
Skylon: A Plane That Can Fly Anywhere in the World in 4 Hours - miraj
https://futurism.com/skylon-plane-can-fly-anywhere-world-4-hours/
======
valuearb
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.

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trhway
>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](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.

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verytrivial
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.

~~~
nthcolumn
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.

~~~
ethbro
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](http://www.bbc.com/news/science-environment-23332592)

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mc32
>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.

~~~
rdiddly
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.

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sathackr
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.

~~~
nickhalfasleep
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.

~~~
nickhalfasleep
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...](https://thehighfrontier.blog/2016/01/02/reagans-impossible-
dream-the-x-30-national-aerospace-plane/)

------
melling
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...](https://www.extremetech.com/extreme/251718-nasas-quieter-supersonic-
plane-project-soon-take-flight)

~~~
ghaff
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.)

~~~
melling
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.

~~~
ghaff
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.

~~~
cperciva
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.

~~~
ghaff
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.

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

[https://niskanencenter.org/blog/supersonic-
overland/](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](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.”

~~~
ghaff
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.

------
amelius
This will give rise to even more crazy commute stories.

~~~
thebiglebrewski
"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."

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

~~~
thebiglebrewski
r/theydidthemath

~~~
roryisok
r/theydidtheMONSTERmath

sorry, couldn't resist

~~~
thebiglebrewski
apology excepted

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

~~~
matheweis
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...

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

~~~
valuearb
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.

~~~
vilhelm_s
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.

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filipncs
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/](https://www.reactionengines.co.uk/category/news/)

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boznz
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.

