EmDrive + Focus Fusion = Space Access for all?

[vansig]

i’m not going to address “all propellantless propulsion schemes”.

this thing about weakly interacting massive particles isnt a kitchen sink hypothesis. it should be
testable, as it is probable that there be local anisotropy in the force produced by the thruster,
due to fluctuations of density and velocity of the particles near gravity wells.

[Andrew Palfreyman]

Ein = P t
Eout = 0.5 m v^2
= 0.5 m a^2 t^2
= 0.5 m (F(P)^2 / m^2) t^2
= 0.5 (F(P)^2 / m) t^2

Eout / Ein = ( 0.5 F(P)^2 / ( m P) ) t
= k t

OU occurs for all t > 1/k

Therefore all propellantless propulsion schemes, whereby the motive force is a function of the on-board power, are inherently OU after some characteristic time T

[vansig]

whereas a scheme that depends on favourable external conditions, like solar wind or density & velocity of dark matter, would not suffer this problem

[vansig]

the following is not a smoking gun, since alternative explanations for the annual modulation were proposed recently, but offers some insight into present searches for dark matter
http://people.roma2.infn.it/~belli/belli_DM2012.pdf

[Alex Pollard]

News out of NASA is that their tests of the EM drive space propulsion concept suggest it is a real effect.

http://www.nasaspaceflight.com/2015/04/evaluating-nasas-futuristic-em-drive/

Discussion centres around using a compact reactor as is used in nuclear submarines to enable spacecraft to reach the Moon in as little as 4 hours and Mars in 3 months.

One problem may be that the heat dissipation requirements cannot be met when there aren’t unlimited quantities of sea water to cool the reactor.

But a bunch of 20MW Focus Fusion reactors could offer an excellent power-to-weight ratio yet run very cool, not relying on a steam cycle to operate.

Maybe NASA would be interested in supporting the development of Focus Fusion?

Regardless, taken with the reports of faster-than-light transmission thru the device, I think I can safely say we are now living in the future! Exciting times!

[Andrew Palfreyman]

It is unfortunate that there is no peer review for the pop press 🙂
The FTL assertion is untrue.
I know this from personal email with the experimenters.

[meemoe_uk]

Ein = P t
Eout = 0.5 m v^2
= 0.5 m a^2 t^2
= 0.5 m (F(P)^2 / m^2) t^2
= 0.5 (F(P)^2 / m) t^2

Eout / Ein = ( 0.5 F(P)^2 / ( m P) ) t
= k t

OU occurs for all t > 1/k

Therefore all propellantless propulsion schemes, whereby the motive force is a function of the on-board power, are inherently OU after some characteristic time T

A pertinent question to understanding the em drive :

Why, if when you shoot a 100W laser, are you not pushed back with an equal and opposite thrust equivalent to 100W ?

My answer : photons have very low momentum for the amount of energy they carry, therefore the push back from a 100W laser is negligible.

The point is, as a propellant, a photon is a vast untapped stash of energy. Using them as a propellant is like jettisoning fuel tanks.
Is there a way of converting the energy of a photon into momentum ? This is one of the motivating questions which led to the em drive.

The question also illustrates we already know kinetic energy equations alone aren’t sufficient to explain conservation of energy wrt light, particularly non-relativistic analysis with kinetic energy. Along similar reasoning to Andrew’s analysis and conclusion, light doesn’t exist since the energy used to make photons isn’t accounted for in his non-relativistic kinetic energy equation.

Converting between one form of energy to another should not be a taboo for physicists, so don’t be so quick to dismiss it with a napkin of non relativistic college level physics. Any attempt to understand conservation of momentum and energy in a system involving both light and mass is going to fail if the analysis is non relativistic.

Anyway, here’s another question that should pique interest in the heart of any physicist.

Is the doppler shift reversible?
I don’t mean blueshift as opposed to redshift. I mean: since red shift is caused when an object changes velocity, is a change of velocity causable by red shift?

According to Roger Shawyer, yes. We know for sure the maths works because we already have motion causes redshift maths. Every equation used to theorise the EM drive has already been used to describe doppler red shift.
The argument against the EM drive then becomes : is there a “trap door” aspect to doppler maths, so that it works “motion to red shift”, but not “redshift to motion” ?.
I haven’t read about any such trap door, either in maths analysis or otherwise.

The trick of the EM drive is that its captures red shift in a bottle, which should appeal to Eric since thats what he’s done with quasars with FoFu1.

[Jan Hemmer]

Andrew Palfreyman wrote: There exists a generic problem with all propellantless schemes, and that is violation of both momentum and energy conservation. This leads to the generally true statement that if you can build a propellantless thruster, then you can generate free energy continuously, forever. Mathematically, all that’s required is to define a relationship between power input and thrust (you can pick linear or anything else you like). Then write down the energy budget for acceleration in free space, and compare kinetic energy to total input energy. You’ll find there’s a breakeven velocity (or equivalently distance or time), above which the kinetic energy exceeds the total input energy. So not only is a propellantless drive great for space travel, it solves all our energy problems too!

At first sight I would say the same reasoning goes for a conventional rocket.

[Author]

Posts