Author Topic: The Reaction Engines Skylon Master Thread (5)  (Read 441373 times)

Offline momerathe

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #760 on: 11/03/2015 08:14 PM »
Not if in the process SpaceX's costs go below those projected for Skylon.

Welp, the long game is cheap access to space - I don't care who does it. I personally have my doubts about just how low SpaceX can go, but I wish them luck. If they manage it, great! if they don't, maybe Skylon will.
thermodynamics will get you in the end

Offline 93143

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #761 on: 11/03/2015 08:30 PM »
I'd imagine that Skylon's launch prices would depend strongly on flight rate - probably more strongly than SpaceX's, since the system is fully reusable with a relatively high DDT&E cost and potentially very low processing overhead.  The current projection of $20M per flight is ten times the lowest number they've ever produced, which was for low-value cargo in an arbitrarily large market.

There are other advantages as well, such as the Shuttle-like on-orbit ops and downmass capabilities (without adding cost and reducing payload mass and volume by adding a capsule) and the very high projected reliability.  It's not really an apples-to-apples comparison, and even if SpaceX comes out cheaper, price may not be the only relevant market factor.
« Last Edit: 11/03/2015 08:56 PM by 93143 »

Offline Kansan52

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #762 on: 11/03/2015 08:55 PM »
"...and even if SpaceX comes out cheaper, price may not be the only relevant market factor."

Totally agree.

Offline TrevorMonty

Re: The Reaction Engines Skylon Master Thread (5)
« Reply #763 on: 11/03/2015 09:02 PM »
The one payload Skylon would be good for is delivering fuel. Especially if they can hit $1000kg mark as per their website. There are no fuel depots at present, but ULA and their distributed launch system offers hope here.

Offline ChrisWilson68

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #764 on: 11/03/2015 09:53 PM »
I'd imagine that Skylon's launch prices would depend strongly on flight rate - probably more strongly than SpaceX's, since the system is fully reusable with a relatively high DDT&E cost and potentially very low processing overhead.

Yeah, Skylon's very high development costs make its economics highly dependent on flight rate.

The current projection of $20M per flight is ten times the lowest number they've ever produced, which was for low-value cargo in an arbitrarily large market.

There are other advantages as well, such as the Shuttle-like on-orbit ops and downmass capabilities (without adding cost and reducing payload mass and volume by adding a capsule) and the very high projected reliability.  It's not really an apples-to-apples comparison, and even if SpaceX comes out cheaper, price may not be the only relevant market factor.

In terms of downmass, I agree Skylon might have an advantage.  It's not clear how much that will count in the market.  STS never carried much downmass, though things might change in the future and with much lower costs to orbit.

The "very high projected reliability" part, though, I completely disagree with.  There's no reason to actually think Skylon would have better reliability.  It's a paper rocket at this point, and no detailed design has been done, so there's little to go on for projecting reliability, but historically liquid hydrogen systems haven't been as reliable as systems using other sorts of fuel.

Offline pippin

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #765 on: 11/04/2015 01:49 AM »
Ummm... Development costs are sunk costs and so have no impact whatsoever on the operational economics.
Flight rate is important if you have high (operational) fixed costs like a standing army of engineers for maintenance, support infrastructure that needs to be operated and so on.

Offline ChrisWilson68

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #766 on: 11/04/2015 01:54 AM »
Ummm... Development costs are sunk costs and so have no impact whatsoever on the operational economics.
Flight rate is important if you have high (operational) fixed costs like a standing army of engineers for maintenance, support infrastructure that needs to be operated and so on.

No.  Development costs only become sunk costs after the money has been spent.

If at some point in the future the development has been completed, then we can consider development costs sunk and ignore them for purposes of determining business model feasibility.

Right now, they are absolutely not sunk costs.  They must be included in any analysis of the economic case for Skylon.

Offline 93143

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #767 on: 11/04/2015 02:30 AM »
There's no reason to actually think Skylon would have better reliability.

Sure there is.  It's the nature of the vehicle we're talking about, not the bolt supplier's testing practices.  You don't get multiple orders of magnitude on your loss-of-vehicle numbers by fiddling with the design details.

Skylon is more of an airplane than a rocket.  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 lands like an airplane (well, like a glider), which is a comfortable, well-understood maneuver (particularly for a computer) and doesn't put a main engine relight on the critical path with no time to troubleshoot if it doesn't work.  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 each production unit will undergo four test flights before delivery.  It is also an SSTO, which means 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.  And of course it's fully reusable, which means infant mortality should be way down.

As of March 2014, REL was targeting a 1% abort rate (similar to the loss rate for some of the better ELVs) and a 0.005% loss rate per mission, and based on earlier comments by Mark Hempsell they expect both those metrics to be much better in actual operation.  In other words, those are more like must-not-exceed numbers than optimistic projections.

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historically liquid hydrogen systems haven't been as reliable as systems using other sorts of fuel.

Centaur
Saturn V
DC-X
Ariane 5
Delta IV
STS
...

I don't see the problem, unless you're talking about niggling intermittent launch-delaying issues like the Shuttle's GUCP troubles or the Delta IV's sticky fuel valves, which aren't really the sort of thing I was talking about.  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).

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.  (Even so, note that Falcon 9 has already had more catastrophic engine failures than STS...)

Ummm... Development costs are sunk costs and so have no impact whatsoever on the operational economics.

They affect launch prices (not costs), because they affect the purchase price of the vehicles.  Skylon doesn't have thousands of years to pay back its development costs; there's a finite horizon within which you have to confine your economic analysis, and the development cost looms large in that context.

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.
« Last Edit: 11/04/2015 03:09 AM by 93143 »

Offline pippin

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #768 on: 11/04/2015 02:37 AM »
Development cost of course has to be taken into account NOW because now you do of course want your investment case to close.
And yes, of course you have to make sure you have a decent assumption on the flight rate.
But in case that assumption turns out overly optimistic at some point in the future after you convinced someone to pay for the development Skylon - at least the ones built - could still be profitable at a lower flight rate if operating costs are low.
Even the sales price will drop, you have big write offs, your investors lose their money but the ongoing project could still be profitable.

Offline 93143

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #769 on: 11/04/2015 02:57 AM »
That's true, I guess - it could turn out like Iridium, or Concorde.  I hope it doesn't - depending on the circumstances, it might imply that the market isn't as robust as we would like, and it would certainly deter future investment into similar systems (see Concorde), but at least the fallback does seem to exist for a system this development-heavy.
« Last Edit: 11/04/2015 03:12 AM by 93143 »

Offline pippin

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #770 on: 11/04/2015 03:11 AM »
Yea, but Iridium and Concorde were not doomed due to excessive development costs. Concord had excessive operating costs (it was still lossy after they wrote down all of the purchase costs) and Iridium was simply the wrong product for the market.
Eurotunnel would be a better example. Way over cost, investors lost most of their money but the whole thing is now highly profitable after writing off the initial investment.

The problem with a system like Skylon is that your actual market better be as predicted because otherwise you can't afford ongoing development and a system that doesn't see ongoing development will be dead at some point. But at least you can recover from excessive initial dev costs and you are not dependent on being able to up flight rates to recover excessive development spending or something like that.

Offline 93143

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #771 on: 11/04/2015 03:23 AM »
Concord had excessive operating costs (it was still lossy after they wrote down all of the purchase costs)

That's not how I heard it.  As I understand it, British Airways consistently turned a profit on it, and Air France's service was spottier but not exactly a loss leader.  Things went to pot after the crash (9/11 didn't help, nor did the recession, and they were looking at increasing maintenance issues anyway), but prior to that the vehicle seems to have been useful enough on its main routes to make up for the high operating costs.
« Last Edit: 11/04/2015 03:32 AM by 93143 »

Offline ChrisWilson68

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #772 on: 11/04/2015 03:40 AM »
There's no reason to actually think Skylon would have better reliability.

Sure there is.  It's the nature of the vehicle we're talking about, not the bolt supplier's testing practices.  You don't get multiple orders of magnitude on your loss-of-vehicle numbers by fiddling with the design details.

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.

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.  It's just too early in the process.  And the designers of these vehicles are always sure they will be much much safer.  But it's all nonsense.

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.

Skylon is supposed to go to orbit.  It uses airplane-like takeoff and generates lift like an airplane for part of its flight.  But it does other things that are not at all like any airplane we have experience with.  Its engines are supposed to be both air-breathing and rockets at different points in flight.  It's supposed to use liquid hydrogen and liquid oxygen.  It's supposed to go to Mach 25.  It's supposed to re-enter from Mach 25.  All very much unlike all the airplanes we have experience with.  It is all those things that give it much more risk than a typical airplane.

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.  For example, if Falcon 9 has an engine that is about to explode and destroy the main propellant tank, the Dragon abort system can pull the capsule away from the exploding main tanks.  Skylon can't do that.  If the Skylon main prop tanks are about to explode, nothing at all can be done.

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.

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.

Propulsive landings can be done anywhere there's a small flat area, not just on a runway.  They're much more flexible that way.  If Skylon loses propulsion, it has to get back to a runway, which isn't easy as it has a poorer glide ratio than a typical airplane, and even a typical airplane will often have trouble getting back to its runway to land if engines are lost at the wrong time (see the airliner that landed on the Hudson a few years ago).

Also, propulsive landings give more than one shot at an approach.  With a glider, if there's a sudden gust of wind and conditions aren't good, you still have to land.  In a powered airplane, there's the option to throttle up and go around, and airplanes use that option not too infrequently.  Gliders don't have the choice.  A Dragon doing a propulsive landing has the choice.  If there's a momentary gust of wind, it can throttle up, go up in the air, then settle back down again.

and doesn't put a main engine relight on the critical path with no time to troubleshoot if it doesn't work.

Dragon can land even if any one engine fails to light, and it has a backup parachute landing system.  So, even if the engines fail to light, it can still land safely.  Skylon has no backup -- it has to glide to a landing or it crashes disastrously.

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.

and each production unit will undergo four test flights before delivery.

Dragon can do exactly the same.

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!  That has to do with how much lift it generates.  Shuttle and Dream Chaser are not SSTO but they can also generate lots of lift on re-entry and get lots of cross-range.

Dragon can also wait out bad weather on orbit.  It doesn't need much cross-range capability to do that.  And Dragon can land in far more places than Skylon, so it actually has more flexibility there.

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.

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.

As of March 2014, REL was targeting a 1% abort rate and a 0.005% loss rate per mission, and based on earlier comments by Mark Hempsell they expect both those metrics to be much better in actual operation.

What they're targeting is irrelevant.  Shuttle was supposed to have much higher reliability than it actually had.  Vehicle designers always have rosier projections than the way things turn out in practice.  Mark Hempsell and the rest of the REL team don't actually have experience designing a vehicle and seeing it through to an operational launch system.  The REL team has a lot of experience doing research on engine components and writing slideware, not much on systems that actually become operational.

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.

Quote
historically liquid hydrogen systems haven't been as reliable as systems using other sorts of fuel.

Centaur
Saturn V
DC-X
Ariane 5
Delta IV
STS
...

I don't see the problem,

STS killed more astronauts than any other space launch system in history.  And it's an instructive lesson because at the time it was conceived, it was seen by its designers very much as Skylon is seen by its designers -- a radically different design, reusable, and the solution to make space launch much safer and cheaper than ever before.

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

unless you're talking about niggling intermittent launch-delaying issues like the Shuttle's GUCP troubles or the Delta IV's sticky fuel valves, which aren't really the sort of thing I was talking about.

Those sorts of things make the systems much more expensive.

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, but without the disadvantages of having to use liquid hydrogen (very low temperatures and hydrogen working its way into everything, causing leaks and embrittlement) and the disadvantages of having to be single-stage to orbit (so there is less margin available for safety).

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.

(Even so, note that Falcon 9 has already had more catastrophic engine failures than STS...)

No.  Falcon 9 has had zero catastrophic engine failures.  It has had one catastrophic structural failure.  It's not a catastrophic failure if the vehicle keeps flying and makes orbit.

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

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.  The word "cost" doesn't just apply to operational costs.

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.

because they affect the purchase price of the vehicles.  Skylon doesn't have thousands of years to pay back its development costs; there's a finite horizon within which you have to confine your economic analysis, and the development cost looms large in that context.

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.

In addition to Skylon's much higher development costs, 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.

Offline 93143

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #773 on: 11/04/2015 03:50 AM »
I'll get back to this later.  I can't spend the time now.  For now I'll just say that from a quick read-through, it seems you're going to great lengths to miss the point of several of my arguments, and making analogies that don't really hold if you inspect them.

And no one said anything about Dragon.  This is a launch vehicle comparison.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #774 on: 11/04/2015 06:30 AM »
The one payload Skylon would be good for is delivering fuel. Especially if they can hit $1000kg mark as per their website. There are no fuel depots at present, but ULA and their distributed launch system offers hope here.
Skylon was designed to be a general purpose transporter. It's core mission is sending comm sats to GTO.

Much lower price per Kg is a key enabler of many missions but where Skylon shines here is downmass

Quite a lot of countries can put stuff into space but only 3 (Russia, SX and ESA) can get it down.

That becomes very important if you want to carry people into space as for the foreseeable future they will also want to come back.
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline john smith 19

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #775 on: 11/04/2015 07:08 AM »
Yeah, Skylon's very high development costs make its economics highly dependent on flight rate.
No it's development cost, on a par with a similarly sized reusable aircraft, are highly dependent on it's mfg being able to sell enough of them .

It's customers economics depend on their flight rate, which depends on their business model.
Quote
In terms of downmass, I agree Skylon might have an advantage.  It's not clear how much that will count in the market.  STS never carried much downmass, though things might change in the future and with much lower costs to orbit.
How about the 7 astronauts it carried on pretty much every flight?
Quote
The "very high projected reliability" part, though, I completely disagree with.  There's no reason to actually think Skylon would have better reliability.  It's a paper rocket at this point, and no detailed design has been done, so there's little to go on for projecting reliability,
Perhaps you'd like to walk us through your logic on this. Most open minded people would say the reverse.
Quote
but historically liquid hydrogen systems haven't been as reliable as systems using other sorts of fuel.
There's a difference between developing an LH2 engine and operating it.

LH2 engines have been more difficult to develop but once in service have performed  as well as LOX/Kero or storable engines in terms of reliability.

Perhaps you could list some specific LH2 engine failures you have in mind? SSME has never failed in flight operation, the first Ariane 5 was a GNC fault and AFAIK the original J2 never had trouble starting when attached to a vehicle.
« Last Edit: 11/04/2015 07:20 AM by john smith 19 »
"Solids are a branch of fireworks, not rocketry. :-) :-) ", Henry Spencer 1/28/11  Averse to bold? You must be in marketing."It's all in the sequencing" K. Mattingly.  STS-Keeping most of the stakeholders happy most of the time.

Offline momerathe

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #776 on: 11/04/2015 07:30 AM »
Do we really have to go over this again? is there anything that hasn't been said a hundred times before in these threads?

I for one would rather concentrate on the news, not rehashing old arguments.
thermodynamics will get you in the end

Offline francesco nicoli

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #777 on: 11/04/2015 10:12 AM »
I'd imagine that Skylon's launch prices would depend strongly on flight rate - probably more strongly than SpaceX's, since the system is fully reusable with a relatively high DDT&E cost and potentially very low processing overhead.  The current projection of $20M per flight is ten times the lowest number they've ever produced, which was for low-value cargo in an arbitrarily large market.

There are other advantages as well, such as the Shuttle-like on-orbit ops and downmass capabilities (without adding cost and reducing payload mass and volume by adding a capsule) and the very high projected reliability.  It's not really an apples-to-apples comparison, and even if SpaceX comes out cheaper, price may not be the only relevant market factor.

A fundamental issue, both for SpaceX_R and Skylon launch costs, is the pricing of the competitors. To decrease actual costs to space you need at least two companies with reusable vehicles: one will not do the trick: if only one company reaches reusability, it will just set the price an inche below the competitor's best price and get all the market it can.
A second company is needed to get the competition you want: in a market environment, technology alone does not drive costs down. tech*companies does.

Offline francesco nicoli

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #778 on: 11/04/2015 10:14 AM »
I'd imagine that Skylon's launch prices would depend strongly on flight rate - probably more strongly than SpaceX's, since the system is fully reusable with a relatively high DDT&E cost and potentially very low processing overhead.

Yeah, Skylon's very high development costs make its economics highly dependent on flight rate.


only for a private operator. a public operator would still enjoy very low costs and have the infrastructure ready when it needs so (eventually) in the future.

Offline Paul451

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Re: The Reaction Engines Skylon Master Thread (5)
« Reply #779 on: 11/04/2015 01:24 PM »
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 suspect bleeding-edge automation is pretty close, but it's certainly not something that can be called "comfortable, well-understood". And the decisions in a true emergency landing, ie when an airport is too far away, is beyond even those experimental systems.

Quote
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.

Dragon can also wait out bad weather on orbit.  It doesn't need much cross-range capability to do that.

Skylon can also wait in orbit before re-entering. Plus Skylon can fly around weather during launch, and fly to launch windows after a delay, making it much more responsive to customers. Fuel use during the subsonic jet-coast phase will be trivial. (A fully loaded 777 will only burn a tonne of fuel every 5hrs or so, for example.)

In a powered airplane, there's the option to throttle up and go around, and airplanes use that option not too infrequently.  Gliders don't have the choice.  A Dragon doing a propulsive landing has the choice.  If there's a momentary gust of wind, it can throttle up, go up in the air, then settle back down again.

I haven't heard, and don't believe, that Dragon has such a capability. It's a high commitment landing system. Do you have any references that suggest otherwise?

I agree that advocates are grossly underplaying Skylon's complexity and risks, but exaggerating in the other direction isn't the answer.

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