Pontifications: No engines, billions shy, devastating enviro analysis, Boom’s CEO still exudes optimism

By Scott Hamilton

Sept. 20, 2022, © Leeham News: Blake Scholl, the founder and CEO of Boom, the start-up company, continued to paint an optimistic picture about the Overture Supersonic Transport.

He told the US Chamber of Commerce Aerospace Summit last week that the Overture, a Mach 1.7 88-passenger aircraft concept, will revolutionize international air travel.

But Boom has big challenges ahead—not the least of which is that there is no engine manufacturer so far that has stepped up to provide an engine. The Big Three—GE Aviation, Pratt & Whitney, and Rolls-Royce—have either outright rejected participation or other priorities exist.

Plethora of Challenges
  1. Rolls says publicly it won’t pursue an engine for Boom. GE told LNA it’s not interested in developing an engine for Boom. P&W is focused on advances for its GTF, developing sustainable technology and military engines.
  2. The International Civil Aviation Organization (ICAO) in July issued a report on the environment that eviscerated SSTs and the SAF concept outlined for Boom. The report included analysis from the International Council on Clean Transportation (ICCT).
  3. Scholl claims a market demand for thousands of SSTs but Boom’s 2013 study by Boyd International forecast a market demand over the life of the program of 1,318 Overtures. Some thought this figure was generous.
  4. Boyd’s report also concludes Boom needs a Mach 2.2 airplane to be commercially viable. Scholl reduced the speed to 1.7. This means that in some cases, airline crews can’t do a round trip from the US to Europe without a relief crew, which upsets some of the economics.
  5. If Boom were a publicly traded company, all the orders would fall under the ASC 606 accounting rule that questions the viability of those orders.
  6. Scholl told AIN Online Boom needs $6bn to $8bn to come to market and so far, it has raised $600m.
  7. And we don’t get into the certification and regulatory hurdles. Among them: In his presentation to the Chamber, Scholl said there are 600 potential SST markets. He included some inland in the US, where there is a ban on SSTs flying over land.

No engines

With Rolls and GE saying they aren’t interested, and P&W’s priorities focused elsewhere, where will Scholl find an engine for the Overture? Flight Global reported that GE’s partner in CFM International, Safran, also says it won’t provide an engine.

Scholl is undeterred. In a quick interview following his presentation, he said Boom would have an engine partner by the end of the year. With RR, GE, Safran, and P&W uninterested, Scholl nevertheless said he will have an announcement by year-end. “I’ll tell you when I can tell you. I feel really good about this.”

Sustainable fuel—not for SST

This summer’s report from the UN’s International Civil Aviation Organization on reducing the environmental impacts of aviation throws doubt on the viability of super-sonic commercial jets. The report’s inclusion of analysis from ICCT said supersonic transports don’t fit in with the industry’s need to drive carbon emissions down, and it specifically rejects the idea of using sustainable aviation fuels (SAFs) to power jets flying faster than sound.

“In a nutshell … supersonics are a poor use of scarce SAF supplies,” the ICAO/ICCT report said.

The problem is that supersonic engines burn seven to nine times more fuel per passenger-seat-kilometer than similarly sized sub-sonic jets, the report said.

And with SAF costing two to five times what standard aviation fuel does, “the combination of SAFs higher cost and SSTs greater fuel intensity could increase fuel costs to 25 times that of subsonic aircraft burning Jet A, threatening the already questionable finances of supersonics,” ICAO reported.

SAFs also would do nothing to lower the impact of commercial aviation on global warming, the report continued.  “More surprisingly, even if SAFs were widely available, their use in supersonic flight could actually backfire after accounting for the full atmospheric impacts of SSTs.”

Because SSTs fly at high altitudes – Boom says 60,000 feet — the emissions from their engines hang in the air longer.

Furthermore, because of the specific characteristics of SAFs, burning that particular fuel at those altitudes “could actually exacerbate the medium-term climate impacts,” the ICAO report warned.  Citing data from NASA and the Massachusetts Institute of Technology, the agency said supersonics burning SAFs high in the atmosphere would have 120 to 230 times the climate impact of a subsonic jet burning kerosene at lower altitudes.

“Assuming that SAFs can address the climate impacts of supersonics is premature,” the report concludes. “Moreover, economic modeling concludes that the high cost of SAFs will make them cost prohibitive for supersonics for the foreseeable future.”

Scholl was dismissive. “This is the first airplane capable of net zero carbon. It flies at a higher altitude, which is advantageous in a whole bunch of different ways. We care deeply about making this not just good for passengers and not just good for airlines, but also good for the planet. We take the science really seriously. Whenever we have opportunities to make the airplane more friendly for the planet, we do. That’s part of why it’s a Mach 1.7 airplane vs 2.2 where we started. A lot of that is about minimizing noise footprints around airport communities, making it as quiet as the latest generation airplanes.

“We think this is going to be a net good for humanity in a really big way.”

Market demand

Scholl recently repeatedly claims there is a market for “thousands” of Overtures. The 2013 Boyd study estimated the demand from 2022 to 2032 of 1,318 airplanes. In the interview, Scholl declined to reveal what “thousands” means.

“To take people who are flying subsonic business class supersonic on routes where there is a big speed up for passengers and enough demand and the appropriate fares to make the airplane profitable, there are hundreds of airplanes in commercial use without assuming any kind of demand stimulation. People fly more when flights are faster,” he said.

“As we’ve partnered with Northrop Grumman and deepened our ties with the Department of Defense, we also see this as a very significant platform to provide a capability for Defense. It’s like we found the other half of the market there,” he said. Taking Boyd’s estimate at face value, Scholl’s response suggests demand for 2,600 Overtures.

Mach 1.7 vs 2.2

The original Overture concept envisioned a Mach 2.2 airplane. This was later revised to Mach 1.7. In the 2013 Boyd study, the higher speed was described as a “critical factor, as the market advantages of slower supersonic speeds—for example, the 1.5 Mach now planned for some proposed business jets—are not sufficient to offer significant time-reductions on long haul flights.” Mach 1.5 is 1,150 mph; Mach 1.7 is 1,304 mph and Mach 2.2 is 1,687 mph. Scholl said the lower speed is more environmentally friendly (see below).

“We’ve looked at that in a lot of detail and we feel great about 1.7 Mach,” Scholl said. “That’s part of why United and American are placing orders. The airlines are voting with their dollars.”

However, a technical perspective concluded that Mach 2.2 is beyond the capabilities of the engines that have been examined. Even engines capable of Mach 1.7 have a huge drawback: they’d have to be overhauled after only 4,000 hours.

Conditional Orders

While Scholl touts nearly 130 orders from Japan Air Lines, United, and American airlines, these are conditional orders. If Boom was a publicly traded company, all would be classified as not firm under ASC 606 accounting rules.

“Most importantly, we have to deliver the airplane that has been promised,” Scholl said. “We would not have the customer relationship we have if the airplane we were building was not one that the airlines wanted.”


Boom has so far raised a fraction of what is needed to bring the Overture to market. AIN Online reported that Bloomberg’s aerospace analyst estimates Boom needs $10bn. “Boom claims to have drawn $600m of its estimated requirement of between $6bn and $8bn…,” AIN wrote.

Scholl declined to make any additional comment during the interview.

Entry into service

Entry into service originally was targeted in 2023. Now it is targeted for 2029.

Bryan Corliss contributed to this report.

49 Comments on “Pontifications: No engines, billions shy, devastating enviro analysis, Boom’s CEO still exudes optimism

  1. Boldly Moving Forward both Scholl & Putin seem in need of Glorious Withdrawal options.

  2. What’s Scholl’s salary? A nice amount, I bet. He gets it every month one way or another, regardless of what transpires. So, just keep up the illusion of viability for as long as possible, and keep raking in the cash.

    A bit like Dave, when you think of it.

    • ^^^ this ^^^

      the whole thing is (at this point) a grift. how long can they drag this out sucking down that sweet sweet VC money before they inevitably declare bankruptcy.

      Also, how much did the major airlines pay for their “non-refundable” order deposits? $500/airframe? and they got free press exposure fawning over the excitement of super sonic travel? bargain.

  3. The USAF and Transport Air Command might be the first customers and can specify the XA-100 or XA-101 engines on it with export probation. This allows a supercruise of M1.7 with ease. For people wanting to join the armed forces (and their parents) it will give comfort to know that downed soldiers/sailors/marines in the area will be flow at supercruise speed to Ramstein or similar hospitals. Maybe starting in a V-22 or MV-22 to the airfield with the Overture with Intensive care interior is ready with warmed up engines.
    Finding a civil engine for a limited marked will be very hard and maybe only after 20 years when F-135 engine clones are available.

    • Solution looking for a requirement.. even creating it, InnoVation.

      Just like the dozens of E-VOTL start-ups.

      At some point the eye always falls on the public Government / Defense Billions.

      • No other suitable engine is available and no one can buy or get their hands on these engines nor the F-22 engines F-119/F-120 that also would work. Historically most new tech products start as overprized government projects.
        Maybe they have to settle for the F414 engine that is flying around the world and would give supercruise performance if you have enough of them installed.

        • The critical period for someone being severely injured (combat or not) is from when it occurred to when they get to expert medical (MASH in combat).

          In other words, its spurious point of fast transport.

    • the only even potentially justifiable use case for a supersonic transport for the military/govt is to get a unique capability SOF team onsite faster and even then in many cases it would end up being overall slower as you would have to fly to a major airport (and all the high visibility that implies) first then transfer to something like a V-22 for the terminal leg where a business jet can likely get you a lot closer to the target at a more discrete location and shorten that terminal leg..

      there is no point whatsoever for VVIP transport as the support team for the VVIP needs to get there too and there isn’t room for 6 limos, 4 blackhawks a mobile command center and 100 secret service doobies in one of these.

      • Well the Overture is a big biz jet and if the government specified that its should have 4ea stock XA-100/101 engines with afterburners field length will not be a problem. It is Wright Field that decides if they want to go ahead once they have the money to spend (usually they have..) and order different versions for different applications.
        If Boom can get F414 engines without afterburners for commercial customers and with afterburners for military customers it might get a small chance to survive.

    • Why should the DoD bother to rely on a compagny without any technical / industrial / customer support experience to provide such an aircraft?

      Should they have a need for it, they already have plethora of capable mature suppliers…

  4. Scott,

    Thanks for an interesting article, seems like reality is catching up with a lot of these new moon shoot projects now.

    Would be interesting to here Leehams view on the new Heart Aerospace ES-30 hybrid aircraft as well. At least here in Sweden they managed to spin the switch from the pure electric ES-19 to the ES-30 hybrid as something very positive. The media and the general public bought their story and were also cheering the new factory/tech center Heart announced they will build on the Swedish west coast.

    I just don’t get how an airplane with 20 km range on batteries would be a good idea at all… unless you are travelling to an island without a bridge or ferry connection you would better off just taking the car to travel that distance right?

  5. An ACJ321XLR like aircraft will offer superior range, comfort, environmental impact. At a fraction of the costs. In 2 years, low risk, with choice of 2 certified, quiet engines, a decent sleep. Commonality with thousands of aircraft, pilots, spare parts, MRO shops globally.

    • Maybe the whole purpose of this plane is to make every a350/787/777/x look like an eco dream? The environmental impact is grotesque, I’m not sure if the math would even work out assuming you took that many private jets off the market? I’m no hardcore environmentalist but I couldn’t self justify that much added emission or cost for a trip savings of a few hours. to your point about spares, the fact that they’re not yet teaming with AB/BA/EMB tells me they haven’t even considered the support aspect of this

      • Noise alone is going to be the killer of Boom, even if the other factors do not kill it off before it gets to the sky. With all these 787s, A350s, 737Max and A320NEO in the sky, the general public will see these quiet generation of aircraft as “normal”. If then Boom comes back with their 70’s noise levels (and I don’t mean Concorde, but 737 and DC-9), then the airport complaint hotlines will glow red of all the complaints coming in.

        You don’t hear complements when noise goes down with a new generation of aircraft, but once it goes back up (by a lot) it will be completely unacceptable.

  6. figuring in airport overheads, the net time savings on a DC to Paris flight on one of these is about 2-2.5 hours on an 11 hour journey.

    factor in 8x fuel use/seat for that journey, 8x maintenance (on wing time for engines on 787 class are in the 25-30k hour range now, vs 4k expected here) acquisition cost of the aircraft will likely be greater than a 787-9 for an 88 seat aircraft with seating equivalent to domestic narrowbody first class. pilots unions are going to demand premium rates to fly it. you will need a whole cadre of specialized and senior maintenance techs to take care of it.

    your break even ticket price is going to be north of $15k/seat one way, which means you need to charge $30k per seat.

    you can charter a private jet for a DC-Paris round trip for ~$60k and due to the lower airport overheads of private jets, your total door to door time will likely be less than this abomination and you will have a much lower environmental impact too.

    • Agreed. Just the security check in portion of every journey, which is not reduced by screaming along at Mach anything makes this an expensive exercise in reducing a fraction of the journey time by a fraction. You could save as much time by paying for a shuttle to the airport and not having to spend time dealing with parking / returning a rental car. Besides all of this, they named the company after one of their biggest technical hurdles. Methinks they’re just after VC dollaz

  7. Sustainable Aviation Fuel is a scam as well. Producing it leads to lot’s of waste. There are no free lunches, for AGW believers.

  8. “As we’ve partnered with Northrop Grumman and deepened our ties with the Department of Defense, we also see this as a very significant platform to provide a capability for Defense. ”

    Ah we’re going to stick the taxpayer with this pig.

  9. Are there any alternatives to the big 3? Allied Signal/ Honeywell, Williams, MTU?

  10. You have to love the Boom and Boom like stuff that we are going to make massive emissions in an environmentally good manner. Arghhhhhhh

    Its stunning to see people buy into the purse BS.

    • I remember our poster was quite positive about Boom not that long ago. 🙄
      History revision after reality hits?!?

  11. At this point Blake Scholl seems like little more than a reincarnation of Bernie Madoff. Any investor who gives this charlatan another dime deserves to have his wallet sucked dry. It’s mind-boggling that Scholl continues to spew the BS he’s spewing given the reality that he has no engine, and never will.

    And to the commenters here and elsewhere espousing a military engine solution, whether off the shelf or derivative: there is exactly zero percent chance of that happening.

  12. Furthermore how likely the two engines mentioned above meet ICAO 2027 noise and emissions rule without significant update??

  13. I`don`t see supersonic as a viable market, it will always be niche. It did exist, but it was never economically sound .
    It`s pretty obvious that SST with nowadays tech is very energy demanding, and that will lead to high cost.
    While travel time will not significantly lower due to flying time in SST not being a major factor.
    Just think about a typicall NY – LHR flight.
    Flight time is about 7 hours for 5600km / 3500 mi.

    You need about 2 hours on the airport, on average 1 hour to get there, 1 hour to arrive and clear the airport, another hour till you arrive at your destination.
    That`s 5 hours inclusive some reserves in case anything fails.
    Today we are talking about a 12h trip.
    Let`s say you cant fly supersonic for the first and last hour of the flight, so now we are talking about 7 hours that will be the same.
    That leaves only 5 hours flight time open for being faster.
    With mach 1.7 you will not even half it, but even if, we will talk about a 2-3 hour save out of 13 hours in total.

    So realistically, the total travel time from somewhere in London to somewhere in NY will be 10 hours instead of 12. A 20% saving, but for the effort that has to be taken and the price it will cost in no relation.

    Oh, did i forget to mention: If you don`t have an engine, you don`t have a program.

    I don`t think it`s the right way to go for civil aviation.

    • Certainly British Airways (possibly Air France too) addressed the “airport time” component of that overall travel time equation. With a Concorde ticket, you could check in 10 minutes before departure, and at arrival they had special arrangements such they had their own passport / baggage reclaim / customs, and you’d be out the door less than 30 minutes after touch down.

      So the whole “Concorde” thing could get you from airport door to airport door inside about 3hrs 40min, which was pretty damned phenomenal. A meeting in London and back to NY really was all in a day’s work!

      • Yes, and that was pre 9/11, pre US travel requirement ESTA
        pre all the things that changed since 2000 when the Concorde stopped operating.
        Oh, and the Concorde went Mach 2,2, so 2400km/h while existing DC10, B767 and B747 or A340s were travelling about 850 – 900 km/h.

        That`s about triple.

        Now we are talking mach 1,7 and a startup, how much influence will they have to bend rules?

        SST is with given tech just an unrealistc idea from the past, and flight time is the biggest part of the trip, but even on a 7 hour flight it`s only half the time.
        You spend the time on the airport, in sec check, visa issues, check in, and after arrival at immigration, baggage pick up, etc.

        If you don`t have time, you`ll do an online meeting.

      • That would certainly be a significant factor that would make a big difference, but I highly doubt whether such arrangements could be instituted again, post 11/9 (Yes, I’m being deliberate by calling it 11/9, and not 9/11.) [I have made a lifestyle out of swimming upstream.] A special boarding process (facilities) would have to be factored into the ticket price, and then, as one other poster here has noted, the ticket price is not that far off the cost of a shared business jet. This thing just doesn’t have a viable business model. Remember that it (the aircraft) would have to earn for its owners (the airlines) the majority of its revenue within the continental US – so over a land mass where its boom would be a big problem, and they have yet to solve that problem, although, without engines, they won’t actually have that problem, now will they?

    • “It`s pretty obvious that SST with nowadays tech is very energy demanding, and that will lead to high cost.”

      I guess the first law of thermodynamics will ensure that even with future tech, the fundamental principle of “SST needs more energy than subsonic” won’t change. 😉

      Agree with the rest of your post as well.

  14. Perhaps a few EJ200’s are going to fall off the back of a lorry somewhere, end up on a Boom SST…

    • So, Bill7 was suspended for 30 days for repeatedly misbehaving in comments. He was notified in this forum of the suspension. He changed email and ISP and came back before the 30 days was up. So I’ve now extended his suspension by another 30 days, to Oct. 30.


  15. “Scholl was dismissive. “This is the first airplane capable of net zero carbon.””

    What the actual…?!?

    Setting aside for a moment the order of magnitude greater fuel use and high altitude emissions than conventional aircraft, what does that make existing aircraft like the Pipistrel Electric???

  16. -> Undisclosed F-22 engine trouble prompted ongoing fleetwide hardware fix http://ow.ly/KVQb50KLArs


    “The issue has racked up nearly $23 million in damages for the service stemming from seven Class A engine mishaps…that spanned nearly a decade and prompted a retrofit effort beginning in 2019 that is slated to finish next year.”


  17. “This is the first airplane capable of net zero carbon.”

    Well, without an engine, he might be on to something.

    “It flies at a higher altitude, which is advantageous in a whole bunch of different ways.”

    “Whenever we have opportunities to make the airplane more friendly for the planet, we do. That’s part of why it’s a Mach 1.7 airplane vs 2.2 where we started. A lot of that is about minimizing noise footprints around airport communities”

    That just reads like a fairly disconnected load of drivel that would probably impress some people on Shark Tank/Dragon’s Den.

  18. I have been following the Boom story and now have a mild case of deja-vu. When I was young I built Concordes with my own hands and later had an office just down the corridor from Dietrich .. the brilliant aerodynamicist who came up with the ogive delta wing in the early 1960s. In 1997/8 I was briefly technical head of the 250 seat ESCT Trinational Concorde replacement programme. Not a small programme and we had huge ex-Concorde experience to draw on. What quietly worried me was when my tame meteorologist said that the Global Warming NOx emissions would not wash out of the atmosphere at the Mach 2 cruise height of 60kft. Certification? A lot of what this article says rings true. Sadly, because it is a great engineering challenge and boundaries need to be pushed. Now it looks like a smaller version of our ESCT but with a tailplane, slower, reduced payload/range and no sign of a viable engine. And then there is the unflown technology demonstrator….seems very quiet in that direction and anyway, how relevant is it now to the current configuration? Maybe they need a hard headed, and independent, Project Review. And oodles more money.

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