"Alain Fournier" wrote in message ...

On Sep/7/2020 at 19:41, Greg (Strider) Moore wrote :
"Alain Fournier" wrote in message ...

On Sep/7/2020 at 11:05, Greg (Strider) Moore wrote :
wrote in message
...

Gravity, Gizmos, and a Grand Theory of Interstellar Travel:

"Woodward’s MEGA drive is different. Instead of propellant, it relies
on
electricity, which in space would come from solar panels or a nuclear
reactor. His
insight was to use a stack of piezoelectric crystals and some
controversial—but he
believes plausible—physics to generate thrust. The stack of crystals,
which store
tiny amounts of energy, vibrates tens of thousands of times per second
when zapped
with electric current. Some of the vibrational frequencies harmonize
as they roll
through the device, and when the oscillations sync up in just the
right way, the
small drive lurches forward."

See:

https://www.wired.com/story/mach-eff...tellar-travel/


What are the odds of this actually working?

https://www.scientificamerican.com/a...ic-propulsion/
is where I first read about this. (paywalled sorry).

This is one of those, "I HIGHLY doubt it'll work, but it's just close
enough to the edge of physics as we know it, it's probably worth some
cautious funding."

I think it's sort of like the proposed Alcubierre warp drive, unlikely
to actually work or be practical, but worth some investigation "just in
case".

I wouldn't put the Alcubierre warp drive in the same category. I think
one could build a working Alcubierre warp drive if one had a suitable
source negative mass exotic matter. Their is some uncertainty, but the
physics behind Alcubierre drive have a reasonable chance of being
correct. Of course finding the source of exotic matter is a problem :-)

Woodward's MEGA drive (and calmagorod's PNN) are on an opposite track.
They have all the hardware to build their gizmos, but they don't seem to
have the physics on their side.


I disagree a bit, but let me explain why.

As you say, basically we COULD build Alcubierre's drive if we had
something that appears to be mythical.
But remember, his first design required something like a negative mass
greater than the mass of the known universe. Later designs reduced it to
3 solar masses.
Now they're down to (depending on assumptions) a few milligrams to a few
hundred kilograms.
My point is, as we do more research, we actually get closer to a
buildable design.

Are we really closer to having a few milligrams of pixie dust than we are
to having 10^62 kg of pixie dust? :-)


No, but we're probably closer to finding a way of "oh look if we manipulate
it this way, we actually just need a few milligrams of antimater" or
something that actually is known to exist :-)

That said, I'll admit, Woodward's MEGA drive does seem to have the
opposite problem, it appears we can physically build it, but the physics
may not work.
In either case, I'm ok with throwing some money at both "just in case".

So am I, not too much money but some money yes. And what I wrote just
before this paragraph might not show it, but I favour much more throwing
money at Alcubierre's drive than throwing some at Woodward's MEGA drive.
Even if Alcubierre's drive is never built, it is very interesting to know
that a few negative milligrams of exotic matter would be enough to
transport an atom faster than light.

About throwing money at Alcubierre's drive, I wouldn't throw a tonne of
money at it, but if I could, I certainly would throw a negative tonne of
money at it :-)


Of course what's really happening is that Alcubierre's inventing Warp Drive
and Woodward is inventing Impulse Drive.
So we're really just one step from the USS Phoenix :-)


Alain Fournier

--
Greg D. Moore http://greenmountainsoftware.wordpress.com/
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