Taking a closer look at another Boom Supersonic milestone

In the wake of Boom Supersonic’s successful subsonic test flight of its demonstrator aircraft, the XB-1 last month, the company’s founder says they are on track for supersonic flight in 2028. The vehicle he’s hoping to launch is Overture, to be built at its manufacturing facility in Greensboro, and billed by the company as the world’s fastest airliner. He’s also confident that the engines will run on sustainable aviation fuels. But some industry professionals remain skeptical that either goal can be achieved within the proposed timeframe or beyond.

The original plan for the XB-1’s first flight was late 2017. Boom CEO Blake Scholl remains unphased by the delay. He says the Overture supersonic airliner will enter service in 2029 with a first flight sometime in 2028, and he patterns the plane’s development after what he calls “the last good commercial aircraft program”: Boeing’s 777.

"And that airplane was five years from firm configuration — meaning the napkin sketch of the airplane, the layout is done — to certified to carry passengers," says Scholl. "It delivered to United on, literally the day it was promised. And it was a high quality, safe airplane from day one."

Director of Research for the International Council on Clean Transportation Dan Rutherford praises XB-1’s recent success but says it might not be a straight line to Overture.

"The number of engines are different," says Rutherford. "The type of engines are different. Obviously the size is different. So, they're sort of test flying something that may or may not be relevant to their final design right now."

Another important difference he says is money. According to the company’s website, Boom has raised more than $700 million from investment and other capital sources. Rutherford says Boeing’s 777 cost several billion dollars to develop, spread out over three engine manufacturing competitors. Boom is developing its Overture engine, called Symphony, all on its own.

"I'm so excited that we're doing our own engines," says Scholl. "The Symphony effort started about two years ago and we've made incredibly rapid progress with it. The engine design has come a long way. We've already started our first hardware tests, and we'll have our first prototype engine core generating thrust in a little under 18 months by the end of the next year."

Scholl says a lot of skeptics said they could not build a supersonic jet and the XB-1 proved the naysayers wrong. Dan Rutherford says the broader question was not can it be built, but can it be built with the investment they currently have, within the company’s aggressive time frame, and using sustainable aviation fuel (SAF).

"One of the promises Boom made was that when they were going to test fly XB-1, they were going to use 100% SAF on it," he says. "And they announced a partner named Prometheus fuel and that company never provided them the SAF for it. So instead of operating on SAF, they're trying to offset the emissions."

Scholl says he stands by the company’s long-term vision for Overture.

"Our goal overall is to deliver supersonic flight that is affordable, safe and sustainable," he says. "And so while Overture can run on any blend of sustainable fuel and traditional jet fuel, it's really optimized for sustainable fuel and runs best on 100% SAF."

Rutherford says he fails to see the connection between the company’s environmental intentions and the XB-1 prototype, particularly with regard to its legacy turbo jet engines which he says are used on military aircraft.

"The engines that are on XB-1 are absolutely not sustainable," says Rutherford. "In fact, they're actually too dirty and too noisy to be used in commercial operations. So there's absolutely nothing sustainable about XB-1, and the idea they’re sort of they're patterning sustainable technologies for Overture is just not correct."

Another factor in the sustainability debate is that once the aircraft is in service, the manufacturers — in this case Boom — don’t buy the fuel. That's up to the airlines.

"And there's good economic modeling on here that because of the extra costs of SAF, and also because supersonic aircraft will be very fuel inefficient, it's much more likely that the airlines will burn conventional fossil fuels than they'll actually burn SAF when they actually use the plane," says Rutherford.

Another challenge he says is availability. According to Rutherford the more expensive sustainable aviation fuels currently make up less than 2/10ths of 1% of global jet fuel supply.

Major oil producer Saudi Arabia has a keen eye on this market. Last October, one of Boom’s investors came from the Saudi NEOM investment fund. The amount has not been released.

"As a private company we don’t announce every bit of funding we have, so I can't comment specifically," says Scholl. "But the backing that we've gotten from NEOM is actually tiny. The nature of that will kind of become more clear down the road. But they're a very, very minor investor in Boom."

Moving forward, Rutherford says people will be closely watching the company’s progress as it attempts to thread the needle between the 18-month horizon for developing the Overture engine and the additional investment capital Boom is able to raise during that period. He says scalability, sustainability, and market demand questions remain unanswered for now.