Diff for "LaserCutBallast"

= 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 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 { { T_v \kappa } \over { Abs w_F arctan left( { 8 \kappa t_L } \over { w_f^2 } right)^2 $

||                  || Aluminum      || 
|| $ I_v $          ||               || Threshold Intensity                                     ||
|| $ T_v $          || 3000K         || Vaporization Temperature                                ||
|| $ w_f $          || 10μm       || spot radius                                             ||
|| $ Abs $          || 0.14          || Absorptioncoefficient                                   ||
|| $ \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 1&um;s pulse, a 10&um;m kerf, and a 10 watt pulse (10MW/cm^2^), 















||(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}}]]||