Why arent faster passenger jets being built?
 

They certainly are becomimg more and more efficent. But the average speed is around 400-500knts Over the last 20 yeas the speeds have mostly have stady the same

First, no one wants it.
Second, even if someone wants it, they are going to charge big time for speed (the faster it travel, the more fuel will be used, ever heard about a few years ago when the fuel was sky high, they are trying to save money, one of the solution is to fly slower?), are you willing to pay for it ? Even you are willing to pay for it, how many people like you are willing to pay more for speed ?

Building an aircraft is not for fun or for a small amount of people, it has to justify the cost to design and build the plane and to make money. Obviously the demand is low, if not Boeing would have built the sonic cruiser by now.

They tried the Concorde and it proved not to be profitable

I would hazard a guess that the cost of any real increase past that "standard" must be... in the view of the airlines/aircraft manufacturers.. uneconomic...

Put it this way.. the last warship I served on was capable of > 30 knots..

..and was powered by 2 LM2500 gas turbines (the marine version of - you guessed it - a jet engine designed for aircraft)

We used ONE of those engines for any speed up to 25 knots IIRC.. the second engine was needed for the relatively small increase to "top" speed...

I suspect aircraft are the same deal.. massive increase in power required past a certain point for relatively modest gain....

Google Boeing Sonic cruiser for the whole story why; bottom line is airlines don't want to buy it as they don't think there is a market -- most pax want cheaper and not faster and won't pay even $1 more. The Concorde sold 16 planes even though it was a tremendous technical success. Boeing decided to build the 787 instead using the Sonic cruiser technology (and cruise speed slightly faster than current planes it is replacing, but >10% slower than the Sonic Cruiser -- but with 20% less fuel consumption).

The technical problem is that air drag increases quadratically just prior to reaching the sound barrier (mach 1). After you surpass it, the air drag decreases again to similar levels as around .8 mach, or even lower. After you surpass the sound barrier, the plane undergoes a lot more stress due to stress on the outside of the plane.

Graph

Wasn't there an idea to travel higher up, thus reducing air pressure (bascially flying outside the atmosphere) and reducing flight times? I think they estimated a now 20hours flight (Europa-Australia) down to 4 hours?

Probably mad science....or only if WARP drive has gone commercial
W

I would imagine too that the sound barrier (mach 1) is an issue. One of the big isses concorde had was that it wasn't allowed to travel over much land because of the sonic boom it created. This restricts the number of routes available a lot. IIRC, planes currently travel at about mach 0.8 - so not too far off mach 1 and the associated sonic boom issues.

The earliest jets were typically somewhat faster than the more recent ones, M.85 or so vs M.82 or so typically now. Fuel efficiency is the reason, and the speed advantages weren't worth much. There are fairly efficient private planes that are much faster (Citation X at M.94) but those speeds are less fuel-efficient than lower ones. Supersonic technologies exist today that would yield fuel efficiency roughly like old 747-100 or so, but the complexity of design and the stress of high speed (Concorde stretched by a meter or so at M1.0 or so cruise, remember?) would make maintenance very expensive and the long range fuel storage is a major issue also. We'll need to wait a couple decades, I'd guess. I had over 300 Concorde flights between Af and BA, and loved the CDG-GIG flights and BAH-LHR-JFK. I still miss them.

Umm, I do! Europe in 3 hours or less, Asia in 6 hours or less from New York? Yes please. Considering the usurious pricing for F tickets as it is, I would rather be there in 1/2 the time if I am paying a ton of $.

Exactly. The SC promised 10 percent faster travel with the same fuel consumption as then-current aircraft. The airlines told Boeing to apply those improvements in engines and airframes to reduced fuel consumption at the same speed instead. (To some extent the SC was also a PR ploy to divert attention from the A380, but that's a separate topic.)

In terms of door-to-door time, faster subsonic travel only makes a noticeable difference on very long routes. Even there, the number of people who would pay more to save 45 minutes between North America and Europe, or an hour between North America and Japan, didn't justify the extra costs.

You may very well want to, but unfortunately for you you're in the minority - The majority of air travellers aren't willing to pay the huge premiums required to get there in half the time.

I *do* think the trend that's we'll see is not faster aircraft, but smaller aircraft that can fly longer distances. Imagine an ETOPS rated 737-size aircraft that can fly between any two points on the globe, non-stop. This will allow airlines to offer more nonstops, which can shave a hours off a journey between a city-pair. For example, if I want to fly YVR -> CDG I need to change planes in London, Toronto, Amsterdam, Chicago etc. There isn't a YVR -> CDG nonstop because the loads don't warrant it - But they might if there was a smaller, fuel-efficient aircraft that could handle it.

If you drive faster in a car, you burn up more fuel. On the other hand, a small engine (for example - a SMART car) can only push a vehicle so fast.

So ultimately, a faster vehicle (car, ship, plane) needs a larger engine that burns more fuel. To get an incremental increase in speed though requires a disproportionate increase in power. More power being used = more fuel being burned. Additionally, a more powerful engine is probably somewhat more complex so maintenance becomes an added issue.

Personally I would consider paying more if I could fly say, YYZ - HKG in 7 hours instead of the current 15+ hours. But I know that I don't represent the majority of flyers.

The Concorde used as much fuel as a 747, but only carried 100 passengers and no cargo. It's certainly possible that a new design would use less fuel, but there's still going to be a penalty.

The high fuel burn also limits the range, which means that routes that would really benefit like LAX-HKG are out of range. JFK-HKG would benefit even more from a supersonic flight, but you can't fly supersonic over land.

Flying higher creates complications for pressurization. You need a heftier structure to contain the pressure, plus you have to provide for depressurization. At 100,000ft, an oxygen mask won't cover it -- you'd need something more like a spacesuit.

(Lack of) Technology is preventing this. You need an a/c that can power itself from ground at slow speed (or have to build launchers) and climb as well as increase speed fast enough to get into sub-orbit, and there's less oxygen/air at higher altitude for combustion. Either that involves carrying two engines (a conventional jet and then some sort of rocket engine or a SCRAM jet - designed for high-altitude high-speed travel) or have a hybrid engine that combines the properties of a conventional jet and a SCRAM jet. That hybrid hasn't been designed yet and SCRAM jets are still in their infancy.