A successful Japanese trial of a ramjet engine designed for Mach‑5 aircraft

https://www.bgr.com/2178211/japan-hypersonic-engine-ramjet-2-hour-flights-to-us/

by rmason • 2 months ago

234 187 2 months ago

rbanffy2• 2 months ago

People say this like it's a simple engineering problem.

No. By itself, a new hypersonic engine can't make 2-hour flights between Japan and the US a reality. We are not even close to being able to build an aircraft that can do that - we don't even have the materials for that. What seems "easier" (as in "less impossible") is a hypersonic glider design that enters a suborbital trajectory and does shuttle-like aerobraking while it glides to its destination, before reengaging propulsion prior to landing on an airstrip (because passenger planes need to be able to abort landings and do multiple attempts). Not sure how reverse thrust would work there - variable geometry rocket bells?

kelseyfrog• 2 months ago

How long of a weightlessness period does this entail?

nine_k4• 2 months ago

Maybe not complete weightlessness, because at 80-90 km the atmospheric drag is still noticeable. But it should be enough of a unique experience.

holoduke• 2 months ago

What would a ticket cost like? 50k? Aren't those people in their own fancy private jet with whiskey, massages and party?

Ekaros• 2 months ago

Or have their own room in first class... Maybe time trade off isn't worth it for most of the people who can afford it at that point.

atoav2• 2 months ago

The actual time to skim off IMO is all the airport procedures.

whiplash451• 2 months ago

This is already a solved problem for the class of customers they are going after.

wat100002• 2 months ago

Not necessarily for extremely long haul flights. The airport side of things takes about the same amount of time regardless. For a transpacific flight, you’re looking at maybe 3-4 hours at the airport and 10+ hours in the air. Shaving down the airport side would be nice but a faster plane could save a lot more time.

rafram3• 2 months ago

Really? Obviously it varies by country, but there’s no customs/immigration when leaving the US, and security usually takes <5 minutes with PreCheck. Sometimes immigration takes a while on the other side, but it’s quick at airports with biometric gate systems. You still hear people talk about airport buffer time in units of hours, but I think that’s increasingly out of date.

bruce5112• 2 months ago

Yes, ymmv (a lot). But alas buffer time is getting higher, not lower.

Yes, TSA is a big part of the problem. It's less "how long it took" and more "how long can it take". I've personally experienced those days where "TSA decided to go slow" and a couple hours disappears. The 5 minute days just make that worse.

Yes, the airport matters. If you're at some small regional it's no big deal. JFK or Atlanta etc is another thing entirely.

Yes, domestic or international matters. Yes, flying business class makes it faster. Yes signing up for "special status" makes things faster.

But airports are typically some drive away from city center (both ends, in traffic). Security and immigration both take time (often significant time.) Door to door time is easily 6 hours more than flight time.

atoav2• 2 months ago

So how long before the actual flight departure will you be at the airport?

If I catch a train that is 10 minutes before the train departs on a metropolitan train station in Europe.

With planes in my experience arriving two hours before the actual departure is not uncommon at bigger airports, since there are more insecurities involved like how crowded security checks are, where your gate is, etc.

jonners00• 2 months ago

And the time wasted on transfers. I used to regularly fly from airports in NY, London, SF, Singapore, LA, Sydney, etc. I would block out the opportunities to work or rest, and the reality was that only the plane time was valuable for either. It was painful to see all the other blocks of non productive time, particularly the allowances for congestion and disruption between downtown and the airports. I would have paid thousands a flight to be able to check in/clear security at my hotel and then get driven to a holding bay at the airport, and then on to the gate, in a vehicle suitable for both work and rest.

vkou• 2 months ago

This is a solved problem in civilized countries. The time between arriving at an airport and boarding your plane in Japan is ~10 minutes, most of it walking. Because they don't spend an hour fucking around with clownshow security, and because boarding doesn't take forever, as people don't try to stuff ten pieces of carry-on luggage into five overhead bin spaces.

Customs always takes time, though, even in the happy (no extra questions, no bag searches) path.

---

Do you want to know the secret to fast security lines?

Either reduce the work security does, or open more lines and hire more agents[1], until they can meet the throughput requirements. Both seem to be anathema to an American airport.

---

[1] This also works to reduce lines and improve quality and cleanliness in other aspects of society. It's not that Japanese people don't produce any garbage, or dirt, it's that their public infrastructure is regularly and meticulously cleaned and maintained.

superkuh• 2 months ago

At that elevation at Mach‑5, air around the nose and leading edges can reach temperatures exceeding 1,000 degrees Celsius (1,832°F), a challenge...

It is not the conical nose or leading edges that are the show stopper problem(s). There the shockwave generally does not touch the craft. The internal shockwaves that touch the walls of the engine ducting are. The heat loading and heat soak ability on those shockwave impingement sites will limit the duration of hypersonic travel.

Hypersonic travel through the atmosphere is easy, a problem solved in the 1950s. Be conical and carry your oxygen internally. Hypersonic travel that is air-breathing is an entirely different class of problem and I don't think it is anywhere near to being solved.

The only silver lining is that at hypersonic speeds you don't need to be propulsive for very long to get anywhere.

switchbak3• 2 months ago

Supposedly the SR-72 has figured this out. Just rumours at this point, but apparently they’ve cracked the hypersonic air breathing puzzle on a usefully sized aircraft.

darkteflon2• 2 months ago

Cool science. But the article fails to take even a cursory stab at contextualising the plan against the economic, environmental and political backdrop - doesn’t even mention that there’s already been one failed supersonic commercial flight programme. This is as pie-in-the-sky as it gets.

HNisCIS5• 2 months ago

Whenever you look at supersonic or hypersonic commercial aircraft plans you should assume one of two things.

A. It's a bait and switch by a founder who wants to pivot to weapons/military aircraft but wants to be able to hire high grade talent without paying the "we're gonna kill people" premium, can pivot once a good chunk of the workforce is complacent with a paycheck. You laugh but this happens SO FUCKING MUCH.

B. It's for business jet scale operations for billionaires. There are >3000 billionaires and however many corporate aviation departments and if you can build a super/hypersonic private jet that's not horribly expensive to operate the "time savings"* for that class of person will demand they buy one.

* when I say time savings I mean dick measuring contest

Seattle3503• 2 months ago

What companies are examples of that bait and switch strategy?

Grosvenor• 2 months ago

* when I say time savings I mean dick measuring contest

And in this case smaller is better?

nradov2• 2 months ago

Defense contractors don't pay premium wages. Rather the opposite. Many employees specifically want to work in the field in order to contribute to the national security mission.

loeg• 2 months ago

Safety should probably also be considered.

hdndjsbbs2• 2 months ago

I think a lot of the Concorde failure is tied to its status as a British-French project. Trans-Pacific flights are much longer and there's a lot of money in PEK -> LAX than in JFK -> LHR.

Qantas wanted to offer London to Sydney, but they couldn't fly supersonic over land. Mainland China or Japan to Australia is a feasible route for high-margin, low-capacity supersonic flights.

If you could make the flight from Beijing to California take less than 5 hours that seems like a premium product many ultra wealthy people would spring for. Dubai to SFO is also a possible route.

gottorf• 2 months ago

Dubai to SFO is also a possible route

Is there really that much premium traffic between Dubai and the Bay Area?

VerifiedReports• 2 months ago

ORD -> Vatican

decimalenough• 2 months ago

There is a lot of money in NYC-LHR, that's why Concorde continued to fly that route and profitably too, once they realized how high they could yank the prices and still fill the plane.

Also, Concorde's maximum range was 4,488 mi, which was calibrated to allow trans-Atlantic but not much more. Trans-Pac was not an option and even Australia to North Asia would be a stretch.

wat100002• 2 months ago

Everyone thought SSTs were going to be the next big thing. Both the US and USSR had projects. The 747 got a hump so it could easily be converted to a freighter once it was made obsolete by supersonic passenger planes.

Despite two superpowers making the attempt, and plenty of time for more tries since then, Concorde is the only one that came even remotely close to something commercially viable.

I’m sure there’s a market for California to China in five hours. But is it enough to support a whole new type of aircraft? Fuel burn is going to be enormous. Maintenance on something so cutting edge will be extremely expensive. Tickets would probably cost more than a private room on a widebody.

vitally3643• 2 months ago

I was pretty sure the whole Concorde thing failed because people don't like it when you sonic boom an entire city dozens of times a day. And that all attempts to reduce the sonic booms necessarily resulted in flight times that aren't significantly faster than traditional subsonic flights, rendering the entire thing moot.

It was impractical due to physics, not some weird racism. You simply can't push a supersonic shockwave over inhabited areas, and the only way to not do that is to fly subsonic over land. Even if the oversea leg is supersonic, the tickets were much more expensive for not very much shorter flights. It wasn't a valuable proposition for most people.

KennyBlanken2• 2 months ago

It's not tied to anything other than there not being enough people who care enough to spend the sort of money required.

The people who have that kind of money are going to be more interested in flying in a jet share doing mach .96 leaving when they want to leave, going where they want to go, when they want to go, how they want to go, with who they want to go with.

You get treated like a criminal for forgetting your shampoo bottle is 2 ounces too big for some dipshit TSA agent's liking, and meanwhile the ultrawealthy are shuttling around physical assets worth millions of dollars in their private jets and customs barely does more than stamp their passport.

steveBK123• 2 months ago

One analysis I read by a marketer that makes good sense is that the speed was worth paying for LHR to JFK but not really on the return given the clock changes and speed.

Getting to NYC before the clock time you left London was a cool trick. It allows you to make a morning meeting in NYC without coming in the night before.

But flying subsonic leaving NYC after dinner and arriving in London for breakfast works fine. Getting to London faster in 3.5 hours travel time but 8.5 hours later clock time means losing a day in the air effectively.

laughing_man3• 2 months ago

If it stays in the realm of the ultra wealthy I don't see how it will succeed in the end. Commercial aircraft are really expensive to design and qualify, and you need to have a lot of sales to justify a new model. Ultra wealthy people are willing to pay more, but they also demand luxuries that take up a lot of space.

The only reason Concorde did as well as it did, economically speaking, is the respective governments footed the bill for development.

rdl2• 2 months ago

Vastly more favorable today than it was when Concorde flew.

1) Rich people are WAY richer, and time is even more valuable 2) Businesses have some very important employees and "2 day trip" vs "3-4 day trip" is worth $50-100k 3) Larger population of people able to pay $20-30k for a flight than ever before.

The biggest practical impact is there's probably going to be a private jet version instead of just a commercial one, and there will likely be transpacific demand exceeding transatlantic. Also government/military use.

deadbabe2• 2 months ago

What are some examples of employees so important you would pay $100k to get them somewhere immediately?

amanaplanacanal• 2 months ago

I think the SpaceX plan for point to point travel might be even more pie in the sky. Or maybe a tie.

bob1029• 2 months ago

I think it's more practical. They've already got humans flying.

jojobas• 2 months ago

Point to point rocket travel was never a good faith pitch, it was a hype thing (and your pension money are going into the fraud soon).

godelski3• 2 months ago

  > This is as pie-in-the-sky as it gets.

All your critiques are things we heard about Starlink too. "Oh, you're just reinventing Globalstar[0], which already failed. What makes you think this time will be different?" The question isn't wrong, per say, but most of the time it is used dismissively rather than in earnest. There's thousands of products you use today that were invented and ahead of their time. Hell, Google itself is famous for this. A great example being Google Glasses. When they first came out you could get punched in the face[1], but now there's Meta Glasses, Snap's, and dozens of others. The landscape changes, and fast. Just because others failed before doesn't mean others later won't.

It's not bad to ask these questions, but it is easy to be too dismissive. People love to tear things down, but not build them up. The two go hand in hand, but there needs to be a more measured approach. Frankly, projects can fail for many reasons. Too often it is simply bad luck. You either learn from the past or you repeat it.

[0] https://en.wikipedia.org/wiki/Globalstar

[1] https://www.cnet.com/tech/services-and-software/google-glass...

darkteflon2• 2 months ago

I’m in favour of projects like these - even on spending taxpayer money on them. I think it’s super cool and I would love to see it. Yeah, I also think it’s extremely unlikely.

However, when you’re doing journalism, you should contextualise for your readers. TFA doesn’t even try to do the bare minimum.

_carbyau_• 2 months ago

This is as pie-in-the-sky as it gets.

I saw the "sounding rocket" and thought: Oh, hypersonic missiles money.

sfifs• 2 months ago

Concord was very old technology. I am quite sure a clean sheet now

1. Would have much lower sonic booms thanks to recent research (quite a bit of it by NASA on wing geometry) and more importantly computer simulation available now

2. The engines would be far more fuel efficient

3. The flights would be able to have better efficiency in the subsonic regime as well. Just see what winglets and the like have done to fuel economy .

I fly 14 to 18 hour routes maybe 4-5 times a year on business paying 5x the economy cost and it still sucks. Breaking the flight with a connection (IMO) sucks more. My management flies such routes every month. There is a lot of revenue headroom in that fare gap for something that flies maybe 3x-4x as fast which military aircraft already do.

What will hold back the idea is conservatism among the business managers in aircraft manufactures and incumbent airlines who will "draw lessons" from a 50 year old experiment

notahacker• 2 months ago

It'd be far more efficient than the 50 year old tech, but so is the baseline tech they're comparing it with, and the market has optimised heavily for price competition (and has a lot more private jets doing exactly the route and time executives with Concorde money want) and needs speed somewhat less when it's a lot easier to stay in touch with a business whilst inflight. Ultimately there's not much to draw lessons from that suggests it's going to sell enough aircraft to recover the investment of building and certifying it (even comparatively simple niche aircraft like the A380 struggled there), which is why even Boom is now reinventing itself as a provider of turbines for AI datacentres to try to fund its development costs...

trhway2• 2 months ago

2. The engines would be far more fuel efficient

not really. In supersonic regime Concorde engines were pretty good, and you'd not beat them today by much.

Concorde was using afterburners to accelerate to supersonic and this is where it burned a lot of fuel. Designing engines which would give you good thrust at subsonic speeds without afterburners and would still perform well in supersonic is still much unsolved. Just look at the best military engines today - they all under Mach 2 and can't give even 3000 miles range.

And without increasing efficiency we can't really get much beyond the Concorde's 4500 miles. I.e. unfortunately there seems to be no current tech (or coming right tomorrow morning) that will allow Trans-Pacific.

It looks more feasible to me that Starship suborbital SFO-to-Shanghai will come well before a new Concorde on that route. Especially considering that Starship's ballistic trajectory is more fuel efficient on such long distances than supersonic plane flight.

zardo• 2 months ago

Probably because there is no plan to develop a commercial plane.

domoregood• 2 months ago

Ahh, but can it run DOOM...?

Insimwytim• 2 months ago

At that elevation at Mach‑5, air around the nose and leading edges can reach temperatures exceeding 1,000 degrees Celsius (1,832°F), a challenge the U.S. Air Force has struggled to overcome with its own hypersonic jets.
To handle that level of heat, engineers constructed an advanced thermal‑protection system that maintained the aircraft's interior near normal operating temperature, allowing the onboard avionics and control electronics to function normally.

Hindenburg 2.0 waiting to happen

inglor_cz• 2 months ago

We have a lot of experience with heat shields from cosmic reentries now, though. This is probably doable.

stymaar3• 2 months ago

Hindenburg 2.0 waiting to happen

Fortunately there's no hydrogen in that plane.

Padriac• 2 months ago

I imagine passengers will be exposed to very high noise levels during flight.

BurningFrog• 2 months ago

I don't have a good intuitive feel for that.

At 25km altitude, with 1% of normal atmosphere, maybe you're close enough to vacuum that it can get really quiet?

pdonis• 2 months ago

The engine noise can still be conducted through the body of the plane. With the kind of ramjet being talked about, I think that's still likely to be significant even at very high altitude.

stymaar3• 2 months ago

This effect would help mitigate the noise heard by people outside of the plane (but I suspect that noise is negligible compared to the sonic boom), but in the plane the sound would mostly be propagated though the fuselage of the plane, not through air, so it's not going to help.

nubinetwork• 2 months ago

I've always wanted someone to bring back the Avro Arrow to use the Iroquois engine for freight, but I don't think anyone has the knowledge to even pull it off anymore.

switchbak3• 2 months ago

I’d love to have a big die cast model of one, but that’s about as close as we’ll ever get to the Avro flying again.

I don’t think you’d be pushing much freight on an Arrow (though I’d love to fly one!).

An XB-70 with modern engines? Now that would be interesting.

threwrfaway• 2 months ago

The avro was an excellent plane for the time. It would have been a good plane for the Cold War. It was a plane well suited for Canada's threat environment. The missiles that replaced it sucked.

However, the Avro wasn't anything any of the other great powers couldn't do back then or today and it was ruining Canada financially.

The only question I have about the Avro is: "Could foreign sales have rescued the plans and Ottawa's budget?"

I think not. In an era of hyper-protectionism where the Brits built an air cooled nuclear reactor [1] rather than buy Canadian heavy water, it's inconceivable that Canada would have found buyers.

[1] resulting in the largest nuclear disaster until Chernobyl. Keep in mind, at the time, English Canada largely thought of itself as British and even decades later fumed at the new flag lacking the Union Jack. And yet the Brit's didn't but their heavy water.

laughing_man3• 2 months ago

Boy, that's an evergreen headline.

jjtheblunt• 2 months ago

that headline uses a subjunctive verb mood "_could_ <verb>" and those titles are seemingly always clickbait

brandelune• 2 months ago

Two news items in one : Japan is getting ready for hypersonic missiles, and Japan’s elite does not give a damn about global warming.

argimenes• 2 months ago

The world's elites have factored in global warming already. It's a cost they are happy to shift onto their descendants.

ranyume• 2 months ago

Their descendants

I'm sad to tell you, they're already looking for places on earth to buy land to build their nest after they decimate or help decimate humanity.

numpad02• 2 months ago

Next generation of. The Type 25 HVGP just entered service few months ago. That one is just a two-stage Scud, but the Block 3 or NG or Type 35 or whatever of that could have this tech.

MarxOk• 2 months ago

As a Canadian who travels to Europe about once per month I am very excited for this :D

dnnddidiej• 2 months ago

Wait 20 years to save a few hours :)

belviewreview2• 2 months ago

Interesting, but assuming they can get the engine to work as intended, the question still remains how the passenger jet would get up to Mach 5 so the engine can start working. A solid-fuel rocket booster that would then drop off?

credit_guy• 2 months ago

It is a safe bet that the first applications will be missiles and there won't be any passengers to worry about.

jandrewrogers• 2 months ago

Interns provide the guidance.

flohofwoe5• 2 months ago

I may be wrong but I think a ramjet doesn't need Mach 5 to ignite, Mach 3 to 6 is just where it is most efficient at high altitudes.

E.g. early German experiments during WW2 based on the Lorin tube (https://en.wikipedia.org/wiki/Ren%C3%A9_Lorin) only had to get to 320 km/h to start working:

https://en.wikipedia.org/wiki/Kronach_Lorin

belviewreview2• 2 months ago

Ok, but the question still remains, how is it going to get up to the required speed? And in a way that is practical for a passenger plane?

trhway2• 2 months ago

https://en.wikipedia.org/wiki/Kronach_Lorin

coal burning ramjet!

"It was initially proposed that a wire-mesh basket holding coal be mounted behind a nose air intake, protruding slightly into the airflow and ignited by a gas burner. [...] The air passing through the ramjet would take the gases from the burning coal ..."

Ngraph3• 2 months ago

First time I heard the word "ramjet" was as a kid watching the Goliath episode of Knight Rider. Definitely not a documentary, but the word stuck. Then the Blackbird showed up in some plane book, and that was that. Ramjets back in the news. Kid me is having a great morning.

AIorNot• 2 months ago

Yes it looks a lot more cheesy now than I remember as a kid

https://youtu.be/SpEO-jIKhE8?si=89Qw1_AOXYow9PfR

But ramjets have been promised to us for years

Ngraph3• 2 months ago

So nostalgic. AI, self-driving, ramjets — they packed it all in. And the thing that dates it isn't any of that, it's that nothing is a touchscreen. The future used to be chunky buttons.

testing22321• 2 months ago

“Roger ramjet he’s our man, hero of the nation!!

https://m.youtube.com/watch?v=E7SqSNQeAFM

Ngraph3• 2 months ago

Roger Ramjet! Now I've got that theme stuck in my head. Pretty sure that's where "ramjet = unstoppable" got hardwired in me.

rusk2• 2 months ago

We had Concorde - it was too expensive to operate safely.

Traubenfuchs• 2 months ago

We just didn‘t have enough billionaires back then. Today the Thiels and Musks and Bezos will be able to afford this.

rusk2• 2 months ago

Agree that this is a matter of economic viability rather than technology. Presumably somebody could just go back and resurrect the Roles Royce IP

There would be the nice side benefit of maybe having all these guys in one place, upon an experimental aviation platform.

DeathArrow• 2 months ago

Another Concorde?

mytailorisrich• 2 months ago

It seems to me that hypersonic engines are the fusion power of aeronautics. Always 10 years away.

sigmoid10• 2 months ago

Building a ramjet that is more efficient than rockets while travelling at several times the speed of sound is the easy part. The hard part is getting up to that speed first, because they give basically no thrust at low speeds. So you always need a two component engine and fuel system, with each component being useless at either launch or in-flight. Basically a similar reason why only the military uses VTOL planes. The military has no problem strapping a rocket booster on a ramjet missile.

m4rtink4• 2 months ago

And once you do all that, you will need to also handle the massive atmospheric heating from friction, so that the whole thing does not melt during flight.

Again, not that problematic for missiles due to shorter flight times and single-use ablative heatshields being viable.

phire3• 2 months ago

Is a Mach-5 passenger aircraft actually the goal of this project?

Seems more likely that Japan is designing this engine for a hypersonic cruise missile program, and the passenger aircraft concept is somewhat of a cover.

IMO, there is no point in a Mach-5 Aircraft (other than cruise missiles). There is potentially some point in Mach 2-3 aircraft, (not that we have ever made them commercially viable) but at the boundary to hypersonic, you might as well just switch to a suborbital hop concept.

A suborbital hop gets you to anywhere in the world within ~90min, avoids issues of supersonic overflight and you don't need to worry about the massive engineering issues caused by sustaining hypersonic flight. And as a bonus, the passengers get a hour of weightlessness.

m4rtink4• 2 months ago

90 minutes is a full low Earth orbit cycle. For a suborbital hop it should be about half of that at maximum for any 2 points on Earth.

petterroea• 2 months ago

I didn't initially believe these numbers, but if you look at some real life stats, you are probably right.

Nominal SECO for the last starship mission was at ~8 minutes and it took ~20 minutes from deceleration started (well, from air resistance outweighed the forces of acceleration) to landing. So basically 30 minutes of flight is just the "getting up to speed" and "slowing down" part. Both account for some distance traveled, but still. ~45 minutes is probably a good bet.

Do note however that you may have to go around the world "the wrong way" to get some places due to launch constraints. But living in a world where going around the world "the wrong way" is the easier path is interesting. Imagine that.

thrownthatway• 2 months ago

90 minutes is a low earth orbit period.

A suborbital craft won’t be travelling at that speed.

adev_• 2 months ago

you might as well just switch to a suborbital hop concept.

One is not exclusive to the other.

Skylon was expected to use air breathing engine up to Mach5+ and switch to rocket engine beyond it.

You can probably do the same for a suborbital airliner if you are insane enough.

numpad02• 2 months ago

Air breathing engines don't need the oxidizer tank, so like the 2/3 of a rocket just goes away before even touching Tsiolkovsky math. That improves payload mass fraction massively.

Also, this doesn't scale down to Mach 3-4 and under. This thing uses scramjet, or supersonic combustion ramjet. It REQUIRES intake air to be at high supersonic speeds for it to work.

MrMikardo932• 2 months ago

It REQUIRES intake air to be at high supersonic speeds for it to work

This is why I am highly sceptical it can be part of a commercial supersonic passenger jet: how do you get from subsonic -> supersonic without also tacking on some kind of conventional jet engine?

MrMikardo932• 2 months ago

(not that we have ever made them commercially viable)

Concorde was commercially viable at Mach 2.2 in supercruise (although there's a common misconception that it was not).

However, its overheads were very high, and its applicability was severely limited by fears around the sonic boom (most particularly in the US, which banned supersonic flight overland, possibly largely because they wanted to kill off foreign competition).

phire3• 2 months ago

The individual aircraft could be operationally viable on certain routes, but the whole program was not commercially viable.

eagleal• 2 months ago

Japan, Italy and UK have a program for a competing F35 design, GCAP. And Japan is focusing mainly on the engines.

Given there will at some point be the need to deliver competing cruise missiles for this platform, and after the crisis of the US not being able to keep demand with Israel's and Ukraine's orders they greenlighted SK and Japan to enter the European defense market, to answer your question yes, this is of course a defense related project.

There's been an industry request to develop native defense components on these matters within the EU following pressures and contrasts with the US (on a report to the EC for the ReArm campaign, EU's biggest playes of aerespace industry made a joint report estimating 60-80% of their components and tech are sourced from the US).

lonelyasacloud• 2 months ago

Is a Mach-5 passenger aircraft actually the goal of this project? Seems more likely that Japan is designing this engine for a hypersonic cruise missile program, and the passenger aircraft concept is somewhat of a cover.

Case of China's got them, and can't rely on the Orange Emperor and his heirs to have their backs.

markvdb• 2 months ago

From a science and engineering point of view, I root for this.

From an environmental point of view, I hope this won't materialise for some time.

randomNumber7• 2 months ago

It can be nuclear powered, so you don't have CO2 emmisions /S

You just need to add heat to the air at the point where the diameter is the lowest.

The russians are maybe using this idea for one of their new cruise missles named Burevestnik, although for them the nuclear emmisions are likely a positive side effect.

avadodin• 2 months ago

The original submission didn't mention ramjet.

I always thought it was an underutilized design that could be improved for practical applications.

Improved enough, it could become cheaper and more environmentally-friendly than current aviation whereas regular supersonic jets are never going to achieve that.

fancyfredbot2• 2 months ago

For many many reasons this engine only has one economic application - delivery of a nuclear payload in a way which is very hard for missile defences to stop.

ICBMs can go faster than this already but as I understand it they go higher allowing for earlier detection and they follow a more predictable trajectory which makes interception more realistic.

I find super fast missiles far scarier than advanced AI. I suppose they maintain the "mutually assured destruction" which might be the main reason there hasn't been a nuclear war since WW2, but it's not a huge comfort.

emptyfile• 2 months ago

Well here's an economic application without nuclear tipped warheads.

https://en.wikipedia.org/wiki/Meteor_(missile)

throwaway20374• 2 months ago

The Wiki pages says top speed is about Mach 4. There are already multiple rockets from US, Russia, and China that can achieve the same (or more) but with a solid-fuel rocket motor. What is the advantage of a ramjet here? It just seems way more complex and much less well tested (in labs and in combat). Also, has this missile (Meteor) been used in any combat scenarios? To be clear, the max speed for any fighter jet is about 2.5 Mach. Once one (or two) of these missiles has locked on, you are done. I read some funny commentary once about how to shoot down a modern fighter jet: Two missiles. They can dodge the first one, but sacrifice so much speed, that the second one can easily find its target.

newsclues• 2 months ago

I find fast missiles with AI to be pretty scary. Heck a slow drone with AI targeting chasing me is bad enough...

loloquwowndueo• 2 months ago

You only need to draw a fake moustache on yourself to fool it, or something.

Quarrelsome• 2 months ago

I find fast missiles with AI to be pretty scary

Not sure I entirely appreciate the use-case vs classical targeting. I'd imagine you're going so fast that you don't really have the opportunity to engage in thought that is particularly useful.

b65e8bee43c2ed0• 2 months ago

judging by what we saw so far in Russia, Ukraine, and Israel, defensive missiles don't require particularly sophisticated offensive missiles to overwhelm.

RicardoLuis0• 2 months ago

yeah, but those are using conventional explosives, only countries like the US and Russia have enough nukes to do the same with nuclear explosives, a country like japan would need a sophisticated missile instead

octaane• 2 months ago

My take is also a missile, but as an interceptor, not offensive purposes. North Korea has shown that they can deliver a payload to Japan if they want. If the NKs do decide to launch something at Japan, it's not going to be tipped with conventional explosives. It'll be a nuke. Hypersonic interceptor seems the more likely application is this tech to me.

fancyfredbot2• 2 months ago

I think that hypersonic interceptors would use a rocket motor and not a ramjet, but I'm not sure.

I think this is for offence because I understood the advantage of this engine (compared to a rocket engine) is that you don't carry oxygen so you can carry more fuel and get more range. I think range is much more useful for offence than defence.

I am possibly making myself look foolish now as I'm not an expert on either rockets or ramjets and I might have incorrectly dismissed defensive applications.

musicale• 2 months ago

I find super fast missiles far scarier than advanced AI

But what about super fast missiles with advanced AI?

Gravityloss• 2 months ago

Ramjets were developed right after the second world war and Mach 4+ was reached in the fifites. It's complicated but not extremely. See Antonio Ferri or Lockheed X-7.

It turned out out solid fuel rockets are operationally more practical for the use cases like air defence, long range missiles that are ballistic instead of cruising in the atmosphere and so on. And jet engines are more efficient for subsonic cruise missiles. Ramjets are still used in some missiles like the long range mach 3 air-to-air Meteor.

pfdietz6• 2 months ago

There have been air-to-air missiles using rocket-ramjet combinations: they start as a rocket, then once up to speed an inlet opens and they transition to ramjet mode (using the same chamber and nozzle). It extends range. Ramjets are best for maintaining speed rather than accelerating to speed.

EDIT: I see this was referenced above (Meteor).

flohofwoe5• 2 months ago

Ramjets were developed right after the second world war

Development already started during WW2 as one of many German last-ditch experiments, for instance:

https://en.wikipedia.org/wiki/Kronach_Lorin

...it never went into an actually flying airplane though (apparently there were test flights with Lorin tubes attached to propeller planes, but only to test the Lorin tube behaviour under flight conditions, not as an engine replacement).

The idea and patent itself is over a century old by now:

https://en.wikipedia.org/wiki/Ren%C3%A9_Lorin

SEJeff• 2 months ago

This is why Ukraine is so excited to get up to 150 Gripens (with Meteor loadout) from the Swedes.

abbadadda• 2 months ago

I actually learned about what a ramjet is after looking up the definition of “scramjet” when watching the _Top Gun: Maverick_ movie with my son. This is at the beginning of the movie when he is flying the Dark Star plane designed in conjunction with Skunk Works from Lockheed Martin. Well, we are obviously a ways away from Mach 10 reached in the film by the SR-71 Blackbird descendant, the new technology pushing Mach 5 and into high hypersonic is pretty impressive.

A scramjet is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow. As in ramjets, a scramjet relies on high vehicle speed to compress the incoming air forcefully before combustion, but whereas a ramjet decelerates the air to subsonic velocities before combustion using shock cones, a scramjet has no shock cone and slows the airflow using shockwaves produced by its ignition source in place of a shock cone - Wikipedia

pfdietz6• 2 months ago

Ramjets are limited in the speed they can operate because slowing the air to subsonic speed in the engine causes it to become hot, and the temperature increases rapidly with speed (the kinetic energy of an incoming air parcel is proportional to the square of the vehicle's speed, and most of that energy is being converted to heat.)

throwaway20374• 2 months ago

As I understand, the problem with anything over Mach 4 (or 5), the metal begins to disintegrate. It is fine for a one way missile, but not a reusuable aircraft. Without some alien tech (see 1990s game "X-Com 2"), I cannot believe that we can build a reusuable aircraft that can reliably and safely fly for long periods over Mach 5.

TedHerman• 2 months ago

PG celebrates Boom's pivot to power generator supply.

api• 2 months ago

I kind of think today's air travel is in an uncanny valley.

I'd prefer either: just as uncomfortable or even more so but very fast, like multiple mach numbers fast. I live in the Midwest and go to the West Coast often, and it usually takes 5 hours -- I'd cram into a less comfortable seat for 2 hours instead to get there at mach 2.5.

OR... airships. Big cushy seats. A lounge with fast wifi and desks. A coffee shop. You can walk around. The trip takes all day, or overnight with a sleeping cabin. Trains could fill this niche too, but airships could go overseas.

Go faster or go roomier.

dzonga• 2 months ago

I can't see how this would work for civilian purposes - since you need to counter the higher temperatures from higher altitudes. ceramic tiles (heat protection) - then u r heavy. this is based on noob aeronautics reasoning btw.

Jaauthor• 2 months ago

Speed Racer unavailable for comment.

A successful Japanese trial of a ramjet engine designed for Mach‑5 aircraft

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