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I work in aerospace and I don't find this development strategy unusual prima facie. I don't know if Boom is explicitly doing rapid spiral development, but this is what it would look like from the outside - a development vehicle that doesn't resemble the final vehicle design in many ways, but does have strategically selected commonality to validate and buy down risk on specific subsystems and operational concepts. They may be retiring XB-1 simply because they got the data they needed.

That being said, I share your skepticism of Boom as a company. As far as I know, they still don't have an engine for their production aircraft design.

Yeah.

The demonstrator was to validate some basic concepts they were promoting about being able to achieve supersonic flight without supersonic booms. It achieved that at relatively low cost, and gave them something to brag about, an indication of baseline competence at certifying airframes and possibly ticked off some investor boxes. There wasn't much more to be learned about large passenger jets using their intended custom engines from a small GEJ85 powered platform, so its not surprising they haven't gone to the expense of continuing to fly it. It's not going to be useful for most other stuff they might want to test, apart from perhaps their intended custom engines which are probably years away from being certified for flight tests, never mind hitting performance and reliability targets.

I wonder what kind of liability it would be to sell a one-off prototype plane like that. Guessing it would also have more value has a model in the lobby or on a pole outside headquarters one day than they would earn in selling it.

It's hard to see why anyone would pick an airplane like this over a surplus, demilitarized fighter jet (only one of them has spare parts)

> There wasn't much more to be learned about large passenger jets using their intended custom engines from a small GEJ85 powered platform,

This is key to me.

I'm a layman in Aviation, so I'll unpack that.

The Boom XB-1 demonstrator (1) uses GEJ85: the General Electric J85 engines, as seen on military jets (2).

This is not the desired production jet's "Symphony" engine (3), which at a guess has to be both larger and more efficient?

So whatever is to be learned from the demonstrator, it doesn't tell us much about the final engine design.

In fact, all I know about this desired engine, is that Rolls-Royce isn't making it. (4)

Are they still planning to design the engines in-house? If they're making good progress, why are we hearing about how they're replacing excel as a design tool.

As I said in the other comment:

I'm not an expert, but this seems like the engine is on the critical path to success, and also high chance of failure. i.e. Without engines, they have nothing but a glider.

And if Rolls-Royce thinks that it's either not technically or commercially feasible, then who can do it?

1) https://en.wikipedia.org/wiki/Boom_XB-1

2) https://en.wikipedia.org/wiki/General_Electric_J85

3) https://en.wikipedia.org/wiki/Boom_Symphony

4) https://www.space.com/boom-supersonic-rolls-royce-engine-spl...

From [4]: > Rolls-Royce's work over the last few years

So Rolls sank several years of investigation into it before cutting their losses.

From [3]: > Boom aims for production of the engine to begin in 2025 at the Overture factory at Greensboro, North Carolina

Mark your calendar ...

It seems developing a new engine a relatively rare, difficult, expensive, and risky endeavor in aviation. Notice none of the aircraft companies make their own, right? It's CFM, PW, and RR.

But Boom has a bunch of propulsion engineer openings so it looks like they're really going for it.

The saying in aviation is "don't develop a new airframe and a new powerplant at the same time".

Sure there are counterexamples, but they have good reasons to think that this is more than double the difficulty of developing one of these parts. And that the engine will take longer.

The HP.115 [1] and BAC 221 [2] were not exact scale replicas of Concorde.

[1] https://en.wikipedia.org/wiki/Handley_Page_HP.115 [2] https://en.wikipedia.org/wiki/Fairey_Delta_2#BAC_221

My take is that they felt like they were already pushing their luck with the prototype and didn't want to scare investors away when it inevitably crashed.

I share your skepticism, especially with their timeline. It has been some time since I looked at them closely, but they originally pitched developing their own supersonic capable turbofan to power their eventual production model. Especially with such a small team that seemed overly ambitious to me.

Hah.... in the back of my mind: announce they're going to crash it before the fly it.

"This flight we're validating our model by pushing the real world to the limit. It should explode about 38s into the test and crash. We've cleared the expected area"

Hopefully the plane is autonomous

The market for Boom is not commercial passenger flights. So much time is wasted with security, boarding, taxi-ing, waiting at the destination for a gate to unload, etc. that the flight speed is not a big deal. Existing commercial passenger jets could already go faster without going supersonic and save some time, but it doesn't matter. Even if you fly commercial passenger jets at the absolutely face-melting Mach 3.3 of the SR-71, you don't really save enough time to matter. The maximum speed in flight doesn't do anything to address ground delays.

> time is wasted with security, boarding, taxi-ing, waiting at the destination for a gate to unload, etc.

Airlines can optimise for this. Digital ID virtually eliminates security lines. Paying up for gate, t/o and landing spots takes care of the latter. There is a cost tradeoff for service in the airline business. An all-business airline flying Booms would almost necessarily have to pay up to negate these issues. (That or fly out of the FBO terminal.)

Airlines do not dictate airport security.

You cannot simply add gates to airports with even an infinite pile of money. It doesn't matter, unless you're going to make flights from nowhere to nowhere. Doesn't sound like a business strategy to me.

> Airlines do not dictate airport security

Airlines absolutely choose whether to participate in various programs. Digital ID was cited for a reason.

And in some cases, the airlines have substantial control—Delta One has a separate security line at JFK.

> You cannot simply add gates to airports with even an infinite pile of money

You don’t. You outbid someone else for the existing ones.

> And in some cases, the airlines have substantial control—Delta One has a separate security line at JFK.

I'm actually surprised more airports don't have VIP level gates that the airlines can pay a premium for allowing them to charge a premium to their passengers. It'd be interesting to see where the price could be that would guarantee enough passengers willing to pay the premium for much reduced airport headaches.

There’s probably a classist risk to this (recall the uproar over the residential building in NYC that had separate entrances for different unit classes), let alone the logistics are needed at whole-airport level to support it which is difficult to retrofit.

Just build an entirely different terminal instead of shoeing it into the same building as the terminals for the plebes. Out of sight, out of mind.

The classist risk is already there with the pricing they have for first class seats. By making first class only planes, you can have economy only planes like Spirit. Then nobody would be complaining about first class since nobody would see first class. I see no downsides with this concept!

Ah, I was referring to loading the same plane from different gates, which I’ve been told exists at some airports (boarding from business/first lounge one floor above the standard gate)

That's what you would consider classist? How about a lavatory for use only for first class. How about "closing" off the first class part of the plane with a little curtain? None of this suggests to me the airlines are trying to not be classist

> I'm actually surprised more airports don't have VIP level gates

They all do. Delta’s is branded VIP services. They’ll meet you at the curb and shuttle you behind security and in a car to your plane.

But at that point, in most cases, fly private.

Participation in a program does not dictate whether any specific passenger or non-specific passenger can get through TSA in any fixed amount of time. TSA may unilaterally impose any security measures upon any passenger of a commercial flight and may also unilaterally prohibit any passenger from boarding a commercial flight.

No such restriction exists upon private jets

> You cannot simply add gates to airports with even an infinite pile of money.

I was once on a short internal US flight. We recognised an "elder statesman" politician, a Senator who owned property in the area of the city that we were going to.

He was seated at the front, and was given the opportunity to leave the aircraft a minute before anyone else - no luggage beyond a briefcase. Of course, by the time we deplaned he was nowhere to be seen, by then he was likely in the back his car already. Who needs a separate gate when the VIP can be guided through ahead of the rest, through some usually-closed door?

That may be true for domestic coast-to-coast flights, but not for transoceanic ones across the Atlantic, or especially the Pacific, or north-south across hemispheres, that can take 8+ hours. Flight time is a higher portion of the total travel time in those cases, and seems like the main market for Boom, especially if they initially target Business Class flyers who do those kinds of trips regularly.

Boom XB-1 did 750 mph air speed. If I've got an 8 hour flight at 561 mph in an A380 that's a reduction to 5.984 hours when I move to the Boom XB-1. Who cares about saving 1.1 hours on a transatlantic flight. There is a reason why Concorde's cruise speed was 1,341 mph.

So when Boom makes a commercial airliner that hits 1000+ mph with the same availability and turnaround time as a typical passenger plane then I'll pay attention. Until then, it's for rich people who can buy their own plane.

XB-1 is only the demonstrator. They aim to produce commercial airline that can cruise at 1.7 Mach. NYC to London in 3.30h instead of 6h.

Rich people can already buy private jet that is much more comfortable than supersonic one.

https://boomsupersonic.com/overture

8 hours - 5.984 hours = 1.1 hours? My math works out to just over 2 hours of time saved.

My mistake, it is 2 hours of time saved.

Not disagreeing with you at all.

What is the market for Boom?

I see you never flew from LAX to ICN.

It's also largely PR guff. The first privately-developed supersonic aircraft was the Northrop N-156F, forerunner of the F-5, that first flew in 1959. Funded entirely from company funds with no military contract. And it went supersonic in its first flight with no drama.

In fact the chase plane for the Boom XB-1 is a T-38, derived from the N-156F. It can outrun the XB-1.

I'm not sure how strictly privately developed the N-156F is given you could easily argue that reuse of design, knowledge and relationships from existing contracts saved them a lot of money.

I think part of it was that they were testing a new aerodynamic design that eliminates or minimizes sonic boom, so they can go supersonic over land almost immediately after takeoff, and operate over populated land routes. It makes sense to test that kind of thing with the smallest possible model first, then see if you can scale it up to passenger size without losing that quiet acceleration. Their timeline for doing that may be optimistic, but what they're doing makes sense.

The XB-1 doesn't have any boom reduction shaping. That's the NASA X-59, though that aircraft is pretty much a dead-end in that it's not scalable to a passenger configuration.

The XB-1 made use of an atmospheric trick to minimise boom propagation to ground level on one test flight, so well-known in fact that Concorde sometimes used it to accelerate as it coasted-out without an audible ground-level boom. Unfortunately that trick runs out at about M1.17.

Their immediate goal is to get the next round of funding. Viewed from this lense it makes a little more sense.