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| Rocket upper stage tanks have a thickness from 1 to 5 mm (Need Reference) and are typically aluminum alloy. Aluminum has an absorption peak of 14% around 900nm (LOOSEN1998). | Rocket upper stage tanks have a thickness from 1 to 5 mm (Need Reference) and are typically aluminum alloy. Aluminum has an absorption peak of 14% around 900nm (LOOSEN1998). If we assume a 1cm^2^ aperture emitter and a 1 meter distance, we can make a 10&um;m spot, ''maybe'', given a magic phase-coherent focusing laser. Loosen's equation 2 offers Treusch's formula for beam-center intensity: $ I_v \propto \Large { { T_v \kappa } \over { Abs ~ w_F ~ arctan \left( { { 8 \kappa t_L } \over { w_f^2 } } \right)^{{1}\over{2}} } } $ || || Aluminum || || $ I_v $ || || Threshold Intensity || || $ T_v $ || 3000K || Vaporization Temperature || || $ w_f $ || 10μm || spot radius || || $ Abs $ || 0.14 || Absorption Coefficient || || $ \kappa $ || 1e-4 m^2^/s || Thermal diffusivity, $ \kappa = \lambda_th / \rho c_h $ || || $ \lambda_th $ || 240 W/m-K || Thermal conductivity || || $ \rho $ || 2700 kg/m^3^ || Density || || $ c_h $ || 900 J / kg-K || Heat capacity || For a 1μs pulse, a 10μm kerf, and a 10 watt pulse (10MW/cm^2^), MORE LATER |
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||(LOOSEN1998) Peter Loosen, ''Lasers in Materials Processing'', figure 6 on page 291 in [[ http://books.google.com/books?id=l3yk_yBPAuIC&pg=PA287&lpg=PA287&dq=Peter+Loosen+Lasers+in+Materials+Processing&source=bl&ots=hZKod4LG13&sig=BBarW-P1rDi8gz4GZxtVIjHnp6o&hl=en&sa=X&ei=0ML1UPiqHuXoiALAxIGwBQ&ved=0CDMQ6AEwAA#v=onepageq=Peter%20Loosen%20Lasers%20in%20Materials%20Processing&f=false | ''Advances in Lasers and Applications'' 1998. ]]||{{attachment:laserAlum.png| |height=200}}|| |
||(LOOSEN1998) Peter Loosen, ''Lasers in Materials Processing'', figure 6 on page 291 in [[ http://books.google.com/books?id=l3yk_yBPAuIC&pg=PA287&lpg=PA287&dq=Peter+Loosen+Lasers+in+Materials+Processing&source=bl&ots=hZKod4LG13&sig=BBarW-P1rDi8gz4GZxtVIjHnp6o&hl=en&sa=X&ei=0ML1UPiqHuXoiALAxIGwBQ&ved=0CDMQ6AEwAA#v=onepageq=Peter%20Loosen%20Lasers%20in%20Materials%20Processing&f=false | ''Advances in Lasers and Applications'' 1998. ]]||[[attachment:laserAlum.png|{{attachment:laserAlum.png| |height=120}}]]|| |
Making Ballast from Rocket Tanks with Lasers
Space debris may be an opportunity, not a problem. Rocket tanks may be cut into gram-sized weights with lasers, then added to ultra-thinsats to stabilize their orbits against light pressure. Perhaps, with some technological advances, we can learn to build solid state lasers that don't need optics, and mount them on thinsats. A 100 milliwatt (average) pulsed laser will not cut metal very fast, but in time it will cut it.
Rocket upper stage tanks have a thickness from 1 to 5 mm (Need Reference) and are typically aluminum alloy. Aluminum has an absorption peak of 14% around 900nm (LOOSEN1998). If we assume a 1cm2 aperture emitter and a 1 meter distance, we can make a 10&um;m spot, maybe, given a magic phase-coherent focusing laser.
Loosen's equation 2 offers Treusch's formula for beam-center intensity:
I_v \propto \Large { { T_v \kappa } \over { Abs ~ w_F ~ arctan \left( { { 8 \kappa t_L } \over { w_f^2 } } \right)^{{1}\over{2}} } }
|
Aluminum |
|
I_v |
|
Threshold Intensity |
T_v |
3000K |
Vaporization Temperature |
w_f |
10μm |
spot radius |
Abs |
0.14 |
Absorption Coefficient |
\kappa |
1e-4 m2/s |
Thermal diffusivity, \kappa = \lambda_th / \rho c_h |
\lambda_th |
240 W/m-K |
Thermal conductivity |
\rho |
2700 kg/m3 |
Density |
c_h |
900 J / kg-K |
Heat capacity |
For a 1μs pulse, a 10μm kerf, and a 10 watt pulse (10MW/cm2),
MORE LATER
(LOOSEN1998) Peter Loosen, Lasers in Materials Processing, figure 6 on page 291 in ''Advances in Lasers and Applications'' 1998. |
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