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Propulsion Systems

  1. Oct 30, 2004 #1
    A single Engine with five gears, or five separate Engines with 'fixed' propulsion's, as opposed to transitional gearings?

    A rocket leaving Earth has 'boosters', once it is orbiting it uses propulsion systems that are more compact and have a weight-to-ratio output more efficient than Earthbound systems due to the fact that the craft is allready in motion,(my wording here may be technically vague,forgive me).

    What I want to know is, if a Craft is already in a far-off part of Space, then what 'type' of propulsion system is the most efficient for attaining higher speeds?..I know that gas or aerosols can manouvre crafts for docking etc..but I seen an experiment where a 'Superconducting', Electro-Magnetic ring was propelled to a great height, and this was in a Lab on Earth.

    Is it feasible that crafts can have Superconducting Propulsion systems, on board to be used as 'boosters'?

    Basically, if a craft lands on another planet or Moon?..and has a Superconducting plate, (which is obviously situated so that it can be lowered to below the craft, the craft being the 'ring' from the experiment that I had seen), then surely this would produce a really fantastic propulsion system to crafts that need a once-only boost for take off from..say Mars or dare I say it bodies that may have surfaces that already have 'superconducting' surface's?

    The question again, can Superconduction, Electro-Magnetic systems be used to launch crafts from its surface to Orbit?
    Last edited by a moderator: Jan 14, 2014
  2. jcsd
  3. Oct 31, 2004 #2


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    It sounds like you're talking about magnet-electrodynamic drive (the "caterpillar" drive from "The Hunt for Red October"). That's a real technology that works for ships - it has nothing at all to do with spacecraft propulsion and referencing it to spacecraft propulsion is a relatively recent hoax.
  4. Oct 31, 2004 #3


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    Many rocket engines are throttleable as it is.

    Not exactly. A rocket leaving Earth has boosters to take advantage of staging. Any mass you drop off along the way, you don't have to spend fuel to accelerate it up to orbital velocity. Different rockets are used in space to take advantage of underexpansion of the flow. As a rocket's exhaust speeds up in the nozzle, its pressure drops significantly. The faster it goes, the lower the pressure drops. This is just what Bernoulli's equation tells you should happen (although you need to use different equations... rocket exhaust is not incompressible). If the pressure drops below ambient pressure, you get a 'suction' at the nozzle exit, reducing the thrust from the rocket. You can see this on footage from the space shuttle during liftoff. The exhaust plumes are bent inward. That's because of the outside air pushing them. If you watch the full ascent, that angle will decrease and eventually the plume will go outward (the Shuttle's main engines are optimized for upper atmosphere operation). Once the craft is in orbit, you don't need to use engines at all, except to turn your ship or do a de-orbit maneuver.

    Whichever type of propulsion system has the highest Specific Impulse or Isp. That's a measure of how fuel efficient a rocket is. The best we have (or could have within a few years) are either electrical (Ion drives, arcjets, etc.) or nuclear.

    Russ mentioned the answer to this. Until (biiiig if, here...) we find a way to warp gravity or something like that, every spacecraft propulsion system will have to use something for fuel.
  5. Oct 31, 2004 #4
    Sorry Russ I aint seen "Hunt for the red october", and I certainly have not heard of any recent Hoax material. My wording of what I wanted to know is pretty feable after re-reading my post, but I was reading some material, and played an old video of Frank Close-lecture.

    It was in this lecture he showed a demonstration of Superconductive Electro-Magnetics, where he placed a 'metal ring' around the magnet, throwed a switch and up flew this metal ring,this was what I was aiming for.

    A pretty basic notion I had was that on planets with a 'low-gravity', then the escape velocity would be within a "superconductive-Electro-Magnetic" propulsion system just for the take-off?..or so I was contemplating, thanks anyway.
  6. Nov 2, 2004 #5


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    Thats basically a solenoid. Its the same as any other magnetic propulsion (including an electric motor) Its also still an action-reaction propulsion system. The nearest equivalent in spacecraft is ion propulsion, which also is real and works (Cassini, iirc, uses it), but it won't get us even to 10% C.
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