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Latest theories are for inter stellar propulsion

  1. Jun 6, 2003 #1

    wolram

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    can anyone tell me what the latest theories are for inter stellar
    propulsion, and has the problem of bone loss on long space flights
    been solved?
     
    Last edited by a moderator: Feb 5, 2013
  2. jcsd
  3. Jun 6, 2003 #2
    what's propulation?
     
  4. Jun 6, 2003 #3
    I think he means "propulsion".
     
  5. Jun 6, 2003 #4

    ahhh! now that would make more sense!


    all the stuff we send up there is still being fueled by the highly combustable rocket fuel. (i think) but most people agree that is we want to have any real possibility of long distance space travel, we're going to need to get a better fuel system. (fusion being by far the most promising!)

    and i don't know about the bone loss thing. maybe the should take Medimusal-the fibre tablet! did you know that in space, astronauts grow like five inches taller because there is less spinal compresion?
     
  6. Jun 6, 2003 #5

    wolram

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    exuse me i have "slight" dificulty with spelling
     
  7. Jun 6, 2003 #6
    I remember reading something about an "ion drive" a while back. Not sure if it ever came to fruition. Then there is of course the "vacuum energy" theory.
     
    Last edited: Jun 6, 2003
  8. Jun 6, 2003 #7
    The ion drive is very much real. It is used on numerous satellites for orbit corrections and the Deep Space 1 probe used an ion drive for testing and propulsion during its comet and asteroid flybys.
     
  9. Jun 6, 2003 #8

    wolram

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    what is ion drive,how much thrust does it produce?
     
  10. Jun 6, 2003 #9

    drag

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    Greetings !
    Ion engines are space propulsion devices that
    use inert gases as their propellants. They ionise
    the propellant thus providing it with an electric
    charge and then use electrosatic or electromagnetic
    fields to accelerate it to great exhaust speed ussualy
    several times and more greater than those of
    chemical rockets. Through the fields the thruster pushes
    against the ions thus pushing itself in the opposite
    direction according to Newton's Second Law.

    The ion thrusters that have been operated in space so
    far only produced up to a few hundreds of miliNewtons
    of force and were ussualy powered by solar panels
    at power levels of up to a few KiloWatts.

    The efficiency of these systems lies in the fact that
    they have such high exhaust velocities and thus can
    produce far greater thrust for the same amount of fuel.

    Live long and prosper.
     
  11. Jun 7, 2003 #10

    drag

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    wolram, there's a NASA funded program (or was, at least)
    called BPP (Breakthrough Propulsion Physics). My old
    link to it doesn't work, but I think you can find it
    easily through one of NASA's websites. It's about developing
    new physical theories that could allow interstellar travel.
    With the currently known technologies interstellar
    missions with any reasonable parameters are a practical impossibility .

    Live long and prosper.
     
  12. Jun 7, 2003 #11

    wolram

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    cheers DRAG im of huntimg.....
     
  13. Jun 7, 2003 #12

    Janus

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    One of the new promising drives is the VASIMIR. It works by heating the reaction mass up with radio waves until it reaches plasma state, containing it in a magnetic bottle, then allowing this plasma to escape out a nozzle. The VASIMIR has the advantage of the ION dirve of High exhaust velocities, but is capable of generating greater thrust.

    The VASIMIR was actually developed from Controlled fusion experiments, where they were trying to find ways to create and contain the high temp Plasma needed. The containment always ended up leaking. Then someone realized that they could make use of this. If the containment is going to leak anyway, Why not just use this to our advantage in a rocket engine?
     
  14. Jun 7, 2003 #13

    LURCH

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    BTW, a new propulsion system will solve the bone-loss problem automatically. If we could provide 1G of thrust, there would be no loss of bone or muscle mass, because these are effects of low-G.
     
  15. Jun 9, 2003 #14

    drag

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    Greetings !

    Janus, it's VASIMR - Variable Specific Impulse Magnetoplasma Rocket.
    As far as I remember what I read about this the
    exhaust velocity range is about 10 - 200 miles per second.
    But of course, the propellant flow is reduced at higher
    tempratures - exhaust velocities (due to containment and
    power limmitations) and thus the total thrust is also
    reduced for high exhaust velcoities.

    LURCH, no such luck. Electric propulsion has high
    exhaust velocities (or specific impulse) but poor
    total thrust, so the acceleration is tiny.

    Live long and prosper.
     
  16. Jun 10, 2003 #15
    I've found an interesting p-age about ion propulsion:http://science.nasa.gov/newhome/headlines/prop06apr99_2.htm

    BTW I've had an idea (though i've posted in again somewhere),
    what if we used such powerfull electrical fields that would push the ions near the speed of light? That would increase the ions' mass a lot and because of the momentum concervation of the system it would end up to a very powerfull acceleration of the vehicle.

    Feel free to correct me if i'm wrong.
     
  17. Jun 10, 2003 #16

    drag

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    Greetings !
    Well, there's a tiny little bit of a problem there
    that's called energy. Any electric propulsion system
    recieves energy from a power source.

    Now, the momentum that a propulsion system provides
    is p = m * v with m being the propellant mass ejected
    and v being the exhaust velocity. However the energy is
    Ek = m * V^2 / 2 , so you can see that as the exhaust
    velocity grows the energy required to accelerate the propellant
    grows as a square function of it, while the momentum
    only grows as a linear function.

    Of course, once you're near c the relativistic mass increase
    will be great while the relative velocity increase will
    be poor and then primarily the mass will grow as
    a linear function in each equation. However, to get that
    close to c you must be able to supply the huge amount
    of energy that's entailed by the square of the velocity
    in the kinetic energy equation so only if you can get that
    much energy will you be able to use the relativistic mass
    advantage.

    Further more you should consider the source of energy
    itself. Even if theoreticly you were, for example, to use
    something like stored anti-matter, at near c velocities
    you'll have to anihilate more anti-matter than the
    propellant mass you'll be ejecting due to effeciency
    issues and so the whole thing turns into a mess
    and results in the fact that you'll still need huge
    relative amounts of anti-matter that are much greater
    than the mass of the final payload to just make a single
    acceleration & decceleration one-way trip.

    In short, new frontiers will require new physics...

    Live long and prosper.
     
  18. Jun 11, 2003 #17
    Well, drag, seems you're right. I also thought it would be impossible to find such power source (they would have already used it)
    but i was too bored [zz)] to sit and analyse my idea with equations.

    Anyway, this is the theory forum, right? :wink:
     
  19. Jun 11, 2003 #18
    I'm confused: "once you're near c" - relative to what?? Isn't rocket with its fuel completely independent inertial frame? Then, how does it notice its own relativistic mass increase? I thought it all boils down to exhaust velocity only. Over time, earth observer would express rocket mass' relativistic increase, but not rocket observer?
     
  20. Jun 11, 2003 #19

    drag

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    I'm sorry if I might've phrased it in a slightly
    confusing manner. I was talking about the exhaust
    velocity of the propellant relative to the spacecraft - not
    the velocity of the spacecraft itself.

    Live long and prosper.
     
  21. Jun 12, 2003 #20
    ok, but now I'm confused on other issue: why would we need relativistic exhaust velocities at all? All we need is ability to accelerate given mass at 1G, ejecting onboard mass from that same inertial frame. In about 1 year we'd reach 1c relative to earth observer.
     
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