The Reaction Engines Skylon Master Thread (1)

[john smith 19]

Correct me if I'm wrong, but I thought the NTV were quite small, with no internal powerplant other than the COTS booster that it's attached to, something more akin to a larger, unpowered X-43 or X-51 than a vehicle that could reach orbit.

A subscale expendable vehicle with a single SABRE designed to reach orbit would be a great idea, but I don't think that NTV would be right for that.

http://www.slideshare.net/Stellvia/progress-on-the-skylon-reusable-spaceplane

Frame 28 lists the NTV as 9m long by 3.5m wide massing 1000Kg.
I think that's *much* too small to pack a pair of SABRE's, even *very* sub scale ones burning Methane. They look like they want to shake down the *whole* Skylon aerodynamic structure and you cannot do that with a single engine vehicle, which would be *radically* different in an airframe. IIRC Hempsell said it would be a Methane fueled rocket design and IIRC Bond said it'd be expendable, with about 7 vehicles in the test series *possibly* ending with one going to orbit, presumably if they got all the data they needed on the first 6.

My intuition is the NTV will *not* be air dropped as the UK (AFAIK) lacks recent experience  of dropping winged things this big off aircraft (I think it's the size of those anti ship missiles Tu95s carried but who wants to rent/buy one of those and get a crew to fly it?).

I'll note that an NTV making orbit would be a stunt (virtually no payload, 1 way) but *would* demonstrate the architecture could survive *ascent* loads and heating. Comforting certainly and if runway to orbit in some senses revolutionary still something any ELV is capable of.

OTOH if you could bring it *back* as well (even if it was set to crash into the sea, given both of the UK's rocket testing ranges are over sea) that would prove the *whole* flight path was survivable with the technology used, albeit with a payload of test instruments (which would be very re-assuring to your backers when you've got another c£12Bn to get  ). [edit]Note that Skylon is designed to land *without* control inputs so (in principle) it would be a case of getting its attitude correct and giving it enough impulse to get it to the re-entry interface altitude. Mr Newton handles the rest. [edit]

Note NTV's *core* mission is not going to orbit and focusing on that goal might warp the design too far from achieving its core objectives so I'd expect that to be a *very* low priority on their todo list.

[ukrocketman]

Regardless, it won't be turbomachinery or any other subsystem that makes or breaks Skylon, but rather the systems integration of the vehicle. Subsystems can be ground tested to death, but the overall system has to be tested on a real flight. If they can pull off just one flight, the risk level will become drastically lower.

The next phase described in the presentation I linked to shows their next phase plan in this area. It's a full sub scale SABRE engine and the (rocket powered) Nacelle Test Vehicle. I think the SABRE ground test was a recommendation of the ESA review. IIRC the original plan (described on their old website) was to do development testing of SABRE & its inlets on a pair of "boilerplate" Skylons. The engine will be *complete* but not flight weight and allowing replacement/substitution of key sections to allow for problems.

The NTV's have been described as multiple expendable rocket liquid fuel rocket designs weighing about 1 tonne and IIRC Hempsell said they would be Methane fueled. Good enough to verify flow predictions through the system and (if they're made of the same materials) the structural concepts.

*Ideally* the final step would be either for one of the NTV's to make orbit, given their mass ratio that would be a *very* big deal, and would lower the risk associated with the structural materials. Sadly with only one SABRE on test it would not be possible to build a complete sub-scale Skylon/SABRE system

The NTV is not designed to go to orbit. Nor could it. It is designed as a sub scale test vehicle. To go to orbit, you end up with a vehicle that would essentially be the same size as Skylon, would need 2 of the SABREs and is to all intents and purposes.... Skylon.

On another front, I spoke to Mark Hempsell yesterday, and I said if he gets chance, to pop in to this thread again to respond. It is just a question of him getting time. He's insanely busy, as I'm sure people will guess :-)

[kch]

On another front, I spoke to Mark Hempsell yesterday, and I said if he gets chance, to pop in to this thread again to respond. It is just a question of him getting time. He's insanely busy, as I'm sure people will guess :-)

Thank you for the heads-up -- looking forward to that. 

[Turbomotive]

Is the upper limit of GSO market 3,600 satellites at 6' apart? With a conservative flight turnaround of a week, 15 Skylons can fill 3,600 slots in 5 years. What do they do next?

[john smith 19]

Is the upper limit of GSO market 3,600 satellites at 6' apart? With a conservative flight turnaround of a week, 15 Skylons can fill 3,600 slots in 5 years. What do they do next?

It depends on your PoV. That might be a core market for the *operators* (and according to the market analysis done by London Economics as part of the BSA review 15 Skylons would put REL in profit and cover all *development* expenses).

The question then becomes who wants an *asset* that can put 15mT of cargo into LEO.

[Turbomotive]

The question then becomes who wants an *asset* that can put 15mT of cargo into LEO.

I might be interested in owning just one Skylon which could launch 200 satellites in 4 years, more than the entire extant fleet of GSO satellites. At US$20m a launch,and SKYLON at $2bn ($1bn to buy and $1bn lifetime maintenance) I'd make my money back in 2 years, not including the extra expense of SUS.

[Turbomotive]

Question for Mark Hempsell: How much to buy each of passenger module and SUS,  and are they usable beyond Skylon's 200 missions?

[john smith 19]

Question for Mark Hempsell: How much to buy each of passenger module and SUS,  and are they usable beyond Skylon's 200 missions?

Note that SUS is planned to be part of the Skylon system (based on the ESA review) but the "passenger module" was for *illustration* purposes only, to show what operators could supply as a minimum.

[Turbomotive]

Note that SUS is planned to be part of the Skylon system (based on the ESA review) but the "passenger module" was for *illustration* purposes only, to show what operators could supply as a minimum.

I see.. if lucky, free SUS with every Skylon, while passenger module, either develop and make yourself or wait for a passenger module company to do the same for off-the-shelf buy.

[lkm]

I don't think it's quite that simple as their test program intends to deliver people to the ISS so a passenger module has to exist before the in service date.
I think it's more how the development costs are structured, REI hopes that other commercial entities will take the opportunity to develop passenger modules and other potential Skylon add-ons in concert with the development program so that an ecosystem of competing accessories to your new Skylon will exist when you buy it,  like Apple's 'Made for IPod' but 'Made for Skylon'.
However ESA recommended that the SUS be lumped in with the Skylon development because it's so crucial to GEO operations.
If such an ecosystem can't be created then REI intends to develop things in house and the development costs get added on top of Skylon, increasing costs to $17.5 billion.

[john smith 19]

I see.. if lucky, free SUS with every Skylon, while passenger module, either develop and make yourself or wait for a passenger module company to do the same for off-the-shelf buy.

It's a bit more complicated than that.

SUS seems to be a pressure fed LO2/LH2 upper stage (I'm guessing as the engine is the one from their attitude control thrusters) with an Isp of about 462s (Big nozzle). The 7000kg propellant/950kg empty mass figures in the attachment listed down thread is for the *expendable* configuration designed to put comsats on GTO or possibly probes on an escape trajectory. Reusability may change those numbers a bit.

So buy an SUS for your comsat apogee burn or use use a solid AKM or use an oversize ACS/RCS on the sat to drive the apogee engine.
Using the SUS you *eliminate* the cost of the solid (and the hazards) and a Hypergolic ACS/RCS can stay sealed till final GEO.

REL anticipated personel module development to be quite expensive so think of it as a *reference* design (like the sort put out by say Microsoft or Intel on PC's). Their reference design demonstrates it would be *possible* to dock with ISS or with another Skylon for rescue purposes.

Of course you could trade those 24 seats for a smaller group with longer life support (subject to the 4 day on orbit limit for Skylon *unless* you set up as a free-flyer). That would allow an operator (presumably US based) to bid the ISS cargo and  crew re-supply contracts (if ISS is still in business). More specialised (non ISS, non staff/cargo transfer) uses could include.

Short stay/fast turnaround science observatories. This would give "targets of opportunity" without the whole ISS qualification process.

High privacy meeting rooms. A vehicle in orbit is *highly* isolated. Telemetry collection requires *substantial* pre-planning so a module designed to be radio silent/radio opaque  would be fairly easy to sweep for unauthorised transmitters. Properly planned logistics would be very difficult to even discover *who* was meeting as well what was said either during the meeting or afterward.

Recording studios. People have built recording studios in some very odd places, citing acoustics, ambiance of the environment, solitude etc. Such a module would need to be specially adapted and I've no idea if there would be a market for its use but I don't run a recording studio for a living. 

Obviously such facilities would be *very* expensive relative to ground based equivalents but the question would be do the (unique) benefits outway the high costs?

And of course if Bigelow launches its "space hotel" modules the *whole* game changes (but you can't rely on that).

[Jim]

Short stay/fast turnaround science observatories. This would give "targets of opportunity" without the whole ISS qualification process.

High privacy meeting rooms. A vehicle in orbit is *highly* isolated. Telemetry collection requires *substantial* pre-planning so a module designed to be radio silent/radio opaque  would be fairly easy to sweep for unauthorised transmitters. Properly planned logistics would be very difficult to even discover *who* was meeting as well what was said either during the meeting or afterward.

Recording studios. People have built recording studios in some very odd places, citing acoustics, ambiance of the environment, solitude etc. Such a module would need to be specially adapted and I've no idea if there would be a market for its use but I don't run a recording studio for a living. 

Obviously such facilities would be *very* expensive relative to ground based equivalents but the question would be do the (unique) benefits outway the high costs?

None of those are viable or bring any worth while benefits.

[Jim]

The question then becomes who wants an *asset* that can put 15mT of cargo into LEO.

I might be interested in owning just one Skylon which could launch 200 satellites in 4 years, more than the entire extant fleet of GSO satellites. At US$20m a launch,and SKYLON at $2bn ($1bn to buy and $1bn lifetime maintenance) I'd make my money back in 2 years, not including the extra expense of SUS.

It is too small for most of the GSO market

[Jim]

Also, this is completely ludicrous

"enable SKYLON to capture the entire market."

[Hempsell]

Having been given marching orders from UKRocketman I will try to address some of the recent issues raised in this thread working back.  General the discussion is already well informed and generally gets to conclusions I would agree with.

Working backwards

Jim: we have designed Skylon to match all existing applications although the US military will have to change the approach to some of their space applications – but felt in a way that makes things better but that is for them to judge.  We also tried to ensure any realistic future applications likely to occurred in the next few decades are also covered.  So whatever customers want to do with their Skylon it should manage.  I am unclear what is ludicrous about this. This subject is covered in the April 2010 Journal of the British Interplanetary Society (Mark Hempsell and Roger Longstaff “The Requirement Generation Process for the Skylon Launch System” JBIS, Vol. 63, pp.122-128, 2010)

John smith: the SUS is not pressure fed it uses the Skylon orbital manouvering (SOMA) engines and these are pump fed.  SUS details can be found in the April 2010 Journal of the British Interplanetary Society (Mark Hempsell and Alan Bond, “Technical and Operation Design of the Skylon Upper Stage”,  JBIS, Vol. 63, pp.136-144, 2010). This paper reports amore up to date than the design reported earlier. The SI is 4,560 N s/m.(note proper units) 465 sec.

The concept design for the passenger module assumed 24 passengers for 4 days.

lkm: is right to assume things are complicated regarding the passenger module.  Yes we assume this will be an independant development as we originally assumed for the upper stage.  The deal we were planning on offering is if your piece of infrastructure is ready for our test programme then you would get free test flights and these are in the test flight programme.  We will need at least one docking system element to prove Skylon’s capabilities and if none is independently developed we would have to add something like the SOFI to the “to do” list.

Turbomotive: The SUS will be an optional extra (not every customer would need this capability) costing around $70 million each and probably good for 10 flights (this number is TBD but unlikely to be anything like 200) as the IAC paper posted by lkm shows.  The change is we are including it as a development the Skylon consortium is responsible for rather than leaving it to third parties.  This does not stop third parties developing their own upper stages if they think they can do better.

I am guessing any passenger module would probably be designed for 200 flights to match the Skylon – I would do this if it were down to me.

On the marketing of course our market analysis is commercially confidential however the key point to realise is than no operator uses their Skylon to its capacity.  Also as Skylon will be classed a dual use technology there maybe constraints on an operator selling their Skylon, but in principle John smith is right.

I am also going to duck investor questions again because it touches commercially confidential areas.

On the NTV discussion as UKRocketman notes it is a flight vehicle design to test the nacelle and in particular the intake up to around Mach 4.5.  It does not have any of the interior features of the SABRE engine.  It is under review as it may be possible to do this validation work in a wind tunnel without the risk of a flight vehicle.  We will all have to wait and see on this on

The vehicle were all the engine and airframe systems get flight tested are the two pre-production prototypes (misuse of term prototype I am afraid I did not do the naming) these are like to old USAF Y-planes - they will look like Skylons but build on soft tooling with Block 1 SABREs, they almost certainly will not make orbit, and they will not have items like payloads bays.  Any problems found on these vehicles can be corrected in the production design.

With regard to the skill base required for the Skylon vehicle and SABRE engine, Reaction Engines clearly has neither the size or skills base to do it all; indeed I am not sure any company has such a complete capability.  But it has always been the intention to do both engine and airframe with consortia of companies which, combined, do have the necessary manpower and skills.  What Reaction Engines does have is the capability to do the engine and SKYLON system studies required at this stage of the project, and ESA certainly has the capability to review it (including turbine fed engines).  I think some contributors are not fully aware of the skill set has at ESTEC, while CNES does manage a lot of the big engine work ESA has complete technical involvement and are quite capable of evaluating our work.

The development timescales are fast by space launcher standards but not civil aircraft.  The difference is whether you are funded by government fixed budgets which are not repaid or funded by investment which has to be repaid with interest. 

I would disagree with QuantumG we are well past lab work stage particularly with the Pre-Cooler Heat exchanger; the modules on test are flight representative.  We are almost at TRL 5 and we fall short only because we have not yet put 1000C air through the intake

I agree with Pippin on the importance of systems engineering (I used to teach systems engineering at postgraduate level so I would wouldn’t I), but I think we are on top of that aspect of the project and we have not had any fundamental issues in this area during the ESA review.  The point is the development programme has a build up of higher an higher levels of verification – following the classic V diagram.  Sure there will be serious issues along the way, but the programme planning and parametrics allow for that and the only way to get from here to there is by doing the work – i.e. further talk, concept studies, and basic technology development will now just get in the way.

BobCarver slightly exaggerates the TRL level of the TPS the materials do not quite go back to the 1960s and we do have to prove the TPS working as a system (TRL 6 and above).

Turbomotive list of things that could go wrong

The whole SABRE principle being wrong? 
Unlikely given several independent analyses and modelling over almost a decade.  If there was a fundamental problem it would have been spotted by now.

Precoolers not working or icing the engine?
The recent test programme has eliminated that possibility

Engine not producing enough thrust for orbit? 
It is unlikely given the thrust generating element is a chemical rocket engine, and the performance of chemical rocket engines can be very precisely calculated, as we have done the rocket engines we have built and tested.

Thermal protection system inadequate?
Like all the airframe elements the precise technical solution we have selected may not be the best, but it is unlikely there is no technical solution.

or something else?
Well yes there is always the unknown unknowns but hardly an excuse to give up

Adrianwyard “too early/blue-sky optimistic. (e.g. HOTOL in the 80s)”  I would dispute that.  The reasons the Government and Rolls Royce pulled out have not been established and, in line with other completely bonkers UK aerospace decisions, may never be known.  It was not because it not judged feasible.  An independent assessment from RAE Farnborough to inform government decision making on HOTOL clearly showed it was.  This has been vindicated by history, because we are doing nothing now on Skylon that we could not have done in the 1990s

93143 comment on C2 versus D1 performance.  At the moment the numbers are identical. The User Manual is slightly optimistic at high altitudes (600-800km) but otherwise it is good.  At the moment we have capped Skylon to 800km but I am considering a lower cap at 600 km as no one has expressed an interest in orbits above 600 km.

Stopping here or it will completely consume my little remaining life

[Dappa]

Having been given marching orders from UKRocketman I will try to address some of the recent issues raised in this thread working back.  General the discussion is already well informed and generally gets to conclusions I would agree with.

Thanks for that!

[flymetothemoon]

I would disagree with QuantumG we are well past lab work stage particularly with the Pre-Cooler Heat exchanger; the modules on test are flight representative.  We are almost at TRL 5 and we fall short only because we have not yet put 1000C air through the intake

Precoolers not working or icing the engine?
The recent test programme has eliminated that possibility

Like!

Thanks for popping in.

Good luck!

[MikeAtkinson]

I will try to address some of the recent issues raised in this thread working back. 

Thanks for that.

[john smith 19]

John smith: the SUS is not pressure fed it uses the Skylon orbital manouvering (SOMA) engines and these are pump fed.  SUS details can be found in the April 2010 Journal of the British Interplanetary Society (Mark Hempsell and Alan Bond, “Technical and Operation Design of the Skylon Upper Stage”,  JBIS, Vol. 63, pp.136-144, 2010). This paper reports amore up to date than the design reported earlier. The SI is 4,560 N s/m.(note proper units) 465 sec.

I had not realised the SOMA engines were pump fed. I'd put the high Isp down to the stage using LO2/LH2 and a really big nozzle. The report attached to (IIRC) ikm's post described it as being in expendable mode for GTO missions.

lkm: is right to assume things are complicated regarding the passenger module.  Yes we assume this will be an independant development as we originally assumed for the upper stage.  The deal we were planning on offering is if your piece of infrastructure is ready for our test programme then you would get free test flights and these are in the test flight programme.  We will need at least one docking system element to prove Skylon’s capabilities and if none is independently developed we would have to add something like the SOFI to the “to do” list.

Turbomotive: The SUS will be an optional extra (not every customer would need this capability) costing around $70 million each and probably good for 10 flights (this number is TBD but unlikely to be anything like 200) as the IAC paper posted by lkm shows.  The change is we are including it as a development the Skylon consortium is responsible for rather than leaving it to third parties.  This does not stop third parties developing their own upper stages if they think they can do better.

I am guessing any passenger module would probably be designed for 200 flights to match the Skylon – I would do this if it were down to me.

 Also as Skylon will be classed a dual use technology there maybe constraints on an operator selling their Skylon, but in principle John smith is right.

MY (unstated) belief was operators could sell on their Skylons to anyone *not* on (for wont of a better description) the UN "bad boys" list  .

On the NTV discussion as UKRocketman notes it is a flight vehicle design to test the nacelle and in particular the intake up to around Mach 4.5.  It does not have any of the interior features of the SABRE engine.  It is under review as it may be possible to do this validation work in a wind tunnel without the risk of a flight vehicle.  We will all have to wait and see on this on

Logically you would go with whatever path gives the lowest development cost, *however* I would suggest that it would be a opportunity for the airframe design team to do something that would help them to "jell" as a team, as well as possibly to get some early validation of Skylon construction techniques and inspection techniques, assuming you're going with those for the NTV. Obviously if you expect Skylon airframe design will be handled mostly by the consortium when it forms then such a benefit would be irrelevant. I guess it would depend on how settled that decision is.

My hope that the last NVT *might* make orbit was always a *very* long shot and a stunt, as its "payload" would be it's data acquisition and telemetry system, which I would guess will mass a few 10s of Kg at most. Barely enough for a round of cheese. 

The vehicle were all the engine and airframe systems get flight tested are the two pre-production prototypes (misuse of term prototype I am afraid I did not do the naming) these are like to old USAF Y-planes - they will look like Skylons but build on soft tooling with Block 1 SABREs, they almost certainly will not make orbit, and they will not have items like payloads bays.  Any problems found on these vehicles can be corrected in the production design.

...and ESA certainly has the capability to review it (including turbine fed engines).  I think some contributors are not fully aware of the skill set has at ESTEC, while CNES does manage a lot of the big engine work ESA has complete technical involvement and are quite capable of evaluating our work.

The development timescales are fast by space launcher standards but not civil aircraft.  The difference is whether you are funded by government fixed budgets which are not repaid or funded by investment which has to be repaid with interest. 

I noted that one aspect that was not "stress tested" by London Economics was what happens to investment costs if there are programme delays. Aside from "nothing good" have any qualitative tests been made on this area? It seems a blind spot unless "floats" have been built into the schedule already (some of your later comments suggest they are) . I'm not asking *what* the outcomes would be, just weather some testing has been done or if the floats exist in the detailed schedule.

I think Spacex's experience might be relevant here. They had a *very* conventional TSTO VTO LV and internal funding (but a new team with limited development experience) which *should* have made for a development plan that ran on schedule but (I'm sure Jim can give the exact figures) it ended up years behind schedule.

Sure there will be serious issues along the way, but the programme planning and parametrics allow for that and the only way to get from here to there is by doing the work – i.e. further talk, concept studies, and basic technology development will now just get in the way.

That sounds like the time to move into *detail* design and build has begun. I hope so.

The reasons the Government and Rolls Royce pulled out have not been established and, in line with other completely bonkers UK aerospace decisions, may never be known.

Hmm.UK Govt making bonkers aerospace decisions. Surely not 

[simonbp]

Another thanks for the copious response, Mark.

The vehicle were all the engine and airframe systems get flight tested are the two pre-production prototypes (misuse of term prototype I am afraid I did not do the naming) these are like to old USAF Y-planes - they will look like Skylons but build on soft tooling with Block 1 SABREs, they almost certainly will not make orbit, and they will not have items like payloads bays.  Any problems found on these vehicles can be corrected in the production design.

I cannot wait to see one of these blasting down a runway! 

(on the precooler)
We are almost at TRL 5 and we fall short only because we have not yet put 1000C air through the intake

Presumably, this would be the last test for the precooler before trying to build a basic breadboard SABRE?