IBTimes UK ; EmDrive Exclusive: Roger Shawyer confirms MoD interested in space propulsion tech (Full Version)

  • I thought that particle generation conserves momentum? For that purpose the vacuum needs to be polarized and the particle must in average be expelled/ produced to fly opposite the thrust (in line with movement) direction...


    Wasn't the theory originally about massless propulsion?


    I suppose particle generation would conserve momentum. Generate particles from an equal amount of energy, and send them out of one end of the drive. But (1) that's not massless propulsion; it's mass-full propulsion. It's definitely not propellent-less propulsion. (2) I don't think it is what Zephyr_AWT was proposing. (3) I don't think it's what Shawyer is proposing. And (4) where do the keV and GeV to create particles come from?

  • /* It sounds like you are saying that your idea involves the generation of thrust through the emission of photons preferentially in one direction outside of the EM Drive. */


    Nope, absorption inside the EM Drive under exchange of their angular momentum. Why to talk about emission of photons, when the EMDrive only absorbs EM radiation?


    During reflection of light only minute portion of internal momentum of EM wave gets transferred into substrate. This minute portion is connected with momentum of photons and it's too low for to explain the EMDrive thrust. But how the situation will change, once the EM wave gets polarized during it?


    Extraordinary optical momentum and transverse spin-dependent force measured using a nano-cantilever


    Presentation, produced by the authors of the paper, video of the presentation. In contrast to numerous previous studies, which involved radiation pressure forces in the direction of propagation of light or trapping forces along the intensity gradients, they have observed, orthogonal to both of these directions, the extraordinary optical momentum and force.


    The point is that there is more electromagnetic energy in the walls of the cavity than in the cavity itself. Even if the electric fields on each charge in the cavity walls were balanced at the charges themselves, the self-fields of each of the charges constitutes the bulk of the EM energy. Remarkably, the transverse Belinfante momentum and force are determined by the spin (circular polarization) of light rather than by its wavevector. The results demonstrate that the canonical and spin momenta, forming the Poynting vector within field theory, manifest themselves very differently in interactions with matter.

  • Nope, absorption inside the EM Drive under exchange of their angular momentum. Why to talk about emission of photons, when the EMDrive only absorbs EM radiation?


    During reflection of light only minute portion of internal momentum of EM wave gets transferred into substrate. This minute portion is connected with momentum of photons and it's too low for to explain the EMDrive thrust. But how the situation will change, once the EM wave gets polarized during it?


    Direct measurements of the extraordinary optical momentum and transverse spin-dependent force using a nano-cantilever


    You appear to have moved in a direction that is incompatible with the rowboat analogy. You seem to want the rowboat to move forward, but you are willing neither to jettison something with mass, nor to impart opposite an momentum to the water beneath the boat by the action of the oars. Earlier you wrote, "I'd say, these people collect the rain (of photons) and they're redistributing its (mass) water along the board, thus creating the trust. Excessive water evaporates from boat (in form of merely omnidirectional thermal radiation), thus enabling this process to run continuously." It is unclear how your description would cause a rowboat to move forward. Can you rephrase it, so that it becomes clearer? Is the rain coming down at a slant, for example, so that the boat is pushed away from it? Similar to having a sail with the wind blowing into it?

  • You can't model everything with just rain droplets. Note that the photon rocket has similar drag, no matter whether it uses perfect mirror, or just black absorbing surface. This is because the energy of photons (the internal energy of EM field) gets utilized in very small extent and the photons transfer their energy to the spacecraft by redshifting upon reflection or absorption. Only subtle redshifted portion of energy contributes to thrust here. But the introduction of spin decreases the energy of photons way more and the internal momentum of EM field gets transferred to charge carriers of cavity during it.

  • You appear to have moved in a direction that is incompatible with the rowboat analogy.


    @EricW: As I understand the idea, the momentum transfer is free of energy exchange ( proof must be provided). It happens just by distorting e.g. the electron orbit around a nucleous by tilting the spin. But how much energy is need to provide the field, that causes the tilt?

  • You can't model everything with just rain droplets. Note that the photon rocket has similar drag, no matter whether it uses perfect mirror, or just black absorbing surface. This is because the energy of photons (the internal energy of EM field) gets utilized in very small extent and the photons transfer their energy to the spacecraft by redshifting upon reflection or absorption. Only subtle redshifted portion of energy contributes to thrust here. But the introduction of spin decreases the energy of photons way more and the internal momentum of EM field gets transferred to charge carriers of cavity during it.


    In the case of the photon rocket, the thrust is produced from photons that are emitted. The photons go in one direction, and the rocket goes in the other direction. But you have replied above that photons are not what are producing thrust in the EM Drive in answer to a previous question of mine; if that is the case, then we must have something comparable to photons to take their place in order for the analogy to the photon rocket to be meaningful.


    When you mention "drag", there must be something that is producing the drag. What is that thing? Do you agree that in order for thrust to be produced in the EM Drive, it must push off of something, or that something must push off of it? If so, what is that thing, concretely, in your view? It cannot be an abstract property of things: spin, mass, momentum, etc. It must be an actual thing.

  • Spin is not abstract property of things: it's an internal vorticity of field inside particles, the energy swirling at place and giving the particles their mass and charge. The polarization of light introduces the spin into photons, thus making them slow and massive. This effect is rather weak at the case of photons in vacuum, but for quasiparticles spreading at the surface of resonator it has pronounced effect. It gives the mass to these particles into account of electric field intensity, so it represents materialization of energy into matter, absorption of photons and their conversion to massive quasiparticles. The slowing of EMWaves inside EMDrive by their polarization will generate a reactive force, i.e. the thrust.


    /* Do you agree that in order for thrust to be produced in the EM Drive, it must push off of something, or that something must push off of it? */
    It can also suck something, i.e. to absorb and materialize the radiation (energy of translation wave) into a swirling vortices (where the energy rotates at place). Once such a process would run with different speed at both ends of EMDrive resonator, then the thrust will be formed.

  • Spin is not abstract property of things: it's an internal vorticity of field inside particles, the energy swirling at place and giving the particles their mass and charge. The polarization of light introduces the spin into photons, thus making them slow and massive. This effect is rather weak at the case of photons in vacuum, but for quasiparticles spreading at the surface of resonator it has pronounced effect. It gives the mass to these particles into account of electric field intensity, so it represents materialization of energy into matter, absorption of photons and their conversion to massive quasiparticles. The slowing of EMWaves inside EMDrive by their polarization will generate a reactive force, i.e. the thrust.


    Thank you for correcting me. Allow me to rephrase what I said earlier: the thing that is being pushed off of or that is doing the pushing that is generating the putative thrust in the case of the EM Drive cannot be an abstract or concrete property of things: spin, mass, momentum, etc. It must be an actual thing. (I have ceded the adjective "concrete" to you.)


    The effect you point to demonstrates that there are certain materials that by rotating the polarization of light can affect its group velocity. Whether this will cause recoil on the receiving medium is dubious. If there is an imparting of momentum, the frequency of the light (~ energy) will permanently decrease upon the exit of the light from the far end of the spatial light modulator. No permanent shift in frequency after exit from the modulator or other comparable effect, and no imparting of momentum. I did not see any discussion of what happens when the light exits the material. I suspect it looks just like it did before. (Perhaps it has some kind of filtering effect, like that of colored glass.)


    Light has quantized intrinsic spin and orbital angular momentum, and polarization is neither. The alteration of the polarization of light is what those articles describe. Your discussion of spin makes some assumptions about vorticity that many physicists would say goes beyond what we know about intrinsic spin. Although I am very sympathetic to this understanding, we should be skeptical of it.


    With regard to the alteration of polarization of the light and the slowing of its group velocity, let’s assume that your photons are slowing down in the EM Drive and imparting momentum. You still have a big problem to deal with: the photons that are presumably being slowed down are ones that were generated in the microwave cavity, which is part of the drive. If you heave a heavy stone from one end of the rowboat such that it lands in the other end, you will get no net change in momentum for the system as a whole (the rowboat). Your photons are being emitted at one end and slowed down and absorbed at the other, all within the same cavity of the EM Drive. There will be no net thrust.