[ExI] libertarian (asteroid) defense

[Anders Sandberg]

Damien Sullivan wrote:
> Actually I imagine volcanoes might pretty tameable.  Drill down and
> release gases/magma in a controlled manner, rather than letting them
> blow all at once.  Though the BP oil spill highlights the safety
> concerns of drilling into a pressure chamber.  Would want to practice on
> the small volcanoes first.
>   

I think there is a bit of a problem with this method. A typical volcano 
has a lava chamber on the order of a cubic kilometer and  contains up 
towards 10^19 Joules or so. A drilled hole has a diameter ~0.1 m. 
Assuming blackbody radiation from 2000 K lava only allows 9000 W to 
escape the hole. Pumping up something like hydrogen (thermal capacity 20 
kJ/kgK) at the speed of sound (~1300 m/s) at a density of 1000 kg/m^3 
gives an energy flux of 520*10^9 W, able to defuse the volcano in a year 
or so... assuming the massive erosion near-supersonic very hot gas would 
have on the pipe does not just turn it into a steam vent leading to the 
volcano boiling off (the risk is alway a sudden pressure decrease in the 
chamber, since then gases start to release in the lava and it spurts out).

Garden variety volcanos are anyway not big threats except to locals and 
airlines. It is defusing supervolcanos we ought to seriously think 
about, but the liability problems of getting them wrong are... severe.


Most common natural GCRs are fairly manageable if you can warn ahead 
(tsunamis, volcanos, hurricanes, even asteroids) and build resiliency 
(good civil society infrastructure, food storage). The ones to fear are 
the ones that are global (major climate fluctuation impairing 
agriculture, pandemics, cosmic eruptions). Anthropogenic GCRs are 
somwhat similar, but IMHO more dangerous because they are often adaptive 
and potentially larger.

-- 
Anders Sandberg,
Future of Humanity Institute 
James Martin 21st Century School 
Philosophy Faculty 
Oxford University