Problems with 6100 mph airliner

[angminas]

http://www.bbc.com/future/story/20121011-new-york-to-london-in-one-hour/1

I'm not an aerospace expert, but I'd be concerned about durability. At that speed, any small problem will become a big problem very quickly. Also, what about heat? I'm reminded of the thermal expansion / fuel leakage problem with the SR-71, but it's not mentioned in this article...why not?

Based on the history of other supersonic aircraft, what challenges would this kind of craft face, and can they be overcome?

 

[BladeVenom]

Military planes will have it first. So most of the problems will be worked out before it enters the civilian market.

 

[IronWing]

I'm not an aerospace expert, but I'd be concerned about durability.

It only has to last an hour.

 

[exdeath]

Not needed. Pretty soon we can 3d print ourselves on the other side of the world in minutes.

 

[Cattlegod]

It only has to last an hour.

that's what she said

 

[Insomniator]

Go for it! we're due for some upgrades in flight besides stupid fuel economy.

The Concord was great... refine it with modern tech. make the tickets not cost a million dollars and I'm sold. Its ridiculous that there are spots in the world that take 20 hours to get to still.

 

[RossMAN]

LAX to SYD in about 1.5 hours? Yes please.

 

[JohnShadows]

you get what you pay for - that works on many levels.

 

[SparkyJJO]

And remember, it would be built by the lowest bidder.

 

[phucheneh]

Soooo...what does one build control surfaces out of, and how do they operate them, at mach 8?

 

[mmntech]

Go for it! we're due for some upgrades in flight besides stupid fuel economy.

The Concord was great... refine it with modern tech. make the tickets not cost a million dollars and I'm sold. Its ridiculous that there are spots in the world that take 20 hours to get to still.

Air travel hasn't changed a heck of a lot since the Boeing 707 went into service 55 years ago. Air travel was still glamorous back then, unlike the unpleasant experience it is today. Nor has it gotten much cheaper.

There have been lots of plans for a new SST (super sonic transport). Boeing had a mock up a few years back. The problem with SSTs is they involve a lot of compromises. Concorde's sleek design that allowed it to travel at mach two limited interior cabin space. Heating is another issue. Travelling at supersonic speeds, even at 56,000 feet, can warp an aircraft's skin. Metal fatigue is a constant problem. You can avoid this by flying higher but radiation becomes an issue, as well as operational costs.

So instead of speed, airlines opted for size and efficiency. There's a reason why the tin sausage has been around for almost 70 years. They carry a lot of payload efficiently. The Boeing 707 was such a damn good design that nobody has seen a need to change it.

 

[Fenixgoon]

Soooo...what does one build control surfaces out of, and how do they operate them, at mach 8?

ceramic matrix composites, or if you want to stick with metals...incolnel 718 or similar. with LOTS of cooling.

i'm sure there are other structural/high-temp alloys that i dont know of, but 718 is "common" for high-temp/structural applications such as jet engines (and even then they have thermal barrier coatings on them)

 

[CA19100]

Air travel was still glamorous back then, unlike the unpleasant experience it is today. Nor has it gotten much cheaper.

Are you kidding?

Look at some 1966 prices, adjusted for inflation, compared to a few flights I looked at for 2/1 on Travelocity:

NYC - LA - $991 in 1966; $149 on 2/1.
Chicago - LA - $717 in 1966; $152 on 2/1.
NYC - DC - $110 in 1966; $60 on 2/1.

And so on. Air travel in the age of competition is dramatically less expensive than it was back then. No question that it's nowhere near as glamorous as it was back then, but there's no denying how much less expensive it is now.

 

[iGas]

Passenger miles per gallon of fuel:

15.8 -- Concorde
93.4 -- Airbus 380
109 -- Boeing 747-400

 

[Red Squirrel]

I wonder if highspeed travel of this nature would be more efficient on ground. Ex: a network of ultra high speed trains. They'd travel in a tunnel system and use magnetic propulsion and simply have wheels all around that will handle any bumps into the walls. The magnetic system would ensure it rarely even has to touch any surface until it needs to stop though. The whole tunnel would be depressurized to minimize air drag. At least it could work for inter-continent travel.

 

[angminas]

I wonder if highspeed travel of this nature would be more efficient on ground. Ex: a network of ultra high speed trains. They'd travel in a tunnel system and use magnetic propulsion and simply have wheels all around that will handle any bumps into the walls. The magnetic system would ensure it rarely even has to touch any surface until it needs to stop though. The whole tunnel would be depressurized to minimize air drag. At least it could work for inter-continent travel.

That's a nice idea, but to me it seems unworkable due to the vast number of things which could go wrong, not the least of which would be tectonic activity and sabotage. And it reminds me of Sewer Shark.

However, if you put it on the surface and you could generate the vacuum within some kind of force field rather than an actual enclosed structure, and you could turn the field on and off where the train is passing, that could be revolutionary. I don't know if the benefits of eliminating drag would outweigh the associated increase in costs, though...that'd be a massive amount of added infrastructure, maintenance, and energy consumption, and one item breaking at any point on the line could cause massive delays.

You might be able to run a few lines per continent like that, if all the bugs could be worked out. Might be a fun ride. 400mph, maybe? I dunno, though...airliner speed that close to the ground...no chance to recover if something goes seriously wrong, unlike a plane. I guess the first thing to do would be to look at the balance sheets of current maglev lines and figure out how much more money you could make for going how much faster.

 

[Merad]

I wonder if highspeed travel of this nature would be more efficient on ground. Ex: a network of ultra high speed trains. They'd travel in a tunnel system and use magnetic propulsion and simply have wheels all around that will handle any bumps into the walls. The magnetic system would ensure it rarely even has to touch any surface until it needs to stop though. The whole tunnel would be depressurized to minimize air drag. At least it could work for inter-continent travel.

In theory it might work, but building so many large pressure vessels would be unimaginably expensive (probably hundreds of billions of dollars, if not more), not to mention that maintenance would be a nightmare.

 

[Lonyo]

Passenger miles per gallon of fuel:

15.8 -- Concorde
93.4 -- Airbus 380
109 -- Boeing 747-400

0 -- Boeing 787 Dreamliner

 

[randomrogue]

They dump billions into X planes and are constantly talking about this one hour flight but nothing ever happens.

 

[KillerCharlie]

Passenger miles per gallon of fuel:

15.8 -- Concorde
93.4 -- Airbus 380
109 -- Boeing 747-400

Exactly. Subsonic flight will always be more efficient than supersonic flight. Unless super cheap fuel is invented, the majority of people will be flying on subsonic transports - supersonic will be reserved for the rich.

 

[phucheneh]

What's the big deal with air drag on a train? Couldn't a train be easily shaped into the optimal low drag object? I'm not sure what the scientific name for it is, but...big sharply pointed dildo? I've heard teardrop, but that's not it; you want the teardrop 'tail' at both ends.

The main force of drag on a train would be the wheels on the track, I'd think. They have the 'maglev' idea, but I would think that would require a huge amount of power.

Oh, and why do people say supersonic flight is not economical? I mean, modern airliners are doing something like 600mph, aren't they? What makes 800mph (mach 1.1-1.2 or so?) so much more unfeasible?

I know there was initial concern when we started trying to break the sound barrier- there were pilots and designers both who thought (or even described experiencing) severe vibrations or complete losses of control. But I thought those were found to be concerns of a more coincidental nature? Basically, our airframes, aerodynamics designs, ect, were simply not up to snuff for controlled 700mph+ flight?

 

[NikolaeVarius]

What's the big deal with air drag on a train? Couldn't a train be easily shaped into the optimal low drag object? I'm not sure what the scientific name for it is, but...big sharply pointed dildo? I've heard teardrop, but that's not it; you want the teardrop 'tail' at both ends.

The main force of drag on a train would be the wheels on the track, I'd think. They have the 'maglev' idea, but I would think that would require a huge amount of power.

Oh, and why do people say supersonic flight is not economical? I mean, modern airliners are doing something like 600mph, aren't they? What makes 800mph (mach 1.1-1.2 or so?) so much more unfeasible?

I know there was initial concern when we started trying to break the sound barrier- there were pilots and designers both who thought (or even described experiencing) severe vibrations or complete losses of control. But I thought those were found to be concerns of a more coincidental nature? Basically, our airframes, aerodynamics designs, ect, were simply not up to snuff for controlled 700mph+ flight?

Aero Student here.

I could probably type out a laundry list of stuff here.

First on the train bit. Maglev is extremely power efficient. No high speed train in the world is going to go and use wheels. Sea level high speed trains are not economically feasible in the US because of lack of stuff to actually connect in the first place.

Supersonic flight isn't economical for several reasons.
1) Enormous fuel costs. Engines are only efficient in fairly narrow regions. Supersonic flight is a whole other ballpark in terms of engine efficiency. You need special fuels and such.
2) Complexity of design
3) Chances that if something goes wrong, something is REALLY going to go wrong
4) Going over mach 1 is an extremely big deal. Current planes go about mach .7-.8 at cruise.
5) I don't want to keep going on about this

 

[phucheneh]

Aero Student here.

I could probably type out a laundry list of stuff here.

First on the train bit. Maglev is extremely power efficient. No high speed train in the world is going to go and use wheels. Sea level high speed trains are not economically feasible in the US because of lack of stuff to actually connect in the first place.

Supersonic flight isn't economical for several reasons.
1) Enormous fuel costs. Engines are only efficient in fairly narrow regions. Supersonic flight is a whole other ballpark in terms of engine efficiency. You need special fuels and such.
2) Complexity of design
3) Chances that if something goes wrong, something is REALLY going to go wrong
4) Going over mach 1 is an extremely big deal. Current planes go about mach .7-.8 at cruise.
5) I don't want to keep going on about this

LOL. I realized after I posted that every sentence had a question mark at the end. Either as a direct question, or some kind of unsure pseudo-statement.

I was just curious as to WHAT the big deal was with hitting mach. As I said, I've watched and read lots of stuff on aviation development during WWII and beyond; the Chuck Yeager years and whatnot. I guess I was under the impression that with proper aero, the sound barrier wasn't some kind of steadfast line that just changed everything.

On maglev- I mean, it would have to take some serious energy to keep the train 'afloat,' so to speak, during stationary phases (which is why they probably don't). I had assumed there's some kind of physics involved that makes the so-called levitation easier at speed. I just need to read more on that subject. I was just assuming most of the forces generated were with electromagnets, and thought, well...thems must be some mighty powerful electromagnets. Permanent magnets (on such high strength) seem like they could pose a safety risk.

Anyhow; wasn't asking for someone to write a research paper to explain some of this tech to me, heh. I'm just doing the internet equivalent of 'thinking out loud,' I reckon. But I like to throw it out there for other people to expand upon and perhaps educate me (and possibly others) a little bit on something that's not in our normal realm of thought.

 

[KillerCharlie]

As soon are you get to Mach ~0.90 and above (and especially around Mach 1), the drag from shockwaves hits you hard - really hard. Modern airliners cruising around Mach 0.7-0.8 have a bubble of supersonic flow along the wing due to the local air speeding up to around Mach 1.1-1.4. When you get to a cruise Mach around 0.90 and higher, you get supersonic flow all over the place and your drag skyrockets. Once you get a bit past Mach 1 the shock drag goes down some, but it's still severe.

Actual flow discontinuities (shockwaves) happen around sonic Machs - as far as the physics go, there actually is this line in the sand. Sure you can just add more thrust to overcome it, but you will always get better gas mileage at Machs less than one.

In addition to that, the sonic booms of large airplanes like the Concorde are very strong. Even with mitigation from a better fuselage and wing design, the weight of a large airplane will have a bigger boom.

It's all about the money. There are a few companies right now looking into supersonic low-boom business jets. (Boeing and Lockheed are each working with a couple NASA contracts right now)

 

[The Boston Dangler]

as long as sonic booms are produced, commercial supersonic aircraft will not fly over land. if they can't fly over land, they can't make money. the concorde has already demonstrated how a vip-only transatlantic shuttle is a money loser.

as for flying twice the speed of an sr-71, i'll believe it when i see it. otherwise, just more flying-car-of-the-future bullcrap.

I'm reminded of the thermal expansion / fuel leakage problem with the SR-71, but it's not mentioned in this article...why not?

the fuel leakage is a design compromise - the skin of the "wet" wings forms the fuel container instead of a discrete tank. this benefits include greater capacity (the entire internal volume of the wing), fewer parts and a means of temperature control for the wing and internal parts. the drawback is that internal components must be made to tolerate living in fuel and it's awfully dirty and sloppy, like a 2-stroke engine.