Listen in as three Aviation Week editors discuss—and sometimes debate—whether Boom’s new supersonic engine plan is for real.

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Joe Anselmo:

Welcome to our final Check 6 Podcast for 2022. I'm Joe Anselmo, Aviation Week's Editorial Director and Editor-in-Chief of Aviation Week magazine.

After failing to strike a deal with an established aircraft engine manufacturer, supersonic airliner developer Boom has formed an industry team to develop and support a propulsion system for its Mach 1.7 transport. Boom's unconventional approach is a new way of doing business, but can it succeed?

Joining us today are three of our editors. Guy Norris, has led Aviation Week's coverage of Boom and just talked with founder Blake Scholl about the company's new engine development plan. Defense Editor Steve Trimble is Aviation Week's resident skeptic on Boom and just flew supersonic himself on a military aircraft. And Graham Warwick, our Executive Editor for Technology, has covered aircraft and engine developments for more than four decades.

Guy, let's start with you. How do you develop an aircraft engine without an engine OEM?

Guy Norris:

Well, I've got to be honest with you, frankly, when Blake told me what the team was, I was disappointed to know that there wasn't going to be sort of a secret core in there that we hadn't heard about from an established manufacturer. So yeah, I just wanted to kick it off by saying that I am somewhat skeptical myself in some regards in the way that we're approaching this.

But, before I steal Steve's thunder, because I know he's really skeptical, I want to say that having listened to Blake and gone through the plan as we know it today, I can see how we might be looking at literally a paradigm shift in propulsion. And it's not just for supersonic either, I think that's the important thing we have to start off by saying here. We're looking at disruption across the industry. We've seen it in space travel, we've seen it in the development of launch vehicles and rockets, possibly the hardest thing to change in the business. And now we're looking at the beginning of a similar disruption in everything from regional aircraft to air taxis. In other words, why not propulsion as well? Isn't it maybe time that we could see disruption? So that's where I'm seeing things happening.

Joe Anselmo:

Guy, before we go to Steve, could you set the table for our listeners, tell us exactly what Boom's plan is?

Guy Norris:

So Boom, basically, as you rightly say, they did hope to initially team with one of the big three. That didn't work out. So what they've done is they've sort of brought together this team, which includes design group, Florida Turbine Technologies, part of Kratos Defense & Security Solutions. Part of the thing there is that that's an in-house group of people who've come from Pratt & Whitney's combat engine world. So they have this sort of brain trust really of how to get up to Mach 1-plus straightaway from that perspective.

Production, or at least manufacturing, they've got GE Additive. The additive aspect of GE is incredible because they've basically been the first to certify additive parts for jet engines and it's a crucial part of their teaming plan. And then the third leg of the stool really is StandardAero, an established MRO specialist. Obviously one of their key programs that they work with is supporting the GE F110 combat engine, which, of course, is a supersonic-capable fighter engine. So they've kind of decided that they're going to aggregate this team and that the sum is going to be sort of the greater than the sum of the parts kind of approach.

Joe Anselmo:

Steve Trimble, the floor is yours. Why are you so skeptical of this plan?

Steve Trimble:

Well, thank you, and thank you for referring to the fact that I flew supersonic in a Gripen fighter over the Baltic Sea about three weeks ago. That was a very important moment for me and I'm glad that we're all acknowledging it here.

But on the topic of Florida Turbine Technologies and their role in this, I want to be very clear that I actually have a lot of respect for Florida Turbine Technologies. I think they're a really good company and what they're doing, the Air Force Research Laboratory is working with them on a lot of different things. And if you want a turbofan in the 600-900 pound thrust class, they're working on something that is going to be state of the art, if it works, right? If you want something, a small turbo jet for a cruise missile or a target drone in the 200-400 pound thrust class, definitely Florida Turbine Technologies is the company you want to be talking to.

So I don't think I'm going out criticizing Florida Turbine Technologies in any way when I just say or just point out that this is a huge leap for a company like this to go from where they are today to designing a super cruising turbofan engine in the 35,000-pound thrust class. There's only a few companies in the world that have done anything like that. And it's one thing for them to be the designers of this thing. And I guess GE Additive is supposed to build it. Well, not every part of an engine is going to be additively manufactured. Substantial parts of it are. So where's the rest of it going to be built? Are they 3D printing this entire super cruising 35,000 pound thrust turbofan?

And then you go back to the beginning of the program, right? Boom got started in 2014, we started covering them and they had their sort of public launch in 2016. That's when they were talking about building a 40-seat airliner. Now it's 80 seats. They were talking about a Mach 2.2 aircraft with CFRP type composites. Now it's Mach 1.7. They were talking about getting into service by 2023. Now it's by the end of this decade. They were talking about doing a demonstrator, the XB-1 "Baby Boom" Mach 2.2 demonstrator and having that fly by 2017. It's 2023, it hasn't flown, nor based on their series of redesigns, is it clear that even if they did fly, that any of the data they got would be stuff that they could extrapolate to a supersonic airliner except for the fact that it's a supersonic jet.

This is hard, and I don't begrudge small companies and startup companies trying to get into this business and trying to say that we're going to do it differently and we're going to try to make it work. And there have been companies that have done that. SpaceX is a perfect example of that. They spent six years really struggling before they finally were able to get a successful test with the Falcon 1 in 2008, and then they just have gone gangbusters since then.

So it's not impossible, but we're long past that period in the program's life for Boom. And instead of things getting easier, it just seems like things are getting a lot harder for them.

The original plan for the engine was a medium or low bypass ratio derivative of an existing turbofan engine. They worked with Rolls-Royce for several years about converting the Trent 1000 into something that could work for their application. That's an already certified engine. Obviously they'd have to re-certify for this application and the changes they were going to make. But that's a whole lot easier to take something that's off the shelf, that's very well known, has a huge existing install base and parts system and you have a company with a ton of infrastructure to kind of do those tests and do those certification campaigns and all that.

That was the original idea. So not only has the aircraft gotten bigger and far more advanced with this gull wing and area rule fuselage, instead of having a two engine as it was first introduced, and then it became a three engine, now it's a four engine, is starting to stretch the bounds of a plausibility. I mean, just in the sense that I have serious questions about how they pull this off right now, especially after hearing the engine announcement from last week.

Joe Anselmo:

Graham Warwick, we would like to bring you into the conversation. Is what Boom is doing a revolutionary approach a la SpaceX, or is it ‘stretching the bounds of plausibility’ as Steve just said?

Graham Warwick:

Okay, one, they didn't want to do this, right? They wanted to go with an established OEM and they couldn't. So this is a plan B. Two, ignore all timescales given to you by a startup. No startup meets its timescales. And if you actually look at everything that Boom has said, they haven't actually failed, they just haven't got to the milestones, right? It's just stretched.

Three, XB-1 is not, "Baby Boom" is not about technology for the actual aircraft. It is proving the design team can develop an airplane. And that's entirely what that's about. That is for the investors, it's not for the world. It's just approved to the investors, current and future, that they have the wherewithal to develop an aircraft with some relevance to the market.

Third, the engine. So, yes, it's almost unimaginable that somebody could come out of nowhere and develop a certified civil turbofan engine. But if you wanted to develop a certified civil turbofan engine, what better place to start than a single manufacturer, a single aircraft type, a single mission profile? Which means that you can design almost the simplest engine in existence, which is a supersonic engine. There's really very little complexity in a supersonic engine. It's all about managing the thermal environment inside the engine. It's a very simple mechanical design. The complexity's in the inlet and in the nozzle. It's not in the core of the engine. That's about managing the heat.

So, if you are the owner of the aircraft design, the owner of the engine design, it's a single type of aircraft and a single mission profile, that is way simpler than trying to do what GE, CFM, Pratt, Rolls do, which is come up with an engine that will go over multiple different mission profiles from multiple different OEMs on multiple different aircraft types. It's not easy.

But if you're going to start somewhere, this is the simplest way to start. This is a very simple engine, no active cooling, probably no variable geometry of any type in it. It's just a straight pipe that turns fuel into thrust. Now they've got to certify it and that's going to be a huge undertaking.

Where I get skeptical is not the timeframe, it's not the fact it's a startup, it's not the fact that they have to go develop an engine. It is they have to pay to develop the aircraft and the engine, which they already were going to do anyway. Even if they'd gone with an OEM, no OEM was going to pay to develop this engine. They would've had to pay the OEM to develop the engine. They've got to go find $X billion to develop and certify an airplane and an engine.

Then they have got to have a market big enough to recover their investment. I do not believe Boom's business plan -- I believe they can develop an airplane. I believe they can develop an engine -- I do not think that they can find enough supersonic city pairs around the world, viable supersonic city pairs around the world, to build a market for enough airplane to ever recover their investment.

Guy Norris:

Yeah, I was just going to say, I think that one of the key aspects about the Boom story here, and you're right, this is plan B for them, which they've kind of acknowledged really, is the fact that their operating model for this engine is so different to anything that we've seen before. And part of that is obviously related to the fact that this is aimed at the supersonic market where the airplane is flying at Mach 1.7 for several hours rather than the design point being the higher thrust at takeoff or even top of climb.

In other words, they have to design this engine and operate it differently as part of this new approach to the plan. And what that really means is that instead of the classic razor blade model, or the printer cartridge model that we're all familiar with, where you initially buy something relatively cheaply and then spend a fortune on new blades or new cartridges for your printer. Like for engine manufacturers, their revenue stream is spares and maintaining in the parts, or at least supporting these engines and service.

Boom's model is in reverse. It really wants the engine to stay on wing as long as possible and to have as low a maintenance supply revenue side as possible, because it really wants the upfront cost. It wants to get the money from selling the engine as part of the airframe. And if Boom has the engine as well as the airframe, that's where they're going to see their revenue coming in from. And there's four engines on each one, which is a pretty rare thing these days.

But the other point is that, and this is sort of to Graham's really initial point, the design of the engine itself, yes, it is simple in a way, really weirdly to sort of say that, yes, a design point engine for Mach 1.7 can be done relatively effectively and simply. The hard part, of course, is operating that engine efficiently without having to use afterburners and to also be able to meet modern Chapter 14 type noise limits and emissions.

So, what you are seeing here is the benefit really of 30 years of designs that have been done for supersonic business jets as well as optimized cycles that were never possible with the Tupolev 144 or Concorde. For example, they are looking at a variable plug nozzle, a translating nozzle, which was, let's face it, that was developed late to replace the Kuznetsov NK-144 engine when Koleslov did the RD-36. That was really a breakthrough for the Tupolev 144, but, of course, it was too late and never able to be worked on. The other thing is the inlet, which would've been applied to supersonic business jets had they come through in order to meet the cruise requirements as well as the takeoff noise limits.

So, there are innovations here, which, if you can package it, would allow this to happen and would make it work. I think my biggest worry is that I can't see yet, I don't know, as Steve mentioned, who is going to supply all of the other non-additive parts? Who's going to bring this engine together? And who's going to test it and make sure it's certifiable?

Yes, GE Additive, which will be part of GE Aerospace next year, by the way, that is great. Yeah, okay, they've proven they can certify additive parts, but Steve's right, it's more than just those parts. It's the entire engine. And then you've got the innovations like these inlets and variable exhausts. That itself, that's a massive task to do those sort of things. I love the technology, I love the idea of it, but there's so much more that we don't know about this yet.

Joe Anselmo:

Steve.

Steve Trimble:

First of all, I'm a little disappointed we haven't talked more about my supersonic flight in the Gripen a few weeks ago, but that's okay. I'll get over that.

Graham Warwick:

Sorry, Steve, I hate to interrupt, but remind me, did you just do something very significant?

Steve Trimble:

As a matter of fact, yes, but we'll get into that later. I do want to say, I mean, look, everything that I know about this company and about this program comes from the reporting by Graham and Guy. And you're not going to find better writing and reporting about it anywhere else. I went over all of it last night and this morning in between going through the omnibus budget package that just came out. But the thing I just want to point out, I think is a pressing issue for the company, and it goes to this issue of credibility, is they've got to get series C financing done. They cannot move forward into manufacturing that aircraft, manufacturing that engine and starting testing, all of which needs to happen in the next few years without a huge amount of money coming in.

And so all these things about schedule slipping, the airframe going from 40 seats to 88 seats and then back down to 80 seats, the wing completely changing, the number of engines changing, the fact that XB-1 still hasn't flown, even if really, I don't know how relevant that is to the overall program, as Graham has pointed out. It all does speak though to the credibility going to the financial community to get that series C financing. I mean, it makes you just think, I mean why, and this was always the question, why would you start a company looking at a supersonic jet without having the engine locked in from the beginning? I mean, to me that just seems like, why would you do that?

Their story all along was that it will come. Rolls-Royce will build the engine or will take the GE engine that GE was doing for Aerion before they dropped that and we'll use that. There was something out there that they could take and put on this program. And now we get to the final point and they have to build the engine. They have to do that with Florida Turbine Technologies, which has done nothing like this, ever. Again, no disrespect to Florida Turbine Technologies. It's just a different thing.

So, you put all that together and I have very serious questions. The business model also, I mean, we saw this happen with C Series, Bombardier coming up with this, actually a really good aircraft. They did everything right and they still can't get the business case to make it work with the airlines, because Boeing and Airbus can sweep in and underbid them in a heartbeat. SpaceX was entering a market that had no competition. They were at a low-cost rocket that was actually simplified from the stuff that was being done by their competitors. Airbus and Boeing with C Series had a low-cost product, maybe not as low cost or as purpose-built as C Series was for that market, but they could come in with sweetheart deals to bury the C Series in the market, which is exactly what happened.

Boom has got all that to face going forward, in addition to the technical challenges, in addition to the financing challenges, and the fact that they're the first aviation company that I can think of since maybe the 1920s that's doing their own airframe and their own engine at the same time.

Joe Anselmo:

So, Guy, we're running short on time, but I wanted to let you respond and then I wanted to let Graham take us to the finish line.

Guy Norris:

Okay. Well, thanks. Yeah, I just wanted to say that, and this is a good point, it's sort of brought on there by Steve's comments. One of the things that I did notice about the evolution of the Boom design was that it has all the way, just like Concorde did really... I mean, when you think Concorde began as this sort of Caravelle type transport on short to medium European roots and then quickly evolved away into something which it became. We've seen a similar evolution with Boom. And part of that work, particularly in the last two years, through its Rolls-Royce connection, has been this change from three to four engines and reduction in speed to 1.7 from 2.2.

And I think that's been a key part of, also, this transition away from having to rely on existing cores. Yes, it would've been great to do an existing core, but if you go to a new model where you're using, as Graham mentioned, this passive cooling in the turbine and a whole different way of looking at it, that really is the nub of this whole argument that Boom's got. You have to design an engine totally different from the very center of the high pressure core outwards. And you can't do that anymore by relying on existing cores. If you went to a Trent 1000 core, you’d have to start from scratch anyway, because every single cooling aspect of that engine design has to change from that point. So you might as well start from scratch.

So in a way, if you can do that, then you have the benefit of evolving a bespoke engine from the get-go. That didn't even happen with the Olympus, even the Olympus when the Bristol Siddeley design was optimized around a cooling pattern, ancient though it was, for a different mission and a different role. And it was the same with the Kuznetsov engine for the TU-144. So, nobody's ever had the chance to purpose design for a mission like this from literally nowhere. So, who knows? I think there's a lot of potential out there. And I completely agree with you on the other things. Where's the money going to come from? Who's going to do the testing, and who's going to put it together? But from a concept perspective, I think it's got a runway ahead of it.

Graham Warwick:

So, I think we really need to focus down here is the change of business model that this represents. That's the disruption here. It's not supersonic transport, it's not Boom. It's the fact that somebody said, "We can design an engine and we can do it on the basis of making money, selling the engine and not making money maintaining the engine."

It may not be Boom that brings this to market. But you are seeing this across the industry at the moment. A lot of the startups are propulsion first and they are having to develop the airplane to go with the propulsion system as a second step.

Airbus two weeks ago said it's going to develop its own fuel cell engine. Now it's just for a test at this point, but this is a shot across the bow of the propulsion industry, saying that there are other ways to get an engine than coming back to you time and time again, and having the same business model time and time again. That's the disruption.

Joe Anselmo:

And on that note, we will wrap up for this week and this year. Thank you, Graham. Thank you, Guy. Thank you, Steve, for all your thoughts. I'm sure we'll be talking more about this and all these topics next year. Special thanks to our producer in London, Guy Ferneyhough.

To our listeners, thank you for your time and support throughout the year. We wish you a happy holiday season and a safe and prosperous new year.