[Diaspora] Bringing Magsails and plasma sails (mini-magnetosphere plasma propulsion (M2P2) and Diaspora

[Trey Palmer]

All,
In my rummaging around for images that might to make some counters for the
space combat mini-game, I've been getting mildly re-acquainted with
Transhuman Space. And going a bit more deeply into the space ship details
than before.
First, what tech level would the Transhuman Space setting be? They're
terraforming Mars, mining Saturn for He3, etc. To me, that puts them firmly
in the T1 category, IMO.

Second, ThS had 2 drives that might be very useful in Diaspora - Magnetic
Sails and Plasma Sails.

Magnetic Sails
http://www.sjgames.com/gurps/Roleplayer/Roleplayer29/MagSails.html and
http://en.wikipedia.org/wiki/Magnetic_sail have the major advantage of
requiring no reaction mass, only a magnetic field to push off of. Like say,
the ones found in Jovian planets, or stars. They're slow, but ridicuously
efficient. And without a magic reactionless drive, they're about as good as
you can get. Useless for combat though. Still, I think folks could use them,
especially for cargos that don't have a tight deadline attached. Why? To
quote from the old Roleplayer article:


>  In addition to this outward (radial) acceleration, a magsail can also
> generate a sideways (tangential) thrust of up to 30% of the value calculated
> above. By changing the angular momentum around the sun, very sophisticated
> interplanetary orbits can be used that would be impractically expensive for
> reaction engines, and utterly impossible for solar sails.
>
> A magsail cannot thrust inward, toward the sun. It can "tack," however,
> using tangential thrust to lower its orbital speed, and fall sunward. The
> acceleration of Sol's gravity at various distances is given in the table.


In short, they save on fuel. A lot. This makes *really* extended range
vehicles possible. Triple or quadruple what's available under the current
rules. So, a *Magnetic Sail* Stunt makes a lot of sense,. And what's better,
there's no reason they couldn't overburn if they needed too...

Plus, the sails can be furled inside the ships frame protecting them. Though
I could see "Jammed magsails" as a consequence.

Now, then there is the plasma sail, the magnetic sail's prettier and more
efficient cousin.

>
>  In order to reduce the size and weight of the magnet of the magnetic
> sail, it may be possible to inflate the magnetic field using a plasma, in
> the same way that the plasma around the earth stretches out the Earth's
> magnetic field in the magnetosphere. In this approach, called
> mini-magnetospheric plasma propulsion (M2P2), currents running through the
> plasma augment and partially replace the currents in the coil. This is
> expected to be especially useful far from the sun, where the increased
> effective size of a M2P2 sail compensates for the reduced dynamic pressure
> of the solar wind. ... The plasma pressure stretches the magnetic field and
> inflates a bubble of plasma around the spacecraft. The current in the plasma
> in this case augments and partially replaces currents in the coils. The
> plasma then generates a kind of minaturised magnetosphere around the
> spacecraft, analogous to the magnetosphere that surrounds the earth. The
> protons and electrons which make up the solar wind are deflected by this
> magnetosphere, and the reaction accelerates the spacecraft. The thrust of
> the M2P2 device would be steerable to some extent, potentially allowing the
> spacecraft to 'tack' into the solar wind, and allowing efficient changes of
> orbit.
> In the case of the (M2P2) system the spacecraft releases gas to create the
> plasma needed to maintain the somewhat leaky plasma bubble.
> ... calculates a specific impulse of 200 kN·s/kg (roughly 50 times better
> than the space shuttle main engine). These calculations suggest that the
> system requires on the order of a kilowatt of power per newton of thrust,
> considerably lower than electric thrusters, and that the system generates
> the same thrust anywhere within the heliopause because the sail spreads
> automatically as the solar wind becomes less dense.
>

Again, this offers up the possibility of some very efficient and extended
range space craft, that can still use normal engines.
Plus, both of these can act as beam riders, accelerating or decelerating by
using high powered particle beams from other places. With this, you could
even have a basic interstellar 'slow boat' if you wanted one to turn up in
your game.

So, thoughts from the peanut gallery on these? Worth having as a stunt for
those that want 'em? Or do they break the setting too much?
--
Bowden "Trey" Palmer | Tango Romeo Echo Yankee DOT Poppa Alpha Lima Mike
Echo Romeo AT Golf Mike Alpha India Lima DOT Charlie Oscar Mike
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