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Thread: How far into the future? An aircraft that launches from a runway and enters low

  1. #121
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    Quote Originally Posted by neilzero View Post
    The shuttle was too heavy to land on most of the runways of the world, so a similar design would need less payload capabilities to make it runway compatable.
    Possibly the passenger airlines would convert to vertical take off and land except for the huge investment in the present system. Vertical does have some important advantages.
    SSTO = single stage to orbit assumes LEO = low Earth orbit. Why do we want a stopover in LEO if we are going to solar sychonous orbit or almost anywhere else? Unless there is a good reason, let's forget LEO as craft designed for elsewhere can generally make a delivery to low Earth orbit, enroute to somewhere else. If the first stage leaves the atmosphere traveling vertically at 10 kilometers per second, won't a modest ion engine get us almost anywhere, by the shortest and quickest possible route, if it has enough ejection mass? Neil

    The shuttle is a bad baseline for making an SSTO. it's a high density blunt body with the flying capability of a slightly rounded brick. Vertical may have advantages for getting to altitude quickly with a vehicle that is never going to land, but once you want a reusable runway lander you are already adding wings and wheels. not using them to allow a lower T/W ratio at takeoff is wasteful in that case since engine mass is a major mass contributor to the vehicle as a whole.

    you either go vertical all the way, or you go horizontal all the way. both can have unpowered soft landings, and both share approximately the same vehicle mass per unit mass payload despite having wildly different trajectories. what you add in mass with wheels and wings you mostly get back with needing much smaller engines due to not having to support the initial take off mass of the vehicle on thrust alone. Sloping ascent is also a necessity for air-breathing propulsive stages.

    What really closes the case for wanting horizontal launch tho is the flexibility of being able to use a flexible multipurpose runway to launch your vehicle instead of a specialized launch gantry. There are huge cost savings in sharing infrastructure between different users with differing, but still similar needs. the runway can easily double as a runway for normal air traffic when not in use by skylons.

    The skylon spaceport is basically just an airport with added LH2/LOX refueling capability and a strengthened runway for skylon takeoff's. the skylon can land on any old runway on the way home since the vehicle itself is indeed light enough to not need especially strengthened runways on landing. it has burnt off all it's fuel after all.
    There are good reasons for not wanting to go vertical on airliners, and almost all of them has to do with the economics of flight and ground handling to do. it's just so incredibly much easier to handle a vehicle that can be towed into the hangar for maintenance, and that can roll onto the takeoff field under it's own power during departure.
    For an RLV to be economic it has to be capable of airliner like operations. otherwise it becomes just another rocket that needs a ton of supporting infrastructure and people in order to launch.

  2. #122
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    Quote Originally Posted by ravens_cry View Post
    Since those other things have not being built, we don't know their safety margins.
    The things that killed the astronauts were not inherent in the design of the space shuttle, or of rockets in general, but because of safety problems in procedures, management ignoring problems that arose.
    O-Ring problems showed up before Challenger and her crew met their doom for example.
    I would argue that indeed they are inherent. You have to get the velocity to 18,000 mph for LEO. That means a big rocket. And you have to brake that object to bring it home. Both problems are inherently dangerous, and unforgiving. As any Quality Engineer can tell you (and I have been an ASQC certified one), humans will make mistakes.

    Regards, John M.
    I'm not a hardnosed mainstreamer; I just like the observations, theories, predictions, and results to match.

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  3. #123
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    Quote Originally Posted by swampyankee View Post
    Read more aviation history. Until fairly recently, it was pretty common for experimental test pilots to die in the line of work. On that basis -- which is, in my opinion, the right one for comparison -- the US Manned Spaceflight Program has done quite well.
    Christa MacAuliffe?

    By your argument, the Shuttles should have had a crew of one or two.

    Regards, John M.
    I'm not a hardnosed mainstreamer; I just like the observations, theories, predictions, and results to match.

    "Mainstream isnít a faith system. It is a verified body of work that must be taken into account if you wish to add to that body of work, or if you want to change the conclusions of that body of work." - korjik

  4. #124
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    The remaining responders I more or less agree with. We will need a capable LEO rocket system, if only to build alternatives. But for the long term, we need something different.

    Regards, John M.
    I'm not a hardnosed mainstreamer; I just like the observations, theories, predictions, and results to match.

    "Mainstream isnít a faith system. It is a verified body of work that must be taken into account if you wish to add to that body of work, or if you want to change the conclusions of that body of work." - korjik

  5. #125
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    Quote Originally Posted by John Mendenhall View Post
    I would argue that indeed they are inherent. You have to get the velocity to 18,000 mph for LEO. That means a big rocket. And you have to brake that object to bring it home. Both problems are inherently dangerous, and unforgiving. As any Quality Engineer can tell you (and I have been an ASQC certified one), humans will make mistakes.

    Regards, John M.
    We are a squishy species. there are no way around that. Everything we do incur risks. just getting out of bed put's us in danger. while some risks are bigger than others, they are no more unmanageable. safety is in the minds of the people doing the work, and designing the machines that help do the work we need done in order to get what we want to do done.

    The shuttles appalling safety record is squarely the blame of human beings. accidents don't just happen. they are not inherent in any particular endeavour over any other. they are the result of a chain of events, where if even one of the events is prevented the accident will have been averted.
    When something goes wrong we work to figure out how, and when we have figured out the how of the accident we change our designs and procedures to prevent this particular accident from happening again.

    Going to orbit requires a lot of energy. whenever we are dealing with something with a lot of energy, the consequences of failure tend to become more spectacular. but dead is dead. getting killed in a huge fireball on the launch pad, or by being run over by a car makes no difference. at any rate the odds of being run over by a road vehicle or even just falling in the bathroom and hitting your head too hard one morning are both much bigger risk factors than being blown up on a launch pad for the average joe.

    Those whose job it is to go into space know the risks they take beforehand. It is indeed their choice to do so. They are all volunteers. When one day space becomes a place where the merely well to do as well as the extreemely well to do are able to go then we are not going to stop them. it's their choice as well. just as some people choose to climb mountains, or dive into the ocean.
    I know lots of people whose job entails some pretty nasty risks. to be sure. some of my jobs have had me working on some pretty dangerous machinery in the past. I'm probably going to be working with such machinery again in the future.

    I for one would if given the oportunity go into space with a smile on my face. the odds of coming back home alive are not particularly bad.
    Mistakes are going to be made in the future as they have been made in the past, and humanity will hopefully learn from those as well, and continue to improve. but nothing will ever be completely safe. because everything we do is inherently unsafe if you think about it long enough.

  6. #126
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    Quote Originally Posted by John Mendenhall View Post
    Christa MacAuliffe?

    By your argument, the Shuttles should have had a crew of one or two.

    Regards, John M.
    It's not unusual for flight test aircraft to have five or six people on board: pilot, copilot, and several flight test engineers. For an aircraft like the A380, there are probably about 500 to a 1000 test flights (Airbus said the A380 had about 2500 hours of flight test). I could spend a few minutes ranting about NASA's idiotic optimism, in overselling the Shuttle's readiness, but I won't.

    Skylon only requires three or four major unproven technologies, so I'm sure that everything will go swimmingly well.
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  7. #127
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    It will be amazing to see a thing that heavy fly with a wing that small. Hmmm......

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    Quote Originally Posted by swampyankee View Post
    It's not unusual for flight test aircraft to have five or six people on board: pilot, copilot, and several flight test engineers. For an aircraft like the A380, there are probably about 500 to a 1000 test flights (Airbus said the A380 had about 2500 hours of flight test). I could spend a few minutes ranting about NASA's idiotic optimism, in overselling the Shuttle's readiness, but I won't.

    Skylon only requires three or four major unproven technologies, so I'm sure that everything will go swimmingly well.
    At least they have the sense to use a development program that aims to prove each technology separately before building an actual vehicle. and well. skylon is going to have 300 or so un-manned testflights or so before anyone is allowed to even considder putting humans on board.

    I do wonder what technologies you consider as the greatest risk in skylon. the precooler/engine is going to be, barring any accidents, pretty much a proven technology before any other major investements are made. something i think is a pretty sound plan from an investors point of view.

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    Quote Originally Posted by danscope View Post
    It will be amazing to see a thing that heavy fly with a wing that small. Hmmm......
    Rockets fly, and they have no wings at all.

    but i agree. seing a skylon in operation will be awesome beyond words.

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    Quote Originally Posted by Antice View Post
    I do wonder what technologies you consider as the greatest risk in skylon. the precooler/engine is going to be, barring any accidents, pretty much a proven technology before any other major investements are made. something i think is a pretty sound plan from an investors point of view.
    It could work, and everything else could work, and the cost of operation might still be higher than other options. I'd be happy to see them succeed, but I'm very skeptical that an air-breather will really have an advantage over a pure rocket for orbital flights.

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    Quote Originally Posted by Van Rijn View Post
    It could work, and everything else could work, and the cost of operation might still be higher than other options. I'd be happy to see them succeed, but I'm very skeptical that an air-breather will really have an advantage over a pure rocket for orbital flights.
    Well. it's suposed to give a propellant mass savings advantage, thus helping to close the SSTO case.
    a pure rocket SSTO, while not physically impossible is a rather dubious beast due to the insanely small dry mass ratio.
    skylon improves the dry mass ratio by saving more oxidizer mass than the mass of the added machinery to make a rocket airbreathing. That is if they make the SABRE engine work as advertized. it pretty much hinges on them getting that part right.

    there is no economic benefit in air breathing on it's own tho.. those precoolers are aparently eye wateringly expensive according to info from the skylon master thread over at nasaspaceflight.
    the economic benefits of skylon can only be realized by succeeding in making the skylon into a quick turnaround low maintenace RLV.
    That is the real goal. all that technological development is being done for that purpose alone.

    I'm not entirely sure if a rocket only SSTO RLV is actually even physically possible in a vehicle of a reasonable size. getting a expendable SSTO rocket is pretty much at the edge of the possible as it is. if any concept ever would have managed that trick it would have had to be the DC-X concept i think. I was a fan of that one too for quite some time. venturestar was a disapointment when it was chosen. mixing vertical and horizontal modes of operation is always dubious imho. and it hurts the payload capacity for little to no benefit in regards to operations.

    I believe the key to breaking the economics of launch costs is twofold.
    The first part is to stop throwing entire vehicles away. it's wastefull in the extreeme resource wise, and it has a pretty noticeable impact on both launch costs and overall system reliability. this effect becomes a bigger factor the more launches you do. it sets a pretty high lower bound on launch costs.

    The other part is one of operations. airliners and shipping companies have already shown how to do this part right. they do it by utilizing short turnaround times and a high degree of system flexibility in regards to both payloads and vehicles. Skylon is being designed for airliner like operations. success with regards to this is probably the real make or break factor. having the vehicle as an SSTO is big factor in achieving this goal. It actually lowers overall system complexity despite adding to the complexity of the vehicle itself.

  12. #132
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    Quote Originally Posted by Antice View Post
    At least they have the sense to use a development program that aims to prove each technology separately before building an actual vehicle. and well. skylon is going to have 300 or so un-manned testflights or so before anyone is allowed to even considder putting humans on board.

    I do wonder what technologies you consider as the greatest risk in skylon. the precooler/engine is going to be, barring any accidents, pretty much a proven technology before any other major investements are made. something i think is a pretty sound plan from an investors point of view.
    (related to colored text). So did NASA with the Shuttle. For that matter, so did deHavilland with the Comet. Testing components is standard aerospace procedure (been there, done that, got the scars), so it's far from a new idea with Skylon.

    Highest risk technologies? The engines and the thermal protection system, for two. The engine inlets, which cannot be tested on the ground for their full operating range, for a third -- these cannot be tested on the ground in their full operating range because there are no full scale hypersonic ground facilities. Anybody who claims the Skylon's precooler/engine system is "proven technology" based on a few dozen hours of ground testing in a very restricted subset of the operational environment is talking in marketspeak.

    Incidentally, I've worked on engine development programs, where the technical risk was much lower than on the Skylon's engine system. We had lots of surprises before the customers started to integrate their engines into quite plain-vanilla subsonic aircraft, during which we had a few more.
    Last edited by swampyankee; 2012-May-10 at 01:38 AM.
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    Quote Originally Posted by swampyankee View Post
    (related to colored text). So did NASA with the Shuttle. For that matter, so did deHavilland with the Comet. Testing components is standard aerospace procedure (been there, done that, got the scars), so it's far from a new idea with Skylon.

    Highest risk technologies? The engines and the thermal protection system, for two. The engine inlets, which cannot be tested on the ground for their full operating range, for a third -- these cannot be tested on the ground in their full operating range. Anybody who claims the Skylon's precooler/engine system is "proven technology" based on a few dozen hours of ground testing in a very restricted subset of the operational environment is talking in marketspeak.

    Incidentally, I've worked on engine development programs, where the technical risk was much lower than on the Skylon's engine system. We had lots of surprises before the customers started to integrate their engines into quite plain-vanilla subsonic aircraft, during which we had a few more.
    I did not intend it to sound like any kind of new idea. however we have seen proposals that do not have any kind of cohesive step by step plan like skylon does indeed have for retireing the technological risks, and stil got funded to the tune of billions of dollars. this probably reflects more on the fact that skylon is a concept that has been under serious development for more than a decade under private supervision and funding rather than a project trying to wing it under one government administration or another, where funding is given and taken away for no good discernible reason beyond what one or the other political fraction desires at that moment in time. politics and engineering does not mix any better than science and politics does.

    As for surprises during development. that is why there is a development program in the first place. if you could reasonably expect everything to work by just assembling the pieces then there wouldn't be a need for such an expensive program. I expect them to solve many big and small issues with a dev program to the tune of 10 billion dollars. (2007 dollars to boot)

    As long as the hardest parts are shown to work. (the precooler was identified as such from the beginning) then I see no reason for pessimissm in regards to making skylon a reality at this point in time.
    hypersonic inlets are for instance not an imature science. and REL did get rid of a lot of the common worries by moving the engines outside the vehicle shock cone as well.
    As it is stated now, they are finsihing up with the phase one engine dev cycle. proving that the precooler works. this part does not require hypersonic test vehicles nor wind tunnels. the precooler is not going to experience hypersonic airflow under nominal conditions.
    It's in phase 2 they will take it to the next level. and actually prove that the final engine works as advertized. this part is going to costs a lot more than the entire project has cost so far, and does indeed include a hypersonic test vehicle for validating all the aerodynamics of the engine.

    I remain pretty much optimistic, but i do agree. there are still unknowns that may indeed topple the project. what i am certain of is that the skylon is worth the money to try and develop. especially since it is more or less the most promisingly realistic concept we got going atm.

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    Take off in level flight requires lift... in a big way. We shall see.

    Dan

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    Quote Originally Posted by danscope View Post
    Take off in level flight requires lift... in a big way. We shall see.

    Dan
    Lift is a function of lifting area, airspeed and angle of attack. there is nothing mysterious about it. skylon will get lift trough increased takeoff speed to compensate for the shortness of the wings. do keep in mind tho. the skylon is very voluminous compared to it's mass. those wings may seem deceptively small to you, but they really arent as bad as small in relation to the mass as they look.
    perceptions colored by airliners who are optimized for fuel efficient flight at subsonic speeds do not compare well with a hypersonic flier like skylon. There is such a thing as too much lift you know. it was one of the major design flaws of the HOTOL concept. something they realized pretty early on, leading up to a redesign of the entire concept. too bad money ran dry before they metamorphised (sp?) it into skylon.. or maybe that was a fortunate turn of events? hard to tell really. I'l leave the judgement on that to future historians.

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    If the Starfighter flies, if the X15 flies, Skylon flies. As Antice said, lift isn't some unknown new science. When I was working on a scramjet aircraft for ESA, the lift calculations at this point of development were simply an Excel sheet to find out how much wing area was needed for a given airfoil, takeoff speed and mass.

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    Quote Originally Posted by danscope View Post
    Take off in level flight requires lift... in a big way. We shall see.

    Dan
    I cannot understand why you continue to make posts like this when you have made it clear you've done little or no research on the project. As others have pointed out there is nothing odd about the wing span given the the performance envelope of the vehicle.

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    Skylon:
    http://2.bp.blogspot.com/-4wPHXPENKA...970c-550wi.jpg

    Starfighter:
    http://www.fiddlersgreen.net/aircraf...heed-F-104.jpg

    If a starfighter can take off from a runway with those tiny wings, why wouldn't a Skylon?

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    The F-104 has small wings, and about as fast a take-off roll as you could ever see. But Skylon is going to need the Bonneville Salt Flats ! I think there may be some engineering revisions to the "artist's concept " wings suggested in the literature so far.
    I welcome debate on the concept of wings vs take-off with this scheme.

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    Hi, The weight comparison of the scramjet to a full-sized Skylon are worlds apart. And the scramjet was air-dropped,
    if memory serves us. Can't air-drop Skylon with a C-5A at Mach 2. I see problems in this area.

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    Quote Originally Posted by danscope View Post
    Hi, The weight comparison of the scramjet to a full-sized Skylon are worlds apart. And the scramjet was air-dropped,
    if memory serves us. Can't air-drop Skylon with a C-5A at Mach 2. I see problems in this area.
    You think that the engineers working on that project haven't done calculations on the lift?
    As above, so below

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    While I think the term "optimistic" applies to a lot of the engineering issues, the wing area is not something I see as a problem. Now, Skylon will almost certainly need waivers as it will probably exceed the 250 knot speed limit at low altitude, and its takeoff noise level may make a straight-jet 707 seem tame, but the wing area is not a big deal.
    .
    This does of course, bring up the brakes....

    ...aborted takeoff at maximum weight on a really hot day...
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    Quote Originally Posted by swampyankee View Post
    While I think the term "optimistic" applies to a lot of the engineering issues, the wing area is not something I see as a problem. Now, Skylon will almost certainly need waivers as it will probably exceed the 250 knot speed limit at low altitude, and its takeoff noise level may make a straight-jet 707 seem tame, but the wing area is not a big deal.
    .
    This does of course, bring up the brakes....

    ...aborted takeoff at maximum weight on a really hot day...
    Well, the takeoff speed for the craft is estimated to be around Mack 0.5. For an abort during takeoff, the Skylon would use water for cooling the brake system, and the runway will have the extra length necessary for abort. After takeoff the water is dumped, since after the mission there will be little fuel left, so the mass is much lower and will not pose such a problem for the breaking system, and there is no point in wasting payload mass on hauling a few kiloliters of useless water of into orbit.

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    Quote Originally Posted by swampyankee View Post
    While I think the term "optimistic" applies to a lot of the engineering issues, the wing area is not something I see as a problem. Now, Skylon will almost certainly need waivers as it will probably exceed the 250 knot speed limit at low altitude, and its takeoff noise level may make a straight-jet 707 seem tame, but the wing area is not a big deal.
    .
    This does of course, bring up the brakes....

    ...aborted takeoff at maximum weight on a really hot day...
    as swampyankee said, they have taken emergency breaking into account for a runway abort scenario.

    I dunno about noise waivers tho. it's a space launch vehicle, and is therefore not subject to standard aviation rules in the first place.
    I think the noise problem is a minor one. the spaceport would have to be pretty far away from human habitation at any rate for other reasons as well as the noise. so I don't really see an issue. altho, i suspect that like airports, the spaceport will tend to attract people to move into the area since it is a good source of job's. so even if you were to place such a spaceport in the middle of nowhere, you'd probably end up with a town pretty close soon after at any rate.. however. if you choose to move that close to a spaceport then your right to complain about the noise is revoked.

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    Quote Originally Posted by danscope View Post
    Hi, The weight comparison of the scramjet to a full-sized Skylon are worlds apart. And the scramjet was air-dropped,
    if memory serves us. Can't air-drop Skylon with a C-5A at Mach 2. I see problems in this area.
    The scramjet concept I'm talking about was a huge, heavy beast that launched from a runway. We just ran it through Excel for airspeeds starting from takeoff speed all the way through its envelope to see the lift & drag results (so we could compare it with other calculations to find the excess lift and thrust at each stage of the flight). Really, how difficult do you think it is to do the rough calculation on whether or not a plane with a given mass, airfoil, wing area and takeoff speed will fly or not? It will need a long and strong runway for sure, but just answering "will it fly with the wings we've drawn here" is a piece of cake for the people involved.

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    Quote Originally Posted by danscope View Post
    The F-104 has small wings, and about as fast a take-off roll as you could ever see. But Skylon is going to need the Bonneville Salt Flats ! I think there may be some engineering revisions to the "artist's concept " wings suggested in the literature so far.
    I welcome debate on the concept of wings vs take-off with this scheme.
    Unless I'm horribly mistaken, an F-104 could take off at about 370 kph (and some jets with more afterburning thrust than weight could in theory just do the rocket thing at 0 kph ). I've had a 777 in Dubai go airborne at something above 330 kph. I remember thinking that we went faster than a Ferrari F40 before getting the wheels off the ground. Granted, the 777 has a somewhat larger wing than the F-104 or Skylon, so you'd have to do the calculations to see where Skylon ends up. But if these guys can make that precooler work, they can run the lift formula as well.

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    Quote Originally Posted by John Mendenhall View Post
    I would argue that indeed they are inherent. You have to get the velocity to 18,000 mph for LEO. That means a big rocket. And you have to brake that object to bring it home. Both problems are inherently dangerous, and unforgiving. As any Quality Engineer can tell you (and I have been an ASQC certified one), humans will make mistakes.

    Regards, John M.
    Well, a BDB is also going to have to do the same things, and while a rocket may explode, taking out its crew, possibly even some ground technicians, how many would be endangered by a failing launch loop or space elevator?
    I would love to see some of these great ideas put into practise, but we don't have real-world experience, so I still don't think we can say that rockets are on the way out.

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    Quote Originally Posted by danscope View Post
    The F-104 has small wings, and about as fast a take-off roll as you could ever see. But Skylon is going to need the Bonneville Salt Flats ! I think there may be some engineering revisions to the "artist's concept " wings suggested in the literature so far.
    I welcome debate on the concept of wings vs take-off with this scheme.
    Have you even gone to thier site to see what this thing is all about? TrAI gave you some of the information that is right in plain sight on thier FAQ page. Or, is it that you dispute thier claims?

    For the answer to the question you didn't ask (but claimed)... 5.6 km. Or, less than twice the size of a major airport's runway. Actually; it's about the same length as the longest commercial runway.

    Quote Originally Posted by danscope View Post
    Hi, The weight comparison of the scramjet to a full-sized Skylon are worlds apart. And the scramjet was air-dropped,
    if memory serves us. Can't air-drop Skylon with a C-5A at Mach 2. I see problems in this area.
    Its engines are more than just Scramjet or rocket mode.

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    Hi Neo, I am talking wing loading, not propulsion. There is nothing in the literature about wing loading or the wing area on this paper airplane. 275 tons is a considerable weight indeed.
    An SR -71 Blackbird has an empty weight of 67,500 lbs and only takes on as much fuel as it needs to get to a waiting tanker for a very much needed re-fuel in flight. And that aircraft has a wing of 1795 sq.feet plus a lifting chine.
    Well.... we will see. The aircraft is so far in the future, it's shape is going to be revised anyway.

    Best regards,
    Dan

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    Quote Originally Posted by danscope View Post
    Hi Neo, I am talking wing loading, not propulsion. There is nothing in the literature about wing loading or the wing area on this paper airplane. 275 tons is a considerable weight indeed.
    An SR -71 Blackbird has an empty weight of 67,500 lbs and only takes on as much fuel as it needs to get to a waiting tanker for a very much needed re-fuel in flight. And that aircraft has a wing of 1795 sq.feet plus a lifting chine.
    Well.... we will see. The aircraft is so far in the future, it's shape is going to be revised anyway.

    Best regards,
    Dan
    You keep bringing up this subject but have you actually done the research? Do you have any proper analysis to indicate there's an issue or just your vague hunches?

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