
British aerospace company claims biggest engine advance since the jet - james_ash
http://uk.reuters.com/article/2012/11/28/uk-science-spaceplane-idUKBRE8AR0R520121128
======
jws
The BBC article, <http://www.bbc.co.uk/news/science-environment-20510112> has
some nice explanatory graphics.

It appears they are using a liquid nitrogen boiler to chill a helium loop
through their heat exchanger and in turn chill the air.

So, perhaps someone better at these calculations can help out, cooling
incoming air by 160°C by moving nitrogen from -195°C to -15°C is going to
require them to haul up liquid nitrogen and cool a bunch of atmospheric
nitrogen that they don't really need. The heat of vaporization is the key that
will make their solution win, but by what factor? How many grams of nitrogen
must they haul to chill a gram of atmospheric oxygen?

~~~
russss
The liquid nitrogen is just used for the ground tests. On the Skylon itself,
this cooling capacity will come from boiling the liquid hydrogen fuel.

~~~
iwwr
Skylon would basically use the cryogenic fuel as a giant internal heat sink.

A more fanciful application of the concept:
<http://tvtropes.org/pmwiki/pmwiki.php/Main/StealthInSpace>

~~~
felixfurtak
How is this different to HOTOL ?

~~~
zizee
Similar concept, different design.

------
mtgx
Elon Musk was specifically asked about this technology when he was at Martin
School last week. He didn't hear about it, but he seemed skeptical that it
would work better than rockets. His response here:

<http://youtu.be/c1HZIQliuoA?t=48m55s>

SpaceX might still be the first one with a re-usable rocket if they finish the
Raptor engine in 3 years. Plus, his could actually be used to land on Mars,
while this can only be useful where you still have atmosphere and oxygen - so
only for launches to orbit.

But it's great to see more private companies competing in this area. And even
if nothing comes out of it for space travel, it might still turn out be a
useful technology for airplanes.

~~~
UnoriginalGuy
> so only for launches to orbit

Isn't that our biggest challenge right now? I like how dismissive you are of
it, like we have somehow overcome that and are now on our way to Mars any day
now.

If someone was able to reduce the cost of going into orbit by as little as 10%
that would be a MASSIVE achievement. Getting out of the atmosphere is still a
massively costly, logistical, and dangerous challenge.

~~~
btilly
But you don't reduce the cost of going into orbit by 10%. Not even in the
absurdly best case.

Let us take Elon at his word that increasing the size of the booster stage by
5-10% can replace these engines entirely, and assume that it actually is 10%.
The booster stage is mostly fuel, which varies as volume, but the costs are
all in the metal part, which scales as area. So this size increase costs you
at most 6.6%. It actually costs less because the complicated rocket thrusters
are left unchanged. So let's say 5%.

But we're not reducing the cost of the whole rocket by 5%, just the booster
stage. If we assume that the booster stage is, say, 70% of the rocket we're
only saving a maximum of 3.5% in reductions on the existing rocket components.

But we haven't yet factored in the cost of the new component. Which is, after
all, very much like the existing engines except more complicated. In a Falcon
9 we have 9 rockets, so each one is about 11% of the cost of the total. If we
strap on 3 of these new things, which are much like rockets except more
complicated because of the whole hybrid thing, they each can cost a maximum of
about 1.2% of the total cost to stay within our budget.

So unless these things, which are more complicated than rockets, cost you
1/10th as much, you don't get any cost saving at all. It is difficult to see
how they can be this cheap.

Meanwhile, back in reality, Elon has plans to reduce the cost to orbit by
another factor of 10 in a similar time frame to when these might actually
become commercially available. (He's already reduced launch costs by a factor
of 10.)

A large part of how he's managed to reduce costs so much is that he does this
kind of common sense analysis in his sleep, and uses it to ignore everything
he has to ignore, and zero in on what he needs to pay attention to. The
numbers on this technology simply don't add up for space.

(But they don't have to. A practical technology to double the speed of jets by
a factor of 2 will be extremely interesting to various militaries. Plus the
potential savings for the existing airline industry - which is a much, much
bigger market than space right now - means that they are going to have no
shortage of potential customers. Elon is simply not one of them.)

~~~
Gravityloss
A tank's weight is proportional to volume, not surface area, assuming equal
pressure and material strength.

Also, you often can't just simply stretch tanks - you need to increase thrust.
Otherwise your payload drops because of lower T/W and more gravity losses in
early flight.

~~~
btilly
_A tank's weight is proportional to volume, not surface area, assuming equal
pressure and material strength._

The weight of a full tank, yes.

The weight of an empty tank, no. An empty tank is mostly a shell, and the size
of that shell corresponds to area.

 _Also, you often can't just simply stretch tanks - you need to increase
thrust. Otherwise your payload drops because of lower T/W and more gravity
losses in early flight._

I am assuming that Elon Musk's 5-10% estimate takes things like this into
account.

Incidentally "early flight" in this case is very early. At the ground, oxygen
levels are a bit over 20%. But as you go up, oxygen drops off faster than
nitrogen, so oxygen intake falls off slower than drag. At some point you'll
gain nothing. I do not know what that point is, but the oxygen/nitrogen level
is part of why it is most efficient for commercial airlines to fly at around 9
km high. So it is really just a few km that you get a potential benefit. But
your top speed at that moment is a pretty small fraction of what you need to
get to orbit.

~~~
Gravityloss
Nope, the shell. In a bigger tank (similar material and pressure) the shell
has to be thicker. It's mathematically trivial.

------
starpilot
This is just rocket-based combined-cycle propulsion that has been proposed and
studied by various organizations over the years.

<http://en.wikipedia.org/wiki/Rocket-based_combined_cycle>

[http://investor.gencorp.com/releasedetail.cfm?ReleaseID=7085...](http://investor.gencorp.com/releasedetail.cfm?ReleaseID=708513)

[http://www.isset.org/nasa/nano/www.grc.nasa.gov/WWW/AERO/bas...](http://www.isset.org/nasa/nano/www.grc.nasa.gov/WWW/AERO/base/ccp.htm)

The concept is not new, but Reaction is probably the closest to a commercial
implementation. Also, it's not fair to compare it to the jet when RBCC isn't a
fundamentally novel form of propulsion, just a combination of existing ones
(like a car that is both gas and electric propelled). This is not something
that could supplant the jet.

Some people are comparing this to SpaceX's pure-rocket approach. Up until
yesterday, SpaceX and Scaled were working on their own type of combined-cycle
launch with Stratolaunch:
[http://www.flightglobal.com/news/articles/stratolaunch-
and-s...](http://www.flightglobal.com/news/articles/stratolaunch-and-spacex-
part-ways-379516/). The difference is that the jet and rocket would be
separate vehicles instead of fitting into one nacelle. It'd have some of the
advantages of using air as propellant as with a RBCC engine, but easier to
design I think.

~~~
Gravityloss
The precooler / heat exchanger is the SABRE's distinction. Ramjets and
scramjets don't have such. It enables low internal gas velocity and small
compressors and more thrust from a smaller engine and higher top speed than
jets.

It's like saying when the Wankel was invented that "it's just another internal
combustion engine". Sure, it is, but it's quite different from most of the
others.

------
robomartin
The MAGLEV Launcher.

<http://en.wikipedia.org/wiki/Rocket_sled_launch>

<http://www.reallyrocketscience.com/node/2393>

Using MAGLEV as a launch assist technology to offset the amount of energy
derived from burning tons and tons of fuel. Some of the articles estimate a
potential to increase payload by 80% compared to a conventionally launched
rocket.

If you want to get a little deeper into it, this is a good read:

[http://upload.wikimedia.org/wikipedia/commons/5/58/Maglifter...](http://upload.wikimedia.org/wikipedia/commons/5/58/Maglifter_Mankins.pdf)

Some fun data points:

    
    
        Power for large scale system: 10GW for 20 seconds. 
        Thermal Management system capable of dissipating 40GJ.
    
    

What's the probability of this ever being built? In the US, my guess is zero.
I could see the Chinese throwing money behind such a crazy project if the
numbers make any sense at all. If a system like this can significantly reduce
cost to orbit it could represent a huge competitive advantage.

~~~
schiffern
The payoff would be immense though. At datacenter electricity prices, the
fundamental energy cost to LEO is about 50¢/kg.

~~~
stcredzero
Fuel (energy) cost is less than 1% of the cost to launch. The big costs are
manpower, maintenance, and refurbishment.

~~~
ChuckMcM
That was the interesting takeaway from the Elon Musk talk about how cheap the
fuel was compared to everything else. Having the Skylon be reusable then
shifts some of the operational costs back to fuel.

Of course a plane that can fly a Mach 5 and 100,000' has other uses, the most
obvious one being the SR-71 replacement. Nothing like a bit of high speed
aerial surveillance "right now" to help folks on the ground make better
decisions. I'm sure _someone_ would pony up the $400M they need.

~~~
stcredzero
Yes, but having anything be reusable does that. If you can make up what you
would have gained with Skylon by making the fuel tank 5% larger, then the
opportunity cost of developing a radically new engine isn't worth it. Mach 5
does have other uses, though.

------
bernardom
From the article: "The company has deliberately avoided filing patents on its
heat exchanger technology to avoid details of how it works - particularly the
method for preventing the build-up of frost - becoming public."

I would think that for something like this, the patent system would actually
work fine. Anybody who tries to make this is going to be located in the US,
Canada, Western Europe, or Japan. It's not like they're going to make cheap
ones in China and India, and if they did it would be easily correctable with
the WTO. What am I missing?

~~~
JonnieCache
SpaceX doesn't have any patents either. Musk has specifically said this is
because in the long term their main competitors are the chinese, who treat
patents as recipe books.

~~~
bernardom
I appreciate the argument about SpaceX (and the other thoughtful replies to my
question). I just think that this case is fundamentally different from a
rocket company. This is something that, to make profit, would need to be used
by global airlines, where patent laws are much more enforceable.

My thinking boils down to this: if SpaceX comes up with a novel, patentable
way to improve rocketry, China can steal it.

If these guys come up with a much faster aircraft engine, even if China made
them for cheap, they could and would prevent United, Lufthansa, BA, and the
other big airlines from using it.

China can steal IP when it is used internally, or sold as consumer goods to
other countries that violate patent laws. They can't steal IP and sell it to
large multinationals.

------
timthorn
Unfortunate title here - British Aerospace was involved in the project some
years ago, but Reaction Engines is a distinct company and I believe they exist
despite BAe's "assistance"

~~~
javert
As an American, I parsed the title as "a British aerospace company..." not
"the British Aerospace company..."

~~~
user24
As an Englishman, I parsed the title the same way as you did, though I did
wonder if it meant BA.

~~~
robotresearcher
BA is British Airways. BAE Systems is the new name for what used to be British
Aerospace, which used BAe as its abbreviation, to avoid confusion with BA.

I don't know why it bothers me, but I really dislike the used-to-be-an-
acronym-but-not-any-more names. For example SRI (not affiliated with Stanford
so the S doesn't mean that any more), and my least favourite "HRL
Laboratories" which we have to pretend does not expand to "Hughes Research
Laboratories Laboratories". Yuk.

~~~
cadab
<http://en.wikipedia.org/wiki/RAS_syndrome>

------
Gravityloss
The problem with these advanced technologies is two fold

1\. it requires a large amount of hydrogen - which is not heavy so it looks
good on paper but is very cold and voluminous, meaning you need huge insulated
tanks. They are expensive to build, have bad mass fraction and are
aerodynamically problematic. Hydrogen is also expensive to handle in systems
and infrastructure.

2\. the dry mass of an air breathing engine sucks because they process gases
(rockets process liquids with 1000x density), though SABRE is better than
stuff like scramjets. This is especially bad for an SSTO like they are
proposing since you carry the inlets and precoolers and all that all the way
to orbit.

My bet for cheap spaceflight would be a two stage kerosene-oxygen rocket. A
SABRE engine might make a great first stage but I doubt if you would want to
carry it to orbit. I haven't performed much calculations though.

~~~
brc
That was my first thought - Hydrogen has low energy density, even in frozen
form. That is the thing that holds Hydrogen cars back more than anything else
- tiny range for massive (and costly, and complex) fuel tanks. The same would
have to apply to both airplane and rocket designs.

------
nicholassmith
I think the first article I read about Sabre was on HN so it's nice to see it
getting followed up.

The technology sounds like it's progressing, even if parts of it are still
heavily conceptual, and getting a sign off from the ESA is quite a big step
(even if certain space company founders have dissed them recently). The last I
read was they were struggling to find funding, which is on one hand utterly
surprising as if it works properly then it's got the potential to
revolutionise travel and who wouldn't like to say "yeah, I put money in before
they were famous", and on the other isn't a surprise at all as the returns are
probably a decade out.

Still, I wait patiently and optimistically for when Britain is showing
everyone that whilst we were slow off the mark on the space race we aren't out
of it yet.

------
peterstjohn
Here's a documentary that was broadcast on BBC4 a couple of months ago about
Bond and his quixotic journey to get HOTOL/Skylon into the sky:

<http://www.youtube.com/watch?v=vZ_a21fPkYM>

It includes a test-firing of the new heat-exchanger at the end.

~~~
timthorn
One of those truly inspirational stories, where people dedicate their lives
over decades to an idea and see it through. Granted, their aircraft isn't yet
built, but they're well on the way.

------
milliams
Article from the BCC at <http://www.bbc.co.uk/news/science-
environment-20510112>

------
hkhenson
Someone asked on another list for an explanation of the press release. This is
my try.

Hypersonic engines are up against hard physics. The ram air heats so much in
the inlet that it's hard for combustion to add much energy to make it go
faster out the back.

The idea behind the SABRE engines is to cool the ram air before it is
compressed. The heat exchanger to do this is what the press release is all
about. With not much more than a ton of mass, it sucks 400 MW of heat out of
the incoming air, dropping the temperature from 1500 C to -150 C in a few
inches of heat exchanger that looks much like fabric because the tubes are so
tiny.

The engine cycle also uses the temperature difference between the ram air and
the LH2 to run the compressor. It takes close to 2/5th of the energy from
burning hydrogen to liquefy it. The engines recover much of this by running a
helium turbine on the temperature difference between the ram air and the
liquid hydrogen flow to the engines. The turbine powers the compressor stage
that raises the pressure of the -150 C air to rocket chamber pressure.

The design is extremely clever thermodynamics which also avoids most of the
metallurgical problems of high temperature. Fabricating the air to helium heat
exchanger was a very hard task. They have miles of tiny tubing, tens of
thousands of brazed joints and they don't leak!

Using these engines and breathing air, the vehicle reaches 26 km and about a
quarter of the velocity to orbit giving an equivalent exhaust velocity (back
calculate from hydrogen consumption) of 9 km/s. That's twice as good as the
space shuttle main engines. It is expected to go into orbit with 15 tons of
payload out of 300 or 5% even though the rest of the acceleration is on
internal oxygen that only gives 4.5 km/s exhaust velocity.

Leaving out the oxygen and using big propulsion lasers to heat hydrogen
reaction mass, such a vehicle would get 25% of takeoff mass to LEO, reducing
the already low cost by a factor of 5. That's enough to change the economics
of power satellites from being too expensive to consider to a cost
substantially less expensive than any fossil fuel.

But try explaining any of this in a press release.

------
east2west
I wonder how this will impact air travel. It is a real shame that after
Concord retired there is no supersonic jetliner in service, which at least
kept the dream alive even if Concord is expensive and short legged. I believe
no viable program exists right now for supersonic jetliners. The problem, if I
recall correctly from my aerospace professor, is not the jet engine's thrust
but heat generated from friction with air. If this Sabre engine can get the
airplane mostly out of atmosphere cheaply, heat problem can be alleviated. I
don't know how practical my guess is, but if it works, the market potential is
immense.

------
quattrofan
This guy has been at this in various forms for 30 years. Amazing story and for
once not completely fucked up by the British Govt, unlike our aerospace
industry after WWII that was world leading.

------
tzs
> This core piece of technology solves one of the constraints that limit jet
> engines to a top speed of about 2.5 times the speed of sound, which Reaction
> Engines believes it could double

Is that 2.5 times the speed of sound limit just for jets at low altitude? At
high altitude it is certainly not true. Both the SR-71 and MiG 25 did well
over Mach 3.

~~~
schiffern
They mean turbojets ("conventional" jet engines). The SR-71 doesn't use a
conventional jet engine.

[http://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird#Engine...](http://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird#Engines)

> _A unique hybrid, the engine can be thought of as a turbojet inside a
> ramjet. At lower speeds, the turbojet provided most of the compression and
> most of the energy from fuel combustion. At higher speeds, the turbojet
> largely ceased to provide thrust; instead, air was compressed by the shock
> cones and fuel burned in the afterburner._

------
tocomment
Does anyone have guesses on how the heat exchanger might work to prevent
frost?

Perhaps ultrasound?

~~~
tocomment
How about dividing the heat exchanger into two sections? One section cools the
air while the other section defrosts, and then alternate.

~~~
marshray
That was my first guess too. With that many pipes, they could have many
sections which migrate the frosty sections down into the engine in waves.

------
Killah911
Sounds like quite a disruptive innovation in the aerospace industry. Always
wondered how much it cost to get innovations like this off the ground. $400m
funding round sounds pretty serious...

~~~
ovi256
That's the blind, the bet required to play, in aerospace, it's not a lot of
money at all by their standards.

~~~
NickPollard
Or by social media standards. I know it's a rather over-used meme now, but I'm
again reminded of Instagram's $1b buyout vs. this.

This seems like a good blue-sky venture for a scientific philanthropist.
There's a lot that could go wrong, it might not work (though as pointed out
elsewhere, this isn't all theory - they _have_ tested the heat exchanger in
real life on a proper jet engine), but it could be a big win. If only someone
like Gates could put down $400m for a chance of a big pay off later.

------
joonix
Personally I'm always more intrigued by the prospect of getting around the
world quicker. Making the world a smaller place, and more accessible to all,
would do wonders for humanity.

~~~
pyre
You're missing the "cheaper" part that would be required to make it accessible
to all.

------
tsotha
I don't see where this technology "fits". When you're going to orbit, 90% of
the flight takes place outside the atmosphere, so an air-breathing engine
doesn't do much for you.

For commercial sub-orbital hops, they'll have to bring the cost down
considerably to compete with existing air service. Sure, we'd all love to be
able to go from NYC to Frankfurt in an hour. But how many people will pay ten
thousand dollars for the privilege?

~~~
westicle
Given that people already spend multiples of ten thousand dollars to fly it in
greater comfort at "normal" speeds, I suspect there is already a significant
market.

~~~
tsotha
The numbers are too small to justify a separate design. This is why Concorde
failed.

------
afterburner
I'll maybe believe it when I learn more. That it's an idea on paper only means
it's way too early to tell. I'm also wondering if they are relying on exotic
building materials being developed in the future for this to work, like a
previous expensive but failed US space-plane program.

~~~
timthorn
The critical part (the cooling mechanism) has been fabricated, and validated
in tests.

------
lazyjones
This is great news, but it also makes me a bit sad - because all this
innovation died down in the 80's when everyone lost interest in the space
race. We could be 30 years further down the road already and many of us
probably won't live to see people setting foot on Mars.

~~~
stcredzero
I think many of us will.

------
ColinWright
Another discussion of this has broken out here:

<http://news.ycombinator.com/item?id=4856986>

------
colinshark
"The company has deliberately avoided filing patents on its heat exchanger
technology to avoid details of how it works - particularly the method for
preventing the build-up of frost - becoming public."

Evidence that the main use case for patents - protecting true innovation and
development - does not even need the patent system.

------
sek
I was skeptic about them so far, I would love to be proven wrong here.

------
caycep
I'm sure some of you chuckleheads are going to figure out how to use this to
OC some poor unassuming Ivy Bridge CPU...

