Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

bgr.com

Post reply on HN
Print view View original

141–150 of 196 posts

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

#141

Post by loloquwowndueo »

newsclues wrote: post #139
fancyfredbot wrote: post #126

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 t…

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

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

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

#142

Post by randomNumber7 »

markvdb wrote: post #117

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.

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.

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

#143

Post by Quarrelsome »

newsclues wrote: post #139
fancyfredbot wrote: post #126

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 t…

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

> 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.

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

#144

Post by threwrfaway »

nubinetwork wrote: post #51

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.

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.

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

#145

Post by b65e8bee43c2ed0 »

fancyfredbot wrote: post #126

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 t…

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

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

#146

Post by pfdietz »

Gravityloss wrote: post #127

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 miss…

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).

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

#147

Post by pfdietz »

abbadadda wrote: post #129

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…

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.)

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

#148

Post by pfdietz »

thrownthatway wrote: post #115
m4rtink wrote: post #112

Earlier quoted context omitted.

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.

90 minutes is a low earth orbit period. A suborbital craft won’t be travelling at that speed.

Unless 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.

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

#149

Post by infecto »

deadbabe wrote: post #93
infecto wrote: post #43

Earlier quoted context omitted.

You are not thinking high enough the food chain. I mean heck you have tenured SV engineers cracking $1mm with RSUs. It’s not rare in finance for folks to be hitting $3-5mm with bonus. So that’s what $19k comp a day. If that individual is making $5mm they are more than likely making a multiple of that for the organization.

Well yea great but why do they have to be there so quickly that not even a private jet is good enough? What kind of multi million dollar deal blows up because a dude arrives 18 hours later? And what are they doing when they get there that couldn’t have been done online?

Again, time is money. It’s not about arriving later but the efficiency of time. Many different attributes to consider from sleep, to time optimization or more simply a lot of folks don’t particularly enjoy the long travel and it’s worth the premium. The kind of trips I am thinking about are business related, may only last a day or two with zero buffer before or after.

In business face time still matters. Less than prior to COVID but it still matters. Most boards prefer to meet in person.

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

#150

Post by infecto »

snicky wrote: post #89
infecto wrote: post #43

Earlier quoted context omitted.

You are not thinking high enough the food chain. I mean heck you have tenured SV engineers cracking $1mm with RSUs. It’s not rare in finance for folks to be hitting $3-5mm with bonus. So that’s what $19k comp a day. If that individual is making $5mm they are more than likely making a multiple of that for the organization.

I still don't quite get it given I have never worked high enough or in a big enough corp. What kind of mission a person earning $19k a day have to do at the destination to justify the cost? I imagine to earn this much their main responsibility is to lobby / influence someone important (at dinners, golfing and such). Otherwise, if there are no outsiders involved the whole thing could be just done online. If it's about…

Again thinking too small. Large business dealings are still done in person, who is going to give another entity $50mm or more without meeting in person, having dinner and getting to know the counter party. It’s not about lobbying so much as time in person counts.

Who said anything about 3-4 times a week? There are plenty of businesses with high earners where time matters and I could see flights like these being profitable. Boards meet quarterly typically and they are often preferred to have in person.

Post reply on HN