Re: Reactionless Redux

"nunya@xxxxxxx" <Alien8752@xxxxxxxxx> wrote in message
news:1175045716.547195.96220@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
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.

D'oh! Typo. I meant to say they become more useful at lower wavelengths ==
higher frequencies, as opposed to LIGO, which works on very low frequencies.

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.

That is interesting. Perhaps a second item to add to the list of things to
ask Gregory Benford about.

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 conserves linear momentum just fine, I think. It's angular momentum that
gives you problems with teleportation.

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.

I do wonder how you would control the direction of translation, and make
sure that the vectors matched up for everything in the ship.

-l.
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