[ExI] How will air travel work in a green solar economy?

[Keith Henson]

On Fri, Jul 11, 2014 at 5:00 AM,  "Robert G Kennedy III, PE"
<robot at ultimax.com> wrote:

> No, there are 3:
>
> space-based photovoltaic satellites.
>
> either in GEO as the late great Peter Glaser invented/envisioned, or at
> the Sun-Earth L1 point as we and a few others have proposed. See for
> example our "Dyson Dots and Geoengineering: The Killer App to Bootstrap
> Us Ad Astra" article in JBIS vol.66, no.10-11, Oct-Nov 2013.

I don't know about getting power from L1, might be possible, might
cost too much, but in any case, sunshades are a good idea even without
energy from them.  The best part is that they can be reconfigured to
warm the earth as well as cool it.  I would not be surprised to see a
CO2 crash, and when it gets down below preindustrial levels, we may
head into an ice age.  If you think global warming causes problem,
imagine being able to take a bobsled on a downhill run all the way
from Newfoundland to Chicago

snip
>
> But of all of these, solar is the one with the most "headroom" for the
> human race, even just down here on /terra firma/.

You can do this in terms of physics, but the current trajectory on
ground solar runs up against economic cost.

The most optimistic person I know in the solar business is Ed Kelly of
StratoSolar.  Over time he expects solar power to get down to around
10 cents per kWh.

The cost for a barrel of synthetic oil (or synthetic jet fuel) is $10
for the capital cost and $20 per cent per kWh for the energy.  (It
takes 2 MWh to make the hydrogen to make a bbl of oil.)

So synthetic oil from the cheapest solar we can imagine will come in
at ~$210/bbl.  Given the damage oil prices only half that high are
causing to the economy, and the fraction of a ticket cost that's from
oil, I don't think a lot of people are going to be flying if we depend
on ground solar for energy.

> The United States alone encompasses 2 billion acres.

The US is not the only player.  Other countries have intractable
energy problems as well.

The only problem I see with Dyson Dots is the amount of material
needed, in the hundreds of millions of tons.  That large even in the
context of a power satellite project big enough to completely displace
coal an oil.  However, if we build the last half of the power
satellites with material from the asteroids, then we can keep the
mines going a few more decades and have all we need.

snip

> Btw, LNG would be an even better aviation fuel, especially for
> professional (non-amateur) flyers, with far less difficult handling and
> density problems than LH2. Expect to see LNG-fueled a/c in the next
> decade.

Maybe.  If you are making synthetic hydrocarbons, you can make stuff
more like current jet fuel.  LNG is still a PITA to handle.  Been
looking into using a few ships a week to make hydrogen (the only
choice) for Skylons.

Keith