Basically this is the first demonstrated propulsion method that really supersedes the SR-71's J58 + inlet. Instead of 0 to mach 3, this is like 0 to mach 10.
After watching these two videos it's unclear to me what is hard about building such engines. The numerical model seemed pretty pedestrian compared to anything else in fluid dynamics. If I understood correctly the detonation is basically stable depending on the right reactant intake. So you wouldn't need submillisecond active control or anything like that.
Is the heat the biggest problem? Do RDE get that much hotter than other engines or produce more vibrations?
I haven't ran the numbers or anything but I would assume supplying the high PSI oxygen for a long burn duration would be a considerable engineering challenge. You would need a system to jump start with bottled oxygen and then a heat exchanger in the combustion chamber to gasify LOX once stable detonation is reached. It is likely New Space companies have run the numbers on engine weight versus a contemporary staged combustion engine and found it to be little to no efficiency gain.
The rumors in Aviation Leak were that (one of the) Arora was an external burn (not RDL) unmanned aircraft around Mach 5-6. The "skyquakes" described here set off the local seismometers at regular intervals (eg 7am monday and wednesday), which doesn't normally happen. By looking at the parabolas (conic shockwave intersection with earth) of the arrival at an array of seismometers one could estimate the angle of the shockwave (Mach) and the angle relative the surface (attack angle). My memory is that it was accelerating Mach 3-5 at an angle over 45 deg.
Curious why they mention mach limits with their ramjet/rde I've seen them work under subsonic air conditions. Makes me wonder what the limiting factor is of rde under subsonic speeds. To me,the rde always seemed like the holy grail of propulsion even under subsonic speeds because of the significantly higher exhaust velocity. Something even rocket engines could benefit from due to the better ISP characteristics in low and high atm pressures.
If I recall scott Manley correctly, mach 5 is roughly the speed only reachable by ramjets. And also roughly the speed where aerodynamic heating starts generating plasma around the airframe.
Hence getting to mach 5 requires solving two problems that don't really need to be solved for slower speeds.
The point isn't specifically having trouble breaking the record, the point is that having to deal with the plasma makes it a completely different flight regime with completely different design considerations, exactly like how sustained supersonic flight requires all sorts of considerations that are very different from what subsonic flight requires.
I think what they mean is: Sonic speeds / Mach 1 brings a set of problems. Mach 2, 3, 4 don't add new ones. But Mach 5 does, hence warranting a different naming with hypersonic. At least that's how I understood the conversation.
I believe the second issue is that engines which work well at supersonic speeds don't work well at slower speeds and visa versa
"A typical air-breathing DMRJ propulsion system can only begin operating when the vehicle achieves supersonic speeds greater than Mach 3. In fact, since ramjet (and scramjet) engines don’t have rotating parts (compressor and turbine) as turbojet and turbofan engines, they rely on specially designed air inlets to compress the air to the pressure required for the combustion.
The efficiency, however, only gets sufficiently high when the speed reaches at least Mach 2, due to the higher temperature and pressure obtained in the combustion chamber. This is why ramjets usually need other means to reach the minimum speed for ignition, such as rocket boosters or, in the SR-71 Blackbird, dual cycle turbo-ramjet engines."
A barrage of regular missiles would easily be able to take out any aircraft carrier. You don’t need hypersonic.
This is due to the simple fact that you can only carry so much AA ammunition and restocking ammunition on a ship takes significantly longer than it does on land.
This isn’t even touching on drones, both flying and boats, as well as torpedos and mines.
Taking out an aircraft carrier isn’t difficult. It’s just that luckily, no country with the capacity to do so has been crazy enough to start ww3.
*using air breathing engine, I think. Earth escape velocity is Mach 22, 7.9km/s, 5 mi/sec., 67k mph, etc. Clearly there are faster guided man-made objects.
"Turbofans stop working, and you start needing to deal with plasma from air resistance" are the specific points here.
Moreover, if you can handle these issues, you can probably use similar tech to go even faster.
" Typical speeds for hypersonic aircraft are greater than 3000 mph and Mach number M greater than five, M > 5. We are going to define a high hypersonic regime at M > 10 to account for re-entry aerodynamics. The chief characteristic of hypersonic aerodynamics is that the temperature of the flow is so great that the chemistry of the diatomic molecules of the air must be considered. At low hypersonic speeds, the molecular bonds vibrate, which changes the magnitude of the forces generated by the air on the aircraft. At high hypersonic speeds, the molecules break apart producing an electrically charged plasma around the aircraft. Large variations in air density and pressure occur because of shock waves, and expansions. "
It is speeds where air starts forming plasma when hitting an object, which triggers all sorts of issues.
In practical aerospace, hypersonic generally means anything significnantly faster than the sr71, the mach 4-5 range being the low end and orbital velocities the high (mach 10).
I know this is all weapons related (and mostly single-use weapons), but I long for the supersonic passenger jets of my childhood. Or even subsonic ones with 5% more legroom.
That's fine. With the exception of routes that go from Europe to East Asia over the continent, there is no shortage of gruelingly long flights between South America and Australia, New Zealand and Europe that are done mostly over the ocean.
And that doesn't take into account the recent developments in reducing sonic booms.
As another comment notes, various companies take a shot at this from time to time. It's more an economic problem than a pure engineering one. When you can buy lie flat seating on most long distance routes (and even sort of cabins on some), it's not clear how big the market is for supersonic tickets that may cost even more (as was the case with the Concorde) and probably will have less range. Legroom isn't a problem on bigger jets. You just need to pay a big premium for it.
I also assume there's less market these days for flying NYC to London to shake hands and sign a deal over lunch and be back home for dinner.
Conversely (or to take it further really) I’d rather a way more comfortable experience on a much slower service. Yes, I’d like an airship cruise that takes a couple days to get me to my destination. Bring that back.
Apart from cost, the biggest objection to large supersonic passenger planes is noise. That prevents them from flying over inhabited areas. This limitation is also present with ocean liners.
I long for the return of airships. Slower, but probably they emit much less CO2 for the same weight transported. A good fit for people trying to avoid a climate apocalypse. Also more legroom.
Given that they would carry fewer people and would be much slower, I'd have to see the actual energy use analysis. As for legroom, as I noted elsewhere, that's just a matter of how much money you're willing/able to spend for your seat.
So, if I read that right, about a 50% per passenger predicted drop. Which, for a small fleet of slow travel airships, wouldn't even budge the needle on air traffic emissions overall.
Spiraling doom won't get us to reduce emissions. Id give airships a chance. I've been flight free for almost a decade but I would take an airship somewhere if it was done to a luxurious standard. Although for a bipedal mammal being airborne is a luxury in itself.
I guess it's less about how much energy per passenger, but what the energy source is. A plane or jet have to fight hard against the atmosphere to defy gravity. That absolutely cannot be decarbonized for passenger flight. But an airship floats. If you're only energy requirement is pushing a floaty thing around you can absolutely decarbonize. Batteries? Probably. How about one of the nukes that powers a sub? No idea! Maybe!
It's possible to use hydrogen to save helium, while keeping it safe. Even the designers of Hindenburg in the 1930s had in mind a design involving hydrogen enveloped by an outer helium layer to make it inert. But a total ban in US helium exports foiled their plans, leading to risky full hydrogen utilization. See <https://www.airships.net/hindenburg/hindenburg-design-techno...>:
"But Hindenburg’s potentially most innovative features were never actually implemented. Hindenburg was originally designed for helium, which was too difficult to obtain and too expensive to be vented to compensate for the weight of fuel burned during flight. To avoid the need to valve helium, several innovative solutions were proposed. One involved a set of inner hydrogen gas cells to be installed at center of 14 of the ship’s 16 helium cells. The flammable hydrogen would be protected inside the larger cell containing inert helium, and when it was necessary to valve lifting gas, hydrogen, rather than helium, could be released. When it became obvious that helium would not be made available by the Americans, and that the ship would be inflated with hydrogen, the inner cells were abandoned, but Hindenburg did retain the axial catwalk at the center of the ship that was installed to provide access to the valves for these inner cells."
I don't. Have you ever heard a sonic boom before? Supersonic aircraft are useless over land for that reason alone, and if the regulations regarding supersonic flight over land were lifted then the net result would be a small number of wealthy jetsetters subjecting hundreds of millions to ongoing, unpredictable, maddening explosions, akin to living in a warzone. This scenario is one of the worst plausible futures that I can imagine. Supersonic passenger jets are a dead end.
You could probably allow supersonic flights over the oceans and get a bit of the best of both worlds. But yeah hypersonic flights from NYC to LA are a terrible idea.
In the past decades research has been done about the sonic boom and how aircraft shape influences it.
This is one of the reasons new companies are looking into supersonic flight again.
America has strategic ambiguity when it comes to hypersonic tech..
It appears that America is behind. They keep reporting their hypersonic programs are failing.
The best tech is not presented to the public.
What happened with the NDAA makes it clear that defense contractors are hiding advanced technology related to UAPs.
The UAP Disclosure Act unanimously passed the Senate. When it got to the House, it was completely gutted by the man who is Lockheed's #1 Lobbying Recipient (Mike Turner). Here is the response from the Senate when the House killed the bill: https://www.youtube.com/watch?v=N0HoXkQXpVE
So it's clear, defense contractors have advanced technology that not even Congress or the President can learn about.
The line I've often heard from defense enthusiasts is that America appears behind on hypersonics because they're aiming for "true" hypersonic weapons, ie ones which are capable of a wide range of navigation while in powered hypersonic flight, as that's what actually makes the concept so potent, by making the missile so fast and unpredictable that current air defense systems would struggle to intercept it.
Without controlled navigable flight, "hypersonics" are much simpler, as you basically just have a ballistic missile, which can still be intercepted by traditional air defense (Russia's Kinzal being an example of this kind of so-called hypersonic missile).
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[ 2.9 ms ] story [ 96.7 ms ] threadhttps://www.defenceaviation.com/sr-91-aurora-aircraft/
The description seems to say that there's also a rde turbine to handle subsonic and low supersonic flight.
Hence getting to mach 5 requires solving two problems that don't really need to be solved for slower speeds.
"A typical air-breathing DMRJ propulsion system can only begin operating when the vehicle achieves supersonic speeds greater than Mach 3. In fact, since ramjet (and scramjet) engines don’t have rotating parts (compressor and turbine) as turbojet and turbofan engines, they rely on specially designed air inlets to compress the air to the pressure required for the combustion.
The efficiency, however, only gets sufficiently high when the speed reaches at least Mach 2, due to the higher temperature and pressure obtained in the combustion chamber. This is why ramjets usually need other means to reach the minimum speed for ignition, such as rocket boosters or, in the SR-71 Blackbird, dual cycle turbo-ramjet engines."
from https://theaviationist.com/2023/12/16/ge-aerospace-demonstra...
That would be bad for Taiwan.
This is due to the simple fact that you can only carry so much AA ammunition and restocking ammunition on a ship takes significantly longer than it does on land.
This isn’t even touching on drones, both flying and boats, as well as torpedos and mines.
Taking out an aircraft carrier isn’t difficult. It’s just that luckily, no country with the capacity to do so has been crazy enough to start ww3.
https://www.grc.nasa.gov/www/k-12/airplane/lowhyper.html
In practical aerospace, hypersonic generally means anything significnantly faster than the sr71, the mach 4-5 range being the low end and orbital velocities the high (mach 10).
https://boomsupersonic.com/commercial
That's fine. With the exception of routes that go from Europe to East Asia over the continent, there is no shortage of gruelingly long flights between South America and Australia, New Zealand and Europe that are done mostly over the ocean.
And that doesn't take into account the recent developments in reducing sonic booms.
I also assume there's less market these days for flying NYC to London to shake hands and sign a deal over lunch and be back home for dinner.
Cargo: https://ageconsearch.umn.edu/nanna/record/319295/files/ageco...
"But Hindenburg’s potentially most innovative features were never actually implemented. Hindenburg was originally designed for helium, which was too difficult to obtain and too expensive to be vented to compensate for the weight of fuel burned during flight. To avoid the need to valve helium, several innovative solutions were proposed. One involved a set of inner hydrogen gas cells to be installed at center of 14 of the ship’s 16 helium cells. The flammable hydrogen would be protected inside the larger cell containing inert helium, and when it was necessary to valve lifting gas, hydrogen, rather than helium, could be released. When it became obvious that helium would not be made available by the Americans, and that the ship would be inflated with hydrogen, the inner cells were abandoned, but Hindenburg did retain the axial catwalk at the center of the ship that was installed to provide access to the valves for these inner cells."
Btw, they are also VERY loud.
The best tech is not presented to the public.
What happened with the NDAA makes it clear that defense contractors are hiding advanced technology related to UAPs.
The UAP Disclosure Act unanimously passed the Senate. When it got to the House, it was completely gutted by the man who is Lockheed's #1 Lobbying Recipient (Mike Turner). Here is the response from the Senate when the House killed the bill: https://www.youtube.com/watch?v=N0HoXkQXpVE
So it's clear, defense contractors have advanced technology that not even Congress or the President can learn about.
Who would they sell it to? And why is any of what you said a bad thing?
Without controlled navigable flight, "hypersonics" are much simpler, as you basically just have a ballistic missile, which can still be intercepted by traditional air defense (Russia's Kinzal being an example of this kind of so-called hypersonic missile).