The Reaction Engines Skylon Master Thread (1)

[Seer]

Can those who think that Skylon should aim to be TSTO explain how that would even work? I.e at what point the upperstage would stage and where it would go - inside the first stage, under it or above it?

[mmeijeri]

Can those who think that Skylon should aim to be TSTO explain how that would even work? I.e at what point the upperstage would stage and where it would go - inside the first stage, under it or above it?

It would be inside the cargo hold, and would be released after the first stage had pulled up to a suborbital trajectory, once dynamic pressure had dropped enough to make release feasible.

[john smith 19]

+ I am ignoring the realities of international politics and trade - e.g. in reality a US Gov project is not likely to buy Skylon flights, and of course other counties cannot simply buy SLS flights. I'm just trying to think about the generalized arguments people make for small/cheap/frequent services vs super-heavy/integrated approaches to launching big projects.

The REL model is that once they have sold a Skylon it's the owners business what that do with it.

If that's the US Govt or a US based company that offers flight services to the US Govt It's certainly possible for ISS 2.0 to launch on Skylon, bearing in mind half the ISS modules were built in Italy anyway.

I *strongly* doubt NASA would let any outside payloads on SLS.

Skylon is the size it is because the only *consistent* market they could find that makes *profit* on launches is the launching of communications satellites. That's how big *any* launcher needs to be to put a current generation commsat in orbit.

Note *all* commsats have a further stage to get them to GEO, usually a solid fuel Apogee Kick Motor but it can be integrated with the station keeping liquid fuel system.

AFAIK REL have *no* interest in TSTO. However they have considered Skylon in a *sub* orbital mode. IIRC their rough estimate is the payload *doubles*. Current AKM's are about 30% of total mass to GTO, so an upsized AKM *might* be enough to deliver a normal size commsat to GEO (but I'm not familiar enough with solids to know).

Steven Pietrebon (no I didn't check that name either) who posts on NSF some time has also done modelling on "nearSSTO" but not AFAIK using HTOL.

[flymetothemoon]

I'm wondering why it costs $10 billion to get something flying. A full scale proof of concept vehicle  perhaps. Skylon is afterall just a drone. A very large drone, but a drone none-the-less.

The A380 cost  EUR 11 billion to develop and Airbus are very familiar with building large aircraft.

Although I would agree. I think (or is that I like to think?) the sceptics can overplay how much it could eventually cost. REL have carefully modelled their costing against other projects including Concorde (which they were familiar with being Rolls Royce and BAe engineers) and even with contingency believe their figures to be good.

What we dont know is how much, using the same estimating modelling, those figures will come out as for Skylon D1 when it is time to make those estimations. An A380 would end up costing more than EUR 11 billion if you started it today.

[flymetothemoon]

...ESPECIALLY if the costs are similar to pursuing something uselessly conventional....

Skylon is /the/ most expensive RLV project out there (much more than a conventional expendable, for sure), as far as estimated/likely costs for development. Blue Origin and SpaceX's vehicles...

I agree and understand that. I was referring to spending 10 billion on yet another ELV. HTOL RLVs are another thing and have no doubt I am rooting for SpaceX. The amount of money he does things for is extraordinary too.

Even with SpaceX there though I think there is a place for Skylon, although clearly their pitch is queered a little as compared with 10 years ago.

...don't forget downmass...

http://forum.nasaspaceflight.com/index.php?topic=24621.msg896575#msg896575

And let's not also forget that by the end of the year they will hopefully be able to tell us that they have revolutionary, durable, flight-weight pre-coolers - good for Mach 5+. Who knows who might want to pick them up and run with them?

[aero]

I'm wondering why it costs $10 billion to get something flying. A full scale proof of concept vehicle  perhaps. Skylon is afterall just a drone. A very large drone, but a drone none-the-less.

The A380 cost  EUR 11 billion to develop and Airbus are very familiar with building large aircraft.

Although I would agree. I think (or is that I like to think?) the sceptics can overplay how much it could eventually cost. REL have carefully modelled their costing against other projects including Concorde (which they were familiar with being Rolls Royce and BAe engineers) and even with contingency believe their figures to be good.

What we dont know is how much, using the same estimating modelling, those figures will come out as for Skylon D1 when it is time to make those estimations. An A380 would end up costing more than EUR 11 billion if you started it today.

Those comparable vehicles have a major cost driver that Skylon doesn't. They are man rated commercial passenger vehicles, Skylon is an unmanned drone. (Yes, Skylon hopes for passengers in the future, but not now.) Early Skylon vehicles should be built to service the LEO satellite market, not the future tourist market. Looking at the real market as it exists, do they really need 200 test flights before going operational. To get the first 5 (my number) Skylons flying, do they really need so much payload or would a few tonnes of extra structure and test equipment be acceptable in a prototype?

I don't know but I think a big hurdle to funding is the investors concern that Skylon won't fly. Something built on the cheap that flys would counter that concern. Other side of that coin is that something built on the cheap that lofts only 3 (my number) tonnes to LEO would color the investor perception in a totally different, negative way.

[adrianwyard]

Don't forget the ~$10B figure isn't simply to construct and fly the first operational vehicle; it's the complete development program which includes many, many test steps including building and flying several Nacelle Test Vehicles. Also, another feature of Skylon/SABRE to bear in mind is the fact that so much of it can be ground-tested (unlike, say, scramjets). Others who are closer to the actual details can correct me, but I would say the problem faced is not finding someone with a spare $10B, but rather the several hundred million needed to advance the TRL on the components. *This* investment could be for nothing if they uncover a project-killing problem. But once you have a SABRE working to spec on the static test stand, and the Nacelle has been verified in flight conditions, and a section of fuselage/TPS passes arc-jet testing and is not too heavy, then at that point some very large entity comes in with the billion-dollar cheque. (And as others have said that cheque very probably doesn't go to REL.) Just as with a big project like the A380, this multi-billion dollar investment is only made once the business case is clear, and absolutely everything is at a very high testing readiness level.

So... who has a few hundred million to spare?

[flymetothemoon]

So... who has a few hundred million to spare?

Me! Me! Damn. No. It isn't me 

[adrianwyard]

OK, semi-seriously, has anyone heard of any interest in Skylon from Richard Branson/Virgin Galactic? For a few hundred million, I bet Bond and company might be willing to rename Skylon 'SpaceShipFour'...

And how would such an investment work, assuming that at a later date the project is likely to be lead by a consortium of industry giants?

[zt]

Doesn't SpaceShipTwo belong to the U.A.E. now? Do people want them owning the rights to affordable access to space?

Do you think REL's exit plan is to license the IP to BAE/EADS and become the ARM of hypersonic engines or to sell the company to BAE/EADS? Or will that depend on whoever funds the full SABRE static test stand demo?

[The man in the can]

I have read this entire thread, one subject that didn't come forward often is the airframe. The SABRE engine is an amazing piece of technology but Skylon still need to be quite a light aircraft for its size to achieve SSTO.

here some quotes from old posts:

...
Call me a cynic, but I'm tempted to think that the weights work on paper because they have to work on paper, if they don't the Sabre's no longer have a function on a launch vehicle, and the entire enterprise is questionable.

...
On the other side of the argument the main reason our structure masses are lower than conventional civil aircraft of comparable dimensions is the truss frame structure - like an airship.
...

I don't remember any aircraft of this size flying with such an airship structure, even less flying supersonic with such a load of propellant. Does Reaction engines have plan to demonstrate the feasibility of such structure for such an aircraft. 

I'm new on this forum. I'm surprise that people like Mr Hempsell take time to answer some unknown guys on the net.

[john smith 19]

I have read this entire thread, one subject that didn't come forward often is the airframe. The SABRE engine is an amazing piece of technology but Skylon still need to be quite a light aircraft for its size to achieve SSTO.

I don't remember any aircraft of this size flying with such an airship structure, even less flying supersonic with such a load of propellant. Does Reaction engines have plan to demonstrate the feasibility of such structure for such an aircraft. 

I'm new on this forum. I'm surprise that people like Mr Hempsell take time to answer some unknown guys on the net.

There are not many. Most seem to have been built by Vickers aircraft and designed by Barns Wallis. The most famous was the WWII Wellington bomber.

The technique delivers a very strong design (proven in combat) but was manpower intensive to construct and difficult to modify (this was at a time when "Calculator" was a job title, not a machine and "numerical control" meant cutting a set of cams on a spindle  ).

An early REL programme was to evaluate the exact joint design and how to mfg it. IIRC the current materials for the struts (unidirectional carbon fibre with a Titanium alloy end pieces to allow flash welding) are being re-considered with a view to moving to a light weight alloy (I can't recall if it's porus or uses strengthening wires strung through it)

It's true no one has built a vehicle this big with these materials that is partly compensated by the corrugated skin being used on some parts of the SR71 and the "hairpin" rivet being spec'd for the X20 Dyna-Soar as a way of coping with the expansion mismatch.

[RobLynn]

An early REL programme was to evaluate the exact joint design and how to mfg it. IIRC the current materials for the struts (unidirectional carbon fibre with a Titanium alloy end pieces to allow flash welding) are being re-considered with a view to moving to a light weight alloy (I can't recall if it's porus or uses strengthening wires strung through it)

Aren't they now using a Titanium-SiC MMC?  Seems like a good option if it is manufacturable as it is likely to be able to be able to handle brief periods at 800+°C which might just make it survivable for the airframe if there is a localised TPS failure during a mission. 

[john smith 19]

Aren't they now using a Titanium-SiC MMC?  Seems like a good option if it is manufacturable as it is likely to be able to be able to handle brief periods at 800+°C which might just make it survivable for the airframe if there is a localised TPS failure during a mission. 

That sounds correct. One cited benefit of the Shuttles aluminum design was it's ability to cope with brief localized hot spots by conducting it away. The MMC will not be as good but likely quite a bit better than carbon fiber

[flymetothemoon]

Interesting extra information about ESA engagement...

http://www.space.com/16780-skylon-space-plane-progress.html

Roll on one year's time!

[Hempsell]

I don't remember any aircraft of this size flying with such an airship structure, even less flying supersonic with such a load of propellant. Does Reaction engines have plan to demonstrate the feasibility of such structure for such an aircraft. 

Originally all aircraft used truss framework structures with separate aeroshell normally doped canvas.  Semi-monocoque construction was brought it just prior to the Second World War but many aircraft were still using it.  The largest truss framework aircraft I know of is the Messerschmitt Me 323 Gigant but I would not cite that as technology heritage.  So yes we do have plans for structural tests of the concept (including flight verification) before it ends up in the production SKYLONs.

Which raises the long debate about the technical risk which I afraid I think is rather sterile – yes SKYLON has more new technologies than a conventional expendable but those risks are known and the Technology Readiness Levels are assessed and where necessary the programme addresses them though specific test activities.  Technology Readiness Levels (TRL) are explained in the post by krytek but the wording of that version can lead into the trap of forgetting that it is experience with the under lying technology and not the specific design that matters.

There is no identified technology in SKYLON baseline below TRL 4 although we are looking at a few options (like the silicon carbide reinforced titanium) which we are bringing up to TRL4 to see if we can rely on their initial promise.  At TRL 4 you do not have any real risk the technology will not work, more concerns over exact performance, cost and secondary operational issues, and while this affects the assessment of margins we have to carry, it does not impact on the feasibility of the SKYLON system.  This has been the conclusion of all independent assessments based on full access to the SKYLON/SABRE material.

I have just gone through the recent post and some answers to other points might help the discussion.


aero “I'm wondering why it costs $10 billion to get something flying.”

Because it doesn’t - $10 billion includes the qualification programme to get the plane into operational service not just the first flight.  It is comparable to the cost of a large civil jet program such as the Airbus A380 for pretty much the same reasons.


adrianwyard  It's clear that the Scimitar engine is much farther down the road than SABRE, due to its greater complexity. And I'm pretty sure I recall Mark Hempsell saying Skylon would not work well for point-to-point for various reasons, but I do wonder if the super-fast civil transport market might be easier to open.”

The answer is it isn’t easier – nor is the business case yet clear.  Scimitar must have lifetimes and reliabilities comparable to modern jets, and the Reaction Engines A2 configuration requires technologies well below TRL 4.

And another from adrianwyard   “I think it's fair to say the business case for Skylon is dependent on its existence enabling a greatly expanded launch services market.”

While we would all expect a massive increase in traffic t space once SKYLON is in operation, and the lower cost we quote for mature operational cost do assume some growth, it is wrong to say that SKYLONs business case depends upon this.  We can have 30 sales and the commercial operators can still recover their costs with profit, without any increase in the existing open launches market, it is just launch prices do not drop as much in this scenario.

[aero]

Thanks for your reply. I thought it was something like that.

[MikeAtkinson]

Thanks Mark for your continuing replies.

Do you think there is a market for non-commercial Skylons? By non-commercial I mean countries and other organisations that operate Skylon(s) for reasons other than profit. These reasons might include military, assured access to space, national prestige, perhaps even a billionaires personal Skylon.

[adrianwyard]

Yes, thanks very much Mark for your responses.

As far as I know the most detailed public discussion of Skylon economics is in the ESA Skylon Assessment document:
http://www.bis.gov.uk/assets/ukspaceagency/docs/skylon-assessment-report-pub.pdf

Pages 16-25 talk about the economic justification for Skylon development costs, and indeed mentions 30 Skylon sales as a goal, but as far as I can tell any discussion of Skylon's impact on the launch market are in supporting 'Requirements Documents' that are not available.

Is there a better source? Perhaps this sort of thing is confidential...

With 30 Skylons available to launch payloads, and the number of payloads per year similar to today, wouldn't many of them be sitting idle for long stretches of time, even if you capture most of the market?

See also:
http://forum.nasaspaceflight.com/index.php?topic=24621.msg883583#msg883583
http://forum.nasaspaceflight.com/index.php?topic=24621.msg884414#msg884414
and the surrounding posts.

[simonbp]

I really like the reusable upper stage. It neatly solves the issue of a fully-reusable GTO launch system without the complexity of Fluyt. Presumably that's a single Vinci engine?