Proposed Lapcat II Hypersonic Airliner: Brussels to Sydney in Less Than 3 Hours

New submitter AG_2011 writes: Could an airliner that flies anywhere in under 3 hours be in service by 2030? One estimate puts the cost one way at €5,000 (£3,700) per seat for a Brussels to Sydney trip. The Lapcat-II project's Mach 8 airliner will be capable of 8,500 km/h (5,280 mph) and could take passengers on this trip in 2 hours and 55 minutes. The race is on...

Comments

So: nine hours from Brussels to Sydney

[Anonymous Coward]

Three hours: airport security checks

Three hours: flight time

Three hours: customs

Not bad. Not bad at all.

Re:So: nine hours from Brussels to Sydney

[turbidostato]

And then, at five grands a-pop don't expect you have flights each hour, so add up "waiting for next flight".

Doesn't look as if it can go against private jets/flights which seems the natural competitor here.

Re:So: nine hours from Brussels to Sydney

[OzPeter]

Three hours: airport security checks

Three hours: flight time

Three hours: customs

Not bad. Not bad at all.

You'd think that if you had an airline charging >5k euros per one way ticket, that they would have already paid off the right people in order to expedite security and customs. But even still as it is it doesn't take 3 hours to get through customs in Australia .. unless you are attempting to bring in some contraband. This isn't LAX after all.

Re:So: nine hours from Brussels to Sydney

[sycodon]

All things considered, I think I'd rather take 2-3 weeks on a cruise ship to get the Australia.

Re:So: nine hours from Brussels to Sydney

[Anonymous Coward]

Don't eat the tapioca... or the potato salad. And have plenty of Lomotil handy. By the time you arrive, you should have recovered.

Re:So: nine hours from Brussels to Sydney

[currently_awake]

Anyone who can afford this can afford to bypass the security lineup.

Re:So: nine hours from Brussels to Sydney

[ShanghaiBill]

But even still as it is it doesn't take 3 hours to get through customs in Australia

It doesn't in America either. At SFO the time from wheels-down to walking out the door is typically about 40 minutes to an hour.

Pro-tip: Fly non-American airlines. If I fly from Shanghai PVG to SFO, I will clear customs much faster if I fly Air China than if I fly United. Why? Because American airports have separate customs lines for America citizens/residents and non-residents. A United flight is typically 80% Americans and 20% Chinese. The Air China flight is the reverse. So I spend far less time waiting in line. Besides, Air China has better food, and way cuter stewardesses.

Re:So: nine hours from Brussels to Sydney

[ShanghaiBill]

Anyone who can afford this can afford to bypass the security lineup.

How does money help you bypass TSA? I mean legally.

Re: So: nine hours from Brussels to Sydney

[donscarletti]

Air China stewardesses look like hotel maids, especially when they put the apron on. They put all the attractive ones on international flights, so you tend to see an over representation of pretty girls, but they still dress in that same ugly uniform. China Eastern and China Southern mostly look pretty on whatever route though.

Re:So: nine hours from Brussels to Sydney

[Dutch Gun]

Chartered flights aren't subject to the same security regulations as normal passenger airlines.

Re:So: nine hours from Brussels to Sydney

[postbigbang]

And the acceleration g-forces, coupled to the de-accelaration forces means you have five minutes during the flight to go to the loo. Please don't stand in the aisles whilst you wait.

Re:So: nine hours from Brussels to Sydney

[PopeRatzo]

All things considered, I think I'd rather take 2-3 weeks on a cruise ship to get the Australia.

I'm not going back there until they get rid of all the death adders.

http://www.independent.co.uk/e...

I had a nice time when I was there last, but I didn't realize then that every form of wildlife in Australia wants to kill you. Now I know better. Even the pigeons have venom that will make you die a slow, painful death.

Re:So: nine hours from Brussels to Sydney

[Anonymous Coward]

its true bro, dont forget about our snake ridden toilets, or venomous birds

Re:So: nine hours from Brussels to Sydney

[Anonymous Coward]

But even still as it is it doesn't take 3 hours to get through customs in Australia

Pro-tip: Fly non-American airlines.

Sure, Ryan Air is great!

Re:So: nine hours from Brussels to Sydney

[Anonymous Coward]

Chartered flights aren't subject to the same security regulations as normal passenger airlines.

Yep. Meaning you could fill one with high explosives and fly it into the new World Trade Center fairly easily. If you plan to do intelligence analysis, you should always start with the idea that what they wanted to achieve has already been achieved, if there has not been additional enemy action.

Re:So: nine hours from Brussels to Sydney

[Anonymous Coward]

I have heard that small private charters are not a bad deal if you can fill the plane, but solo fliers of the target type are going to just fly first class.

Doing a quick check, a first class one way ticket (Emirates) is already 4400 euros.

Re: So: nine hours from Brussels to Sydney

[Anonymous Coward]

TSA is an American thing, so flying from Brussels took Sydney you've already bypassed then.

I took an international trip on a Boeing 777 a few weeks ago. No body scanners, just a standard walk through metal detector.

Re:So: nine hours from Brussels to Sydney

[dryeo]

but I didn't realize then that every form of wildlife in Australia wants to kill you

Oh bullshit. Everyone knows that some of the sheep are harmless.

Re:So: nine hours from Brussels to Sydney

[Anonymous Coward]

As a Brussels resident, I must say that I am confused. First of all I don't know where they intend to land it. Zaventem has no room for expansion and "Brussels South" is really just a dingy RyanAir airport over an hour away from the city in a post industrial shithole called Charleroi. Then there is the route: Unless they intend to loop out over the north sea and go over the north pole, the thing will pass over the most populated areas in the world, and I promise you that will remain subsonic.

Re:So: nine hours from Brussels to Sydney

[Anonymous Coward]

but I didn't realize then that every form of wildlife in Australia wants to kill you

Oh bullshit. Everyone knows that some of the sheep are harmless.

But are they the pretty ones?

Re:So: nine hours from Brussels to Sydney

[Anonymous Coward]

... you have five minutes during the flight to go to the loo

I think very few people are qualified to go to the loo in space. Space flight would also be an extra cost in construction and operation (oxygen, heating, humidity reduction), so I can't see these planes being space-worthy (and they're not; sporting air-breathing ram-jets). When a plane is in the atmosphere it has to deal with friction and heat, so constantly changing the velocity is a dumb idea. Like modern planes they will want to reach cruising altitude and velocity in a couple of minutes.

Re:So: nine hours from Brussels to Sydney

[GNious]

Don't know about Sydney, but at Brussels Airport you can get through Security in under 2 hours most days, and customs in under 30 minutes.

Yes, you were trying to be funny and all....

Re:So: nine hours from Brussels to Sydney

[CrimsonAvenger]

Funny. Slightly.

At half a gee acceleration, it'll take about 8 minutes to reach cruising speed. It'll probably take longer to slow down, say 25 minutes....

Re:So: nine hours from Brussels to Sydney

[PopeRatzo]

Oh bullshit. Everyone knows that some of the sheep are harmless.

That's what I thought, until one gave me gonorrhea.

Re:So: nine hours from Brussels to Sydney

[turbidostato]

"Doing a quick check, a first class one way ticket (Emirates) is already 4400 euros."

Yes, but how many first class seats load that plane? Those 5000 (or more) are for all of the seats. The result is a new Concorde, which, it seems, was never profitable.

Re:So: nine hours from Brussels to Sydney

[K. S. Kyosuke]

That's only because the ozone hole made some of them blind.

Re:So: nine hours from Brussels to Sydney

[Anonymous Coward]

What's your name and social and full address? That way, we can put you on the No Fly(tm) list, which ensure a full Anal Probing(R) whichever flight you take.

--sf

Re:So: nine hours from Brussels to Sydney

[Kyogreex]

I have heard that small private charters are not a bad deal if you can fill the plane, but solo fliers of the target type are going to just fly first class.

Indeed. People seem to have an image in their heads of rich people always flying private, but the reality is that that private makes less and less sense the greater the distance being traveled (at least without stopping), where the aircraft required are considerably more costly to own and operate. There's a reason why Emirates and other carriers do offer such options, and why some American carriers offer first class on New York to LAX flights.

Re:So: nine hours from Brussels to Sydney

[pepty]

I think the market for hypersonic planes would be more B.C. to Beijing than S.F./L.A to NYC. For one thing: the flights will probably have to be over water the entire time they are above the speed of sound.

Re:So: nine hours from Brussels to Sydney

[AK Marc]

Supersonic at high enough altitudes will be inaudible. That's what I've seen the proposed services of this kind counting on.

Re:So: nine hours from Brussels to Sydney

[quenda]

Besides, Air China has better food, and way cuter stewardesses.

Try Thai Airways. Even the stewards are cute.

Re:So: nine hours from Brussels to Sydney

[quenda]

every form of wildlife in Australia wants to kill you.

The real danger is in the water: great white sharks, crocodiles, blue-ring octopus, stonefish, etc. (Not to mention all the tourists that drown every year.)
Land is actually quite tame - no lions, bears, wolves or tigers. No large land predators at all. I'll take my chances with a death adder over a grizzly bear any day, at least since they invented anti-venom.

Re:So: nine hours from Brussels to Sydney

[PopeRatzo]

Land is actually quite tame - no lions, bears, wolves or tigers. No large land predators at all.

What about the yowie?

Re:So: nine hours from Brussels to Sydney

[stoatwblr]

Bunyips and dropbears spring to mind as potential dangers too.

Re:So: nine hours from Brussels to Sydney

[Anonymous Coward]

Not to mention Vegemite!

Brussels to Sydney

[turkeydance]

who would want to do that?

Re:Brussels to Sydney

[Anonymous Coward]

Real men fly from Shanghai to Buenos Aires.

Re:Brussels to Sydney

[OzPeter]

who would want to do that?

Let's see. Right now the shortest commercial flight Brussels to Sydney is about 22 hours. I don't know if you noticed, but 3 is a lot less than 22, and some people have a lot more money than the $1600 needed for the current return ticket prices. And a fair share of these people travel all over the world.

Re:Brussels to Sydney

[GoodNewsJimDotCom]

I think he was making a joke that anyone with enough money to fly on this plane isn't going to want to go to a country where 15 or the 12 deadliest snakes and spiders live.

Re:Brussels to Sydney

[OzPeter]

2nd reply because I forgot about this for a moment.

Come to Australia

Re:Brussels to Sydney

[Anonymous Coward]

LOL, the intersection of those groups is so small as to be meaningless. Either way, we're talking about going halfway around the world in less than a day. If you're that impatient, nothing will satisfy you.

And the time zone difference will mean that you'll arrive smack in the middle of the opposite part of the day you left. You're gonna have to sleep that off somehow, so who cares???

It's a technology with no future.

Re:Brussels to Sydney

[OzPeter]

LOL, the intersection of those groups is so small as to be meaningless. Either way, we're talking about going halfway around the world in less than a day. If you're that impatient, nothing will satisfy you.

By your reasoning there is also no rationale for business or first class fares on flights as it doesn't matter how much you pay as you still get there at the same time.

and as for your timezone comment, lots of people transition their sleep by 12 hours all the time .. its called rotating shift work

Re:Brussels to Sydney

[sycodon]

Australia:

Where the Women are pretty, the Men are drunk, and everything in Nature wants to kill you.

Re:Brussels to Sydney

[rtb61]

I got no idea where all that came from, except possibly as an Australian Government misinformation campaign because they were having to reject too many American applicants and the Americans were getting nasty about it but http://www.bobinoz.com/migrati.... I mean seriously grizzly bear versus koala bear which would you rather meet out in a forest or mountain line versus Tasmanian devil, sure the devil sounds worse, much worse but not really a problem.

Re:Brussels to Sydney

[0123456]

And the time zone difference will mean that you'll arrive smack in the middle of the opposite part of the day you left. You're gonna have to sleep that off somehow, so who cares???

Me. I'd rather sleep in a hotel bed than on a plane. Even the planes with seats that fold down into beds still aren't very comfortable.

And the prices quoted here are about the same as my last transatlantic first class flight. Though I'm sure the real numbers would be several times as high.

Re:Brussels to Sydney

[ShanghaiBill]

is a lot less than 22, and some people have a lot more money than the $1600 needed for the current return ticket prices.

The Concorde proved that there are actually very very few people willing to squander thousands of dollars to save a few hours. The Concorde was only kept alive by taxing middle class working people in France and Britain, in order to subsidize millionaires jetting across the Atlantic. It was never close to being economically viable without those subsidies. Living in Silicon Valley, I know quite a few people that are well off and could easily afford this. But they are also some of the cheapest bastards alive. They didn't get to be rich by wasting their money on frivolities.

Re:Brussels to Sydney

[Anonymous Coward]

Any city in the US to Hawaii in 1 hour.

Sign me up!

Re:Brussels to Sydney

[Grishnakh]

It's not the koalas and kangaroos which want to kill you (though the kangaroos can punch you in the face and knock you out).

It's the giant spiders, poisonous snakes, and crocodiles. I believe, however, that the really dangerous stuff like this is mostly in the northeastern part of the country.

Re:Brussels to Sydney

[PopeRatzo]

And, it's getting worse every day:

http://www.independent.co.uk/e...

This thing is so poisonous, that I get queasy just seeing it's photograph.

Re:Brussels to Sydney

[phantomfive]

I would, but the price is kind of expensive.
If they added it to other routes, I would be even happier.

Re:Brussels to Sydney

[phantomfive]

You're gonna have to sleep that off somehow, so who cares???

Better to sleep 8 hours than 22 hours.

Re:Brussels to Sydney

[Anonymous Coward]

It is photograph?

Re:Brussels to Sydney

[pollarda]

Because they want to go to the Opera?

Let's see.... If you wanted to go to the Sydney Opera (assuming an 8pm show) you would have to leave your house in Brussels at .... 5am. (two hours to get to the airport, three hour flight time, two hours to get to the opera house plus the 8 hour time difference.) This is of course assuming there is a flight that happens to correspond with the Sydney Opera House's schedule which is reasonably likely if for no other reason it doesn't make sense to be arriving in the middle of the night if it can be helped...

As I recall, <strike>Lady Galadrial</strike> I mean Cate Blanchet is directing nowadays.

Re:Brussels to Sydney

[Anonymous Coward]

... though the kangaroos can punch you in the face and knock you out.

They can also stand in a billabong (pond) and drown shorter animals.

... giant spiders, poisonous snakes, and crocodiles

Snakes and spiders like buildings but travel slowly. The real danger is animals that can fly into a city, such as bats. Their saliva contains the Lyssa virus (a mild and usually fatal form of rabies).

... mostly in the northeastern part of the country.

Australians have an urbanized lifestyle, contrary to the tourist brochures, so the likelihood of facing a dangerous animal is low. Plus, most of those deadly predators hunt small animals and and want to run from large animals like humans, cows and horses.

Re:Brussels to Sydney

[multi io]

I got no idea where all that came from, except possibly as an Australian Government misinformation campaign because they were having to reject too many American applicants and the Americans were getting nasty about it but http://www.bobinoz.com/migrati.... I mean seriously grizzly bear versus koala bear which would you rather meet out in a forest or mountain line versus Tasmanian devil, sure the devil sounds worse, much worse but not really a problem.

Yeah, but then whenever I'd discover one of these in my room I'd have to burn the house down and be homeless afterwards, which is not so convenient in a place with so many free-running monsters.

Re:Brussels to Sydney

[thegarbz]

who would want to do that?

People who appreciate warm winters, hot summers, beautiful blue skies, and endless beaches.

Re:Brussels to Sydney

[Aereus]

Oh don't worry, the kangaroo will kill you too—threaten one near a watering hole and chase after it into the water... it'll suckerpunch you in the gut and hold you under until you drown, no problem.

Re:Brussels to Sydney

[Anonymous Coward]

Ever been to Brussels?

Re:Brussels to Sydney

[Anonymous Coward]

Your description applies until the early 80s, when BA realized that they could charge more and still get the same number of passengers. There are not many people willing to spend a lot of money on flights, but those that do, are willing to spend way more. The Concorde was operated at a profit in the second half of its life. The question is can a new plane not blow too much money on development, because then there definitely is enough of a market that a business could plan around.

Re:Brussels to Sydney

[Grishnakh]

Their saliva contains the Lyssa virus (a mild and usually fatal form of rabies).

Surely they've come up with a vaccination for this?

Australians have an urbanized lifestyle, contrary to the tourist brochures

Any idiot should know that the vast majority of the population there lives in one of a handful of cities (Melbourne, Sydney, Adelaide, Brisbane, Perth). That's really not too different from most industrialized nations. Most Americans live in cities too. We don't have quite the concentration though, or a giant area of completely uninhabited land in the middle, but the American West does have some pretty barren parts in Nevada, Utah, etc.

so the likelihood of facing a dangerous animal is low.

It's no different here. We don't have deadly grizzly bears running around east-coast cities; they're all in rural places like Yellowstone National Park (in Wyoming, a western state with only 500k inhabitants despite a rather large geographical size).

Re: Brussels to Sydney

[Anonymous Coward]

I'm Australio-Belgian, you insensitive clod!

Re:Brussels to Sydney

[ewibble]

I think Brussels to Sidney is just an example, of a long flight, They will have any route that is economically feasible.

Re:Brussels to Sydney

[stoatwblr]

"some people have a lot more money than the $1600 needed for the current return ticket prices"

You'd have to attract the people who are currently paying for first class - which is about $10-15k a seat on these distances.

Some of them want the pampering, others would pay that much to get there sooner even if they had to sit on orange crates.

That's nice but total travel time is a bitch

[Kjella]

The actual plane ride is actually quite nice. You can get up and stretch your legs, get refreshments and whatnot. The crappy part is getting to the airport, check-in, security control, boarding, disembarking, waiting for luggage, getting from the airport and so on. Going to the capital is ~50 minutes flight time, but in practice city center to city center it's 3.5-4 hours. Now I suppose for the really, really, really long flights this could be an advantage but for the somewhat shorter trips within 1000 km I'd rather see end-to-end high speed rail.

Re:That's nice but total travel time is a bitch

[Anonymous Coward]

This is mostly an America thing. Most other countries airports are nowhere near as much of a nightmare.

Re:That's nice but total travel time is a bitch

[sk999]

Breakdown of timing for my most recent flight (yesterday):

Travel time to airport: 90 minutes (normal time 20 minutes, but it was rush hour. A Taylor Swift concert on the way was not a problem.)
Time in airport, including ground hold time due to weather at destination: 210 minutes (normal 60 minutes)
Actual flight time: 70 minutes (normal time 50 minutes)
Time from touchdown to exiting the parking lot: 90 minutes (normal 30 minutes - airport operations stinks late at night)
Drive home: 90 minutes (normally 60 minutes, but weather and detours factored in).

Basically, 9 hr total travel time for a nominal 50 minute flight. Driving time is slightly shorter.

Re:That's nice but total travel time is a bitch

[Greyfox]

I run into that every time I go to DIA. No matter how you arrange it, it's always going to cost neighborhood of $60 and take about an hour to get there. Parking for three days there cost nearly as much as a round trip ticket to Phoenix.

I live next door to a municipal airport and talked to a pilot there about just flying down to the big airport. I'd have to pay for the plane rental and pilot's time by the hour, but that's actually pretty reasonable. Meaning a round trip could cost less than parking a car there for a week. Apparently the gate fees at the airport will run you at least a couple hundred bucks, though.

Re:That's nice but total travel time is a bitch

[Anonymous Coward]

Basically, 9 hr total travel time for a nominal 50 minute flight. Driving time is slightly shorter.

Hence why my rule of thumb is that if it'd take 8 hours or less to just drive directly there then I'll do so.

Re: That's nice but total travel time is a bitch

[Anonymous Coward]

I guess I've always been lucky then. I routinely travel on 2-4-hour flights. I average about 45 minutes from my door to the gate, wait 30 minutes to board (time I buffer in just in case), etc. I'll fly out in the morning, do a day of work, and fly back in time for a late dinner if I'm lucky. My wife often has to decide between driving for 4 hours one way or flying for maybe an hour, which is a harder decision. I clearly live closer to airports than most but I haven't had the nightmares you guys are talking about.

Re:That's nice but total travel time is a bitch

[Harlequin80]

Wow that is seriously fucked for such a short flight. Brisbane to Sydney is a 1hr5 flight. With only carry on my day looks like this.

Travel time to airport: 30 minutes
Time in airport: 45 minutes (you can board up to 20 mins before flight for domestic and security is straight forward, you precheck in online and have your boarding pass pre-printed)
Flight: 65 min
Touch down to train: 15 mins
Train to cbd: 35 mins

Driving time - 11-13 hours.

I do that there and back in 1 day for work regularly.

Re:That's nice but total travel time is a bitch

[Anonymous Coward]

It's pretty common for Canberra - Sydney to take longer by plane than by car.
It only takes one delay and you could have driven.

Of course, there's a lot to be said for _not_ having to spend three hours driving, and then deal with Sydney traffic, so it's probably worthwhile even if flying ends up taking twice as long as driving.

The ultimate answer would be high-speed rail. Canberra to Sydney in under an hour without airport bullshit.

Re:That's nice but total travel time is a bitch

[AK Marc]

I took a domestic 60 minute flight for a while. 1 hour to the airport (rarely are they convenient, but are all on the outskirts of town, I'm on the wrong side). 5 minute check in, 5 minutes security, 5 minute walk to gate, sit at the gate for 20+ minutes (even with less than 15 minutes from edge of airport to gate, check in still closes 30 minutes before the flight). 60 minute flight. 5 minutes to get to luggage carousel, 5 minutes to get bag, 0 minutes for taxi, 15-30 minutes to destination. Train for the same destination is about 8 hours, drive is 12+ hours.

But when I worked a place with offices in Dallas and Houston, I'd drive. I was the only one in the company who regularly drove it. Everyone else flew. The time office-to-office was about the same either way.

Can't even keep London to New York in 2 hours

[TWX]

Until we can keep reliable low-supersonic passenger service flying, I'm really not going to worry about the hype of hypersonic.

Give me LA to London in six hours for a price I'm willing to pay as an already frequent flyer, then we'll start talking.

Re:Can't even keep London to New York in 2 hours

[Anonymous Coward]

Actually, the economics of supersonic flight aren't there; the fuel cost v.s. time saving isn't that big. However, the ability to turn a super-long flight into a short flight has a different market.

Re:Can't even keep London to New York in 2 hours

[TWX]

Per-passenger might be a different market, but there's still program costs that have to be paid. Normally those costs are paid for by amortizing over the sale of aircraft. The purchase of the aircraft have to be paid, by amortizing over the sale of airfare.

I do not see enough passengers to justify enough planes to justify development costs. I don't doubt that there is a market for same-day passenger service to anywhere on the planet, but that market is too small to drive development of the equipment to make it possible. Even among the rich, there are only so many people that would want or need service like this, and most of them probably can't justify the $5000/trip cost to work weekdays at the office in Singapore and to see their families on the weekend in New York.

For just about anyone else going vast distances, there's usually time available to account for the travel.

Re:Can't even keep London to New York in 2 hours

[tsotha]

I do not see enough passengers to justify enough planes to justify development costs.

There weren't enough to justify the development of the original passenger airlines - the jet engine itself would probably never have been developed if it didn't have military applications. If this plane has to rely on passenger fares to pay for development it will never fly.

A good use for hydrogen

[WalksOnDirt]

This one of the few good uses for hydrogen fuel that I've seen other than rockets. However, I suspect it will be too loud for passenger traffic. The Concorde was notoriously noisy, even aside from the sonic booms it created.

There are few flights long enough for this to be worthwhile, especially if the courts limit the areas they can travel at transonic speeds. At the least, I would want government involvement minimized.

Re:A good use for hydrogen

[Anonymous Coward]

Hydrogen is a terrible fuel. It has no good uses.

Re:A good use for hydrogen

[Brett Buck]

Hydrogen is a dead loser as an airplane fuel - FAR too bulky/not dense enough. Look up the "suntan" project.

Re:A good use for hydrogen

[Anonymous Coward]

Depends. Are you making H2O or He?

Re:A good use for hydrogen

[serviscope_minor]

Hydrogen is a dead loser as an airplane fuel - FAR too bulky/not dense enough.

That must be why it's the most efficient choice for getting to space then...

Re:A good use for hydrogen

[Anonymous Coward]

When you look at the amount of fuel burned for what's being lifted, it's awful, yes. Which is why the Saturn V used kerosene.

And there's nothing important about getting to space, except for Space Fundamentalists.

Is there a reason you always post such nonsense?

Re:A good use for hydrogen

[Anonymous Coward]

The Saturn V used RP-1 only for the first stage and hydrogen for later stages. This mostly comes down to the final size as kerosene is denser than LH2, but it adds to engineering issues and requires additional components, e.g. fuel pressurization, and in case of S-IC, insulation to prevent freezing from the LOX pass through. LH2 is still more efficient, fuel efficiency is not the only constraint.

Re:A good use for hydrogen

[Anonymous Coward]

Going close to the edge of space, basically on a rocket booster, then gliding down would be the fastest way to get there.

Re:A good use for hydrogen

[WolfWithoutAClause]

Not sure about the Mach 8 version, but the Mach 5 LAPCAT A2 has extraclever turbofan engines, so should be quite quiet and efficient subsonically, and then when they're out over the ocean, they can turn it up to 11 and go Mach 5.

Re:A good use for hydrogen

[WolfWithoutAClause]

Nah, it's fairly practical, you just end up with a big aircraft. The only real problem is finding a big enough runway. Similar problems with the A380 faced.

There's also cost, it's not a cheap fuel; but on the upside it has twice the energy per unit weight and it's a marvellous coolant.

R&D?

[jklovanc]

One estimate puts the cost one way at €5,000 (£3,700) per seat for a Brussels to Sydney trip.

Does that price include any amortized R&D expenses? I somehow doubt it.

Re:R&D?

[tlambert]

One estimate puts the cost one way at €5,000 (£3,700) per seat for a Brussels to Sydney trip.

Does that price include any amortized R&D expenses? I somehow doubt it.

No, but if you read the article, you'll already know that it includes the hydrogen fuel costs, with the hydrogen not being derived from methane.

Favorite Two Sentences from the Article

[R3d M3rcury]

If the hydrogen can be sourced from natural gas, instead of from the electrolysis of water, the airfare tickets of a hypersonic trip could drop to about half the price of a business-class ticket.

Based on current projections the ticket price will be about three times more expensive on average than current business-class subsonic tickets.

Yes, these two sentences followed each other. There was no editing.

So the cost could be about half as much, but they'll charge three times as much because they can. I suppose I can't blame them--if I was in Brussels, I'd probably pay three times the going rate to get to Sydney.

Re:Favorite Two Sentences from the Article

[ClickOnThis]

The editing is clumsy, but I don't think there is any contradiction. I read it thus:
- if they can get the hydrogen from natural gas, then a ticket will cost 0.5 CBCT (Current Business Class Ticket);
- otherwise, if they have to rely on electrolysis to get the hydrogen, then the cost is 3 CBCT.

Re:Favorite Two Sentences from the Article

[ClickOnThis]

The editing is clumsy

Not your (non-)editing R3d M3rcury, theirs. Thought I should clarify that. ;-)

Wrong news site

[Anonymous Coward]

Should be on $. news for the rich who can afford such things :|

Re:Wrong news site

[ClickOnThis]

Should be on $. news for the rich who can afford such things :|

Cashdot: News for the wealthy, stuff that's expensive?

Re:Wrong news site

[Anonymous Coward]

What, you didn't by bitcoins at 0.05$ apiece when Slashdot talked about it years before the mainstream press?

For future reference,

[Beck_Neard]

So that everyone can have an informed opinion about this, the laws of physics of high-speed travel are quite simple. The lower the lift-drag ratio of your craft (at cruise speed at level flight), the more fuel you have to consume per mile. The problem with supersonic travel is that at supersonic speeds, high lift-drag ratios become virtually impossible. A 747 has a L/D ratio of over 25; the Concorde had a L/D of about 7 at Mach 2 (and it was a pretty efficient, low-drag design). The best supersonic designs I'm aware of achieve a L/D of around 9 at L/D at Mach 1.5. These are incredibly optimized designs that have been fine-tuned with supercomputers and would be quite unfeasible for a passenger aircraft (weird shapes, no windows, etc.) As a result the Concorde consumed about 3x more fuel PER MILE than a comparable subsonic jet. So half the mass of the Concorde was fuel (!), it winded up being very heavy, and it carried only 100 passengers. And its maximum range was limited to 4500 miles.

And if you look at a craft like the SR-71 blackbird, it fits the same pattern. It had a L/D of about 6 at cruise speed (Mach 3.2), 60% of its mass was fuel, and it could only go about 3000 miles before requiring refuelling.

At hypersonic speeds, it's even worse, as various laws start catching up with you and limiting your theoretical L/D to about 4 or 5. If you're running on typical jet fuel, forget London to Sydney. Such a craft could barely make it from London to Athens. So because of that, they're suggesting hydrogen. Which is both hilarious and also firmly puts this idea in the realm of 'things that are never going to happen.'

Re:For future reference,

[Anonymous Coward]

I agree completely. What you say makes perfect sense. It seems to me that the only way to guarantee delivery of passengers to any spot on the globe in 3 hours or less must necessarily involve orbital space flight. The passenger space craft lifts off and enters orbit, shifts orbits to match a re-entry trajectory that terminates at the delivery point and then de-orbits and lands at the designated coordinates. Of course, such a craft, if it could even be built, would be many times more expensive than the Concord which was itself a complete flop from an economic standpoint. This whole article is a classic example of how some nerds have just about zero sense when it comes to issues of money or economy. Supersonic passenger flights are not economically viable with current technology and I haven't seen anything that looks set to change that anytime soon.

Re:For future reference,

[ClickOnThis]

Interesting post, but one thing: did you consider the fact that they plan to fly at altitudes well above 33 km? The air is a lot thinner up there.

Re:For future reference,

[Anonymous Coward]

Concorde suffered from being small - with limited volume and so poor number of passengers for overall weight (about 1passenger per dry tonne, versus about 2 for a large airliner) A larger SST could get to similar 2 passengers per tonne figures with more internal volume available.

Concorde B (minor wing and engine changes, never built due to halt in production) would have lifted range about 10-20% from Concorde. L/D about 7.5. Modern jets are not 25, more like 21-22, so yeah about 3x, though a new Mach 2 SST might get L/D up to 8 or 9

But cost of travel is about 1/3 fuel, 1/3 capital and 1/3 staff. Travel 2.5 times as fast (concorde) and capital costs are reduced by about half as are staff costs. Optimised Mach 2 engines are also far higher efficiency than subsonic engines due to higher efficiency of inlet air compression so fuel costs are only about 2.5x and overall cost about 1.2-1.3x. That is affordable. You are also only in the air for 3-4 hours at a time, so don't need to provide for high staff headcounts and sleeping spaces or meals as on long-haul flights.

Change to LNG as a fuel and you can lower fuel costs and increase range by 20-30% and might be even cheaper than conventional jets.

Also we now have a raft of improvements since 1970's - like building from lighter stiffer stronger carbon fiber, improved higher temp engines, better control systems, no need for droop noses, cheap fast cfd and fea optimisations, and even ability to do laminar flow wings that can all hook together to greatly reduce weight of aircraft and increase efficiency compared to old Concorde.

The boom remains the big problem, but the economics could otherwise probably work, and there is a market for international flight over oceans, that dropping flight times would increase further. With passenger volumes increased by an order of magnitude since the 70's the time for supersonic airliners might be returning - Boom Nimbys are the big uncertainty/roadblock. And of course corporate risk aversion.

Maybe the chinese govt will do it - it is the kind of thing that would appeal to them and would let them break into civilian aerospace doing an end-run around the Boeing Airbus duopoly.

Re:For future reference,

[viking80]

One correction to your math. At high Mach, the curvature of the earth creates a "virtual" L/D improvement. For example at Mach 22, you will have a L/D ratio better than 100 for a grand piano filled with tungsten.

Re:For future reference,

[phantomfive]

The best supersonic designs I'm aware of achieve a L/D of around 9 at L/D at Mach 1.5. These are incredibly optimized designs that have been fine-tuned with supercomputers and would be quite unfeasible for a passenger aircraft (weird shapes, no windows, etc.) As a result the Concorde consumed about 3x more fuel PER MILE than a comparable subsonic jet. So half the mass of the Concorde was fuel (!), it winded up being very heavy, and it carried only 100 passengers. And its maximum range was limited to 4500 miles.

These guys (actually, there are several different teams working on competing designs, including Airbus) are planning on using ramjets, probably powered by hydrogen.
Interestingly, the prototype pictured in the article has no windows, not even a cockpit (as far as I can tell).

Re:For future reference,

[joe_frisch]

Agreed. Its also very difficult to make efficient scramjets which makes the problem even worse. The best scram jets so far have barely been able to maintain steady flight at a single mach number and in a short range test vehicle.

I think there is a good chance that you want to jump from supersonic all the way to mostly ballistic sub-orbital. It also completely avoids the noise footprints except (and its a BIG except) at the launch and landing points.

As several people have also said, I'll take hyper-sonic travel seriously only after we have supersonic commercial flight again. Existing airliner speeds haven't changed significantly in 60 years. (!!!). (the same time it took to go from the Wright brothers to near mach-1 travel).

Re:For future reference,

[Beck_Neard]

Minor correction: The HIGHER the L/D, the more fuel you have to consume per mile.

Re:For future reference,

[Beck_Neard]

The dependence between L/D ratio and range is independent of height or air density. Assuming fixed speed, in less dense air, you have less drag, but you also produce less lift.

Re:For future reference,

[Beck_Neard]

That's another good point that I forgot to mention: At high speed, it becomes hard to develop efficient engines. The best engine efficiency occurs at low (below Mach 2.0 or so) speeds where good pressure recovery exists and the velocity of the exhaust jet is matched with forward flight speed. At higher speeds air-breathing engines become far less efficient.

Re:For future reference,

[Beck_Neard]

I completely agree about the feasibility of a Mach 2.0 transport in the same vein as Concorde. I never suggested anything to the contrary.

What you have to consider though, is that even though there have been a lot of technological improvements since the 70's, fuel costs have also risen enormously (as a fraction of operating cost), and airliners run on profit margins of 1% or so. It's a really lousy business to be in overall and it's no surprise that most airlines are heavily state-supported.

While reports about Concorde losing money are a bit overblown, it still didn't make nearly as much money as subsonic airliners, and an SST introduced today would have the same problem. From the perspective of the consumer, it makes far more sense to get a regular business class ticket than a ride on an SST unless you really really have to go from London to NY in 3 hours. A long-haul SST service from, say, London to LA or LA to Sydney would be far more attractive but would be technologically hard.

Re:For future reference,

[Anonymous Coward]

That's not a "minor" correction, but I still appreciate you doing it. That's uncommon here. Kudos.

Re:For future reference,

[BlackPignouf]

Thank you. Also : peak oil.

Re:For future reference,

[Anonymous Coward]

Wow. So you are using lift/drag to analyze a ballistic suborbital hop? Brilliant! Why didn't all the people that have suggested the "few hours to anywhere" suborbital hop (you know, the ones with extensive experience and education) not just consult with random basement dwelling mouth breathers? They could discover other things like how much red weighs and such.

Re:For future reference,

[serviscope_minor]

Mach 2 engines *were* more efficient at the time the concorde was built. In the mean time however, more efficient engines have been built: compressors have got better, but crucially, people have figured how to make turbofans efficiently have extremely high bypass ratios. So while the core might be more efficient at Mach 2, the overall production of thrust isn't, unfortunately.

Re:For future reference,

[KonoWatakushi]

You keep arguing as if the Lapcat A2 uses a conventional engine, which it does not. An entirely new thermodynamic cycle takes advantage of the extremely cold fuel to significantly improve efficiency. Rather than armchair speculation based on generalizations, I'm more inclined to trust the actual modeling done for these engines and aircraft, for which the numbers look very promising. The engines are based on SABRE, and the ESA is confident that the design is sound.

Re:For future reference,

[cjameshuff]

These issues arise because the engine takes in air as reaction mass and ejects it at higher speed to produce thrust...they apply to anything that breathes air. No fancy internal thermodynamic cycle can get around this. Ultimately, accelerating that flow of reaction mass by a given amount takes more power as the initial velocity of that reaction mass with respect to the craft increases. The only way around this is to not breathe air.

The fact that their engine is absolutely dependent on large quantities of liquid hydrogen is also not promising when it comes to economics...

Re:For future reference,

[Anonymous Coward]

In the real world, cruising at higher altitude is well known to improve efficiency. You won't get anything close to the rated range of out of something like a 747 if you stay at 3 km altitude the whole trip.

Assuming fixed speed, in less dense air, you have less drag, but you also produce less lift.

In order to maintain level flight, the lift produced by an aircraft must be equal and opposite to the pull of gravity. So, obviously (all else being equal) a plane cruising at 15 km is producing the same amount of lift as one in level flight at 3 km.

However, the plane at 15 km will experience much less drag in the thinner air, and consequently require much less fuel to maintain its speed.

The source of your error is confusion over the significance of the characteristic lift-to-drag ratio of an airplane. A characteristic L/D of 25 does not mean that lift is always equal to 25 times drag. Rather, it means that lift is always less than or equal to 25 times drag. The instantaneous L/D ratio is controlled within that range, as needed by the pilot, by adjusting the plane's angle of attack.

The air pressure at 3 km is about 72 kPa, versus 14 kPa at 15 km. So, at the same speed a plane at 3 km will experience about 5 times the drag, and be capable of generating 5 times the lift at optimal angle of attack. If, at its maximum L/D ratio of 25, the plane can generate enough lift to maintain level flight at 15 km, the pilot at 3 km will have to lower his L/D to about 5 by reducing his angle of attack to avoid rapidly ascending.

The difference in fuel economy between the two flight plans really is (almost) as large as those numbers imply; for long distance flights optimal fuel efficiency is achieved by basically going as high as you can without completely depriving the engines and/or control surfaces of air.

Aside from the sudden massive increase in drag which accompanies breaking the sound barrier, the same principles apply to supersonic and hypersonic aircraft. Because they go so much faster, such aircraft can also fly much higher, mitigating the extra drag. The SR-71 maxed out at almost 26 km, where the air pressure is as little as 2 kPa - a further 5 times lower than the pressure experienced by a subsonic airliner at maximum altitude. Thus, aerodynamically an SR-71 at maximum speed and altitude might actually be more efficient than a 747.

(The SR-71's lesser range - which is actually still quite good compared to many other airplanes of similar size - can be explained entirely by the large fuel burn required to reach the higher cruising speed and altitude in the first place, and by the much lower specific impulse of the insanely overpowered engines required to sustain flight at Mach 3+:

6850 nmi (range of a 1970's 747) * 3000s (approximate specific impulse of SR-71 engines in full afterburning cruise) / 8000s (approximate specific impulse of 747 turbofan engines) = 2600 nmi (less than the actual range of an SR-71)

So, if only the SR-71's engines could be made as efficient as typical subsonic airliner engines, its superior cruising altitude would actually have given it more range than contemporary 747s, despite its reduced L/D ratio.)

Re:For future reference,

[Anonymous Coward]

So half the mass of the Concorde was fuel (!)

That's not unusual. The Boeing 747-400, for example, has an empty weight of 179 tonnes, and a fuel capacity of 217 kilolitres (massing perhaps 170-180 tonnes). The difference is, the 747 can fly twice as far with that fuel load.

Re:For future reference,

[joe_frisch]

(not disagreeing with your conclusions) Depends on how you define efficiency. For an ideal jet engine the power to produce a given thrust goes up with airspeed, but since you are moving faster, the energy per distance remains the same. (distance * Weight / (L/D) = energy_use. ) ,.

For a real engine though the efficiency does go down. Conventional ram jets don't work well at high speed because slowing down the inlet air to subsonic heats it too much, and involves aerodynamic losses.

Supersonic Combustion Ram Jets can work - there you never slow down the air so there isn't much loss in efficiency. (see the X-51 for example). Still, its difficult for many reasons. You do need to slow the air some - and the aerodynamic efficiency of the inlet decreases for much the same reason the wings get less efficient at high speeds. Its tricky to mix the hydrogen in at high speeds - you need lots closely spaced injectors, and that can add drag. The flame speed in hydrogen is subsonic, so you need some way to keep it from blowing out the back of the engine - constant ignition, or detonation wave combustion (mostly a concept for >mach12), or some other trick.

Noting violates basic physics but this is a LONG way from being practical for a passenger aircraft.

Re:For future reference,

[Anonymous Coward]

Concorde B (minor wing and engine changes, never built due to halt in production) would have lifted range about 10-20% from Concorde. L/D about 7.5. Modern jets are not 25, more like 21-22, so yeah about 3x, though a new Mach 2 SST might get L/D up to 8 or 9

Fuel per distance depends not on L/D alone, but on Mach times L/D (look for Breguet range equation). So everything else being equal, Mach 0.85 airliner with L/D of 21 is going to spend as much fuel as Mach 2 airliner with L/D of 9.

But everything else is not equal, like the empty mass. This will be higher for supersonic transport, for the given number of passengers. E.g. A319 is ~0.35 t/pax and Concorde was ~0.65 t/pax. More fuel will be needed to keep that extra mass in the air (check the same equation).

Re:For future reference,

[Beck_Neard]

Until a SABRE engine is flying we might as well be talking about the efficiency of flying carpets. The intercooler has been tested and apparently it works, so I'm hopeful that the engine design will work, but you never know until you actually fly.

By the way, if it works, it will achieve an efficiency about equal to that of a conventional turbofan engine. Which is great, but still wouldn't get you from London to Sydney cheaply.

Re:For future reference,

[Beck_Neard]

I have a PhD in engineering. The mechanics of flight are obviously complicated but I'm attempting to simplify it so that we can make ballpark estimates of fuel consumption and efficiency. And I explicitly said I'm referring to straight and level flight at cruise speed. My analysis is correct.

'Ballistic suborbital hop' is a neat bait-and-switch word trick though. Sure, you can reach 'space' (above 100 km) with relatively low fuel consumption if you wanted to, but that will only get you a few hundred miles downrange. To travel clear across the world, you need a ballistic trajectory that comes pretty darned close to an orbital trajectory, and then you're looking at basically building a rocket.

Using a ballistic trajectory is far, far less fuel efficient than flying, no matter the altitude, because you aren't taking advantage of the atmosphere to provide lift. If you look at vehicles designed for ballistic trajectories (missiles, ICBMs, etc.) they all have very high fuel mass fractions and very low payload mass fractions.

Re:For future reference,

[Beck_Neard]

> You won't get anything close to the rated range of out of something like a 747 if you stay at 3 km altitude the whole trip.

That's only because the 747 is designed to fly at that altitude and speed. It's airframe and engines have been optimized for that speed. I fail to see how this is relevant to what I'm saying.

> A characteristic L/D of 25 does not mean that lift is always equal to 25 times drag. Rather, it means that lift is always less than or equal to 25 times drag. The instantaneous L/D ratio is controlled within that range, as needed by the pilot, by adjusting the plane's angle of attack.

You're getting dumber by the minute. I explicitly said I'm talking about straight and level flight.

Nothing you said negates what I'm saying about lift/drag. You're just attempting to spin an argument around it.

Re:For future reference,

[Beck_Neard]

As far as I know, the Concorde's engines are still the most efficient combustion engine to have ever been built. This is mainly due to the intake which had very good pressure recovery. Modern engine design techniques could push the efficiency still higher. Unfortuntaely, the fairly high drag at supersonic speeds more than cancel out this efficiency improvement.

Re:For future reference,

[Anonymous Coward]

That's only because the 747 is designed to fly at that altitude and speed. It's airframe and engines have been optimized for that speed. I fail to see how this is relevant to what I'm saying.

At low altitudes, it is basically impossible to avoid experiencing substantial form drag at jet aircraft speeds, regardless of wing design. The form drag of the fuselage falls linearly with air density.

Fuselage design is dictated mostly by what needs to fit inside of it. The optimal shape is somewhat influenced by speed, but not all that strongly until you hit the transonic regime. The coefficient of drag and reference area are not meaningfully altitude-dependent.

All truly long-range jet aircraft are designed to cruise at high altitude, because form drag precludes efficient operation at low altitudes. The military would love to be able to build a bomber which can fly at sea level for 6,000 miles, but they can't.

I explicitly said I'm talking about straight and level flight.

And I also explicitly said I was talking about straight and level flight, multiple times. Even in level flight, angle of attack is often non-zero. Angle of attack describes the orientation of the plane itself, not its velocity vector.

Nothing you said negates what I'm saying about lift/drag.

It ought to give you pause that the shorter range of the SR-71, which you claimed as evidence for your theory, is entirely explainable by the low specific impulse of its engines.

Re:For future reference,

[AK Marc]

Ultimately, accelerating that flow of reaction mass by a given amount takes more power as the initial velocity of that reaction mass with respect to the craft increases. The only way around this is to not breathe air.

A supersonic ramjet doesn't slow the air down to subsonic, like running a conventional turbine at high speed does. So breathe air, just don't slow it down.

Re:For future reference,

[Anonymous Coward]

Although aerodynamic lift can be very helpful, this is not the main reason for the very low payload fractions of ballistic missiles or orbital rockets.

The actual (direct) cause is the massive loss of effective specific impulse incurred by carrying all of your own propellant, rather than taking in atmosphere to serve as additional reaction mass. Each kilogram of kerosene fuel must be mixed with about 2.5 kilograms of oxygen to burn completely, so burning atmospheric oxygen allows an engine to produce the same impulse while carrying less than 30% of the propellant.

Efficiency of real jet engines is further increased by spreading the energy of combustion over up to ~30x as much air as is actually required to oxidize the fuel. Because the kinetic energy of the exhaust scales as 1/2*m*v^2, while the momentum scales as m*v, distributing the same energy over more mass greatly increases the momentum transfer. (Using 30x more mass would ideally yield 24x the thrust for the same energy.)

Of course there are various inefficiencies inherent to using the atmosphere in this way, so the actual gains are smaller than the factor of ~80 implied. Nevertheless, the net efficiency gain is massive; jet engines are 5-20x as fuel efficient as rocket engines, depending on exactly what you compare. (Aside from the obvious need to remain in the atmosphere, the other big drawback to jet engines is the high weight of the fans and compressors.)

Despite its low fuel fraction, a fully loaded 747 has something like 28 km/s of deltaV, sufficient for a round-trip to and from the surface of the Moon, followed by a powered deceleration at Earth so as to avoid burning up in the atmosphere. Propulsion-wise, it is mainly their need to operate in relatively thick, drag-inducing air which prevents them from doing so.

The 747, with its phenomenally efficient jet engines, must begin its journey with about 33% fuel, by mass, to achieve such range. In contrast, thanks to the tyranny of the rocketry equation, an ideal single-stage kerosene powered rocket would need to be over 99.96% fuel to do the same thing.

TL;DR: It is the terrible efficiency of chemical rocket engines, much more than the lack of aerodynamic lift, which makes ballistic missiles so big and expensive.

Re:For future reference,

[Beck_Neard]

All that talk about form drag is completely irrelevant. For the second time, I'm just talking about a simple number: Lift/drag. Yes, it changes under different circumstances and yes, for a lot of craft it is lower at higher altitudes. I never said Lift/drag is constant across the entire flying envelope of an aircraft! That would be idiotic and insane. I'm just saying the relationship between Lift/drag and range does not depend on air density since, for a first-order analysis, you can absorb all of the dependencies into the lift/drag ratio.

> And I also explicitly said I was talking about straight and level flight, multiple times. Even in level flight, angle of attack is often non-zero. Angle of attack describes the orientation of the plane itself, not its velocity vector.

Jeezus... I did not say AoA is zero! For the third time, I'm talking about straight and level flight at cruise speed and altitude.

Re:For future reference,

[Anonymous Coward]

I'm just saying the relationship between Lift/drag and range does not depend on air density since, for a first-order analysis, you can absorb all of the dependencies into the lift/drag ratio.

Assuming constant speed:
1: [thrust (N)] = [drag (N)]

By the definition of [L/D ratio]:
2: [drag (N)] = [lift (N)] / [L/D ratio]
From #1 and #2 by substitution:
3: [thrust (N)] = [lift (N)] / [L/D ratio]

By the definition of [lift coefficient]:
4: [lift (N)] = 1/2 * [air density (kg/m^3)] * [speed (m/s)]^2 * [reference area (m^2)] * [lift coefficient]
From #3 and #4 by substitution:
5: [thrust (N)] = ( 1/2 * [air density (kg/m^3)] * [speed (m/s)]^2 * [reference area (m^2)] * [lift coefficient] ) / [L/D ratio]

By the definition of thrust-specific fuel consumption - [TSFC (kg/(s*N)]:
6: [fuel flow (kg/s)] = [thrust (N)] * [TSFC ( kg/(s*N) )]

Assuming a small wet-to-dry mass ratio to keep the math simple:
7: [range (m)] ~= [speed (m/s)] * [fuel mass (kg)] / [fuel flow (kg/s)]
By substitution and simplification from #5, #6, and #7:
8: [range (m)] ~= 2 * [fuel mass (kg)] * [L/D ratio] / ( [air density (kg/m^3)] * [speed (m/s)] * [reference area (m^2)] * [lift coefficient] * [TSFC ( kg/(s*N) )] )

From #8, it can be clearly seen that range is inversely proportional to [air density], which is an independent parameter from [L/D ratio]. The independence of [air density] from the other parameters in #8 is because the maximum cruising altitude attainable by an aircraft also depends upon how much [thrust] its engines can produce at altitude.

Re:For future reference,

[serviscope_minor]

Yes: the core is efficient at higher mach numbers, and it certainly was the most efficient engine in service at the time. And yes, drag at supersonic speeds does matter.

But modern high bypass turbofans then convert the high speed, hot exhaust into a large, cool, low speed stream of air. Consider that you can impart a fixed amount of energy to a block of air. energy goes as velocity squared and momentum is linear in velocity. You get the most momentum by making a large amount of air move slowly as compared to a small amount move very fast.

This is also why planes have wings rather than just pointing engines at the ground: turbofan bypass is essentially just an intermediate form of such things.

https://en.wikipedia.org/wiki/...

The concorde has about 2x the fuel consumption for a given thrust compared to a high bypass turbofan. Though of course it's going over 2x as fast, so it needs to generate the thrust for under half the length of time, which evens it out to just a bit better for the concorde. The CF6 is an old high bypass turbofan though. A more modern one like the trent 1100 will give substantially better results.

So, in conclusion, by the early 70s, there were high bypass turbofans which could nearly match the concorde engine for efficiency in terms of amount of fuel / thrust / unit of distance.

Also, the most efficient combustion engine I know of (in general use, not some lab prototype) is the Flex-96C, which is over 50% efficient compared to about 43% for the concorde. You wouldn't find a Flex-96C on any sort of aircraft though.

Re:For future reference,

[Big Hairy Ian]

Add to this they're talking about trying to get this up and running by 2030! We'll be more likely to see sub orbital passenger flights doing it in 90mins than this

Re:For future reference,

[cjameshuff]

Whether it slows it down or not as an intermediate step is entirely irrelevant. Kinetic energy is proportional to the square of velocity. Applying a given increment in velocity (as a jet engine of any sort needs to do to produce thrust) costs more energy at higher initial velocities.

Re:For future reference,

[Anonymous Coward]

Correcting myself...

The independence of [air density] from the other parameters in #8 is because the maximum cruising altitude attainable by an aircraft also depends upon how much [thrust] its engines can produce at altitude.

Since I began by assuming constant speed, that last sentence is incorrect. A better explanation for why the [air density] parameter is independent of [L/D ratio] is:

Assuming level flight:
9: [lift (N)] = [g0 (m/s^2)] * [total mass (kg)]
From #4 and #9 by substitution, solved for [air density]:
10: [air density (kg/m^3)] = 2 * [g0 (m/s^2)] * [total mass (kg)] / ( [speed (m/s)]^2 * [reference area (m^2)] * [lift coefficient] )

So, even when all the other parameters to the range formula (given as equation #8 above) are fixed, you still need to know the [total mass] of the aircraft to calculate [air density]. All else - including [L/D ratio] - being equal, an aircraft with lower [total mass] will be able to fly higher, and therefore experience less drag and achieve a greater [range].

Re:For future reference,

[stoatwblr]

Hypersonic travel is spent at altitudes so far up that lift/drag isn't much of an issue. Any higher and you'd need to resort to "skipping" into lower atmospheric levels to relight the engines and get thrust (This has been proposed but the negative points include endless passenger barfing)

Re:For future reference,

[Beck_Neard]

Thrust specific fuel consumption can't be used to compare a supersonic engine with a subsonic one, because it must be compared at fixed speed.

The concorde's engines had a propulsive efficiency of 43% at cruise. The best modern high-bypass turbofans I'm aware of achieve a propulsive efficiency of 35% at cruise. As I said, the main reason for this discrepancy is the intake which provided good pressure recovery and the losses encountered when you mix a hot fast-moving stream with a cold slow-moving stream. Newer turbofan designs are pushing up against 40% efficiency though.

Re:For future reference,

[serviscope_minor]

Thrust specific fuel consumption can't be used to compare a supersonic engine with a subsonic one, because it must be compared at fixed speed.

Well it depends what you're trying to do. Ultimately, aircraft efficiency is about how much fuel you take to get to your destination. The trust/time measure is a reasonably good one because it factors out one of the important but ultimately irrelevant details of efficiency which is how long the aircraft flies for.

As for comparing engines at fixed speeds: that's essentially impossible. The optimum speed for a high bypass turbofan and the optimum speed for a supersonic afterburning capable turbojet are quite different.

And you're still missing the point. The concorde engine is very efficient at squirting out a high speed jet of air out of the back, with 43% of the thermal energy going into kinetic energy. More efficient than other engines. However, squirting out a high speed jet of air s not a very good way of generating thrust, especially at subsonic speeds and/or when you can afford a larger frontal area.

Or, look at it this way: the engine core of modern turbofans gets 40% thermal efficiency.That's the *core* and would still get it with or without the fan at the front. Without the fan, you'd get a small, high speed jet of air out the back, with 40% efficiency but not much thrust.

There's more to propulsive efficiency than raw thermal efficiency.

Re:For future reference,

[Beck_Neard]

Ok I might have simply misunderstood you previously. I agree with what you're saying here. It's what I'm saying as well: There's nothing special about the Concorde engine, it's just that the speed at which it flew was a great speed for turbojet efficiency (and it had a good intake design). But maybe you've also misunderstood me. I'm not taking a dig at turbofan engines or other modern engines.

Re:For future reference,

[serviscope_minor]

Oh OK yes, then sure.

I think many people don't realise that the concorde was designed for fuel efficiency and that it's only a gas guzzler by modern standards. By the standards of the time it was designed it was decently efficient, precisely because of those engines and the supersonic speed.

Labour costs

[MichaelSmith]

It used to be economic to spend a month on a ship, paying hotel rates for labour but thats just too expensive now, so you pay less money to spend a day on a plane to go half way around the Earth. But at some point the cost of labour will rise to the point where that one day is too expensive as well, so it will be economic to develop faster aircraft which cost less in manpower to run. Even now an SST could get away with less in cabin staff, fewer changes of crew, etc.

NIce

[Impy the Impiuos Imp]

Good tech, but why doesn't a project for the elitist rich bother Europeans? And subsidized at that?

Re:NIce

[Anonymous Coward]

you're an idiot

europe/uk is just as corrupt as the US. they just think its culturally more important to pretend to address the
concerns of the unwashed masses.

go back to pretending that you're #1. #1. #1 damn it #1.

Re:NIce

[Jeremi]

Why should a paper airplane bother anyone? They might as well have come up with plans to build a Death Star in orbit.

If/when someone decides to actually start building this airplane (and asking for the billions of euros required to do so), then it becomes something worth being bothered by.

Concorde didn't fail because of tech

[Tony Isaac]

It failed because the cost of tickets was unsustainable, and they couldn't get the price down to where enough people would buy them to make it financially viable.

This will be the fate of any future super-high-speed mode of travel, if they can't get the cost down enough so that ticket prices can compete with traditional air travel.

Re:Concorde didn't fail because of tech

[mpoulton]

It failed because the cost of tickets was unsustainable...

The Concorde failed because a tire exploded, it streaked terrifyingly across the Paris sky trailing hundreds of feet of fire, and crashed in a giant fireball, killing everyone. And then the fleet was instantly and irrevocably grounded. The program had its economic issues over the years, but was still in operation nonetheless - until the disaster.

Re:Concorde didn't fail because of tech

[Tony Isaac]

Concorde was hardly the first jetliner to crash in a giant ball of fire.

Re:Concorde didn't fail because of tech

[ganjadude]

by that logic there are no more 747s in flight because of flight 800 right?

Re:Concorde didn't fail because of tech

[0123456]

And then the fleet was instantly and irrevocably grounded.

Uh, no, it wasn't.

Concorde was operationally profitable, at least for BA, until 9/11 took the bottom out of the airline market and killed many of the people who used to fly on Concorde (e.g. bankers flying between NYC and London), and the cost of the required upgrades to keep them flying couldn't be justified.

The crash did scare off some passengers, but they flew on for several years afterwards.

Re:Concorde didn't fail because of tech

[0123456]

Oh, and the tire didn't 'explode', it was cut open by a piece of debris on the runway. That can happen to any aircraft, but it was more dangerous to Concorde because of the large fuel tanks and the location of the wheels relative to them.

Re:Concorde didn't fail because of tech

[Zontar The Mindless]

And then the fleet was instantly and irrevocably grounded.

No, it wasn't. Air France 4590 crashed on 25 July 2000. Regular Concorde passenger flights resumed the following year and continued for about 2 years after that.

Re:Concorde didn't fail because of tech

[uvajed_ekil]

It failed because the cost of tickets was unsustainable...

The Concorde failed because a tire exploded, it streaked terrifyingly across the Paris sky trailing hundreds of feet of fire, and crashed in a giant fireball, killing everyone. And then the fleet was instantly and irrevocably grounded. The program had its economic issues over the years, but was still in operation nonetheless - until the disaster.

I think you are misremembering history. Concordes were not instantly and irrevocably grounded after the 2000 Paris accident, as some flew well into 2003. Maintenance costs were rising on the old planes and demand sagged after 9/11. The Paris wreck was a heavy blow but it is not what ultimately ended Concorde service. The flight deck of those things was so antiquated by 2003 and they were so inherently crappy to fly that I'm surprised they made it that long. Incredible machines, and a real marvel in their day, but it is not accurate to say that their one and only fatal accident did them in.

And, for the record, the tire only exploded because it had help from debris another plane had left on the runway, and because other factors caused the Concorde to use more of the runway than normal on takeoff. As demanding as it was (long runway requirement, so unique to fly, incredibly thirsty, limited cargo and seating capacity, old, and expensive to maintain) the plane in question was completely airworthy. Decreased demand and increased costs related to security caused a lot of grief in the airline industry after 9/11, and didn't just kill the Concorde.

Re:Concorde didn't fail because of tech

[Macdude]

Concorde failed because the number of airports it could fly into was extremely limited and the ground it could overfly was even more limited.

But in reality it failed because it was expensive, cramped and didn't reduce total trip time by all that much.

Re:Concorde didn't fail because of tech

[serviscope_minor]

It failed because the cost of tickets was unsustainable, and they couldn't get the price down to where enough people would buy them to make it financially viable.

No, the BA one was mildly profitable. Not hugely so but profitable nonetheless. The French one wasn't, but then again if your crew are on strike for 364 days of the year and rioting for the remaining 1 1/4, then profit margins are thinner so it's harder to turn a profit.

What actually happened is that the French conglomerate which wound up with the plans and support after mergers and mergers and mergers refused to continue supporting the aircraft and refused to sell the support to someone else.

Re:Concorde didn't fail because of tech

[Tony Isaac]

Still, it wasn't profitable enough to spread the service to other markets, or to make it worthwhile to have more of the planes built. If it were, it would have happened.

Re:Concorde didn't fail because of tech

[Anonymous Coward]

It was for a while, but things got complicated with BA and BCal not allowed to step on each other's areas of service, and BCal just about to setup a lease to create new routes in the 80s. But the price of oil was went up and their small scale plans were too tight in profit margins to follow through. They might have actually pulled it off if they went slightly larger with their lease plans and not depend on high utilization, however there wasn't many more planes available.

Unlikely

[Anonymous Coward]

The Concorde was retired over a decade ago, and since then, nothing comparable to it has been developed, much less put into production.

They have it all wrong. In 15 years, the pinnacle of commercial airplanes won't be shiny, fast and high tech. They will be more like buses or trains: slow, boring, reliable and affordable.

Because that's what people want, especially if the affordable part far out weights the slow and boring parts.

Re:Unlikely

[turkeydance]

retired 'cause rich people died. rent-a-jet took that market.

Re:Unlikely

[Anonymous Coward]

Well I think the high speed wasn't what the rich guys were looking at after all. Currently the rich guys don't need to travel overseas to arrange their business as fast as possible. That's when video conferencing and delegation comes in play. What they want though is a comfortable flight where they can stretch their legs, have something to read or look at and have drink and food on demand. Those large Aerobus have models with build in casino's. I guess for someone who doesn't know what to do with his money, it's more fun to do a 10 hour flight while trying to impress the ladies than to sit 2 hours in the deafening sound that makes conversation difficult, even impossible.

Re:Unlikely

[uvajed_ekil]

They have it all wrong. In 15 years, the pinnacle of commercial airplanes won't be shiny, fast and high tech. They will be more like buses or trains: slow, boring, reliable and affordable.

They're already slow, boring and reliable. Where I disagree is that I don't see them getting a whole lot more affordable in 15 years. Fuel and maintenance costs should continue to drop as more old planes are replaced with current and upcoming models but ticket prices have only gone up. People will continue to pay high prices for air travel unless ground travel suddenly becomes a whole lot quicker and we build highways and railroads over large bodies of water. We all seem to hate airlines, but what are you going to do, go Greyhound? Yeah, right. Air travel will continue to be both expensive and popular for the foreseeable future, especially but not only in America. Not every place has a rail system like Western Europe, nor is as compact.

Re:Unlikely

[Anonymous Coward]

We all seem to hate airlines, but what are you going to do, go Greyhound? Yeah, right. Air travel will continue to be both expensive and popular for the foreseeable future, especially but not only in America. Not every place has a rail system like Western Europe, nor is as compact.

Hyperloop?

Maybe one day.

Sure it's possible

[CanadianMacFan]

I'll just hop in my flying car to get to the airport and catch my flight in it.

Laughable journalism

[gman003]

"What’s more, liquid hydrogen fuel is not highly combustible mid-flight. Although hydrogen can be ignited, the risks of an explosion or fire are lower compared to conventional airline kerosene fuel"

Gaseous hydrogen is already a ridiculous explosive risk. Liquifying it only makes the resulting explosions bigger. They somehow think this is safer than Jet-A, which is actually less flammable than gasoline.

There are valid engineering reasons for the use of liquid hydrogen as a fuel, such as specific impulse or heat capacity. But safety is absolutely not one of them.

In other news, this is a blatantly obvious attempt to get funding for SSTO spacecraft development by disguising it as a less outlandish business plan. Seriously, this has much more in common with Skylon or VentureStar than with Concorde, right down to the choice of fuel. I wouldn't be surprised if many of the engineers are the same.

Re:Laughable journalism

[Anonymous Coward]

Don't know why the Lapcat is mentioned now in an article (didn't read).

But the Lapcat is basically the suborbital passenger version of the Skylon. Always has been, have seen it referenced on reactionengines.co.uk a few years ago.

Hmm

[koan]

I wonder if that makes the jet lag worse.

Why not Mach 22

[viking80]

Why not Mach 22

If you first want to go fast, why not just use an intercontinental ballistic missile? It is really simple construction (read fuel tank with orifice), uses cheap fuel, and really need no fancy aerodynamics or control system. Just aim and fire.

The whole idea of pushing a vessel through air for hours and hours, wasting fuel, when it can glide with no friction a few miles higher seems dumb. It also consumes more fuel in total.

Re:Why not Mach 22

[Anonymous Coward]

If you first want to go fast, why not just use an intercontinental ballistic missile? It is really simple construction (read fuel tank with orifice), uses cheap fuel, and really need no fancy aerodynamics or control system. Just aim and fire.

So cheap as in $50 million with max of about 5 passengers?

Re: Why not Mach 22

[Anonymous Coward]

This is why Virgin is investing so heavily in Virgin Galacticâ"not for space travel as they claim, as the tech is fundamentally unsuitable for adapting into that, but to supplement their air travel businesses.

Re:Why not Mach 22

[Beck_Neard]

Nope, you're dead wrong on all points. Flight is far more efficient than a ballistic trajectory. Being in an atmosphere is actually really great because wings allow you to lift far more weight than your engines themselves are capable of. And there's no way to 'glide' in space. You fall. The only way to avoid rapidly falling to the ground is to accelerate to such a tremendous speed (orbital velocity) that your freefall trajectory is wider than the curvature of the Earth. And to get to such speeds, you need a two-stage rocket that costs an insane amount of money and, at present, has to be thrown away each time it's used (Elon Musk is planning to change this, but it's not like it would make it as cheap as air travel).

Re:Why not Mach 22

[serviscope_minor]

And to get to such speeds, you need a two-stage rocket that costs an insane amount of money and, at present, has to be thrown away each time it's used (Elon Musk is planning to change this, but it's not like it would make it as cheap as air travel).

Actually, Skylon are planning to change it more (the people behind the Mach 5 LAPCAT variant), since their main line of work is a reusable single stage to orbit spaceplane. The Mach 5 airliner is essentially a simplified spaceplane without the exoatmospheric capability.

Re:Why not Mach 22

[Anonymous Coward]

That's all fine, but most people assume they'll be alive when they reach their destination.

Re:Why not Mach 22

[Anonymous Coward]

really difficult to avoid spilling your coffee in an ICBM

Re:Why not Mach 22

[Beck_Neard]

As I said above, until a SABRE engine is flying we might as well be talking about the efficiency of flying carpets. The intercooler has been tested and apparently it works, so I'm hopeful that the engine design will work, but you never know until you actually fly.

And even if it works, there's still a very large gap between "can struggle up to space carrying ridiculous amounts of cryogenic liquid hydrogen" and "affordable passenger aircraft."

Re:Why not Mach 22

[serviscope_minor]

As I said above, until a SABRE engine is flying we might as well be talking about the efficiency of flying carpets. The intercooler has been tested and apparently it works, so I'm hopeful that the engine design will work, but you never know until you actually fly.

The intercooler works, and so does the transition from air-breathing to LoX mode:

http://www.reactionengines.co....

Those are basically the two really crucial and untested bits. So, the exchanger works, and they've got a scaled down engine which produces lots of thrust, though it's bolted to a test stand.

Re:Why not Mach 22

[viking80]

Nope, you're dead wrong on all points. Flight is far more efficient than a ballistic trajectory. Being in an atmosphere is actually really great because wings allow you to lift far more weight than your engines themselves are capable of. And there's no way to 'glide' in space.

Maybe you lack some understanding here. Take the international space station. It is using almost no fuel as it moves along at Mach 22. If you lower it into the atmosphere, and add wings to it, you will use a lot more fuel to keep it flying.

Re:Why not Mach 22

[Beck_Neard]

Believe me, I think the SABRE engine idea is great and I'd love nothing more than a SSTO reusable rocket. But plenty (and I do mean plenty) of hypersonic aircraft (for example NASA's numerous concepts) have come and gone and none have lived up to their promises. Hypersonic flight is generally where aircraft designs go to die. The aerodynamics are tricky and poorly-understood. Heating is a huge problem. Intakes fail and un-start. There are lots of problems operating craft at such speeds. It's definitely not 'just the intercooler'. Again, I'll believe it when it flies. Skylon's major saving grace is that it's only designed to fly at hypersonic speeds for a very short time, so presumably it can 'punch' out of any failure modes that arise. Even if it does fly successfully, though, hydrogen is an expensive and tricky fuel and the SABRE engine uses a LOT of it. It may be worthwhile for space access but it's definitely not worthwhile for passenger flight.

Can it work?

[the_Bionic_lemming]

How much will it cost to change the rules about sonic booms, and what's going to be the window replacement cost for people under the flight?

Re:Can it work?

[AK Marc]

Sonic booms from low earth orbit are silent. And the rules would allow this as described without change, so no change needed.

And sonic booms don't break windows. Go watch the Mythbusters on that one.

Re:Can it work?

[the_Bionic_lemming]

I'm not stupid enough to pay for commercials - so I can't.

Re:Can it work?

[AK Marc]

But you are too stupid to find the content without commercials? That's a very narrow band of stupid. About 90 to 95 IQ I'd say. I've seen it and never paid to see a commercial in my life. And I wasn't even trying.

Re:Can it work?

[the_Bionic_lemming]

I'm not a thief, and I won't load adobe on my system.

Unlike other stupid people.

The race is on?

[uvajed_ekil]

What race is on? The race for funding for a project that requires new and unproven technology, and a ridiculously huge leap of faith, considering the fastest manned military aircraft in history has never even touched Mach 4? Yeah, um, the race is not on. Not yet, and sure as hell not any time soon. This half-assed summary reads like a bullshit Popular Mechanics blurb about someone's pie in the sky dream.

If fares were a modern equivalent of Concorde fares there would certainly be quite a few interested customers, and not just for the novelty of flying at Mach 8 or reaching any major city quicker than I can drive across Ohio. But beginning work soon on a Mach 8 commercial airliner would require skipping several logical and necessary steps, since there is currently no supersonic airliner in use or in the works and no manned military plane (some of the most advanced machines in the world) exceeds Mach 2 by very much. Achieving Mach 8 is no joke, and I can't see rocket propulsion receiving any consideration for a passenger craft.

Re:The race is on?

[Anonymous Coward]

MiG 25 still flying, iirc (Mach 3.1). its modern follow-on MiG-31 is too, but it "only" gets to Mach 2.8 or so.
 

Re:The race is on?

[Anonymous Coward]

3D printing has changed the game. Anything is possible.

What about solar power?

[tlambert]

Hydrogen is a terrible fuel. It has no good uses.

What about solar power? Most stars, including ours, tend to burn hydrogen.

Is it a great fuel for stars?

Re:What about solar power?

[colinrichardday]

The sun doesn't burn hydrogen (how much oxygen is in the sun?); it fuses it.

Re:What about solar power?

[Anonymous Coward]

Are we building stars now? And even if we were, you'll note that a chemical fire has a higher power density than the core of the Sun.

Diseases will travel faster...

[Anonymous Coward]

Expect advances in travel to increase the spread of dangerous disease more quickly.

Meh.

[tlambert]

Meh.

Hydrogen is a lot cheaper as a fuel, unless you source it stupidly, like they did in the article (they assumed no use of methane precursor, only electrolysis), and a Miele design will hit an L/D ratio of ~14 at low Mach numbers (e.g. Mach 2), which compares favorably with the Boeing 747 L/D ratio of 17 at Mach 0.85.

A Miele design will drop to an L/D ratio of about 7, but it takes going Mach 30 to get there. You can easily do an L/D ratio of 8, if you don't plan on going over Mach 5 with the thing -- and methane derived hydrogen fuel is far cheaper than jet fuel.

http://www.aerospaceweb.org/de...

My take-away on the article was: written by someone who doesn't want sonic booms (he states that the Concorde had booms as loud as 135 dB, but states in the same sentence that booms are 160 dB.

Re:Meh.

[Beck_Neard]

> and a Miele design will hit an L/D ratio of ~14 at low Mach numbers

Link?

Re:Meh.

[tlambert]

> and a Miele design will hit an L/D ratio of ~14 at low Mach numbers

Link?

Since you missed it in the first post: http://www.aerospaceweb.org/de...

Re:Meh.

[Beck_Neard]

I didn't miss it. I'm just asking you to point to where it gives a L/D of 14. If you mean the [Anderson, 2000] graph, I'm sorry but that's just showing the Kuchemann trend, NOT an actual measured L/D. The Kuchemann trend is not accurate for low Mach numbers.

If you're pointing to somewhere else in the article, then where?

Re:Meh.

[tlambert]

The text on the pages 1 and 3 prior to the reference to the graph.

There are other references on the Internet, but you have to have journal access to get them. There are probably others that don't need the access, but I didn't bother digging them out. The Concorde was particularly badly designed for L/D, being instead designed to minimize the sonic boom profile.

Re:Meh.

[Beck_Neard]

If you're talking about the reference to the F-111 and P-51 aircraft, that's talking about the subsonic L/D, not the supersonic L/D. A bit of searching on google confirms this: http://www.hq.nasa.gov/pao/His...

I have journal access. I'd appreciate if you could give me the links to the articles you're talking about.

Re:Meh.

[stoatwblr]

methane precursor is a significant carbon emitter. Electrolysis is predicated on cheap nuclear electricity or thorium-level heat being available for non-electrolytic water-splitting.

Not sure how this makes sense

[blindseer]

As pointed out by others the problem with faster aircraft is that a large portion of a traveler's time is spent standing in line at airports, not in the airplane. Few people travel at such great distances that such an increase in speed proves beneficial in decreasing travel time. What would be more beneficial is to reduce the time standing in lines at the airport.

We have a conflict of interests here. Bigger planes are cheaper to run. Bigger planes take more time to fill and, since they move more people at a time, need to run less often. Smaller planes take less time to fill, would need to run more often, reducing travel time.

I see the future of air travel being run more like a subway station. I show up at the station, pay my fare, and then I am free to get on any plane that has room for my butt in a seat. If the plane I want to be on is full then I wait 20 minutes for the next one. I should not have to pass through a metal detector or have to take off my shoes any more than if I was getting on a train or bus.

Domestic travel would be more likely to run like a subway station, international travel could be quite different. This hypersonic plane would not change the need for things like customs, which is where a lot of the waiting would be.

Re:Not sure how this makes sense

[RogerWilco]

I don't see the difference between domestic and international travel you're making. I have 6 different countries within 400km of where I live. Any shorter distance and I would take a train.

Re:Not sure how this makes sense

[blindseer]

International travel could be different because of customs. With more nations having freedom of travel agreements this is less of an issue but if one passes a border where a visa is required then there would be people standing in line.

Hydrogen fule is not necessarily "green"

[blindseer]

The article points out how having this plane burn hydrogen gas would be less polluting than if it burned kerosene like conventional jet planes. It then points out that getting hydrogen gas from natural gas would be the cheapest way to get it. If the hydrogen gas ultimately comes from a fossil fuel then it's no "greener" than any other fossil fuel burning jet plane.

I hear the same thing about electric cars. Electric cars are not inherently "green" since a large portion of our electricity comes from coal and natural gas. Electric cars are coal burners. Hypersonic aircraft would be burning hydrogen derived from natural gas, using a factory powered most likely by coal, it is also therefore a coal powered vehicle.

Even if the hydrogen was from cracking water unless that plant was powered by wind or nuclear then it would still be a coal powered airplane.

I've said for a long time that these "green" advocates will get us all killed. If it isn't the electric and hydrogen vehicles that are powered by coal then it's the lights going out because the sun didn't shine on their desert solar power plant for two weeks. Deserts may have fewer clouds than the rest of the world but they still have clouds. I'm a fan of clean energy but I'm also a fan of arithmetic. Wind and solar power cannot keeps the lights on. Bio-fuels mean we have to choose between eating or driving to work. The only thing that adds up is nuclear power.

To those that will scream "WHAT ABOUT THE NUCLEAR WASTE!!!!" I say do a Google search on waste annihilating molten salt reactors. All molten salt reactors can consume existing nuclear waste while making electricity, it's just that the WAMSR is optimized for eating the waste over producing power.

If we build a nuclear powered hydrogen plant to make fuel for this hypersonic airplane then we'd have a "clean" flying aircraft. But then if we can make this plane fly from burning hydrogen then what keeps us from converting subsonic aircraft to burning hydrogen? It would be a matter of logistics, we've built up a large infrastructure around kerosene powered aircraft. So much so that light aircraft that typically ran on gasoline are trending towards running on jet fuel. If this airplane works out, and does so with it's "green" hydrogen fuel, then I expect that we'd see more planes come out shortly afterward that also burn hydrogen. Or at least we'd see the hydrogen used to synthesize jet fuel. At that point we'd have the "hydrogen economy" that so many tree huggers dream about, only it would look a lot like the oil economy we have now to end users.

Re:Hydrogen fule is not necessarily "green"

[Beck_Neard]

> Electric cars are not inherently "green" since a large portion of our electricity comes from coal and natural gas.

You're right about the hydrogen, but wrong about this. Electric cars ARE green because internal combustion engines are really, really, and I do mean really, inefficient. If you do the math, the typical electric car in the USA produces 2-4x times less emissions than a gas car (even taking electricity production into account). And in places where the electricity is generated cleanly, they produce zero emissions.

Re:Hydrogen fule is not necessarily "green"

[blindseer]

Assuming an electric car gets twice the thermal efficiency compared to a petrol car I'll do some math. A coal powered electric car is powered solely by the carbon bonds on coal, that means every joule comes from turning carbon and oxygen into CO2. A petrol powered car gets roughly half its power from the carbon bonds and half from the hydrogen bonds. If the petrol car is getting half of its energy from turning hydrogen and oxygen into H2O then it's producing the same amount of CO2 per mile traveled.

If we compare the coal powered electric car to a car run on methane then we get better numbers. For every carbon atom burned in that methane we get four hydrogen atoms burned. Which by my back of the envelope math the methane burning car is just as good, or better, than the coal powered electric car that has four times the thermal efficiency.

No one in the USA can claim a "green" electric car because in the USA 80% of our electricity comes from coal or other fossil fuels. Even if someone owns an electric car, and charges it from their own solar panels, it's still not carbon neutral since the aluminum and steel used to make that car came from coal powered factories.

What we might have is a bit of a chicken and egg question. What comes first, the electric car or the nuclear power? It's difficult to justify the electric car with coal power and so long as cars burn petrol a nuclear power plant does nothing to reduce emissions from vehicles. As long as we get so much of our electricity from coal it seems obvious to me to make the transition from coal to nuclear as soon as possible. After we have a majority of our electricity from nuclear power then it might make sense for electric vehicles from a standpoint of CO2 emissions. Even then we'd still have a problem with the financial cost of electric vehicles. Perhaps electric cars will become cheaper in time but I doubt it. I'd think that natural gas would get so cheap from not having to burn it for electricity that using it in cars would make a lot of sense, both financially and from a CO2 output stance.

That's just my math though. You can do your own math if you like. Please share your math if you think you get numbers that show electric cars are superior to natural gas cars.

Re:Hydrogen fule is not necessarily "green"

[Anonymous Coward]

dude... learn science... then politics... then get back to us on your ideas. ok?

Re:Hydrogen fule is not necessarily "green"

[Anonymous Coward]

All the stuff in the article about hydrogen being chosen because it's "green" is nonsense.

Hypersonic aircraft proposals tend to use liquid hydrogen for the same reason it was chosen for the Space Shuttle Main Engines: when burned with oxygen, liquid hydrogen is the most energetic (per unit mass) practical fuel available.

It is only 27% more efficient than kerosene, but because of the "tyranny of the rocketry equation" (which applies to jet aircraft, as well), a linear increase in fuel efficiency yields an exponential reduction in the total fuel required, all else being equal. It's not about lowering the fuel bill - it's about being able to cram enough fuel onto the vehicle to get where you're going without stopping for gas. Also, reducing the wet mass of the vehicle reduces the thrust required from the engines; this can lead to major weight and cost savings.

Another reason for the use of liquid hydrogen, specific to the concept plane shown at the top of the article, is that it is an excellent coolant. The plane pictured is the Reaction Engines A2, a proposed civilian derivative of the single-stage-to-orbit Skylon spaceplane. The key innovation shared by both designs is the use of a cryogenic pre-cooler to super-cool incoming air, enabling the engine to produce high thrust at high speeds without melting.

The engine concept used by the A2 predates the modern global-warming scare by a decade or two, and it was always intended to use liquid hydrogen for engineering reasons that have nothing to do with CO2-phobia.

Re:Hydrogen fule is not necessarily "green"

[Anonymous Coward]

You can look up measures of how much CO2 is produced by different fuel sources per generation methods, and find about 900 g/kWhr for coal and 800 g/kWhr for diesel/oil, and 500 g/kWhr for natural gas. Those are for large scale generators. The carbon bonds are not equal to the hydrogen bonds, and the difference in the end is smaller than just counting them up.

Re:Hydrogen fule is not necessarily "green"

[blindseer]

Okay then, I will revise my math. The g/kWhr for energy to moving the vehicles becomes:
900 / 50% = 1800 for coal-electric vehicle (CEV)
800 / 25% = 3200 for petrol powered vehicle (PPV)
500 / 25% = 2000 for natural gas vehicle (NGV)

At this point the life cycle carbon output comes into play. How much more heavy metals are needed for the batteries in the CEV vs. the NGV? How much more mining and refining is needed to produce those batteries?

I will admit my back of the envelope math was off by a bit I was still well within order of magnitude. Electric vehicles are not the "zero emission" vehicles they claim to be so long as we burn coal for electricity.

To be fair I'll add the 20% factor for electricity made from "green" nuclear, hydro, and wind.
900 / 50% * 80% = 1440 for coal-electric vehicle (CEV)

Even that makes CEV and NGV within 30% to 40% of each other. New engines announced this last year claims to increase internal combustion efficiency to 40%, making total vehicle efficiency close to 33%.
500 / 33% = 1500 for natural gas vehicle (NGV)

That puts NGVs at near parity with CEVs. Then there are some real bonuses for natural gas beyond being "green". Cost is a big one, as NGVs share many parts with PPVs that makes production and repairs inexpensive and easy to find. There is the possibility for dual fuel with petrol from those that have difficulty finding natural gas stations. CEVs can share this as a plug in hybrid but that adds to the cost, weight, and the reduction in efficiency that comes with that weight. NGVs have increased range between fill ups and reduced time to fill up compared to CEVs;.

Not all bad things for CEVs. Electric motors can achieve performance and noise reduction that internal combustion vehicles cannot match. If natural gas/petrol dual fuel electric plug-in hybrids come to market then we get the best of them all, IMHO.

Re:Hydrogen fule is not necessarily "green"

[Anonymous Coward]

The one disadvantage of natural gas is that any leaked methane could be much worse than a reduction in CO2. But no one has done a very good job of quantifying how much is lost in production, distribution, and use. Gas distribution companies report anywhere from 1-6% unaccounted for in distribution, which includes things other than leaks like rounding errors, but doesn't count end use loss beyond the meter.

Re:Hydrogen fule is not necessarily "green"

[Beck_Neard]

> Assuming an electric car gets twice the thermal efficiency compared to a petrol car I'll do some math

Your very starting assumption is wrong. ICE engines are, at best, 25% efficient. This is for hybrids; old-school gas cars are closer to 16 or 17% efficiency. When I said they're very inefficient, I meant it.

Electrical engines are very efficient. 90% efficiencies aren't unusual. The Tesla Model S gets 68% wall-to-wheels efficiency (from plug to battery to motor to wheels).

So adjust your math from 2x to 4x.

Re:Hydrogen fule is not necessarily "green"

[Anonymous Coward]

Some of us have solar panels on our roofs that power our EVs.

There is no way to do any math to make EVs look bad. I will even correct your error that you forgot all the pollution in making the gas/petrol in the first place and transporting it to the station. Let alone how many people were involved and had to drive to jobs and used gas to get to work to drill, pump, refine, and sell it. My solar panels are just sitting there working as long as the Sun comes up.

Cosmic Radiation att 33km!

[Unsichtbarer_Mensch]

How come noone seems to address the issue of the very high cosmic radiation exposure at such a high flight alitude? Sure, because of the shortened travel time, the effect would be somehow mitigated, but would it be enough to complete compensate? Seems to me passengers will have to wear space suits :p

Re:Cosmic Radiation att 33km!

[stoatwblr]

"How come noone seems to address the issue of the very high cosmic radiation exposure at such a high flight alitude?"

1: It isn't high enough to be of any concern for the flight durations in question

2: Space suits have no cosmic ray protection in them.

Re:Cosmic Radiation att 33km!

[rpstrong]

The plane is slated to have ceramic panels in order to handle the heat - would such panels block the radiation?

I'll believe it when I see it

[Borgmeister]

This probably won't happen. Yet another pie in the sky proposal that'll lead nowhere, such as the British Skylon project. The reality is that Concorde required considerable national investment from the Great Britain and France. With the advent of high speed internet, the need to shift an actual human at high speed from A to B is lessened - this is why we now have two double decker models of passenger jet (747-400 and A380) and no supersonic airliners (either TU-144 or Concorde). Shifting materiel is done at a leisurely 23 knots on a cargo ship. I'm not necessarily happy with the way things have panned out, but that's nevertheless how they have. :(

Just once difference.

[thegarbz]

Just once difference, we're talking Brussels to Sydney. The answer is more:

15min security check
1.5 hours binge shopping duty free goods and sipping on latte at the gate. Bonus points if you get to spend it in the lounge with a nice whiskey.
3 hours flight time.
10min bag wait.
10min customs.

Don't let America ruin flying for you. Not every country in the world is batshit stupid when it comes to air security.

Re:Just once difference.

[stud9920]

I second that. Up until last spring, we had to walk down, then along a loooong tunnel, then back up. Now they made a direct junction, from entrance to gate it's about 15 minutes tops

Reason for Brussels to Sydney

[140Mandak262Jamuna]

This plane would take 2.5 hours to go up and come back minimum. Crossing the half the globe at the higher atmosphere is just 25 minutes. So the flight times are like: 2hr 30 min for Brussels to Brussels, 2 hr 35 min for Doha, 2hr 40 min for Delhi, 2hr 45 min for Manila, 2hr 50 min for Sydney!

Why not Internet speed?

[tomhath]

Video conferencing has gotten so good, the demand for fast business travel is shrinking. I find it hard to believe there is enough market for pleasure travel at supersonic speed to support it; especially if it means traveling to an intermediate hub airport versus a slower but non-stop flight

Re:Why not Internet speed?

[iggymanz]

the really good salespeople and managers know face-to-face is best and irreplaceable. such people will never settle for videoconferencing

Sounds good news Friends!

[andy carrol]

Super Fast Lapcat II Hypersonic Airliner reaches you within 3 hours from Brussels to Sydney. That's sounds great news with airport security checks for US.

Not optimal, but nice

[Anonymous Coward]

Not optimal because at $5K wach way, even in 2030, is not something just about anyone can afford. But it is better than those ridiculous claims from Boeing and their latest "superliner", which is no faster than existing planes, more efficient (which implies more earnings for airlines) and whose "revolutionary" advantages for passengers are windows a teeny-weeny bit larger, plus higher atmospheric pressure and humidity in the cabin. This is not revolutionary, but pathetic.

I've been face to face with a grizzly

[Anonymous Coward]

I met a grizzly hiking once. I raised my arms and yelled "fuck off" and it looked at me and wandered off. Unlike the fucking spider or whatever that bit me outside of Cairns that left a festering hole in my leg for 3 weeks.

Chillagoe 7/10, would return, but only with a flamethrower.

Brings back memories.

[Anonymous Coward]

Anyone else get a "Land of the Giants" vibe...

our tax dollars at work

[Anonymous Coward]

the tax payer - that is you and i - is gonna wind up paying zzillions so millionairs can fly quick

what a great world when rich people get welfare

Re:our tax dollars at work

[Anonymous Coward]

and you have a problem with this ?
commie; we are supposed to tax the poor to support the job creators like Ms Fiorina (kinda sexist to call her carly or not ?)

why i love slashdot

[Anonymous Coward]

people take seriously ludicrous garbage
my fav was the yes, we can mine asteroids for metals by crashing them into the ocean thread of a few years ago.

Are you guys (I'm assuming guys) all Trump supporters or what ? (altho, as Krugman points out, the economic "plans" of trump actually make more sense then Jebs! plan !)

all you really need to know

[Anonymous Coward]

read this, and just replace "mars" with "supersonic transport"

http://www.nytimes.com/2015/09/21/opinion/lets-not-move-to-mars.html?ribbon-ad-idx=7&rref=opinion&module=Ribbon&version=origin&region=Header&action=click&contentCollection=Opinion&pgtype=article