![Worm-Hole-600375[1].jpg](https://i.imgur.com/nBVaJJp.jpg "Worm-Hole-600375[1].jpg")
How long would a manmade object like a solar sail would take to reach near lightspeed levels ? Is it possible to send a probe and back to the nearest star within our lifetime ?
I'm pretty sure some form of gold is the key to space travel
look at ormus
>>8013676
> The Kingdom of Ormus was a 10th to 17th century kingdom located within the Persian Gulf and extending as far as the Strait of Hormuz.
>>8013694
white gold powder
>>8013670
University of California Santa Barbera proposed a 1 gram ship getting to alpha centuri in less than 20 years, just in terms of velocity.
Practicality of this? Low. This requires huge sails (in regards to ship size), these sails have to be super thin, and be able to withstand the interstellar medium.
In our life time is doubtful, but I'd give better certainty to another century or two, being hopeful for some fatbrain coming along to make some serious improvements. Barring this happening in our lifetime, of course.
Starshot plans to do it in twenty years.
http://breakthroughinitiatives.org/Initiative/3
>>8014053
>Starshot plans to do it in twenty years.
They plan on launching within 20 years, assuming the required technology can be developed that quickly.
See "Project Orion", "Project Daedalus", "Project Longshot", etc.
We've been "right around the corner" from interstellar probes for decades now.
And I'm not sure I'd call 0.2C "near lightspeed", tau is 0.98, so relativistic effects are minor.
>>8013670
>Is it possible to send a probe and back
>and back
No, solar sails are about useless without high powered lasers pushing against them.
why are they called 'solar sails?
>>8014106
because they use the aether flow of space to propel their sails, much like wind
>>8014119
> aether flow of space
:^)
>>8014106
Because they act like sails. Instead of wind you have radiation pressure from the sun.
>>8013670
>Is it possible to send a probe and back to the nearest star within our lifetime ?
no
>How long would a manmade object like a solar sail would take to reach near lightspeed levels ?
Can't happen.
>>8014099
>0.2C
We couldn't even reach 20% of C (134,123,325mph). We would even begin to make enough power to do so.
>>8014126
https://en.wikipedia.org/wiki/Solar_wind
>>8014146
yeah. says nothing about aether...
>>8014149
Aether is an old term for everything beyond the Earth's atmosphere, meaning the solar winds.
>>8014155
>Aether is an old term for everything beyond the Earth's atmosphere, meaning the solar winds.
Not only is that wrong, but solar sails don't use solar wind either. They use radiation pressure.
>>8014160
Aether is an antiquated umbrella term for everything between the stars including solar wind and has had more than one definition. Solar wind is radiation pressure.
>>8014160
> radiation pressure
like thats a real thing
>>8014163
>Aether is an antiquated umbrella term for everything between the stars including solar wind and has had more than one definition.
No.
>Solar wind is radiation pressure.
Also no.
>>8014201
https://en.wikipedia.org/wiki/Solar_wind
https://en.wikipedia.org/wiki/Aether_%28classical_element%29
https://en.wikipedia.org/wiki/Radiation_pressure
kys
>>8014106
In an analogous way that wind pushes a sail, light can to. Momentum is always conserved, so where do you think a photons momentum goes when it hits something?
>>8014252
photons don't have mass idiot they have no momentum
>>8014241
>links three articles which prove himself wrong
Such a failure at everything you are.
>>8014261
>photons don't have mass idiot they have no momentum
>photons don't have REST mass, sorry to have bothered you
FTFY
>>8014146
>We couldn't even reach 20% of C (134,123,325mph). We would even begin to make enough power to do so.
The Starshot guys are saying it will require a 100GW laser which can be sustained for several minutes
>>8014261
p=hf/c
>>8014146
>We couldn't even reach 20% of C (134,123,325mph). We would even begin to make enough power to do so.
http://arxiv.org/abs/1604.01356
Why not?
>implying space vacuum is empty
>implying any manmade vehicle wouldn't be shattered by colliding with microdust at near C velocities
It would take a very long time, and i doubt it would ever come back, but if we did it right, it would probably only take 40 or 50 years.
how many times would you need to cum to produce the propulsion necessary to reach 1% the speed of light?
>>8014261
>please be trolling
m=p/c
λ=h/p
>>8014295
>implying popsci would ever dare mention this
>>8014313
idk but I can reach Uranus in no time, famm.
>>8013670
TL;DR: If the sail relies on the sun's light for thrust, then it would accelerate extremely slowly and would be useless for interstellar travel unless you're willing to wait millions of years. If instead you aim a high-powered laser at the sail, then in principle you could accelerate a solar sail to relativistic speeds in a reasonable amount of time, but it would be incredibly expensive, technologically challenging and would consume enormous amounts of power. In my opinion, such a laser sail is not going to be achievable any time soon. Perhaps in a few hundred years.
There are a few reasons why light is a very poor way to apply thrust to a spacecraft. For starters, photons (light particles) carry a lot of energy but hardly any momentum. In order to accelerate a spacecraft, you want to give it lots of momentum. This means that you waste an incredibly large amount of energy producing a laser beam to shine on your sail, but it hardly pushes the sail at all. You would need terawatts or petawatts of laser power to produce any usable thrust at all for even a small spacecraft. It is extremely inefficient.
The second problem is that laser beams (or any light beams for that matter) tend to spread out with distance. For an effective laser sail, you want to be able to focus all of the laser light onto the sail for the entire acceleration phase. However, there is something called the diffraction limit. It is impossible to create a beam of light that is 100% parallel and straight. All light beams will spread out as a cone, with some divergence angle. This angle depends on the wavelength of light (shorter wavelengths will spread out less) and the diameter of your laser aperture (the wider your laser cannon, the less the beam will spread out). For example, say you have a solar sail that's 1 m in diameter. If you have a laser emitter that's 1 m wide, using a wavelength of 500 nm (green light), the divergence angle is about 9x10-6 degrees.
>>8014356
That may not sound like much, but eventually the beam will spread out so much as to become unusable. At a distance of 1,000 km, the beam has spread out to 1.16 m in diameter. Not too bad. Now, after 1 million km, it has spread out to 159 m. Remember that your sail is only 1 m in diameter. So now over 99.99% of the beam is being wasted. At a distance of 150 million km (about the distance from the Earth to the sun), the beam has spread out to about 24 km in diameter. So it's now completely unusable.
To get around this second limitation, you need either a really wide sail and/or a really wide laser emitter. Both of which are expensive and difficult to build.
>>8014365
And as for the first problem (that light carries a lot of energy but not much momentum), this means that you have to have a *very* intense laser beam constantly shining on your laser sail to get any usable thrust. You'd need something crazy like gigawatts or terawatts of power per square m of sail area. Now, we're assuming that the sail is reflective like a mirror (maybe it's coated in a layer of aluminum or gold). But mirror's aren't 100% reflective. Aluminum for instance is only about 92% reflective in the visible spectrum. That means it's absorbing 8% of incoming light. And all of that absorbed light turns into heat. 8% of a gigawatt or a terawatt is. . . a LOT of heat. So an aluminum sail would basically instantly vaporize.
>>8014372
We can do better than aluminum, though. It is possible to make dielectric mirrors using special coatings which are over 99.9% reflective, but only for a specific wavelength of light. So, in principle we could make a laser sail that's reflective enough to not instantly vapourize the moment we turn on the laser. But there are two difficulties here. One, these dielectric mirrors are only 99.9% reflective when they are perfectly clean. There is a decent amount of dust floating around in space. As this dust lands on your sail it will gradually make it less reflective and will cause the sail to absorb more laser energy, thus heating up and becoming damaged.
The second problem is that as you accelerate your sail to relativistic velocities, now the laser light becomes redshifted (i.e. from the sail's perspective, the light is now a longer wavelength). Since your dielectric mirror is optimized for a specific wavelength, it will no longer be 99.9% reflective at this new, redshifted wavelength. You could maybe make a tunable laser which can gradually change its output wavelength, but this is very difficult and inefficient.
