
UK government invests in Sabre air-breathing rocket engine - andydd
http://www.bbc.co.uk/news/science-environment-23332592
======
3327
The Brits are good engineers, and, compared to American juggernaut companies,
specially in the defense and aerospace area, they manage to make innovation
with very little.

The US military spent millions all through the 1960's upto the late 1980's for
a successful VTOL aircraft. Along came the brits with fractions of the budget
with a great product the Harrier GR-1.

There are some great arguments here, specially the savings in weight from
Oxygen by pja.

But I want to ask something different. Even if there is a slight chance for
this idea to succeed shouldn't we/they invest in it anyway? Making
breakthroughs in jet engine design takes years and extraordinary amount of
effort and money. If the government doesn't take the risk, long term
innovation would be very difficult. Plus even if it doesn't reach its intended
goals many side technologies are generated even from a failed undertaking...

~~~
JonnieCache
_> If the government doesn't take the risk, long term innovation would be very
difficult._

What I'm wondering is, if the taxpayers have to take all the risk and spend
all the R&D money out of our own pockets, why don't we get to keep all the
profits as well? I thought innovation was the role of heroic figures who eat
risk for breakfast? I thought the massive, economy-distorting pay packages
were justified by all that risk?

EDIT: obviously a lot more money is needed for marketing, manufacturing etc.
But as I understand it the IP from these projects is basically given as a gift
to favoured arms manufacturers when it's ready to become a product? Please
correct me.

~~~
arethuza
The article says:

"the government's investment represents about 25% of the total"

Personally I am quite delighted to see my UK tax money going to back this
project. Compared to the amounts we spend on much sillier projects it is a
rounding error.

[e.g. My home city of Edinburgh is spending £1 _billion_ on a rather short
length of trams and the UK is spending ~£7 billion on two aircraft carriers
when we can only afford to run one!]

~~~
JonnieCache
In this case that seems pretty fair. Although if it's only 25% and it's such a
great project I wonder could our bounteous financial sector not cover it?

Are the trams really still not finished? Blimey. My commiserations.

~~~
arethuza
"Are the trams really still not finished?"

About a year from them actually running properly for passengers :-|

------
speeder
Whoa, this is really awesome!

For those that don't know, airbreathing engines are MUCH MORE efficient than
conventional rocket engines.

Not only in terms of weight saved from not having to lug around too much O2,
but also because of the way it works inherently.

I decided to make a space game once, with real world stuff on it, and settled
for the Triton engine for my game spaceship, I did lots of research about
rocket engines, and I was very sad when I compared them to airplane engines
and it was clear how better they were, and yet useless in space.

But I never had this idea of mixing both... It sounds so awesome that I cannot
describe it.

Also it allow some sci-fi stuff that is frequent but so far very broken (that
is small fighter spaceship planes hybrids that can enter and leave atmosphere
at will, that for now were usually handwaved by the author to explain that it
has some weird super efficient rocket engine... with this tech that sort of
stuff is less improbable)

~~~
benl
Are they really more efficient, for real world uses?

The way I understand it, the argument goes something like this. To reach orbit
you need to accelerate to very high speeds (Mach 25). To avoid crazy drag
losses you therefore want to get out of the atmosphere as quickly as possible.
So being able to use oxygen from the air on your way up is a marginal gain at
best, and almost certainly not worth the extra complexity.

~~~
olex
The main advantage of the Sabre concept is not only using outboard air as
substitute for onboard oxidizer, but also as reaction mass. This allows to
accelerate to over Mach 5 while still flying in airbreathing mode, using a
fraction of the amount of fuel that would be required to reach the same speed
on pure rocket power, and no onboard oxidizer. Once that speed is reached, the
air becomes too thin for the air-breathing mode to continue functioning, and
the engines switch to rocket mode, burning onboard oxidizer instead of air;
but because the ship is nearly out of the atmosphere at this point, it doesn't
take much to finish accelerating to orbital speed. Think of it basically as
replacing the whole first stage of a conventional rocket with some jet engines
and a sip of fuel for them.

------
lifeisstillgood
This made my day however:

    
    
      has passed an independent audit from European Space 
      Agency experts, and Mr Osborne himself has inspected the 
      test rig on the Culham science park in Oxfordshire.
    

The ESA has verified the engine, but thank goodness, George Osbourne double
checked it all, just in case those rocket scientists missed micro-fluctuations
in heat transfer gradients. I mean they were probably all French anyway.

George Osbourne (UK CFO/Treasury Secretary) is getting a lot of political
flack, and having his name associated with UK home grown and based innovative
technology is clearly something his press office wanted the BBC to know. Who
were too lazy to cut the sentence.

~~~
voicereason
You clearly have something against Osborne.

The UK government are investing the money. Osborne is the Chancellor of the
Exchequer, why is it strange that he would be mentioned in the article as
having a look at it?

He's only getting political flak from socialists and welfare claimants really
- no surprise there.

~~~
JonnieCache
And those well known socialists, the IMF:
[http://www.guardian.co.uk/politics/2013/apr/18/george-
osborn...](http://www.guardian.co.uk/politics/2013/apr/18/george-osborne-imf-
austerity)

------
timw6n
A couple of months ago there was an excellent BBC4 documentary about Alan Bond
and Reaction Engines called The Three Rocketeers[1], which I believe has been
re-posted on the internet.

[http://www.bbc.co.uk/programmes/b01mqv45](http://www.bbc.co.uk/programmes/b01mqv45)

~~~
Element_
It was an excellent documentary:
[http://www.youtube.com/watch?v=vZ_a21fPkYM](http://www.youtube.com/watch?v=vZ_a21fPkYM)

------
acd
Sabre Air will eventually revolutionize internet communication so that it is
possible to get internet access cheaply anywhere on earth.

Commstellation a Canadian company are planning 72 micro satellites that will
provide backbone capacity for cellphone towers. Latency will be in the 40 ms
range. [http://www.commstellation.com/](http://www.commstellation.com/)

Currently smartphones become dumb phones as soon as you leave your country on
vacation, in the future we will be able to connect to internet anywhere
cheaply.

------
eksith
This is a dubious investment IMO.

Rockets that have shrouds have been thrown about for a long time, but they
have one fundamental weakness. The shroud only works while in the atmosphere.
After that, it's dead weight (since no significant aerodynamic forces come
into play further up).

It's not quite the same as the SR-71 Blackbird engine which is a turbojet
engine that morphs mid-flight into a ramjet. That's quite a spectacular piece
of engineering especially since this was before the advent of computer-aided
modeling. But the SR-71 was still very much an air breathing engine. The outer
engine casing was still an essential part of its function.

Don't get me wrong; I wish these guys success and I hope my assessment is
incorrect, but I just don't see how added weight to win over gravity lower in
the atmosphere would help in the upper atmosphere and in space.

~~~
NickPollard
I don't know the maths involved, but the idea presumably is that they save
more weight not carrying (as much) oxygen than they lose by adding the rest of
the engine. By being able to draw oxygen from the air whilst in the
atmosphere, they only need to store a smaller amount of oxygen for when they
hit space. This is the main saving I believe.

~~~
pja
Indeed. O2 is much heavier than H2 so if you can scavenge the O2 out of the
atmosphere on the way up then the amount you need to carry for the final burn
in space is much smaller & the weight savings are huge.

Consider that the Space Shuttle external fuel tank contained 650,000kg of O2
and only 100,000 kg of H2. Save 10% of your O2 needs and suddenly you've got
60,000 kg to play with. The Shuttle payload was only about 25,000 kg.

------
parley
I seem to remember Elon Musk getting a question about SABRE at a post-talk Q&A
a while back (probably in the UK, perhaps an inauguration ceremony of some
institution), but now I can't find it. He was skeptical and had some
constructive things to say, but I'm not a physicist so unfortunately I can't
remember the specifics. If anyone else finds it, kindly reply with a link!

EDIT: Found the video, but haven't yet found the specific time of the
question. My connection is a bit slow, so jumping around in the stream isn't
going so well.
[http://www.oxfordmartin.ox.ac.uk/videos/view/211](http://www.oxfordmartin.ox.ac.uk/videos/view/211)

EDIT 2: Found it. Elon's reply is at 48:55.

~~~
arethuza
Maybe he doesn't like it because it won't work on Mars? :-)

------
tobiasu
How and where does the nitrogen boiler(?) get its energy too cool helium to
-170C at a constant rate? Is it effective to chill what must be ginormous
amounts of air to -150C? It's all nice that the heat exchanger works, but
where does that heat go?

There's a large discrepancy between the inlet air temperature (1000C vs 20C)
in the article.

Somehow my sense for violation of the laws of thermodynamics is tingling.

~~~
arethuza
They have details on their web site:

[http://www.reactionengines.co.uk/sabre_howworks.html](http://www.reactionengines.co.uk/sabre_howworks.html)

My reading of their explanation is that in a full system they would "pre-burn"
some of the hydrogen and oxygen also used to power the main rocket motor to
power the cooling of the helium that then cools the intake air.

[NB I have no idea whether that would actually work or not - just trying to
interpret what their own explanation is!]

~~~
tobiasu
Thanks for the link, this clears up a lot:
[http://www.reactionengines.co.uk/images/sabre/sabre_cycle_10...](http://www.reactionengines.co.uk/images/sabre/sabre_cycle_1024.jpg)

There is no nitrogen in the system (not as consumable, anyway). Shoddy BBC
reporting, as usual.

The heat exchangers use chilled hydrogen fuel they have to take up anyway,
before it is burned in the rocket motor.

That makes a ton more sense.

~~~
arethuza
To be fair to the BBC, what they describe is the test setup that has actually
run, not the design of the full engine - which they haven't built yet.

------
jotm
Man, I really hope this engine works - they won't get a second chance if the
prototype fails (which is a shame, since the concept is solid)...

And that prototype plane/spaceship just looks cool as hell...

------
jpeg_hero
The british are cute.

that test rig looked like something the North Koreans would put together.

this is no where near being a "real program"

------
venomsnake
I am a bit skeptical of any technology that uses helium. We just don't have
viable ways to obtain reliably enough of the stuff reliably.

~~~
arethuza
Well, there is an expensive plant in France that will be manufacturing helium
from raw materials ;-)

[http://www.iter.org/](http://www.iter.org/)

~~~
venomsnake
Nuclear fusion has always been 10 years away. Lets hope that they will succeed
this time.

~~~
shabble
The fusion itself is (afaik) essentially a solved problem. The trick is
extracting net energy from it, since you use a lot in generating the plasma,
massive magnetic fields to keep it contained, etc.

But if you just cared about the byproducts, I think that's a much easier
problem.

Probably still 10 years though :)

