back to article ESA: British Skylon spaceplane seems perfectly possible

Good news for spaceplane fanciers today, as a new report issued by the European Space Agency (ESA) says that "no impediments or critical items have been identified" which could block continuing development of the radical British-designed "Skylon" orbital craft. Many Reg readers will be familiar with the Skylon, modern-day …


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  1. Anonymous Coward
    Anonymous Coward

    I say get the fudge on with it

    The sooner we can have a go at getting one of these Thunderbirdish spaceplanes running the better.

    Perhaps its just the fact that it's a natural shape for a highspeed aircraft but it reminds me of the Arvo 730 design

  2. Richard Ball
    Thumb Up

    Liking the music

    I say HAL, would you mind awfully opening the pod bay doors?

    1. Anonymous Coward

      Quite right too

      "The sooner we can have a go at getting one of these Thunderbirdish spaceplanes running the better."

      Interestingly enough (I'm on the sauce), Gerry Anderson's Supermarionation setups (*) were generally set 100 years into the future (check out TV21 and the dates). At the rate things are going, things would lead to a setup where we would have spaceplanes around that time.

      It's one of my saddest realizations that I won't be around to see it :-(

      (*) Fireball XL5, Stingray, Thunderbirds, Captain Scarlet - not sure about Joe 90...

      1. nyelvmark


        Well, I'd like to see it, too, though hopefully the real thing would be a bit less jerky.

        Except Tintin, of course.

    2. John Smith 19 Gold badge


      "I say get the fudge on with it "

      You are Fred Goodwin and I claim my free lifetime unlimited overdraft facility at RBS.

  3. Alister Silver badge

    It's a shame...

    That like a lot of truly innovative ideas from British designers and Engineers in recent history, this will probably need massive private investment or foreign support to actually come to fruition.

  4. Getter lvl70 Druid Silver badge

    Leave it to the British

    To come up with such a cool name while combining two negative terms - Skynet and Cylon - and then paint it black. Fun to be had by all...


    1. Nigel 11

      Cool name

      the cool name predates Skynet and Cylon - it was given to a purposeless buy eye-catching structure at the festival of Britain in 1951. This beast's fuselage is much the same shape.

      1. Getter lvl70 Druid Silver badge


        The folks working on this project were most likely born around that time and thereafter, while Skynet and Battlestar Galactica occurred in the seventies and eighties. 'Recent' memories from a generational point of view would be more prominent in determining the name source.

        Or, I could just be talking out of my ass from this side of the pond and you're absolutely right.


      2. Julz

        The title is required, and must contain letters and/or digits.

        I think it's probably named after the 1951 festival of britain structure:

      3. Simon Harris Silver badge


        Actually, the British can lay claim to Skynet too...

        Before it got its sinister association with a rather large Austrian, it was also the name of a series of British military satellites, first launched in 1969.

    2. Philolai

      Write to the government/your MP

      I'm quite tempted to write David Willets MP, who has ministerial responsibility for space, to encourage him to ensure that everything is done to support the project and keep it in the UK. One letter isn't going to make much difference but if he started getting letters from people and MPs all over the country about this it might help.

      1. BenR

        More to the point

        It's £12billion quid.

        Isn't that about the amount the country is spending on the world's biggest school sports day... sorry, sorry... Olympic Games?

    3. Christoph Silver badge

      Names the Brits use

      I once saw a painting of the old HOTOL concept. where the artist had even included the name of the individual vehicle.

      It was, of course, "Anastasia".

  5. laird cummings
    Thumb Up

    Worth doing

    Even it it never gets off the ground, the value of all the primary research and engineering will translate to many other projects. Knowledge of that sort is never wasted.

    Carry on smartly, lads!

    1. John Smith 19 Gold badge
      Thumb Up

      @laird cummings

      "Even it it never gets off the ground, the value of all the primary research and engineering will translate to many other projects. Knowledge of that sort is never wasted."

      Actually *most* of the research to get here has *already* been done.

      RE's has partnered with *many* companies and universities (both in the UK and the rest of Europe) through its own funds and with EU funding (and *very* occasionally UK govt funding) in some cases to *prove* the various elements.

      The *big* costs come from scaling up these lab trials, FEA simulations and prototypes to a *full* size vehicle.

      I personally would like to seem them investigate premixed catalytic ignition to eliminate a high temperature/high voltage ignition system but that's not a necessity.

  6. Mike Richards Silver badge

    Twelve billion? Cheap at twice the price.

    For that investment we could create thousands of high technology jobs, countless spin-offs and grab a lucrative market. It's almost petty change when government spending is concerned.

    We're going to spunk three times as much on the next generation of Trident submarines and it's only a little more than next year's running and jumping show.

    1. Anonymous Coward
      Anonymous Coward

      That is one third of Lloyds bailout

      Another way of looking at it - 1/3rd of bailing out Lloyds.

      1. Anonymous Coward

        Speaking of bailouts

        As an Eurozone reader I'd rather be paying for a tech project like this than bailing out UK banks' lousy investments in Portugal and Greece, as I am doing now.

  7. Michael H.F. Wilkinson Silver badge

    May I be the first to

    Welcome or Skylon overlords

  8. Anonymous Coward
    Anonymous Coward

    The New Concorde

    to Falcon's 747 Jumbo Jet.

    Some undoubtedly amazing technology, but it will cost a fortune and never make a profit, while the Americans clean up in the commercial space launch business with cheap, reusable rockets that can actually a) carry a useful payload and b) reach a useful orbit.

  9. Anonymous Coward

    yeah but...

    I'd like to see how it handles the ash cloud!

  10. Bronek Kozicki Silver badge


    construction of fuselage able to stand the heat (without too much ablation), light enough and providing necessary isolation to keep the liquid hydrogen safe, all at hypersonic speeds is going to be a problem. I wish them best of luck with this (and with the engine).

    1. John Smith 19 Gold badge

      Bronek Kozicki

      You might not be aware of this but RE was formed in 1989.

      BTW your comment about ablation indicates you have no idea how they operate. RTA or their website.

      It's been around for about 20 years.

      1. Bronek Kozicki Silver badge

        John Smith 19

        I did checked their website and found rather novel proposed solution "Separate ambient structure" in

        I'm still pondering how does this relate to "how they operate", care to enlighten me?

        1. John Smith 19 Gold badge

          @Bronek Kzicki

          "I'm still pondering how does this relate to "how they operate", care to enlighten me?"

          The question is ambiguous.

          On the assumption you mean how the *structure* operates it splits the loads being carried into different types. A more detailed explanation follows.

          "airstream" loads are carried by the skin.The skin is currently spec'd as a French ceramic called "Pyrosic" in the updated PDF, and is mostly a Silicon Carbide. Like parts of the SR71 it is corrugated parallel to the direction of airflow. It is joined to the load bearing "ambient" structure by "hairpin" rivets. The skin is c800c hotter than the frame. It can be made airtight (unlike the SR71, whose outer skin served as the wall of the fuel tanks) because the heating is partly re-emitted into the airstream (like the tiles on the shuttle) but also partly absorbed "flattening" out the corrugations on the surface and stretching the hairpin rivets underneath. All should be *poor* thermal conductors.

          What you might not realize is although skylon is airtight it is designed to be *vented* (also much like the shuttle, which has 16 motor controlled vents to do so). The air is sucked out by the surrounding air pressure on ascent and *stays* out when the vents close. This eliminates convection, and mounting the skin structure on low conductivity pins stops *most* conduction into the interior while encouraging its re-radiation outward. That leaves thermal radiation.

          Radiation is dealt with using multi-layer insuation. This is standard kit on satellites and some launch vehicle stages. The interleaved inorganic mesh layers prevent heat conduction while the metal foils reflect any IR from the back face of the skin back outward to it. It's the lightest known form of insulation *provided* you have a reliable vacuum.

          The surfaces of the tanks are coated with a layer of polyurethane foam with an SG of 0.06 to a thickness great enough to prevent water condensation on their outside. This would be far too fragile to coat the outside of say the Shuttle ET but is adequate because it's protected from airflow.

          Using *multiple* structures in this way is very different from a conventional vertical takeoff rocket.

          "Static" loads (tank weight and engine thrust) are carried by the "truss" frame, sitting inside the MLI layer.

          With MLI keeping the heat *out* and polyurethane foam keeping the cold *in* the frame can be made of materials that are strong at *near* room temperature without worrying about their high temperature strength properties..

          The frame is made of unidirectional laid carbon fibre tubes fitted into titanium fittings made in 2 halves and "flash" welded together for speed and to retain good materials properties with a very thin heat affected zone. This work was done under an EU grant at IIRC Bristol University some years ago. Note that with modern plastics near room temperature *can* exceed 250c (the maximum use temperature on the Aluminium skin of the shuttle is 183c).

          By "floating" the skin away from the tanks and non airstream load bearing structure from day 1 RE aim to side step the pitfalls of the tightly integrated Shuttle structure of stressed skin (distorting under thrust and gravity loads) stressing (or rather over stressing) the brittle ceramic tiles. In principle with the Pyrosic panels floating and thin they should *bend* on minor impacts rather than shatter. While they wouldn't survive being hit with foam of an SG of say 0.2 at M3 they are also not likely to have a *source* foam anywhere near them either.

          The 4 tanks are designed to be rigidly mounted at one end and carried in a series of Kevlar "slings" to they are free to grow and shrink under temperature loads without high deformation forces building up. This is not clearly shown in *any* RE diagram.

          While the truss structures has never AFAIK been tried in carbon fibre tubes it has a long history in UK airship and bomber design, mostly by Barnes Wallis.

          Rivet joined plates remain a common aircraft construction method and the idea of hairpin rivets IIRC was one approach to the design of the X20 Dynasoar, although the material of these plates and the rivets would be viewed as exotic by mainstream aircraft manufacturers.

          It *should* also be capable of a high degree of automatic assembly, even if the individual tube insertions and panel riveting were fairly slow.

    2. Anonymous Coward
      Anonymous Coward

      Why does everything need to make a profit?

      This is what bugs me about our species. Half of us are only interested in money, the other half on mindlessly passing the time watching a load of irrelevant rubbish on TV.

      A few great geeks out there are the shining lights of our species and it is them who will be saving us come the deadly asteroid or other cataclysmic event.

      We should be building these things for the sake of building them - to better our species - with the end goal of getting us into space so that we can, should we have to, travel to another habitable planet.

      Money has no more value than what we place on it.

      1. Captain Thyratron

        How wouldn't it?

        It takes some incentive to get a whole bunch of people to work on some other guy's idea, and it should. I mean, really, if your neighbor told you "Hey, come to my house and I'll have you manufacture something that's really hard to make, and might not even work, in exchange for a nothing but a vague ideological pat on the back", you'd probably tell him "no" or some florid analogue thereof.

        Glittering vagaries about the betterment of humanity through difficult aerospace projects do not get them built. Work gets them built, and only suckers and prisoners work for nothing. A neat-sounding idea of yet-undetermined feasibility does not automatically deserve a team of engineers and a fat government research budget.

        1. Anonymous Coward
          Anonymous Coward


          "It takes some incentive to get a whole bunch of people to work on some other guy's idea, and it should."

          Really? Because Linus Torvalds had an idea ... and he didn't even need to ask, he just published and made available. That is the difference between those great geeks and the rest of the world. The challenge is the incentive.

          "Work gets them built, and only suckers and prisoners work for nothing."

          That is exactly the mindset that is holding us back. You're essentially calling every unpaid open source programmer a sucker - do you honestly believe that?

          But the point is a lot of advancements in technology/science are discovered accidentally through some failed project/experiment - that is the value of this project.

          1. John Smith 19 Gold badge


            "Really? Because Linus Torvalds had an idea ... and he didn't even need to ask, he just published and made available. That is the difference between those great geeks and the rest of the world. The challenge is the incentive."

            No that's the difference between computer software running on *widely* available hardware and fabricating high performance *physical* components in the real world.

  11. BristolBachelor Gold badge

    Liquid O2

    Now I thought that the tanks holding liquid O2 on normal rockets could only do so for a short time, as the stuff is nastily corrosive. If you've ever seen a lanch scrubbed, you will know that they spend ages filling the tanks just before launch, and if it's scrubbed, they take it back out pronto to protect the tanks.

    So what happens if you want to re-use the same tank for every launch (something that I think has not been done before) ?

    1. John Smith 19 Gold badge


      "Now I thought that the tanks holding liquid O2 on normal rockets could only do so for a short time, as the stuff is nastily corrosive."


      Current LO2 and LH2 tanks are loaded with propellants at Normal Boiling Point. It take *very* little heat input to start their contents boiling.

      Either the tank pressure starts rising (GO2 is roughly 700x the volume of LO2) fast or the tanks starts venting, dumping a very effective oxidiser into the environment where it could turn any stray spark into a fireball.

      RE is planning to operate a Zero Boil Off tanking arrangement (something NASA has repeatedly looked at but not got around to doing. This "Sub cools" both propellants *substantially* increasing the time a Skylon can stay on the runway before taxiing off.

      As for "corrosive" LOX is one of the most *common* cryogenic liquids in the world. Every major hospital uses it, along with many steel processing plants, not to mention its routine transport by road tankers and freight cars on railways.

      If you were talking about Flourine, NTO or any of the Amines you'd have a point.

      They are *very* nasty.

      1. sT0rNG b4R3 duRiD

        Liquid oxygen.

        There may be a significant difference in oxygen tanks used in rocketry and that in more terrestrially bound applications.

        Perhaps mass would have a lot to do with this, and I do vaguely recall lighter metals tend to oxidize a lot easier.

        It may be that rockets have much thinner tank walls made of lighter alloys....

        But I'm no rocket scientist, so if you know better feel free to correct this.

    2. Mike Richards Silver badge

      Not corrosive - but...

      Liquid O2 will make almost anything burn. In the 1950s the Americans had a number of nasty fires and explosions when liquid oxygen boiled out of their Thor missiles and dripped on to asphalt.

  12. Pete 2 Silver badge
    Gates Halo

    Being unmanned is the key

    That's really where the scuttle went wrong (the Soviets managed it, with their Buran: who's one and only flight and landing was handled autonomously by the on-board AI).

    Without the weight overheads of people and all the inconvenient stuff they must bring along,, the cost goes down considerably. Likewise, the preflight checks don't have to meet human-standards of safety, so there is a possibility that one of these, could be turned around in a few days.

    I just wish the development cycle for this could have been measured in years, a la Apollo, rather than the decades it's taken so far and another one to get something onto a runway.

    1. John Smith 19 Gold badge

      @Pete 2

      "That's really where the scuttle went wrong (the Soviets managed it, with their Buran: who's one and only flight and landing was handled autonomously"

      Part of the *implicit* design criteria were "Must keep astronaut corps fully employed for conceivable future."

      At least 1 supplier proposed a 2 stage winged design with the first stage uncrewed (the mother of all RPV's). Marshall stated "No unmanned stages."

      Shuttle has *always* had the ability to autoland but required someone on board to throw certain switches (like the ones that drop the landing gear. It cannot be retracted and kills the glide speed. NASA did not want that on direct computer control). There is now a cable that can wire up/bypass all the manual bits as well.

      Pilots refuse to engaged auto land stating it's feel is too "different" and they don't think they could get used to the difference in an emergency. Besides which if you'd practiced for 5 years to land the worlds fastest aircraft you'd probably want your shot at it when the time came.

      " by the on-board AI)."

      Not even necessary. Just carefully worked out logic, much like the autoland function on commercial aircraft.

      Bear in mind the Shuttle is unstable. It *cannot* fly without computer intervention and working hydraulics. There is *no* mechanical backup (This is why the landing simulator scenes in the film Space Cowboys are hilarious). Once you're committed to *that* much automation the rest is just more code.

  13. Anonymous Coward

    Geostationary Orbit

    I don't think that any rockets actually go to GEO orbit. They normally release the satellite into a GTO (GEO Transfer Orbit). Normally this is the work of the last stage of the rocket, and for example was a separate thing in the case of the shuttle. Actually getting from GTO to GEO orbit was always the job of the satellite (and the fuel for that might be a good proportion of the satellite launch mass).

    If we assume that this part is not re-usable, then it's probably not much different than the 3rd stages currently used by lots of people and shouldn't be too much of a problem (as far as rocket science goes!). Making it non re-usable means that you don't have to decelerate it and control it's re-entry to make it survive, whcih would double the amount of fuel it would have to take up.

    1. David 164 Bronze badge

      They are developing a other vehicle to boost cargo into GSO orbits.

      I believe reaction engines are working on a fully reusable craft able to handle cargo transfere from LEO to GEO. The craft would stay permanently in orbit, to either boost satelites to the require orbits or to refuel them why in orbit. The craft would be service and refueled by Skylon while still in orbit.

      There been some suggestion that if something goes wrong with there development of theSabre engine, that development of this craft could still go ahead. But with the launch vehicle would be change to a Falcon 9 or a other launch system.

      The costs of developing this vehicle is also included in Skylon costings at least the one produce by the ESA review which was release today. As it is consider essential to make Skylon economically feasible.

  14. My-Handle

    SABRE's key tech

    This article itself points out that the SABRE engine is essentially the pre-cooling rig bolted to a hydrogen rocket (I'm sure it's a little more complicated than that, but bear with me). The big question is: can this tech be bolted to one of SpaceX's Merlin rockets? A fusion of these two techs would be a big step for space-planes! No need to carry that bulky hydrogen.

    1. John Smith 19 Gold badge


      "The big question is: can this tech be bolted to one of SpaceX's Merlin rockets?"

      No. Lewis might *call* it a bolt on but it's an integral par

      A fusion of these two techs would be a big step for space-planes!

      Totally different approach to the problem. RE's nearest *potential* partner in the US (If it *wanted* a US partner, which it does not) would actually be Xcor Aerospace.

      No need to carry that bulky hydrogen."

      Hydrogen is a *key* enabling component of the design. No Hydrogen. No Skylon.

      Here is (roughly) the engine schemeatic.

      See if you can work out where to cut it to drop in the Merlin 1d engine.

    2. annodomini2


      The liquid hydrogen is used to provide the energy sink for the pre-cooler, the helium is an indirect medium.

      The liquid oxygen is used to cool the rocket engine.

      Cryogenic fuels are a critical component of the design.

  15. Anonymous Coward

    Bang for Buck

    Anyone fancy a futures contract on the film rights to the first Skylon accident (provisional title: The Big Bang).

  16. F111F

    CG Issues

    Since the thing is mostly fuel tanks fore and aft, it will be interesting to see how they manage to maintain CG (Center of Gravity) as it burns the fuel.

    1. John Smith 19 Gold badge


      "Since the thing is mostly fuel tanks fore and aft, it will be interesting to see how they manage to maintain CG (Center of Gravity) as it burns the fuel."

      Pretty much the way some of the RE design team solved it on Concorde.

      Look at the cutaway diagram.

      Each propellant is stored in *two* tanks. 1 in front of the payload bay, 1 behind and note that LO2 is roughly 16x more dense than LH2.

      Controlling *which* tank each propellant is drawn from matches most (if not all) of the CG shift.

      BTW the design is designed to be statically stable so the control surfaces do not have to flutter about continually like the Shuttle during a landing.

    2. SkippyBing Silver badge

      What problem?

      Take fuel from the forward tanks for one engine and aft tanks for the other and the CG will stay in the middle, strangely about where the wings are.

      I'm guessing it may be slightly more complicated e.g. connecting both tanks to both engines in case there are problems getting it out of one of the tanks, but it seems to be designed to keep the CG in the middle unless you do something really stupid like only take fuel from the front tank.

    3. foo_bar_baz

      I'd also like to add

      This is no different from airplanes that have fuel tanks in the wings.

      Unless I'm mistaken they even have pumps to move the fuel from a tank to another.

  17. Richard Ball

    Interesting launch trajectory

    Am I right in thinking that's an 'unusual' trajectory for a launch to orbit, in that it's getting steeper at the top instead of shallower...?

    Damn Korean animators - obviously need poking with sharper bayonets to sort out their ideas.

    Icon chosen with more irony than I realise?

    1. Nick Thompson


      Normal rockets want to get up into space as quickly as possible where the air resistance is lower. This space plane will want to stay as low initially so that it can continue to use the oxygen in the atmosphere. When it gets fast enough the air resistance will be high enough that it is more efficient to get out of the atmosphere and use internal oxygen. At this point it will want to climb rapidly. So the trajectory in the video is probably right.

  18. Anonymous Coward

    Someones being playing a lot of elite.

    As is only right and proper.

  19. John Smith 19 Gold badge
    Thumb Up

    RE don't *want* a governmet handout.

    The reason they have costed it at £12Bn is because they are looking to fund it as a *commercial* venture as in a *commercial* investment based on current estimates of the market.

    No government subsidy.

    Operators *buy* the vehicle, unlike the present system where you buy a ticket to ride an *expendable* launch vehicle. It works, all your money is spent.

    If it fails all your money is *still* spent.

    They believe there is a market for 30 of these vehicles and they will be in profit at somewhere *below* that.

    Just like a *real* company making real products

    As for most the questions of most posters. Look at their web site

    The answers to *most* of your questions will be found in the PDF's on this page.

  20. Marketing Hack Silver badge

    Why do we tempt fate so??!!

    You Brits are going to name your robotic spaceplane "Skylon"? Are you going to give it a cold, menacing synthesized voice that says "By your command" whenever you order it to do anything? And then of course the MoD is going to want a nuclear-capable military version with "enhanced autonomous decision-making". And when the resultant monstrosity gains self-awareness and starts bombing us from orbit, we're going to find that you guys forgot to build it with an "off" switch!

    I guess it's time to build my survival bunker.....

    1. Mike Richards Silver badge

      Only the beginning

      It'll be followed by the 'Mysteron' whose voice will have you soiling your pants right across the Atlantic.

      1. John Smith 19 Gold badge

        @Mike Richards

        I once worked for a guy for whom English was not a first language.

        Imagine a Mysteron who swears a lot.

        *Very* unnerving and quite sinister.

  21. BozNZ


    whatever happens, the goalposts have moved forward and at worst at least there will be some R&D and engineering happening in the UK for a change.

  22. lawndart


    @ Marketing Hack

    Can we help it if some Merkin takes a perfectly good British word and applies a negative connotation to it? I suppose we should be used to playing the bad guys.

    @ Anntoin

    Forget Elite, try the Orbiter space sim:

    You can even download Skylon for it and try it out. Then use it to construct space stations...

  23. trashbat

    I'm sure it's a lovely spaceship

    But what's it like to write with?

  24. Anonymous Coward

    I can see the future.....

    ...and in about 30 years time, Lewis Page will be lamenting a colossal UK/EU waste of money on this project and asking why on earth we had to build our own super-ambitious space vehicle when we could have just bought some poxy US rocket instead (which he will then produce some contrived and dubious evidence to argue is superior in every respect, and that this should have been obvious 30 years ago).

  25. This post has been deleted by its author

  26. John Smith 19 Gold badge
    Thumb Up

    This document is likely to be *critical* for fund raising. It's a major milestone

    Before it RE is a smallish company with a big idea.

    After it RE are a smallish company whose idea has been *thoroughly* investigated by competent auditors with *no* vested interest in it working. The auditors have looked at even the *secret* bits and concluded they work.

    This is the sort of hard nosed scientific deep cavity inspection that large scale investors *must* see in order to start signing cheques.

    It is an area where companies have failed because the few groups of people qualified to be able to make a judgment on someones capability in reality have a vested interest in them *not* succeeding.

    In the US it's known as the friend-at-NASA syndrome.

    Note that in a recent interview Elon Musk stated the total investment to date for Spacex was c$800m. Had he had to borrow *all* that money through the financial markets his bill would have been a *lot* higher and this is despite the fact that the technology is relatively (let me just repeat that word *relatively*) pedestrian, although its *implementation* is very advanced.

    RE's net worth is roughly 1/133 the size.

    I wish them every success. I believe that if they do get to market their estimate of 30 customers will go down in history with Thomas Watson Jnr's assessment that the world market for mainframes *might* reach 14.

  27. JeffyPooh Silver badge



    Requirements := Requirements + Surviving A Bird Strike*

    * Canada Goose, fired directly into the frost-proof helium-powered super-beer-cooler thingy at Mach 6-ish. If they can handle that, then that's A Very Good Thing (TM).

    1. BorkedAgain

      Canada Goose?


    2. Captain Thyratron

      Not that big a deal.

      I'm pretty sure most birds don't very much like the parts of the atmosphere where this thing is supposed to go that fast.

    3. annodomini2


      You just want the contract to build the cannon

    4. John Smith 19 Gold badge


      Funny you should mention that.

      I wrote to RE a long while back on that and a few other points.

      They kindly wrote back and explained that they *had* considered it and the design is *more* resistant to it than a conventional turbo fan or jet (I point out that's provided you defrost the goose first). They were a *lot* smaller then.

      In hindsight it would be a lot like a bird strike on an SR71 nacelle.

      Firstly there are 2 engines on each side so worst case would give a 50% loss of thrust balance. Secondly I'd guess the SABRE core site *directly* behind the entry cone. A bird strike would slide down the cone and hit the inlet but by pass the engine core, possibly clobbering part of the "Spill ramjet" (I'd guess they can isolate sections of the feed piping on this) before being flash broiled by the superheated steam on the way to the exit.

      Hitting the inlet heat exchanger matrix *would* be a very bad day for all concerned but I *suspect * you'd have to fire the goose at *just* the right entry angle to do so. In these cases I think civil aircraft certification bodies start breaking out probabilistic risk assessments, with the odds (of a mishap) lengthening as the inlet closes on ascent.

      99 times out of a 100, SABRE cooks the goose. 1 in a 100 (or rather less), the goose cooks the vehicle.

  28. John Smith 19 Gold badge

    Most comsats incorporate that final stage as part of *their* components

    The last rocket stage might *point* them roughly into the direction and a bit of delta V but the bulk is usually provided by something called an "Apogee Kick Motor".

    Historically it's been a big solid but for best performance you make the storeable propellant tanks on your satellite oversize. if the rocket has done a good job you get a *free* satellite life extension since you can keep it in its orbital box (comm sats are confined to a rectangular section of their orbit but they drift about it. Like a slow motion game of pong)

    Note although RE show satellite launch from a Skylon in a stable *orbit* it has a 2300Km cross range. A sub-orbital launch could put up a *very* big sat pointed in the right direction and with as much delta v as a regular launcher, leaving the AKM to finish the job.

    However a separate "tug" could be a *very* useful investment. Staying in space (ideally being re-fueled there), not taking up cargo pay space or mass on *every* flight it would deliver the idea of space as a "service" rather than a piece of hardware you *have* to acquire to fly your mission (in the way you have to buy a rocket to do so now).

    1. Bronek Kozicki Silver badge
      Thumb Up


      They published a study of such "tug", it's called Fluyt

  29. The elephant in the room


    If every human chips in 2 quid we can start building this thing tomorrow!

    (checking pocket for loose change)

    1. annodomini2


      Every UK resident chips in £20 a year

      They claim a 10 year development schedule

      Allowing for inflation

  30. John Savard Silver badge

    Not So Terrifying

    Right now, what the world needs is a new way to get astronauts to and from the ISS, so the fact that this vehicle is unmanned limits its importance. However, that is perhaps the only way it could be developed privately; a manned vehicle would need government funding, in the big way that only the United States might do.

    However, in addition to the sculpture from the Festival of Britain, the name "Skylon" has another positive association, as the name of a tower in which many a honeymooning couple has shared a restaurant meal - in Canada, overlooking Niagara Falls.

  31. John Smith 19 Gold badge

    @John Savard

    "Right now, what the world needs is a new way to get astronauts to and from the ISS, so the fact that this vehicle is unmanned limits its importance. "

    Not really.

    Uncrewed <> *incapable* of carrying passengers.

    It's a subject that RE have looked at as you can see in this report.

    The unmanned thing may be a bit of a red herring. But as the UK never built a crewed rocket they never worked out a man rating requirement either. Note the Shuttle is *not* crew rated either. The aspects it does not deal with are met with "waivers."

    I will observe that *not* being mated up to *huge* solid fuel boosters (which cannot be shut down in emergency) and a large tank with foam shedding issues ("mitigated" but not AFAIK *eliminated*) should put it head and shoulders above the Shuttle in the risky-features-we-cannot-do-much-about stakes.

    More to the point would be how the US and/or Europe view it's crew worthiness. However if there were *other* places to go who did not care about such distinctions that would not matter.

    Like an orbiting hotel for example.

    However RE are *very* cautious about market projections as they *have* to be given the budget they need. This is why they are *very* cautious talking about *anything* but communications satellite business, which is *the* paying segment.

    I will point out that a vehicle designed with a *very* small number of fluids (*the* key reducer of support costs on *several* NASA studies), basically LOX,LH2, hydraulic fluid and water, requiring *no* mating of components and with *no* on board crew *should* be able to substantially lower the price per Kg to orbit, given the propellant bill is roughly $1.68m. #

    The bill for the Shuttle's expendable tank is about $1m, but the tank itself is roughly $12m and it's single use. However that $1.68m does not count topping up the water tanks and replacing they pyros (not cheap. The Shuttle has several 100 on board, along with their ignitors, each at about $400).

    Unlike NASA RE has *no* standing army of people it's politically *required* to employ (and no desire to acquire one).

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