The Reaction Engines Skylon Master Thread (1)

[flymetothemoon]

Well it did seem likely we wouldn't be getting any early pre-cooler testing news...

http://www.reactionengines.co.uk/news_jan12.html

[john smith 19]

Can anybody link to that story?

http://www.armadilloaerospace.com/n.x/Armadillo/Home/News?news_id=369#EngineDevelopment

I did. It suggests that Armadillo (along with Rotary Rocket/Xcorp, NASA and REL) have also demonstrated that LOX cooling (without even *knowing* it) does not in fact bring about the fall of civilization as we know it.

Which is quite amazing given the fear the process has engendered.

[Seer]

If Skylon were to increase their payload bay from 4.8m to 5m diameter, and the length from 13m to 14m, they could fit the Bigelow 330 module inside.
The mass of this module is 20 tonnes - higher than the 15 tonne Skylon payload, but some mass could be offset from the module.
 Also, Skylon could utilise a suborbital insertion, which would boost the payload a further 1.5 tonnes. Would this be worth doing? I don't imagine the payload penalty would be much, about half a tonne.

[deltaV]

If Skylon were to increase their payload bay from 4.8m to 5m diameter, and the length from 13m to 14m, they could fit the Bigelow 330 module inside.
The mass of this module is 20 tonnes - higher than the 15 tonne Skylon payload, but some mass could be offset from the module.
 Also, Skylon could utilise a suborbital insertion, which would boost the payload a further 1.5 tonnes. Would this be worth doing? I don't imagine the payload penalty would be much, about half a tonne.

The chances of either BA 330 or Skylon actually flying is low; the chances of both flying is very low. Even if both fly the timing isn't right, with BA 330 scheduled to launch mid-decade and Skylon flying many years later.

Skylon will only be worth its development costs if it flies hundreds to thousands of times. The handful of potential BA 330 flights wouldn't make a significant difference to the business case even if they were timed correctly.

[john smith 19]

If Skylon were to increase their payload bay from 4.8m to 5m diameter, and the length from 13m to 14m, they could fit the Bigelow 330 module inside.
The mass of this module is 20 tonnes - higher than the 15 tonne Skylon payload, but some mass could be offset from the module.
 Also, Skylon could utilise a suborbital insertion, which would boost the payload a further 1.5 tonnes. Would this be worth doing? I don't imagine the payload penalty would be much, about half a tonne.

The increase to 4.8m in diameter and 15 tonnes capacity was a result of a fairly extensive consultation exercise described in IAC-10.D2.4.7

I think that re-sizing to accommodate Bigelow modules would skew their design too much to a fairly high risk *potential* payload for which a number of other vendors already have launch capability.

*However* AFAIK Skylon already has the capability to mate with an existing Bigelow complex in the same way it could mate to ISS. It would be up to a buyer of one or more Skylons if they wanted to do so.

[cuddihy]

The increase to 4.8m in diameter and 15 tonnes capacity was a result of a fairly extensive consultation exercise described in IAC-10.D2.4.7

Which puts Skylon at the same point technically that shuttle was c. 1972-73.

The reality is that until the SABRE engine is proven, the radical TPS and structure is built and tested at cryo LH2 temperatures and proven to the point that they can be sure it will not collapse mid-flight or even on the runway awaiting takeoff, they can spec and trade any payload dimensions they want.

Till then, it's all spitballing because noone even knows if its physically buildable. I do daresay that if an operating RLV is completed, Bigelow along with every other satellite builder will make the payloads fit the RLV, not the other way around. (although there probably is an 8-10 ft minimum dimension for human spaceflight.

[93143]

What radical TPS and structure?  The design is creative, but it doesn't push the technical envelope like Shuttle and VentureStar did.

Your lack of confidence in engineering calculations and modelling seems extreme.  They're well into detailed design of the fourth major vehicle revision...

[john smith 19]

Which puts Skylon at the same point technically that shuttle was c. 1972-73.

No. Skylon has already been through several design cycles already.

The reality is that until the SABRE engine is proven,

Large segments of which are happening now.

the radical TPS and structure is built and tested at cryo LH2 temperatures

The purpose of the design is to *avoid* the TPS or main load bearing structure from *ever* getting to LH2 temperatures, which is fairly obvious from a brief glance at the structure.

and proven to the point that they can be sure it will not collapse mid-flight or even on the runway awaiting takeoff, they can spec and trade any payload dimensions they want.

I think you underestimate how much design work has been done on this and the impact further changes (*especially* increasing the payload by a *further* 1/3 above the 1/4 they have already increased it by) would have on an HTOL design versus a conventional ELV.

Till then, it's all spitballing because noone even knows if its physically buildable.

So what is REL's incentive to move from a difficult to build design to a *very* difficult to build design, in your opinion?

I do daresay that if an operating RLV is completed, Bigelow along with every other satellite builder will make the payloads fit the RLV, not the other way around. (although there probably is an 8-10 ft minimum dimension for human spaceflight.

Which suggests there is *no* reason to change it yet again given that (in your opinion) Bigelow would change their design to fit the payload bay.

4.8m is roughly 15' 8" and REL have done a *reference* design for a crew carrying module with docking facilities and ground access, although they expect this is something operators will have built for them as part of their business plan and is not (AFAIK) being planned as a product.
It's on their web site.

[john smith 19]

What radical TPS and structure?  The design is creative, but it doesn't push the technical envelope like Shuttle and VentureStar did.

That's not really fair.

The TPS is looking to be a corrugated rigid Silicon Carbide reinforced glass currently baselined as a French product called PyroSic which AFAIK has never flown in space while the structure, originally unidirectional carbon fibre tubes with Titanium end fittings into hexagon shaped carbon fibre end fittings is now spec'd with SiC fibre reinforced Titanium in a spaceframe. Again not something with any flight experience AFAIK. Likewise the deeply pre-cooled turbo/ramjet/rocket. Nothing close to this has been inside a wind tunnel since the mid 1960's.

The tanks are aluminum with PU foam insulation which is fairly common state of practice (might go to Al-Li with FSW but I'd guess that would depend on the legal position with the NASA closed loop welding licensing) held in place with Kevlar cord (shades of dirigible airship design). 

I'd guess REL would say they have been no more innovative than they *need* to be to meet the requirements they (and their customers) feel are *crucial* to build a viable system.

In *some* areas they have more heritage than either Shuttle or X33 and they've designed out the *most* problematic X33 feature (the composite LH2 tank) but this is a *highly* innovative design. However the team seem wide open to the issues and appear to have the plans in place to *rigorously* test at each stage before moving on.

And they have been able to raise the money to move forward, which suggests their backers convinced they know what they are doing.

Your lack of confidence in engineering calculations and modelling seems extreme.  They're well into detailed design of the fourth major vehicle revision...

I'd agree. The REL team's experience comes from a number of projects one of which was Concorde. This was subject to 3 different *prototype* designs at a huge increase in cost. It has given them a preference for solid analysis followed by firm movement in a particular direction. So far they seem to have avoided paralysis by analysis. Hopefully they will keep it up. At present it looks like we will find out in April.

[93143]

The TPS is looking to be a corrugated rigid Silicon Carbide reinforced glass currently baselined as a French product called PyroSic which AFAIK has never flown in space while the structure, originally unidirectional carbon fibre tubes with Titanium end fittings into hexagon shaped carbon fibre end fittings is now spec'd with SiC fibre reinforced Titanium in a spaceframe. Again not something with any flight experience AFAIK.

Actually, last I checked (Hempsell, Bond, Varvill, & Bond (2011)), they had decided to drop Pyrosic in favour of rebuilding the supply chain for System2.

Also, the struts are currently plastic composite; they've cited a need for more testing before baselining the titanium/SiC tubes, as well as a need to get the manufacturing cost down.

Do you have more recent information?

Likewise the deeply pre-cooled turbo/ramjet/rocket. Nothing close to this has been inside a wind tunnel since the mid 1960's.

Obviously the engine is fairly ambitious (though, as you note, currently engaged in risk reduction).  I was just talking about the rest of the vehicle, which is innovative but doesn't seem as risky as certain past efforts.  Maybe I'm being overconfident...?

...

It would be cool if they could use AlLi tankage, perhaps with some of that improved/braced MLI that's been in development lately...  Right now, they're aiming for an ITAR-free product, so they seem to be actively avoiding any American involvement...

[john smith 19]

[quote author=john smith 19 link=topic=24621.msg864864#msg864864
Actually, last I checked (Hempsell, Bond, Varvill, & Bond (2011)), they had decided to drop Pyrosic in favour of rebuilding the supply chain for System2.

That was my impression based on them going quiet on Pyrosic but Hempsell has posted here that their approach is more to work with the Pyrosic product and improve it to System2 capabilities.

Also, the struts are currently plastic composite; they've cited a need for more testing before baselining the titanium/SiC tubes, as well as a need to get the manufacturing cost down.

Do you have more recent information?

I'd have to check my notes if that was posted here or if it came from a presentation.

Obviously the engine is fairly ambitious (though, as you note, currently engaged in risk reduction).  I was just talking about the rest of the vehicle, which is innovative but doesn't seem as risky as certain past efforts.  Maybe I'm being overconfident...?

...

You may have overestimated the TRL's for some of the components. Only time will tell if the REL teams confidence in their approach is misplaced.

It would be cool if they could use AlLi tankage, perhaps with some of that improved/braced MLI that's been in development lately...  Right now, they're aiming for an ITAR-free product, so they seem to be actively avoiding any American involvement...

Yes REL are adamant on avoiding ITAR and rightly so. Surprisingly AlLi seems to be a big part of the new AirBus A380 so it's supply may not be such an issue. Likewise FSW was originally developed by TWI (or The Welding Institute as they were originally called) in the UK.

The joker in the pack is that the "closed loop" welding tool, that allows full circular welds, was developed by NASA. FSW scores over conventional MIG/TIG because it gives near parent metal strength and seems to virtually eliminate re-work, which has to be allowed for in the design as it knocks down strength still further.

This would mean either a "mostly" FSW design (for example a *spiral* weld, like that used for making pipe, or only the longitudinal joins being FSW) or diffusion bonding as the only ways to get join strength that good. Once you actually have to *melt* the metal strength always suffers. Laser or electron beam *might* improve on MIG/TIG but I'm not clear how big a gain you'd get.

[flymetothemoon]

Shakedown!

http://www.reactionengines.co.uk/news_feb12.html

[antiquark]

Anyone know why the Sabre engine exhaust points downward by a few degrees? That's something I've never seen before on existing aircraft. You'd also think that a fixed angle could be inefficient at some phases of flight.

[flymetothemoon]

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

 

[antiquark]

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

Thanks. Seems strange though, you'd expect all existing aircraft to have curved engines, if it actually helped with flight. 

[truth is life]

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

Thanks. Seems strange though, you'd expect all existing aircraft to have curved engines, if it actually helped with flight. 

Well, if the performance gains are less than the expense...(eg., in maintenance, in replacing existing systems which assume straight through engines, etc.).

[flymetothemoon]

My guess would be that regular aircraft have a balanced design for a mixed flight profile of:

- climb
- potentially hours of horizontal flight
- descent

...whereas skylon must be completely optimised to breath the ever thinning atmosphere during climb to MACH 5+ to achieve its key function of single stage to orbit.

[tlesinsk]

1. An aircraft's engines need not be aligned with its center of mass since any resulting torque can be cancelled by trimming aerodynamic surfaces. That only works as long as you are in the atmosphere.

2. Aircraft designers usually manage to make the fuselage parallel to the direction of flight in typical conditions (esp weight) to minimize drag. The problem with Skylon is that it is about five times heavier on ascent than at landing. Either you put big heavy wings, or you use smaller ones that are light but good enough for low-speed descent/landing, and takeoff at high speed then fly up at a significant angle of attack. Plus, I would expect the hypersonic inlets on Skylon to be less tolerant of AOA than those of a fighter jet or airliner.

[WellingtonEast]

Pardon if I have missed it.

Once the SABRE precooler, attached to a Rolls Royce Viper jet is tested - whats the next development step.

In particular I was wondering about flight testing.
Will this engine be flight tested in a standard fighter jet  or will it have to wait for a actual skylon airframe?

[simonbp]

IIRC, the next major steps are to ground test a full SABRE engine, and then fly a few subscale "Nacelle Test Vehicles" to test the engines and (especially) inlet geometry at high speeds and low pressures. Then, I think the plan is build a full prototype...