How would you even focus a laser over such a distance?
[QUOTE=Morgen;50121288]If you read the op, they plan to get around the acceleration problem by shooting it with a 100 Gigawatt laser..[/QUOTE]
Aren't they going to need about 82.5 bolts of lightning to generate that kind of power? :v:
If these guys are serious about getting our asses in the stars, they'll find a way to make that shit work. We did it with the moon, we just need to take some money out of the military and dump it on NASA so we can start advancing the species.
[editline]12th April 2016[/editline]
[QUOTE=Morgen;50122294]How would you even focus a laser over such a distance?[/QUOTE]
It's probably a solid five whiteboards of math for these guys
[QUOTE=BigJoeyLemons;50122302]Aren't they going to need about 82.5 bolts of lightning to generate that kind of power? :v:
If these guys are serious about getting our asses in the stars, they'll find a way to make that shit work. We did it with the moon, we just need to take some money out of the military and dump it on NASA so we can start advancing the species.[/QUOTE]
The largest nuclear power plants we have put out about 1 GW per reactor, so it would take about 100 nuclear reactors to power that one laser. It's... quite a lot of power.
[QUOTE=Headhumpy;50122360]The largest nuclear power plants we have put out about 1 GW per reactor, so it would take about 100 nuclear reactors to power that one laser. It's... quite a lot of power.[/QUOTE]
It would take the 10 (~102,830 MW) biggest power plants in the world to produce 100GW.
[url]https://en.wikipedia.org/wiki/List_of_largest_power_stations_in_the_world[/url]
Thats a lot of power.
[QUOTE=LoneWolf_Recon;50122093]I'm fairly certain they're not serious on the technical side considering neither one of them have any aerospace engineering experience.
Funnily enough, perhaps with a larger light sail, it could have a dual purpose of propulsion from an earthbound laser and as the reflector for a parabolic antenna.[/QUOTE]
It's not about surface area, the satellite they Invision will be using so little power that it would make voyager seem like a bullhorn in comparison
I'm just wondering how much this'll cost... In any event, if this "Sci-fi" notion happens, it'll be revolutionary.
[QUOTE=_Axel;50122276]I assume the sail wouldn't be deployed before it reaches orbit. And given that we can communicate to the other end of the solar system using radio waves, I don't think the falloff from the atmosphere would matter much for a 100 GW laser. I suppose the main problem would be diffraction.[/QUOTE]
Dude it has to be built in orbit, far away from earth no less so it can almost continuously beam power. This whole thing doesn't work if can't do that, then the other issue is the craft is unguided so it's not going to be able to flip around and use the sail as a parachute on its way into alpha centari, and on top of that I'm pretty sure the solar wind there won't slow it down from .2 C when it's acting like a parachute.
I'm honestly surprised he would throw his weight behind such a hairbrained scheme when theres better projects to highlight, like the one bill Nye is working on to fly a cubesat with a solar sail
I mean he could even just advocate for another keppler telescope to be built, because that thing is rewriting textbooks and it's 1 more malfunction away from being useless
So this will require sonething like fusion power?
If it's earth based it might not be that big of a deal? Have a rather large battery bank (or capacitors if it needs to deplete that quickly) and build up charge overtime. Of course that would probably still take awhile to charge. Talking several years worth of the current lithium battery output of the entire world, even with the gigafactor to build something like that though.
[QUOTE=Sableye;50122504]It's not about surface area, the satellite they Invision will be using so little power that it would make voyager seem like a bullhorn in comparison[/QUOTE]
This is true, even with high antenna gain (I thought of some reflector the size of Arecibo, which has a antenna gain/directivity of 70dBi) you can only get so much out of a tiny transmitter that small with maybe a milliwatt (-30dB) of power compared to Voyager 1 (22W/13.4dB radio + 48dbi parabolic dish).
The noise floor in the inner solar system, especially within the radius of the Moon's orbit is higher than the rest of space, thus further making it harder to receive.
[QUOTE=Morgen;50122294]How would you even focus a laser over such a distance?[/QUOTE]
The math isnt that hard if you know the orbit of the target, your position, and have precise enough optics and the capability to very precisely point the laser, which are tasks we already do with things like telescopes. Its sort of like a telescope in reverse.
You can exploit windows in the absorption spectrum of the atmosphere to minimize the losses from going through it, however this can depend on the atmospheric conditions and so it would probably need some kind of adaptive optics setup. I think a large ground-based laser like this could be feasible, it would just be really really expensive. It would probably also make some countries uncomfortable because it would be easy to use it in an anti-satellite capacity.
[QUOTE=Morgen;50122636]If it's earth based it might not be that big of a deal? Have a rather large battery bank (or capacitors if it needs to deplete that quickly) and build up charge overtime. Of course that would probably still take awhile to charge. Talking several years worth of the current lithium battery output of the entire world, even with the gigafactor to build something like that though.[/QUOTE]
How would batteries or capacitors help here? You need sustained power output over the course of many years to keep the sail accelerating. Batteries do nothing to help that.
[editline]13th April 2016[/editline]
[QUOTE=mecaguy03;50122720]The math isnt that hard if you know the orbit of the target, your position, and have precise enough optics and the capability to very precisely point the laser, which are tasks we already do with things like telescopes. Its sort of like a telescope in reverse.
You can exploit windows in the absorption spectrum of the atmosphere to minimize the losses from going through it, however this can depend on the atmospheric conditions and so it would probably need some kind of adaptive optics setup. I think a large ground-based laser like this could be feasible, it would just be really really expensive. It would probably also make some countries uncomfortable because it would be easy to use it in an anti-satellite capacity.[/QUOTE]
Depending on how wide the beam is, at a power of 100 GW, you may start running into problems like laser-induced breakdown of air.
[editline]13th April 2016[/editline]
[QUOTE=LoneWolf_Recon;50122700]This is true, even with high antenna gain (I thought of some reflector the size of Arecibo, which has a antenna gain/directivity of 70dBi) you can only get so much out of a tiny transmitter that small with maybe a milliwatt (-30dB) of power compared to Voyager 1 (22W/13.4dB radio + 48dbi parabolic dish).
The noise floor in the inner solar system, especially within the radius of the Moon's orbit is higher than the rest of space, thus further making it harder to receive.[/QUOTE]
It's likely that communication over such immense distances will be carried out using lasers that don't suffer from the inverse-square law.
You might be able to avoid that by using an array of lasers or something like that
might be the best way because smaller installations would be easier to build
[QUOTE=Ruski v2.0;50120349]We future now
Driverless cars, forays into space exploration, disease cures and the continuing miniaturization of technology? Fucking awesome last few years.[/QUOTE]
Don't forget that we also now have cyborgs, limbed, walking mechas designed for military use, medical procedures using just lasers, trains that float through the air without touching the ground using the power of electricity, fairly accurate word-based voice recognition by computers, video phones and laser weapons, as well as having cloaking technology and adaptive AI in their first steps toward utilization.
[QUOTE=Headhumpy;50122781]
It's likely that communication over such immense distances will be carried out using lasers that don't suffer from the inverse-square law.[/QUOTE]
Much less likely to be victim to inverse-square yes, but still very much vulnerable. The bonus could be more that visible light or certain forms of short-wave IR will have an even lower noise floor than standard radio out in space, thus making detection of weaker visible light/IR signals easier than normal radio.
I'm not entirely convinced blasting a micro-satellite with a 100 GW laser is the path to the stars we should take.
As fascinating as it sounds, it seems like a massive energy investment.
[QUOTE=LoneWolf_Recon;50122888]Much less likely to be victim to inverse-square yes, but still very much vulnerable. The bonus could be more that visible light or certain forms of short-wave IR will have an even lower noise floor than standard radio out in space, thus making detection of weaker visible light/IR signals easier than normal radio.[/QUOTE]
Still the issue of power again defeats it, the satellite they're talking is 100 grams or less, which means it's most likely going to run out of lower pretty quickly, and even if lower wasn't a problem, the size limits again make it pointless.
To call this a satellite is a bit of a joke, what it is is launching a potato chip to .2 c using a big space based laser array
If we are putting the resources in to make a 100 GW laser array, we might as well use it for more constructive purposes like sending larger craft around our own solar system. If they didn't need to use chemical propulsion systems or even onboard power systems we could realistically send larger spacecraft directly to where they need to go instead of having to use complex gravity assists
[QUOTE=Headhumpy;50122781]How would batteries or capacitors help here? You need sustained power output over the course of many years to keep the sail accelerating. Batteries do nothing to help that.
[editline]13th April 2016[/editline]
Depending on how wide the beam is, at a power of 100 GW, you may start running into problems like laser-induced breakdown of air.
[editline]13th April 2016[/editline]
It's likely that communication over such immense distances will be carried out using lasers that don't suffer from the inverse-square law.[/QUOTE]
I was under the impression that the laser would be firing at the sail for a relatively short period of time.
[QUOTE=Matthew0505;50122986]Wouldn't the laser just vaporize the sail, even at 99.9999% reflectivity that's 100kW of energy being absorbed.[/QUOTE]
Depends on what material you use.
I saw something about using sapphires.
Also depends how long the laser is firing for.
[QUOTE=Morgen;50122252]The sail. It's only a few atoms thick. I imagine the transmission losses of shooting at something probably in GEO would be too significant as well.[/QUOTE]
Wouldn't micrometeorites ruin this thing really fast
[QUOTE=Kylel999;50123838]Wouldn't micrometeorites ruin this thing really fast[/QUOTE]
Some sort of magnetic shield on the front... or some kind of really thick multilayer/composite armour.
You are unlikely to hit anything large so you only really need to plan for tiny bits of dust etc
20% of light speed is relativistic? I thought it's like, 95%
[QUOTE=The Duke;50122857]Don't forget that we also now have cyborgs, limbed, walking mechas designed for military use, medical procedures using just lasers, trains that float through the air without touching the ground using the power of electricity, fairly accurate word-based voice recognition by computers, video phones and laser weapons, as well as having cloaking technology and adaptive AI in their first steps toward utilization.[/QUOTE]
I just remembered when i was a Kid i always thought voice recognition would never take off because it was always so shit. Funny thinking back on it now.
[editline]13th April 2016[/editline]
[QUOTE=damnatus;50123858]20% of light speed is relativistic? I thought it's like, 95%[/QUOTE]
From Wikipeida;
[QUOTE=Wikipedia]The boundary for when a particle becomes relativistic is impossible to define, but a particle can generally be said to be relativistic when Newtonian mechanics no longer provide an accurate description which, within a margin of error of 1%, is 10% of the speed of light for the speeds of the associated masses under consideration.[/QUOTE]
[QUOTE=Morgen;50122294]How would you even focus a laser over such a distance?[/QUOTE]
No need to focus too much, the sail is pretty big so a little bit of dispersion isn't a big deal and is even necessary.
[QUOTE=Sableye;50122521]Dude it has to be built in orbit, far away from earth no less so it can almost continuously beam power.[/QUOTE]
Or you can position several on the surface of the earth so that there's always one pointed at it.
[QUOTE=Kylel999;50123838]Wouldn't micrometeorites ruin this thing really fast[/QUOTE]
Space is really big and mostly empty.
Really, what are the chances?
[editline]13th April 2016[/editline]
Wait, I get how were getting there but how are we supposed to stop? Wont it just fly by so fast we won't get any useful data?
So at 20% of the speed of light, how big of an issue is time dilation going to be?
[QUOTE=Zestence;50123984]So at 20% of the speed of light, how big of an issue is time dilation going to be?[/QUOTE]
I think it only starts to be an issue when you approach c at like 0.9 and upwards since you can never reach c. I think the difference is about 1 day otherwise, besides that i don't think it would matter to much anyway since it isn't manned.
[QUOTE=_Axel;50122208]The laser beam will get torn to shreds? I don't think we're talking about the same thing here.[/QUOTE]
Yes the laser beam would literally be torn to shreds, or diffused, as it travels through the imperfectly refractive atmosphere.
[editline]13th April 2016[/editline]
[QUOTE=mdeceiver79;50123624]Depends on what material you use.
I saw something about using sapphires.[/QUOTE]
How would sapphires help, exactly?
[editline]13th April 2016[/editline]
[QUOTE=Kylel999;50123838]Wouldn't micrometeorites ruin this thing really fast[/QUOTE]
You could just send lots of them, and hope that most survive.
[QUOTE=paul simon;50124036]Yes the laser beam would literally be torn to shreds, or diffused, as it travels through the imperfectly refractive atmosphere.[/QUOTE]
The astronomers who pointed lasers at a mirror on the moon didn't seem to have problems with that. I think you overestimate the diffusing effect of the atmosphere.
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