USAF + UK's Reaction Engines for hypersonic/single stage to orbit engine

[Dr Mordrid]

Well, well, well....this is VERY interesting what with the talk about the SR-72 and DARPA's XS-1 reusable hoeizontal launcher projects.

The key technology in Reaction Engine's powerplants is a powerful precooler, which was successfully tested last summer. The tests went so well ESA found no showstoppers and REL got funding from the UK govt.

http://www.reactionengines.co.uk

http://moonandback.com/2014/01/13/u-...ceship-engine/

U.S. Air Force to Evaluate British Firms Spaceship Engine

Technology May Offer Unique Performance and Vehicle Integration Advantages

LONDON, U.K. Reaction Engines Ltd has announced that it has entered into a Cooperative Research and Development Agreement (CRADA) with the Air Force Research Laboratorys Aerospace Systems Directorate (AFRL/RQ).

The CRADA provides a framework to assess the performance, applications and development paths for RELs SABRE air-breathing rocket engine, a new class of aerospace engine designed for low cost, responsive space access and high speed atmospheric flight. This CRADA is the first U.S. government formal relationship with Reaction Engines Ltd and will be used to inform U.S. government stakeholders about the SABRE engines potential for hypersonic vehicle applications.

Alan Bond, Managing Director commented The signing of this agreement with AFRL builds on an extraordinary period for Reaction Engines Ltd which has seen the successful demonstration of SABREs ultra-lightweight high performance heat exchanger technology and a UK Government commitment of £60m ($100m) towards the next phase of development of the SABRE engine.

AFRL/RQ project manager Barry Hellman stated that This CRADA opens the door for joint development and testing to help AFRL understand the SABRE engines technical details, and whether it may offer unique performance and vehicle integration advantages when compared to traditional hypersonic vehicle concepts. We look forward to exploring the engine and its lightweight heat exchangers which have the potential to enable hypersonic air-breathing rocket propulsion.

Reaction Engines has developed ultra-lightweight air heat exchanger technology that can transfer the same amount of heat generated by an electricity power station (450MW) using equipment that weighs less than a standard car and can cool air from 1,000°C (1832°F) to minus 150°C (-238°F) in 1/100th second whilst preventing the formation of ice at sub-zero temperatures.

Combined with unique thermodynamic cycles, Reaction Engines heat exchangers enable a new aerospace engine called SABRE that can fly at Mach 5.5 in the atmosphere (twice as fast as a jet engine) and then subtly transition to a rocket mode of operation allowing spaceflight at up to orbital velocity, or Mach 25 (7.5 kilometres per second). The viability of the SABRE engine has been independently validated by the European Space Agency during a review undertaken at the request of the UK government.

SABRE engine pre-cooler testbed
SABRE engine concept
Skylon SSTO spaceplane


LAPCAT A2 hypersonic transport

http://www.reactionengines.co.uk/mach5cruise.html

[Umfriend]

So the Helium itself is not cooled? It just whisks away all energy?

[Dr Mordrid]

The the staged combustion engines (4 per SABRE) can use either chilled air (ramjet mode) or liquid oxygen (rocket mode) as an oxidizer.

In the air breathing/ramjet mode, the helium is run through the precooler where it chills the incoming air. The now (very) hot helium is first used to run turbomachinery then to superheat liquid hydrogen before its burned. The helium is now cold enough to go back to the precooler.

In the vacuum/rocket mode it operates pretty much like any other liquid hydrogen/liquid oxygen staged combustion rocket.

The advantage of the dual-mode is that it requires MUCH less liquid oxygen on board, the mass savings being used for increased payload and eliminating the need for a second stage.

Alternatively, running an air-breathing only version (Scimitar) gives you a hypersonic transport.

[Evildead666]

Doubt this will ever be commercially used, not for the masses anyway.
It'd probably be a Concorde type thing, and about as popular due to the prices.

Military will eat it up though.

[Jammrock]

The no windows part alone will drive most passengers away from it. I suppose if they could make transparent aluminum strong enough to withstand the pressure that might work.

[cjolley]

Is there someplace in this cycle where heat moves from cold matter toward hot matter? It just makes my brain ache to think about it.
I will have to see one working with my own eyes before I believe it. Though it would be cool. (har)

[Umfriend]

I think the compressed hydrogen, especially when expanded, is very cold so that it can re-cool the helium (while being heated itself of course) which can then in turn cool the (incoming) oxygen. Makes sense to me. If I'd thought it was special I'd have patented it 23 years ago.... ;-)

[Evildead666]

Umfriend has it I think.

[Evildead666]

The no windows part alone will drive most passengers away from it. I suppose if they could make transparent aluminum strong enough to withstand the pressure that might work.

You start worrying when the Pilots are placed in a safety box in the middle of the plane, surrounded by the passengers.

[cjolley]

On the other hand, the air coming in is going to be heated by friction and probably has a higher heat carrying capacity than H2.
I mean there's only so much heat the H2 could absorb from a larger mass of heated air.
And it would be impossible (I think it's what I'm asking) to get the air cooler than the H2.

[Umfriend]

Sure, but the H2 will be like -250C or so (after expansion) and you'll only need twice the mol (that's the Dutch word, unsure about the English name for Avagod's number of atoms as SI-unit) of air to H2 because, well, it needs to react with each other in a certain ratio.

I think the energy needed to cool/warm O2/H2 is about the same per atom*. Course, you need twice the H2 but still then, given that the (very thin) air will be sub-zero prior to intake, I can see -120C as feasible.

* Long time ago. Atomweights are 1.0079 and 15.999. Energy per 1K for 1kg is 14,304 and 920. Should use " mol" but here I guess atomweights * energy.(K.kg)^-1 is good enough.

[Dr Mordrid]

Mol is the correct term here as well.

As to the precoolers thermal capacity, try wrapping your head around 400 megawatts while massing only 1.25 tonnes.

In air breathing mode the air is nearly liquified, then it and LH2 are burned in a preburner (normal for staged combustion rockets). The combustion products with more LH2 and air go to the the 4 thrust chambers.

At first glance one might presume that the 80% of air that is nitrogen would be a problem, but it isn't. Once superheated by the LH2/O2 burn in the thrust chamber it becomes extra reaction mass (see air augmented rocket), significantly increasing the engines thrust.

[Umfriend]

That does not answer where/how/to what the precooler dissipates the heat.

[cjolley]

See? And the Nitrogen makes things worse heat-wise because only 20% of the air being cooled is O2.
And supposedly the thing is cooling the air to "cryogenic" temps.

BRIAN!!!!!
We need engineering help here.

[Dr Mordrid]

That does not answer where/how/to what the precooler dissipates the heat.

The incoming hot air heats the liquid helium and is chilled. The now hot helium eventially goes through a heat exchanger to pre-heat the LH2 fuel. Now cold again, the helium goes back to the precooler to chill more air.

ESA and the UK have validated the cycle, and the precooler.