The Reaction Engines Skylon Master Thread (1)

[Kharkov]

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.

So really, Skylon could be built in the UK and once assembled could take a minimum fuel load & ferry itself to Kourou or wherever. Cool, a British programme providing British jobs.

Let's hope the E/D programme is successful. The longer the runway needs to be, the fewer the places Skylon can operate from. The DC-3, if Roger Longstaff doesn't mind me borrowing his metaphor, could operate from just about any airstrip in the world. It'd be nice if Skylon could do that too.

[flymetothemoon]

People are not saying he was uninformed because he got the disadvantages of airbreathing wrong.  He didn't.  They're saying he was uninformed because he gave an answer that seemed to assume a generic TSTO, when the question was about a specific SSTO.

I am not sure about the capabilities that you are attributing to Skylon here. It will for the most part be unmanned. So I am not sure about the retrieval part.

It has to be able to retrieve its own upper stage after a geostationary mission.  Presumably it wouldn't be that hard to have it do the same with other satellites, especially if it were equipped with an RMS (no indication that it will be, but it certainly could be.  With Falcon the option simply doesn't exist; you'd need to design a separate spacecraft to do the retrieval and reentry).

My question to Mr Hempsell:
I am also interested in the down mass capabilities. If you can abort any time up to orbit we might conclude the down mass capability were 15 tons, but without fuel that could conceivably be more. Can you let us know any more about that?

His answer:
We have not analysed re-entry beyond 15 tonnes but it may be OK to go to 30 tonnes if you stick to the Centre of Mass constraints in Figure 16 of the User’s Manual.  My concern is the increase in ballistic coefficient may push the re-entry temperatures above where we would be comfortable, but without analysis I could not be sure.  And before you ask - such analysis is very low down the “to do” list at the moment.

[DLR]

According to Reaction Engines, a single Skylon space plane is supposed to be capable of 200 flights before it has to be retired. How did they come up with that number? Why 200? Why not 50, 1000 or 5000? Which components of the vehicle impose this limit? The engines? The hull? The hydrogen tanks?

While it is a huge improvement over expendable launchers, 200 flights is still way outside "airplane territory", even compared to high-performance experimental aircraft.

[BobCarver]

musk seems to be the new messiah around here 

Actually, around here we follow the Church of Skylon but around the corner from here you'll find the SpaceXians who do hold Elon in some regard...

Bingo.  Both are getting more hype than warranted.

If NASA were on the job, there wouldn't be nearly as much interest in commercial space. The attention ("hype") is well deserved given the situation at NASA.

[RanulfC]

One thing I've noted in the "discussion" here is that there is a strict tendency to try and "seperate" SSTOs into "all-rocket" and "SKYLON" when in fact there are and were many proposals for various OTHER "not-all-rocket" SSTOs.

We're not comparing Skylon with alternatives.  We're comparing airbreathing with all-rocket, in the context of a Skylon thread.  Naturally Skylon is going to end up the champion of airbreathing...

Given the title of the thread of course Skylon is going to "naturally" end up being the champion of airbreathing...

My personal opinion is that is not "naturally" a given outside of this thread but for the sake or argument I'll let that one go

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.

The correct comparison is with LACE engines. Designs for this (Linde IIRC were active in this area) never worked without frosting up or meeting their weight goals. They used spinning heat exchangers in an attemp to "fling" the cooling water off the tubes. It did not work. The heat exchanger architecture and mfg techniques are 6x better in terms of heat capacity per unit mass than any other designs.

No your making the assumption that my point was a direct point-to-point program which it was NOT. LACE was a type of air-collection and cooling systems that was tried in the late 50s and 60s and yes it tended to frost up, a lot. Newer work has shown that a VERY simple method of not frosting up is to NOT use it on the ground, (ALCHEMIST) and the Japanese discovered (by accident) several ways to generate liquid air during the ATREX program so even in that regard RE's work is less "ground-breaking" that is being stated. (BTW, you might want to look a bit deeper into the more current work on LACE systems as the spinning "heat-exchanger" isn't actually the HE but a mechanical seperator of the nitrogen from the oxygen. Just FYI)

While it's great that the RE designs are "6X" better it remains to be seen if this will be enough to actually make a working engine.

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 capable 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.

SERJ was not designed to achieve SSTO. It was proposed to use as the 1st stage of a 2 stage LV.

Might want to look into that again, SERJ was ORIGINALLY designed to power a 0-Mach-4 interceptor for the military and was found to have many advantages in both staged and SSTO applicatioins. The "final" version of the SERJ which was called the "SynerJet" engine WAS designed for SSTO use and the "Spaceliner" VTVL SSTO vehicle designed around the engine. Some versions "required" scramjet operations while some did not and only air-breathed up to Mach-8.

I pointed it out in "comparision" to the SABRE because it was also seen as a highly disruptive propulsion system, unlike the SABRE though it has a much higher TRL and still did not make it into flight testing.

Uncooled airflows are much larger in volume.

Yes it does however COOLED air has to have added heat in for the form of more fuel to reach optimum combustion which is why most "power-plant" turbine engines need to recirculate exhaust heat for economic operations.

Simply "cooling" the incoming air doesn't net you much advantage, what DOES is cooling and mass addition such as MIPCC but at the added cost of lower ISP overall.

And "variable geometry" does not come much more so than retracting the turbine into a protective casing (SABRE variable geometry is mostly about changing valve settings).

"Variable geometry" is still a system to regulate the incoming air no matter how its done and while the SABRE method may be "simply" changing valve settings I don't believe that has actually been SHOWN yet so may be more speculation than fact at this point.

On the subject of "historical" air breathers the last (airbreathing mostly to orbit) US programme was the X30. As "facing the heat barrier" records it did not end well.

Which means you expect the Skylon to go the same way? After all it faces the majority of the same issues? As "Facing the Heat Barrier" clearly points out the X-30 had to many conflicting requirements and not enough avialable solutions for its needs. In most ways it was simply carrying on the 1950s "Aerospaceplane" concept into the '90s with very little work having been done with hypersonic flight in the interim.

It is interesting to note that like Skylon the X-30 latched onto a certain type of unproven propulsion and proceeded to build only and single mindedly on that system alone before having run any full scale (or at the time even small scale) succesful testing of an actual engine. Perhaps you're right there is a lesson to be learned there

The Nacelle Test Vehicle is a rocket powered vehicle to refine the design of the Nacelle. It is not designed to go above the transition speed. 
The rest of the flight path and vehicle development will be done by what REL refer to as the "boilerplate" or Y Skylon vehicle. That will be expensive but as  you may have noticed each phase  builds on the last and yes the cost multiplies as the vehicles get bigger.

So you're saying my assumptions were correct, thanks.

The issue here is the "Y" vehicle Skylon is going to have to be (from the way the program is working) pretty much a "full-up" vehicle to enable testing to the actual "proof-of-concept" stage. Anything smaller won't have the performance to reach hypersonic speeds and anything less simply won't be an actual "proof" of the concept. So what it seems you are indicating is that once the non-SABRE NTV is done then REL will be "stuck" waiting for a major infusion of money (government) in order to build a "boiler-plate" test vehicle that may or may not work as advertised.

Randy

[RanulfC]

I never said that it offers no real advantage.

Musk did.  I was talking about him, not you.

Hold on a second... Musk didn't say that "air-breathing" offered no real advantage, he said "air-LAUNCH" offered no real advantage or am I missing an "update" around here somewhere?

That is the entire point; he was talking about a two-stage system, which is irrelevant to the question because it totally changes the trades.  The fact that he apparently didn't know that SABRE is intended for an SSTO is why he has been accused of being uninformed.

I think we have an information "boggle" here folks, he was NOT talking about a "two-stage" system per-se he was talking about an AIR-LAUNCHED multi-stage rocket vehicle carred to altittude by a sub-sonic air-breathing carrier vehicle.

He isn't "talking" about Skylon for the very simple and practical reason that Skylon does NOT exist at this point and HIS TSTO-rocket powered Vertical Take Off space ships DOES exist.

I get the feeling that this whole argument is based on a misinterpreted statement and a feeling that because he hasn't thrown in the towel and declared the Skylon to be THE transport of the future he's "ignorant" about it. Not the case at all but simply the Skylon is not a "near-term" threat to his business and has yet to reach a point where it is possible for it to be considered "competition" in any respect. When it reaches a point where is become "credible" competition you can bet he'll take active interest, till then it's not an issue

Randy

[grondilu]

I get the feeling that this whole argument is based on a misinterpreted statement and a feeling that because he hasn't thrown in the towel and declared the Skylon to be THE transport of the future he's "ignorant" about it.

He was asked, at least twice, a specific question about Skylon, and he answered twice that to him the physics behind it did not make sense.  Even if he acknowledged that he might be wrong or might have made wrong assumptions about it, I think it's fair to say that he does not know much about Skylon, and that it's a shame because we surely would like to have a more educated opinion from him.

[Chris Bergin]

For for the new thread here: http://forum.nasaspaceflight.com/index.php?topic=30547.0

There was a whole jumble of "OMG, someone said ELON!!" and relevant Elon talking about Skylon comments at the end of this thread. Attempted to trim, went blind, gave up.