Author Topic: The Reaction Engines Skylon/SABRE Master Thread (7)  (Read 349388 times)

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 10357
  • Everyplaceelse
  • Liked: 2436
  • Likes Given: 13612
Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #780 on: 02/11/2023 12:48 pm »

I think it's in the ballpark of 140kg based the numbers we have access to, but it depends on how this changes engine performance.
This is only necessary for about 5 minutes above mach 4 so the H2 coming out of the high temp He/H heat exchanger has already reach the temp limit of the precooler, as those numbers are thermodynamically linked so injected into the airstream it couldn't lower the average temperature to within the materials limit.
So not too big a mass to retain after takeoff.
Promising, but not home yet.  :)
Key question how much (in terms of mass) H2 is needed to carry out this function at this stage of the flight?
I'm not asking for the answer (I don't know it) but if it's > 140Kg then it's looking like a net win. More so if  you can reduce the size (and hence mass) of one of those HX's, and if it's worthwhile resizing the H2 tank and ultimately the vehicle itself, or if the simple answer is just not fill it up as much. :(

However then you need to consider the cost of the additional plumbing (and what pressure it will operate at).

You've already got the water tank. Where it's located could make quite a difference to complexity.  Will it need a pump or can you use the water with stored gas pressure?  Maybe the acceleration alone is enough with a pipe from the tank bottom? A pump adds more mass and can fail. Is this merely annoying or is this a Criticality 1 failure IE must never fail condition?

Personally I like the idea of eliminating stuff and using existing stuff with additional modes to it. Your idea is in keeping with that PoV. Using the water (which has to be carried anyway) but does not need to be carried to orbit to reduce the mass of a system that does need to be carried to orbit, which (hypothetically) improves the chances of system success (by reducing mass uncertainty. The HX could be too heavy otherwise). It also simplifies the HW that has to be built in house by replacing it with some bought-in components (pipework, valves etc).

Wheather or not that's a good thing depends on Reactions supplier costs for those sorts of components.  :(  Building inhouse means the costs are under your control. The HX is bigger, the H2 tank is bigger and so on.

Once again it's all about wheather the benefits are benefit enough to make the complexity a good trade.  :(

But I do like the idea.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¨cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline lkm

  • Full Member
  • ****
  • Posts: 541
  • Liked: 117
  • Likes Given: 1
Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #781 on: 02/11/2023 02:10 pm »

I think it's in the ballpark of 140kg based the numbers we have access to, but it depends on how this changes engine performance.
This is only necessary for about 5 minutes above mach 4 so the H2 coming out of the high temp He/H heat exchanger has already reach the temp limit of the precooler, as those numbers are thermodynamically linked so injected into the airstream it couldn't lower the average temperature to within the materials limit.
So not too big a mass to retain after takeoff.
Promising, but not home yet.  :)
Key question how much (in terms of mass) H2 is needed to carry out this function at this stage of the flight?
I'm not asking for the answer (I don't know it) but if it's > 140Kg then it's looking like a net win. More so if  you can reduce the size (and hence mass) of one of those HX's, and if it's worthwhile resizing the H2 tank and ultimately the vehicle itself, or if the simple answer is just not fill it up as much. :(

However then you need to consider the cost of the additional plumbing (and what pressure it will operate at).

You've already got the water tank. Where it's located could make quite a difference to complexity.  Will it need a pump or can you use the water with stored gas pressure?  Maybe the acceleration alone is enough with a pipe from the tank bottom? A pump adds more mass and can fail. Is this merely annoying or is this a Criticality 1 failure IE must never fail condition?

Personally I like the idea of eliminating stuff and using existing stuff with additional modes to it. Your idea is in keeping with that PoV. Using the water (which has to be carried anyway) but does not need to be carried to orbit to reduce the mass of a system that does need to be carried to orbit, which (hypothetically) improves the chances of system success (by reducing mass uncertainty. The HX could be too heavy otherwise). It also simplifies the HW that has to be built in house by replacing it with some bought-in components (pipework, valves etc).

Wheather or not that's a good thing depends on Reactions supplier costs for those sorts of components.  :(  Building inhouse means the costs are under your control. The HX is bigger, the H2 tank is bigger and so on.

Once again it's all about wheather the benefits are benefit enough to make the complexity a good trade.  :(

But I do like the idea.

Well if you look at a chart of the engine Vex you can seen it climb to a peak at mach 3 as the preburner has to do less work and wastes less fuel  and then fall as the cycle switches the helium flow so that the high temperature precooler no longer is running at a matched capacity ratio. I'm pretty sure that the patent says that happens then, at mach 2 they turn on the low temp precooler and mach 3 they turn on the high temp precooler. I'm just interpreting what I'm seeing there but intuitively the engine should be at it's most efficient at the top end of it's cycle and clearly isn't.

Offline lkm

  • Full Member
  • ****
  • Posts: 541
  • Liked: 117
  • Likes Given: 1
Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #782 on: 02/11/2023 09:10 pm »
Thinking a bit more about it, the SABRE 4 cycle we know about wouldn't even need to be altered for their mipcc system to be included, as it it's just a matter of the eliminating the switch to mode 3. It seems not improbable that a SABRE 4 engine would still include a frost control system to prevent low speed icing from a sub zero air stream anyway so the delivery mechanism might not even need to be added.
Given the water needs to be emptied rapidly onto the breaks anyway  there must already be a pump, so the only extra mass is the plumbing from the central tanks to the engines and the mass of water you are retaining.
 

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 10357
  • Everyplaceelse
  • Liked: 2436
  • Likes Given: 13612
Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #783 on: 02/12/2023 07:12 am »
Given the water needs to be emptied rapidly onto the breaks anyway  there must already be a pump, so the only extra mass is the plumbing from the central tanks to the engines and the mass of water you are retaining.
I don't have the time for the rest of  your two posts now but I can say that the plan for the brakes on Skylon was a pyro system. Such systems are zero maintenance and fast acting. That was about as detailed as it got. I'm picturing something like a car air-bag system. AIUI although some (Volvo?) use small high pressure tanks (which can be tricky for rescue workers to deal with in a crash) most use an azide based compound that mostly produces water and nitrogen. The gas would come from a gas generator chamber and push the water directly or push a piston to expel it.

No pump required. For routine use adapting this system would imply routine replacement of pyro ignitors, which have limited suppliers, longish lead times and are not cheap.  :( At that point I'd guess they'd be thinking about some kind of pump.
MCT ITS BFR SS. The worlds first Methane fueled FFSC engined CFRP SS structure A380 sized aerospaceplane tail sitter capable of Earth & Mars atmospheric flight.First flight to Mars by end of 2022 TBC. T&C apply. Trust nothing. Run your own #s "Extraordinary claims require extraordinary proof" R. Simberg."Competitve" means cheaper ¨cheap SCramjet proposed 1956. First +ve thrust 2004. US R&D spend to date > $10Bn. #deployed designs. Zero.

Offline FutureSpaceTourist

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 48463
  • UK
    • Plan 28
  • Liked: 82196
  • Likes Given: 37085
Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #784 on: 02/16/2023 03:32 pm »
https://twitter.com/reactionengines/status/1626250265828507648

Quote
Itís been 2 months since our FCT program, and we're still reeling from the success! Another outstanding performance of our heat exchanger technology, achieving 10 MW of heat transfer. This further proves its credibility as a key component of future high-speed propulsion systems.
« Last Edit: 02/16/2023 03:33 pm by FutureSpaceTourist »

Offline JCRM

  • Full Member
  • ****
  • Posts: 533
  • Great Britain
  • Liked: 321
  • Likes Given: 456
Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #785 on: 02/17/2023 09:50 am »
Curiosity had me locate the first thread for RE on this forum. It is 13 years old now. RE seems farther away from flying anything now than they did back then.
Really?

To me, they seem much closer to a working engine than they did then

Offline JCRM

  • Full Member
  • ****
  • Posts: 533
  • Great Britain
  • Liked: 321
  • Likes Given: 456
Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #786 on: 02/17/2023 10:15 am »

My thinking went like this.


So this was my thought. Skylon is a very large aircraft, could it successfully trade an increased fuel density and lower Isp for the reduced dry mass and reduced drag of a smaller vehicle and come out ahead?

|

Probably not.

Ammonia isn't a big enough heat sink for the SABRE cycle

Also, mmonia weighs 5 times as much as Hydrogen. You would need bigger wings for the same payload

Even hydrogen is too heavy for the Skylon design --  the SH body is shortened


Just another thought about the patents.
Given a Skylon takeoff with a 1mt of water for brake cooling could it make performance sense to retain some for mass injection allowing a matched capacity ratio within the engine at high mach and a more efficient cycle?

Unlikely. you need 8 tonnes of water to replace 1 tonne of hydrogen.

Offline lkm

  • Full Member
  • ****
  • Posts: 541
  • Liked: 117
  • Likes Given: 1
Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #787 on: 02/23/2023 08:51 pm »

My thinking went like this.


So this was my thought. Skylon is a very large aircraft, could it successfully trade an increased fuel density and lower Isp for the reduced dry mass and reduced drag of a smaller vehicle and come out ahead?

|

Probably not.

Ammonia isn't a big enough heat sink for the SABRE cycle

Also, mmonia weighs 5 times as much as Hydrogen. You would need bigger wings for the same payload

Even hydrogen is too heavy for the Skylon design --  the SH body is shortened

Well, putting aside that we were discussing this because RE has a patent on a high mach precooled ammonia engine cycle, if you do the basic math an ammonia fueled SABRE 4 cycle would actually run fuel lean. At a capacity ratio of 2:1 it would have a Air/Fuel ratio of over 9:1 while a stoichiometric ratio would be 6.7:1. But that's without the endothermic cooling of cracking so it could be even leaner.

In the first order it would be a trade of fuselage mass for fuel mass and perhaps wing mass but a smaller fuselage would also have lower drag and so without actual trajectory modelling with the skylon mass model it's hard to say if it would need bigger wings for the same payload and if the increased wing size cancelled out any gains. Beyond this is the possible issue of plume impingement, a shorter fuselage with wider wings would reduce the length of time the rear would have to withstand any thermal effects of rocket plume impingement and possibly reduce the amount of mitigation required.

Just another thought about the patents.
Given a Skylon takeoff with a 1mt of water for brake cooling could it make performance sense to retain some for mass injection allowing a matched capacity ratio within the engine at high mach and a more efficient cycle?

Unlikely. you need 8 tonnes of water to replace 1 tonne of hydrogen.


Except the water isn't exactly replacing the hydrogen, the hydrogen is still the heat sink. The water is just making the hot air cooler, denser and more thermally conductive so the same energy contained in it can be extracted by the precooler more efficiently. The only energy lost from the hydrogen is that contained in the temperature difference between the exit temperature of the precooler and the initial temperature of the water. The mass comparison isn't between the mass of water or hydrogen but between the mass of water and calculated gains of a more efficient engine cycle.
Beyond that there is the possibility to use MIPCC to expand the SABRE operational range beyond mach 5.5 a bit. I recall that RE considered that momentum drag made the gains diminishing much past this speed but I don't know where that line is actually crossed.
 

Offline JCRM

  • Full Member
  • ****
  • Posts: 533
  • Great Britain
  • Liked: 321
  • Likes Given: 456
Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #788 on: 03/01/2023 03:33 pm »


Well, putting aside that we were discussing this because RE has a patent on a high mach precooled ammonia engine cycle,

It doesn't, at least not if you're talking about GB2608643A

It has a patent on a thermally integrated engine that partially cracks ammonia to produce a fuel mixture that burns "just like" jet fuel

Quote
if you do the basic math an ammonia fueled SABRE 4 cycle would actually run fuel lean.
I'd like to see your maths.

Does it account for ammonia weighting 18 times hydrogen per mole, and that the majority of the cooling would be gaseous ammonia? So for the same cooling the amount of fuel  is around an order of magnitude higher for ammonia.

Does it account for an engine running leaner needing more air, which needs to be cooled?

my shaky maths suggests that the endothermic reaction to crack ammonia is roughly two degrees temperature rise in hydrogen - more than offset by the 180 degrees difference in the melting points of the two cryogenic liquids


Quote
In the first order it would be a trade of fuselage mass for fuel mass and perhaps wing mass but a smaller fuselage would also have lower drag
GTOW is dominated by mass of the fuel. By ISP, one needs 50% more ammonia by weight than hydrogen. even if you eliminated the structural mass one would need bigger wings.

Body drag, excluding the wings, is dominated by the cross-section. Skylon's cross section is dictated by the payload. A hypothetical ammonia Skylon would be shorter, and therefore more draggy than a hydrogen Skyon. It would need even more fuel, and therefore even bigger wings fuel.

simplifying wing drag to just the lift/drag ratio, by ISP ammonia is heavier, so it will need more lift, so they will create more drag. 



Just another thought about the patents.
Given a Skylon takeoff with a 1mt of water for brake cooling could it make performance sense to retain some for mass injection allowing a matched capacity ratio within the engine at high mach and a more efficient cycle?

Unlikely. you need 8 tonnes of water to replace 1 tonne of hydrogen.


Except the water isn't exactly replacing the hydrogen, the hydrogen is still the heat sink. The water is just making the hot air cooler, denser and more thermally conductive so the same energy contained in it can be extracted by the precooler more efficiently.
The primary reason for using "too much" hydrogen was for cooling. if hydrogen needs to provide the same amount of cooling, where's the saving?

« Last Edit: 03/02/2023 02:53 pm by JCRM »

Offline JCRM

  • Full Member
  • ****
  • Posts: 533
  • Great Britain
  • Liked: 321
  • Likes Given: 456
Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #789 on: 03/04/2023 09:49 am »
I'm very disappointed (but not altogether surprised) to hear that Virgin's failed launch from Newquay is causing some politicians to talk about reducing space funding.

Also disappointed (but not altogether surprised) to hear that working with the CAA to get a launch license is a complete nightmare. I do recall saying that working with the defunct Orbital Access would be a good opportunity to get the kinks out of the system before trying to get a billion dollar SSTO off the ground


Offline JCRM

  • Full Member
  • ****
  • Posts: 533
  • Great Britain
  • Liked: 321
  • Likes Given: 456
Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #790 on: 03/23/2023 11:55 am »
A really good "from the basics" explanation of the Swallow engine here:


Offline FutureSpaceTourist

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 48463
  • UK
    • Plan 28
  • Liked: 82196
  • Likes Given: 37085
Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #791 on: 04/11/2023 10:34 am »
https://twitter.com/reactionengines/status/1645735990051368961

Quote
It is with great sadness that we announce the passing of Nigel McNair Scott, devoted father, husband, and chairman of Reaction Engines. His passion for space helped propel the company to new heights. We extend our deepest sympathies to his family and friends during this time.

Offline t43562

  • Full Member
  • **
  • Posts: 298
  • UK
  • Liked: 164
  • Likes Given: 101
Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #792 on: 04/11/2023 01:36 pm »
Sad news about Mr McNair Scott. Not much I can say.


Moving on heartlessly, I am starved of news enough to look at the job postings at REL - at least 2 related to high-speed flight (an engineer and a project manager):

https://cezanneondemand.intervieweb.it/reactionengines/jobs/engineering-project-lead-high-speed-flight-verification-and-validation-29359/en/

Quote
Engineering Project Lead Ė High Speed Flight Verification and Validation

Position

Reaction Engines is looking for a high calibre engineer to join our fast paced and exciting High Speed Flight programme. The Verification and Validation Engineering Project Lead will report into the Chief Engineer and direct a multidisciplinary team of engineers to deliver a challenging test and verification programme for a revolutionary high-Mach propulsion system.


This is a phenomenal opportunity to realise a unique system that builds on our SABRE technology.
Requirements

To be successful you will need to have:

    Sufficient engineering experience or qualified to an equivalent of degree level (in a STEM subject)
    Excellent leadership and decision-making abilities
    Experience in design, development and testing of unique systems
    Experience in leading product or technology development projects
    Demonstrable approach to interdisciplinary problem solving and design trade-offs (systems thinking)
    Strong practical mind-set and abilities

On the site I thought that the salary was not that amazing compared to the IT world and what's being asked for.  This is the problem with engineering in general! :-/ I think if I had those skills though, and if my mortgage was as paid off as it is now, I would be there almost as fast as a speeding bullet.
« Last Edit: 04/11/2023 01:41 pm by t43562 »

Offline Ravenger

  • Member
  • Posts: 43
  • Liked: 17
  • Likes Given: 4
Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #793 on: 04/18/2023 04:04 pm »
Given that ESA is having issues with Ariane 6 such that the EU is considering using US launchers, and that they're having trouble competing with SpaceX it's a shame that they never went for Skylon/Sabre as an alternative reusable launch system.

With sufficient funding it might well have been flying by now.

Oh well. I wonder if it was politics, or simply that that ESA are very much in the governmental 'old space' way of doing things and not interested in risking new concepts that caused them to pass by this opportunity. Possibly both.

Offline JCRM

  • Full Member
  • ****
  • Posts: 533
  • Great Britain
  • Liked: 321
  • Likes Given: 456
Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #794 on: 04/19/2023 08:04 am »
Given that ESA is having issues with Ariane 6 such that the EU is considering using US launchers, and that they're having trouble competing with SpaceX it's a shame that they never went for Skylon/Sabre as an alternative reusable launch system.

Demo A is an ESA program. Various work relevant to Skylon continues under FLPP.
Quote
With sufficient funding it might well have been flying by now.
or might not, and then where would ESA be? I'm fairly certain that SABRE is viable, but I wouldn't bet a continent's launch capability on it.
Quote
Oh well. I wonder if it was politics, or simply that that ESA are very much in the governmental 'old space' way of doing things and not interested in risking new concepts that caused them to pass by this opportunity. Possibly both.
ESA, like NASA isn't afraid of new concepts, they actively pursue them - unlike private companies that iterate on proven solutions.

ESA has the complication of "geographic return" which means that it's down to the uk government to fund it


Offline JCRM

  • Full Member
  • ****
  • Posts: 533
  • Great Britain
  • Liked: 321
  • Likes Given: 456

Offline t43562

  • Full Member
  • **
  • Posts: 298
  • UK
  • Liked: 164
  • Likes Given: 101

Offline t43562

  • Full Member
  • **
  • Posts: 298
  • UK
  • Liked: 164
  • Likes Given: 101

Offline JCRM

  • Full Member
  • ****
  • Posts: 533
  • Great Britain
  • Liked: 321
  • Likes Given: 456

Offline t43562

  • Full Member
  • **
  • Posts: 298
  • UK
  • Liked: 164
  • Likes Given: 101
Re: The Reaction Engines Skylon/SABRE Master Thread (7)
« Reply #799 on: 07/11/2023 11:52 am »
More about netzero rather than space applications but signs of life are always encouraging:

« Last Edit: 07/12/2023 08:41 am by t43562 »

 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
0