Re: Reactionless Redux

On Mar 26, 3:46 pm, "Logan Kearsley" <chrono.sur...@xxxxxxxxxxx>
wrote:
"Erik Max Francis" <m...@xxxxxxxxxxx> wrote in messagenews:aKCdnXfeEcybrZXbnZ2dnUVZ_u2mnZ2d@xxxxxxxxxxxxxxxx

n...@xxxxxxx wrote:
[...]
Hence I'd expect any matter to _feebly_ feel a very powerful
graviton beam, but only propitiously arranged (per the wavelength of
the beam) very dense masses would absorb any great part of the beam
energy.

Right, it would feel it, in terms of tiny stresses that propagate at the
speed of light through the material. Detecting these stresses is one
proposed way to detect gravitational radiation (and thus gravitons).
However, it's awfully hard, which is why we take other proposed
mechanisms more seriously, like LIGO's approach.

LIGO is only good for low-frequency gravitational waves, though. If we're
going to be generating them artificially for propulsive purposes some tuning
capacity would probably be desirable.
Weber bars and other sorts of detectors become more useful at lower
frequencies and higher amplitudes, I think.

M'kay, I thought Weber bars were only good for relatively (whatever
that means in this context) high-frequency work.

Well, reversibility
seems to imply that whatever one uses to emit such a pulse ought to
also be able to absorb it, no?

I wouldn't want to drive my gravity-powered flitter into the wake of
a gravity-powered battleship; my drive might get slightly scrambled!

Well, one big grey area we're talking about here is that we haven't
specified a mechanism by which confined (confused?) beams of
gravitational radiation could be emitted in the first place. I don't
know enough general relativity to know whether that's even theoretically
possible; all the natural sources (asymmetrical stellar collapse,
neutron star and black hole collisions, etc.) shouldn't emit them
directionally.

I should make a direct reply to Erik but Google groups is being
difficult, dropping posts even after telling me it was "successful",
so I'll push my luck with a twofer. Anyway, I didn't mean time
reversibility, I meant functional reversibility, as in using what
amounts to a gravitational wave transmitting antenna as a receiving
antenna.

Enough people seem to think that there are ways to build compact gravity
wave emitters for lots of papers on the subject to be available on ArXiv.
The two that stick in my mind are applying high-intensity jerks to
circularly arranged masses (nothing ever rotates or moves beyond a few
micrometers, but an acceleration wave travels around the circle, simulating
orbits of two massive bodies), and forcing cooper pairs to undergo energy
transitions at the junction of two kinds of semiconductor where angular
momentum changes by +/-2. There's a paper on the latter athttp://arxiv.org/pdf/physics/0410022.

Very cool, especially if it actually does explain the non-
replicability of Podkletnov, Liu, et al.

BTW the high-intensity jerk tech sounds very similar to Forward's
"protogravitic" stuff; he mentions that the fluid neutronium would
have to constantly accelerate to produce a g field, and his cheela
somehow "overcame" the obvious limitations (though he wisely didn't
say how).

The thing that got me wondering about using gravitational waves for
propulsion was discovering several papers in the mix stating that non-linear
effects come into play for interfering gravitational waves that can result
in coulomb-like fields and singularities. Which would pull the source
towards them, causing the fields to move, producing more gravitational
radiation (presumably with much larger amplitude than the original output of
one's generator)... and then the question, does the net emission of gravity
waves from that system allow for conservation of momentum?

All of us may be at sea here; ISTR that when you add up the masses
of a gravitationally-bound system, and add the gravitational energy
holding the system together, it still doesn't quite add up to what
you'd get when it all radiates away as the satellites spiral out to
infinity. Either something somewhere isn't conserved, or it's
conserved in a rather strange (to me) way.

Now, many times we run across SF FTL drives involving turning all
the particles that make up a spacecraft into tachyons, then reverting
to bradyons at the destination. I'm suggesting something similar
except with superpartners of all the ship's constituent particles
(assuming they maintain the same relationships with each other their
non-superpartners do), done repeatedly. I don't think it would produce
FTL.

Well, I'm not sure how this qualifies as a reactionless drive, as we've
been discussing in this thread. It's still reaction _momentum_ that is
technically needed, not just mass. Bosons, as we've been talking about,
have momentum (because they have energy, but not mass, as E^2 = m^2 c^4
+ p^2 c^2). Your supersymmetric equivalent bosons would still have
momentum.

No, no partner particles are ejected; all the particles that make up
the ship and contents switch from particle to superpartner
"simultaneously", then switch back; they're unchanged except they're
now all a little bit that --> way from where they were.

I know, it doesn't conserve linear momentum. I didn't make it up, I
just noticed it go by when SuSy first made a public splash (I think it
was in SciAm in the late 80's) and wondered why nobody jumped on that.
Apparently it's just that if SuSy is correct, then some or all of what
we think of as conservation laws will need, if not complete rewriting,
some riders attached.

It depends on the nature of the translation between supersymmetric partners,
which isn't made particularly clear in the web page previously referenced.

I'd have ref'd a better explanation but couldn't find one.

Does it involve a particle dissapearing in one place and its superpartner
showing up elsewhere (reactionless drive), or does it involve a particle
transforming into its superpartner (and emitting something else to balance
momentum), which then goes shooting off at the speed of light before
transforming back again (light-speed reaction drive).

As I said, AFAICT it does not explicity involve other particles that
carry momentum away, it's solely due to symmetries not being what
we're used to if SuSy is correct; a two-way transformation involves as
a direct consequence a spatial translation. However, I'm guessing
there'll have to be some kind of energetic effort applied to get a
ship's worth of particles to synchronized-switch back and forth, but
whether that would have to be direction-selective and thus amount to
an exhaust is quite beyond me.


Mark L. Fergerson

.

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