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4/18/2021 9:59:29 PM
Posted: 10/31/2004 8:12:26 PM EDT
So you shoot a laser from Earth at a target on the moon. The Laser has to get though the Earths atmosphere and still have enough power to melt a 1/4" diameter hole though both sides in a FULL aluminum soda can that is placed on the moon.

How powerfull and what wavelength of a laser do you need? Pulsed lasers are ok.

edited to add: the time of day on the moon is between sunrise and sunset so the temp is about 100 degrees F

edited to add: the whole pulse has to take place in less than 1 second

edited to add: the can wont tip over, its secure
Link Posted: 10/31/2004 8:13:57 PM EDT
PSA: anodizing on aluminum melts at about 1400 degrees
Link Posted: 10/31/2004 8:14:24 PM EDT
Link Posted: 10/31/2004 8:15:23 PM EDT
It isnt wavelength, or necessarily power.

You will get some attenuation from the atmosphere, but the main problem will be focusing the laser to the moon.
Link Posted: 10/31/2004 8:16:17 PM EDT
You would need to know the amount of heat being applied to it from the sun, to get an accurate idea. (if your looking for how much laser is enough to get it to happen)
Link Posted: 10/31/2004 8:17:34 PM EDT
40 KW
Link Posted: 10/31/2004 8:20:32 PM EDT
Diet soda or regular? It makes a HUGE difference.
Link Posted: 10/31/2004 8:21:45 PM EDT

Quoted:
Diet soda or regular? It makes a HUGE difference.



Ok...diet.
Link Posted: 10/31/2004 8:22:02 PM EDT
Even if you could focus a beam tight enough and had enough power it wouldn't focus on a spot small enough to melt the hole from here to there. Earth movements and moon movements would have the beam bouncing all over the place. Then refraction through the atmosphere would degrade the beam.

Railgun....
Link Posted: 10/31/2004 8:22:40 PM EDT
Its impossible. After the first hole the soda will jet out and tip the can over. Next question.
Link Posted: 10/31/2004 8:23:48 PM EDT
Link Posted: 10/31/2004 8:25:51 PM EDT

Quoted:

Quoted:
Diet soda or regular? It makes a HUGE difference.



Ok...diet.

In that case, the answer is ... 42!
Link Posted: 10/31/2004 8:26:38 PM EDT
As with all radiation energy is halved evert time distance is doubled.
Link Posted: 10/31/2004 8:31:10 PM EDT

Quoted:
Its impossible. After the first hole the soda will jet out and tip the can over. Next question.



Ok the can is secure to the ground because one of astronaut Allen Shepards gold balls is resting on top of the can wont fall over.
Link Posted: 10/31/2004 8:41:47 PM EDT
Here you go. Just light it up and melt it.

Link Posted: 10/31/2004 8:43:25 PM EDT
There's a soda can on the moon?  Who did that?
Link Posted: 10/31/2004 8:47:29 PM EDT
1/4 inch hole? Fire up the Deathstar, you ain't getting a beam that small from earth to moon.

CW
Link Posted: 10/31/2004 8:49:25 PM EDT
1.21 jigowatts
Link Posted: 10/31/2004 8:51:52 PM EDT

Quoted:
1/4 inch hole? Fire up the Deathstar, you ain't getting a beam that small from earth to moon.

CW



so whats a reasonable size?
Link Posted: 10/31/2004 9:01:35 PM EDT
Lets assume that you want  a small hole ~ 10mm for convenient unit.  The diffraction limited spot size of a lens is 1.27*L*F# (pick L to be 10.6um "CO2 Laser",  and we solve for f#).    So to focus a laser to a 10mm diameter spot we needs a lens with a focal length of  384403 km and a diameter of ~ 51748 km.  Now energy density we need to get to 1400C  is ~ 3.2KW/cm^2 .  

So power is power you need 3.2 KW/cm^2 to burn.  Plus you need enough power to overcome the atmospheric attenuation.  Then you need a really big lens to focus.  You will also need  an adaptive optics mirror to overcome the atmospheric disturbances.

There is more but this is most of it and it is late.

roptics
Link Posted: 10/31/2004 9:12:51 PM EDT

Quoted:

Quoted:
1/4 inch hole? Fire up the Deathstar, you ain't getting a beam that small from earth to moon.

CW



so whats a reasonable size?


Read roptics post and do the math. I would use a graser instead of a laser, but that's your choice.

CW
Link Posted: 10/31/2004 9:17:02 PM EDT
Tell me how the soda can got on the moon, unopened, first.
Link Posted: 10/31/2004 9:19:13 PM EDT
42
Link Posted: 10/31/2004 9:20:02 PM EDT

Quoted:

Quoted:
Diet soda or regular? It makes a HUGE difference.



Ok...diet.



Coke, Pepsi, or generic?
Link Posted: 10/31/2004 9:25:08 PM EDT

Quoted:
There's a soda can on the moon?  Who did that?



Probably some irresponsible asshole, water skiing on the Sea of Tranquility. Jerks.

Edit: can't spell
Link Posted: 10/31/2004 9:28:38 PM EDT

Quoted:

Quoted:

Quoted:
1/4 inch hole? Fire up the Deathstar, you ain't getting a beam that small from earth to moon.

CW



so whats a reasonable size?


Read roptics post and do the math. I would use a graser instead of a laser, but that's your choice.

CW



Interesting, Gamma Ray Laser or Graser, has been a problem for engineers and scientists  for 30+ years.
Something called LEGS: www.legs.bnl.gov/

Have to read more on this!

Railgun....
Link Posted: 10/31/2004 9:30:56 PM EDT
Just use a .50 cal and be done with it! If it can shoot down 747s and satellites, I'm sure it can punch soda cans on the moon!
Link Posted: 10/31/2004 10:17:08 PM EDT
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