The Reaction Engines Skylon Master Thread (1)

[Tass]

Two companies looking at a winged launch vehicle? Assuming you're not talking about Virgin Galactic, who's the 2nd?

Possibly Bristol Spaceplanes?

http://www.bristolspaceplanes.com/

Since sentence from their site caught me eye:

[Spacecap] uses proven materials and existing engines.

I'll bet that last bit is put there specifically to distinguish them from REL.

[grondilu]

but Alan Bond hopes this Skylon design is but version 1 of a whole new fleet of space-planes. Here's to hoping the Jumbo-Skylon and Jumbo-A2 style craft are flying before I croak it.

Did he actually express such a wish?   From what I saw on the RE website, Skylon would be the main tool of some already quite ambitious projects, including the Troy Mars Mission:

[Kharkov]

Did he actually express such a wish?   From what I saw on the RE website, Skylon would be the main tool of some already quite ambitious projects, including the Troy Mars Mission:

Just for the record, REL have said on many occasions that they have absolutely zero intention of doing the Troy program or building the necessary base station. Those things were just thought experiments that allowed them to define what Skylon needed to be able to do.

Skylon, once it flies (I'm optimistic), will be the key to a whole range of large-scale space projects, I'm sure but REL will have nothing to do with them.

Oh, and Bristol Spaceplanes? No news updates for 2 years, nothing pops up in a cursory search besides their webpage - I, personally, would discount them. Ideas only.

[Elmar Moelzer]

Possibly Bristol Spaceplanes?

They are still around? I think I first saw their concept floating around 15 years ago, or so...

[ArbitraryConstant]

Ok, but according to REL:

http://www.reactionengines.co.uk/sabre_howworks.html

"This approach enables SABRE-powered vehicles to save carrying over 250 tons of on-board oxidant on their way to orbit."

Even with my limited knowledge, it's clear that 250 tons is quite a lot of savings and clearly enough to compensate for all the additional paraphenalia

That's not clear to me at all. What's 250 tons of LOX cost? $60k?

[Hempsell]

As for runway lengths, perhaps Mark Hempsell, should he return, or someone else would care to speculate on the takeoff run of a (prototype?) Skylon with... oh, let's say a 50% liquid hydrogen load & nothing in the cargo bay.

For that matter, does anyone know how the Expansion/Deflection nozzle program is going?

Without liquid oxygen we currently believe Skylon would be able to use sub-3 km runways without special strengthing, so many exisiting airfields could be used if there was a way to get the hydrogen fuel onboard. And of course environmental and certification issues were resolved

The E/D nozzle programme is still on going and new test engines are in development.

[Hempsell]

That's not clear to me at all. What's 250 tons of LOX cost? $60k?

It "costs" over 15 tonnes additional tank and structure mass.  Opps! there goes the payload.

[Elmar Moelzer]

It "costs" over 15 tonnes additional tank and structure mass.  Opps! there goes the payload.

How much of those additional tank and structure mass could be saved by not having air breathing engines and staying in the atmosphere (and thus exposed to drag) longer so that these air breathing engines get enough oxygen to save those 250 tons of LOX?
Dont get me wrong, I still think that the equation comes out in favor of REL, but it comes at an enormous development cost.

[ArbitraryConstant]

It "costs" over 15 tonnes additional tank and structure mass.

Does it? LOX is quite dense and removes the need for intakes.

[BobCarver]

Not according to Alan Bond in The Three Rocketeers:

Watching the video, I still cant see how the Skylon will scale to put larger payloads into orbit. The F9 can be scaled to the falcon heavy. You cant cluster several Skylons... That is what I was referring to.

Bond also said somewhere (might have been the same video) that they were very conservative in their design and they expect to be able to advance the design in the future.

[BobCarver]

Richard Varvill in http://www.flightglobal.com/news/articles/spaceplane-air-cooling-technology-could-revolutionise-aero-engines-379772/

While the company's focus will be on its SABRE concept, Reaction Engines believes its cooling technology, which transfers heat from the air to tanked liquid hydrogen fuel by running it over a huge network of 1mm tubing, could augment a "standard" aero gas turbine in two ways.

Reaction Engines technical director Richard Varvill says a SABRE-style heat exchanger could feed cool air to compressor blades. In current gas turbines, the hot-section blades are running at temperatures above the melting point of the metals they are made from, and have to be cooled by pumping less-hot air through internal holes, the formation of which greatly complicates blade manufacture. Better cooling with colder air may permit even hotter combustion.

Another technique would be to use a heat exchanger to take heat from the exhaust and feed it back into the combustion chamber, thereby getting work from energy that would otherwise be wasted.

Varvill reckons these two approaches could slash fuel burn by 5-10%, a massive improvement. As Varvill notes, waste-heat recuperation is widely used in power station gas turbines, where weight and space considerations clearly do not apply as they do in aircraft. Indeed, recuperation is used in aero-derivative gas turbines, including Rolls-Royce's WR-21, a 25MW unit widely used in ships and derived from the RB211, the first three-spool engine which led to the Trent family.

None of this will happen quickly for aircraft, stresses Varvill, as it would require a new engine architecture rather than any bolt-on approach. But, he notes, aero engine makers have not abandoned hope of bringing in recuperation at some point.

[Elmar Moelzer]

Bond also said somewhere (might have been the same video) that they were very conservative in their design and they expect to be able to advance the design in the future.

Yeah, sure they can advance the design, but that does not mean easily scalable like going from an F9 to a FH which increased payload by a factor of 5 or more.

[flymetothemoon]

Bond also said somewhere (might have been the same video) that they were very conservative in their design and they expect to be able to advance the design in the future.

Yeah, sure they can advance the design, but that does not mean easily scalable like going from an F9 to a FH which increased payload by a factor of 5 or more.

He does somewhere compare Skylon to something like the DC-3 (1936), ushering in a new age of consumer travel. That Skylon could usher in the age of the Spaceplane.

The point being not many may have predicted how quickly we would have moved from DC-3 to Jumbo (1970) - only 34 years.

[Elmar Moelzer]

The point being not many may have predicted how quickly we would have moved from DC-3 to Jumbo (1970) - only 34 years.

That is true, but I am not sure these two can be so easily compared.

All I am saying is that if REL can do it better and cheaper than SpaceX can, more power to them! That does not mean that Musk would be totally wrong to have reservations about the concept. All I am saying that these are two different philosophies and it is too early to say which one will come out as a winner. They both have the right to try their own approach and to promote it, if needed.

[john smith 19]

Possibly Bristol Spaceplanes?

They are still around? I think I first saw their concept floating around 15 years ago, or so...

and REL was founded in 1989. The core hardware of their concept dates from 1958.

[Elmar Moelzer]

and REL was founded in 1989. The core hardware of their concept dates from 1958.

Not saying that this is a bad thing. Was just surprised that they were still there. So many have come and gone in the past 15 years.

[RanulfC]

Richard Varvill in http://www.flightglobal.com/news/articles/spaceplane-air-cooling-technology-could-revolutionise-aero-engines-379772/

While the company's focus will be on its SABRE concept, Reaction Engines believes its cooling technology, which transfers heat from the air to tanked liquid hydrogen fuel by running it over a huge network of 1mm tubing, could augment a "standard" aero gas turbine in two ways.

Reaction Engines technical director Richard Varvill says a SABRE-style heat exchanger could feed cool air to compressor blades. In current gas turbines, the hot-section blades are running at temperatures above the melting point of the metals they are made from, and have to be cooled by pumping less-hot air through internal holes, the formation of which greatly complicates blade manufacture. Better cooling with colder air may permit even hotter combustion.

Another technique would be to use a heat exchanger to take heat from the exhaust and feed it back into the combustion chamber, thereby getting work from energy that would otherwise be wasted.

Varvill reckons these two approaches could slash fuel burn by 5-10%, a massive improvement. As Varvill notes, waste-heat recuperation is widely used in power station gas turbines, where weight and space considerations clearly do not apply as they do in aircraft. Indeed, recuperation is used in aero-derivative gas turbines, including Rolls-Royce's WR-21, a 25MW unit widely used in ships and derived from the RB211, the first three-spool engine which led to the Trent family.

None of this will happen quickly for aircraft, stresses Varvill, as it would require a new engine architecture rather than any bolt-on approach. But, he notes, aero engine makers have not abandoned hope of bringing in recuperation at some point.

Not exactly following where he's going here, cooling the intake air isn't going to "help" the combustion process all that much in fact it will make it less efficent overall. Which would pretty much REQUIRE the ability to re-add the combustion heat prior to the air coming into the combustion chamber. So ... More equioment for less performance???

IF the engines (as in standard jet engines) were running on hydrogen then you could circulate the liquid hydrogen or even "cold" gas hydrogen through the turbine blades before its fed into the combustion chamber but simply cooling the incoming air isn't going to get you any benifit down-stream of the combustion chamber.

Where you WANT to cool the incoming air is at high Mach and Hypersonic speeds to protect the FAN blades and to keep the combustion temperature within the tolerances of the turbine blades but that is definatly NOT "standard" aircraft engines we're talking about.

I'm getting the feeling here that they are "stretching" to try and make "points" here for the technology which to me doesn't exactly give me a "warm-fuzzy" feeling that they have actually thought about the technology outside of the single-use of the SABRE engine.
I am and will continue to be quite impressed with the work that RE is doing and where they are going with it, but the various "claims" of this being "ground-breaking" and "paradigm-shifting" technology just are not being supported and I think they might want to take a step back and review the idea of "selling" it as such.

Frankly? All the stuff RE has done still has not reached the TRL of the Supercharged-Ejector-Ram-Jet (SERJ) engine which was ready for flight testing in the mid-60s. And the "problem" area remains the same for the SABRE as the SERJ; Flight testing is going to be very expensive and getting funding and support is not going to be at all easy. SABRE just like the SERJ is going to require a flight test vehicle cabable of all-aspect runway-to-hypersonic and back again flight regime and my "read" is that the proposed "Nacelle-Test-Vehicle" is going to be very much less than that.

Randy

[john smith 19]

It "costs" over 15 tonnes additional tank and structure mass.  Opps! there goes the payload.

How much of those additional tank and structure mass could be saved by not having air breathing engines and staying in the atmosphere (and thus exposed to drag) longer so that these air breathing engines get enough oxygen to save those 250 tons of LOX?
Dont get me wrong, I still think that the equation comes out in favor of REL, but it comes at an enormous development cost.

Well you should factor in a few things. A good LH2/LO2 engine has a SL T/W of about 59:1.  Nacelles typically double the engine weight (from SR71 work) and a typical aircraft aircraft thrust is about 1/3 to 1/4 its GTOW.  VTOL SSTO normally targets a 1% payload of GTOW.

Bottom line what you save on nacelle weight you loose on engine mass and oxidizer growth.
REL made three key discoveries modelling Skylon. not liquifying the airflow and not trying to find clever uses for the discarded GH2 coolant were the first. The last was not trying to fly to orbit entirely on air breathing. When it's no longer a good idea switch to rocket mode. The wings nullify the gravity losses but that 's not a good enough reason to try to stay air breathing longer.

[Elmar Moelzer]

Well you should factor in a few things. A good LH2/LO2 engine has a SL T/W of about 59:1.  Nacelles typically double the engine weight (from SR71 work) and a typical aircraft aircraft thrust is about 1/3 to 1/4 its GTOW.  VTOL SSTO normally targets a 1% payload of GTOW.
Bottom line what you save on nacelle weight you loose on engine mass and oxidizer growth.
REL made three key discoveries modelling Skylon. not liquifying the airflow and not trying to find clever uses for the discarded GH2 coolant were the first. The last was not trying to fly to orbit entirely on air breathing. When it's no longer a good idea switch to rocket mode. The wings nullify the gravity losses but that 's not a good enough reason to try to stay air breathing longer.

Which was my point. You loose some, you win some elsewhere. The differences between the two ideas wont be that large in the end. REL might have some technical advantages, but at a very high development cost.

[93143]

The differences between the two ideas wont be that large in the end.

You're handwaving.  My math (based on REL's math) seems to say otherwise.  I'm seeing a payload that's twice what an all-rocket SSTO can get as a fraction of dry mass, or four times as high as a fraction of GTOW, with correspondingly less sensitivity to structural mass growth and engine underperformance.

Also, it's "lose", not "loose".  This is an extremely common error, but it is an error.