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Comment by ctippett | Hacker News Reader

I'm enthusiastic about what Boom are setting out to achieve, but it's my understanding that the technological/engineering challenges to supersonic flight is just one hurdle – the other being the geopolitical issues that arise from negotiating flight paths over various country's air space.

The economics of the Concorde were significantly impacted when India prohibited Singapore Airlines / British Airways from flying over Indian airspace[1].

[1] https://www.heritageconcorde.com/singapore-airlines-concorde...

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> other being the geopolitical issues that arise from negotiating flight paths over various country's air space

Overture targets ICAO Stage 5 noise levels, the most stringent international noise standard [1].

[1] https://hmmh.com/resources/news-insights/blog/stage-5-aircra...

This is a lie. They write "Overture’s takeoffs will blend in with existing long-haul fleets, resulting in a quieter experience for both passengers and airport communities, meeting or exceeding ICAO (International Civil Aviation Organization) requirements for all subsonic aircraft operating over land and at or near airports."

Note that they are talking about takeoffs (and presumably landings) only where there isn't any sonic boom anyway, not cruising.

> This is a lie

Hell of a claim with zero evidence. By your logic, I could disprove the Sun by not observing it at night.

Yes, the ICAO rules are for takeoff and landing. When subsonic planes are the loudest. Concorde, for example, couldn’t have met these requirements.

We don’t know what Boom are targeting for in-flight noise. But we can guess, based on its parity with ICAO take-off and landing requirements, that it aims to match subsonic noise levels on the ground. There is strong evidence we can soften and disperse a high-altitude boom [1]. Whether it’s doable by Boom is an open question.

So no, it’s not a lie.

[1] https://www.nasa.gov/centers-and-facilities/langley/nasas-su...

What? I cited their own document to show that your claim was not about the sonic-boom noise (which is what people are worried about). You say yourself "we don’t know what Boom are targeting for in-flight noise".

What do you mean about "its parity with ICAO take-off and landing requirements"?

Appreciate the reference, I wasn't familiar with the ICAO noise standards.

If I'm reading things correctly it looks like Stage 5 caps out at 50dB, whereas a cursory search on the decibel levels for a supersonic boom comes up with 110dB.

That seems like a pretty large divide! Am I missing something?

Edit: A sibling comment appears to have addressed my confusion.

My understanding is that Boom is planning to implement technology that prevents sonic booms as we think of them.

IIRC their goal is to deflect it upwards with their wing and fuselage design.

> cursory search on the decibel levels for a supersonic boom comes up with 110dB

Short answer is we aren’t able to predict how loud a sonic boom will be [1]. Raw decibels produced at source is one thing. But you also have components like direction, dispersion (spatially as well as temporally) and frequency and how altitude and even moisture effect all that.

We’re making progress [2]. But the conventional wisdom is you need a perceived loudness on the ground that matches subsonic airliners to have a hope in hell of FAA approval. (Would note that a sonic boom in this context is not a physical phenomenon but summary of perceptions. There will always be an acoustic reaction to supersonic flight. But the far field effects that characterise a “boom” aren’t inherent to supersonic flight.)

[1] https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1...

[2] https://www.sciencedirect.com/science/article/pii/S037604212...

Boom is trying to build their own engine for the full size aircraft. That's tough. The number of groups that have built a reliable high-performance jet engine is very small. China still has trouble doing it.

The XB-1, the 1/3 scale model, uses standard General Electric J85 engines.[1] Old, reliable, not too expensive, and used by many prototypes over many decades.

[1] https://en.wikipedia.org/wiki/General_Electric_J85

> Boom is trying to build their own engine for the full size aircraft. That's tough

It echoes my criticism of Virgin Galactic checks notes ten years ago.

That said, Boom started dancing with the DoD in ‘22. That’s a deep pot of cash, and could help make up for inexperience.

Surely there is somebody with enough brains in the Pentagon to diversify their supplier base away from the moribund Boeing-esque incumbents, right? If they haven't learnt this lesson post-SpaceX, when are they going to figure it out?

A couple billion bucks is pocket change to the DoD, they literally "lose" it in their couch cushions, and it could eventually be the difference between "viable domestic defense aerospace industry" and "buy threaded steel nuts for $9000 each, with an 18 month lead time and 5000 pages of paperwork."

> Boom is trying to build their own engine for the full size aircraft.

Hahahaha. No.

That China still has trouble is one thing. The fact that Russia also has issues, with around 80 years of experience, tells you everything you need to know about how non trivial the task is.

Then again, SpaceX managed to pull their thing off, using modern tooling and some of the world's best rocket engineering teams. Russia and China, with all of their expertise don't have SpaceX's capabilities either. Supersonic jet engineering isn't exactly the same thing as rocket engineering, but they're related.

Good thing the oceans don’t care. The most viable routes are mostly oceanic. LA-Singapore could be done mostly supersonic and then slowed down once closer.

Not that I disagree with you, but I'd argue the most viable route would be one the Concorde already served: New York to London over the North Atlantic.

Market enviornments change though. There's probably a lot more people with disposable income in the higher end and plane travel has exploded since then. But gov controls and red tape on this sort of thing probably tripled, especially around environment/airport development+nimby politics/aircraft regulations, so it's probably 50/50 vs the 1970s-80s.

I eagerly awaiting saving 500,000 Amex points and having a chance to fly supersonic.

That's less true now than it was in the 1980s.

Concorde got a pass because it was British and even then it was controversial.

Boom will still have to meet all noise pollution rules now and in the future. Noise rules are designed for normal passenger aircraft, they will not get any exceptions.

I don't doubt that they can make something much quieter than Concorde but can they make it as quiet as subsonic aircraft?

Sure, but Concorde was hella loud even in subsonic regime.

I grew up in Cedarhurst, NY, 3 miles from Kennedy Airport. The Concorde at subsonic speeds was very loud. It was a loud, window-rattling rumble. But the worst of all were the 707s. They _screamed_. If I was outside when one went over Runway 31R/13L, I'd have to cover my ears.

Yes, back in the 80s I could hear aeroplanes fly over. Nowadays they're far too quiet to hear.

In the meantime we got 9/11, and all the security procedures that goes with it. It is nowadays much slower to fly than before, and that time is mostly incompressible, making the benefits of supersonic flight less incentive.

I fly a fair amount, and I haven't been in a situation where I had to arrive at the airport 90 minutes before a flight in years - typically 1 hour is plenty of time, and if I weren't optimizing for low-stress, could get away with 45 minutes most days for domestic flights.

90 minutes out of 17.5 hours of travel ( 16 hour flight from SFO to Singapore) represents a small amount of 'incompressible' time - cutting that 16 hour flight down to 8 or 10 would make a HUGE difference, especially given timezone/IDL issues.

Air Canada just announced today it's inreasing check-in cutoff time to 1hr - roughly meaning if you don't get to the counter at least 1hr early you're out of luck.

Not sure if it impacts those who travel without luggage and check-in online.

I contrast this to when I used to be able to (long ago) roll up to the airport a mere 20mins before takeoff time.

>I used to be able to (long ago) roll up to the airport a mere 20mins before takeoff time.

I worked for a guy once when I was working in downtown Boston for a bit and the times I traveled with him he would absolutely drive me crazy by not wanting to grab a cab to the airport until well under an hour before flight time.

Today, I usually breeze through security in a few minutes with TSA Pre for early morning flights. I still arrive about 2 hours in advance because I find it more relaxing and my limo company pretty much wants that much slack anyway. (I rarely check luggage.)

> Not sure if it impacts those who travel without luggage and check-in online.

If you checked in online and have no luggage, you just need to make in time before your boarding gate closes.

Boom Overture, which does not yet exist, is supposed to have a range of 4,250 nm (presuming they can get their engines to actually exist, which is a giant question-mark). That means they can bring JFK-FRA into service, but SFO-SIN is going to be tight even on just one refueling stop (7340 nm but the jet stream is working against you the entire way- sometimes it will require a second refueling stop!).

There are a few airports (like MCO [Orlando’s commercial airport]) where I do try to give myself 90 minutes, but for most of my trips, I leave my house about 60 minutes before boarding and get to the airport about 20-30 before boarding.

Supersonic uses a lot more fuel. It's highly unlikely LA - Singapore can be done on a single tank. Adding a stop for refueling negates much of the time benefit.

A lot of these regulations are regulation on speed not noise. I expect some governments will be amenable to changing their speed restrictions to decibel restrictions (which Boom claims they can comply with).

If not, there's always trans-oceanic flights.

Well the second one isn't really their hurdle. Its up to the airlines and governments to squabble with each other on flight routing.

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