4 ms·

That conclusion is surprising to me. If the drive has a source of reaction mass then it works kind of like a jet-ski, it scoops reaction mass from the surround

That conclusion is surprising to me. If the drive has a source of reaction mass then it works kind of like a jet-ski, it scoops reaction mass from the surroundings and shoots it out accelerated. In a way it almost has to work and it would take effort to screw it up. Sure the performance may be awful but it should be possible to get it above zero, unlike reactionless drives which violate established laws of physics.

rrss 7y ago
If the reasoning there is sound (and it makes sense to me), the closer analogy is trying to propel a canoe by rolling a cannonball along the bottom. It will work for a while, but eventually the cannonball hits the back of the canoe. No dice.
- aey 7y ago
  I believe this canoe is picking up cannonballs along the way.
  - ScottBurson 7y ago
    It seems that way at first. The problem is that each of those cannonballs is tethered to the canoe by a long bungee cord.
    - aey 7y ago
      Ah, because the electrical field loops? Just thinking of the top of my head, couldn’t this pulse? Basically capture material then shoot it out?
ScottBurson 7y ago
Maybe the best way to understand it intuitively is that the drive would actually work for a little while after you first turn it on, but as it shoots charged particles in opposite directions, it creates a field in its region of space that eventually gets strong enough to pull it backwards by the same amount that its thrust pushes it forwards. By continuing to add energy it could continue to move, but it can't continue to accelerate. The best it could do, perhaps, is to accelerate to a certain velocity, then turn off its generator and discharge its plates so it now has no net field, and then coast to its destination. Probably part of the confusion here is that a dipole does have a nonzero field even though the net charge on it is zero. Dipole fields are often negligible, particularly as they fall off faster than monopole fields -- 1/r^3 rather than 1/r^2 -- but ignoring the dipole field is another familiar approximation that doesn't hold in this case.

rrss 7y ago

If the reasoning there is sound (and it makes sense to me), the closer analogy is trying to propel a canoe by rolling a cannonball along the bottom. It will work for a while, but eventually the cannonball hits the back of the canoe. No dice.

aey 7y ago
I believe this canoe is picking up cannonballs along the way.
- ScottBurson 7y ago
  It seems that way at first. The problem is that each of those cannonballs is tethered to the canoe by a long bungee cord.
  - aey 7y ago
    Ah, because the electrical field loops? Just thinking of the top of my head, couldn’t this pulse? Basically capture material then shoot it out?

ScottBurson 7y ago

Maybe the best way to understand it intuitively is that the drive would actually work for a little while after you first turn it on, but as it shoots charged particles in opposite directions, it creates a field in its region of space that eventually gets strong enough to pull it backwards by the same amount that its thrust pushes it forwards. By continuing to add energy it could continue to move, but it can't continue to accelerate. The best it could do, perhaps, is to accelerate to a certain velocity, then turn off its generator and discharge its plates so it now has no net field, and then coast to its destination. Probably part of the confusion here is that a dipole does have a nonzero field even though the net charge on it is zero. Dipole fields are often negligible, particularly as they fall off faster than monopole fields -- 1/r^3 rather than 1/r^2 -- but ignoring the dipole field is another familiar approximation that doesn't hold in this case.