No-boom supersonic flights could slide through US skies soon
theregister.com
theregister.com
I now understand that's not the case, but still don't quite know what it is. I think a supersonic aircraft is constantly "dragging" a boom behind it. So when it passes overhead sometime later you'll hear a boom. Is that right? Does that mean you'll see a plane flying overhead, hear the normal drone associated with it, but at one particular moment here a distinctly louder but shorter noise?
And is this a real thing that can be done? How do you make the sonic boom go away? As someone who lives where planes are flying overhead constantly, can it be used to make non-supersonic planes quieter, too?
It’s lightning/thunder: you will be able to see the plane, and then after a bit, hear the boom. You won’t be able to hear other plane noise, all of the combined noise from turbulence and engines is forced back into the boom.
It is shorter duration, yes, but MUCH louder: F-18s at 5000 feet can rattle windows on the ground! Usually not a good trade-off.
Any sound-producing plane generates sound waves, not just a plane that goes faster than sound.
Sonic booms are nothing more than a collapsed wavefront of that wavefront. The speed of sound, definitionally, is the maximal speed at which any physical wavefront can propagate through a medium. (We hear it in air as sound, but no wave can be propagated through the medium any faster than this. You cannot move air any faster than the speed of sound in air.) This causes all of the disturbances from the aircraft moving through the air to be compressed into a single, maximal wave that itself moves at the speed of sound, since it can’t move any faster. Thus the boom.
(You can see a similar cool thing with Cherenkov radiation, where neutrons moving faster than light in water produce a bright blue glow — or, waves of light!)
In physics, an air wave typically refers to a sound wave. While both of your statements are true (plane makes sound-waves at both speeds), they didn't explain the sonic boom, like you did now.
> You cannot move air any faster than the speed of sound in air.
Minor nitpick, doesn't a plane traveling above Mach 1 displace (i.e. move) air faster than the speed of sound in air? :)
Source: this picture from the Boom XB-1 website, which was originally made by Pennsylvania State University: https://boomsupersonic.com/wp-content/uploads/2025/02/xb-1-b...
You can't completely make the sonic boom go away, but you can change how it's experienced on the ground through careful design of the airplane shape. The X-59 Quesst (https://en.wikipedia.org/wiki/Lockheed_Martin_X-59_Quesst#De...) is an experimental supersonic aircraft that reportedly reduces the sound of the sonic boom to something comparable to a 'car door closing', mostly by ensuring that different shockwaves created by different parts of the plane don't combine into a single, stronger boom.
> can it be used to make non-supersonic planes quieter, too?
Sadly no; the principles of design are very different for sonic booms and ordinary plane noise. For ordinary aircraft, the big causes of noise are the engines themselves and turbulence over the airframe.
That being said, the problem of ordinary aircraft noise is usually limited to the areas near an airport. Sonic booms are noticed underneath the entire flight path of a supersonic aircraft, even when it's flying at altitude.
Not really. Supersonic means faster than sound. Meaning that the plane flies faster than the sound. Even its own sound. So you would hear nothing before the sonic boom reaches you. Because the sound didn't have time to get to your ears yet.
> I think a supersonic aircraft is constantly "dragging" a boom behind it.
What was really revealing to me is to look at shadowgraph images of supersonic wind tunnel test. Like this one: https://media.sciencephoto.com/image/s3300054/800wm/S3300054...
You can see the dark airplane looking shape. That's the model of the airplane in the wind tunnel. And then you can see that V shaped shadow edge starting from the tip of the nose. That's the sonic boom. It is a sudden step change in pressure. In this visualisation it appears as two lines, but in reality it is a cone centered on the tip of the nose (or other protrusions.)
Where and when your ear crosses that cone surface that's where you experience a sonic boom.
> How do you make the sonic boom go away?
If I understand it correctly their plan is not to make it not happen, but to fly such that the pressure wave is bent upwards away from the ground. Which sounds like a weather dependent trick. I recommend the video in the article which shows the idea.
So this happens to be rockets. In most plane videos you have sound of other aircraft in the video. This is because people are usually recording at air-shows. It's really hard to find a clean version!
You can't, but you can prevent it from reaching the ground.
> Boom boasts a number of big-name VCs and tech luminaries as funders, including AI poster child Sam Altman
This... can't be a coincidence. Can it?
https://www.nasa.gov/news-release/nasa-lockheed-martin-revea...
"The X-59 is expected to fly at 1.4 times the speed of sound, or 925 mph. Its design, shaping and technologies will allow the aircraft to achieve these speeds while generating a quieter sonic thump."
Further, if the atmospheric conditions aren't right, the cutely named "thump" will turn into a boom again.
I suppose if Qatar gifts Trump the first golden supersonic private jet, it'll also pay fines for "thumps" exceeding the limits.
Nit: eminent not imminent.
As for climate change and oil use, all aviation globally is only about 7% of oil use and about 3% of carbon emissions. It’s not the main thing to worry about.
Coal fired electricity followed by oil fired land transport (mostly easily electrified cars) are together well over 50% of all emissions and are the easiest things to fix. Deforestation and agricultural emissions are also up there. All of these sources are way easier and cheaper to address than decarbonizing aviation.
Thankfully we don't have to stop at one thing. Or even limit ourselves to doing one thing at a time.
Climate change is its own problem. Physics doesn’t care what our gini coefficient is. A more equal society that emits too much carbon still has this problem.
A decarbonized society powered by renewable and nuclear energy could still have too much inequality.
A more equals society would have fewer people in poverty. It would have more active services for people who need them. All that represents a lower entropy state. Lower entropy states require more external energy input to maintain, not less.
Allowing vast numbers of people to rot in squalor while a few rich people live it up is a lower energy higher entropy state.
Individual rich people may use crazy amounts of energy but there are not many of them. Bezos’ jet consumes a tiny fraction of the power required to provide continuous modern health care to everyone, for example.
A much simpler one, that costs nothing, is simply if we did less aviation. If we had the political will, even just trying to get somewhere close to pricing pollution externalities of aviation (in addition to other pollution sources, to be clear), would immediately reduce demand and make other forms of transportation more competitive.
Of course we don’t have that political will, so it may be true that the only choice is to come up with expensive and esoteric technologies to decarbonize aviation. But I think it’s important to acknowledge that flying less was always an option we (collectively) had, but chose not to take.
It’s 3% of world carbon emissions. It’s tiny, it’s pivotal to the economy, and it’s hard to change. It’s the worst thing to fixate on, the one you’ll make the least progress toward.
What we should be fixating on is “end coal” because coal burning, largely for power generation, is both the largest single source and one of the easiest to replace. Yet that climate group is called “end oil” not “end coal.” Why?
If we actually think climate change is a problem we need to think like scientists and engineers and prioritize rationally. We also have to be willing to put politics aside and make a broad and wide appeal, arguing that fixing this is in everyone’s long term interest (because it is).
Only a small amount of aviation is pivotal by any definition, and that portion isn't very price sensitive, so paying for externalities wouldn't make much difference to it.
Even in the richest country in the world, only half of the population took even one plane trip in 2024, and the distribution among those who did, probably skews heavily toward a very small # of frequent fliers.
Aviation is super useful, no doubt. But like many difficult political problems, the benefits are concentrated on those who fly the most, or who consume most of the products that typically fly, and the costs are spread among those who fly the least, or not at all.
Anyway, I have never seen someone advocate to ignore coal in favour of focussing on aviation. But I have seen a lot of people advocate to ignore aviation in favour of focussing on anything but aviation.
As others have said, we can do more than one thing. Some of us can focus on coal, others on aviation. I am just a message board pundit, not involved in coal or aviation, nor advocacy around climate change on either. I am just skeptical of approaches that privilege one pollution source over another. Maybe politics means it's the best we can do, but that's not a very satisfying answer to some of us.
Since the retirement of the Concorde we've regrettably had to use fighter jets for some of these life-saving flights. Sure, rich people subsidized all of it to shave a few hours off their business flights, but given how much avgas Elon's jet uses, it is really more efficient if they half the people who would take a supersonic flight take small private jets instead?
Jets don’t consume avgas.
This sounds like it would check out until you realize that the Concorde operated on only two routes, and not on an ad hoc basis.
This is extremely convenient if you happen to need to get some critical medical supply, which happens to not exist in one of these world capitols, from New York to Paris or London and the timing lines up perfectly with a scheduled Concorde flight. How often do organs go transatlantic anyway? Are there tons of snakebite victims in Paris or London that can only be treated by antivenin stored at JFK?
In any other circumstance, you are almost certainly better off sending a medical jet directly from where the item is to where it needs to go. A business jet going straight from where the donor organ is, to where it needs to go is, in almost any circumstance, going to be faster than waiting for the next scheduled flight going supersonic across the Atlantic, then having to transfer to a completely different subsonic plane for the rest of its journey.
Also, the Concorde had other routes. I don't think those routes were even the first ones. I remember reading about Singapore and the Middle East, but according to this website: http://www.concordesst.com/history/destinations.html it even went to Barbados.
It looks like you can learn plenty more by googling or reading newspaper archives.
It mentions nothing about the Concorde being used for medical deliveries on charter, or at all. Nor have you substantiated using fighters for medical deliveries in its lieu, which was asserted. It also notoriously wasn’t viable for longer flights without refueling, which again, is another logistical and timing issue for medical flight.
The rub with Concorde, or any supersonic jet, is that they are not allowed to operate supersonic over land. That makes it an expensive, fuel hogging, very loud, plane with special runway needs.