The Reaction Engines Skylon/SABRE Master Thread (6)

[t43562]

There was an interesting concept picture of a Hypersonic aircraft which may or may not have been a business jet. Looked like concorde but with shallow V stabilisers and no tail (sorry I'm not an expert - hope that makes some sense).  The engine nozzles are tucked up in v-shaped areas next to the fuselage. Only saw from behind.
         \  /
---<ooOoo>----

but the stabilisers are too steep in this one and the engines far too large

[SICA Design]

I gather (speaking with my wife who was there) that Skylon is definitely on the back-burner until the 2030s, with no mention made of 2STO or other orbital variants, just hypersonic mil hardware and perhaps biz jets.

Main focus was on engine ground test, with plenty of engine-specific questions from the multitude of knowledgeable RR staff (estimated ~500 people there?) who'd come to the lecture straight after work.

I'll post more (probably Friday when home) once I've listened to your audio and read the notes that she took...

[john smith 19]

What did they need BAE for, regulatory hurdles in the US and the ability to the ball rolling with the DOD?

From the BAE video, it seems it lasers!

It such seem like this project is devolving into deal making rather than engine making.

Curious thing about that.
When Mark Thomas wrote his follow up letter to the House of Commons committee who asked why REL had not received the grant George Osborn promised in 2013 he stated the terms had been changed. Instead of paying the £60m over 2 years which the government hoped would allow them to get other partners they had to get a partner in before the money was released.

Leaving REL needing to get an aerospace business partner at short notice. 

Allowing BAe to buy 20% of the company for £20m.

[t43562]

What Mark Thomas said was that 2STO was *the* next thing to happen and that SSTO was on the back burner - just because it causes such a huge leap in development cost.   

He implied that the management were more focused on things that can actually come off and possibly make money. I think if you can develop all sorts of 2STOs and military jets and whatever and spin-offs for heat exchangers then the cost of developing a lot of the technology can be assigned to those programmes rather than Skylon. So to me that means that at some point Skylon or its successor will not be 1 billion apiece.

I have some notes on things that were on the slides. I couldn't record with my phone and take pics at the same time - sorry.

Nozzles need to operate at very different pressures and temperatures :
   20Bar - 230K (or was that 2300K - my writing is bad)
   160Bar - 3000K   (rocket mode)

The Microchannel heat exchangers:
50K - 950K (whatever that means)
30 Bar - 300 Bar
Stainless steel/Titanium
Can be spun off for satellite applications.

There is an internal debate about their flight test article - should it be useful or just a test.

Helium Turbo pump problems:
  very long - 0.5m.
  200 bar inlet
  multistage modules
  uncooled turbie
  low mach number
  lots of stages
  managing bearing loads
  tip clearances
   

[john smith 19]

Nozzles need to operate at very different pressures and temperatures :
   20Bar - 230K (or was that 2300K - my writing is bad)
   160Bar - 3000K   (rocket mode)

This is quite a big change. IIRC they were looking nearer 100bar in air breathing. Obviously this cuts down the power needed quite a lot. It would have been good to know if they are definitely going with SABRE 4 and and E/D nozzle.

The Microchannel heat exchangers:
50K - 950K (whatever that means)
30 Bar - 300 Bar
Stainless steel/Titanium
Can be spun off for satellite applications.

This I think is the "cold end" of the pre cooler loop, where the heat not used to drive the pump and compressor turbines is put into the LH2. Meggett, Battelle Labs and IIRC there's a startup from Case Western Reserve U that do stuff like this. Meggett I think picked up their IP from an Australian company they bought.

There is an internal debate about their flight test article - should it be useful or just a test.

The flight test will be useful. Question is how far beyond the AB/rocket transition (one of the key known unknowns) it will go? If it's just beyond transition (c M5.6 ?) then to put something in orbit it needs a fairly significant 2nd stage even if it's putting a cubesat up. That has to be planned in and designed. Likewise is the flight test vehicle 1 shot or expected to fly multiple times?

Of course if you could make a FTV that could reach, and return from orbit, even if only to deploy a cubesat that would be a powerful validation of the whole technology.

I suspect this results in too great a growth in FTV size to be viable. That means you need a 2nd stage which tells you nothing more about SABRE (it's already shut down) but does add significant needed resources.

OTOH it can (in principal) start to generate revenue. The challenge is if it's expendable to make it so cheap to build (and so cheap to develop) that it pays for itself in a few flights and starts to  put money in the REL revenue account.

If it's economically reusable then it's a question of how big a payload will it carry and what price.

This is historically where UK companies have come seriously unstuck.

Helium Turbo pump problems:
  very long - 0.5m.
  200 bar inlet
  multistage modules
  uncooled turbie
  low mach number
  lots of stages
  managing bearing loads
  tip clearances

I looked up "gas circulators" in gas cooled nuclear reactors, which are loosely similar technology. Only the Dragon reactor in Winfrith was He cooled and it used gas bearings by Brown Boveri. However they stated they scale up badly (SoA in gas cooled reactors is moving to active magnetic bearings, which seems risky. Others have been water cooled oil lubricated, but these have hit trouble with water leaks into the bearings). 
The Dragon gas circulator had very short blades (of the whole diameter 88% was disk, 12% was actual blade). This has issues because clearance losses (you still have to have some clearance between the blades and the casing) and boundary layer losses are a bigger proportion of the power involved. Similar issues arise in power MEMS systems. OTOH their small size means they can hit greater than 1 million RPM on air bearings.

Note that when SABRE design started AFAIK only the Pegasus engine on the Harrier had contra-rotating blades (to minimize gyroscopic effects). Today this is SOP on the Trent 900 series flying on the Airbus 380's. Bearings are key lift limiting components. Ceramic bearings seem to be better but the best option seems to be to eliminate an actual rolling or thrust element, hence some kind of grooved air or foil air bearing, provided the spinning parts aren't too heavy.

[Archibald]

I gather (speaking with my wife who was there) that Skylon is definitely on the back-burner until the 2030s, with no mention made of 2STO or other orbital variants, just hypersonic mil hardware and perhaps biz jets.

Main focus was on engine ground test, with plenty of engine-specific questions from the multitude of knowledgeable RR staff (estimated ~500 people there?) who'd come to the lecture straight after work.

I'll post more (probably Friday when home) once I've listened to your audio and read the notes that she took...

Dang !

[t43562]

I gather (speaking with my wife who was there) that Skylon is definitely on the back-burner until the 2030s, with no mention made of 2STO or other orbital variants, just hypersonic mil hardware and perhaps biz jets.

Main focus was on engine ground test, with plenty of engine-specific questions from the multitude of knowledgeable RR staff (estimated ~500 people there?) who'd come to the lecture straight after work.

I'll post more (probably Friday when home) once I've listened to your audio and read the notes that she took...

Dang !

I'm sorry but this is not quite correct. There was a lot of mention of 2STO and pictures of Orbital Access' designs. Yes Skylon doesn't look like it will be the first SABRE-powered vehicle to launch something because they feel they need to prove the technology. He also emphasised that some satellites were getting smaller so there are potentially a lot of opportunities which may not demand a 15 ton payload.

There was quite a lot of talk about military interest but I think that's just because it's a source of money and useful facilities really and a way to progress and I suppose it's what Mark Thomas knows about.

On the other hand, with a £10 billion pound development cost, who really thought Skylon would emerge without any kind of precursors, without any way to split the engine complexities off from the airframe and so on, without convincing the purse-string-holders that it can be done?

[knowles2]

I gather (speaking with my wife who was there) that Skylon is definitely on the back-burner until the 2030s, with no mention made of 2STO or other orbital variants, just hypersonic mil hardware and perhaps biz jets.

Main focus was on engine ground test, with plenty of engine-specific questions from the multitude of knowledgeable RR staff (estimated ~500 people there?) who'd come to the lecture straight after work.

I'll post more (probably Friday when home) once I've listened to your audio and read the notes that she took...

Dang !

I'm sorry but this is not quite correct. There was a lot of mention of 2STO and pictures of Orbital Access' designs. Yes Skylon doesn't look like it will be the first SABRE-powered vehicle to launch something because they feel they need to prove the technology. He also emphasised that some satellites were getting smaller so there are potentially a lot of opportunities which may not demand a 15 ton payload.

There was quite a lot of talk about military interest but I think that's just because it's a source of money and useful facilities really and a way to progress and I suppose it's what Mark Thomas knows about.

On the other hand, with a £10 billion pound development cost, who really thought Skylon would emerge without any kind of precursors, without any way to split the engine complexities off from the airframe and so on, without convincing the purse-string-holders that it can be done?

The one thing they kept trying to sale was that the engine was the more complicated part and proving that the engine could work could all be done on the ground, unlike other single stage to orbit vehicle engines, once the engines is fully tested, everything else was suppose to be essentially off the shelf technology.

The real issue REL has is that it couldn't and from all reports still can't raise the 300 million they need to build a flight ready test engine on the ground.

[john smith 19]

The one thing they kept trying to sale was that the engine was the more complicated part and proving that the engine could work could all be done on the ground, unlike other single stage to orbit vehicle engines, once the engines is fully tested, everything else was suppose to be essentially off the shelf technology.

That's a misrepresentation. SABRE is a key part of making Skylon work. If it works Skylon has to miss it's mass and strength targets by a lot to fail to deliver the planned performance. REL have never AFAIK called it OTS technology. However aircraft design is a process that has been gone through several thousand times, rather than the (at most) 100 for an ELV.

The real issue REL has is that it couldn't and from all reports still can't raise the 300 million they need to build a flight ready test engine on the ground.

Which explains why they've decided to go with a scaled down (but fully functional) test engine. Historically REL have avoided this approach because scaled systems have scale effects where you speed months coping with problems brought on by the small size of the test components that simply don't exist on the full size design.

An interesting point about such systems is that once you've built one the incremental cost of building a second engine is fairly low.  This would make a flight vehicle much more like a full size Skylon

There was quite a lot of talk about military interest but I think that's just because it's a source of money and useful facilities really and a way to progress and I suppose it's what Mark Thomas knows about.

I'm sure there considering all options. It's interesting they're talking to the MoD.

On the other hand, with a £10 billion pound development cost, who really thought Skylon would emerge without any kind of precursors, without any way to split the engine complexities off from the airframe and so on, without convincing the purse-string-holders that it can be done?

Skylon was specifically designed to minimize the interaction between airframe and engine. It's SCRamjets, that use forebody compression, where any slight change in the engine design means you have to redesign the whole airframe as well.

REL have always expected funding to be done in phases, with cash release dependent on results.

[Archibald]

What worries me is the talk about the helium loop, core of the SABRE, itself essential to Skylon. Looks they have run into some unexpected snags ?

[t43562]

My impression is that they are doing real development now and facing up to the things that they have been able to ignore up to this point. They have a good person working on helium turbopumps, for example, but they need access to the libraries of data and the codes and experience of an engine company so that they don't have to start from scratch like this for everything.

Also they do have a problem dealing with seals but that sounds like "the problem du jour" of which there are going to be many.

[john smith 19]

What worries me is the talk about the helium loop, core of the SABRE, itself essential to Skylon. Looks they have run into some unexpected snags ?

Not a problem. A simple statement of fact. The precooler does have a large number of joints. They have developed an effective joining method, but it requires certain conditions in the furnace to work reliably.

My impression is that they are doing real development now

They have been doing "real" development work on mfg of pre coolers since at least 2012 [EDIT in fact that was the start of the full size SABRE module pre-cooler test programme. The module would have been built roughly in the period 2010-2012]

Also they do have a problem dealing with seals but that sounds like "the problem du jour" of which there are going to be many.

There's a difference between saying seals are difficult and there being a problem.

Seals at high temperatures and pressures will have problems. The excessive leakage on the labyrinth seals on the preburner / LOX turbopump on the SSME partly resulted in each engine carrying an additional  270lb GHe tank. A seal upgrade programme  (tested but AFAIK not implement) used 1/3 the GHe. Brush seals (one of the types tested) seem to be something of a UK specialty. The tightest seem to be the "abradable" seals where the airfoil ends carve a path through a (relatively) soft ring, but these appear to be available on GE engines so may be proprietary. 

[t43562]

My impression is that they are doing real development now

They have been doing "real" development work on mfg of pre coolers since at least 2012 [EDIT in fact that was the start of the full size SABRE module pre-cooler test programme. The module would have been built roughly in the period 2010-2012]

Bad phrasing on my part, I think I mean they are designing components for the supporting systems which they have only treated at some sort of theoretical level before. It's exciting.

Also they do have a problem dealing with seals but that sounds like "the problem du jour" of which there are going to be many.

There's a difference between saying seals are difficult and there being a problem.

Seals at high temperatures and pressures will have problems. The excessive leakage on the labyrinth seals on the preburner / LOX turbopump on the SSME partly resulted in each engine carrying an additional  270lb GHe tank. A seal upgrade programme  (tested but AFAIK not implement) used 1/3 the GHe. Brush seals (one of the types tested) seem to be something of a UK specialty. The tightest seem to be the "abradable" seals where the airfoil ends carve a path through a (relatively) soft ring, but these appear to be available on GE engines so may be proprietary.

I listened again - they are feeling challenged by the seals specifically in the helium turbine that takes the helium out of the precooler. 

On listening again I heard that they're hiring out their vacuum furnace - they made nozzles for a moon lander apparently and bits and pieces of satellites.   Apparently it's a unique facility particularly in terms of how clean it is.  There is a worry that they might contaminate it, I think, if they aren't very careful and it's the cleanliness that makes it able to braze the inconel tubes of the precooler.

Other spinoffs include their attempt to get their microchannel heat exchangers into satellites (used to dump heat from the helium to hydrogen in SABRE).   They also think these might eventually be useful in civil jet engines.

[john smith 19]

Bad phrasing on my part, I think I mean they are designing components for the supporting systems which they have only treated at some sort of theoretical level before. It's exciting.

Yes that's always the issue with limited funds. Approximation and conservative design can take you only so far. Obviously new funds have helped them flesh out parts that till now have only been outlines, such as the ground test stand design. Until you've decided on a test engine size and level of accuracy a lot of areas would be provisional.

I listened again - they are feeling challenged by the seals specifically in the helium turbine that takes the helium out of the precooler. 

I think that you have that backward. Cold helium from the He/LH2 HX goes through the precooler and is raised in temperature and pressure. This then drives the turbine, which turns the compressor at the front of the engine, and any other systems attached to the same shaft. However making this work has huge payoffs since you can drive the LOX and air systems with an inert gas.

This is exactly the same rationale for full flow staged combustion engines running separate fuel and oxidizer rich preburners.  The engineering of turbines to survive in those pre burner environments (high speed and highly chemically active) is also very demanding, and of course both turbines have to work for the engine to work.

On listening again I heard that they're hiring out their vacuum furnace - they made nozzles for a moon lander apparently and bits and pieces of satellites.   Apparently it's a unique facility particularly in terms of how clean it is.  There is a worry that they might contaminate it, I think, if they aren't very careful and it's the cleanliness that makes it able to braze the inconel tubes of the precooler.

It's certainly a worry. it helps that they know it's an issue. I suspect they have, or will install, some kind of contamination monitoring sampling process

Other spinoffs include their attempt to get their microchannel heat exchangers into satellites (used to dump heat from the helium to hydrogen in SABRE).   They also think these might eventually be useful in civil jet engines.

The LAPCAT programme let them build some of the key HX systems.

I'll note that non-SABRE work helps them move the programme on between grants and joint projects.

I do have one specific question for the presentation.

You said the turbine is very long at 0.5m (which does sound long). Was there any indication of the diameter?

[SICA Design]

@t43562

Just to say thanks for posting the audio files. Between listening to the lecture and my wife's recounting, I now feel like I was there.

[Mutley]

The Uk Defence Secretary popped in for a visit with Reaction Engines today.
https://www.gov.uk/government/news/defence-secretary-announces-world-class-innovation-panel

"Sir Michael discussed the innovative collaboration between Reaction Engines, the MOD, and suppliers while touring the cutting-edge facility. "

[JCRM]

Mark Thomas explains REL are transitioning from research to development, and aim to be an engine manufacturer, it's for others to choose what to build using the engine on Radio4's The Bottom Line
He also indicates there are other uses for the heat exchangers.

[RanulfC]

On the "lensing" concept IIRC wasn't something similar used for astronomy at one point? Using the thermal bloom of a laser to allow precision photography as I recall. This would then be doing much the same in the opposite, (thinner to thicker rather than thicker to thinner) direction.

Randy

[john smith 19]

On the "lensing" concept IIRC wasn't something similar used for astronomy at one point? Using the thermal bloom of a laser to allow precision photography as I recall. This would then be doing much the same in the opposite, (thinner to thicker rather than thicker to thinner) direction.

Randy

It rings a dim bell from SDI. Something about a spinning hot cylinder acting as an "anti lens" or concave lens.

I smell "grant bait" being prepared. 

[lkm]

So listening to the bit about electric power production made me wonder about the potential for hybrid electric propulsion. If a distributed electric propulsion element could be integrated  with the SABRE hypersonic platform it might improve takeoff noise and thrust and allow improved subsonic efficiency.
    It occurred to me that the SABRE cycle would integrate well with a a solid oxide fuel cell given that it produces high temperature hydrogen in the right temperature range and that it has excess hydrogen at points in the cycle and that the cryogenic hydrogen would be available to cool superconducting motors.

A hypersonic platform that could loiter efficiently at subsonic speeds might be useful, or indeed one that could takeoff quietly and fly efficiently over land.

The question I guess is could distributed motors be integrated in such a way that they can be protected at hypersonic speeds.