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Hypersonic Flight ‘Breakthrough’ Could Have Us in Tokyo by Lunch (wired.com)
43 points by jordhy 1695 days ago | hide | past | web | 45 comments | favorite

I wonder if it would have any effect adding a statoreactor tube to the end of a rocket engine ( as a kind of postcombustion chamber) to take advantage of all that heat. Maybe adding some fuel to that part to make use of atmosferic oxigen to increase power. Above 30km you may drop it. I don't think it would be too heavy as it doesn't have moving parts. The question is if it would generate power enough to be worth all the trouble.

I'm not sure I understand what you're suggesting, but it sounds like some form of ram afterburner?

Yes exactly. Has it been done or studied?.

I do not understand how the physics of a ram afterburner would work. A ram duct generates compression via aerodynamic drag. It slows and compresses the air forced into it by controlling shocks.

The expansion stage of a brayton cycle engine maximizes exhaust velocity rearward and hence by Newton's third law creates thrust. Constricting the exhaust will only reduce efficiency.

If you're talking about an expansion duct with secondary combustion, that has nothing to do with ram effect and is just an afterburner.

By and large afterburners are hideously inefficient, but many military craft still include them because it is easier to manufacture an afterburner tolerant of secondary combustion temperatures than a turbine. SABRE erodes this motivation as the incident temperature into the flame holders (or rocket nozzles) is dramatically lower than common in a turbine engine, so you can get more of the energy possible from the oxygen density of the engine's intake flow without secondary combustion.

I thought another big issue with flying at such fast speeds was that you end up tearing pieces off your fuselage every time... This looks like one piece of a bigger puzzle to achieve what the headline of the article is suggesting.

Air-frame heat is definitely an issue, but it's solvable. According to a BBC documentary that's on youtube, the Skylon design uses the same concept as the SR-71, which is a corrugated skin that allows a great deal of thermal expansion and limits conduction of heat from the skin to the air-frame. They also apparently have a novel composite material, which could be a big advantage since machining titanium alloys like the SR71 used is a serious pain in the ass.

That and cost. No one is willing to pay for supersonic flight, and the sonic boom makes it obnoxious over land.

Skylon could fly high enough to moot sonic boom issues, but I think you're right about lack of market demand for transportation. I think aerospace folks may underestimate how continued advances in communication networks will erode demand for travel of all forms, let alone prompt travel.

Of course the military will always be giddy about dropping bombs on whatever poor soul they want as promptly as possible...

According to my Dad (who is clearly the most reliable authority in the world :-() the reason the Concorde failed is because Boeing lobbied the government to get it banned over the continental US so they could sell the 747.

He's basically saying all that stuff about noise is mostly bunk pushed forward by Boeing to get rid of the competition. You'll note BTW the 747 and Concorde both came out around the same time and you probably also know the 747 was never designed to be a passenger plane. It was designed to be a military cargo plane but lost the contract to Lockheed's C-5A so Boeing needed it to sell as something else.

He, my dad, claims the NYC to LA route was the most lucrative and that without it Concorde didn't stand a change.

I have no idea if there's any evidence to back up his story. Maybe someone else out there has more info.

People are willing to pay for supersonic flight. Concorde made a profit on most of it's flights, and it was only after the World Trade Center attacks and subsequent downturn in international commercial flight that it became a problem. Also, because not many Concordes were made, the R&D costs were never properly amortized.

The sonic boom however is an issue - Concorde was limited to a small selection of routes that passed mainly over water (e.g. London -> New York) because it was not allowed to go supersonic over a lot of countries. If you could fly supersonic all the way from London to Tokyo, or San Fransisco, or Sydney, then I'm sure it would be worth even more.

Wikipedia disagrees about the profits on "most of its flights". It says "it is reported that British Airways then ran Concorde at a profit, unlike their French counterpart". That is half the fleet for slightly over half the years of operation.

The linked-to http://news.bbc.co.uk/2/hi/business/2935337 says:

"British Airways […] was reckoned to make a £20m annual operating profit from its London-New York Concorde service."

But also:

"By 1975, the year before commercial launch, more than £1.2bn - at least £11bn today - had been spent."

So, their margin on investment was 1.6% or so, starting about ten years after the investments were made.

They would have needed a lot more planes to get their investments back. To fill them with passengers, fares would have to drop. Lower fares means they needed even more planes, etc.

Concorde also was limited to long distance flights. On shorter routes, its fuel economy did not compensate for a slightly shorter (boarding+flight+deboarding) time.

I think 9/11 was coincidental and unrelated. The important trend in 2001+ was the growth of telecommunications phenomena that reduced travel demand. I am not sure if the sonic boom was nearly as big a problem as it was made out to be. I think we can do some cursory math.

If 30% was at 50% of the speed, the total distance covered would be 85% less, adding about 20% flight time increase. Something that normally takes 8+ hours now take 3 or 4 hours. Did this kill the concord?

Airline stocks went down almost 40% the next day. Yes, the economy went down because of other factors, but the immediate hit to airlines was definitely caused by 9/11.

It was very reliant on dotcom and banking transit between London and NY. The sitcom bust killed a lot of that.

And of course, if you leave NYC after breakfast and head to Tokio you won't get there by lunch

More likely you'll get there for dinner and a night out

At Mach 5 this will take 2h (not considering acceleration/deceleration times)

Then standing in line for two hours at security will be even more ironic.

Anyone who can afford this ride will be part of a paid Get Out of Grope program.

Does this happen anymore? I flew out of Boston the day before Thanksgiving (when I would imagine tons of people are traveling) and it took <5 minutes to get through security. Same thing on the way back.

One data point doesn't mean anything... It's the uncertainty that you might spend 1h in line that makes you waste time in the end.

No, but this is HN.

It depends on when you fly. I haven't had a really bad (1 hour) security wait since 2002, but when the airports are really crowded, I've seen it get close to that.

Of course, assuming they allow supersonic flights over the continental united states. I imagine it would probably be severely restricted due to the noise concerns from the sonic boom.

The great circle route from NYC to Tokyo flies over virtually no part of the continental United States, aside from New York. (Canada, on the other hand, would be below the plane for much of the trip, but is sparsely populated enough if the north that I suspect you could route around major population centers easily.)

Exactly, you have to worry mostly about the coldest parts of Canada and maybe Russia


Ok, thats a good point. I'm not farmiliar enough with the globe to remember the great circle routes.

Which still doesn't change the times involved getting to and from the airport. These are often worse than the flights themselves. Better to engage remotely rather than travel at all.

Also discussed extensively here:


Does anyone know how practical this is? Is it economically feasible to do this on a jetliner, at Concorde prices? A business jet?

"could have us", who is us?

The engine has never been the problem. Heat dissipation is the problem.

Meh... you know what I want? I want to be able to go to Tokyo and not have the ticket cost multiple fucking days of work. In 2012, four-digit airfares for coach are fucking inexcusable. We were supposed to be better than that, 20 years ago. And don't get me started on business class: those tickets are more than some people in the world make in a fucking year. I want travel that doesn't belch a bunch of CO2 into the air, leaving our grandchildren with a world where there are palm trees in Winnipeg and a year-round hurricane season. That's what I care about. If this Mach-5 travel costs the same as airfare currently does, and burns a bunch of fucking hydrocarbons to get there, then I'm not impressed.

I'm sure the technology is cool, but would someone please solve the real problem? The real problem is that transportation hasn't improved since the 1960s. In the US, we call exorbitantly-priced, 130-mph trains "high speed", we use airplanes for mid-distance travel and it's ass-expensive as it should be because it makes no economic sense, and most of our transportation relies on burning fossil fuels in tin cans that can't be safely operated above about 90 miles per hour. Solve that one, please.

What are you talking about? China has almost 5000 miles of high-speed rail that runs over 150mph. Japan is hard at work on replacing their "slow" 186mph trains with 310mph maglev trains.


Tesla is hard at work selling electric cars and making a profit. Google has a self-driving car that works. People are solving problems. Getting hypersonic jets to work would be great.

Now the problem of getting people to adopt any of this in the US? Engineers can't solve those problems. Someday the US will finally get a real high-speed train, but it looks like Japan will have maglevs first.

My bitching was largely US-centric. I should have clarified that. However, high airfares are a world-scale problem.

My malaise is more general. In the 1950s-60s, the economy was growing at 5-6 percent per year because people actually had the vision to invest in basic research and technology. In this day in age, we have a million IUsedThisToilet.com startups built to be acquired, but very little effort going toward real work.

The last few flights I've taken, 60% of the ticket price has been taxes. I understand the need for taxation, but that seems a little absurd to me. It'd be a really quick way of slashing ticket prices...

>> The real problem is that transportation hasn't improved since the 1960s.

Yes it has. Guess what? There are a lot more people and they want to travel just like you, basic supply and demand. Planes are far more advanced then they were back then.

>>That's what I care about. If this Mach-5 travel costs the same as airfare currently does, and burns a bunch of fucking hydrocarbons to get there, then I'm not impressed.

It will cost more and burn even more hydrocarbons(Of course skylon is an unrealistic satellite launch system and this article makes no sense ). Engineering problems are hard, the development work done in the 1960s is child's play to what is being done now. If things suck so much you should be happy that you will change things for everyone and make a bunch of money in the process.

>> In the US, we call exorbitantly-priced, 130-mph trains "high speed"

They are exorbitantly priced anywhere. We don't get anywhere close to that over an entire distance because existing and even proposed systems (California) won't be fully high speed lines. That isn't a question of technology just simple budget and priorities. No country in the world has replaced mid-distance travel with high speed rail. France is barely finishing out its high speed network that covers a much smaller country than ours.

Transportation CO2 emissions make up a tiny fraction of total greenhouse gases. Water vapour is by FAR the biggest greenhouse gas. I wonder if a 787 burns more hydrocarbons flying 250 people from NY to LA than 250 cars driving that distance? Roughly ~9000gal (2500mi 787 @ cruise) is 36gal per car. Assuming everyone gets perfect highway mileage even if they're Prius it wont get them the whole way (50MPG*36gal=1800mi). And that's not considering the energy required to build and maintain 250 Prius cars vs. the cost of one 787. The retail cost alone for 250 Prius is nearly $90M. A 787 is more like $250M, but lasts a least 3x longer than a car.

Transportation has improved since the 1960 by a HUGE amount. Modern cars, trains, and airplanes are significantly better (safer, cheaper, more efficient) than those in the 1960s. I'm curious how much travelling you did in the 1960s compared to today?

Transportation CO2 emissions make up a tiny fraction of total greenhouse gases. Water vapour is by FAR the biggest greenhouse gas.

Water vapor is the largest greenhouse gas, but it's a relatively constant contribution; it's not part of anthropogenic contributions to greenhouse gases (which is usually what people are referring to in this sort of context).

Good point. I'm not trying to start an off-topic climate change debate, just trying to step back and look at the problem a little more broadly, but there's at least one big error in my calcs as has been pointed out.

250 * 30,000 = 7,500,000

ah! whoops, one too many zeros (I used $35K) :P

They'll probably never let humans travel by air at hypersonic speeds, its far to dangerous.

They'll simply use Evacuated tube maglev(Elon Musk's HYPERLOOP) for long distances, same hypersonic speed.

Looking forward to breakfast in San Fransisco, Lunch in LA, and Dinner in Washinton DC.

Haven't they let humans travel by air at hypersonic speeds already?


Concorde has a max speed of just over Mach 2.0. Hypersonic means Mach 5.0 or higher. The rocket-powered X-15 max speed was 6.7, and of course the Space Shuttle also went faster than Mach 5.0, so yes, humans have already flown at hypersonic speeds.

HYPERsonic means Mach 5.0 or higher


Why is it far too dangerous?

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