’t been used in well over 20 years and hasn’t been built since the original set, I can’t imagine it’s still a classified design. Also, the design was made with slide rules… I think we can do better these days. The Blackbird was stupid efficient when it got up to speed, hooray ramjets. If they could find a way to fix the fuel problem, make the fuselage not leak before takeoff and need 2x v8 engines as blowers to start, it’d be the go-to engine for something like this.
Bernie Leighton says
I still haven’t seen any good whitepapers that are totally UNCLASS, and thus accessible to a schlub like me, that lower the transition speed enough to something Boom could obtain without afterburners.
Bernie Leighton says
I’m still at a loss as to what ITARS compliant engine they can use to provide enough specific impulse to accelerate the aircraft to supercruise. On top of that, the J-58 used afterburners to get up to speed as the optimal transition speed was roughly Mach 2.0. Boom has a, reasonably heavy, aircraft and a refusal to use afterburners. I can’t see how you can get a partial ramjet to transition at a lower speed without it being considerably less efficient during the transition. I’ve said it before and I’ve said it again, if you want an engine with no ITARS risk (which a J-58 derivative would still have because declassification is glacial) the only choice is a couple of Saturn ALF-31F. Yes they have afterburners – but so do F-135s. F-135s more so because of all the extra crap they need built into even non B-model engines. The problem that I see Boom having is that you need something that can get you up to around Mach 2.0 without afterburner if you go with a hybrid ramjet engine before it becomes efficient. We have yet to see any engine provide the necessary specific impulse – even for fighter jets. Look at the speeds modern fifth-generation aircraft supercruise at. The shine’s gonna rub off hard.
Michael J. Graven says
This is so nerd I love it
Dwight Looi says
The problem with the Concord was three fold. #1 it was banned from flying transcontinental routes over land. #2 It burns 6.5 times the amount of fuel per economy class seat compared to the Boeing 787. #3 It does not actually have the range to ANY major transoceanic routes except NY Paris and NY London.
Any one of these would have been OK. Any two might have been survivable. But all three doomed the Concorde as a commercial product. We can expect fuel burn per equivalent seat to drop to 3~4 times that of today’s state of the art big fan wide bodies. That solves one of the three problems, leaving two which makes it perhaps a survivable product, but it won’t be a hit unless they can knock over one more hurdle.
6,000 nm really is the magic number. Any more really is a waste. 6,000 nm will cover LAX to Tokyo, Beijing, Shanghai, Seoul and Taipei. It is also enough for any major city on the eastern US seaboard to any European destination. Even though aircraft like the 787 and A350 allows airlines to connect cities like LA and Singapore, this kind of route is rare and accounts from less than 20% of the market.