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

[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

[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

[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

[PopeRatzo]

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

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

Brussels to Sydney

[turkeydance]

who would want to do that?

Re:Brussels to Sydney

[sycodon]

Australia:

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

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]

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,

[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]

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,

[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.

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.

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

[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).