The Reaction Engines Skylon/SABRE Master Thread (7)

[adrianwyard]

And here's yet another design. The powerplant sounds very SABREy as it's M5 combined cycle with pre-cooler and ramjet. Apparently the plan is to one day jet the President around in one of these!

https://www.hermeus.com/aug-06-2020

Hermeus Wins Air Force Investment After Demonstrating Mach 5 Engine
 
ATLANTA, GA - Hermeus Corporation, the aerospace company developing Mach 5 commercial aircraft, has partnered with the U.S. Air Force and the Presidential and Executive Airlift Directorate to work toward hypersonic travel for the Department of Defense.  This award comes under an Other Transaction For Prototype Agreement Direct to Phase II contract through AFWERX after Hermeus successfully tested a Mach 5 engine prototype in February 2020.
​
The effort is focused on rapidly assessing modifications to Hermeus Mach 5 aircraft to support the Presidential and Executive Airlift fleet.  Early integration of unique Air Force requirements for high-speed mobility and evaluation of interfaces between high-speed aircraft and existing communications, airport, and air traffic control infrastructure lays the groundwork for a seamless transition to service.  Additionally, Hermeus will prepare test plans to reduce technical risk associated with these modifications to support Air Force requirements. 
​
Brigadier General Ryan Britton, Program Executive Officer for Presidential and Executive Airlift commented on the program: "Leaps in capability are vital as we work to complicate the calculus of our adversaries.  By leveraging commercial investment to drive new technologies into the Air Force, we are able to maximize our payback on Department of Defense investments.  The Presidential and Executive Airlift Directorate is proud to support Hermeus in making this game-changing capability a reality as we look to recapitalize the fleet in the future."
​
Preceding the award, the Hermeus team designed from scratch, built, and successfully tested a Mach 5 engine prototype, in only 9 months.  The test campaign both served as risk reduction for Hermeus' turbine-based combined cycle engine architecture and illustrates the team's ability to execute with schedule and funding efficiency.  "Using our pre-cooler technology, we've taken an off-the-shelf gas turbine engine and operated it at flight speed conditions faster than the famed SR-71.  In addition, we've pushed the ramjet mode to Mach 4-5 conditions, demonstrating full-range hypersonic air-breathing propulsion capability," said Glenn Case, Hermeus’ CTO.

[ChrisWilson68]

I don't remember ever hearing REL or anyone associated with them saying SABRE technology is applicable to an engine that doesn't go past Mach 3.  Is there something I missed where they said that?

Yes.

Where you confuse not having with not wanting.

What is your intention with this response to my post?  Is it to be insulting or helpful?

[john smith 19]

And here's yet another design. The powerplant sounds very SABREy as it's M5 combined cycle with pre-cooler and ramjet. Apparently the plan is to one day jet the President around in one of these!

https://www.hermeus.com/aug-06-2020

Probably better in the "Hypersonics" thread.

[adrianwyard]

Sure. Mentioned here because it sounds very similar to REL's SABRE/SCIMITAR and this project has a USAF connection like REL too. I wonder if this is connected in any way to REL's USAF research.

[Asteroza]

And here's yet another design. The powerplant sounds very SABREy as it's M5 combined cycle with pre-cooler and ramjet. Apparently the plan is to one day jet the President around in one of these!

https://www.hermeus.com/aug-06-2020

Probably better in the "Hypersonics" thread.

There's also a Hermeus thread somewhere...

[JCRM]

Mach 3 doesn't require SABRE. See: Valkyrie, SR-71, Archangel, etc.

Without wishing to be mean that is a fairly obvious point, but are we sure that a Mach 3 engine cannot benefit from a SABRE cycle or at least some of the SABRE technologies?

in 2019 Rolls Royce/Bae/REL announced a two year project to examine integrating a precooler with an EJ-200 engine - mostly to see if it does extend the performance envelope. It's possible that may make a Mach 3 engine easier to produce and/or operate.

[john smith 19]

And here's yet another design. The powerplant sounds very SABREy as it's M5 combined cycle with pre-cooler and ramjet. Apparently the plan is to one day jet the President around in one of these!

https://www.hermeus.com/aug-06-2020

Probably better in the "Hypersonics" thread.

There's also a Hermeus thread somewhere...

Pity the search function still does not work. 

[john smith 19]

And here's yet another design. The powerplant sounds very SABREy as it's M5 combined cycle with pre-cooler and ramjet. Apparently the plan is to one day jet the President around in one of these!

https://www.hermeus.com/aug-06-2020

Hermeus Wins Air Force Investment After Demonstrating Mach 5 Engine
The effort is focused on rapidly assessing modifications to Hermeus Mach 5 aircraft to support the Presidential and Executive Airlift fleet.  Early integration of unique Air Force requirements for high-speed mobility and evaluation of interfaces between high-speed aircraft and existing communications, airport, and air traffic control infrastructure lays the groundwork for a seamless transition to service.  Additionally, Hermeus will prepare test plans to reduce technical risk associated with these modifications to support Air Force requirements. 
​

IOW, making sure the right radio equipment is on board and the seats are wide enough to accommodate the executive posterior. 

There is nothing worse than being a world leader who cannot sit in their own planes seats.

Preceding the award, the Hermeus team designed from scratch, built, and successfully tested a Mach 5 engine prototype, in only 9 months.  The test campaign both served as risk reduction for Hermeus' turbine-based combined cycle engine architecture and illustrates the team's ability to execute with schedule and funding efficiency.  "Using our pre-cooler technology, we've taken an off-the-shelf gas turbine engine and operated it at flight speed conditions faster than the famed SR-71.  In addition, we've pushed the ramjet mode to Mach 4-5 conditions, demonstrating full-range hypersonic air-breathing propulsion capability," said Glenn Case, Hermeus’ CTO.

As I posted in the general hypersonics thread one of their suppliers is PBS, who make small turbo jets.  So "designed from scratch" is something of an exaggeration.

There other claim depends on how you read the following

we've pushed the ramjet mode to Mach 4-5 conditions

Is that M4.5? In the range of M4-M5? 
The modern standard definition of hypersonic is M5+. Below M5 it's very fast, but not hypersonic.

To put this in perspective the energy level they are dealing with is about that of the heat exchanger built by a PhD student funded by REL around the turn of the century.

The turbo jets they appeared to have used for the test are around 292lb of thrust. The J58 dry thrust was 18000 lb and with afterburner 25000 lb.  A scale up of about 61x.

Since this is the Reaction Engines thread I'll note that the two big issues that REL solved were frost control with a cryogenic fuel and mfg of a large heat exchanger reliably

A full scale HX has literally millions of joints that have to be made. IOW a joint failure rate of less than 1 in 10^6.  How you do that, and what are the key factors that ability is affected by are difficult to learn.

At a small scale you can have a huge scrap rate and still manage to make something that works. Build 20 to get 1 that works. But with a million joints how many do you have build to get 1 perfect one by shear dumb luck?

I'll also note Hermeous are from a rocket background and this can lead to poor design choices when you're relying more on winged flight.

Time will tell if they manage to produce something or not.

[john smith 19]

hermeus thread located   here

If we could move any further discussion to it?

[john smith 19]

Sure. Mentioned here because it sounds very similar to REL's SABRE/SCIMITAR and this project has a USAF connection like REL too. I wonder if this is connected in any way to REL's USAF research.

I was re reading the USAF/SWEI TSTO design today.

I was once again struck by how very odd some of their assumptions were. 

They have a landing gear mass that's 3.9% of GTOW. This is well above what both the B58 and XB70 landing gear achieved in the 1950's and 60's. They have a LH2/LO2 upper stage gg engine that can't manage better than 33:1 (the J-2 on the Saturn V did 73:1  5 decades ago). Meanwhile they are allowing a 25% mass growth weight for an upper stage.

Their booster (which actually uses the SABRE) uses conformal LH2 tanks at each end and then has the LOX tanks as multiple cylinders wrapped around a bottom opening payload bay.
[EDIT I forgot the 5g RTLS turn after the US has separated ]

They state that due to company confidentiality reasons they cannot reveal what Isp or thrust they were using in their design. Historically they have assumed that a HTOL vehicle needs at least  a T/W ratio of 0.7:1 to get through M1.

Which is interesting as I also looked up the wikipedia entry on Concorde.

That lists it's mass while taxiing IE virtually fully loaded, as 418 000lb with its 4 engines (not on AB, which was 18.9% higher) at 128 000 lb in total. IOW a T/W ratio of 0.306:1 (or 0.364:1 with full AB) .
This from an actual large aircraft that achieved mach 2. 

or the XB70, whose dry engine thrust was 22% of GTOW while it's AB thrust was 30% of GTOW.

Yet somehow it managed to get to M3 and sustain it for up to 32 minutes at a time.

[john smith 19]

They state that due to company confidentiality reasons they cannot reveal what Isp or thrust they were using in their design. Historically they have assumed that a HTOL vehicle needs at least  a T/W ratio of 0.7:1 to get through M1.
.
.
.
.
 the XB70, whose dry engine thrust was 22% of GTOW while it's AB thrust was 30% of GTOW.

Yet somehow it managed to get to M3 and sustain it for up to 32 minutes at a time.

In case it's not clear why this matters essentially halving the believed needed T/W ratio doubles the potential GTOW of a flight vehicle.

So a test vehicle with 2 20 000 Kg thrust engines can now have a GTOW of 133.3 tonnes, rather than 57.1.  tonnes. That can be traded for more propellant (longer endurance flight tests), higher structural margins (lower risk of structural failure), bigger experimental package (better spatial resolution, wider measurement range) etc. 

Which begs the question "Do we design a vehicle for a T/W ratio that we know has gotten through the sound barrier (for several significant aircraft), or do we design a vehicle that can get through the limits set by some consultancy who might be hired to do due diligence" ?

No ground launched  aircraft has ever broken the sound barrier before it has burnt off a measurable  fraction of its on board fuel load.

[JCRM]

I was re reading the USAF/SWEI TSTO design today.

I was once again struck by how very odd some of their assumptions were. 

They have a landing gear mass that's 3.9% of GTOW. This is well above what both the B58 and XB70 landing gear achieved in the 1950's and 60's. They have a LH2/LO2 upper stage gg engine that can't manage better than 33:1 (the J-2 on the Saturn V did 73:1  5 decades ago). Meanwhile they are allowing a 25% mass growth weight for an upper stage.

They said they're using standard parametric models, so while the undercarriage weight might be optimisable they haven't done that.
The expendable upper stage is "as simple as possible to minimize its cost."
They appear to have been cautious with their figures, while producing a payload mass fraction which is still more than half of reusable F9.  It would be hard to dismiss these concepts as relying on wildly optimistic values

Their booster uses conformal LH2 tanks at each end and then has the LOX tanks as multiple cylinders wrapped around a bottom opening payload bay.

A LOX tank either side of the payload, and two LH2 tanks above the payload. For a SABRE 4 engine, I'd assume the conformal tanks would be used for airbreathing, and the payload tanks for "normal" rocket mode.
 

They state that due to company confidentiality reasons they cannot reveal what Isp or thrust they were using in their design. Historically they have assumed that a HTOL vehicle needs at least  a T/W ratio of 0.7:1 to get through M1.

But there's nothing to suggest that is their assumption here. That T/W ratio gives them a rotation distance of
1280 ft, giving Newquay airport 7720 ft breaking distance in the event of an abort at rotation

[john smith 19]

They said they're using standard parametric models, so while the undercarriage weight might be optimisable they haven't done that.
The expendable upper stage is "as simple as possible to minimize its cost."
They appear to have been cautious with their figures, while producing a payload mass fraction which is still more than half of reusable F9.  It would be hard to dismiss these concepts as relying on wildly optimistic values

No. They'd be dismissed on the grounds that they only give half the payload of an F9 instead.

But there's nothing to suggest that is their assumption here. That T/W ratio gives them a rotation distance of
1280 ft, giving Newquay airport 7720 ft breaking distance in the event of an abort at rotation

Actually on closer checking it does say exactly that.

The engines were sized for a takeoff thrust to weight of 0.7.

So yes the design is grossly conservative against vehicles that have not just been designed but have actually flown IE Concorde and the XB70.
Likewise reusable rocket engines designed for 1950's aircraft could manage a T/W ratio of 43:1. So 35:1 is not just "conservative" it's grossly conservative.

[JCRM]

It would be hard to dismiss these concepts as relying on wildly optimistic values

No. They'd be dismissed on the grounds that they only give half the payload of an F9 instead.

I don't think so. Given the difference in scale and lack of optimisation, 1/2 a Falcon 9 is "in the right ball park."

Unfortunately there are no 5000lb to 100mile partially reusable vehicles to compare against.

Historically they have assumed that a HTOL vehicle needs at least  a T/W ratio of 0.7:1 to get through M1.

But there's nothing to suggest that is their assumption here

Actually on closer checking it does say exactly that

The engines were sized for a takeoff thrust to weight of 0.7.

Nope, can't see where it says the 0.7 is to break the sound barrier.

Given the US Airforce has been operating B-1s for nearly half a centuary it seems strange they should still have a belief that a 0.7 T/W ratio is neccessary for supersonic craft.

So yes the design is grossly conservative against vehicles that have not just been designed but have actually flown IE Concorde and the XB70.

Concorde had thrust reversers and the Valkyrie drag 'chutes which means they should be able to slow down more quickly than this booster.

In fact, given the design hits a peak axial acceleration of 1.5g for the SABRE engines - if anything I'd say they were undersized.

Likewise reusable rocket engines designed for 1950's aircraft could manage a T/W ratio of 43:1. So 35:1 is not just "conservative" it's grossly conservative.

I'm not entirely clear where you are getting the 35:1 ratio from, My assumption is you're taking the "propulsion" mass of 1000 pounds as a fraction of the all up weight, and eyballing the initial acceleration of the US as 1g to give a thrust of 3600 pounds - but I'd suggest to you that "propulsion" for the upper stage includes more than just the engine.
For instance, the similarly sized  Centaur D had a propulsion system budget of 1,226 lbm , and a thrust of 29,500 lbf, giving a ratio of "only" 23:1

I don't know the reasons behind the trajectory decisions made, but it does seem to release the upper stage at around 80km altitude and 9000 km/h which is similar to other reusable first stages.

[FutureSpaceTourist]

From the Virgin Galactic mach3 aircraft thread:

Reaction Engines and Rolls-Royce announce new strategic partnership agreement
21 August 2020

Reaction Engines Ltd and Rolls-Royce plc today announced a new strategic partnership agreement to develop high-speed aircraft propulsion systems and explore applications for Reaction Engines’ thermal management technology within civil and defence aerospace gas turbine engines and hybrid-electric systems.
“We have been working closely with Reaction Engines for the past two years, including exploring the potential of high-Mach systems for defence applications, and I am delighted that we are able to strengthen that relationship,” said Mark Thompson, Director of Global Strategy & Business Development, Rolls-Royce. “This partnership follows our recent announcements with Boom Supersonic and Virgin Galactic.”
“Reaction Engines’ thermal management skills, added to our suite of existing technologies and capabilities, will further assist us as we explore opportunities in supersonic and hypersonic aviation,” Thompson added. “Building on our many decades of innovation, we will also explore the use of Reaction Engines’ technology within our aerospace gas turbines and its potential application in future hybrid-electric propulsion systems, as we look to make flying ever more efficient and sustainable.”
Additionally, Rolls-Royce is making a further investment in Reaction Engines as part of a wider funding round. The two companies have been working together since 2018, including on the first phase of a UK Ministry of Defence contract to undertake design studies, research, development, analysis and experimentation related to high-Mach advanced propulsion systems.
“This strategic partnership is about developing market ready applications for Reaction Engines’ technology in next generation engines and is a significant step forward for our technology commercialisation plans,” said Mark Thomas, Chief Executive of Reaction Engines. “Our proprietary heat exchanger technology delivers incredible heat transfer capabilities at extremely low weight and a compact size. We look forward to expanding our international collaboration with Rolls-Royce, a global leader in power systems, to bring to market a range of applications that will transform the performance and efficiency of aircraft engines, enable high speed – supersonic and hypersonic – flight and support the drive towards more sustainable aviation through innovative new technologies.”

https://www.rolls-royce.com/media/press-releases/2020/21-08-2020-reaction-engines-and-rolls-royce-announce-new-strategic-partnership-agreement.aspx

[Asteroza]

From the Virgin Galactic mach3 aircraft thread:

Reaction Engines and Rolls-Royce announce new strategic partnership agreement
21 August 2020

Reaction Engines Ltd and Rolls-Royce plc today announced a new strategic partnership agreement to develop high-speed aircraft propulsion systems and explore applications for Reaction Engines’ thermal management technology within civil and defence aerospace gas turbine engines and hybrid-electric systems.
“We have been working closely with Reaction Engines for the past two years, including exploring the potential of high-Mach systems for defence applications, and I am delighted that we are able to strengthen that relationship,” said Mark Thompson, Director of Global Strategy & Business Development, Rolls-Royce. “This partnership follows our recent announcements with Boom Supersonic and Virgin Galactic.”
“Reaction Engines’ thermal management skills, added to our suite of existing technologies and capabilities, will further assist us as we explore opportunities in supersonic and hypersonic aviation,” Thompson added. “Building on our many decades of innovation, we will also explore the use of Reaction Engines’ technology within our aerospace gas turbines and its potential application in future hybrid-electric propulsion systems, as we look to make flying ever more efficient and sustainable.”
Additionally, Rolls-Royce is making a further investment in Reaction Engines as part of a wider funding round. The two companies have been working together since 2018, including on the first phase of a UK Ministry of Defence contract to undertake design studies, research, development, analysis and experimentation related to high-Mach advanced propulsion systems.
“This strategic partnership is about developing market ready applications for Reaction Engines’ technology in next generation engines and is a significant step forward for our technology commercialisation plans,” said Mark Thomas, Chief Executive of Reaction Engines. “Our proprietary heat exchanger technology delivers incredible heat transfer capabilities at extremely low weight and a compact size. We look forward to expanding our international collaboration with Rolls-Royce, a global leader in power systems, to bring to market a range of applications that will transform the performance and efficiency of aircraft engines, enable high speed – supersonic and hypersonic – flight and support the drive towards more sustainable aviation through innovative new technologies.”

https://www.rolls-royce.com/media/press-releases/2020/21-08-2020-reaction-engines-and-rolls-royce-announce-new-strategic-partnership-agreement.aspx

That pic would suggest that the initial work on adapting REL cooler tech to the EJ-200 may have morphed into a civil variant of whatever engine development is scheduled for the the new UK Tempest fighter then for Virgin's mach 3 aircraft? Sorta similar to how some military/civil turbofan/turbojet cores will be adapted for the recent crop of supersonic business jets, as nobody seems to want to do a 100% clean sheet design, and adapt an existing engine core?

This, plus the F1 racing cooler work, would suggest REL is getting experienced in doing room temperature-ish hydrocarbon liquid fuel cooling as an adaptation of the initial SABRE helium/hydrogen work. Extending the concepts behind the F-35 being a fuel cooled fighter jet.


As a side note, does REL cooler tech fundamentally force longer inlets/nacelles with the current boatload of tiny tubes setup? I wonder if there's some way to both shorten the length and integrate the cooler assembly, maybe something like the following boeing patent, using 3D compression ramp grids in the inlet as a host for the heat exchanger?

https://patents.google.com/patent/US8210474B2/en

[Star One]

I imagine the Mayhem program is not unrelated to this.

Cross posting the below from the hypersonic thread.

Mayhem is a expendable testbed program designed at developing engines for things like the SR-72.

This is an area of increasing interest around the world, as well. Just today, U.K.-headquartered Rolls-Royce, which manufacturers traditional jets engines, announced it was forming a new partnership with Reaction Engines, another company in the United Kingdom working on combined cycle engines for use on a space-launch mothership, known as a mothership-based two-stage-to-orbit concept, which you can read about in more detail in this past War Zone feature.

https://www.thedrive.com/the-war-zone/35921/air-forces-mayhem-project-tied-to-hyperonic-engines-for-planes-such-as-the-sr-72

[The Ex-Engineer]

Another Reaction Engines article that just caught my eye https://newatlas.com/aircraft/reaction-engines-ammonia-carbon-free-aviation-fuel/

Possibly the first time I've officially seen mention of Reaction Engines' pre-cooler technology working with ammonia as a fuel.

Not entirely sure why the study talks about partially decomposing the ammonia prior to combustion? Anyone have any thoughts?

Anyway, great to see they are working on this. In addition to the obvious environmental issues, ammonia might be perfectly suited for Mach 3-4 supersonic travel with more scope for sub-cooling over traditional hydrocarbon fuels but without the more major challenges of working with deep-cryogenic fuels like hydrogen or methane that would be required for Mach 5 designs.

(PS If there's a more appropriate thread for this specific discussion, someone please let me know.)

[JCRM]

Possibly the first time I've officially seen mention of Reaction Engines' pre-cooler technology working with ammonia as a fuel.

I don't see the precoolers being mentioned in relation to this story. REL have also done work on microchannel heat exchangers for transferring heat to the liquid fuel, which is more likely to be appropriate here

<wrong, deleted>

REL's version of the story

[CameronD]

Possibly the first time I've officially seen mention of Reaction Engines' pre-cooler technology working with ammonia as a fuel.

I don't see the precoolers being mentioned in relation to this story. REL have also done work on microchannel heat exchangers for transferring heat to the liquid fuel, which is more likely to be appropriate here

Not entirely sure why the study talks about partially decomposing the ammonia prior to combustion? Anyone have any thoughts?

possibly partial because full decomposition is too "difficult" most likely in terms of weight or maintenance.
As for splitting it, hydrogen burns hotter, faster and easier, and doesn't directly produce NOx

REL's version of the story

It's an interesting idea but ammonia is not without it's challenges - not the least of which is the amount of energy used to manufacture it in the first place.  Also, according to Wikipedia, one of the main industrial byproducts of ammonia production is CO2 (that's their "low emissions" gone).

But the main issue I see with their current plan is this bit: From the previous article "In this new system, the ammonia is stored as a chilled, pressurized liquid in the wings of the airplane just as kerosene-based fuel is today." Aircraft don't spend their entire lives cruising at altitude - refuelling is also required, generally on hot tarmacs whilst loading passengers.
All current airplane fuel tanks vent harmlessly to atmosphere and fuel spills are fairly simply and safely cleaned up, but ammonia is a caustic and flammable chemical that is toxic by inhalation, resulting in permanent lung damage and even death at high exposure levels - and the "chilled, pressurised liquid" is sure to be venting on a continuous basis.  A spill in an airport environment would be deadly.

As interesting as it is, I'm not at all sure we'll see this leave the drawing board.