Comment by rshnotsecure | Hacker News Reader

Comment by rshnotsecure | Hacker News Reader

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They were hitting their limits by the mid 70’s.

The mid 70’s was golden era of supersonic research. Supersonic engines are just regular jet engines with a Turbofan. Add in wings swept further back in a Delta pattern like the Concorde and you have...supersonic aircraft that comfortably can do Mach 1.5-Mach 2.0.

Today, I think there is just 1 functioning wind tunnel in the US that can do supersonic research, so sad. If you live in the Bay Area you pass it, just look at Moffet Field on your way north of San Jose.

The Japanese and Australians, due to their remote location in part, have done most of the significant research of any last few years.

Why did SuperSonics not go anywhere with essentially every major civilian project being mothballed?

1. Materials Science: we simply don’t have reliable data for how long XYZ Metal lasts at extreme temperatures of supersonic flight. If you read Michael Crichton’s Airframe from 1996 (great novel), they mention that aircraft are designed with a lifespan of a human. 80 years. It’s insane how long these things fly. The heat is so extreme, the Concorde would fully extend 1 foot (it was made in part of titanium) during flight. Many crashes have occurred, such as Alaska Airlines Flight 261 in 1999 from Mexico to California, because the maintenance time frames of these parts is still not fully understood. And that’s for subsonics!

2. Noise: No way around it. The decision to build aircraft close to cities was essentially finalized in preparation for World War II. You can dampen significantly, but it is painfully loud. Landing outside the city with fast train back is best solution.

3. Fuel costs and burn. Supersonic research got underway right as Earth Day started. Lots of supersonic tech relies on afterburners, terrible mileage. It was bad timing.

4. 2003 Concorde crash where a tire was hit on the runway, and the entire aircraft exploded. This should have not happened for a tire collision. SuperSonics are fragile because of all the design tradeoffs one has to make (currently).

Previous commenter had it right. Supersonic aircraft have terrible lift/drag. This means that they will always burn much more fuel. Since the extra speed is really only useful for long flights, a supersonic aircraft has to carry a higher fraction of its weight in fuel, further reducing efficiency.

This makes supersonic airliners infeasible for the really long routes that they would truly help with. The Concorde only shaved 3.5 hours off the NY-London time, and cost about 8x as much to operate.

The extremely high costs then mean that you have to sell what are essentially coach seats at greater than business class prices. There aren't many people willing to pay business class prices, so you can't run the planes very often, and you can only run them between very large, rich cities.

Since the whole point of supersonic is speed, you can't effectively sell connecting flights, because if you fly, say, Boston-London through NYC, the direct flight from Boston subsonic will arrive at nearly the same time as the supersonic flight with a connection.

This leads to a very small passenger market. It also means that supersonic planes will operate on an infrequent schedule. Many people in a position to pay for a supersonic flight will prefer a subsonic flight that meets their schedule over a supersonic flight that doesn't.

With the advent of lie-flat beds, in-flight wifi and power, and higher cabin pressurization, being on an airplane an extra 3.5 hours isn't even so bad anymore, so the practical advantage isn't nearly as great.

All of these factors make supersonic a very small niche market. This means that few planes will be produced. High performance aircraft have high development costs, and those need to be amortized over the production run. Concorde was a complete financial disaster because they only produced 14 of them, for all of the reasons above. The only solution is to somehow make the airframe far more efficient.

> With the advent of lie-flat beds, in-flight wifi and power, and higher cabin pressurization, being on an airplane an extra 3.5 hours isn't even so bad anymore, so the practical advantage isn't nearly as great.

I think this is huge. From what I read, the cabin of the Concorde was very cramped. I would prefer business class on a 787 or A380 vs being cramped and arriving faster.

The size of the seats was a little bit worse than what airlines sell today as premium economy.

It's interesting to see what Boom is doing here relative to Concorde. They have a similar sized cabin, but they propose to configure it with fewer but larger seats.

They will have more efficient engines and a lighter airframe, but the lower efficiency at higher speeds means they can't match subsonic range, so they'll have to make a fuel stop on transpacific flights, which hurts comfort and will cost at least an hour per flight. Economically, transpacific routes may make more sense even with the fuel stop. Concorde probably could have done this too, but Air France and British Airways didn't serve these routes. All of the very long routes they might have used it on crossed Europe and Asia where they couldn't go supersonic.

>2. Noise: No way around it.

"The Low-boom Flight Demonstration mission has two goals: 1) design and build a piloted, large-scale supersonic X-plane with technology that reduces the loudness of a sonic boom to that of a gentle thump; and 2) fly the X-plane over select U.S. communities to gather data on human responses to the low-boom flights and deliver that data set to U.S. and international regulators."

https://www.nasa.gov/X59

I thought they no longer did wind tunnel stuff because computer modelling made it redundant

They do as much computer modeling as they can (partially because wind tunnel testing is insanely expensive), but you still need to do some wind tunnel testing to make sure your models were valid.

> 2. Noise: No way around it. The decision to build aircraft close to cities was essentially finalized in preparation for World War II. You can dampen significantly, but it is painfully loud. Landing outside the city with fast train back is best solution.

What are we talking about here, building aircraft or operating them? Factory noise or takeoff/landing/sonic boom noise?

The main reason is actually even more fundamental: Supersonic aircraft have terrible lift over drag.

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