This plane will be able to fly anywhere in the world within 4 hours

Discussion in 'Science' started by Jacom, Dec 16, 2014.

  1. Jacom

    Jacom Member

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  2. oculi

    oculi Member

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    I was reading about another project/study Alan Bond worked on (no, not that Alan Bond) https://en.wikipedia.org/wiki/Project_Daedalus

    this one seems pretty light on detail, we must have learned a lot since the SR-71 as this would be considerably faster than it was.
     
  3. RobRoySyd

    RobRoySyd Member

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    There's a bit of information on the SABRE engine here.

    So far this is only the heat exchanger which doesn't sound like that much but 400MW of energy transfer is very impressive. Still the concept goes back quite a few decades and as always the problem is mostly in the realm of materials technology. What seems new here is helium is used as a heat transfer fluid to get around the problem of hydrogen not playing nicely with many metals.
     
  4. _slacker_

    _slacker_ Member

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    hiding from census dude!
    Last edited: Dec 16, 2014
  5. onrelas

    onrelas Member

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    Are you being sarcastic and saying the company in the OP is comparable to David Adair? You're aware just about everything he says is a figment of his imagination right?
     
  6. _slacker_

    _slacker_ Member

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    hiding from census dude!
    I am not aware. I know nothing of space, magnetic fusion containment etc but if he's bright enough to have Hawkings, NASA and Congress all request audiences back in the day im sure he knows/knew something worthwhile. You dont get invites like that on crackerjacks boxes.

    What I know? I know enough to know I know next to nothing. But. I keep an open mind. Im sure you are well qualified to call this man a crackpot yes? ( yes, sarcasm was intended here I think )
     
  7. RobRoySyd

    RobRoySyd Member

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    How do you know he even had that apart from him and a few ardent followers repeating the same thing.

    What qualifications has this man got?

    Let's be quite clear here, at the age of 17 he built and flew a rocket powered by nuclear fusion. By comparison we're spending billions of Euros and employing the minds of hundreds of the best men and women to try to get a sustained fusion reaction going inside a machine weighing 1,000s of tons.
    All we need from this man is a few half decent sketches showing how he could do it so easily and the world will be at his feet.
     
  8. _slacker_

    _slacker_ Member

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    *1* I dont. Like i said and you most likely missed, was that I am open to hear what people have to say. Scientists said the world was flat. Scientists said AIDS was HIV. Science has said alot. I dont place a great deal of weight against a degree. Savants have no degrees yet just see the code/art/answer. Science isnt all about being right. Theory is theory. practise is practise. Im open that he had these dreams and then practised. I have before been in "deja-vu" experiences before so I dont doubt. You are welcome to though.

    *2* I dont know. I imagine qualifications dont matter when you walk the line with top echelon folks. My father is extremely skilled in what he does yet never has had a medical. If you were to pull him apart you would find his medicals are all in order. Those that want his work make sure of it. Im sure the same thing can be applied here.


    *3* Statement or question? Ill answer as if it were a question. The man wont sketch. He has his reasons, which he has explained. He is though, still alive. Other sketchers are pushing daisies up through many series of unfortunate accidents. I guess when we are ready to know and listen, others will come forth to tell their tales to. Either way, the OP engine.... Hmmmm. 400MW of heat dissipated to, and let me quote the article you chose to put your beliefs in, :

    Now I dont have a degree but for this engine to function it needs oxygen. Good luck in space with that. Its a simple phase-change principle thats not so simple to put into practise. And, as for our best. How do you know they are our best? Im not against Jesus. Im not for Jesus. But Jesus is going to be Jesus regardless of what I think or know so relax. Discuss. Keep an open mind. I did when I viewed the OP.
     
    Last edited: Dec 17, 2014
  9. MR CHILLED

    MR CHILLED D'oh!

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    If it ever were to come to fruition it would really open the world up a lot than presently.

    I for one would love something like this, as I'm sure many others would.
     
  10. RobRoySyd

    RobRoySyd Member

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    It will carry liquid oxygen as well for when it is beyond the Earth's atmosphere.

    It's all about power to launch weight. Previous designs that Alan Bond worked on involved carrying no oxidant at launch, the craft would fill a tank with liquid oxygen from the air during it's flight up, that idea it was hoped would significantly reduce launch weight but it added complexity and hence weight. It seems it wasn't possible to refine the idea to the point where the gain was more than the loss and the concept has been abandoned, at least by Bond.

    The other problem is nozzle and combustion chamber design, what works at atmospheric pressure doesn't work so well as the atmospheric pressure drops, that's why rockets have different stages. Bond's team in collaboration with others have had success in designing a variable nozzle that can adjust to the changes in outside pressure.

    The other advantage of this kind of craft over conventional rockets is it in part avoids the "gravity cost". A rocket has to use a lot of it's thrust counteracting the force of gravity just to maintain altitude, there's no aerodynamic lift. By having a wing the speed of the craft generates lift until there's no air, then the motor morphs into a pure rocket motor.

    Personally my main concern with the craft isn't so much it getting into space, it's getting back down. The craft has a lot of wing area that'll have to withstand the heat and loading of aerodynamic braking as it re-enters the atmosphere.

    No, science is all about being wrong.
    Proof that a theory is right is always constrained, there's always the possibility that it's wrong or doesn't fully explain every circumstance.
    Proof that a theory is wrong or limited in application is unconstrained. Scientists often get big prizes for proving a long standing theory wrong, proving a theory right is rather boring.

    Eratosthenes calculated the Earth's circumference over a century before Jesus's time on Earth and to a remarkable degree of accuracy. I know of no point in time in the history of science that a flat Earth was given serious consideration. The Earth at the centre of the universe theory certainly was because it does make some sense and for some time as a theory it was difficult to disprove.

    I do have an open mind, in my lifetime I've had to revise or throw out just about all the science I had learned in high school. I don't fully understand a lot of what I've since learned and conventional science without any conspiracy theories thrown in has plenty to keep me in awe of the universe I inhabit.
     
  11. oculi

    oculi Member

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    didn't think of that, much more tricky than withstanding mach 5 (which will still be tricky) flying point to point on Earth.

    how does the wing area compare to a shuttle? wonder if using retro rockets (still using the heat exchanger) would be an option?

    I still can't work out where the heat pulled out of the inlet air goes, I started a rough latent heat calculation to work out how much hydrogen fuel they would need to be carrying but didn't get very far, i'm sure they have done this calculation already.
     
  12. RobRoySyd

    RobRoySyd Member

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    The Shuttle was a glider, the new craft is designed for powered flight, despite having flown gliders I never realised this was a big factor. There's some discussion of the Shuttle's stall speed here: http://quest.arc.nasa.gov/space/ask/landing/Orbiter_Stall_Speeds.txt. Stall speed is sort of indication of wing performance and glide ratio.

    As for retro rockets being used to slow the craft down, well they all use them but just enough to cause the orbit to decay. I'd imagine there's all kinds of other aerodynamic issues because of stall risks in thin air, I do know that above 100,000' there's not enough airflow for control surfaces to work well.
    The other issue would be the increased fuel load, at a very rough guess it could take a significant amount of fuel to achieve that much braking.

    Latent heat of the liquid hydrogen which is then burnt as gas. But yes, I too am lost a bit on this as most rocket motors use the latent heat of the fuel to cool the rocket motor nozzles. There's some indication I think of excess hydrogen being dumped as well.

    Overall the balancing act they're trying to achieve reminds me of the Russian's closed cycle single shaft engine design, they blew up a lot them before they got it right. No doubt these guys have sophisticated simulation software plus they say they don't need to fly the thing to test the engine design, a luxury the Russians didn't have. Still looking at the diagrams it's a complex thing that requires a lot of parts to work together to change modes as well as maintain both modes.
     
  13. oculi

    oculi Member

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    I meant just for re-entry, I assumed it would have to re-enter the same way as a shuttle does, which is flat side against he airflow" to maximise the air cushion, the concept looks a bit too sleek to do that though, I have a feeling it will end up looking much uglier (like a shuttle) to be able to work.
     
  14. RobRoySyd

    RobRoySyd Member

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    I spent a fair amount of effort today trying to understand the complexity of re-entry, that's not a simple subject at all.
    What I couldn't get my head around completely was why if a craft can go up one way it cannot safely come back down the same way. That seems an obvious if not simplistic view and yet nothing I read seems to have explained why such a simple theory is wrong.

    Another thing, it is possible to re-enter using multiple skips, some craft such as the Shuttle were capable of that, it was never tried. The problem is a too shallow angle can cause the craft to bounce up into a higher orbit unable to return. How, didn't the craft just keep some free energy doing that? :confused:
     
  15. oculi

    oculi Member

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    I think it is as simple as when you go up Gravity is working against you, when you go down it is trying to make you go down faster. (you don't need to use the brakes driving up a steep hill, you do driving down it) If you had enough power to reach re-entry speeds while leaving orbit I think you would definitely encounter the same problems.


    I would guess the problem is in the upper atmosphere there isn't enough air to slow you down much, by the time you get to "thick air" you are going too fast to do that. the wiki entry on re-entry mentioned heat sinking as a method of dealing with the heat, if you could store the heat energy somehow in an aerodynamic craft i'd imagine you could do that. i'll use my SR-71 example again as they had air friction heat problems, so i guess you wouldn't be able to go slow enough quick enough to shed heat into the air, in the short term you would be trading speed for height.
     
  16. Ratzz

    Ratzz Member

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    My wife has a broom that will do this already..
     
  17. RobRoySyd

    RobRoySyd Member

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    Yes. My problem was I had the weight being pulled up with a string over a pulley thing from high school physics stuck in my head. A rocket going straight up has to first supply enough force to counter that pulling it down with Mass x g. That energy is lost.




    Yes, that pretty much sums it up, there's a critical altitude where it all comes together. Various strategies are used e.g."shuttlecock" braking used on Virgin's Space Ship One but that will only work for sub orbital re-entry.

    The Lunar Lander used a rocket to control its descent however I think for an orbital descent to Earth you'd use almost as much fuel as you used getting into orbit.
     
  18. Foliage

    Foliage Member

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    Surely the amount of fuel this would use would make it prohibitively expensive? Not to mention the airframe would fatigue so fast it's lifetime would surely be very short?
     
  19. RobRoySyd

    RobRoySyd Member

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    Cost is what killed Concord however on routes where people might have been more likely to pay the cost to get to their destination quickly because much of the route was over land Concorde couldn't fly supersonic which really killed the plane. Hypersonic flight above 100,000' wouldn't generate any sonic shock wave and the fuel cost will probably not be that much higher.

    Where this craft should do well though is delivering a payload into orbit. A lot of the cost at the moment is expensive rockets that are single use. A lot of fuel is burned that could be avoided.

    Fatigue is caused by several factors such as vibration, thermal stress etc. I think once you're above the atmosphere there's much less of this. As we've already discussed though re-entry has to be the area where this concern would be most prominent.

    Even the designers do say this new engine is still decades away from powering a plane. First they have to get the engine to work.


    Bob.
     
  20. Lucifers Mentor

    Lucifers Mentor Member

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    That's not correct - you will still get aeroelastic buffeting at hypersonic speeds, which would make any flight hideously uncomfortable. And the fuel costs would be significantly higher - flying at hypersonic speeds doesn't give you a free lunch. The faster you go, the higher your fuel consumption.

    That said though, we're talking about Reaction Engines here. They've been shopping this idea around for the last decade, gathering lots of press, but not really ever doing anything. It's always just a few years away from being ready, according to them, but the goalpost keeps on moving. It'll never be viable or cost effective as a commercial passenger enterprise, even though that's always the way Reaction try and sell it.

    Edit: Though you were talking about over 100,000'.
     

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