new jet engine?

[blink138 (Pat)]

this sounds very interesting
http://www.sciencealert.com/this-pla...within-4-hours
the cooling system seems to be the breakthrough here
pat

[pluto (Hugh)]

Really exciting, I've been following this for a while. They recently got some government funding too I think.
And much more exciting than quick Jet setting is that it should be a reusable single stage to orbit space plane

[AndrewJ]

Be interesting to see how much power it uses/loses in the process itself.
ie in thermodynamics, you get nothing for free.
My final year project at uni involved looking at the heat transfer rates for various tube/fin/coolant arrangements vs the power required to achieve it.
To get higher heat transfer always required power to be put in from an external source, be that a bigger fan or a more powerful coolant pump.
Interesting research tho.
Andrew

[pluto (Hugh)]

The Wikipedia page for the Sabre engine has some good info on the precooler:
http://en.wikipedia.org/wiki/SABRE_(rocket_engine)

[lazjen (Chris)]

Very interesting read, thanks for the posts.

[multiweb (Marc)]

Sounds very cool going up to low orbit. How about re-entry? Do they have some kind of heat shield on the vehicle?

[pluto (Hugh)]

Originally Posted by multiweb

Do they have some kind of heat shield on the vehicle?

I think that because it's really big and relatively light during reentry it doesn't experience the kind of temperatures that the shuttle/capsules do. I suppose they'll still need something to dissipate heat but it probably doesn't need to be ablative.

EDIT: just checked Wikipedia
Referring to the STS TPS -

The Skylon design does not require such a system, instead opting for using a far thinner yet durable reinforced ceramic skin. However, due to turbulent flow around the wings during re-entry, some parts of Skylon would need to be actively cooled.

[PeterEde (Peter)]

Noise? What kind of dB we looking at? The concorde was banned from many cities due to noise.

[Wavytone]

Haha...

It's a scam designed to fleece gullible investors of their cash.
Does the name Alan Bond ring any bells ?

Firstly the claims are simply impossible, they're breaking a few laws of physics, secondly noise... As Concorde demonstrated frequent sonic booms from passenger aircraft are not tolerable for a host of reasons - it will never receive permission from the various aviation authorities to overfly populated areas at supersonic speeds. Even over the ocean it isn't economic - factor in the times it must decelerate to subsonic speeds it ceases to be worthwhile.

There were a number of studies done in the us regarding the shock from supersonic passenger planes and it's insoluble - there really is a good reason the likes of Boeing, McDD and Lockheed never built one.

[pluto (Hugh)]

Originally Posted by Wavytone

Firstly the claims are simply impossible, they're breaking a few laws of physics, secondly noise... As Concorde demonstrated frequent sonic booms from passenger aircraft are not tolerable for a host of reasons.

Which laws of physics? perhaps you should tell the ESA, among others, as they think it's a good idea:
http://www.esa.int/Our_Activities/Sp...ine_investment
https://www.gov.uk/government/case-s...h-technologies
http://www.theregister.co.uk/2011/05...on_esa_report/
http://en.wikipedia.org/wiki/Skylon_...ne_development

I agree with the noise issues though the passenger aircraft option is certainly secondary to the Skylon's use as a SSTO spacecraft.

[AndrewJ]

Gday Hugh

Which laws of physics?

The laws of thermodynamics associated with conservation of entropy and enthalpy??
The rate at which you can transfer energy from air to something else and how much energy will be required to do it is not simple
Ie

cools down the air entering the engineer system by more than 1,000 degrees Celsius in .01 seconds. That corresponds to an unheard-of cooling rate of 400 megawatts,

yet later it mentions

Crucial to the engine's performance, however, is a compact pre-cooler heat-exchanger that can take an incoming airstream from over 1,000C to -150C in less than 1/100th of a second.

Soooo, 1150 deg C drop. Not sure i believe that yet.
There is no free lunch in thermodynamics, so where does the 400+MW come from?
ie How much air is really getting cooled, and where does the energy come from to cool it??? You might be able to cool an air layer a few atoms thick at that rate in a lab test, but maybe not the full intake volume for a jet engine at mach 4. ( And their diags indicate the whole inlet air volume is getting cooled???? )
Again, interesting research, but ill believe it when it runs.

Andrew

[pluto (Hugh)]

Hi Andrew,
They have an explanation of the engine design here:
http://www.reactionengines.co.uk/sabre_howworks.html
I'm sure you'll understand it better than I do

I can't find many details but I believe they tested a full sized precooler in 2012 and it was successful in cooling the incoming air from 1000c to -150c. However I don't know how they heated the air and under what conditions it entered the precooler, and I'm not sure how long the test ran for. This was the testing that was overseen by the ESA propulsion experts and its success was required to achieve the next round of government funding, which they got.

The next milestone is for them to build a complete sub-scale engine with precooler and to run it in simulated flight conditions.

I certainly understand your skepticism though as it's a pretty difficult machine they're trying to build, and they're certainly not the first to claim they've invented the next-big-thing

[AndrewJ]

Gday Hugh
Having an explanation, and being able to do it in real life at full scale are 2 different things.
Eg Fusion reactors are well understood "in theory", as was the nuclear car on the gold coast back in Johs day
http://www.stephenhorvath.com.au/
I just cant get my mind around the reality of cooling the amount of air a full sized engine would need when going at mach 4 by 1100degC in 0.01 seconds.
My calculator runs out of digits.

Andrew