The Reaction Engines Skylon/SABRE Master Thread (6)

[FutureSpaceTourist]

New FT article giving overview of Skylon and SABRE etc: https://www.ft.com/content/9b1244f6-78f7-11e6-97ae-647294649b28

Nothing new that I noticed. I suspect more a marketing piece, positioning Reaction Engines for the significant funding increase that'll be needed, eg

Mr Ford [Mark Ford head of ESA propulsion] estimates the total cost of eventually putting Sabre on to the wing of a vehicle at £500m-£1bn.

“We will need investment,” says Mr Thomas [RE CEO]. “This programme will get larger and the funds required will be exponentially larger.” He hopes the technology will interest partners from outside the space sector. Its cooling concept has applications well beyond aerospace, stretching to transport, power systems and aviation.

[john smith 19]

New FT article giving overview of Skylon and SABRE etc: https://www.ft.com/content/9b1244f6-78f7-11e6-97ae-647294649b28

Nothing new that I noticed. I suspect more a marketing piece, positioning Reaction Engines for the significant funding increase that'll be needed, eg

Mr Ford [Mark Ford head of ESA propulsion] estimates the total cost of eventually putting Sabre on to the wing of a vehicle at £500m-£1bn.

“We will need investment,” says Mr Thomas [RE CEO]. “This programme will get larger and the funds required will be exponentially larger.” He hopes the technology will interest partners from outside the space sector. Its cooling concept has applications well beyond aerospace, stretching to transport, power systems and aviation.

Not a bad article, although nothing new on the technical side. It seems journalists still have trouble with the idea that SABRE does not separate O2 from air but burns all of it.

I do wish Mark Thomas had not used the word "exponential" when it came to discussing investment needs.  It's true REL has grown by orders of magnitude that's probably not a good word to use for future investors. 

[Matthew Ak43]

The image enclosed is from a presentation that Richard Varvill gave at the British Interplanetary on July 22. (from a video on the BIS website, I thoroughly recommend joining) The new bits that I wasn't aware of is that the plan is that the test engine will be put into a flight test vehicle drone (as in the pic) with a small hydrogen tank, that he compared to the Lockheed D21 drone. The vehicle would exhilarate to about mach 5 for about 2 minutes until it has expended all its fuel then come in for a dead stick landing.

Richard said he had been told that the development of this test vehicle drone would cost about £1 billion.

[Hanelyp]

It seems journalists still have trouble with the idea that SABRE does not separate O2 from air but burns all of it.

Given what would be involved in separating oxygen, you might as well use the nitrogen collected for something useful like reaction mass, at which point there's no point in separating out the oxygen.

[Kansan52]

The D21 was the first thing that came to mind seeing that picture of the test drone.

[john smith 19]

The image enclosed is from a presentation that Richard Varvill gave at the British Interplanetary on July 22. (from a video on the BIS website, I thoroughly recommend joining) The new bits that I wasn't aware of is that the plan is that the test engine will be put into a flight test vehicle drone (as in the pic) with a small hydrogen tank, that he compared to the Lockheed D21 drone. The vehicle would exhilarate to about mach 5 for about 2 minutes until it has expended all its fuel then come in for a dead stick landing.

Richard said he had been told that the development of this test vehicle drone would cost about £1 billion.

I think you  mean accelerate 

This has been mentioned in outline before but it's good to get a bit more confirmation.  with only a single engine something like the D21 layout was always the probable design and the issue was the limited LH2 storage it would have.  This is very much an X plane. Ideally it will fly most of the early ascent profile, confirming the anticipated thrust/Isp Vs speed/altitude values and including the air breathing/rocket transition.

That said £1Bn sounds quite high for a vehicle with such limited endurance. While building an airframe able to go to cM5.6 is not simple the X15 (which was designed specifically to fly long enough for the whole airframe to reach a constant temperature) first flew in 1959. Eliminating  that requirement opens up a number of structural options, ranging from straight super alloys like the X15 to testing out the structural concepts for Skylon.

[knowles2]

The image enclosed is from a presentation that Richard Varvill gave at the British Interplanetary on July 22. (from a video on the BIS website, I thoroughly recommend joining) The new bits that I wasn't aware of is that the plan is that the test engine will be put into a flight test vehicle drone (as in the pic) with a small hydrogen tank, that he compared to the Lockheed D21 drone. The vehicle would exhilarate to about mach 5 for about 2 minutes until it has expended all its fuel then come in for a dead stick landing.

Richard said he had been told that the development of this test vehicle drone would cost about £1 billion.

I think you  mean accelerate 

This has been mentioned in outline before but it's good to get a bit more confirmation.  with only a single engine something like the D21 layout was always the probable design and the issue was the limited LH2 storage it would have.  This is very much an X plane. Ideally it will fly most of the early ascent profile, confirming the anticipated thrust/Isp Vs speed/altitude values and including the air breathing/rocket transition.

That said £1Bn sounds quite high for a vehicle with such limited endurance. While building an airframe able to go to cM5.6 is not simple the X15 (which was designed specifically to fly long enough for the whole airframe to reach a constant temperature) first flew in 1959. Eliminating  that requirement opens up a number of structural options, ranging from straight super alloys like the X15 to testing out the structural concepts for Skylon.

I would have thought it make sense for them to test out as much as possible on the drone aircraft and eliminate as many of the hurdles as possible for large crafts that use this engine.


What about putting fuel pods under the wing of the drone to increase the fuel capacity? Could it also be done in a manner that would represent the nacelles on a full size craft?

[john smith 19]

I would have thought it make sense for them to test out as much as possible on the drone aircraft and eliminate as many of the hurdles as possible for large crafts that use this engine.

Within reason yes. But again it's walking a line between retiring risk for a possible  vehicle structure and still leaving significant work for the airframe maker to be responsible for.  Yes I'd like them to prove out the SiC reinforced Titanium rod space frame with the SiC reinforced glass skin but if that multiplies the cost for this vehicle then going with something more conventional (super alloys, Titanium) would be the more sensible use of available funds. When in doubt, focus on the core task.

That said I think the water cooled brakes would be applicable to any concept and TBH I could see them having a market for commercial aircraft. A system that replaces possible a tonne of brakes that have to be carried with the aircraft with a water tank that can be emptied post takeoff could save an airline a lot of money over the life of an aircraft.

What about putting fuel pods under the wing of the drone to increase the fuel capacity? Could it also be done in a manner that would represent the nacelles on a full size craft?

The D21 design is fairly well known and I think quite a lot of its aerodynamics are either available for the real thing or have been simulated in various projects.  That means it's a low risk shape to build (provided the weight distribution mimics the original), although working out where to put the LH2 tanks is going to be tricky.  I'm guessing cylinders in the wings or along the body.

IIRC  REL estimate that it would only take about a cm of 60Kg/m^3 PU foam to keep the foam outer surface temp above the condensation point of water using sub cooled propellants.

Adding pods changes the aerodynamics, and in any case it's highly unlikely the drone would be scaled up to a full vehicle, which I think is likely to remain a 2 engine design.

[john smith 19]

I'm not sure how much information has been released about this planned drone but we can make some deductions.

Can't remember if the ground engines thrust was given in lbs, Kgs or KN. I think it was lbs (which is odd for a UK company). If I'm wrong please divide by 2.2 for Kg  and multiply by 4.46 to give KN.

Based on the SpaceWorks USAFRL study they seem to think that thrust needed to be 60% of GTOW, rather than the usual 30% (IIRC the Ryan Firebee II supersonic drones had engine thrust 1/2 GTOW, suggesting 60% is conservative).

If the engine thrust is 40 000 lb that gives a GTOW of about 66 000lb. Assuming REL deliver an engine with proper T/W of 14:1 that's an engine of 2857 lb. Using the water cooled brakes concept gives a weight of less than 990 lb (that's 1.5% of GTOW but the historic rule of thumb relates brake weight to gross landing weight).

That leave 62153 lb for the whole structure, tankage and propellant (assuming you'll need LOX for a few seconds past the air breathing/rocket transition). My last data point is that most fluid tanks are 1% of the weight of the fluid they hold but LH2 tanks are somewhere between 2 and 10% of their fluid mass.

The challenge is can you build a vehicle to hold enough propellant to fly the full trajectory within this weight. Obviously if the idea that thrust has to be 60%of GTOW is reduced that gives you more mass to play with but AFAIK that's what the USAF study went with so probably best to trying fitting within that constraint first.

[EDIT. BTW it looks like the REL website is offline.  Does anyone know anything about this? ]

[momerathe]

So in the third image, it mentions a constant inlet temp. of 400k. That implies it's the SABRE 4 cycle, right?

[Mutley]

[EDIT. BTW it looks like the REL website is offline.  Does anyone know anything about this? ]

The website now says they are building a new site that will be up in mid November

[Star One]

[EDIT. BTW it looks like the REL website is offline.  Does anyone know anything about this? ]

The website now says they are building a new site that will be up in mid November

Perhaps we can expect some significant announcement then to coincide?

[Baskii]

There are some interesting renders on the Reaction Engines Twitter feed (attached).
The first one shows the 'D21' test vehicle, a Skylon, and another twin-engined vehicle.  This vehicle is also shown in the second render.  It doesn't look like the AFRL TSTO concept - could it be an intermediate test vehicle?  Apologies if you've already covered this upthread and I missed it.
I note that one render shows it with straight engine nacelles, and the other with Skylon's curved nacelles.

[Archibald]

The left model looks like a D-21 except with a different wing (the D-21 wing angled in the shape of a pear)

20 years ago NASA briefly investigated turning D-21 drones into RBCC test beds
https://www.google.fr/webhp?ie=utf-8&oe=utf-8&client=firefox-b&gfe_rd=cr&ei=1NUhWMepIoLDaNL2i6AK#q=%22D-21%22%22RBCC%22

[hkultala]

There are some interesting renders on the Reaction Engines Twitter feed (attached).
The first one shows the 'D21' test vehicle, a Skylon, and another twin-engined vehicle.  This vehicle is also shown in the second render.  It doesn't look like the AFRL TSTO concept - could it be an intermediate test vehicle?  Apologies if you've already covered this upthread and I missed it.
I note that one render shows it with straight engine nacelles, and the other with Skylon's curved nacelles.

This is originally from some university research paper. They were studying an alternative aerodynamic configuration for skylon, and doing some CFD modeling  and comparing this to the official skylon configuration.

The paper was released something like one year ago.

[Baskii]

There are some interesting renders on the Reaction Engines Twitter feed (attached).
The first one shows the 'D21' test vehicle, a Skylon, and another twin-engined vehicle.  This vehicle is also shown in the second render.  It doesn't look like the AFRL TSTO concept - could it be an intermediate test vehicle?  Apologies if you've already covered this upthread and I missed it.
I note that one render shows it with straight engine nacelles, and the other with Skylon's curved nacelles.

This is originally from some university research paper. They were studying an alternative aerodynamic configuration for skylon, and doing some CFD modeling  and comparing this to the official skylon configuration.

The paper was released something like one year ago.

Oh yes - I'd forgotten about that study.  Sorry...I guess I was getting overexcited...

[john smith 19]

So in the third image, it mentions a constant inlet temp. of 400k. That implies it's the SABRE 4 cycle, right?

Yes that compressor inlet temperature is about 127c, rather than the deeply pre cooled -150 to -200c, so SABRE 4.

[Matthew Ak43]

Richard Varville also confirmed that they are working with Sabre 4. Half the fuel consumption as you already probably know, but a much more heavier and  complex engine. I wonder if this would have been a much simpler and cheaper engine development process if they went with Sabre 3.

[dror]

From this simple diagram it looks like SABRE 4 should be able to work with different types of fuel such as LCH4, is that so?

[Asteroza]

Drop tanks for takeoff->subsonic climb seems not unreasonable, after examining the zero start takeoff test envelope. Don't forget there are carrier planes available, such as StratoLaunch's Roc, and perhaps the Virgin Galactic SS2 carrier plane, which could do an air launch to reach other test envelopes.