The spaceship from Avatar would do exactly this when travelling to Pandora.
[thumb]http://vignette4.wikia.nocookie.net/jamescameronsavatar/images/1/1f/Isv.jpg/revision/latest?cb=20100127043619[/thumb]
A massive array of lasers stationed around earth, which hit a big reflector (not present in image), accelerate the craft to 70% the speed of light.
Problem is that it would require ~10 000 times more power than the the power usage of the entire planet.
You can read more about it here (Avatar ISV Venture Star):
[url]http://www.projectrho.com/public_html/rocket/slowerlight.php#id--Go_Fast--Starships[/url]
efficient travel in space has got to be possible. I feel as if every concept for the next big space thing is 8/10 already possible, 2/10 minor footnote thermodynamic laws that make the concept not work.
video brought up my concern-
if we need a laser array on earth to propel it, how the hell does it slow down
[QUOTE=ScottyWired;49897777]video brought up my concern-
if we need a laser array on earth to propel it, how the hell does it slow down[/QUOTE]
Eventually build one on each planet.
[QUOTE=Silikone;49897892]Eventually build one on each planet.[/QUOTE]
So in the future inter-planetary travel is going to be like a game of pong between a pair of huge lasers?
[QUOTE=Morbo!!!;49897940]So in the future inter-planetary travel is going to be like a game of pong between a pair of huge lasers?[/QUOTE]
More like "we got a cruise liner incoming, let's blast it with lasers so they can land safely and our planet doesn't get hit by a kilometre-long piece of metal at ¼c "
Woah cool I actually know one of the students working with this research group
[QUOTE=Blind Lulu;49898321]But how do you build one on the other planet if you have to get their in the first place?[/QUOTE]
I would assume using Slingshot maneuvers around the destination sun or around certain planets could be used to slow down the craft enough until it hits an orbit velocity around target planet, upon which normal engines could be used for further deceleration. That's just a guess though.
[QUOTE=Feuver;49899450]I would assume using Slingshot maneuvers around the destination sun or around certain planets could be used to slow down the craft enough until it hits an orbit velocity around target planet, upon which normal engines could be used for further deceleration. That's just a guess though.[/QUOTE]
not at those speeds
deceleration from anything close to relativistic takes a ton of energy so for this setup to be used you'd have to travel to the planet the hard way first (slowly)
I suppose you could brake with other methods, but you spend only half the fuel because you don't need to worry about the speeding up part.
Lithobrake.
woah imagine we made it really small but just a strong we could space pirates
[url]http://i.imgur.com/oTaglUg.png[/url]
There's some missing information, but if the laser array in total is outputting a max of 70GW (assuming 70GW is the actual light power) focused onto a 1 sq meter area on the space craft's sail (and the spacecraft + sail = 200kg) would only result in ~2.33mm/s^2 of acceleration. (See radiation pressure)
It would take this laser array over 22 thousand years to accelerate the craft to 0.015c. Its bullshit in its current form that the video is presenting it.
[QUOTE=LoneWolf_Recon;49900007]There's some missing information, but if the laser array in total is outputting a max of 70GW (assuming 70GW is the actual light power) focused onto a 1 sq meter area on the space craft's sail (and the spacecraft + sail = 200kg) would only result in ~2.33mm/s^2 of acceleration. (See radiation pressure)
It would take this laser array over 22 thousand years to accelerate the craft to 0.015c. Its bullshit in its current form that the video is presenting it.[/QUOTE]
yea you'd need ~10K terawatts or something for reasonable acceleration
Which of course is absolutely bonkers.
What a load of populist bullcrap.
[QUOTE=NeverGoWest;49900082]What a load of populist bullcrap.[/QUOTE]
Aren't they just explaining a theoretical concept in layman's terms? What's wrong with that? It's kind of SciShow's whole shtick.
[QUOTE=paul simon;49897672]The spaceship from Avatar would do exactly this when travelling to Pandora.
[thumb]http://vignette4.wikia.nocookie.net/jamescameronsavatar/images/1/1f/Isv.jpg/revision/latest?cb=20100127043619[/thumb]
A massive array of lasers stationed around earth, which hit a big reflector (not present in image), accelerate the craft to 70% the speed of light.
Problem is that it would require ~10 000 times more power than the the power usage of the entire planet.
You can read more about it here (Avatar ISV Venture Star):
[url]http://www.projectrho.com/public_html/rocket/slowerlight.php#id--Go_Fast--Starships[/url][/QUOTE]
I love this ISV. I was reading about it on the avatar wiki and it's all very well thought out. Unfortunately we haven't quite got the technology for it yet.
[QUOTE=Adamhully;49901353]I love this ISV. I was reading about it on the avatar wiki and it's all very well thought out. Unfortunately we haven't quite got the technology for it yet.[/QUOTE]
A lot of the tech that was waved around in our faces for 3 seconds in the movie, was a lot more interesting than the movie.
[QUOTE=StrawberryClock;49901314]Aren't they just explaining a theoretical concept in layman's terms? What's wrong with that? It's kind of SciShow's whole shtick.[/QUOTE]
What's wrong with it is that the math is completely off, they proport that a 200kg craft with this laser array could be propelled to mars within a month. (See previous post above)
They explain the concept decently, but I suppose I'm just being picky.
[QUOTE=LoneWolf_Recon;49901603]What's wrong with it is that the math is completely off, they proport that a 200kg craft with this laser array could be propelled to mars within a month.
They explain the concept decently, but I suppose I'm just being picky.[/QUOTE]
Usually SciShow is pretty open about receiving criticism for inaccurate information in their videos. I don't know what's the best way to contact them about it but if you want to tell them about a flaw I'm guessing their [URL="https://twitter.com/scishow"]twitter[/URL] would be a good start.
Perhaps they should have done some more in-depth research, but one of the sources (all their sources are always listed in the video description) for their claim about getting a probe to mars in 3 days is this video: [URL]https://www.youtube.com/watch?v=WCDuAiA6kX0[/URL]
THAT video was developed from THIS live recording: [URL]http://livestream.com/viewnow/niac2015seattle[/URL]
So, I'm guessing you can't fault SciShow too much if that inaccurate information passed through two "scientific-minded" channels without any fuss first, though I guess they could have done their own calculations first but that's a bit unlikely with their current format.
[editline]9th March 2016[/editline]
So basically it's not like they materialized that claim out of thin air.
[QUOTE=LoneWolf_Recon;49900007]There's some missing information, but if the laser array in total is outputting a max of 70GW (assuming 70GW is the actual light power) focused onto a 1 sq meter area on the space craft's sail (and the spacecraft + sail = 200kg) would only result in ~2.33mm/s^2 of acceleration. (See radiation pressure)
It would take this laser array over 22 thousand years to accelerate the craft to 0.015c. Its bullshit in its current form that the video is presenting it.[/QUOTE]
Are you sure? I did the calculation and my number is 3 orders of magnitude greater. Say the sail absorbs all the power from the laser (area is irrelevant if all the beam power is being absorbed) and the sail is perpendicular to the beam. 70GW is 70 billion Joules per second. So the total momentum of the beam is 70 billion / 299,792,458 kg * m/s = ~233 kg * m/s, and dividing by the mass of the craft (which they say is about 100 kg in the video, not sure why you wrote 200 kg) and since this is the change in velocity per second, you get 2.33 m/s^2. That's by absorption, but solar sails are typically reflective and the momentum change is twice as big, so really you'd get 4.66 m/s^2, over half a g.
So, I appreciate the skepticism that FPs display in general but sometimes I feel like some posters just qualify something as BS and call it a day instead of doing the required homework like JohnnyMo1 just did.
Can we just make this on a smaller scale and send some satellites one way out. I think that would be cool enough already and probably in the realm of possibility.
[QUOTE=JohnnyMo1;49901772]Are you sure? I did the calculation and my number is 3 orders of magnitude greater. Say the sail absorbs all the power from the laser (area is irrelevant if all the beam power is being absorbed) and the sail is perpendicular to the beam. 70GW is 70 billion Joules per second. So the total momentum of the beam is 70 billion / 299,792,458 kg * m/s = ~233 kg * m/s, and dividing by the mass of the craft (which they say is about 100 kg in the video, not sure why you wrote 200 kg) and since this is the change in velocity per second, you get 2.33 m/s^2. That's by absorption, but solar sails are typically reflective and the momentum change is twice as big, so really you'd get 4.66 m/s^2, over half a g.[/QUOTE]
I'm using the [URL="https://en.wikipedia.org/wiki/Radiation_pressure#Radiation_pressure_by_reflection_.28using_particle_model:_photons.29"]radiation pressure by reflection function[/URL] which yields more pressure than the absorbed pressure perpendicularly, thus alpha = 0. With Ef = 70GW/m^2, c = 3 x 10^8 m/s.
Pressure felt = 466N/m^2 or 466N on that meter^2 sail.
Assuming the craft and sail add up to 200kg in the video (They added the extra 100kg sail at 3:33), I get an acceleration of 2.3m/s^2 ([U]I goofed on this part, I accidentally put in 200kkg[/U]) Thus taking 22 days to accelerate up to 0.015c.
I partially take back what I said earlier, thanks for the sanity check JohnnyMo!
[QUOTE=LoneWolf_Recon;49901962](They added the extra 100kg sail at 3:33)[/QUOTE]
Ahh, yeah. Missed that. Now our calculations match up!
[QUOTE=Tmaxx;49901377]A lot of the tech that was waved around in our faces for 3 seconds in the movie, was a lot more interesting than the movie.[/QUOTE]
Very late reply but yeah, couldn't agree more.
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