The Reaction Engines Skylon/SABRE Master Thread (7)

[JCRM]

Slightly more on-topic (but barely) the current edition of Space Chronicle includes Alan Bond's memoir of working on the RZ20 engine. as it touches of his experience of working on LH2/LOx engines, and UK Government handling of projects it provides some background that might have influenced decisions around HOTOL/REL/Skylon

[john smith 19]

Slightly more on-topic (but barely) the current edition of Space Chronicle includes Alan Bond's memoir of working on the RZ20 engine. as it touches of his experience of working on LH2/LOx engines, and UK Government handling of projects it provides some background that might have influenced decisions around HOTOL/REL/Skylon

His comment that "My Sinclair Spectrum was more powerful than the computer we used to design the RZ20" (in a Spaceflight interview in 1989) was a nice sidelight on the available computing power at the time.

However John Scott Scott said it was not quite that simple and in fact Bond had set up a small cluster of Spectrums to act as server farm.

[JCRM]

This little animation of an exploded engine diagram turned up on the REL site, apparently at the end of July. Nothing new, just pretty.

https://www.reactionengines.co.uk/video/forward.webm

The Hot HTX tests were slated for Q3 this year, has anyone seen anything about them starting? finishing?

[edzieba]

Nothing from Reaction engines themselves, but a press release from Consarc (who developed the furnace for brazing the HEX microtubes) mentions:

SABRE’s modular design allows each component to be built and ground-tested independently. Testing of representative technology (known as HTX) will begin in late 2018 at a soon-to-be-completed test facility at Front Range Airport near Watkins, Colorado.

[Soundbite]

Reaction Engines must have seen your comments as they have just released a review of their 2018 activities https://www.reactionengines.co.uk/news/building-momentum-our-development-programme. The following are snippets of what they have stated: "In Colorado, USA, we have recently completed the construction of a new high-temperature airflow test facility located at the Front Range Airport near Watkins, Colorado.... We are now at the facility shakedown phase where a series of systems tests are being conducted ahead of the commencement of the ‘hot’ heat exchanger tests... In the UK, our TF1 test site is on track.... our Applied Technologies team has continued to explore opportunities across multiple sectors including aerospace, motorsport and energy... generating significant interest with exciting announcements anticipated in 2019.... Our diverse and talented employee numbers have reached 200." Merry Christmas to you all

[kuldan]

Not to set any hairs on fire for mentioning Starship (ex BFR):

SpaceX wants to fly many people on Starship to locations in the Solar System, but the issue with Launch Escape seems to come up in discussion very often.

If you take designs from REL from a few years ago, they were considering building a small space station (actually more of a space dock) for building orbit-only crafts - if Skylon ever turns out working as expected (SSTO with meaningful payload), would it be an interesting thing to combine both systems?

What I'm envisioning is to build a spacedock as proposed by REL, but use Skylon primarily for high-value-low-weight cargo (Humans, electronics/whatever is suspectible to G-Forces etc.), and fly "bulk" cargo like raw materials/prefab parts and fuel using reusable Starship cargo trips?

I obviously am not a space engineer, but based on intuition, a skylon with engine failure looks like a considerably more survivable reentry/landing compared to a rocket that cannot generate meaningful lift on its own... and I don't know about you, but I guess a lot of people would feel safer on a "plane"-style vehicle...

[edzieba]

It's a good question what Skylon's abort profiles look like. To be any decent sort of glider it would need to dump most propellant for those little stubs to do much good, and re-entry likely assumes a mostly empty Skylon too (with most prop expended getting to orbit and the deorbit burn). That leaves a gap where Skylon is going fast enough on a suborbital trajectory to have to perform a high energy re-entry in case of an abort, but still having a large amount of propellant on board that would need to be rapidly dumped beforehand.
And an Engine Rich Combustion event would likely be quite a bit worse than with Starship/Super Heavy, with ejected turbine bits liable to try and chop the thing in twain.

[CameronD]

It's a good question what Skylon's abort profiles look like. To be any decent sort of glider it would need to dump most propellant for those little stubs to do much good, and re-entry likely assumes a mostly empty Skylon too (with most prop expended getting to orbit and the deorbit burn). That leaves a gap where Skylon is going fast enough on a suborbital trajectory to have to perform a high energy re-entry in case of an abort, but still having a large amount of propellant on board that would need to be rapidly dumped beforehand.
And an Engine Rich Combustion event would likely be quite a bit worse than with Starship/Super Heavy, with ejected turbine bits liable to try and chop the thing in twain.

From images readily available I'd expect this thing would have the glide ratio of a house-brick.  As you point out, those little stubs would require a fairly speedy landing at the best of times, limiting emergency landing options and meaning you wouldn't want to get too far away from the airport you took off from.

In an engine-out scenario, maybe they could lose forward speed at a reasonable altitude and parachute from there? https://en.wikipedia.org/wiki/Cirrus_Airframe_Parachute_System
 

[JCRM]

To be any decent sort of glider it would need to dump most propellant for those little stubs to do much good,

From images readily available I'd expect this thing would have the glide ratio of a house-brick.  As you point out, those little stubs would require a fairly speedy landing at the best of times, limiting emergency landing options

Skylon is designed to be able to land on conventional runways.

Once propellant has been dumped, the stubby wings (with a wing area slightly larger than a A321) and lifting body tail have to carry a sixth of the take-off weight (about 15% less than an A321 mlw) giving a landing speed of around 130 knots (less than an A321)

This may have been mentioned once or twice before https://forum.nasaspaceflight.com/index.php?topic=30547.0

[john smith 19]

From images readily available I'd expect this thing would have the glide ratio of a house-brick.

You're pretty poor at judging flying characteristics.

Unlike Shuttle, whose slab sides were about all the CFD of the early 1970's could cope with the body is a Sears Haack shape, the optimum volume for hypersonic flight. With LOX dumped (which is the majority of the mass) it's 150 tonnes lighter and Skylon was designed to cope with an engine out event throughout most of the takeoff and acceleration phases. Protecting the payload at all costs (even if the vehicle will never fly again afterward was part of the mission). That's before it dumps the LH2 and switches off the engines.

As you point out, those little stubs would require a fairly speedy landing at the best of times, limiting emergency landing options and meaning you wouldn't want to get too far away from the airport you took off from.

In an engine-out scenario, maybe they could lose forward speed at a reasonable altitude and parachute from there? https://en.wikipedia.org/wiki/Cirrus_Airframe_Parachute_System
 

Or maybe you could just glide? The body alone will generate significant lift.

Again, unlike Shuttle (mostly because Skylon does not have a huge point mass hanging off it's rear) it's statically stable.

I'd guess that it could be piloted by a human directly linked to the flying controls. Again unlike the Shuttle, where APU failure meant the computers, the controls (and probably the crew) would all die.

[Lars-J]

From images readily available I'd expect this thing would have the glide ratio of a house-brick.

You're pretty poor at judging flying characteristics.

And you are pretty great at making up handling characteristics for paper aircraft. JS19 is back to his old habits of writing checks that RE/Skylon can't cash.

[JCRM]

And you are pretty great at making up handling characteristics for paper aircraft.

It seems a little disingenuous to describe as "a paper aircraft" a design that has undergone wind tunnel testing to improve confidence in its compliance to its specification.

"Brass aircraft" instead?

I'm also interested in what handling characteristics you believe JS19 "made up". The static stability and engine out capability are documented design features.

[Lars-J]

And you are pretty great at making up handling characteristics for paper aircraft.

It seems a little disingenuous to describe as "a paper aircraft" a design that has undergone wind tunnel testing to improve confidence in its compliance to its specification.

"Brass aircraft" instead?

I'm using "paper aircraft" to mean "an idealized not yet built thing".

I'm also interested in what handling characteristics you believe JS19 "made up". The static stability and engine out capability are documented design features.

But that sometimes has little bearing on final product features. Just like the early Shuttle program in the early 70s has many design features that would allow rapid reusability and low cost. It didn't turn out that way. The way JS19 opines about Skylon you would think it was two degrees short of curing cancer. In reality - if Skylon was fully funded - they would run into many engineering compromises that could cripple it or its flight safety. Would the final model have 'static stability'? Not necessarily. Would it be capable of engine out engines on the extreme ends of the wings, at all phases of flight? Extraordinary claims require extraordinary evidence. Could it just dump all Hydrogen quickly to allow it to glide at all? How exactly? The fastest way to empty a propellant tank for a rocket propelled vehicle is to actually burn it through the engine. But with one engine out, how fast can it be dumped in order to not fall like a brick? The list goes on and on.

We live in a real world with real engineering trade offs. Skylon still lives in the paper world where everything can be solved by writing another paragraph about a design feature that can solve everything. Or a spurious claim on an internet forum by a Skylon evangelist.

[Dao Angkan]

Come on guys, Skylon is dead, but SABRE is very much alive. A bit boring to read in here all the time about Skylon which is no longer being pursued, whilst the exciting SABRE devlopments are buried in circular arguments. Could we just have a SABRE updates thread for those of us who just want to follow that?

[john smith 19]

Come on guys, Skylon is dead, but SABRE is very much alive. A bit boring to read in here all the time about Skylon which is no longer being pursued, whilst the exciting SABRE devlopments are buried in circular arguments. Could we just have a SABRE updates thread for those of us who just want to follow that?

And you know this because?

SABRE was designed for Earth to orbit flight. Once you factor in the huge shift in CoP across 23 Mach numbers and the massive forces needed to keep anything that's rear end heavy pointing in the right direction (which was what killed HOTOL) you find something like would the preferred option, assuming you have 2 engines available.  For a 1 engine design (like a FTV) you're looking at something like the X-7, but that is not anywhere near as optimal, although I expect it would be good enough to prove the air breathing to rocket transition, which AFAIK neither of REL's ground facilities can duplicate. 

[Star One]

Come on guys, Skylon is dead, but SABRE is very much alive. A bit boring to read in here all the time about Skylon which is no longer being pursued, whilst the exciting SABRE devlopments are buried in circular arguments. Could we just have a SABRE updates thread for those of us who just want to follow that?

In the same way that the Starship is the ultimate goal of Space X, so Skylon is the ultimate goal of REL

[Dao Angkan]

Come on guys, Skylon is dead, but SABRE is very much alive. A bit boring to read in here all the time about Skylon which is no longer being pursued, whilst the exciting SABRE devlopments are buried in circular arguments. Could we just have a SABRE updates thread for those of us who just want to follow that?

In the same way that the Starship is the ultimate goal of Space X, so Skylon is the ultimate goal of REL

No, REL is no longer pushing Skylon, SpaceX is pushing Starship ... big difference.

[Star One]

Come on guys, Skylon is dead, but SABRE is very much alive. A bit boring to read in here all the time about Skylon which is no longer being pursued, whilst the exciting SABRE devlopments are buried in circular arguments. Could we just have a SABRE updates thread for those of us who just want to follow that?

In the same way that the Starship is the ultimate goal of Space X, so Skylon is the ultimate goal of REL

No, REL is no longer pushing Skylon, SpaceX is pushing Starship ... big difference.

This is a mis-representation of REL’s long term position.

[Dao Angkan]

Come on guys, Skylon is dead, but SABRE is very much alive. A bit boring to read in here all the time about Skylon which is no longer being pursued, whilst the exciting SABRE devlopments are buried in circular arguments. Could we just have a SABRE updates thread for those of us who just want to follow that?

And you know this because?

From their business plan and roadmap. Just try finding any mention of Skylon on their website.

[Dao Angkan]

Come on guys, Skylon is dead, but SABRE is very much alive. A bit boring to read in here all the time about Skylon which is no longer being pursued, whilst the exciting SABRE devlopments are buried in circular arguments. Could we just have a SABRE updates thread for those of us who just want to follow that?

In the same way that the Starship is the ultimate goal of Space X, so Skylon is the ultimate goal of REL

No, REL is no longer pushing Skylon, SpaceX is pushing Starship ... big difference.

This is a mis-representation of REL’s long term position.

I'm happy to re-evaluate my current evaluation if you can show me that the current management are still pushing Skylon.