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A successful Japanese trial of a ramjet engine designed for Mach‑5 aircraft
- rbanffy 5mo agoPeople 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?
- deleted 5mo ago[deleted]
- kelseyfrog 5mo agoHow long of a weightlessness period does this entail?
- holoduke 5mo agoWhat would a ticket cost like? 50k? Aren't those people in their own fancy private jet with whiskey, massages and party?
- Ekaros 5mo agoOr 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.
- deleted 5mo ago[deleted]
- atoav 5mo agoThe actual time to skim off IMO is all the airport procedures.
- whiplash451 5mo agoThis is already a solved problem for the class of customers they are going after.
- wat10000 5mo agoNot 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.
- rafram 5mo agoReally? 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 You still hear people talk about airport buffer time in units of hours, but I think that’s increasingly out of date.
- bruce511 5mo agoYes, 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.
- superkuh 5mo 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.
- switchbak 5mo agoSupposedly 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.
- darkteflon 5mo agoCool 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.
- HNisCIS 5mo agoWhenever 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 5mo agoWhat companies are examples of that bait and switch strategy?
- Onavo 5mo agoCan't give any examples but I have definitely heard the same about a lot of aerospace startups through the grapevine. As for OP's point about private jets, Boom supersonic is your classic example.
- HNisCIS 5mo agoI can't name names but 3 of the startups I've worked at. Places I haven't worked: Skydio Applied Intuition Saildrone Planet Labs Boom Scale AI Also worth noting that sometimes it's on purpose, sometimes the founders are all "we're gonna save the world" then AFWERX enters the chat with a big fucking check and the founders yell "Nevermind! Guess we're the baddies now! How many slaughterbots did you say?"
- domoregood 5mo agoAhh, but can it run DOOM...?
- deleted 5mo ago[deleted]
- Insimwytim 5mo 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
- Padriac 5mo agoI imagine passengers will be exposed to very high noise levels during flight.
- BurningFrog 5mo agoI 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 5mo agoThe 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.
- stymaar 5mo agoThis 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 5mo agoI'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.
- switchbak 5mo agoI’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 5mo agoThe 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.
- protocolture 5mo ago[flagged]
- laughing_man 5mo agoBoy, that's an evergreen headline.
- jjtheblunt 5mo agothat headline uses a subjunctive verb mood "_could_ <verb>" and those titles are seemingly always clickbait
- brandelune 5mo agoTwo news items in one : Japan is getting ready for hypersonic missiles, and Japan’s elite does not give a damn about global warming.
- argimenes 5mo agoThe world's elites have factored in global warming already. It's a cost they are happy to shift onto their descendants.
- ranyume 5mo 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.
- numpad0 5mo agoNext 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 5mo agoAs a Canadian who travels to Europe about once per month I am very excited for this :D
- dnnddidiej 5mo agoWait 20 years to save a few hours :)
- belviewreview 5mo agoInteresting, 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 5mo agoIt is a safe bet that the first applications will be missiles and there won't be any passengers to worry about.
- jandrewrogers 5mo agoInterns provide the guidance.
- flohofwoe 5mo agoI 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 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 https://en.wikipedia.org/wiki/Kronach_Lorin
- belviewreview 4mo agoOk, 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?
- flohofwoe 4mo agoI'm no aircraft engineer, but I guess it would use traditional jet engines to get up to some low Mach 1+ speed until the ramjet gets enough air to bite on. My bet is that this hasn't been done yet simply because it wouldn't be economical (the technology itself is a century old and has been tried over and over again), and that the 'civilian ramjet aircraft' is just a feel good story for what will end up as purely military usage, and most likely not in an airplane, but in missiles (there are a couple ramjet engine missiles in use already, like the European Meteor).
- Ngraph 5mo agoFirst 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 5mo agoYes it looks a lot more cheesy now than I remember as a kid https://youtu.be/SpEO-jIKhE8?si=89Qw1_AOXYow9PfR https://youtu.be/SpEO-jIKhE8?si=89Qw1_AOXYow9PfR But ramjets have been promised to us for years
- Ngraph 4mo agoSo 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 5mo ago“Roger ramjet he’s our man, hero of the nation!! https://m.youtube.com/watch?v=E7SqSNQeAFM https://m.youtube.com/watch?v=E7SqSNQeAFM
- Ngraph 4mo agoRoger Ramjet! Now I've got that theme stuck in my head. Pretty sure that's where "ramjet = unstoppable" got hardwired in me.
- rusk 5mo agoWe had Concorde - it was too expensive to operate safely.
- Traubenfuchs 5mo agoWe just didn‘t have enough billionaires back then. Today the Thiels and Musks and Bezos will be able to afford this.
- rusk 5mo agoAgree 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 5mo agoAnother Concorde?
- mytailorisrich 5mo agoIt seems to me that hypersonic engines are the fusion power of aeronautics. Always 10 years away.
- sigmoid10 5mo agoBuilding 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.
- m4rtink 5mo agoAnd 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.
- phire 5mo agoIs 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.
- m4rtink 5mo ago90 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.
- thrownthatway 5mo ago90 minutes is a low earth orbit period. A suborbital craft won’t be travelling at that speed.
- m4rtink 5mo agoLike, you could do a partial orbit & then drop down over the destination. But it would need much more delta-v & an orbital class heat shield. It was proposed as nuclear warhead delivery method though: https://en.wikipedia.org/wiki/Fractional_Orbital_Bombardment_System https://en.wikipedia.org/wiki/Fractional_Orbital_Bombardment...
- pfdietz 5mo agoUnless a suborbital trip is nearly at orbital velocity, it will involve a high, arcing trajectory. This will make the deceleration at the end unacceptably (lethally) high for all but short arcs. Some of the Mercury suborbital missions involved deceleration of 15 gees, if I recall correctly.
- markvdb 5mo agoFrom 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 5mo agoIt 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 5mo agoThe 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.
- fancyfredbot 5mo agoFor 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 5mo agoWell here's an economic application without nuclear tipped warheads. https://en.wikipedia.org/wiki/Meteor_(missile) https://en.wikipedia.org/wiki/Meteor_(missile)
- throwaway2037 5mo agoThe 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.
- ranger207 5mo agoMissiles versus aircraft is a fight between very high kinetic energy in the missile, and relatively low kinetic energy in the plane, but with the ability to generate more kinetic energy. Missiles don't have a lot of fuel, so they need to generate a lot of kinetic energy to still be effective by the time they reach the target. Typically a missile will accelerate to its top speed in the first few seconds of flight and coast the rest of the way. At very long ranges, all the energy generated when launched has bled off, so there's two common solutions for long-range missiles to generate more energy: a "dual pulse" motor is basically a second rocket motor that fires later in the course; or a ramjet, which can be throttled up and down and is more fuel efficient than a rocket engine.
- Gravityloss 5mo agoRamjets 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.
- pfdietz 5mo agoThere 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).
- flohofwoe 4mo 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 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 https://en.wikipedia.org/wiki/Ren%C3%A9_Lorin
- SEJeff 4mo agoThis is why Ukraine is so excited to get up to 150 Gripens (with Meteor loadout) from the Swedes.
- abbadadda 5mo agoI 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
- pfdietz 5mo agoRamjets 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.)
- throwaway2037 5mo agoAs 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 5mo agoPG celebrates Boom's pivot to power generator supply.
- api 5mo agoI 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 5mo agoI 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 5mo agoSpeed Racer unavailable for comment.