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Journal by takyon

This is what some people really believe:

If EMdrive is real and scales with Q factor then we get almost Star Trek level Technology (or Stargate Atlantis, going by the picture)

An EM-Drive with a q factor of 3 billion would need required is 20 MWe for the 1 gee acceleration spacecraft. 20 MWe is more than any reactor ever orbited but well within known design parameters.

An EM-Drive with a q factor of 30 billion would need required is 2 MWe for the 1 gee acceleration spacecraft.

An EM-Drive with a q factor of 60 billion would need required is 1 MWe for the 1 gee acceleration spacecraft.

An EM-Drive with a q factor of 300 billion would need required is 200 KWe for the 1 gee acceleration spacecraft.

For 30 to 300 billion q factors the power levels for a 1000 ton vehicle drop to the level where, you could use solar power for Emdrive to counter gravity on earth. It would be virtual anti-gravity. Structures that would be possible would not just be flying cars or floating antigravity but flying cities.

Gee = G.

Even the millinewtons of thrust being measured currently are disputed.

I won't say that EmDrive won't kill thermodynamics, because the expansion of the universe is apparently accelerating. Maybe that is an energy source that is being tapped into by the magic thruster. In which case turning on enough EmDrives would save the Universe by preventing the Big Freeze/Rip.

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The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
  • (Score: 1) by khallow on Thursday June 29 2017, @01:26AM (2 children)

    by khallow (3766) Subscriber Badge on Thursday June 29 2017, @01:26AM (#532732) Journal
    As I see it, the big limit is power out must be less than power in. Being able to accelerate 1 kg for 9.8 m/s^2 continuously would yield enormous power output over time in outer space. In the Newtonian approximation, acceleration, "A" is constant and kinetic energy goes up as as the square of velocity (1/2 m*v^2) which would be A*t. So the average power output over time t would be 1/2 m*A^2*t^2/t = 1/2 m*A^2*t. Notice how that is linear with time. The way rockets get around this is that mass m declines tremendously as the rocket accelerates with that mass left in an exhaust trail traveling much slower than the rocket (or even in the opposite direction). This keeps the average power term bounded from above by the energy contained in the propellant system. We don't have a similar restriction for this EM engine as it is presented here. No mass is lost except a minute amount due to the generation of power (which is extremely small). Hence, the power output of the system must be huge at these extremely high "Q" values compared to the power input. At that point, you're generating power at extremely high ROI on initial power input.

    Either it happens, but somehow we have never seen it in nature, or the other parameters change over time in a way to bound the power output of the system. That means either m or A has to decline as the EM drive continues to accelerate. And for this high a level of Q, that means a very sharp decline in m or A.
  • (Score: 2) by kaszz on Thursday June 29 2017, @01:47AM (1 child)

    by kaszz (4211) on Thursday June 29 2017, @01:47AM (#532744) Journal

    What you say is that: P = 1/2 * m * a² * t
    Where:
      P = Power [W]
      m = Mass [kg]
      a = Acceleration [m/s²]
      t = Time [s]

    It seems backwards that for a constant acceleration, the required power input increases linearly with time. Seems like something is up, question is what and how.

    So a 100 kg load would need:
    1s: 4821 W
    2s: 9643 W
    3s: 14 464 W
    4s: 19 286 W

    That would certainly not make any battery feasible.

    Also, if power is shut off. Does the power requirement start at t=0 again? What count as time reference? how does physics know when you started?

    • (Score: 1) by khallow on Thursday June 29 2017, @02:12AM

      by khallow (3766) Subscriber Badge on Thursday June 29 2017, @02:12AM (#532766) Journal

      Where:
      P = Power [W]

      P is average power over time t.

      Also, if power is shut off. Does the power requirement start at t=0 again?

      No, because you're traveling with velocity.

      What count as time reference? how does physics know when you started?

      Good problems with the approach from attempting to maintain consistent physics. This might be an alternative way to develop relativity without assuming a speed of light. Ultimately, it's a problem in any frame of reference. Constant acceleration with no loss of rest mass means increasing power.