Why No One Will Build an Engine for Boom's Supersonic Plane | Hacker News Reader

Why No One Will Build an Engine for Boom's Supersonic Plane

viewfromthewing.com

16 pointsOzzie_osman15 comments

I'm curious as to known state of the art and conjectured designs that could work for them -- that is, is their goal even possible?

And not that they have the runway to do this (bad pun), but to do a SpaceX style rapid iteration on design / production techniques that could make it happen.

It's not that I weep for the rich to be unable to fly around the world faster than the rest of us -- just general fascination with technology and where it can go.

Everything about Boom has been dumb-shit from Day 1. From their name to their design concept. It's the kind of thing one expects when VCs are seduced by people in fields they don't understand. My view is that if large-scale commercial supersonics has a future, it will be in low-boom types, assuming X-59 does well and overland low-boom supersonic flight is permitted. Renewable or synfuels at acceptable cost will also likely be needed to avoid political suicide.

It is a much more expensive proposition for supersonic cruise engines than subsonic so even more critical you get an engine OEM onboard, figure out your market, and get a solid design point nailed down quickly. If you're off even a little bit in efficiency, it will very significantly affect the aircraft's market viability. If I were an engine company, I wouldn't put my own R&D funds into this area yet, and especially not toward Boom's design point.

Even more stupid things than Boom: commercial endoatmospheric hypersonics, and SpinLaunch. I can't believe SpinLaunch has funding.

The one "science fiction becomes reality" concept that could one day (not today) be viable is sub-orbital (exoatmospheric) point-to-point transport. But there's a long way to go to make that more routine and it's hard to see a path to safety better than subsonics. Subsonic/transonic commercial transport is a real sweet spot.

Claimer: I'm a practicing aerospace engineer, and do not work for Boom or their competitors.

Thanks for the insights. Any links for simple folk like myself to see what the right way might look like?

I'm not sure how accessible this is for the layperson, but I thought this report was pretty well done: https://ntrs.nasa.gov/citations/20150015837

Also, I didn't really answer your question directly before, but SpaceX-style iteration in this arena is unlikely. Unlike launch, which has high margins, commercial supersonics would be competing by trying to "build a better mousetrap" where "better" means "faster, but more expensive to develop, operate, and has a smaller addressable market". Iteration could build design team competence, but iterating the design itself would be extremely expensive and wouldn't have enough potential payoff to merit the necessary $Billions of pre-production investment.

It was a wee bit dense, but I appreciate the effort.

My naivete as a software guy is that the advancements and cost drop of computational modelling, ML/AI, and 3D printing could enable a small team of smart people the opportunity to "think outside the box".

The engine costs about as much as an airframe to build. If your scrappy start up builds an airframe on the cheap you still incur all the legacy costs of engine manufacturers.

Also Pratt is a solid 3rd tier manufacturer. It’s really GE and everyone else is far behind

I see two paths:

An engine maker waits for Boom to go into liquidation and buys their airframe innovation to sell engines they have control over the design costs and process. Think how Honda is an engine maker that happens to sell cars to sell their engines. Existing engine makers don’t want to be left holding the bag for Boom’s dev costs if they don’t succeed, something engine makers have little control over. Boom is a startup, and most startups fail.

Some nation state sponsors this as a vanity project. Think Emirates. Not as likely as the first option imho considering geopolitics and macro economics, but there are folks with exceptionally deep pockets who prefer a return of something other than monetary (status, etc).

Boom can’t go the SpaceX route and vertically integrate (airframe, engines, etc), including selling directly to customers, because of the capital costs necessary to get there and the passenger air market volatility.

> Some nation state sponsors this as a vanity project. Think Emirates.

UAE is the exact opposite of a nation state.

Probably the wrong word for a monarchy. My point was that vanity gov sponsorship of some sort is required. You’re not going fast because you need to; you’re going fast to flex.

> a vanity project. Think Emirates.

I can't help thinking MBS's Saudi Arabia [1].

[1] https://www.theguardian.com/global-development/2020/may/04/i...

Discussed 2 days ago (155 comments): https://news.ycombinator.com/item?id=32937736

I recently heard that the French have lobbied to prematurely ban this thing from flying over land in Europe as some kind of revenge for the US doing the same to the Concorde back in the day. Anyone else heard anything like that?

Edit: tried googling around and couldn't find anything substantial other than that the US and EU seem to have argued over noise pollution since the 70's.

The EU didn’t exist until 1993.

This article is a bit fallacious/misleading: I have no clue wether Boom design is vaporware or serious engineering but: 1) The initial premise, that there is a costly need to design a new engine is meta-unecessary AKA not necessarily necessary. The article raise 2 reasons for a new engine: fuel efficiency and noise reduction. I'd argue the concorde engine (the Rolls-Royce/Snecma Olympus 593) is excellent regarding efficiency -> > The overall thermal efficiency of the engine in supersonic cruising flight (supercruise) was about 43%, which at the time was the highest figure recorded for any normal thermodynamic machine.[3]

I don't know for sure what is the SOTA efficiency nowadays but IIRC last generations engines are ~10% more fuel efficient than the ones from the 80s, which where at the time behing the Rolls-royce engine hence I even doubt modern engine have better thermal efficiency than aforementioned 43%. Regarding the topic of thermal efficiency, engines are not supposed to reach 43% without being supercritical, did Rolls-royce bypass physics laws? There must be something I ignore here. Anyway even if (?) we could design supercritical jet engines the best possible thermal efficiency would be 46-7% AKA a minor improvement.

Boom can increase fuel efficiency via the airplane architecture with e.g. composites. The near commercialisation new civil aircraft from china achieved a 10% reduction doing so. The same can be said for noise reduction. Hence what Boom should do is simply to order Rolls royce to produce the same engines again. However one should know that R&D for the successor of the concorde engine has already been spent and such engine has been designed. Unfortunately the U.S imperialist oppressive bans killed the concorde economics before the production of said engine, cf: https://en.wikipedia.org/wiki/Rolls-Royce/Snecma_Olympus_593....

Now about the noise levels let's adress the fact that it is a non-issue. 1) If you look at the empirical scientific comparisons, the mean noise of the concorde is significantly lower than many civil airplanes, especially the ones with 4 engines. 2) The boom while intense, is very transient. It is not heard from people inside the airplane. It is a non-problem for the obvious reason that your jet does not need to be supersonic for 100% of the trajectory, therefore a plane can and should go to very high altitude (already a supersonic requirement) and/or above low density population (rural, ocean) and only then bypass the speed of sound, making the noise boom a moot problem. While this solution is trivial, political bans and people hysteria isn't.

What is at stakes? A lot of things, supersonics isn't just cool, it is a life saving technology that can allow the transfer of key people in records time (expert surgeon in niche disease emergency for example) which can have very high utilitaristic value. It can also make it much more pratical for key people to meet physically (e.g. key academicians for a symposium about advancing the state of the art in a topic) which is high impact considering cognitive biases regarding human agency.

Note however there are other supersonic engine makers than rolls royce, for example any country that makes supersonic military jets can obtain such engines. It is easy to forget that the first commercial supersonic engine was not the concorde but a russian tupolev. While the tupolev has reliability issue, few know they had an alternative engine (likely more reliable). In addition to the tupolev engines, I would look into the state of the art https://en.wikipedia.org/wiki/Saturn_AL-31 Regarding SOTA civilian turbofan there is the https://en.wikipedia.org/wiki/Aviadvigatel_PD-14#PD-35 in development, although it can power an antonov (!) and seems very versatile I wonder if (not a turbojet) it can perform supersonicity without afterburners.

regarding those options however, russia bad, china bad.

There are a number of non-starters here:

1. Efficiency counts for a lot in these aircraft, and it's absolutely possible to do better than the Olympus. In particular, high-temperature materials and engineering, along with combustor efficiency have evolved significantly since the Olympus era. Tenths of a percent are a big deal in subsonics, let alone supersonics.

2. Emissions are also a huge deal. Significant work would need to be done to clean up Olympus emissions.

3. Is the Olympus sized properly for the Boom design? Probably not.

4. We don't necessarily publicly know if Rolls offered to refurb and support these engines, but if they didn't, there are some very good reasons. Re-establishing a supply chain for these would be a really big deal, and in some cases not cost-competitive with a from-new design based on present-day supportability.

5. Supersonic boom noise being a non-issue is an absurd premise. It drastically affects your addressable market, period.

6. Time savings for a few critical needs as you cited are not going to be enough economic motivation to develop this system.

7. It's not that "China, Russia bad", it's that Chinese and Russian materials and manufacturing will not currently support the durability requirements for commercial viability of these hypothetical supersonic cruise engines you propose. You would have a lot of off-wing refurb time on such engines. Chinese engines don't have the performance, either.

The case for anything Boom is developing is not really there.

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