Author Topic: The Reaction Engines Skylon Master Thread (5)  (Read 441250 times)

Offline flymetothemoon

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #800 on: 11/06/2015 11:22 PM »
The question is can REL turn this increase exposure into either increased funding or move them forward in forming the Skylon consortium?

REL said that with the involvement of BAe, the group now has "no immediate funding needs". Does this mean they are not looking for funding? Does BAe involvement effectively block any more investment anyway since they are now prepared to handle everything up to at least working test engine?

Online Alpha_Centauri

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #801 on: 11/07/2015 12:52 AM »
Can't see a Skylon airframer committing until there is a representative demonstration of the SABRE cycle, REL doesn't have an actual product to offer them until then.  Right now the focus will be on that, which is what the tie-up with BAE should hopefully deliver.
« Last Edit: 11/07/2015 12:52 AM by Alpha_Centauri »

Offline Dalhousie

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #802 on: 11/07/2015 08:44 AM »
No, the interviewer was harping on about the intercontinental transport, while the guy from REL clearly said their focus was on orbital in "10-15 years" and intercontinental in "about 20 years".

The media almost always seem focus on LAPCAT rather than Skylon.  Hypersonic transport has a higher public profile than just another space launcher.
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Online Alpha_Centauri

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #803 on: 11/07/2015 09:09 AM »
A little bit more in here about there not necessarily being change in direction vis-a-vis skylon,

http://fortune.com/2015/11/06/bae-commercial-space-launch/

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And for BAE, it offers a critical toehold in the growing space access market. While BAE’s North American arm does a fair amount of business in satellite components and the like, the company has no significant presence in the commercial space launch industry. “It’s a market we’re interested in but we were looking for a different way of doing it,” Allam says. “We were looking for a breakthrough or something new as opposed to just joining everybody else.”

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And what about that super-high-speed point-to-point passenger travel—four hours from anywhere to anywhere on the globe? It’s certainly possible with this kind of technology, Reaction’s Thomas says. But given various safety and technical considerations, a spaceplane making regular trips to orbit at 25 times the speed of sound is the more realistic near-term proposition.

“A lot of people are excited about point-to-point travel at the moment, the thought of going anywhere in the world in four hours just excites people,” he says. “But that is hugely challenging, it’s just orders of magnitude more difficult. I was telling someone from Australia recently that, unfortunately, it’s more difficult to get to Australia than it is to get into space.”

Offline lkm

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #804 on: 11/07/2015 10:08 AM »
Can't see a Skylon airframer committing until there is a representative demonstration of the SABRE cycle, REL doesn't have an actual product to offer them until then.  Right now the focus will be on that, which is what the tie-up with BAE should hopefully deliver.
Except of course that BAE is an airframer not an engine maker and their biggest contribution to the current development program could actually be the design and development of the test aircraft they wish to fly by 2025,  doing that is very much within their capabilities and not REL's and functionally wouldn't be much different to Taranis so would be a useful activity to give to their aircraft design teams.

Offline flymetothemoon

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #805 on: 11/07/2015 10:20 AM »
Can't see a Skylon airframer committing until there is a representative demonstration of the SABRE cycle, REL doesn't have an actual product to offer them until then.  Right now the focus will be on that, which is what the tie-up with BAE should hopefully deliver.
Except of course that BAE is an airframer not an engine maker and their biggest contribution to the current development program could actually be the design and development of the test aircraft they wish to fly by 2025,  doing that is very much within their capabilities and not REL's and functionally wouldn't be much different to Taranis so would be a useful activity to give to their aircraft design teams.

Quite. One thing I am liking about BAE's involvement is the potential for airframe research to be significantly further forward at the end of this test engine development phase than might otherwise have been the case. Let's hope that time is well used.

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #806 on: 11/07/2015 01:11 PM »
Can't see a Skylon airframer committing until there is a representative demonstration of the SABRE cycle, REL doesn't have an actual product to offer them until then.  Right now the focus will be on that, which is what the tie-up with BAE should hopefully deliver.
Except of course that BAE is an airframer not an engine maker and their biggest contribution to the current development program could actually be the design and development of the test aircraft they wish to fly by 2025,  doing that is very much within their capabilities and not REL's and functionally wouldn't be much different to Taranis so would be a useful activity to give to their aircraft design teams.

BAE used to be a major airframer but they have steadily eroded that side of their business over the last couple of decades to concentrate on generic platforms that are less dependant on any specific government programme. They are more focussed on things like avionics now.

You are probably right that BAE may well develop test vehicles for SABRE, but I would expect a full Skylon would require them partnering up with an outfit like Airbus.

Offline Star One

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #807 on: 11/07/2015 02:42 PM »

Can't see a Skylon airframer committing until there is a representative demonstration of the SABRE cycle, REL doesn't have an actual product to offer them until then.  Right now the focus will be on that, which is what the tie-up with BAE should hopefully deliver.
Except of course that BAE is an airframer not an engine maker and their biggest contribution to the current development program could actually be the design and development of the test aircraft they wish to fly by 2025,  doing that is very much within their capabilities and not REL's and functionally wouldn't be much different to Taranis so would be a useful activity to give to their aircraft design teams.

BAE used to be a major airframer but they have steadily eroded that side of their business over the last couple of decades to concentrate on generic platforms that are less dependant on any specific government programme. They are more focussed on things like avionics now.

You are probably right that BAE may well develop test vehicles for SABRE, but I would expect a full Skylon would require them partnering up with an outfit like Airbus.

I increasingly see the parallels with the Taranis technological demonstrator. As that is to drone technology so this will be to hypersonic research.

Wonder if the demonstrator will be manned or a drone?

Offline lkm

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #808 on: 11/07/2015 04:56 PM »
Can't see a Skylon airframer committing until there is a representative demonstration of the SABRE cycle, REL doesn't have an actual product to offer them until then.  Right now the focus will be on that, which is what the tie-up with BAE should hopefully deliver.
Except of course that BAE is an airframer not an engine maker and their biggest contribution to the current development program could actually be the design and development of the test aircraft they wish to fly by 2025,  doing that is very much within their capabilities and not REL's and functionally wouldn't be much different to Taranis so would be a useful activity to give to their aircraft design teams.

BAE used to be a major airframer but they have steadily eroded that side of their business over the last couple of decades to concentrate on generic platforms that are less dependant on any specific government programme. They are more focussed on things like avionics now.

You are probably right that BAE may well develop test vehicles for SABRE, but I would expect a full Skylon would require them partnering up with an outfit like Airbus.
Absolutely, in fact I was arguing this some pages back when we were discussing prospective consortium members but I think it's still fair to say that BAE is more of an airframer and supplier of things that go into them than they are a maker of engines.
When it comes to Skylon there are definitely things they'll need Airbus as a supplier for but I could see BAE being involved in construction if a UK assembly site is required. BAE has often looked enviously at Lockheed Martin as their main rival and they have extensive involvement in space launch so BAE could be wishing to follow suit.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #809 on: 11/07/2015 05:06 PM »
I increasingly see the parallels with the Taranis technological demonstrator. As that is to drone technology so this will be to hypersonic research.

Wonder if the demonstrator will be manned or a drone?
I hope not.

Taranis was billed as costing £140m, it's now running about £185m.

The European Neuron project (which seems similar) is listed at about 25m euros, with roughly 75% of the takeoff mass.

That's not exactly the kind of tight cost control you want from a supplier/consortium member.  :(
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Offline Hanelyp

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #810 on: 11/07/2015 05:09 PM »
So, I was watching this interview on CNN and the image below popped up. What is this?

http://www.cnn.com/videos/business/2015/11/04/bae-systems-reaction-engines-mark-thomas-intv-qmb.cnn
That concept looks like someone took an X-30 style scramjet with forebody integrated inlet and aftbody integrated exhaust nozzle, stripped out the scramjet engines the underbody was designed to serve, and stuck sabre engines on wingtips.  I'm thinking with that fuselage shape you might do better with the sabre engines installed center-body where the scramjets would be, using the contoured underbody for inlet and exhaust.

It may look that way, but it's not just an artists' impression or derived from an X-30 style scramjet design. It's the result of an aerothermal study of Skylon:

http://strathprints.strath.ac.uk/41933/1/Brown_et_al_Towards_Robust_Aero_Thermodynamic_Predictions_for_Re_Usable_Single_Stage_to_Orbit_Vehicles.pdf
That looks like a study of reentry aerodynamics at high angle of attack, not the low angle of attack on the way up.

Offline lkm

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #811 on: 11/07/2015 05:49 PM »
I increasingly see the parallels with the Taranis technological demonstrator. As that is to drone technology so this will be to hypersonic research.

Wonder if the demonstrator will be manned or a drone?
I hope not.

Taranis was billed as costing £140m, it's now running about £185m.

The European Neuron project (which seems similar) is listed at about 25m euros, with roughly 75% of the takeoff mass.

That's not exactly the kind of tight cost control you want from a supplier/consortium member.  :(

I think the 25m euros is the estimated unit cost not the development cost which was 405m euros or £289m also Taranis is autonomous while the Neuron isn't, I don't think.

Offline 93143

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #812 on: 11/08/2015 03:46 AM »
The Space Shuttle was supposed to be orders of magnitude safer than previous vehicles too.  Its projected reliability was far, far greater than what it turned out to be in practice.

Yes, but that was because NASA was trying to happyface its way through an abysmally underfunded development program in which they were forced to heavily compromise their vision to save money, coming straight off the Apollo program which they must have considered the greatest achievement of human history and which had given them the impression that they were invincible.  Lots of doublethink.  The problems with STS were known; they were simply brushed aside.  The same thing happened during operation, in the lead-up to both accidents.  And REL knows this.

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The point is with a new design that is very different from existing systems you usually don't know what will be the real reliability problems.

No, not exactly.  But you can make a fair guess, especially if you've done detailed design studies, which they have.

Besides, Skylon isn't nearly as unique as Shuttle was.  Just about everything about STS was new - the high-pressure closed-cycle hydrogen rockets, the reusable thermal protection system next to (and under) the giant foam-insulated drop tank, the large segmented solids, even the whole idea of a winged reusable orbital vehicle had never been done before.  And the whole thing ended up an insanely hard-to-maintain kludge with built-in issues that could never be fully mitigated.

The main innovations with Skylon are the precooler (proven on the test stand, and apparently surprisingly robust) and the structural concept (which I have a hard time seeing as a potential reliability problem, considering the ease of analysis and the extensive testing regimen).  Standout risks that occur to me are the sweat cooling system for the canards, the potential for FOD on the runway and MMOD on orbit, and the rocket-mode transition (which should get an enormous amount of testing and debugging before the flight test programme so much as starts).

The high-pressure hydrolox rocket engines are a potential issue, but the pressure is much lower than that of the SSME, and pressure makes an enormous difference in the difficulty of designing a reliable engine - look what happened to the service lifetime and estimated failure probabilities on the SSME when they widened the throat slightly.  And as I said, the SABRE avoids a lot of the known issues with the RS-25 - the combustion chamber is oxidizer-cooled, the hydrogen and helium turbopumps are run by warm hydrogen gas turbines, and the oxygen turbopump and air turbocompressor are both run by helium.  There is no turbomachinery downstream of the preburner.

Modern launch vehicles are so unreliable in large part because they're expendable; every flight is the first real test of the vehicle.  F9R doesn't entirely get rid of this issue, nor did STS (even some of the "reusable" parts needed rebuilding).  Skylon does.

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Skylon is more of an airplane than a rocket.
People tend to think that.  It's human nature.  What does it look like that I understand?  OK, so it must behave like that.

But it's not always so.  We can look deeper and see if it really holds.

Yeah, why don't we?  That statement was not intended as a point on its own; it was a lead-in to the rest of the paragraph.

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It is all those things that give it much more risk than a typical airplane.

That might be why the loss-of-vehicle numbers are so much higher than for a typical airplane.  There's an enormous reliability gap between a 737 and a Delta II, and one can make massive improvements over the latter without coming anywhere near the former.

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It takes off and flies like an airplane, which allows it to have full intact abort capability (including engine out) with no black zones.
It only has an abort capability for certain kinds of failures, not all the kinds of failures a more traditional launch vehicle with an abort system has.

No traditional launch vehicle has an abort system.  Manned capsules have abort systems.  The rocket is a writeoff, and if the payload doesn't have an abort system it's a writeoff too.  We were talking about the likely effect of a launcher's reliability on its share of the satellite market, no?

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For example, if Falcon 9 has an engine that is about to explode and destroy the main propellant tank

Skylon's propellant tanks aren't right next to the engines, and if they're serious about aviation-style certification I'd really kinda expect to see measures to prevent engine failures from penetrating the fuselage.  Falcon 9 has something similar, since their engines are right next to one another and they take engine-out capability seriously.

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If the Skylon main prop tanks are about to explode, nothing at all can be done.

Yes, but how likely is that?  Prop tanks don't explode on their own, especially ones that have been flown a minimum of four times already and inspected for issues afterwards.

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And Falcon 9/Dragon has no black zones in its abort capability either.  It's not an "intact" abort in the sense that the first and second stages are possibly lost, but that's a positive, not a negative, because it allows the people to escape and survive when the engines and prop tanks explode.

This isn't about Dragon.  This is about the launch vehicle.  Most payloads don't have escape systems.  And Skylon won't be carrying people until it's been proven to be safe enough to do so; it's primarily a satellite launcher.

Furthermore, if a failure destroys the launch vehicle, (a) you can't inspect it to find out what went wrong, and (b) you need to replace it with a factory-fresh flight unit that may have bugs.  If your failure rate exceeds your retirement rate, this could noticeably damage reliability all by itself.

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It lands like an airplane (well, like a glider), which is a comfortable, well-understood maneuver (particularly for a computer)
The computers doing a Dragon propulsive landing are just as "comfortable" with that landing maneuver.

Falcon 9 isn't, which is part of why it hasn't worked yet.  Compare to Buran.

I admit that isn't an especially strong argument.  However, I still believe that the inclusion of an engine start as a single-string critical-path item with no time for any failure contingency is likely to be bad for reliability, and as I explained above, if the recovery reliability gets bad enough it can indirectly affect the payload delivery reliability.

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If Skylon loses propulsion

Which is massively more unlikely than losing partial propulsion - remember, it has effectively two engines (nowhere near each other) in airbreathing mode, and four in rocket mode.

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Also, propulsive landings give more than one shot at an approach.

Not the way Falcon 9 does them, they don't.

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It is intended to be certified like an airplane, with an extensive test programme putting two prototypes through hundreds of flights including dozens of abort tests,
And Dragon can do exactly the same thing.

Are you claiming that SpaceX plans to fly a specific Dragon 2 flight unit into orbit and back 204 times, and take another one through over a hundred envelope exploration flights including dozens of aborts of various flavours, before so much as offering the capsule on the market?

Besides, I'm not talking about Dragon.  This is a launcher comparison.  Those numbers are even more ridiculous when applied to Falcon 9.

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and each production unit will undergo four test flights before delivery.
Dragon can do exactly the same.

Will it?

But again, this isn't about Dragon.  Falcon 9 won't; of that I'm nearly certain.

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It is also an SSTO, which means that it can wait out bad weather on orbit or divert to almost anywhere in the world (the wings afford a very large cross range),
That has absolutely nothing to do with it being SSTO!

It has everything to do with it.  Falcon 9 can do nothing of the sort, because the recoverable part isn't orbital.

But that's beside the point, because Falcon 9 can simply wait out bad weather on the pad, since the recovery happens so quickly.  This is why I removed this point from my previous post before you made your response.

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and that if staging (a major launch risk) is required at all, it can be done at a leisurely pace after the launch, as more of a payload deployment than a controlled inflight breakup.
Staging of Falcon 9 is in no meaningful way like an "inflight breakup".  That's just a meaningless emotional argument about superficial similarity with no substance to it.

You are deliberately taking my words in the most unreasonable sense possible.  Staging is a significant element in launch risk.  The point I'm making is that Skylon's "staging" procedure is far more benign and can take advantage of procedural risk mitigation strategies that are simply not available to a TSTO of any description.  That's if it's necessary at all, and for a LEO payload it's not.

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And of course it's fully reusable, which means infant mortality should be way down.
SpaceX is closing in on reusability of both their first stage and Dragon.  Both are designed for it.  SpaceX has also said they plan to eventually have a reusable second stage, though they're not pursuing that at the moment.  But you can bet that if the flight rate is high enough to make it make economic sense SpaceX will create a reusable upper stage.  The cost for SpaceX to create a reusable upper stage should be far, far less than the cost to develop Skylon, so the advantage is to SpaceX on the reusability front.

You're really reaching here.  Skylon is completely reusable; it doesn't even drop a "trunk".  There is no way for any system to have an advantage over Skylon "on the reusability front" unless development goes south and they need to do extensive refurbishment like STS (and let me assure you, they have heard of STS; they aren't going into this blind).

By contrast, SpaceX does not currently plan to reuse upper stages (perhaps because it would be fairly costly to get it to work, never mind get it to the level of tested reliability Skylon is targeting), and apparently the question of what to do with the FH core is still open.  Even if they do end up reusing the upper stage, simply stacking a fully reusable TSTO would be enough 'rebuilding' to make it less completely reusable than Skylon, since the stage mating is untested on every flight.

Dragon is, as always, irrelevant to this comparison.

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The REL team has a lot of experience doing research on engine components and writing slideware, not much on systems that actually become operational.

This is not actually true, except in the sense that some of them have been working on Skylon for a while, and Skylon isn't operational yet.  Plenty of REL personnel have had experience on systems that became operational before becoming part of REL, and that includes the founders.

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In other words, those are more like must-not-exceed numbers than optimistic projections.
But there's no way they could possibly know the real reliability.  They are of course optimistic projections not grounded in any evidence.

That doesn't follow.  They don't know the real reliability, but based on the information we have, they do apparently think they can at least guarantee certain numbers regardless.  It is your opinion that isn't grounded in any evidence.

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STS killed more astronauts than any other space launch system in history.

The Challenger accident had nothing to do with the liquid hydrogen systems, and the Columbia accident was a result of a specific design feature that was known to be risky from the start and which Skylon doesn't share.

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STS's problems came from trying to push the edge of what is possible -- exactly what Skylon hopes to do.

No.  STS's problems came from trying to push the edge of what was possible at the time with about half as much money as they needed to actually do it right.  Skylon is not about trying to push the edge of what's possible - it's about using ingenious game-changing ideas to make a reusable SSTO shuttle comfortably possible without having to push the bleeding edge.

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Even those should be greatly mitigated by the extensive flight test programme (so systematic design and maintenance issues can be worked out) and by the highly reusable nature of the whole system (so you don't have untried factory fresh parts on every launch).
Falcon/Dragon has all those advantages too

I will not address Dragon further.  Falcon does not have those advantages, and it won't for a long while if it ever does.  SpaceX didn't kick off their program by putting a pair of reusable vehicles through a series of 400 test flights (the bulk of them orbital), nor have they been holding each individual booster back from launching commercial payloads before its fifth flight, and as far as I know they have shown no sign of doing either of those things in the near future.  And there is currently no plan to do anything other than use a brand new upper stage on every flight.

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but without the disadvantages of having to use liquid hydrogen (very low temperatures and hydrogen working its way into everything, causing leaks and embrittlement)

We know a fair bit more about hydrogen handling in reusable systems than we did in the '60s and '70s (thanks in part to STS), and the engine at least seems to be designed to mitigate hydrogen-related issues.  The issues can be mitigated, and I'd certainly expect them to have a handle on the problem by the end of that monster test programme of theirs.

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and the disadvantages of having to be single-stage to orbit (so there is less margin available for safety).

Apples to oranges.  The whole point of Skylon is that the engine concept enables SSTO without razor-thin margins.

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Based on what we know of the engine, they seem to have circumvented the main issues with the SSME that made it dangerous and maintenance-intensive.
It's premature to make pronouncements about an engine that hasn't been built yet.

Depends on the pronouncement.  We have high-level schematics for SABRE, and we know what the fundamental problems with the SSME were.  We can see that SABRE steers around those problems.

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STS had one catastrophic engine failure -- of a solid engine.

That had nothing to do with hydrogen, unless you're going to argue that the solids were only needed because they went with a hydrogen-fueled TAOS, which is really stretching your point...

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Ummm... Development costs are sunk costs and so have no impact whatsoever on the operational economics.
They affect launch prices (not costs),
No, they affect costs.  Development costs are costs.

They are not costs associated with the ongoing operation of the system.  If you somehow managed to steal a Skylon, you could use it without worrying about the development cost.  Once the development is finished, that outlay becomes part of the price structure (because people want their money back); it's not an ongoing cost.  This is illustrated by the bankruptcy/writeoff/restructuring scenario pippin described.

Frankly I can't believe you challenged me on that.  You've plainly overshot the point of honest disagreement and are in condescending contrarian territory.

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The price a company charges isn't necessarily directly related to the costs.  It often has more to do with the market -- what the market will bear.

True, but if the vehicle was priced higher than its manufacturing cost + profit margin in order to make back the development cost, that raises the minimum price the operator will be willing to charge, because he wants to make back the purchase price.

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Even as matters stand, the numbers they're talking about seem pretty competitive.  The more SpaceX expands the market, the more likely it becomes that Skylon will undercut them.
I don't see any evidence for that.  An expanding market allows SpaceX to lower prices too because its per-flight costs go down when volume goes up too.

Not as much as Skylon's do.  That's the advantage of a fully reusable low-overhead fast-turnaround ground-maneuverable HTOL SSTO, and it's the reason I mentioned the high development costs.

You don't seem to get this - Skylon (if it works out as hoped) looks to be competitive despite the high development cost.  What that high development cost does is increase the slope of the curve so that the system gets more expensive faster as the market shrinks - or in other words, it gets cheaper faster as the market grows.

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there are two factors that argue for it having higher per-flight operational costs: the fact that it uses liquid hydrogen (look at Delta IV's costs versus Atlas V) and the fact that it is single-stage (so it has less mass margin to use making things more rugged and cheaper to maintain).

That doesn't guarantee Skylon's costs will be higher, but it suggests they are likely to be.

No, it doesn't suggest anything of the sort.  You're comparing apples to oranges here; the vehicles are too different to suppose that those factors are likely to be dominant.

Besides, Skylon has plenty of mass margin and a higher structural safety factor than Falcon; the margin troubles show up with the Falcon upper stage.  And hydrogen does have reusability advantages vs. kerosene to go with the disadvantages.

...

There are a lot of unknowns, and I don't want anyone to take this as a confident prediction of the future.  But I do think you are being unfair to Skylon.
« Last Edit: 11/08/2015 04:06 AM by 93143 »

Offline 93143

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #813 on: 11/08/2015 04:20 AM »
It lands like an airplane (well, like a glider), which is a comfortable, well-understood maneuver (particularly for a computer)

Can you explain the reasoning behind this comment? Chris was discussing "reliability" and abort scenarios. I'm not aware of any mainstream autopilot system that is capable of even an unpiloted emergency landing after a single engine-out, let alone an all-engines-out emergency glide.

I was contrasting it with Falcon 9's hoverslam, which strikes me as a highly tuned accident waiting to happen, with a first-try engine restart on the critical path.  I can imagine the control problem becoming well enough understood for robust performance, but I don't like that engine restart.

No one was discussing abort scenarios until I brought them up.  And who said anything about all engines out?  At least Skylon has a chance in that scenario; Falcon 9 sure as hell doesn't...

Losing one engine is a much more likely scenario (and REL have specifically sized the tail fin to deal with it).  With one engine, you've got options no matter where you are, even if you can't make orbit.

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historically liquid hydrogen systems haven't been as reliable as systems using other sorts of fuel.
Centaur      Expendable
Saturn V     Expendable
DC-X          Suborbital experiment
Ariane 5      Expendable
Delta IV      Expendable
STS           Expendable hydrogen tank, very expensive and high-maintenance engine.
...

Not sure what this list tells you about the reliability of reusable hydrogen rockets.

Not sure why you expected it to tell you anything about the reliability of reusable hydrogen rockets specifically.  Chris was talking about hydrogen vs. other fuels in general.  What the list shows is that there doesn't seem to be a significant effect on the probability of vehicle failure.

All the same, it does tell you something about reusable engines.  One thing it tells you is that the RL-10 is pretty great - the fact that DC-X was a "suborbital experiment" notwithstanding...

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I agree that advocates are grossly underplaying Skylon's complexity and risks

How so?
« Last Edit: 11/08/2015 04:44 AM by 93143 »

Offline TrevorMonty

Re: The Reaction Engines Skylon Master Thread (5)
« Reply #814 on: 11/08/2015 06:16 AM »
It maybe possible to build and flight test the Skylon without a finished Reaction engine. Existing rocket engines or Reaction engine in rocket mode should provide enough DV to take airframe through the riskier parts of flight envelope.

Even better/cheaper build a subscale version using existing rocket engines. These don't necessary need to be hydrogen fuelled engines either.
« Last Edit: 11/08/2015 06:27 AM by TrevorMonty »

Offline A_M_Swallow

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #815 on: 11/08/2015 08:56 AM »
It maybe possible to build and flight test the Skylon without a finished Reaction engine. Existing rocket engines or Reaction engine in rocket mode should provide enough DV to take airframe through the riskier parts of flight envelope.

Even better/cheaper build a subscale version using existing rocket engines. These don't necessary need to be hydrogen fuelled engines either.

Existing rocket engines would allow the Skylon's ability to take off, change course, navigate and land to be tested. Four things less to worry about when the SABRE is added.

Offline knowles2

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #816 on: 11/08/2015 11:29 AM »
It maybe possible to build and flight test the Skylon without a finished Reaction engine. Existing rocket engines or Reaction engine in rocket mode should provide enough DV to take airframe through the riskier parts of flight envelope.

Even better/cheaper build a subscale version using existing rocket engines. These don't necessary need to be hydrogen fuelled engines either.
Not cheaper to the overhaul project through. Whether a subscale model is needed will probably be decided when they have built and tested a full scale sabre engine of the ground. If that engine manages all stages of the flight without any major malfunctions or unexpected issues popping then I suspect they will go for a full scale model, if unexpected issues pop up then they might go for a subscale model. But this will be for testing Sabre engines not simply to test whether skylon model can fly with rocket engines or jet engines attach to it they will use computer simulations for that, which I'm sure they have already done.


An one person above mention costs. Cost per flight is expected to be just 5 million quid, they add 5 million for cost of acquiring Skylon presuming it will still cost 1 billion per unit but I suspect prices there will full as they introduce more 3d printed components,  and they could add another 5 for their profit and still be less than half the price of Falcon 9 whilst potentially being a lot more flexible in the missions it is able to carry out. 
« Last Edit: 11/08/2015 11:40 AM by knowles2 »

Offline Katana

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #817 on: 11/08/2015 01:59 PM »
Orbital reentry of razor-thin tank airframe is something with "razor-thin margins".

Unless somebody reentry and reuse an upperstage before Skylon.

No matter with engines.
« Last Edit: 11/08/2015 02:07 PM by Katana »

Offline TrevorMonty

Re: The Reaction Engines Skylon Master Thread (5)
« Reply #818 on: 11/08/2015 02:07 PM »
Alan Bond said it would cost £350 to get finished engine. £10B to produce Skylon and engines, I think this is large scale manufacturing.

Going from finished engine to flying prototype Skylon would still cost a few £B.
« Last Edit: 11/09/2015 04:10 AM by TrevorMonty »

Offline Katana

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #819 on: 11/08/2015 02:28 PM »
Subscale models are needed to prove intact vehicle reentry from orbit.

Unless you want to try it with a full scale "reuseable" but really expendable vehicle.

F9R is cheap enough to start from F9 expendable, is Skylon also cheap enough to start from expendable?

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