Simplest and cheapest rocket possible

Discussion in 'General Discussion' started by Frank, Jun 14, 2008.

  1. Frank

    Frank Certified not a majority
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    What would be the simplest and cheapest rocket possible, that you could build yourself from stuff that is readily available and be capable of lifting stuff into orbit? Adding as much of them as it takes to lift the mass required (in stages if needed) is no problem, as long as they're really cheap.

    Alternatively, if scaling them up is easy, a reusable SSTO is of course nicer.

    My thoughts:

    1. Solid fuel rockets are very simple and cheap, great for the small stuff, but hard to scale. If you go beyond firework scale, they become quite hard to build, the thrust can vary a lot and they're almost impossible to throttle.

    2. Liquid fuel scales great, but requires a lot of practice, effort and a well stocked machining shop. Unless you can come up with something really basic and (almost) solid-state, the amount of flaws possible will make the rate of error very high (comparable to the amount of components), and the initial investment quite big.

    3. A single engine always has a better weight/thrust ratio than multiple engines. It's only the weight of the fuel tanks and supporting structures that makes multi-stage rockets perform better. But they also suffer from diminishing returns: you do need to lift more.

    In short, I think the simplest and cheapest design is probably best. Saving weight can always be done later, if needed (and affordable).

    If it can be done really cheap, I really want to try and build one.


    Or how about a Beyond3D X-prize entry? :grin:
     
  2. weaksauce

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    You know those "bottle-rockets" you fill up with water and compress air into with a pump until the pressure gets too high and it shoots up? How about one like that, but super big, and yellow?
     
  3. Frank

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    The thrust to mass ratio of that is only good for about one second. I need something that'll work for up to 15 minutes.
     
  4. Frank

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    Btw, multi-stage, as in: using multiple, diferent engines is an idea as well. As long as you carry the fuel, a ram/pulse jet and an open scramjet are really cheap and simple.
     
  5. weaksauce

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    How about building a spherical sattelite with a hot plasma cover and shoot it up with a giant slingshot? Or something. I mean, it should get cheaper with wind resistance out of the equation.
     
  6. weaksauce

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    Oh, also! Arent they already sending up stuff into space with baloons? How about having that as the first stage? You could have like a baloon stage, then a slingshot stage, and then a bottle rocket stage. :D
     
  7. Frank

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    Well, microwaves would also work. But, (like with a balloon), the amount of payload it could carry (ie: your rocket) would suck, and you still need that rocket for the second half of the trip.
     
  8. weaksauce

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    Not even if you have giant platform "powered" by lots of balloons? But I think I've got a better idea now that we're talking about balloons: You can make your own Hydrogen. And if you want to be really cheap you can get a solar panel and have it running for some years. And then you could do something like compressing that hydrogen into tubes, really long tubes which you then combine into a cylinder, and then you burn the fuel by just letting it out of the vents and using a sparkle, and then maybe with a delaval nozzle underneath all of that you can get enough thrust. And with some remote appliance you can control the flow of hydrogen. It'll be like a solid state rocket but with gas.

    Actually, I'm thinking now, maybe you can use a lot of hydrogen balloons to lift up the "tube-rocket" as much as possible, then using some compressor you can compress the hydrogen superfast into the tubes and then set it on fire. And there's another benefit of having that compressor when the gas starts to decrease I guess.
     
    #8 weaksauce, Jun 14, 2008
    Last edited by a moderator: Jun 14, 2008
  9. AlphaWolf

    AlphaWolf Specious Misanthrope
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    I saw something about trying to achieve orbit using a glider, I'll see if I can find it.
     
  10. Davros

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    What happens when daft people get silly idea's about rockets :)
     
  11. tongue_of_colicab

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    I dont really know anything about building rockets but isnt trying to have as little as weigth as possible #1 priority? As you relative need more power as the weight goes up so the lower the weight the smaller, cheaper and simpler your rocket can be.

    I dont think it can be done really cheap. Even those amateur rocket people spend alot of money on getting rockets up and those cant even get into space.

    The cheapest way for the rocket would probably be launching it from a airplane so you have 10km or so less to travel.
     
  12. digitalwanderer

    digitalwanderer Dangerously Mirthful
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    Cheapest rocket possible? Diet coke and mentos. :razz:
     
  13. Frank

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    Thinking from the other side (and taking a lesson from Formula 1: "if it is still in good condition when the race is over, it was build too strong") and starting with fireworks instead of conventional rocket engines, there are actually a few fascinating possibilities:

    1. Ablative rocket nozzles. Cooling those nozzles is the single hardest thing to get right, when developing rocket engines. But why bother? Simply let it burn away. Use LOX to create a cooler air curtain at the sides, and make sure they're thick enough. Materials can be glass fiber composite (outside), carbon cloth composite (lining) and heat-resistant concrete (filler). Can be build at home for a few bucks.

    2. Semi-solid fuel. Make a gel from diesel with aluminium powder and an oxydizer in it, simply by cooling it down. Take a single fuel tank, put a piston in it and fill the top with something that provides pressure, cooling and allows for pre-heating, like LOX. You can bleed off a bit of LOX every now and then to keep it cold enough. Push it out like with a tube of toothpaste, get the diesel to ignite to spread it out evenly and pre-heat it, and see if your ablative nozzle can take it. Blowback would be a problem, though. That solves the second and third hardest problems (getting the fuel to burn evenly and getting enough fuel and oxydizer into the combustion chamber) all in one go.

    Edit: if you use an aluminium tank and allow some of the heat to creep back in, you might be able to keep the pressure lowish, but more or less constant. Just make sure you throw it away when done, before it blows.
     
    #13 Frank, Jun 15, 2008
    Last edited by a moderator: Jun 15, 2008
  14. Frank

    Frank Certified not a majority
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    Even simpler: just take a long, thick walled aluminium pipe, blow LOX through and some fuel to get the temperature up real high until the aluminium at the inside of the pipe starts to burn!.
     
  15. Frank

    Frank Certified not a majority
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    "As hard as Rocket Science!"

    Is it, really?

    If we look at the X-prize and such: you have to be able to hover, which requires throttle control, you have to be able to send a human up to LEO and come back, and you have to be able to repeat that with the same rocket in a month. That's more than any currently available commercial rocket (even the Space Shuttle) can do! And the prize money is at most $20M, while any available commercial launch is a lot more expensive!

    Then again, simply hitting the Moon only requires thrust and guidance. If you don't succeed, try again.

    "Aim for the Moon!"

    Literally. :grin:
     
  16. dizietsma

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    It would be probably be cheapest and easiest to shoot your payload into space such as HARP did all those years ago.
     
  17. nutball

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    That depends on what you're launching. Small payloads can be quite cheap. There's a semi-endless supply of ICBMs which are being re-tasked for such purposes. $10-20M are figures I've heard for a few tens of kilos to LEO (possibly a bit more mass than that I don't recall precisely).
     
  18. Davros

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    ok who volenteers to pilot franks rocket
     
  19. Sxotty

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    Frank can go first of course.

    "Aim for the moon!"

    Oops he missed...
     
  20. Davros

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    maybe he wants a close-up of Uranus!
     
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