How many SPSes for $87 billion ?

You have many good points and I enjoyed reading your reply (especially
philosophy points).

Let me again summarize the key (non philosophical) issues here:

1. Vulnerability of SPS

You think an SPS is not vulnerable to terrorism or embargo in our
current geopolitical system. I disagree.

Here are several obvious attacks on SPS off the top of my head:
A. Taking over encrypted communications channels to use robots at the
SPS to disable it. Coudl be done in a matter of minutes.
B. Using a computer virus to change where the SPS is pointing or fire
thrusters to deorbit it (and terrorize people with where it will crash).
C. Trusted engineers being secret sleeper terrorists.
D. Destruction of rectennas on the ground through conventional means.
E. Given the wide prevalence of space transports assumed by large use of
SPS, hijacking one of these vehicles either onboard or remotely and
crashing it into an SPS.
F. Exploding a fragmentation weapon in geosyncronous orbit (or other SPS
orbit) at a distance away and lettign the shrapnel over time destroy the
SPS. Note that this may happen anyway, as NASA and other studies show
that there is already so much space junk that there is a high risk of a
cascade failure of all orbiting satellites etc. ans the shreddign of one
leads to the shreddign of others etc. in a total destruction of all
space infrastrucutre in various orbits.
G. Ground based lasers destroying the SPS.
H. EMP destruction of SPS from nearby nuclear blasts.
I. Direct rocket attacks -- the only defense assumes a quick and
complete militarization of space and I think that is a bad thing, for
among other reasons that once space is militarized conflicts between
Powers or one power going rogue could use this military potential to
destroy all SPSs.
J. Any organization can go on strike. Any set of organizations can form
a cartel. For example, Singapore dependent on one desalinization plant
is still vulnerabel to strikes or ever increasing financial or other
pressures from the owners or controllers of the facility. Anyone gaining
control of a significant fraction of SPS administration will have a
terrible amount of Power over the world. Why engineer in such societal
problems when there are alternatives which are more supportive of a
distribution of Power (and power) among diverse people?
K. Timed explosives smuggled onto a cargo flight to an SPS.
L. If there are habitats used to build SPSs, the habitats striking the
SPSs or simply towing them away or temporarily disabling them. Remember,
destruction does not have to be done for rational reasons. People can
and do go suicidal and take others with them.

In short, I think suggesting SPSs are secure because they seem far away
is a problematical as thinking the USA is immune from terrorism because
there are big oceans surrounding it.

2. Economics

I think we have a genuine disagreement here -- one which reflects a
disagreement in the energy field (classically centralized oil and big
nukes vs. distributed renewables & efficiency & lifestyle) and which
won't be resolved anytime soon here. Personally I think you too are
doing a bit of hand waving saying these alternatives won't work without
presenting current numbers regarding energy use. :-) Suffice it to say,
I have called into question that SPSs are economically cheaper or
environmentally better or more secure than renewables and energy
efficiency and remain unsatisfied with the communities response --
especially because the solutions I advocate can be done with small
investments and succeed right away, where as SPS requires a huge
investment and still has tecnical and logistical uncertainties. In
general, the principle here is not directly environmental -- it is just
(to my mind) common sense incremental investment strategy. You or others
may not agree, but I think there is enough uncertainty here to doom SPS
on economic grounds anytime soon (especially given rapid improvements in
PV, wind, etc.). That means SSI and the related community (e.g.
Criswell) might be more productive focusing on other approaches to
development of humanity in space and prosperity on Earth (such as self
replicaitng seeds, coordinting free researches into Buck Fuller type
life support issues, etc.). And of course SSI does do some of these
other things, so I think that is a good thing. Still, judging from the
last conference and the web site comments regardign the planned
conference -- SSI still seems philosophically fixated on SPS as *the*
route to habitats.

All the best.

--Paul Fernhout

P.S. In the excerpt you clipped it mentioned Iceland gets its power from
Hydro and Geothermal -- so that would be the energy used to create
Hydrogen as a transfer and storage medium.