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Jens
2012-Sep-21, 02:38 AM
* Just partly kidding, there... anyone who controlled a laser powerful enough to drive a starship could effectively control the Solar System, so it would indeed be a prime target for any would-be rebels.

Not entirely to the point, but I don't see why it would be a prime target, since it has not strategic value whatsoever. Who cares if they stop accelerating a spaceship that's traveling to some distant place from whence it will never return? More likely would be that the rebels do something else, and the empire decides to stop funding the lasers in order to support the war effort.

Noclevername
2012-Sep-21, 03:08 AM
Not entirely to the point, but I don't see why it would be a prime target, since it has not strategic value whatsoever. Who cares if they stop accelerating a spaceship that's traveling to some distant place from whence it will never return? More likely would be that the rebels do something else, and the empire decides to stop funding the lasers in order to support the war effort.

A weapon, or set of weapons, that powerful with no strategic value? Why would you come to that conclusion?

Noclevername
2012-Sep-21, 03:18 AM
If the laser's controllers decide to take the beams off a distant target, it will probably be to turn them on other, closer targets. The lasers can hit something light-years away and moving while the lasers themselves orbit the Sun. If they can do that, they are effectively already weaponized-- no modifications needed to vaporize a rebel stronghold, be it a ship, asteroid or planet-based.

Noclevername
2012-Sep-21, 03:35 AM
If the laser's controllers decide to take the beams off a distant target, it will probably be to turn them on other, closer targets.

I take that back-- they can probably do both at once, since not all the lasers will be able to fire at the starship in the same direction at once--the sun will be in the way half the time, so a ring of laser stations around the solar equator will probably be necessary to maintain a constant rate of thrust. The laser banks will include some under maintainance and some in their cool-down phase, so there will be some to spare at any given time.

Ara Pacis
2012-Sep-21, 04:40 AM
I take that back-- they can probably do both at once, since not all the lasers will be able to fire at the starship in the same direction at once--the sun will be in the way half the time, so a ring of laser stations around the solar equator will probably be necessary to maintain a constant rate of thrust. The laser banks will include some under maintainance and some in their cool-down phase, so there will be some to spare at any given time.

How about we use nuclear powered lasers and line them up and each one pushes another laser platform farther out of the system while the front lasers illuminate the interstellar vehicle's light sail.


If the laser's controllers decide to take the beams off a distant target, it will probably be to turn them on other, closer targets. The lasers can hit something light-years away and moving while the lasers themselves orbit the Sun. If they can do that, they are effectively already weaponized-- no modifications needed to vaporize a rebel stronghold, be it a ship, asteroid or planet-based.

Laser light will spread out after a bit. Some, like Isaac Kuo and myself, have discussed using zone plates to refocus the beams and extend the range. That might be something to consider using for optical wavelengths too. You may lose a bit of light at the ZP but a lot of that would have been lost to the spread anyways. The point is that if you use a ZP then you may have difficulty using the laser on closer targets due to beam spread or the ability or length of time to get the ZP (or a second ZP) positioned.

Noclevername
2012-Sep-21, 04:50 AM
How about we use nuclear powered lasers and line them up and each one pushes another laser platform farther out of the system while the front lasers illuminate the interstellar vehicle's light sail.

How much nuclear material would it take to do that?




Laser light will spread out after a bit. Some, like Isaac Kuo and myself, have discussed using zone plates to refocus the beams and extend the range. That might be something to consider using for optical wavelengths too. You may lose a bit of light at the ZP but a lot of that would have been lost to the spread anyways. The point is that if you use a ZP then you may have difficulty using the laser on closer targets due to beam spread or the ability or length of time to get the ZP (or a second ZP) positioned.

A zone plate for optical lasers would basically be a massive Fresnel lens, collecting and collimating the beams from all the laser banks. It would have to be in the outer Solar system to keep it aimed at the lightship in a very slow orbit--and even then it would need frequent maneuvering. And it would have to be expanded as the ship gets more distant.

But those banked lasers would still pack a wallop even at distant range.

Noclevername
2012-Sep-21, 05:32 AM
Let me give an example. Suppose our intrepid rebels are burrowed deep inside a sturdy asteroid. The whole laser system is designed to run for decades at a time. It can simply focus a fraction of its power onto the rock, slowly heating it until it's cherry-red and unsuited to human habitation. They don't need to be any more precise or focussed than they have to be to hit the Fresnel lens. An icy KBO would serve as a greater heat sink, but it too would melt and then evaporate. Not to mention the lasers could be used for something close to their intended purpose, to launch some warships to the ice base to scoop up any escapees or survivors.

And that's at the outer edge of the Solar System. Closer in it's really not even a contest.

ADDED: I think I'm derailing here with what started as a throwaway half-gag, should I start a separate thread to talk about this topic?

Ara Pacis
2012-Sep-21, 07:48 PM
How much nuclear material would it take to do that?How powerful are the lasers and how much energy from the lasers gets converted into energy for the next laser?


A zone plate for optical lasers would basically be a massive Fresnel lens, collecting and collimating the beams from all the laser banks. It would have to be in the outer Solar system to keep it aimed at the lightship in a very slow orbit--and even then it would need frequent maneuvering. And it would have to be expanded as the ship gets more distant.Not exactly, but similar


But those banked lasers would still pack a wallop even at distant range.Or will they be affected by the thinned array curse?


Let me give an example. Suppose our intrepid rebels are burrowed deep inside a sturdy asteroid. The whole laser system is designed to run for decades at a time. It can simply focus a fraction of its power onto the rock, slowly heating it until it's cherry-red and unsuited to human habitation. They don't need to be any more precise or focussed than they have to be to hit the Fresnel lens. An icy KBO would serve as a greater heat sink, but it too would melt and then evaporate. Not to mention the lasers could be used for something close to their intended purpose, to launch some warships to the ice base to scoop up any escapees or survivors.

And that's at the outer edge of the Solar System. Closer in it's really not even a contest.

ADDED: I think I'm derailing here with what started as a throwaway half-gag, should I start a separate thread to talk about this topic?

Assuming that the lasers can be focussed. Assuming that the lasers put out enough energy dense enough to affects asteroids or KBOs.

Noclevername
2012-Sep-21, 08:09 PM
How powerful are the lasers and how much energy from the lasers gets converted into energy for the next laser?

From Project Rho (http://www.projectrho.com/public_html/rocket/index.php):
Free-electron lasers have a theoretical maximum efficiency of 65%, while others are lucky to get a third of that. This means if your beam power is 5,000 megawatts (five gigawatts), and your cannon has an efficiency of 20%, the cannon is producing 25,000 megawatts, of which 5,000 is laser beam and 20,000 is waste heat! Ken Burnside describes weapon lasers as blast furnaces that produce coherent light as a byproduct. Rick Robinson describes them as an observatory telescope with a jet engine at the eyepiece. Laser cannons are going to need seriously huge heat radiators.

So you'd lose energy fast.


Or will they be affected by the thinned array curse?

Assuming that the lasers can be focussed. Assuming that the lasers put out enough energy dense enough to affects asteroids or KBOs.

If they can't be focussed they'd never hit the fresnel lens or the starship and you'd have no drive.

IIRC, the amount they put out would have to be the equivalent of Earth's yearly energy production budget per day, or some other equally massive amount.

Ara Pacis
2012-Sep-22, 12:01 AM
From Project Rho (http://www.projectrho.com/public_html/rocket/index.php):

So you'd lose energy fast.

IIRC, the amount they put out would have to be the equivalent of Earth's yearly energy production budget per day, or some other equally massive amount.

Was there a point in there?


If they can't be focussed they'd never hit the fresnel lens or the starship and you'd have no drive.

How big is the aperture and how dense is the energy at the aperture? Will lens materials be able to refract it without suffering meltdowns?

Noclevername
2012-Sep-22, 12:11 AM
Was there a point in there?

Yes, the point was answering the question that you asked. Lasers pushing lasers pushing lasers is a red queen's race-- batter to just build bigger lasers. And that the amount of nuclear materials required would probably rival if not exceed that needed for a direct nuclear thruster drive.


How big is the aperture and how dense is the energy at the aperture? Will lens materials be able to refract it without suffering meltdowns?

No way to know unless someone builds it.

Ara Pacis
2012-Sep-22, 06:25 AM
Yes, the point was answering the question that you asked. Lasers pushing lasers pushing lasers is a red queen's race-- batter to just build bigger lasers. And that the amount of nuclear materials required would probably rival if not exceed that needed for a direct nuclear thruster drive.

Then just preposition them along the trajectory of the interstellar vehicle.


No way to know unless someone builds it.

I take that to mean you agree with me. If you don't know, then you also don't know if it would work for the other uses.

Noclevername
2012-Sep-22, 07:24 AM
Then just preposition them along the trajectory of the interstellar vehicle.

That will still take the same amount of energy as sending the vehicle, unless you plan to make it a thousand year preparation phase instead of a thousand year journey.


I take that to mean you agree with me. If you don't know, then you also don't know if it would work for the other uses.

Wrong. The physical parameters for the lasers to be used as a stardrive require that the lasers be both extremely accurate and extremely powerful. If they are not, they can't be used in the way intended.


EDIT: This is now a full-scale derail, so I'll start a thread here (link) (http://cosmoquest.org/forum/showthread.php/138306-Weaponized-laser-launchers) for continuation of this topic.

Noclevername
2012-Sep-22, 08:04 AM
Continuing a discussion from the Will children born in 2012 see the first starship? (http://cosmoquest.org/forum/showthread.php/137581-Will-children-born-in-2012-likely-see-the-first-starship) thread, I'm moving a side conversation here about the possibility of using interstellar launching lasers as weapons within the Solar Sytem.

galacsi
2012-Sep-22, 08:42 AM
Continuing a discussion from the Will children born in 2012 see the first starship? (http://cosmoquest.org/forum/showthread.php/137581-Will-children-born-in-2012-likely-see-the-first-starship) thread, I'm moving a side conversation here about the possibility of using interstellar launching lasers as weapons within the Solar Sytem.


Who do you want to zap ?

Noclevername
2012-Sep-22, 08:54 AM
Who do you want to zap ?

Me personally? I have a list of targets... :)

Swift
2012-Sep-22, 04:48 PM
Continuing a discussion from the Will children born in 2012 see the first starship? (http://cosmoquest.org/forum/showthread.php/137581-Will-children-born-in-2012-likely-see-the-first-starship) thread, I'm moving a side conversation here about the possibility of using interstellar launching lasers as weapons within the Solar Sytem.
Relevant posts have been moved from that thread

publiusr
2012-Sep-22, 06:34 PM
In terms of beamed energy propulsion, might a maser work better? From the Wiki
"In 2012, a research team from the National Physical Laboratory and Imperial College London found a way to make a solid-state maser operate at room temperatures by using pentacene-doped p-Terphenyl as the amplifier medium. This development could possibly lead to a renewal of the maser technology into a wide range of applications, including communications and space exploration."

http://spacewatchtower.blogspot.com/2012/08/laser-cousin-maser-to-become-more-useful.html
http://thesis.library.caltech.edu/2405/

I then noticed this about magnetic fields
http://arxiv.org/abs/1207.7030

There has been a lot of talk about warp drive, but the only field effect type of propulsion that is do-able in the near future might involve the concepts above.

A real plus might be to find a magnetar orbiting a black hole with one pole tidally locked pointing at the BH. Thus both gravity and electromagnetism would snare the spacecraft. As the magnetar passes behind the BH and field lines weakened, the electromagnet is reversed, and the spacecraft not only does a slingshot, but a repulsion effect on the astonomical bodies can be had too. The magnetar is actually more dangerous farther out--Scylla to the BH Charbdis.

OT, if something emerges from a wormhole travelling at Nearly As Fast as Light speeds (NAFAL) the object only emerges with its own velocity, or the wormholes?

Noclevername
2012-Sep-22, 07:10 PM
Relevant posts have been moved from that thread

A thousand thanks, Swift!

Noclevername
2012-Sep-22, 07:17 PM
In terms of beamed energy propulsion, might a maser work better? From the Wiki
"In 2012, a research team from the National Physical Laboratory and Imperial College London found a way to make a solid-state maser operate at room temperatures by using pentacene-doped p-Terphenyl as the amplifier medium. This development could possibly lead to a renewal of the maser technology into a wide range of applications, including communications and space exploration."

http://spacewatchtower.blogspot.com/2012/08/laser-cousin-maser-to-become-more-useful.html
http://thesis.library.caltech.edu/2405/

I then noticed this about magnetic fields
http://arxiv.org/abs/1207.7030

There has been a lot of talk about warp drive, but the only field effect type of propulsion that is do-able in the near future might involve the concepts above.

A real plus might be to find a magnetar orbiting a black hole with one pole tidally locked pointing at the BH. Thus both gravity and electromagnetism would snare the spacecraft. As the magnetar passes behind the BH and field lines weakened, the electromagnet is reversed, and the spacecraft not only does a slingshot, but a repulsion effect on the astonomical bodies can be had too. The magnetar is actually more dangerous farther out--Scylla to the BH Charbdis.

OT, if something emerges from a wormhole travelling at Nearly As Fast as Light speeds (NAFAL) the object only emerges with its own velocity, or the wormholes?

Woah, let's not derail the derail already! ;) This one's only about lasers as weapons. Why not ask this stuff back in the main starship thread (http://cosmoquest.org/forum/showthread.php/137581-Will-children-born-in-2012-likely-see-the-first-starship)?

publiusr
2012-Sep-22, 07:50 PM
I can see a dual use certainly. Especially with this maser breakthrough.

Noclevername
2012-Sep-22, 07:58 PM
I can see a dual use certainly. Especially with this maser breakthrough.

It's a possibility. Room temperature functionality may mean it produces less waste heat than other chemical lasers, an important consideration for a long-use beam.

publiusr
2012-Sep-22, 08:16 PM
There was even a Delta press booklet called "poor mans ray gun" about how to turn a microwave into a weapon. Great... just great http://www.amazon.com/Poor-Mans-Ray-David-Gunn/dp/0879471557

cjameshuff
2012-Sep-23, 07:33 PM
In terms of beamed energy propulsion, might a maser work better? From the Wiki
"In 2012, a research team from the National Physical Laboratory and Imperial College London found a way to make a solid-state maser operate at room temperatures by using pentacene-doped p-Terphenyl as the amplifier medium. This development could possibly lead to a renewal of the maser technology into a wide range of applications, including communications and space exploration."

The main application for these things is as an amplifier for extremely faint signals, not for producing high power signals. We have more direct approaches to producing high-power coherent microwave radiation...klystrons (which are closely related to free electron lasers), magnetrons, etc.

And the required transmitter aperture is proportional to the wavelength. Microwaves are in the cm range, visible light in the sub-micron range. A 30 GHz transmitter would require a 1 km diameter reflector to match a 500 nm transmitter with a 5 cm reflector. Microwave beams might of use for short ranges, but lasers seem superior for long range uses...they aren't nearly inefficient enough to counter the 4-5 orders of magnitude difference in wavelength.