Author Topic: Reaction engines Flight Test Vehicle speculation  (Read 10642 times)

Offline knowles2

  • Full Member
  • *
  • Posts: 124
  • Liked: 26
  • Likes Given: 51
Re: Reaction engines Flight Test Vehicle speculation
« Reply #40 on: 05/05/2018 11:25 AM »
I wasn't sure if this should go in "Advance Concepts" or "Commercial" with the main SABRESkylon thread, but it's not meant to be a product and it' would certainly be advanced.  :)

REL have talked about the idea of a "Flight Test Vehicle" on a couple of occasions. Earlier ideas were for a scaled down Skylon, running LOX/Methane rockets while the current design, resembles the D-21 M3 reconnaissance  drone designed to launch off the back of a couple of modified SR71s in hte late 60's. then modified with a booster longer than the drone, was tested off a modified B52, before the whole project was cancelled.

However looking through the archives I located this.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20000004765.pdf
and this.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19990110312.pdf

Basically a late 90's plan to modify a couple of D-21 to demonstrate the "DRACO" Rock Based Combined Cycle engine some NASA centers were working on.  This system has multiple mode transitions in its flight trajectory and also featured a moving inlet spike to accommodate the speed changes.

In the process the second one discusses the D-21 in some detail, along with the LM Advanced Projects "Experimental Prototype" approach to cutting the development cost by about 1/3 (page 35 if you're interested).

Interestingly they reckoned you could  add a LOX tank between the fuel wing tanks and the engine duct, and they didn't think it would have thermal issues, although once you got above M3.5 the titanium skin and duct leading edge looked doubtful. Interestingly the issue around the LOX tank was not temperature related but pressurization. The D-21 was designed to operate its fuel tanks (there were 3, front, middle and back cross ways) at 1.5psi above the ambient pressure. Pressurizing the tanks to make the engine pressure fed was viewed as too dangerous.

On the upside the REL FTV is a clean sheet design with a thrust about 29x bigger than the D-21 ramjet. (Marquardt RJ43-MA-20S4) and recovery and reuse will be designed in from day one.

Beyond that we have a few data points.

The SABRE test engine is expected to have a thrust of 20 tonnes (44 000lbf) and according to the SEI study on the USAF TSTO design thrust needs to be at least 70% of GTOW, giving about 28500Kg of mass.

SABRE's T/W ratio is expected to be 14:1 so engine mass is say 1430Kg.
The D21 dry mass 5500lb vs fully loaded at 11200lb means it was 49% structure. It was stressed to withstand -2/+5g in both axial and directions normal to axial. So a lower peak acceleration should give a lighter structure.

28,500-1,430kg is a total mass of 27,070Kg. A 15% mass growth allowance means the maximum mass (structure and propellant) is 23,539Kg.

To put this in perspective 30tonnes is a small(ish) regional airliner or a large(ish) fighter aircraft.

My instinct is this layout is not a good fit to the issues around LH2 as a fuel, hence my interest in wheather it would be possible to make 2 engines and go with a "Mini Skylon" airframe.

Given the D-21 is going to be REL's FTV design to test inlet design and spike schedule what does that say about its capabilities?


My instinct is REL can go one of two ways on this.

A "bare bones" X-plane approach.
This is totally focused on flying SABRE through as much of its trajectory as possible and refining the inlet and spike performance to meet its goals. The vehicle structure is as simple as possible to do that.  Not intended to be anywhere close to deliver a substantial payload to orbit, or a 2nd stage to release.

A "Skylon risk retirement" approach.
This implements the FTV in technologies more like those planned for Skylon. IE a truss framework with appropriate levels of MLI and the SiC reinforced ceramic skin fabricated in corrugated panels.

Both options can help retire a number of operations features of a Skylon as well. EG fully automated fueling and de-fueling, although that would not be necessary for early tests. Likewise early tests could treat it as an RPV flown from a ground station, before moving to fully AGV status.

the big question would be what else  could it be used for ? What sort of things would 3rd parties like to test, and what sorts of instrumentation would they want to install to do so?
It all about funding, if REL can go for the mini skylon concept then they will because it means they go from mini to full scale pretty quickly.

But if they don't have the money for that they will knock up the cheapest vehicle they can to test their engine. Which will most likely be something that complete avoids anything use or developed in the US to avoid Itar.

Thing is they are a engine seller, they aren't interesting in building the actual craft, at least not yet, so all they need is something that proves the engines flies and at least make to sub orbit. You should be able to knock something up that does that for less than a 100 million.

Offline knowles2

  • Full Member
  • *
  • Posts: 124
  • Liked: 26
  • Likes Given: 51
Re: Reaction engines Flight Test Vehicle speculation
« Reply #41 on: 05/05/2018 11:41 AM »
Quote
BAE are the steering force now in this, their actual percentage is pretty irrelevant but itís big enough to do what they want to do. Also why do you think they are working with DARPA in the US, they only have one purpose and it sure isnít civilian.
They are working with DARPA because they are willing to pay for testing of their pre cooler in a hypersonic tunnel. They are hoping this piece of data along with the other testing going on in the UK over the next 2-3 years that will unlock serious money either from BAE/Boeing/RR or from other investment funds around the UK, they want to avoid taking as much US money as possible to avoid getting entangled in ITAR. They

An Reaction Engines is just creating the engine, they want to sale that engine to anyone that wants one, if that includes the military then so be it, they aren't fuss, as long as no this top secret, classified,can't talk to anyone about it type restrictions are place on the program. In a ideal world they would want the military and civilian companies to buy their engines to mount of their own vehicles. Just like RR does.

Offline JCRM

  • Member
  • Posts: 93
  • Great Britain
  • Liked: 45
  • Likes Given: 25
Re: Reaction engines Flight Test Vehicle speculation
« Reply #42 on: 05/05/2018 11:37 PM »
The form a test vehicle takes will depend on the requirements behind the funding.

REL worked on FSPLUK which if funded may provide a flight tested vehicle that could fly a SABRE.

But I can't see anyone funding a pure SABRE test vehicle until SABRE has been tested. BAe's initial estimates for a test vehicle was 1 billion

The Darpa funding has a potential phase 3, which covers flight testing (It also explicitly mentions dual use - civilian and military).

« Last Edit: 05/05/2018 11:39 PM by JCRM »

Offline knowles2

  • Full Member
  • *
  • Posts: 124
  • Liked: 26
  • Likes Given: 51
Re: Reaction engines Flight Test Vehicle speculation
« Reply #43 on: 05/06/2018 12:52 AM »
The form a test vehicle takes will depend on the requirements behind the funding.

REL worked on FSPLUK which if funded may provide a flight tested vehicle that could fly a SABRE.

But I can't see anyone funding a pure SABRE test vehicle until SABRE has been tested. BAe's initial estimates for a test vehicle was 1 billion

The Darpa funding has a potential phase 3, which covers flight testing (It also explicitly mentions dual use - civilian and military).
BAE works on military funding scales, if they say it will cost a billion, a non military contractor probably could so it for a fraction of that price.

The vehicle only have to be something similar to SpaceshipOne,. Which cost around a 100 million dollars, even taking inflation into account it hard to get to BAE figure of a billion quid for a demonstrator vehicle.

Offline Katana

  • Full Member
  • ***
  • Posts: 378
  • Liked: 47
  • Likes Given: 21
Re: Reaction engines Flight Test Vehicle speculation
« Reply #44 on: 05/06/2018 05:26 AM »
Two booster engines to be symmetrical like conventional rockets with strap on boosters, nothing related to X7.
Are you saying you think REL would build two flight engines or two rocket engines?
Quote from: Katana
The X7 airframe may work up to M6, but would be infeasible for rocket mode operation to M10.
I'm talking about the X7 layout which is basically the same as the M2 Firebee II drone and Hound Dog missiles.
Quote from: Katana
Even without VTOL, the vehicle need to be symmetrical in rocket mode, which exclude X7 and favors BOMARC/ SR71/ original Skylon.
There have been a number of asymmetric thrust rocket concepts, IIRC one of the NLS designs for example.

I think everyone would prefer a symmetric vehicle wheather it looked like Skylon or not. Thrust is more balanced, there are more engine placement options and you have redundancy, which is important given the new engine has unknown reliability statistics (something else flight testing will discover).

It's wheather the budget will be available to allow it.  :( The minimal assumption is there will be enough for one engine, not two, so what can you do with that one engine?

Incidentally it turns out that through the 1970's and 80's NASA ran a number of studies for such an aircraft in the 40-60 000lb range as the "High Speed" or "Hypersonic Speed" Research Aircraft, partly to try out the various possible structural concepts they had seen on a scale that would give them a realistic test of the structural issues of a large aircraft.

They reckoned you could build a baseline aircraft out of fairly conventional Aluminium with active water/glycol cooling good at least to M6.

My instinct is for a passive heat pipes to move heat, eliminating the need for pumps and the large  numbers of fluid connectors that have to stay fluid tight over a very wide range of temperatures and pressures covering the wings and fuselage. I don't think their complexity was ever really addressed and it's a non trivial problem to solve.
Why you think REL can't afford to build two engines , for a test vehicle?

Building several more copies per batch only add minor cost to R&D. In fact they are really needed for backup, in case of damaging.

Solving the asymmetrical thrust problem needs additional procedures, which becomes really expensive.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 7581
  • Everyplaceelse
  • Liked: 1172
  • Likes Given: 7832
Re: Reaction engines Flight Test Vehicle speculation
« Reply #45 on: 05/06/2018 06:08 AM »
Why you think REL can't afford to build two engines , for a test vehicle?

Building several more copies per batch only add minor cost to R&D. In fact they are really needed for backup, in case of damaging.

Solving the asymmetrical thrust problem needs additional procedures, which becomes really expensive.
Because the last REL presentation I've seen showed a test vehicle looking like a D-21 drone, whereas earlier ones (designed to fine tune the inlet design) was more Skylon like.  Historical learning curves for aircraft production are that when you double the number of items you drop the cost by 15%.

That said I would expect the precooler would be a 3rd generation unit ( the test stand ones in Colorado and the TF1 stand being the first two generations). The rest would be the second full  iteration of the design.

Pending an announcement from REL the conservative view is they are going to build one flight weight engine to test fly.  :(
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 7581
  • Everyplaceelse
  • Liked: 1172
  • Likes Given: 7832
Re: Reaction engines Flight Test Vehicle speculation
« Reply #46 on: 05/06/2018 06:24 AM »
BAE works on military funding scales, if they say it will cost a billion, a non military contractor probably could so it for a fraction of that price.

The vehicle only have to be something similar to SpaceshipOne,. Which cost around a 100 million dollars, even taking inflation into account it hard to get to BAE figure of a billion quid for a demonstrator vehicle.
This is where it gets complicated. BAe is an investor (and having  an airframe mfg already was a late changed condition of the UK govt grant contract to REL)

TBH I don't believe there are any existing airframe mfgs with experience of the materials REL have baselined for the Skylon airframe, so the fact that BAe is a large military contractor is not a plus point. It basically means they are great at the paperwork of a government contract, like the F35.

No doubt the UK govt were persuaded that having someone who could design such a vehicle would "reduce risk" in their investment.

Personally I would have preferred someone who still built commercial jet aircraft (Bombardier in Belfast for example), but UK "industrial" policy (much like US DoD policy) mashed them all together (along with small arms, artillery, submarines, torpedoes and armored fighting vehicle makers) into BAe.  :(

[EDIT For those curious of what what some of the issue of a hypersonic vehicle are this is a NASA roundup paper of some of the issues (and ways to handle them) from 1968. Note a structural fraction of 25% for hypersonic aircraft was viewed as achievable without the use of a truss structure.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19680017975.pdf

What has changed? Well FSW for metal joining, much cheaper  high resolution NDE of parts. Wider experience of diffusion bonding. Maximum operating temperature for some plastics exceeding 250c and some up to 350c. ]
« Last Edit: 05/06/2018 07:56 PM by john smith 19 »
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 7581
  • Everyplaceelse
  • Liked: 1172
  • Likes Given: 7832
Re: Reaction engines Flight Test Vehicle speculation
« Reply #47 on: 05/21/2018 09:20 AM »
One problem area for space planes is the hydraulic system. Servicing the one on the Shuttle was a major PITA and needed a dedicated pump to stop it freezing.

All electric actuation looks to be less troublesome, given the wide thermal and pressure operating ranges the control system needs to operate over.  It is already standard on the Vega solid rocket and seems to have worked fine for main nozzle TVC, which calls for a fairly high thrust, high speed (but low angle) drive system. Likewise the X37b seems to be all electric, including all the landing gear associated equipment.

With this in mind I found a British PhD thesis  sponsored by landing gear mfg Messier Dowty (part of Saffran) on health monitoring for electrically actuated landing gear.

https://www.research.manchester.ac.uk/portal/files/54520238/FULL_TEXT.PDF

It mentions a £10m programme funded by the UK Dept of Trade & Industry called ELGEAR targetting this specific area.

Here is a presentation by Messier Dowty's parent company Saffran on the idea of electric landing gear, including brakes and steering.
http://www.icas.org/media/pdf/Workshops/2013/ICAS%20-%20Recent%20Advances%20and%20Future%20Electrical%20Landing%20Gear%20Systems%20Publish.pdf

This is paper from China on some of the detailed issues around this task and some of the type of electric motors that could be used.

http://www.icas.org/ICAS_ARCHIVE/ICAS2012/PAPERS/109.PDF

IMHO it would be easier to route electric cabling and cool EMA's than develop high temperature hydraulic actuators, their associated fluid and pump package. 
« Last Edit: 05/21/2018 10:04 AM by john smith 19 »
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 7581
  • Everyplaceelse
  • Liked: 1172
  • Likes Given: 7832
Re: Reaction engines Flight Test Vehicle speculation
« Reply #48 on: 07/16/2018 08:35 PM »
Why you think REL can't afford to build two engines , for a test vehicle?

Building several more copies per batch only add minor cost to R&D. In fact they are really needed for backup, in case of damaging.

Solving the asymmetrical thrust problem needs additional procedures, which becomes really expensive.
I'd agree.  A two engine vehicle just seems much easier to deal with, in terms of air flow and thrust and CoG shifts.

But the latest renderings show a single engine vehicle.
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline knowles2

  • Full Member
  • *
  • Posts: 124
  • Liked: 26
  • Likes Given: 51
Re: Reaction engines Flight Test Vehicle speculation
« Reply #49 on: 07/24/2018 02:29 PM »
The UK has just announce it building a new fighter the tempest.

I think Reaction Engine can squeeze a bit of money out of this program. It could provide a continuous revenue stream by getting rolls royce to adopt it pre coolers for the fighter engine.

 Reaction Engine do claim they offer a lot of advantages,  https://www.reactionengines.co.uk/sabre/pre-cooled-turbojet.

This is Roll Royce video on the new engine
Could the guy fit any more buzz words in this video! Improve thermal management is one of Reaction Engine claims through.
 
Also nearly all the partners involve in Tempest are now also actively involved in Reaction Engine.

I'm taking a little guess here but to be a truly next gen aircraft the Tempest will be base on a all electrical system. incorporate electrical landing gears and replace most of hydraulic systems with electrical systems, which should produce plenty of transferable knowledge to incorporate those technologies into skylon. 

Also could reaction engines take advantage of Project Magma https://www.baesystems.com/en/article/first-magma-flight-trials to further lighten skylon?

Project Tempest if the UK truly wants a true 6th gen aircraft, should mature all of these technologies making them cheaper to integrate them into Skylon and produce a even lighter vehicle and may be even a simpler spacecraft to build as well.

Offline Star One

  • Senior Member
  • *****
  • Posts: 9642
  • UK
  • Liked: 1819
  • Likes Given: 183
Re: Reaction engines Flight Test Vehicle speculation
« Reply #50 on: 07/24/2018 03:02 PM »
The UK has just announce it building a new fighter the tempest.

I think Reaction Engine can squeeze a bit of money out of this program. It could provide a continuous revenue stream by getting rolls royce to adopt it pre coolers for the fighter engine.

 Reaction Engine do claim they offer a lot of advantages,  https://www.reactionengines.co.uk/sabre/pre-cooled-turbojet.

This is Roll Royce video on the new engine
Could the guy fit any more buzz words in this video! Improve thermal management is one of Reaction Engine claims through.
 
Also nearly all the partners involve in Tempest are now also actively involved in Reaction Engine.

I'm taking a little guess here but to be a truly next gen aircraft the Tempest will be base on a all electrical system. incorporate electrical landing gears and replace most of hydraulic systems with electrical systems, which should produce plenty of transferable knowledge to incorporate those technologies into skylon. 

Also could reaction engines take advantage of Project Magma https://www.baesystems.com/en/article/first-magma-flight-trials to further lighten skylon?

Project Tempest if the UK truly wants a true 6th gen aircraft, should mature all of these technologies making them cheaper to integrate them into Skylon and produce a even lighter vehicle and may be even a simpler spacecraft to build as well.

None of this will happen as Tempest is designed to be sixth generation on a budget. Like with the B-21 in the US the rapid capabilities office running this program is looking to use off the shelf technologies as much as possible.

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 7581
  • Everyplaceelse
  • Liked: 1172
  • Likes Given: 7832
Re: Reaction engines Flight Test Vehicle speculation
« Reply #51 on: 07/24/2018 07:15 PM »
The UK has just announce it building a new fighter the tempest.

I think Reaction Engine can squeeze a bit of money out of this program. It could provide a continuous revenue stream by getting rolls royce to adopt it pre coolers for the fighter engine.

 Reaction Engine do claim they offer a lot of advantages,  https://www.reactionengines.co.uk/sabre/pre-cooled-turbojet.


Could the guy fit any more buzz words in this video! Improve thermal management is one of Reaction Engine claims through.
Indeed. I call "House" on the Buzzword Bingo.  :)
However...
I think electric actuation is a technology that Skylon could use well and is becoming more mature. For the FTV I'm not sure if anything more than batteries would be needed (that are several decades more advanced than the ones planned for the DRACO conversion of the D-21). BTW the big points of what he was talking about are
1) Direct bonding of the magnets to the shaft, a more "unitized" construction
2) Magnets cease to work above their Curie Point, so putting those magnets deep inside the engine means magnet alloys that can operate at high (or higher) temperature.
 
Quote from: knowles2
Also nearly all the partners involve in Tempest are now also actively involved in Reaction Engine.

I'm taking a little guess here but to be a truly next gen aircraft the Tempest will be base on a all electrical system. incorporate electrical landing gears and replace most of hydraulic systems with electrical systems, which should produce plenty of transferable knowledge to incorporate those technologies into skylon. 
Quite likely.
 
Quote from: knowles2
Also could reaction engines take advantage of Project Magma https://www.baesystems.com/en/article/first-magma-flight-trials to further lighten skylon?

Project Tempest if the UK truly wants a true 6th gen aircraft, should mature all of these technologies making them cheaper to integrate them into Skylon and produce a even lighter vehicle and may be even a simpler spacecraft to build as well.
This is rather more doubtful.
"Boundary Layer Control" or "blown flaps" have been demonstrated since the 1950's. The classic example was the "Buccaneer" (probably the closest to the Douglas A4 Skyhawk).

BLC allowed the Buccaneer wing to be 50% smaller that designs with similar specs. This is attractive. OTOH it took a substantial fraction of the engine thrust to do so and of course if the engine fails the consequences are serious. OTOH the wing mass reduction is significant. The question is wheather it is significant enough? [EDIT IE does the reduced vehicle dry mass outweigh the increased risk of losing the payload if there is an engine failure? ]

Fluidic controls are even more problematical if you've already gone to electric actuators.

Where you draw the line is a very tricky question. Necessary innovation (because you can't make the design work without it) versus unnecessary innovation, that adds cost, technical risk and potential delays.



« Last Edit: 07/26/2018 07:05 AM by john smith 19 »
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Offline t43562

  • Full Member
  • *
  • Posts: 191
  • UK
  • Liked: 82
  • Likes Given: 39
Re: Reaction engines Flight Test Vehicle speculation
« Reply #52 on: 08/02/2018 01:50 AM »

Fluidic controls are even more problematical if you've already gone to electric actuators.

Where you draw the line is a very tricky question. Necessary innovation (because you can't make the design work without it) versus unnecessary innovation, that adds cost, technical risk and potential delays.

I saw Magma at the BAE Systems display at Farnborough and had a long chat with the gentleman demonstrating it.  He gave me the fluidic thrust vectoring nozzle for the previous aircraft (DEMON) to compare with the one for MAGMA which was 3D printed.

Both were made from Titanium but the DEMON one was about maybe 2KG and the MAGMA one was at most a couple of hundred grams. It was a great surprise.

I don't know about DEMON but the MAGMA one was "only" 2D and it is something that he says has potential to be included in Tempest.  It's like mouth with an (not quite) elliptical opening shape and there are openings at the top and the bottom for gas to be blown to influence the direction of flow of the exhaust.

My memory is that he said DEMON was over 100kg (140?) but that MAGMA is 20kg empty.   This is partly because they worked out how to supply air from the thrust engine instead of having 2 but perhaps mostly because of the carbon airframe.

MAGMA has conventional controls which are used to supplement the fluidics when larger forces are needed.  I think this shows they can perhaps be backups as well.

One of the big innovations in MAGMA was that they worked out that they couldn't supply more air for control but they could supply it at higher speed (supersonic) and this makes their fluidic controls much more efficient than with DEMON.

The main claim about fluidics from the MAGMA representative was that they are much lower maintenance since only a ball valve moves. The fluidic thrust vectoring is also good for this reason - meaning that whatever craft you have is much more likely to have high availability with this kind of thrust vector rather than a mechanical one.   It also pays for the vectoring system to be light because it makes CoG problems much less onerous.
 
I'm no expert but it just seemed like thrust vectoring a rocket nozzle with airflow would be a huge research project of its own and why would you want to do it for a launch vehicle?

As for replacing ailerons etc they mentioned that it got more challenging with larger aircraft but that the fact that large modern engines (as opposed to their model aircraft ones) had more compressors which might compensate.

That's all I could get - I leave you to judge if anything's applicable to SABRE-powered vehicles.



Offline john smith 19

  • Senior Member
  • *****
  • Posts: 7581
  • Everyplaceelse
  • Liked: 1172
  • Likes Given: 7832
Re: Reaction engines Flight Test Vehicle speculation
« Reply #53 on: 08/02/2018 07:19 AM »
I'm no expert but it just seemed like thrust vectoring a rocket nozzle with airflow would be a huge research project of its own and why would you want to do it for a launch vehicle?
You'd be right but this is not how it works.  The flow is run through piping to vent through the trailing edge of the wings. AIUI SABRE thrust chambers, if not the whole nacelle, will swivel.
The point is that this is a research project. I'm very doubtful that this is necessary to make the design close. Plus I'm not sure SABRE has any provision to divert any of its feed air for other purposes. If it does this could be an option. Historical designs have used similar techniques to cut wing size (which lowers drag as well as T/O mass) but it's another dynamic system that becomes a "Criticality 1" system that simply cannot fail.
Quote from: t43562
As for replacing ailerons etc they mentioned that it got more challenging with larger aircraft but that the fact that large modern engines (as opposed to their model aircraft ones) had more compressors which might compensate.

That's all I could get - I leave you to judge if anything's applicable to SABRE-powered vehicles.
Personally I think more could be done with Skylon's wing design. I suspect it is fairly basic in shape and plan. As we move toward construction I think there is room for improvement, while keeping the aerodynamics within the known SoA.

My instinct is the model for this fluidic controls stuff is the acceptance of 2 engine airlines for flight over the oceans. This took a long process of accumulating flight hours to demonstrate the new engines had the reliability to operate for the extended periods needed. It helps this technology can fly in a hybrid configuration, allowing it to accumulate flight hours without failure being catastrophic.

While the current FTV that REL have shown pictures of looks like the Man. U test vehicle I think it adds design issues both to the engine and the vehicle that aren't needed. Conventional controls should be adequate. Also the operating speed range for the FTV and Skylon are way  beyond what the bulk of vehicles fitted with this technology will operate over.  We know aerosurfaces can operate to high Mach numbers, as Buran, Shuttle and the X37b have shown. Outside the atmosphere you need thrusters anyway.
Failure to make fluidic controls work on the FTV at M3+ wouldn't mean they aren't completely viable at 0-M2+, which is pretty much what all military (and < M1 for all civil) aircraft fly at.
« Last Edit: 08/05/2018 09:47 AM by john smith 19 »
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.

Online Asteroza

  • Full Member
  • ****
  • Posts: 644
  • Liked: 83
  • Likes Given: 2
Re: Reaction engines Flight Test Vehicle speculation
« Reply #54 on: 08/05/2018 11:48 PM »
Would fluidic nozzles win versus gimbals and associated structure to accommodate gimbaling? I get a sneaking suspicion that the mass and performance trades are real murky here. For instance, is there enough bleed air from the SABRE compressor to run fluidics? On a more conventional rocket engine, would turbine exhaust work? Shades of the TAN augmented nozzle work in a sense?

For Skylon, the nacelles have a serious bend to them, trying to matching between airflow flight angle and ideal thrust angle, which is probably not insignificant in terms of drag. Could one cheat with fluidics to effectively get more of the nozzle inline with the airflow and have variable thrust angle/trim?

Offline john smith 19

  • Senior Member
  • *****
  • Posts: 7581
  • Everyplaceelse
  • Liked: 1172
  • Likes Given: 7832
Re: Reaction engines Flight Test Vehicle speculation
« Reply #55 on: 08/08/2018 09:50 PM »
Would fluidic nozzles win versus gimbals and associated structure to accommodate gimbaling? I get a sneaking suspicion that the mass and performance trades are real murky here.
And you'd be right. Multiplied by the TRL of the technology. Well understood and used many times over the last 60+ years versus (essentially) developed over the last decade with limited funding.

The hardware is not the whole story.  :( You must consider things like the design tools available to design new versions. Mature for mechanical TVC. But for fluidic, with supersonic flows? And bleeding off thrust right during take off?  That could turn a slight engine under performance into a crash (or it might not. The new tech brings greatly increased uncertainty).

Basically your swapping a well understood steering method, with equally well understood design methods, for a new approach that's have very limited hardware validation and a high risk of "Unknown unknowns" when you design and operate it over a range of at least 0-M6

The benefits, in terms of mass reduction and reliability increase by reducing the number of individual parts, would have to be huge to justify the (substantially) greater risk of using it. If they are not it's way more risk of the design not working (and over running on schedule and budget) for just too little gain.
Maybe  it can, but I'm very skeptical the case closes, in which case it would be novelty for novelty's sake, which is always a bad idea.
Quote from: Asteroza
For instance, is there enough bleed air from the SABRE compressor to run fluidics? On a more conventional rocket engine, would turbine exhaust work?
Unknown, and possible, if you can take the 3-5% of propellant diverted to the gas generator. SABRE, is more in the line of staged combustion engines, where everything that goes through the preburner ends up in the combustion chamber.
Quote from: Asteroza
Shades of the TAN augmented nozzle work in a sense?
Not really, that's way too far down stream.
Quote from: Asteroza
For Skylon, the nacelles have a serious bend to them, trying to matching between airflow flight angle and ideal thrust angle, which is probably not insignificant in terms of drag. Could one cheat with fluidics to effectively get more of the nozzle inline with the airflow and have variable thrust angle/trim?
Maybe. Estimates are that this angle was about 14Deg for SABRE 3 but SABRE IV has halved that to about 7 Deg.
BFS. The worlds first Methane fueled FFORSC engined CFRP structured A380 sized aerospaceplane tail sitter capable of flying in Earth and Mars atmospheres. BFR. The worlds biggest Methane fueled FFORSC engined CFRP structured booster for BFS. First flight to Mars by end of 2022. Forward looking statements. T&C apply. Believe no one. Run your own numbers. So, you are going to Mars to start a better life? Picture it in your mind. Now say what it is out loud.