> A dual-mode ramjet was developed and tested in less than 11 months
Incredibly impressive if true. But below quote makes it sounds like they purchased a company with mostly ready design and made a prototype. Still pretty awesome.
> The successful development and testing of the dual-mode ramjet in such a short period of time was made possible through the collaboration of GE Aerospace’s team of engineers, Innoveering – a company acquired by GE Aerospace in 2022 that specializes in hypersonic propulsion – and GE Aerospace’s Research Center.
Now I want real engineering / everyday astronaut like breakdown of how it works.
> Incredibly impressive if true. But below quote makes it sounds like they purchased a company with mostly ready design and made a prototype. Still pretty awesome.
We're probably reading a lot from a few sentences but I had a similar impression. Probably more similar to writing a software project for the second time after you throw away your first version - but now with more resources. Like you said still pretty cool.
>more similar to writing a software project for the second time after you throw away your first version - but now with more resources
All aircraft design is basically this. You don't/can't ever really start from scratch, there's an enormous volume of historical aircraft designs and all new planes look very similar to old planes. There are very rarely opportunities to solve problems in new ways.
even if you have a novel design your customers are rarely interested.
Airlines are extremely conservative because pilots are expensive and hard to train, which is how we got the whole 737MAX fiasco instead of a clean-sheet, optimized design. Though i wonder why they didn't go for commonality with the 787 similar to how the a330 and a350 are common type ratings.
The problem Boeing had was that there is a massive amount of 737:s, and a correspondingly massive pool of crew qualified for those planes. Customers really wanted not just a plane that was compatible with something, but specifically compatible with the 737. And this was a problem because the 737 is too old of a design.
If Boeing attempted to sell these customers a new type, even if there is some compatibility with some other plane, it creates an opportunity for them to freely compete bids between Airbus and Boeing, and even when Boeing wins that bid, it's a loss to them. (Because they are going to win at a lower price point than if the customer has to account for the switchover cost only for Airbus planes.)
When companies reach a certain size they basically become banks, either funding smaller teams under their umbrella to do things or purchasing and integrating them into a larger portfolio.
If they purchased the design it's because GE Aerospace has the manufacturing and sales arms to actually make it real.
i for one look forward to experiencing this next generation of ramjet technology firsthand in my next three-star motel room air conditioner, the most common and widespread use of ramjet technology in the United States today.
I just got a new battery-powered air duster that says "TURBO FAN" on the side. It's about 100,000 horsepower short of an actual turbo fan, but it's a good duster and I enjoy the enthusiasm.
If this is a joke about GE's appliances -- that version of GE is long in the past. GE has pretty much been dismantled and is just an aerospace company at this point.
What was once GE Appliances was sold to Haier 8 years ago.
Per the above in 2019 they had been developing RDE technology for 5 years.
Now developing the tech is different then building a prototype but it's good to take these timetable numbers with a large dose of salt.
It is interesting to see RDE's getting alot of headlines recently. Really cool tech that works off of a principle known for a long time but only just recently hitting an inflection point in terms of development.
I’ve been saying this for years, but I’m extremely skeptical the DARPA hypersonic programs just ceased.
The waverider program was a huge success, then suddenly funding stops and nothing is heard about it anymore. That was over 10 years ago, and now we have a commercially-developed dual cycle engine in under a year.
It’s my personal opinion that the technology was developed further internally for weapons and surveillance platforms like the SR-71 was back in the day. The technology just has too much potential.
Supersonic has been DoA for a while because post-deregulation airlines are only interested in ever more fuel efficient aircraft. (It’s also why major states like Japan, China and Russia have for the most part failed to build a competitive airliner against the duopoly.)
>It’s also why major states like Japan, China and Russia have for the most part failed to build a competitive airliner against the duopoly.
I don't think that has anything to do with it at all. Building a competitive large airliner requires a huge industrial base. And since it's so safety-critical, it takes a lot of time and expertise to build the reputation needed to unseat the incumbents. China has an aircraft manufacturer, but time will tell if it goes anywhere, since they don't exactly have a reputation for high quality. Russia has built many large aircraft in their Soviet days, but their industrial base has eroded so they probably just don't have the capacity to build competitively-priced aircraft in volume now, plus they're not well-liked by most countries that would want airliners anyway. Japan might be able to do it, but just isn't geared up for building lots of large aircraft so it would be a huge investment to build such an industry almost from scratch.
Fuel efficiency isn't a factor because building an airliner doesn't involve building engines for that airliner, and engines determine an aircraft's fuel economy for the most part. Boeing and Airbus don't make jet engines: those are all made by Rolls-Royce, Pratt & Whitney, and GE.
> Russia has built many large aircraft in their Soviet days, but their industrial base has eroded so they probably just don't have the capacity to build competitively-priced aircraft in volume now, plus they're not well-liked by most countries that would want airliners anyway
Russia did design and build a few designs recently - SSJ-100, MS-21, Tu-204/214. Almost all of them used Western parts (such as engines/avionics) to speed the process up because Russian manufacturers are a few decades behind in some critical parts (like engine efficiency). That being said, they're currently trying to ramp up production on a domestic only Tu-204/214 version, but it's slow, probably quite expensive, and super inefficient.
> Japan might be able to do it, but just isn't geared up for building lots of large aircraft so it would be a huge investment to build such an industry almost from scratch.
Mitsubishi had a regional jet design in progress, the SpaceJet, which got cancelled after a few billion in R&D and years in delays.
Ukraine also had decent manufacturing facilities and capabilities with Antonov and Motor Sich, including decent recent designs and subcontracting work for other companies.. but with the war a lot of things were destroyed (like Antonov and Motor Sich factories and facilities), and their focus is mostly on drones and missiles now.
> Fuel efficiency isn't a factor because building an airliner doesn't involve building engines for that airliner, and engines determine an aircraft's fuel economy for the most part. Boeing and Airbus don't make jet engines: those are all made by Rolls-Royce, Pratt & Whitney, and GE.
Fuel efficiency is a major factor. Outside of countries big enough to prop up a domestic airliner industry with enough spare cash to compensate for inefficiency (which is a list of 1 country, China), nobody will buy a jet which is less efficient than an alternative. Airline margins are razor thin.
And not everyone can buy an engine from Rolls-Royce, GE/CFM(their joint venture with Safran that designs manufactures short-haul engines and the future open fan design) and Pratt and Whitney. The Russian UAC cannot. The Chinese COMAC got sold a decade+ old variant for their latest jet out of fear of industrial espionage (the Chinese engine manufacturers have failed at producing reliable and efficient jet engines for any application, usually relying on Russian designs).
TL;DR is that modern airliners are extremely complicated, expensive, and have very long lead times. A new design won't be making any money within the first 10-15 years of its life, which means that only countries with very developed and advanced industrial bases, lots of money, and the desire for strategic airliner autonomy will invest in them.
>Fuel efficiency is a major factor. Outside of countries big enough to prop up a domestic airliner industry with enough spare cash to compensate for inefficiency (which is a list of 1 country, China), nobody will buy a jet which is less efficient than an alternative.
No, it's not really a factor, because, as I wrote before: airliner manufacturers don't make jet engines. They can only get engine manufacturers to build them engines, and integrate those into their airframe designs. Of course, actually having access to modern, efficient engines is necessary to be competitive, which as you point out is problematic for Russia and China, but if, for instance, a major Japanese company decided to suddenly get into the jumbo-jet business, this shouldn't be an issue for them, provided the existing engine manufacturers have enough manufacturing capacity to provide them engines in addition to those they provide to Airbus/Boeing. So yes, being fuel-efficient is important to the end customers (passenger airline companies), but for the airframe makers, that's really determined by the engines they have access to, not really by any technical capabilities of the aircraft makers. The problem with lack of supply in large passenger jets isn't the engines (AFAIK), it's really just the Boeing/Airbus duopoly and how quickly they can build new aircraft, which use the engines from those suppliers.
> company decided to suddenly get into the jumbo-jet business, this shouldn't be an issue for them
I don't think it's that simple. You can count jumbo jet makers and their engine suppliers on one hand. It's not like you can go shop for a new line of engines on Craigslist, these things are designed with the plane maker in mind and production numbers planned for a decade+ ahead. Both parties have to work very closely together to produce something with acceptable fuel efficiency.
the major engine OEMs aren't investing enormous amounts in optimising for a startup airframe program though, so at best you're getting a derivative of the engine on the equivalent sized Boeing/Airbus program with roughly the same fuel efficiency but worse expectations in every other relevant area (expected reliability, competitive local maintenance markets, type-rated crew availability, commonality with existing fleet, residual values etc, and probably worse aerodynamics and structural weight) due to the airframe program's relative immaturity
The most fuel-efficient aircraft possible would be an electric one (for the sake of argument lets assume batteries of high enough Wh / kg would exist) flying at much higher altitudes (20km+) than the current fuel and oxygen fired engines.
That definitely involves both engine and aircraft design.
Even for jet engines: an engine from the 50's is not going to cut it in terms of fuel efficiency on ANY airframe compared to current flying machines. Even if you had unlimited budget and time to design the perfect airframe for those engines.
> (for the sake of argument lets assume batteries of high enough Wh / kg would exist)
Highly unlikely, it's not even close right now, and nothing in recent progress indicates that soon we might have batteries that are denser and lighter by a factor of 10 any time soon.
At this point the 737 Max 8 and A320 both are sitting around an 18:1 L/D. You can't really go a whole lot higher than that without affecting controllability. Things like winglets give you incremental improvements on the order of single digit percentages.
But weight savings... that's huge. For every pound you shave off, all other things equal, means the engine needs to make less thrust and the aircraft itself needs to carry less fuel.
Both China and Russia are building alternatives to Boeing/Airbus commercial airliners. But are in two completely different situations.
COMAC relies on international suppliers, probably hoping that will make it easier for them to be allowed to fly outside China and then over time they can use more and more domestic suppliers. Whereas the Russians are completely cut off from international suppliers and travel, and have to resurrect their airliner projects which have been more or less dormant since the Soviet times.
I think both will be succesful over time; they have huge internal markets that can sponsor quite a bit of development cost.
The reason they dipped in terms of planes is directly related to sanctions and western countries pulling out based on the article you shared. Worth noting, the foreign parts Sukhoi Superjet 100 (a very good regional jet) are in the process of being fully "Russified" and the MC-21 is actually a true domestic plane vs the Chinese C-919:
Also, Russia just surpassed Japan to become #4 in terms of GDP PPP (the number that matters), was recently reclassified as a high-income county and is expected to experience relatively high GDP growth, and that's even under the heaviest sanction regime on the planet x3 and after getting cut off from SWIFT:
> Worth noting, the foreign parts Sukhoi Superjet 100 (a very good regional jet)
A very good based on what measurement? Operators have complained about extremely poor reliability, and there have been a high amount of crashes.
> and the MC-21 is actually a true domestic plane vs the Chinese C-919:
The MS-21 isn't domestic, it uses Western avionics and engines. There's a russified version which is supposed to be launched in 2025-2026, but it's unknown if that would happen considering it's using the Aviadvigatel PD-14 engines which are still undergoing design refinement and testing. It could literally be years before the engines are ready, so when the jet enters service is anyone's guess.
> Also, Russia just surpassed Japan to become #4 in terms of GDP PPP (the number that matters), was recently reclassified as a high-income county and is expected to experience relatively high GDP growth, and that's even under the heaviest sanction regime on the planet x3 and after getting cut off from SWIFT:
A big issue with these metrics is that they use the official exchange rate for RUB to USD exchange rate, which is entirely theoretical since it's impossible to trade the two due to the sanctions. The real exchange rate is probably much worse for the RUB, so these metrics based on the official theoretical one are highly misleading.
> Also, Russia just surpassed Japan to become #4 in terms of GDP PPP (the number that matters), was recently reclassified as a high-income county and is expected to experience relatively high GDP growth,
You can get a lot of GDP growth if you focus your entire economy on making war materiel. It's not exactly durable growth and it doesn't really increase your citizens' quality of life.
Russia's industrial development outside of refurbishing Soviet stockpiles for war is extremely limited. Ditto for its civilian development: come on, 20% of citizens are still waiting for indoor plumbing.
GDP PPP is a useful number in comparing relatively-like economies, but here it breaks down completely.
GDP is sort of a nonsense metric for "ability to get things done". A huge portion of that GDP are things like rents extracted via intellectual property so it doesn't tell you anything about ability to manufacture anything.
Example: California woman sends her kids to daycare a few weeks after birth and goes back to her job (high GDP), Russian woman stays home with her children (no GDP). Now wait 50 years until you only have neglected iPad kids raised by busy parents left, how many planes you building now? And the ones you manage to build? Maybe they start falling out the sky, doors coming off the hinges, that sort of thing. Maybe the engineers don't have enough of a backbone to stand up to their boss because they never really experienced secure attachment, and some people die.
The economy is growing because of massive government expenditures on defense. The same thing happened with Nazi Germany. It's not sustainable.
"Buoyant commodity prices" is also known as inflation. They have high inflation despite having a federal interest rate of 18%, which is sky high. Not great signs for their economy.
Not at the same scale. At the peak of the Vietnam War, the US spent less than 10% of GDP on the war. Most of the time it was only half of that (for comparison it’s less than 3% at the moment).
Russia currently spend about 40% of the GDP on Ukraine war ( coming off my memory, may not be 100% accurate). That can’t be sustainable and they will have long lasting impact.
Why would they need to borrow when they can continue to sell commodities (which the EU and US continue to buy, btw)? Besides, there's no indication that they are running out of reserves. Wasn't one of Putins first moves to get off of foreign debt?
They’re going to have a hard time exporting oil and gas if Ukraine keeps attacking their refineries. Repairing those refineries requires equipment that Russia has a hard time getting thanks to sanctions.
Those commodities won't even come close to covering their spending spree. And their reserves are running dry very quickly. Likely by the end of this year.
The Ukrainian aircraft industry was indeed interesting, but it was all about cargo planes. An-225 was a magnificent device, but it could not serve as an airliner. Neither could An-124. BTW both were designed back in the USSR times.
> The Ukrainian aircraft industry was indeed interesting, but it was all about cargo planes
Not exclusively, they had the An-148/158 regional civilian airliners (and related An-178 military cargo jet). They definitely had catching up to do (the An-148/158 didn't perform really well, in large part due to issues with the supply chain which was part Ukrainian, part Russian, and the war(s) between the two complicated things a lot), but there was a good base on which to build.
> I wonder where Embraer fits in your picture.
They're the only ones that can do it, but probably won't because they don't have the capital and there's the example of Bombardier which bankrupted themselves trying to make a new short to medium haul airliner.
Wasn’t bombardiers failure the result of Boeing playing dirty and pulling political strings? The commerce department imposed tariffs that quadrupled the price of the plane.
I mean, Bombardier was selling the planes below cost, which is the technical definition of dumping.
Part of why they had to do it is because they had so many testing issues and delays with their new design that people were not willing to bite the bullet on an unproven design.
> I mean, Bombardier was selling the planes below cost, which is the technical definition of dumping
Nope, it's not unheard of in aviation because a plane, or an engine, has a multi-decade life, over which there will be a lot of maintenance and spare parts needed.
GE and Rolls-Royce used to sell jet engines at a loss, banking on maintenance and spare parts making up the losses.
And of course, the punitive tariffs were later removed because Boeing weren't actually impacted by the C-series, dumping or not.
> A new design won't be making any money within the first 10-15 years of its life, which means that only countries with very developed and advanced industrial bases, lots of money, and the desire for strategic airliner autonomy will invest in them
And to add to that, the desire for strategic airliner autonomy tends to be inversely proportional to domestic companies' chances of non-trivial international sales. There will be a few airlines and lessors that passed on the Russian SSJ-100 out of longstanding concerns about Russian supply chains (even though it had an Italian marketing JV so you didn't necessarily have to deal with them directly) that will be patting themselves on the back for making the correct decision, and presumably the Russian state picked up the tab for all the losses Sukhoi made on the programme.
Tbf that one was counted as pilot error IIRC, but never a good idea to kill your customers. The few non Russosphere SSJ customers pretty much all going bust except for CityJet who dropped them from their fleet citing reliability issues probably didn't help either
They are now being built again, because it's the only design that wasn't built with the assumption that Western providers (of avionics, specialised parts, engines) will be available and therefore it's the easiest one to manufacture with an entirely Russian supply chain. Still painful because most of that supply chain is decades old and very rusty, but theoretically possible.
Airbus is heavily depending Russian titanium. Even with the current tensions they decided to keep buying Titanium from Russia. Money is the only reason why players are not having inhouse solutions. Give it time and reason and any country can get a fuel efficient engine.
It takes an insane amount of expertise and endurance testing to produce a safe, reliable jet engine. These companies have been doing so for 60+ years at this point. There’s a lot of knowledge and investment that has allowed them to produce these things at any kind of scale at this point.
I used to work at Pratt & Whitney, and trust me a LOT goes into this. We also worked with some of the Rolls-Royce guys. There’s a reason Boeing and others don’t even attempt it.
This was a century ago, when aircraft engines were radial ones with propellers, and weren't all that different or complex than truck or tank engines (outside of layout and materials for weight optimisation).
Modern jet engines are technological marvels of engineering with extreme complexity. And there are massive advancements like turbojets, turbofans, high bypass turbofans, geared turbofans, open fan every few decades.
Any engine manufacturer from the 1930s could and did manufacturer plane engines. Nowadays it's so complex and capital intensive there are 3.5-4 companies remaining with modern efficient designs.
It's a hypersonic thruster, i.e. 5 or more times the speed of sound. Far too fast for civil aviation. It's probably even too fast for "safe" manned flight. This is the speed at which the air ionizes around the vehicle. It's like flying inside a fireball.
The first use that comes to mind is a hypersonic cruise missile or unmanned bomber.
Intercontinental missiles are also hypersonic, but their re-entry vehicles are gliders with limited maneuvering capabilities.
The Russians have developed and used hypersonic air-to-ground missiles in Ukraine, the Kinzhal. It is very difficult to intercept a missile at these speeds, and almost impossible if the missile is maneuverable.
This has re-launched research into this type of missile and propulsion system.
Russia is ahead in this field. The USA, China and France have carried out various experiments (mach 5 to 25), but do not really have combat-ready hypersonic weapons.
One of the great difficulties of hypersonic flight is that you generally need one engine and one stage per flight regime. The majority of demonstrators operate according to the following scheme:
- a rocket or aircraft propels the vehicle to supersonic speed, so that it can start its engine.
- The vehicle accelerates to Mach 5. The vehicle starts its hypersonic engine and detaches from the supersonic stage.
- Climb to the edge of space.
- Descent and acceleration.
- Detachment from the hypersonic engine and final gliding approach. The fireball moving off at mach 20 kind of approch.
The engine shown here would enable to have just one engine for supersonic and hypersonic flight, greatly simplifying the vehicle.
The fact that it's an engine and not a rocket is important, as it means that the thrust is much longer and can potentially last for the whole flight. At these speeds, it's largely the engine's thrust that makes maneuvering possible, and this is what distinguishes these vehicles from the hypersonic glider/reentry vehicle found on intercontinental missiles.
If you define "hypersonic weapon" as merely traveling at or beyond Mach 5, then practically every medium range ballistic missile since the V-2 qualifies. There is nothing special about a missile that can hit hypersonic speeds.
The real difference is maneuvering, but most of Russia's "hypersonic weapons" cannot actually do this. Hence why Ukraine has shot down nearly every Khinzal that has been fired at Kyiv and about half of the Zircon missiles too, using technology that has existed for decades. IIRC one of the Khinzal missiles was even knocked out by a PAC-2 missile, which wasn't designed for that purpose.
Maybe AvanGuard is more competent and less overrated/overhyped than their other efforts, but there's no particularly good reason to believe that. Meanwhile the last time the US successfully tested a hypersonic weapon it was immediately greenlit for serial production, and I don't think that's because they are freaking out so much as that the US sandbags our capabilities while some of our competitors inflate theirs. You claim the Russians are ahead, but they keep putting their hypersonic engine researchers in jail. I don't buy it.
> The Russians have developed and used hypersonic air-to-ground missiles in Ukraine, the Kinzhal. It is very difficult to intercept a missile at these speeds, and almost impossible if the missile is maneuverable.
Speed does not make hypersonic missiles difficult to intercept. They are considerably less maneuverable than slower missiles due to the limits of material physics. The primary advantage of hypersonic weapons is that it reduces the available reaction time of the target such they may not be able to respond effectively or mount a defense. Any "difficulty of intercept" is predicated on there not being enough time to execute the intercept after the missile is detected. US air defense systems have very low reaction latencies by design, as demonstrated in Ukraine.
I am unclear why anyone thinks Russia is ahead in this field, beyond their penchant for marketing ballistic missiles like Kinzhal as "hypersonic". The US has been building and testing hypersonic weapon systems longer than most people have been alive. Unlike Russia, the US requires hypersonic missiles to have precision terminal guidance, which is an extremely difficult engineering problem within the atmosphere. It took decades for the US to figure out how to reliably deliver terminal guidance for hypersonics.
> It's a hypersonic thruster, i.e. 5 or more times the speed of sound. Far too fast for civil aviation. It's probably even too fast for "safe" manned flight. This is the speed at which the air ionizes around the vehicle. It's like flying inside a fireball.
Ionization occurs at considerably higher temperature.
The hypersonic regime is described as when vibrational excitations of air molecules begin to significantly affect the specific heat. After that, dissociation sets in, and only after that does ionization become significant. Temperature ranges, as I understand it, are (for air at 1 bar):
Vibrational excitations: > 800 K
Dissociation of oxygen: > 2500 K (nearly complete ~4000 K)
Dissociation of nitrogen: > 4000 K (nearly complete ~9000 K)
Ionization: > 9000 K
Lower pressure will reduce the temperatures at which dissociation and ionization become significant.
Kinzhal isn’t really a true hypersonic weapon. They just strapped an iskander tbm to a su34, which is why the pac3 patriot interceptors can actually shoot them down, they were developed to intercept tbms.
well you still get the marginal benefit of having a mobile launch platform that travels at mach 1, which makes it a bit easier to avoid static air defenses if you know where they are. (assuming your adversary can't track and destroy your aircraft before they get a chance to launch them)
This is hypersonic. Way faster, way more heat just from moving through air. We will not see passenger aircraft going hypersonic for a long time. It will be hard enough to make a hypersonic aircraft that doesn’t melt itself during flight.
The main reason supersonic flight is dead is the sonic boom. Until that issue is resolved they are banned over land, unfortunately.
| The main reason supersonic flight is dead is the sonic boom
Is it? The Concorde would fly at subsonic speeds over land and move to supersonic over the Atlantic. Given the reduced flight time at supersonic speeds I thought economic considerations prevailed.
The sonic boom made Concorde's economics harder, but they'd have been hard anyway. It confined it to largely only being useful for that transatlantic route, and that was borderline economically viable for airlines. However, as there was really only one route where it was useful, there were not many Concordes flying and the fixed costs were considerable. Eventually Airbus pulled the plug, and ended maintenance, and that was the end of that. It was probably spurred on by a high-profile disaster, but even without that, the writing was on the wall; if you were an airline Concorde looked economically viable, but without subsidy by the state or by Airbus or both, it never had been.
In a world where there had been many viable Concorde routes, this could all have worked out a lot differently, Concorde B might have happened (which would have allowed a Pacific crossing), and maybe we'd still see supersonic airliners.
Even without the sonic boom, it was painfully loud on takeoff and final approach. It used to fly over us near Heathrow and the ground would shake as it went over at a few thousand feet.
Concorde B allowed a Pacific crossing in a technical sense, if you did a technical stop in Anchorage or Honolulu. And then only to Japan, but not to Korea or China.
In the 90s and 2000s you would have had 747s and a340s doing that nonstop without Anchorage or Honolulu, so if anything that would have made concorde B have an even shorter shelf life.
> Didn't the SR71 fly between LA and NY at above supersonic speeds? Don't military jets fly at supersonic speeds above land?
I think not routinely in either case? Most supersonic aircraft can't actually sustain supersonic speeds for a significant period; the Concorde and Tu-144 are, as far as I know, the only aircraft ever designed with supersonic flight as the effective _default_ mode of operation. For both planes, _getting_ to supersonic was rather expensive, and required the use of afterburners, so an ideal flight profile would involve ramping up to supersonic once, and then staying that way for the rest of the flight.
The SR71 was, unusually, _capable_ of sustained long-range supersonic flight, but I can't imagine it was routinely used above land when not actually on missions; why would it be?
> The SR71 was, unusually, _capable_ of sustained long-range supersonic flight, but I can't imagine it was routinely used above land when not actually on missions; why would it be?
Everything a military plane does is a mission, and the SR-71 absolutely did supersonic training missions over the US.
And as I understand, the military can and still does do supersonic training missions over land, but they do it at higher altitudes and in locations where it isn't disruptive to population centers.
_Can_, but does it routinely outside of training/deployment situations? Like if you're just moving one from one side of the US to the other, you're probably going subsonic.
> Don't military jets fly at supersonic speeds above land?
It can happen, but it is disruptive at best. It isn't something you'd want happening around a populated area on a routine basis in peacetime. And it typically is not, unless under emergency circumstances.
Thd only time I've ever heard a sonic boom was as a kid, on holiday in the south of France. They would regularly fly Mirage jets over the beach resorts. I suspect these flights were for when Gen. de Gaulle was in residence at the Chateau d'If.
>The sonic boom made Concorde's economics harder...
I live in south-east Canada in the province of PEI and I hope no supersonic aircraft are made. Right now all commercial air traffic from NA flies right over my house. Especially every evening the rumble of high flying jets can he heard. It's not loud but it's certainly noticeable for something 10,000m above me.
It's a little more complicated then that. The main impetus for the development of the Concorde was actually fuel efficiency - once you get high enough above the sound barrier supersonic flight is more fuel efficient than subsonic flight, all else being equal. Back in the 50s, as fuel costs became more and more of a concern for airlines, this seemed like the obvious future: you get your passengers to their destinations faster, you spend less on fuel, and you can make more flights per day. So Super Sonic Transports (SSTs) looked great on paper. SSTs need to use turbojet engines, which all passenger jets in the 50s were using anyways.
But shortly after Concorde's design was locked in high bypass turbofan engines were developed whose fuel efficiency was way higher than turbojets, and indeed much higher than the jump to supersonic flight could achieve. Now it was a choice between speed and fuel efficiency. This really could have gone either way, but when Boeing got out of the SST game they lobbied for overland supersonic flight to be restricted because of sonic booms, which eliminated the potential domestic market. Concorde was reduced from the future of air travel to an offshoot for a niche market.
Still it was profitable. People were willing to pay a premium for faster travel, it just wasn't a big enough success to warrant further development. The aircraft aged, unable to take advantage of many of the improvements that came to subsonic jets, and there was no replacement in sight. The Concorde was increasingly expensive to operate compared to more modern aircraft, not because of fuel but because of maintenance and staffing. Between a high profile Concorde crash in 2000, then the reduction in aircraft travel after 9/11, and the security increases which essentially tacked on 2 hours to every trip by air, the Concorde ceased to be viable.
Green and nimby bullshit as usual.
I lived at a summer home in 80s which was near a (soviet) air force base for many summers, and listened to sonic booms daily. In no way it was even disturbing.
Supersonic has also been dead because passenger supersonic flight is banned over the continental US (and probably similar restrictions exist in Europe). In the US the regulations will be getting reviewed depending on the results of studies on building supersonic jets that make less noise (after which it'd be down to if they can be made efficient enough to be profitable).
You don't need to make an airliner. There are enough billionaires in the world to support a small industry of supersonic private jets. All of the marketing hype about supersonic for the masses is a figleaf to avoid being pilloried over tech that only serves the ultra wealthy.
We speak of hypersonic flight when we approach or exceed Mach 5. At this speed, the heat is such that the ionized air forms a plasma around the vehicle. To put it simply, you're flying in the middle of a white hot blowtorch.
This dramatically alters flight characteristics. Some prototypes approach or exceed mach 20. At this speed you're closer to a meteorite burning up in the atmosphere than to any form of aircraft.
This distinction is important, but in the contexts of this engine, hypersonic is important because it roughly aligns with a performance boundary for conventional ramjets.
In a conventional ramjet, you basically have some static/static-ish structures in your inlet that uh.... "rams" into the air. This entire structure slows down the supersonic airflow to subsonic speed, and causes the pressure/temperature of the air to rise to allow for combustion.
The problem is that ramjets become less and less efficient and feasible as Mach number increases, and around Mach 6 (so technically past the hypersonic boundary), you basically can't push them any harder, and so you need a supersonic ramjet (scramjet).
In a scramjet, you only slow down the airflow to low supersonic speeds (instead of all the way to subsonic), and you feed that compressed supersonic flow into your combustion chamber.
I believe expectation for scramjets in general is that you'd only really get to Mach 10-12 or so, since above that speed rockets start providing more favorable performance.
The reason one cannot push the ramjet any higher is the air, slowed to subsonic speed, is simply too hot. If it's sufficiently hot the materials of the engine cannot withstand it, and even combustion stops being effective (because the temperature drives reactions in reverse, preventing heat production.)
These lecture notes[1] goes into some details of what makes hypersonic aerodynamics different.
Similarly to how the supersonic regime is different enough from the subsonic regime that it's useful to distinguish the two, the hypersonic regime is different enough that it warrants its own name.
There's no exact definition, but typically around Mach 3-5 things start to behave differently enough.
This should be upvoted more, but I know HN prefers the binary explanations over the accurate ones in aerospace. "Hypersonic" isn't strictly defined like supersonic. Hypersonic phenomena begin to manifest at around 3 mach.
No offense, but you can type “hypersonic” into your favorite search engine and be reading the explanation on Wikipedia, literally in less than five seconds.
Hypersonic dual-mode ramjets are not suitable for 'general' applications. What makes them 'dual-mode ramjets' is that a single engine can work at both supersonic and hypersonic speeds. It's still a ramjet and so needs another means to get the engine/vehicle up to supersonic speeds.
As sibsling notes, maybe it could go into SR-72 or similar penetrating ISR platform is a reasonable guess. It might go into some sort of missile carrier (the carrier gets the expensive reusable dual-mode ramjet, so it can launch missiles with cheaper disposable scramjets directly at hypersonic speed?).
This isn't the world we've built, it's the world we live in. We didn't create this world, and we aren't yet powerful enough to change the nature of reality, so to blame humanity for the necessity of defense is silly. You'll be a lot less dispirted if you accept that the world we live in isn't a human creation and that we still haven't made it out of the struggle to survive.
There's nothing in the nature of reality that forces us to fight each other, unless you mean human nature. But we have a choice in whether we choose to be self-serving, which inevitably leads to conflict, or we choose to love our enemy. Loving your enemy requires dying to yourself, usually metaphorically, but it is an option. Humanity is entirely complicit.
In fact, each person is a microcosm of that dynamic. Each time we sacrifice a little bit of someone else's well-being for our own, we are engaging in a small bit of that warfare. Cut someone off in traffic because you're in a hurry; cheat a little to get ahead; don't clean up your public mess because laziness/rushed. It's all essentially that same dynamic.
>There's nothing in the nature of reality that forces us to fight each other
The reality that we are each capable of disagreeing with each other and having conflicting priorities, combined with the limited resources we have access to, is the nature of reality that forces us to fight each other.
> But we have a choice in whether we choose to be self-serving, which inevitably leads to conflict, or we choose to love our enemy.
Sounds very poetic, but how exactly does this apply to the case of Ukraine being invaded by Russia? Do you propose that the Ukrainians should love the invaders? If that should happen, then the Poles and the Romanians should also love the Russians when their time to be invaded comes?
If people were not pulling the oars, the galley of war would never leave the harbor. People have to remember there are more of them on the oars than there are those who hold the whips, although this is no easy feat when the incentives to paint this simple truth as some desperate impossibility are so high.
It’s all so simple until a missile strikes a hospital full of childern. Then what? Do you think you’ll be praised for your wisdom of oars and helms if you talk to the parents who just lost a child a week ago?
I'd argue Ukraine would be better served by the ~1000 ATACMS (in service 1991-) sitting in storage with their expiration dates rapidly approaching, than by a small number of some prototype hypersonic missiles.
Incredibly impressive if true. But below quote makes it sounds like they purchased a company with mostly ready design and made a prototype. Still pretty awesome.
> The successful development and testing of the dual-mode ramjet in such a short period of time was made possible through the collaboration of GE Aerospace’s team of engineers, Innoveering – a company acquired by GE Aerospace in 2022 that specializes in hypersonic propulsion – and GE Aerospace’s Research Center.
Now I want real engineering / everyday astronaut like breakdown of how it works.