• Hi Guest! Forum rules have been updated. All users please read here.

Skylon Spaceplane

steelpillow

So many projects, so little time...
Senior Member
Joined
Jun 25, 2014
Messages
556
Reaction score
53
Website
www.steelpillow.com
TomS said:
sferrin said:
Imagine the cooler required to take the exhaust from say, an F414 in afterburner, and turn it into liquid. :eek:
Not quite that cold -- it's about 40C above the liquefaction point. But yeah, it's pretty heroic. Keeping it from icing up seems like the worst part. Ice blocking channel in the precooler could cause serious problems, so they have to dry the air as well as chill it.
As I understand it, the oxygen in the air will liquidise, but not the nitrogen. What comes out the back is a kind of gassy slush. Jet exhaust would have high carbon dioxide and water content and that would solidify into both ordinary and "dry" ice well above these temperatures. Without knowing the detailed test regime, it probably needs a heat exchanger to keep combustion gases out of the precooler. Either that, or use an incandescent electric heater.

My main concern with bean-burritos, as suggested above, is that the very thin tubes of the precooler might curl up in disgust.
 

TomS

CLEARANCE: Top Secret
Senior Member
Joined
Apr 16, 2008
Messages
3,208
Reaction score
125
No. Oxygen liquifies at -183C, so again, SABRE doesn't get quite cold enough. I think people are confusing this with earlier liquid air cycle engines (LACE). SABRE specifically is trying to avoid the problems of dealing with liquifying the airflow, so it "only" chills down to -150C.
 

sferrin

CLEARANCE: Above Top Secret
Senior Member
Joined
Jun 3, 2011
Messages
11,944
Reaction score
285
Guilty. I thought it was a LACE engine. :-[ I thought the plan was to liquefy air on the way up to use at high altitude / in space where there isn't any.
 

AndrewN

By day, a mild mannered teacher of computing...
Joined
Sep 16, 2012
Messages
18
Reaction score
0
Reaction Engines does have a "secret sauce" method of eliminating the blocking of the pre-cooler from frozen moisture and other stuff. They won't talks about the details but it is supposed to involve the injection of Methanol into the airstream around the cooler.
 

Zootycoon

CLEARANCE: Confidential
Joined
May 27, 2008
Messages
163
Reaction score
101
-150C is the pre-cooler outlet temperature for the Sabre 3 thermodynamic cycle. Reaction Engines latest Sabre 4 thermodynamic cycle doesn't necessarily need operate this low. In fact Richard Varvil has even hinted that the 4 can run on LCH4 (-161C) in place of the LH2 which has the pre-cooler deliveries air at maybe -100C or higher. The real advantage of LCH4 is the energy density which is just over twice that of LH2.This means the airframe is smaller I.e lighter, for the same payload or range.
 

steelpillow

So many projects, so little time...
Senior Member
Joined
Jun 25, 2014
Messages
556
Reaction score
53
Website
www.steelpillow.com
TomS said:
No. Oxygen liquifies at -183C, so again, SABRE doesn't get quite cold enough. I think people are confusing this with earlier liquid air cycle engines (LACE). SABRE specifically is trying to avoid the problems of dealing with liquifying the airflow, so it "only" chills down to -150C.
The phrase "cooled to the point of liquefaction" is also used to describe this stage of the engine cycle. It means something fairly specific to a physicist, denoting the temperature at which the fluid liquidises. During liquefaction, the temperature does not change but the fluid gets rid of its latent heat of evaporation. The temperature throughout this period of condensation remains at " the point of liquefaction". If as you say "SABRE doesn't get quite cold enough" then this is not in fact the point of liquefaction and somebody is misleading us somewhere.
Exact temperatures are only a rough guide, as the conditions at the compressor face are far from standard atmospheric pressure and a nice, sealed condensation vessel.
The relevant detail seems to have vanished from the RE web site, so we shall just have to wait and see what the truth really is.
 

SteveO

CLEARANCE: Secret
Joined
Jun 24, 2007
Messages
363
Reaction score
1
Not much on the Reaction Engines website about Skylon or space exploration anymore :(

You can hardly see Skylon against the black of space and behind(!!) the header on the vehicles page! Oh well, at least work on the Sabre engine is progressing. SpaceX will have to do in the meantime :D

Found this here though - https://www.reactionengines.co.uk/careers/life-at-rel/
 

Attachments

FighterJock

CLEARANCE: Top Secret
Joined
Oct 29, 2007
Messages
1,029
Reaction score
25
SteveO said:
Not much on the Reaction Engines website about Skylon or space exploration anymore :(

You can hardly see Skylon against the black of space and behind(!!) the header on the vehicles page! Oh well, at least work on the Sabre engine is progressing. SpaceX will have to do in the meantime :D

Found this here though - https://www.reactionengines.co.uk/careers/life-at-rel/
Interesting find SteveO, another design variant of Skylon that Reaction Engines are investigating, or just a design exercise?
 

Moose

CLEARANCE: Top Secret
Senior Member
Joined
Jul 4, 2010
Messages
1,023
Reaction score
37
Nice find, SteveO.

Wonder if that's a further exploration of the A2/SCIMITAR concepts rather than Skylon/SABRE.
 

SteveO

CLEARANCE: Secret
Joined
Jun 24, 2007
Messages
363
Reaction score
1
Better pic from - https://twitter.com/ReactionEngines/status/842700031132078080

I'm guessing it's a hypersonic airliner concept. V-Tail, winglets and area ruling. The embedded engines are a big change from previous configurations and the latest SABRE concepts are much more slim line than those proposed for Skylon.
 

Attachments

FighterJock

CLEARANCE: Top Secret
Joined
Oct 29, 2007
Messages
1,029
Reaction score
25
SteveO said:
More from Twitter - https://twitter.com/ReactionEngines/status/784680163757944832 and https://twitter.com/ReactionEngines/status/784473384327446528
That third design reminds me of the Lockheed Skunk Works Mach 3 D-21.
 

harrier

BAe P.1216 book: harrier.org.uk/P1216.htm
Senior Member
Joined
Dec 21, 2006
Messages
1,011
Reaction score
47
I saw on Twitter that Alan Bond retired from REL today. I wonder if that will change its focus?
 

FighterJock

CLEARANCE: Top Secret
Joined
Oct 29, 2007
Messages
1,029
Reaction score
25
Harrier said:
I saw on Twitter that Alan Bond retired from REL today. I wonder if that will change its focus?
End of an era, wonder who will take over? Hope Skylon goes from design study to actual flying hardware and does not end up being another HOTOL. That is what I fear about Alan Bond's retirement.
 

steelpillow

So many projects, so little time...
Senior Member
Joined
Jun 25, 2014
Messages
556
Reaction score
53
Website
www.steelpillow.com
I think the NASA study killed Skylon as we know it. If you want to design a spaceplane then you have to understand rocket exhaust plumes. Every practical powered spacecraft has had the engine exhausts at the back, and for very good reason. Skylon tried to be too clever and moved them too far forward. HOTOL was actually a more practical design in this respect, though in reality it was never more than a poster child for SABRE development. Fortunately, SABRE doesn't need either of them any more.
 

Flyaway

CLEARANCE: Top Secret
Joined
Jan 21, 2015
Messages
2,235
Reaction score
296
Harrier said:
I saw on Twitter that Alan Bond retired from REL today. I wonder if that will change its focus?
Here’s his official statement on the REL website.

https://www.reactionengines.co.uk/alan-bond-retires-reaction-engines/
 

FighterJock

CLEARANCE: Top Secret
Joined
Oct 29, 2007
Messages
1,029
Reaction score
25
Flyaway said:
Harrier said:
I saw on Twitter that Alan Bond retired from REL today. I wonder if that will change its focus?
Here’s his official statement on the REL website.

https://www.reactionengines.co.uk/alan-bond-retires-reaction-engines/
Good to see that Alan Bonds replacement has been already chosen, lets hope that REL carry's on with the Sabre engine and then Skylon or whatever design replaces it.
 

fredymac

CLEARANCE: Top Secret
Joined
Dec 14, 2009
Messages
1,448
Reaction score
66
How small can this technology scale down? If you really want people to take notice and attract venture capital, a minimum size/unmanned flight demonstrator would go a long way. The X-43 was very small and the program cost around $250M. Is that kind of financing too much for the UK?
 

AndrewN

By day, a mild mannered teacher of computing...
Joined
Sep 16, 2012
Messages
18
Reaction score
0
You're right, a flying demonstrator would be advantagous but the money would be a challenge in the UK. Certainly the UK government wouldn't put up the full amount, the government of the day has it's hands full with Brexit at the moment and I don't think something like Skylon would fit with the opposition's mind set (I could be wrong there, I have been before). However it's paid for though, I think RE has to have a running engine first and this is what they are concentrating on at the moment. Once they can demonstrate that they can produce the thrust needed to get an aircraft off the ground in the first place then a demonstrator aircraft would be the next logical place to go to and more likely to attract the funding required.
 

steelpillow

So many projects, so little time...
Senior Member
Joined
Jun 25, 2014
Messages
556
Reaction score
53
Website
www.steelpillow.com
DARPA have already picked up the next expense, building a high-temperature test facility to simulate the compression-heated air hitting the precooler.

If the US don't follow it up with a small-scale drone testbed, nobody else will.
 

AndrewN

By day, a mild mannered teacher of computing...
Joined
Sep 16, 2012
Messages
18
Reaction score
0
Yes, they have and most welcome it is too. It's interesting that both the Americans and the Europeans have seen promise enough to put money up to investigate the capability of the SABRE concept.
One point about the Skylon engine location, a major problem with HOTOL that they could never sort out was the centre of gravity/centre of pressure mismatch caused by all the mass of the propulsion at the rear of the vehicle. Skylon's mid postion location of the engines was an attempt to solve this problem. Of course this brings own issues, such as exhaust impingement on the rear fuselage.
 

steelpillow

So many projects, so little time...
Senior Member
Joined
Jun 25, 2014
Messages
556
Reaction score
53
Website
www.steelpillow.com
AndrewN said:
One point about the Skylon engine location, a major problem with HOTOL that they could never sort out was the centre of gravity/centre of pressure mismatch caused by all the mass of the propulsion at the rear of the vehicle. Skylon's mid postion location of the engines was an attempt to solve this problem. Of course this brings own issues, such as exhaust impingement on the rear fuselage.
Posted earlier but seemingly taken down, here is a lower-res version of the SABRE system diagram:



Note how most of the gubbins is miles from the combustion chamber.
The obvious thing to do is what Frank Halford did to the Whittle jet when he turned it into the de Havilland Goblin - he straightened out all the kinks in the pipework and designed the thing around the airflow. It made for a longer engine, but a far more practical one. Do the same to the SABRE and you end up with a forward intake-cooler-turbine section, a pipe full of compressed stuff surrounded by widgetry, and a rear combustion chamber. This long, lean SABRE would improve the balance of HOTOL by moving the intake section forward, while improving SKYLON by also moving the rocket chamber aft. A halfway design, having just a stub rear fuselage, might just cut it.
 

Rhinocrates

CLEARANCE: Confidential
Joined
Sep 26, 2006
Messages
180
Reaction score
11
This has been covered upthread, but giving it a bump.

BAE Systems has invested in Reaction Engines and has developed concept of a hypersonic strike aircraft that uses SABRE. The notable thing about the design is that it separates the intake and rocket components and bypasses the problem of the hot plume damaging the sides of the vehicle. It is an aircraft and not a spaceplane - but Reaction Engines is called Reaction Engines and not Skylon Corp because they acknowledge that they don't have the capital to develop a complete spaceplane, but have a propulsion concept that is applicable to a spaceplane among other things. The AFRL also has an interest in the engine for the first stage of a 2STO system.

https://www.digitaltrends.com/cool-tech/bae-funds-sabre-engine-prototype/

https://www.space.com/32115-skylon-space-plane-engines-air-force-vehicle.html?cmpid=514648

http://nextbigfuture.com/2016/07/bae-systems-reveals-vision-of-unmanned.html

https://www.youtube.com/watch?v=XVBHs-aS9WU
 

Attachments

FighterJock

CLEARANCE: Top Secret
Joined
Oct 29, 2007
Messages
1,029
Reaction score
25
Rhinocrates said:
This has been covered upthread, but giving it a bump.

BAE Systems has invested in Reaction Engines and has developed concept of a hypersonic strike aircraft that uses SABRE. The notable thing about the design is that it separates the intake and rocket components and bypasses the problem of the hot plume damaging the sides of the vehicle. It is an aircraft and not a spaceplane - but Reaction Engines is called Reaction Engines and not Skylon Corp because they acknowledge that they don't have the capital to develop a complete spaceplane, but have a propulsion concept that is applicable to a spaceplane among other things. The AFRL also has an interest in the engine for the first stage of a 2STO system.

https://www.digitaltrends.com/cool-tech/bae-funds-sabre-engine-prototype/

https://www.space.com/32115-skylon-space-plane-engines-air-force-vehicle.html?cmpid=514648

http://nextbigfuture.com/2016/07/bae-systems-reveals-vision-of-unmanned.html

https://www.youtube.com/watch?v=XVBHs-aS9WU
First time that I have seen this design, looks like a similar concept to the Skunk Works SR-72.
 

Flyaway

CLEARANCE: Top Secret
Joined
Jan 21, 2015
Messages
2,235
Reaction score
296
Via NASA Spaceflight forum.

This month's Spaceflight (ISSN 0038-6340, Vol 59 No. 12 December 2017) mentions the HTX in the 'Briefing Notes' section, ending with
REI says that flight tests could begin within five years with an X-series research vehicle which will integrate airframe, propulsion system and associated systems for a hypersonic vehicle which may satisfy US Air Force requirement for a hemispheric strike system
 

Flyaway

CLEARANCE: Top Secret
Joined
Jan 21, 2015
Messages
2,235
Reaction score
296
Reaction Begins Building U.S. Hypersonic Engine Test Site

A high-temperature airflow test site designed to evaluate a key technology in the Reaction Engines’ hypersonic air-breathing combined cycle Sabre rocket engine is under assembly at Front Range Airport near Watkins, Colorado. Construction of the facility follows the award earlier this year of a U.S. Defense Advanced Research Projects Agency (DARPA) contract to test the engine’s pre-cooler heat exchanger, or HTX. The test work, which is due to start in 2018, will focus on running ...
http://m.aviationweek.com/space/reaction-begins-building-us-hypersonic-engine-test-site
 

Flyaway

CLEARANCE: Top Secret
Joined
Jan 21, 2015
Messages
2,235
Reaction score
296
Reaction Engines Begins Construction of High-Temperature Airflow Test Facility in Colorado

WATKINS, CO – December 18, 2017

Reaction Engines, Inc. has begun construction of a new high-temperature airflow test facility where it plans to validate the performance of its precooler heat exchanger technology, an enabler of its revolutionary SABRETM engine. Located at the Front Range Airport near Watkins, Colorado, the test facility will be capable of exposing the precooler test article (HTX) to high-temperature airflow conditions in excess of 1800°F (1000°C) that are expected during high-speed flights up to Mach 5.

Reaction Engines, Inc. recently received a contract award from the Defense Advanced Research Projects Agency (DARPA) to conduct the HTX tests, which are designed to build upon previous successful testing of the precooler heat exchanger at ambient temperature conditions.

“This new test facility shows our commitment to rapidly prove our precooler technology in the most compelling test campaign possible,” said Dr. Adam Dissel, President of Reaction Engines Inc. “The facility’s ability to deliver controlled temperature profiles over flight-like run durations at significant airflow represents a unique capability that can fill additional testing demand beyond HTX.”

The project is an additional investment by Reaction Engines into ground test facilities. The company is progressing rapidly on the previously announced TF1 engine test facility in the United Kingdom where the first ground-based demonstration of its revolutionary SABRE™ air-breathing rocket engine will take place. The Colorado test facility, named TF2, consists of a test building and a control room located on the east side of the Front Range Airport. The hot air for the testing will be provided by a modified afterburning jet engine configured to produce a wide range of flowrates and temperatures.

“We are tremendously excited that Reaction Engines is locating their new engine test facility here at Front Range Airport and, as the future site of Spaceport Colorado, the linkages between high-speed aviation uses and the commercial space applications for this new technology are a perfect fit,” said Dave Ruppel, Front Range Airport Director. “Reaction Engines has been outstanding to work with and we are looking forward to being a small part of their ongoing success.”

Colorado has a long history as a leader in the U.S. aerospace sector, and provides a supportive and capable location for Reaction Engines’ expanding U.S. activity.

“Colorado is a leading aerospace state known for our innovative businesses that propel our growing aerospace economy,” remarked Jay Lindell, representing the Colorado Office of Economic Development and International Trade. “We are proud to have Reaction Engines in Colorado at the Front Range Airport and look forward to supporting their test operations that will lead to future cutting-edge propulsion technology.”

Once TF2 achieves full operations, and following the completion of HTX testing, the company plans to make the facility available to industry, technology developers, and universities who could benefit from the facility’s unique test capabilities.

Distribution Statement A:

Approved for Public Release, Distribution Unlimited
https://www.reactionengines.co.uk/reaction-engines-begins-construction-high-temperature-airflow-test-facility-colorado/
 

steelpillow

So many projects, so little time...
Senior Member
Joined
Jun 25, 2014
Messages
556
Reaction score
53
Website
www.steelpillow.com
http://www.bbc.co.uk/news/science-environment-43732035

Rolls-Royce and Boeing invest in UK space engine
By Jonathan Amos BBC Science Correspondent

"Reaction Engines Limited (REL), the UK company developing a revolutionary aerospace engine, has announced investments from both Boeing and Rolls-Royce. ... "The new investments amount to £26.5m. ... It lifts the total capital raised in the past three years to about £100m."

So both Rolls and BAe are back on board after the HOTOL too-much-too-soon exercise.

REL is approaching important demonstration milestones.
In Colorado this summer, it will begin further testing of the pre-cooler technology, confronting it with conditions that simulate the very hot airstreams encountered when vehicles move at hypersonic speeds.
This will be done under contract with the US Defense Advanced Research Projects Agency (DARPA).


Nice to see a timeframe appearing.
 

Flyaway

CLEARANCE: Top Secret
Joined
Jan 21, 2015
Messages
2,235
Reaction score
296
Here’s the AW article just posted covering this news.

http://m.aviationweek.com/defense/boeing-rolls-royce-back-reaction-hypersonic-engine-developer

Here’s the Boeing Press Release.

http://boeing.mediaroom.com/2018-04-11-Boeing-HorizonX-Invests-in-Reaction-Engines-a-UK-Hypersonic-Propulsion-Company?sf186806280=1

https://twitter.com/ReactionEngines/status/984341611390947328?s=20

Our new partners bring invaluable expertise in both #hypersonics and engine technologies and will support key elements of the SABRE development programme. @RollsRoyce @Boeing @BoeingUK
New tweet & new image I think.
 

Flyaway

CLEARANCE: Top Secret
Joined
Jan 21, 2015
Messages
2,235
Reaction score
296
Here’s the UK government Press Release.

Global aerospace giants invest in UK firm Reaction Engines

Science Minister Sam Gyimah hails new private investment from Boeing and Rolls-Royce as a 'vote of confidence' in British-built SABRE rocket and jet engine.

Oxfordshire-based Reaction Engines has secured a further £26.5 million to support the development of SABRE™ - a revolutionary new class of aerospace engine combining jet and rocket technologies.

The UK Government has previously committed £60 million funding via the UK Space Agency and the European Space Agency to support the development of the project. The new strategic investors are Boeing HorizonX Ventures, the investment arm of the world’s largest aerospace company Boeing; and Rolls-Royce, which has been at the forefront of British engineering for over a century.

They join BAE Systems, which invested £20.6 million in Reaction Engines in 2015 and is providing further investment in this round, as well as financial investors Baillie Gifford Asset Management and Woodford Investment Management.

Together these investments take the total raised by Reaction Engines in the last three years to over £100 million.

Sam Gyimah, Minister of State for Universities, Science, Research and Innovation, said:

“These investments are a real vote of confidence in Reaction Engines and its revolutionary SABRE engine, which has benefited from £60m in UK Government support. Boeing and Rolls-Royce will bring world-class expertise to the project ahead of its testing at Westcott, alongside the new National Space Propulsion Facility.

“This is an exciting time as the UK’s commercial space industry goes from strength to strength, boosting the economy and creating high-skilled jobs across the country. Through our ambitious Industrial Strategy, we are working with the sector to pursue new opportunities, develop technologies and infrastructure, and enable small satellite launch and sub-orbital flight from UK spaceports for the first time.”

Reaction Engines is currently constructing a new facility in Westcott, Buckinghamshire, UK for SABRE testing. The UK Space Agency is also investing more than £4 million in a National Propulsion Test Facility on the same site, which has a strong history of rocketry research for defence and space development.

Mark Thomas, Chief Executive of Reaction Engines said:

“This is a significant milestone for Reaction Engines and I am delighted to welcome our new strategic and financial shareholders. In addition to providing our largest round of private investment, these new partners bring invaluable expertise in both hypersonics and engine technologies with significant access to target markets. This is not only a vote of confidence in our technology but also underlines belief in our ability to develop a thriving commercial business which will provide strong financial returns for our shareholders.”

Find out more about the UK National Space Propulsion Facility
 

steelpillow

So many projects, so little time...
Senior Member
Joined
Jun 25, 2014
Messages
556
Reaction score
53
Website
www.steelpillow.com
Interesting that the new concept artwork has the engines well to the rear. That damning NASA report last year on the rocket plumes must have been quite a wake-up call for RE.

But why is one of the SABRE engines firing off without taking the spaceplane with it? A thermal protection fail-safe? ;)

 

sferrin

CLEARANCE: Above Top Secret
Senior Member
Joined
Jun 3, 2011
Messages
11,944
Reaction score
285
That's not a free-flying engine. It's a kick-stage to take the payload the rest of the way into orbit.
 

Archibald

CLEARANCE: Top Secret
Senior Member
Joined
Jun 6, 2006
Messages
2,397
Reaction score
163
That picture is freakkin' awesome, and so is the "baby Skylon" B)
 

Flyaway

CLEARANCE: Top Secret
Joined
Jan 21, 2015
Messages
2,235
Reaction score
296
Precursor to Hypersonic Engine Heat Exchanger Tests

Advanced propulsion developer Reaction Engines is nearing its first step toward validating its novel air-breathing hybrid rocket design at hypersonic conditions by firing up a vintage General Electric J79 turbojet to act as a heat source for testing, expected later this month.

The ex-military engine, formerly used in a McDonnell Douglas F-4, is a central element of Reaction’s specially developed high-temperature airflow test site, which will soon be commissioned at Front Range Airport, near Watkins, Colorado. The J79 will provide heated gas flow in excess of 1,000C (1,800F) which, together with conditioned ambient air, will be mixed to replicate inlet conditions representative of flight speeds up to and including Mach 5.

The flow will verify the operability and performance of the pre-cooler heat exchanger (HTX), which is at the core of Reaction’s Sabre (synergistic air-breathing rocket engine). It is also key to extracting oxygen from the atmosphere to enable acceleration to hypersonic speed from a standing start. The HTX will chill airflow to minus 150C in less than 1/20th of a second, and pass it through a turbo-compressor and into the rocket combustion chamber where it will be burned with sub-cooled liquid hydrogen (LH) fuel. Beyond Mach 5, and at an altitude approaching 100,000 ft. the inlet will be closed and the engine will continue to operate as a closed-cycle rocket engine fueled by onboard liquid oxygen and LH.
However, given the recent additional funding, Thomas says that “for the full demonstrator there is definitely a possibility of accelerating the program with the support we are achieving and the capability we can potentially bring to bear. For the moment, our place holder is that we will do the core engine demonstration and the center piece of the overall system in 2020 and that would be the start of a longer development activity. But what we are really looking at is full-scale development into flight test, and what opportunities do we have now to accelerate that?”
https://www.reactionengines.co.uk/turbojet-runs-precursor-hypersonic-engine-heat-exchanger-tests/
 

Flyaway

CLEARANCE: Top Secret
Joined
Jan 21, 2015
Messages
2,235
Reaction score
296
New presentation apparently.

https://www.airpower.org.uk/wp-content/uploads/2018/05/Dr-Robert-Bond-presentation.pdf
 

steelpillow

So many projects, so little time...
Senior Member
Joined
Jun 25, 2014
Messages
556
Reaction score
53
Website
www.steelpillow.com
Flyaway said:
New presentation apparently.

https://www.airpower.org.uk/wp-content/uploads/2018/05/Dr-Robert-Bond-presentation.pdf
Very interesting, and new to me at any rate, is the bypass air duct with its own burner. This appears to help take it up to the Mach 5+ region, working as a conventional ramjet, before the core transitions to rocket mode. Scramjet mode above that appears to be scrupulously avoided. All in all, somewhat reminiscent of the dual-cycle J-58 engines in the Lockheed Blackbirds. But multiple flame cans? Come on guys, that's so 1940s! And one has to ask, if the SABRE thermodynamic cycle is so much better, why bypass it?

Then again, according to this BBC piece http://www.bbc.co.uk/news/science-environment-44112519: "If Bloodhound SSC drove through the [the Ashton Gate football] stadium at full speed (1,000mph = 447m/s), then driving the 100+ metres length of the pitch would take less than one-third of a second." 1,000 mph is around Mach 1.3 and the other numbers give around 300 metres per second. It hardly seems to equate to "Cool the hot incoming air from 1000 deg C in 1/20th second (Mach 5)" in a couple of metres or so, suggesting that Mach 3 (average speed between Mach 5 at the inlet and and Mach 1 at the outlet) equates to around 50 metres per second. The first example is broadly correct, so the Powerpoint number should be closer to 1,000 metres per second, making it a factor of 20 off and the transit time through the cooler more like 1/400 second. Or am I missing something?
 

Zootycoon

CLEARANCE: Confidential
Joined
May 27, 2008
Messages
163
Reaction score
101
The bypass burner contributes only a small fraction of the total thrust;- from memory near zero at zero speed, 15% in the Mach 2-4 range, dropping to about 5% at Mach. This is unlike J58 where the bypass ramjet (both intake and duct) provides the majority of the thrust when in Mach 3 cruise. The reason for Sabres bypass ramjet is that more liquid H2 is required to cool the air entering the compressor than is used in the compressor fed combustion chamber. In essence the bypass burner dispose’s of the excess, now hot hydrogen in a way which gets some thrust.

On your second point, the task of the air intake is to convert the air’s kinetic energy into potential energy in terms of pressure. But if a gas is compressed it inherently get hot as well. The air intake produces the pressure and temperature rise by slowing the air’s velocity by making it pass through a geometry which creates multiple shock waves. Hence when the air arrives at the heat exchanger it’s at high pressure, it’s hot and it’s traveling at less than Mach 1, which in turn matches the time quoted for the air to pass through the HTX.
 
Top