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Comment by thinkingkong | Hacker News Reader

I havent spent much time digging into Booms plans before but its sort of wild that their secret weapon was just… nothing? We already know we have airframes that can achieve supersonic flight, so why wasnt the engine design the number one priority?

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Their secret sauce, at least according to marketing was composite materials and high bypass turbofans, which combined could make a drastically more efficient plane than the Concorde.

I know nothing about Boom, but the "high bypass supersonic" thing raises the obvious question, how do they avoid the drag from the large (by definition) cross sectional area of the high-bypass fan?

I'm not privy to what Boom is doing, but variable intake geometry easily takes care of this.

You still have the massive frontal area though

They actually wanted medium-bypass engines. Low-bypass relative to modern airliner engines, but high-bypass relative to supersonic military turbofans.

High bypass turbofans are the "engine" part we're talking about no body wanting to make for them. How saucy is an engine that doesn't exist?

And composite materials like on the A350 and 787 have been around, see the A350 and 787.

> High bypass turbofans are the "engine" part we're talking about no body wanting to make for them. How saucy is an engine that doesn't exist?

The plane doesn't exist either, it was a plan.

> And composite materials like on the A350 and 787 have been around, see the A350 and 787

Their point of comparison is the Concorde. If they can make a plane that is significantly cheaper than the Concorde, thanks to the great tech that is now mainstream (composites, turbofans, CAD) but wasn't back then, it can be similar in cost to modern day business class, while still being supersonic. At least that was their marketing pitch, i don't see it taking off without an engine.

And not just an engine design but an engine design that fundamentally changes the economics of commercial supersonic flight.

I thought noise was the issue with commercial supersonic flight not economics.

Noise is an issue for overland flying (which of course affects the economic viability of a supersonic aircraft).

But even if you assume there's a viable transatlantic market for supersonic flight, you probably can't charge all that huge a premium over business/first. If your premium has to be 2x to 3x, I doubt you have a market.

Handwaving away noise issues with supersonic flight over land gets you closer to something viable. But you still need economics that aren't that different from an all business-class subsonic. (And my understanding is that British Airways had trouble making all business work on the London to New York route.

>And my understanding is that British Airways had trouble making all business work on the London to New York route.

I don't know - the all-business class A318 service from London City to JFK ran from 2009 to 2020 and was up to two flights a day for a significant part of that time. I guess it was really Covid that killed it.

Fair enough. Although that is also obviously not a run-of-the-mill city pair.

Both. Noise limits where you can go, and that limits who will want the service.

Maybe they could use a SABRE engine:

https://en.wikipedia.org/wiki/SABRE_(rocket_engine)

Mind you, I've been hearing about that since I was at high school and I'm in my late 50s. :-)

Their secret weapon is that their product is their valuation and the hype surrounding it.

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