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.

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notahacker 5 days ago | parent | next [-]

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.

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SideburnsOfDoom 4 days ago | parent | next [-]

> 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...

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everybodyknows 4 days ago | parent [-]

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 ...

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imglorp 4 days ago | parent [-]

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.

	▲	SideburnsOfDoom 4 days ago \| parent [-]
		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.

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dylan604 5 days ago | parent | prev [-]

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.

	▲	SR2Z 3 days ago \| parent [-]
		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)

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rjsw 5 days ago | parent | prev [-]

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