[ExI] Planetary defense

[Anders Sandberg]

Samantha Atkins wrote:
>
> I am much much less concerned with asteroid protection as the 
> probability of such is utterly minuscule compared to the certainty of 
> material shortage on the ground and other problems if we do not 
> establish a space beachhead soon.  I am dismayed at the amount of 
> brains that are dedicated to this tiny possiblity versus exploiting 
> such opportunities.

The impact community is warm to space colonization. It is just that 
there are practical realities to be dealt with:

Capturing asteroids is not at all easy. Leaving the safety aspects 
aside, the delta v needed to make a NEO end up in a convenient 
Earth-bound orbit is significant. It is often much larger than the 
amount needed for asteroid deflection. Clever dynamical solutions like 
multiple passes by the Moon and Earth to bleed of velocity probably 
exist, but to use them we need 1) very exact location data, 2) a bit of 
luck to find a NEO in the right initial orbit, and 3) lots of time, 
since the low energy orbits tend to loop around all over the place.

Second, the value of matter in space is higher than on ground. Launching 
stuff up is *expensive*. Dropping things down is almost as expensive too 
- you need a nearly equivalent delta v (aerobraking can maybe give you 1 
km/s or so). I doubt a space manufacturing industry will ever be 
competitive with an Earth manufacturing industry for the Earth market. 
However, it can build valuable things like solar power satelites.

-- 
Anders Sandberg,
Future of Humanity Institute
Philosophy Faculty of Oxford University