
Reaction Engines Reveals Secret of Sabre Frost Control Technology - curtis
http://aviationweek.com/space/reaction-engines-reveals-secret-sabre-frost-control-technology
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Mithaldu
Can someone explain for a layman what this cooling technology is useful and
necessary for?

Edit: Thanks for the excellent explanations. Upvotes all around. :)

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curtis
The guys at Reaction Engines are trying to build a jet engine that will
operate at very high speeds. In order to make this work the incoming
supersonic air has to be slowed to subsonic speeds and compressed. This has
the unfortunate effect of also making the air very hot and much less dense
than it might otherwise be. This limits the effectiveness of the engine. This
cooling technology can be used to cool the hot air before injecting fuel for
combustion. This can increase the maximum speed at which the jet engine can
operate.

The reason Reaction Engines is working on this type of jet engine is because
they want to use it for an airbreathing single-stage-to-orbit re-usable
spaceplane. (Technically, the Reaction Engines design is a hybrid that
switches to a pure rocket mode at higher speeds.)

Some further reading:

Precooled jet engine:
[https://en.wikipedia.org/wiki/Precooled_jet_engine](https://en.wikipedia.org/wiki/Precooled_jet_engine)

SABRE (rocket engine):
[https://en.wikipedia.org/wiki/SABRE_%28rocket_engine%29](https://en.wikipedia.org/wiki/SABRE_%28rocket_engine%29)

Single-stage-to-orbit: Airbreathing SSTO:
[https://en.wikipedia.org/wiki/Single-stage-to-
orbit#Airbreat...](https://en.wikipedia.org/wiki/Single-stage-to-
orbit#Airbreathing_SSTO)

Skylon (spacecraft):
[https://en.wikipedia.org/wiki/Skylon_%28spacecraft%29](https://en.wikipedia.org/wiki/Skylon_%28spacecraft%29)

~~~
twic
Perhaps not all of them are 'guys'. Can we stick to the gender-neutral
'boffins' please?

~~~
colordrops
'guys' is gender neutral in the US. 'boffins' is not used at all in the US,
and sounds vaguely offensive, even if its meaning is not.

~~~
programmernews3
Well that is bizarre. When did guys become gender neutral in the US? How did
that happen?

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ohsnap
Started exactly in June 1985. In the film Goonies, Sloth called out 'hey you
guys' to a gender mixed group. Never been the same.

[https://www.youtube.com/watch?v=OmTNWVh2gSw](https://www.youtube.com/watch?v=OmTNWVh2gSw)

~~~
programmernews3
Well that explains it, thanks :(

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anentropic
"The system chills incoming air from more than 1,000C to minus 150C in less
than 1/100th of a second"

sounds impressive!

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CarVac
This is really incredibly awesome.

The SABRE is turning out to be "Countercurrent exchange: the engine".

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dvdt
Someone please correct me if I'm wrong, but it sounds like the secret is to
use countercurrent exchange to rapidly cool incoming air? Incidentally,
countercurrent exchange is the same principle used in the kidneys to
concentrate waste products into urine.

[https://en.wikipedia.org/wiki/Countercurrent_exchange](https://en.wikipedia.org/wiki/Countercurrent_exchange)

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Theodores
This project is a bit like the British 'Bloodhound' land speed record attempt
in that there is a bit of 'Duke Nukem' about it, i.e. it is never going to
happen! Very 'British' though, with the usual cause for failure, e.g. short
term return on investment demands of the city, the uselessness of the
government for backing 'British genius' and so on.

Anyone not sceptical is advised to watch the BBC documentary 'The Three
Rocketeers':

[https://www.youtube.com/watch?v=vZ_a21fPkYM](https://www.youtube.com/watch?v=vZ_a21fPkYM)

These guys have been begging for funding and making the same 'design studies'
for decades, the fact that British Aerospace 'BAE SYSTEMS' have disowned the
project is quite telling, it is not anywhere near being tangible and it never
will be. The only lesson to be learned here is how not to run your start up!!!

~~~
codewithcheese
Except the UK Space Agency awarded them a £60 million investment in 2013 after
a successful precooler test conducted with the European Space Agency.

[http://www.engineering.com/DesignerEdge/DesignerEdgeArticles...](http://www.engineering.com/DesignerEdge/DesignerEdgeArticles/ArticleID/6023/UK-
Government-Invests-60M-in-Spaceplane-Engine.aspx)

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pcrh
I'm not an engineer, but this [0] appears to be at least one patent related to
technology used to cool the air and economize on methanol. Perhaps someone can
interpret it for a more general audience?

[0]
[https://www.google.com/patents/US20150101334](https://www.google.com/patents/US20150101334)

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jakeogh
I don't get it. They are injecting methanol on the outside of the precooler
tubes right? What causes it to move opposite to the airflow? Capillary/wetting
action?

~~~
CarVac
The dehumidification is done before the precooler, I'd expect.

They seem to inject it at the end, collect it somehow, then inject it upstream
of the first injection location, then collect it again, then inject again
upstream of that...

No clue how they perform this collection action, though.

~~~
draggnar
No, it seems like the mix moves against the airflow, so they'll inject it and
collect it upstream. He refers to a trick from the chemical industry. It seems
like with the massive temperature difference, the mix will move (expand?) to
the warmer part, and the force of this is stronger than the airflow so it
moves upstream.

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curiousjorge
I think this will be the single biggest revolution since aviation history. It
would change the way we travel, send things up to space. Of course, military
consequences will be interesting as well. I wonder if US military already has
something like this in the works. I'd hate it to see it fall into the wrong
type of people.

Very inspiring stuff.

[https://www.youtube.com/watch?v=vZ_a21fPkYM](https://www.youtube.com/watch?v=vZ_a21fPkYM)

~~~
adventured
Given China, Russia, US all steal from each other when it comes to military-
aerospace technology (making no statement about who steals more mind you), it
would be entirely irrelevant if it fell into the wrong hands.

If China gets it first, the US will steal it from them. If the US gets it
first, China will steal it from them.

Of the countries that could actually put it to use, they're going to get it no
matter what. The other countries are of no concern, they're all at least 30
years behind and will perpetually remain that way.

