http://www.ibtimes.co.uk/emdrive-warp-drive-are-two-different-things-nasas-still-working-emdrive-1501268I'm linking to this because it mentions us, is mostly accurate (not completely) and is fair and balanced. It has lots of quotes from Shawyer himself. The final comment from him about the West has me extremely unnerved.
I'd say both the article above and several of the commenter above clearly have the wrong idea about which Eagleworks project is more likely to pan out into anything.A warp drive does not break any obvious laws of physics, and is merely an esoteric construct that happens to require yet undiscovered forms of matter, but is clearly allowed by GR if these forms of matter are allowed. The Alcubierre metric is straightforward enough to show up as a source of homework exercises in general relativity courses.The EM-drive on the other hand does break some rather important laws of physics, and otherwise should set off enough red lights that calling it a cargo cult is warranted.
With no trouble at all. That is why the EM Drive stops at two-thirds of the speed of light.Similar rules apply to cars, only with lower top speeds.
The second generation engines will be capable of producing a specific thrust of 30kN/kW. Thus for 1 kilowatt (typical of the power in a microwave oven) a static thrust of 3 tonnes can be obtained, which is enough to support a large car. This is clearly adequate for terrestrial transport applications.The static thrust/power ratio is calculated assuming a superconducting EmDrive with a Q of 5 x 109. This Q value is routinely achieved in superconducting cavities.Note however, because the EmDrive obeys the law of conservation of energy, this thrust/power ratio rapidly decreases if the EmDrive is used to accelerate the vehicle along the thrust vector. (See Equation 16 of the theory paper). Whilst the EmDrive can provide lift to counter gravity, (and is therefore not losing kinetic energy), auxiliary propulsion is required to provide the kinetic energy to accelerate the vehicle.
Quote from: A_M_Swallow on 05/16/2015 01:31 amWith no trouble at all. That is why the EM Drive stops at two-thirds of the speed of light.Similar rules apply to cars, only with lower top speeds.I don't think you're following me.Shawyer's FAQ #18 deals with terrestrial applications:QuoteThe second generation engines will be capable of producing a specific thrust of 30kN/kW. Thus for 1 kilowatt (typical of the power in a microwave oven) a static thrust of 3 tonnes can be obtained, which is enough to support a large car. This is clearly adequate for terrestrial transport applications.The static thrust/power ratio is calculated assuming a superconducting EmDrive with a Q of 5 x 109. This Q value is routinely achieved in superconducting cavities.Note however, because the EmDrive obeys the law of conservation of energy, this thrust/power ratio rapidly decreases if the EmDrive is used to accelerate the vehicle along the thrust vector. (See Equation 16 of the theory paper). Whilst the EmDrive can provide lift to counter gravity, (and is therefore not losing kinetic energy), auxiliary propulsion is required to provide the kinetic energy to accelerate the vehicle.This reduction in specific thrust is important to public acceptance of Shawyer's claim because otherwise his device would be more easily recognized as a free energy machine. His attempt to enforce energy conservation is not invariant under Galilean transformation (more on that in a later post), but that's a point lost on the layman who doesn't understand the issues raised by a reactionless drive.What we should all be asking after reading this interview is, if specific thrust drops so rapidly upon acceleration along the thrust vector that his proposed flying car can be levitated by EmDrive but requires auxiliary engines for propulsion, then how is it able to accelerate a spacecraft to 2/3 c in 10 yr.? Let's crunch some numbers and figure out what kind of power density he is envisioning for its power source.He addresses the reduction of specific power (thrust per unit power = T/P) with velocity (due to acceleration along the thrust vector of the EMDrive) starting on page 8 of his Theory Paper. Combining equation (16) with his formulas for thrust and taking the limit on Q gives (T/P)max < 1 / v, with the maximum specific thrust approaching the inverse of the velocity as Q increases without bound. Figure 3.2 plots the specific thrust against Q for a velocity of 3 km/s and shows it maxing out at 333 mN/kW.Assume that our spacecraft of mass m and power P starting from rest is somehow able to achieve its maximum permitted specific thrust at all times. Combing T/P = 1/v and T = m v-dot (where v-dot = dv/dt, acceleration) yields the differential equation v-dot = (P/m) v-1 with the initial condition v(0) = 0 and solution v(t) = sqrt(2Pt/m). Plugging in v(10 years) = 2/3 c and solving for power density gives P/m = (2/90) c2 / yr = 63.3 MW / kg. But that isn't even taking relativity into account. 2/3 c is not highly relativistic, but it does yield a Lorentz factor of 3/sqrt(5) = 1.34, so doing the calculations relativistically reveals a required power density of 97.3 MW / kg. Accounting for electrical losses, payload, and the mass of the EmDrive itself will further increase the required power density of the spacecraft's power source.Proponents of VASIMR driven 39 day trips to Mars are rightly taken to task for not pointing out that their plan requires a power source capable of generating an astounding 1 kW / kg. Shawyer's zero to 2/3 c in 10 years spacecraft needs a power source with five orders of magnitude greater power density.~Kirk
Shawyers equations are in my opinion rubbish. If you can float a car, that means you can accelerate at the rate of at least 10 m/s^2 (1g is 9.8m/s^2). If you can do this then you can slowly float higher and higher and accelerate as gravity grows weaker and acceleration wouldn't change from 10m/s^2...
His distinction between hovering (unlimited) and accelerating horizontally at 9.8 m/s^2 (limited due to reduction in specific thrust) would appear to violate the equivalence principle.~Kirk
Shawyer's a nut. That whole The West is slowly dying, and that's all for the good' business is wild speculation. His math has been shown to be nonesense by many people smarter than him, and the boffins in the other thread are closing in on more conventional and mundane explanations for EMDrive thrust. End of.
http://2.bp.blogspot.com/-C1cgolGV6r0/VUCw2IWncwI/AAAAAAAACWQ/8RhssZGNGKA/s1600/22.JPG
One possible explanation for the optical path length change is that it is due to refraction of the air. The NASA team examined this possibility and concluded that it is not likely that the measured change is due to transient air heating because the experiment’s visibility threshold is forty times larger than the calculated effect from air considering atmospheric heating.