Skylon: A Plane That Can Fly Anywhere in the World in 4 Hours | Hacker News Reader

Skylon: A Plane That Can Fly Anywhere in the World in 4 Hours

futurism.com

48 pointsmiraj46 comments

REL has been developing Skylon since the 1990s, and has done nothing but suck up research dollars ever since. It hasn't ever created a testable engine, let alone a testable plane. The whole idea is a set of nearly insurmountable problems.

For just one example, they claim that it will be an enormous plane filled with hydrogen, so on re-entry it will have a large cross section but low mass so it will be slowed by atmospheric friction more rapidly than the shuttle. But it's also going to have wings and turbulent air flow, it's a bad shape for atmospheric re-entry. This is project killer if they can't handle re-entry, and they are no where near a physical test of it.

>The SABRE Engine is a hybrid air breathing rocket engine. In the past, attempts to design single stage to orbit rockets have been unsuccessful largely due to the weight of oxidiser, such as liquid oxygen.

Carrying your oxidizer with you allows you to avoid losses related to the accelerating (which is slowing down in the plane's frame or reference) of the unnecessary 80% of the incoming air, ie. nitrogen. Decompressing that nitrogen back in the working chamber (which also decreases the efficiency of the chamber) allows to recuperate back some of that loss. At slow speeds (like typical jet) - most of that loss is recuperated back. The higher the speed the bigger the share of that unrecuperated loss, due to higher temperatures, etc... Granted, thrust-wise having larger working mass moving slowly would usually/theoretically be welcome (larger prop effect, one example in application to rockets - air-augmented rockets like http://www.astronautix.com/g/gnom.html), yet at higher speeds other things like that mentioned loss, efficiency, complexity/cost, etc. start to become major factors.

Additionally the potential amount of oxidizer saved while reaching the orbit is really not that much. Quick mind napkin calculation shows that on the order of several tons per engine which is close to a wash given the additional hardware (thus weight) necessary for such scheme to work.

If anything, 2 stage system with returnable 1st stage should work much better/cheaper/robust as we can already see from SpaceX and SpaceShipOne. Developing such first stage - basically a plane for quick acceleration to M5-M8 and returning back to the airport should be pretty simple relatively to any other orbital/suborbital or long-range supersonic effort.

If a plane of this design ever flies, I will purchase a stout fedora and eat it one sitting.

There are SO MANY things that can go wrong, esp. at the micro level, which will see the engine turn from a chiller to a block of ice, then melted metal in a fraction of a second. Plus this is being developed in the UK, a country whose aerospace industry lost its entrepreneurial spine when the de Havilland Comets started falling from the sky and never really recovered IMHO.

No spine, but with France it produced the Concorde, a wonderful, ridiculous, marvellous machine.

You had better start shopping. It was not just a UK effort. I first heard about this technology in Australia ten years ago where it was being touted as reducing the Europe-Sydney route to something more bearable. They have done many successful early prototypes of this design and other scramjets - flying ones.

The fact that they can't seem to raise £200M (2013) [1] to build a prototype does seem either troubling about its feasibility OR indicative that something's very wrong with capital markets (or that they're working on traditional military aerospace "we'll get it done in 10 years" pace).

On the other hand, I'm sure harnessing explosions to propel heavier than air craft into orbit also seemed insurmountably technically impossible at one point.

[1] http://www.bbc.com/news/science-environment-23332592

>Who wouldn’t want to have breakfast on the French Riviera, take a walk along the Great Wall of China in the afternoon, and then cap off the evening by staring at stars above the Alaskan wilderness?

Ok, I know this is just aspirational ad copy... but, realistically, this looks very bad with respect to planetary health.

We're trying to get people out of cars and into public transit or bikes --this would do the opposite of that. It would allow the wealthy to further increase their carbon footprint. In addition, even if we figure ways to counterbalance carbon pollution, it would in the least increase throughput in a given area due to reduced travel friction. Already some national parks exhibit detrimental effects from too many people visiting -such that some require advanced limited reservations.

Yeah, so the answer to that (who wouldn't want to...) is 4 main groups:

1) Anybody who cares enough about others (i.e. "the planet") to refrain.

2) Anybody who can think of a better use for [unknown dollar amount, probably 6 or 7 figures]. This includes philanthropists like Bill Gates & Warren Buffett (who might also be in group 1), as well as most other people, who don't have that kind of money sitting around.

3) Anybody who's happy right where they are. Includes those who actually enjoy being with their spouse and working at their job.

4) Anybody well-traveled enough to know those places aren't actually all that amazing, and that your same problems always await you back home.

Better question is "who WOULD want to?" Well if you subtract or negate the above, you're left with restless, self-involved, probably young, very rich people trapped on the hedonic treadmill, who don't have much sense, and who think they deserve everything they have (yet it's still not enough) and who don't care or think about their impact on others.

How do you shed 400Mwh of heat in an area that small?

I would imagine the surrounding air would take some of the heat, but that's an incredible amount of energy to dissipate in such a small area.

Call me skeptical.

This is at least an order of magnitude more complexity and heat exchange than the Shuttle Main Engines (SME's) ever succeeded in doing. And were constantly maintained and babied by NASA staff for less than a dozen flights a year.

Cryogenic hydrogen is a really nasty chemical. It's so small it'll worm into your linings, plumbing, metal walls, and flake them apart with the temperature swings. Other combustible fluids condense on the outside of the plumbing if you're not careful.

NASA and the DOD tried to make this with Copper Canyon / NASP / X-30. They couldn't make it fly, and they had cubic billions of dollars to try with.

Today, the children of Von Braun, tail-sitting rockets like the DC-X, which is Blue Origin and Space-X, are progressing towards the amazing reality of boring reliable transport to space without crazy wings and dwelling in thick atmosphere.

https://thehighfrontier.blog/2016/01/02/reagans-impossible-d...

Maybe they're going liquid hydrogen for the fuel? Or another cryogenic? That gives you a lot of "waste cold" that you can use for cooling charge air and the rest of the engine.

I'm a big fan of LH2 planes. Tupolev actually built one just before the wall fell [1]. Airbus did a big concept study in the 2000s that indicated it would be on par with normal airliners once you eked out all the optimizations.

Then everyone decided to go gradual biofuel phase-in instead, which I'm decidedly skeptical of. Sure I get that the CAPEX of going LH2 is a lot worse, so for someone optimizing on a < 10 year horizon it looks better. But are biofuels really going to get us all the way we need to go eventually?

[1] https://en.wikipedia.org/wiki/Tupolev_Tu-155

I’d been happy if we could just get commercial supersonic flight back. NASA is working on quiet supersonic, which will hopefully do the trick:

https://www.extremetech.com/extreme/251718-nasas-quieter-sup...

I'm all for doing engine research. But the economics seem pretty clear that if you can't afford to routinely fly in luxury first class suites on 787s, you probably wouldn't be able to afford to fly in a supersonic jet either. (Which means that it's unlikely anyone would build one given that there are barely any all-business class large jets today.)

Hey, while we’re making up economic data, let me take a crack at it. Business class is usually full when I fly. When I flew to South Africa this year (15 hours direct) from JFK, I asked if first class always sells out, and I got a chuckle and a yes. So, I believe there is a sufficiently large market for supersonic flight. However, you need to be able to fly supersonic over land.

You'll find many of those higher class seats are filled by frequent flyers on upgrades. Business is almost always full because there are more frequent flyers who bought economy who are eligible for upgrades (or want to use their own mileage to upgrade) than there are left over business class seats.

Flights in the 8 hour range, sure. But Air Canada's ~15 hour Vancouver-Australia flights are notorious for never having any upgrade space available.

I'm guessing that new supersonic jets will be taking the (formerly) 16 hour routes first.

YMMV, I guess. I can get upgrades using miles pretty routinely from US East Coast to Asia.

The other challenge with those sorts of routes though is that you also need a lot more range than the Concorde had. Its range was around 3500 to 4500 miles depending on various factors.

There have been a number of studies on the viability of commercial supersonic flight.

https://niskanencenter.org/blog/supersonic-overland/

While your anecdotal experience may have formed your opinion, others have taken a deeper look into the problem.

[Update]

You should read the section on economic myths: http://www.supersonicmyths.com/#supersonic-myths

“Everyone stands to benefit from supersonic transport. Nonetheless, early technological adoption among a luxury or business class of consumers is a recurrent phenomenon in the spread of innovation. As Everett M. Rogers showed in his seminal work, Diffusion of Innovation, early adopters are often willing to pay a high initial price for a new product due to greater resources and the pursuit of social status. From there, firms reinvest profits in product design and use the benefits of volume and scale to introduce subsequent product versions with more and more mass market appeal. This is how cell phones went from a luxury used by Wall Street's Gordon Gecko to being in the pockets of poor farmers in Africa. It's also the strategy Tesla Motors is using to mainstream affordable electric vehicles.”

Actually, supersonic business jets (which is what the research in that link is focused on) seem like an entirely plausible market. It's a market that already pays a huge premium for convenience.

That's a big difference from viability as a commercial passenger jet in a market where so many people buy on price. Not impossible. But the economics seem very challenging.

you also need a lot more range

If you can fly suborbital, range becomes much less of a factor, since you can avoid most of the atmosphere.

>However, you need to be able to fly supersonic over land.

that current restriction of supersonic overland looks to me the same as that 4 miles per hour restriction on the car speed during the second half of the 19th century in England. Had all the good sounding reasons too ... (note: i grew up in USSR at a navy base and supersonic booms were just a fun part of my childhood, so i don't share that animosity toward the boom :)

Lots of people in business class and first class are frequent fliers on upgrades. The number of people paying full fare is relatively small proportion.

Suddenly that plane hauls 2000 people a day instead of 500.

You will have to factor in the 4x associated costs as well (fuel, maintenance , flight crew, airport costs, etc).

I have 0% knowledge on commercial flight OPEX, but at first glance it doesn't sound as simple.

The less time on the ground, more money a company makes.

This probably is true on the air too, granted that you have a similar efficiency and fuel combustion.

Doesn't really work like that. There are substantial dwell times in the cycle that no amount of enroute speed can elimanate...

Unload the passengers

Unload the luggage

Clean the cabin

Load the next set of passengers

Load the luggage

Taxi to the runway...

A supersonic jet is almost certainly going to be (much) smaller than a widebody subsonic passenger aircraft. Furthermore, you probably wouldn't need to make the seating super-luxurious but people paying premium prices are still going to expect at least the level of seating and service you get in domestic US business.

I think the most likely next step is supersonic business jets. That market can afford the cost much easier than commercial airlines, and there appear to be companies who are making significant progress towards building them.

https://boomsupersonic.com

They already have 76 orders:

http://www.wired.co.uk/article/virgin-supersonic-travel

This will give rise to even more crazy commute stories.

"To work in the bay area, she has to live a 4 hour plane ride away in Western China. She wakes up at 2pm "the day after" to get into the office by 8AM SF time."

It would have to be 2pm on the "same day", unless the plane is so fast that it goes backwards in time.

r/theydidthemath

r/theydidtheMONSTERmath

sorry, couldn't resist

apology excepted

Forgive my ignorance, but how does cooling super hot air super fast make a jet engine go faster?

Well, you probably know colder air has higher density (or conversely, that hot air expands). Now a jet turbine compressor stage, just like a turbo on your car, moves a fixed volume of air per second into the combustion chamber. But the actual combustion cares about the mass of air (well, oxygen). So a higher density/lower temperature gives you more power with the same turbo. This is why cars have intercoolers.

I think cooling it allows you to increase the density to the point that the air can be used as oxidizer for the rocket engines.

But I am still confused though - part of the article talks about how the breakthrough is that it doesn't need to carry oxidizer because of the precompression / cooling system, but then it talks about how it could operate in orbit for 14 days, where no about of compression will get you enough oxygen...

They mean it needs to carry less oxidizer. The engines switch from air-breathing to on-board liquid oxygen at some point.

They have to switch to onboard LOX when intake air gets too hot to cool sufficiently. That occurs at Mach 5.5. You need to achieve Mach 30 to reach orbit, so all this fancy engineering can only going to be used for a small fraction of the journey to space.

It's a small fraction of the velocity, but a significant fraction of the mass. E.g. I think for the reusable missions, the Falcon 9 first stage cuts out around Mach 6, but the mass of the first stage (which is mostly liquid oxygen) is about 80% of the mass of the rocket.

If I'm not mistaken, it doesn't directly make it go faster. What it does do is let you use less-exotic (i.e., lighter weight) materials for the front end of the engine without having them melt. Less weight -> more speed.

because that cooling happens before combustion making the intake air denser and the difference in kinetic energy of intake vs exhaust larger.

It is a fine line since you might end up spending more energy (in terms of drag mostly) than you can recoup by making the combustion more powerful/efficient.

Also, cold air does not have 'more' oxygen than hot air - its just more dense and hence has more oxygen per unit volume.

Should be tagged as 2014. The included video interview is even older, from July of 2012.

I can't find any recent news about them. Only what they post themselves, which doesn't seem to have much concrete information: https://www.reactionengines.co.uk/category/news/

To tell the truth I would be so much happier taking 3 days to cross the Atlantic on an airship with a cabin and a bar.

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