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

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

#191

Post by seabass-labrax »

pfdietz wrote: post #190
seabass-labrax wrote: post #188

Earlier quoted context omitted.

It would still be possible to fly a predominantly ballistic trajectory, yet use rocket propulsion to decelerate whilst still outside the atmosphere. It would require a huge amount of extra fuel compared to a purely ballistic trajectory, but perhaps still less than achieving a full orbit and de-orbiting again for some destinations.

At global distances a fraction orbital trajectory would use less total rocket delta-V. More practical would be a trajectory that was a series of small suborbital arcs with skipping off the atmosphere (perhaps with some airbreathing propulsion during the skips.) The thermal protection can cool by radiation between the skips.

That would be very cool to witness! SABRE sounds like it would be an ideal engine for that application.

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

#192

Post by fragmede »

throwaway2037 wrote: post #158
fragmede wrote: post #68

Earlier quoted context omitted.

Shorter, no, but having a private cabin with a shower, and a lounge with a bartender on the plane, not to mention Starlink, would make those 12 hours a lot more bearable vs 12 in an economy seat.

> having a private cabin with a shower AFAIK: Showers are only available to first class customers flying via the major Gulf carriers. I checked Google flights for business class and first class tickets between Tokyo and London. Business is about 5,000 USD and first class is about 10,000 USD. Assuming that we are talking about first class here (to satisfy your shower requirement), what kind of developer is hacking cod…

Mitchell Hashimoto's got tres commas in his bank account and his own jet. He doesn't need to take commerical, or even first class. If we backsolve, say $10,000 is a once a month purchase, and $10,000 for a hotel and you stay a month. Say your other living expenses are $10,000/month, so we're shooting for spending $20,000/month. With the recommended shaving off 3% the nest egg, (20,000 * 12) / 3% gets us $8 million in the bank.

So at $8 million in the bank, you could take a $10,000 plane trip, stay for a month, spend $10,000 on a hotel, take a $10,000 flight back. Still upper end of net worth, but nowhere near Mitchell Hashimoto territory.

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

#193

Post by rdl »

deadbabe wrote: post #37
rdl wrote: post #28

Earlier quoted context omitted.

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 on…

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

If a fund can get into the Anthropic Series A vs. not get into the Anthropic Series A based on a flight to meet with the team, that is worth buying the supersonic plane even if you scrap it after.

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

#194

Post by musicale »

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 super fast missiles far scarier than advanced AI

But what about super fast missiles with advanced AI?

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

#195

Post by rbanffy »

nine_k wrote: post #42
kelseyfrog wrote: post #31

Earlier quoted context omitted.

How long of a weightlessness period does this entail?

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

I would say windows would be a non negotiable design requirement, as well as external HDR cameras for the middle seats.

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

#196

Post by SEJeff »

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…

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