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Comment by nikhizzle | Hacker News Reader

Interesting that this is slower that the Concord which cruised at Mach 2. I wonder if a slightly lower speed makes the economics more sustainable.

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Boom were previously targeted a cruising speed of Mach 2.2, I wonder why they lowered it to Mach 1.7 with the latest design update.

Might be related selecting an engine. The previous version of the design had a fantasy engine that didn't exist (I think the specs came from a military engine that they couldn't use due to export restrictions), but now they are working with Rolls-Royce, and appear to have actually selected an engine design. It must be smaller than what they originally wanted, because they moved from a 3 engine design to a 4 engine design.

To me that sounds like a fuel saving option. Might extend the routes.

Export restrictions are not just messing cryptography!

Maybe military engine control systems work by sending PGP-encrypted emails to the fuel valves?

But helping mute the airforces of Russia and China

Supersonic heat also. Concorde was in Aluminum and at 2.1 mach it was at the very limit of what could be done in aluminum. Which required a very "tight" design, engineering marvel in fact. Go faster and one have to go for titanium, which is much more difficult to work with and manufacture.

Didn't the Blackbird weep jet fuel because the seals couldn't hold when the skin was at ambient temperature?

I heard they put enough fuel in it to take off and get up to temperature and then refueled it in the air for safety reasons.

If this is achieved without afterburners (as I understand it is), then yes, this is an immense difference in fuel consumption and radically impacts the economics.

Concorde only used afterburner(en_us)/reheat(en_uk) for a small part of the acceleration phase of the flight not for cruise.

It used afterburners for takeoff and accelerating through Mach 1.

Well past Mach 1 actually, reheat was cut off at Mach 1.7.

Note that Concorde "B" was meant to use a variant of the Olympus 593 without reheat, but ultimately lack of sales of the original aircraft doomed it.

Afterburner is a common term in both countries. Reheat is and always was a semi-official slang used in the UK and is a reference to the similarity in concept to reheat steam turbine.

It's en_gb and not en_uk (although UK is exceptionally reserved [1], and we recently begun using UK on car nationality identifier stickers).

[1] https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2#Exceptional...

GB is the more neutral term, UK is pushed by the Conservatives and nationalists/royalists

GB is not more neutral - it excludes Northern Ireland, which is a part of the UK.

Aside from any such associations, they mean different things.

People often use the terms imprecisely, but (for example) if Scotland were to leave the United Kingdom, it'd still be part of the island of Great Britain.

GB is not "more neutral".

Great Britain is the name of the post 1707 Union of England and Scotland. It's not neutral if you are a member of the Unionist community in Northern Ireland.

The United Kingdom is the name used by the country at the UN but is, of course, not neutral if one is a member of the Nationalist community in Northern Ireland.

No one uses .co.gb domains.

Here .... en-ie and en-gb are different things, because the Irish English dialect is a bit more distant from British English than the Scottish one. Whereas .uk is a country code representing a specific political entity.

It doesn't seem very neutral to go around demanding others call you great.

Yes I know.. that's not how the word is meant in this context...

So afterburner then. 'Merica.

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