> 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.
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.
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.
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.
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.
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?).
Readit News
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.
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.
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.
If they purchased the design it's because GE Aerospace has the manufacturing and sales arms to actually make it real.
Dead Comment
What was once GE Appliances was sold to Haier 8 years ago.
https://www.geaerospace.com/news/press-releases/other-news-i...
They really seem to love to talk about how fast they move except wait:
https://www.geaerospace.com/news/articles/100-year-anniversa...
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.
Cool video from Scott Manly talking about RDE's: https://www.youtube.com/watch?v=rG_Eh0J_4_s
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.
https://youtu.be/QlMX6TYdU7I
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.)
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 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.
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.
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.
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.
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.
The main reason supersonic flight is dead is the sonic boom. Until that issue is resolved they are banned over land, unfortunately.
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.
This is DoD language, so more secret drones I would think.
What advantage does an air-breathing engine have in this capacity over MIRVs and decoys?
The air is part of the fuel and onboard fuel hydrogen or some other thing to burn is the other half.
Really at >Mach 5 you'll be there fast. At Mach 5 NY to London in 54 min. Mach 10 it's 12 minutes.
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.
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.
I don't know at what speed a rocket has to be going, before the kinetic impact of 200Kg of solid metal exceeds the energy of 200Kg of explosives.
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.
[1]: https://archive.aoe.vt.edu/mason/Mason_f/ConfigAeroHypersoni...
It's a waste of money though as the Ukraine war showed that the Russian Kinzhal missile have limited utility and can be intercepted.
Naval drones and long-range drones are not only cheaper but also more effective.
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?).
Apparently they had to completely rethink and refocus the project part way though due to new technology becoming available.
That tech is probably this rotating detonation dualmode ramjet.
But might be that with a functional dual mode ramjet, assuming that was the major holdup, perhaps the project could be on track again?
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