in a previous thread, i suggested using solar sail thinking that it
worked off solar wind. after a little research i discovered that a
better name for them was light sail, as they actually worked off
photon, usually from the sun. one of the theories concerning them is
to use a earth based 600 gigawatt laser to speed a large ship to the
stars.
2 solar powered satellite would be launched into an orbit just inside
of Venus. these would not use solar cells to power the laser, but
would be light pumped (that is they get the energy directly from
light) by the sun. in the shadow of the satellite a radiator would
release the waste heat from the laser. since the laser would be much
more intense than the sunlight, the effect would be about 1000 times
greater. this would drop the size of the sail to about 1 mile across,
and the weight to about a ton and a half. it would take about three
years to move a 100000 tone asteroid into the proper place. two
satellites would mean that you could have a new asteroid in earth
orbit every 1.5 years, give or take due to the location of the
satellites and their specific orbits. it would take at least that
long to mine the asteroid.
On 5/23/06, Robert wrote:
> in a previous thread, i suggested using solar sail thinking that it
> worked off solar wind. after a little research i discovered that a
> better name for them was light sail, as they actually worked off
> photon, usually from the sun. one of the theories concerning them is
> to use a earth based 600 gigawatt laser to speed a large ship to the
> stars.
(...)
magsail. That would be a "sail" composed by a magnetic field that
would catch solar wind particles (and their momentum), thus getting
propulsion. Perhaps it is an even simpler approach to an asteroid or
meteoroid, for I guess that the problems with asteroid rotation would
be of much easier solution. (Though I may be wrong.)
unfortuately, even if you catch the entire energy from their momentum,
it would still be much lighter than that from light, and the equipment
to generate those fields are much heavier that those needed for the
light sails. I check these out too. the rotation of both the meterorid
and asteriod would have to be stopped inorder to be moved. in the
case of meteriods, the light sail would be between it and the sun,
which would stop it from losing material to the solar wind and heat.
wrote:
On 5/23/06, Robert wrote:
> unfortuately, even if you catch the entire energy from their momentum,
> it would still be much lighter than that from light, and the equipment
> to generate those fields are much heavier that those needed for the
> light sails. I check these out too. the rotation of both the meterorid
> and asteriod would have to be stopped inorder to be moved. in the
> case of meteriods, the light sail would be between it and the sun,
> which would stop it from losing material to the solar wind and heat.
(...)
have a better thrust-to-mass ratio than lightsails. Solar wind is
relatively strong, for instance being perhaps the main force directing
a comet tail.
--- In spacesettlers@yahoogroups.com, "Lucio de Souza Coelho"
wrote:
>
> Well, the references that I know point that magsails would probably
> have a better thrust-to-mass ratio than lightsails. Solar wind is
> relatively strong, for instance being perhaps the main force
directing
> a comet tail.
>
this was something i believed at one point, but have not found any
evidence to support it. other areas have said it would not have that
streagth. if you have a link that supports that, please allow me to
follow up on it.
Energy delivered per square meter of cross-section is higher for photons,
but the magsail's magnetic field can cover a larger cross-sectional area for
a given mass of equipment. Magsails only become cost-effective if one can
make a superconducting wire 150 KM long, that can operate in direct
sunlight. As superconductor technology is not there yet, the lightsail is a
more effective choice at the moment. An alternative design, that uses a
cloud of charged gas instead of a wire loop, has been proposed as well, and
it seems promising.
has come up more than once, and seems to be an elegant solution. The only
issue is the total reliance on targeting accuracy, and therefore timing.
Aiming a laser at something that is potentially light-hours away is a dicey
proposition, especially when that object accelerates.
On 5/23/06, Robert wrote:
--- In spacesettlers@yahoogroups.com, "Alexander Roderick"
wrote:
>
>...As superconductor technology is not there yet, the lightsail is a
> more effective choice at the moment...
>
that's why I'm proposing the solar sail, it can be done now.
>
> Your idea of using a solar-powered satellite to deliver power via a
laser
> has come up more than once, and seems to be an elegant solution.
The only
> issue is the total reliance on targeting accuracy, and therefore
timing.
> Aiming a laser at something that is potentially light-hours away is
a dicey
> proposition, especially when that object accelerates.
>
i guess i did not make it clear, I'm talking about neos which by
definition are inside the orbit of mars at the apogee. earth is about
8 light minutes from the sun and mars would be about 16. since venis
is about 4, that means the farthest the laser would be from the sail,
would be maybe 20 minutes top. since it would be only decelerating or
accelerating in a staight (orbital) line (any manuver would require
that the beam be turn away, before the sail could be changed) the
potition of the sail would be easy to calcuate the proper angle to
send the beam. the great majority of time the laser satalite would be
on the same side and the asteroid would be inside or near earths
orbit. that would mean a seperation of maybe 5 to 10 light minutes.
On 5/24/06, Robert wrote:
(...)
> i guess i did not make it clear, I'm talking about neos which by
> definition are inside the orbit of mars at the apogee. earth is about
> 8 light minutes from the sun and mars would be about 16. since venis
> is about 4, that means the farthest the laser would be from the sail,
> would be maybe 20 minutes top. since it would be only decelerating or
> accelerating in a staight (orbital) line (any manuver would require
> that the beam be turn away, before the sail could be changed) the
> potition of the sail would be easy to calcuate the proper angle to
> send the beam. the great majority of time the laser satalite would be
> on the same side and the asteroid would be inside or near earths
> orbit. that would mean a seperation of maybe 5 to 10 light minutes.
(...)
the Sun and Mars is 13.
--- In spacesettlers@yahoogroups.com, "Lucio de Souza Coelho"
wrote:
>
> Just being picky with your numbers: Venus is six light-minutes from
> the Sun and Mars is 13.
>
the distance between the earth and sun. and mars as being twice as
far. i guess venus is a lot closer to earth than the sun and mars is
much less than twice earths orbit. earth is 8 light minutes, so venus
orbit is about 2 light minutes away. and mars is 5. still the
generalization of 20 light minutes for the farthest the beam would
have to travel is still on.
this would make it better for the closest approach though. since the
laser would be just inside venus orbit, perhaps at 5.5 lm's from sun
and the neos would be for the most part between the two planets most
of the time.
A twenty minute lag, plus another twenty before you could see the result, is
still a hard shot. Not completely unfeasable, but hard. Imagine if the
throttle on your car took forty minutes to respond to an input. (I know it's
not that great an analogy, as the accelerations involved are tiny, but
still.)
--- In spacesettlers@yahoogroups.com, "Alexander Roderick"
wrote:
>
> A twenty minute lag, plus another twenty before you could see the
result, is
> still a hard shot. Not completely unfeasable, but hard. Imagine if
the
> throttle on your car took forty minutes to respond to an input. (I
know it's
> not that great an analogy, as the accelerations involved are tiny,
but
> still.)
>
your talking about a steady acceleration of a fraction of an inch per
second. in 40 minutes, the change in speed would be 48 inches per
second. i really dont think the computer would have any trouble
tracking to postion of the sail which is a mile in size.