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

Alfio Puglisi puglisi at arcetri.astro.it
Sat Jul 19 19:05:41 UTC 2014

On Wed, Jul 16, 2014 at 7:46 PM, Tomaz Kristan <protokol2020 at gmail.com>

> Over my small (Central European) country, there are about 10 large
> passenger planes every moment. Their combined power is roughly equal to all
> the hydroelectric, coal and nuclear power beneath them - combined.
> I am not sure is this pathetic or glorious fact. I guess both.

I think this discussion has been overly pessimistic. Maybe Tomaz you live
under the air corridor originating from some major European hub. But as you
scale things up, the picture is not that bad.
For example, Italy's usual daytime electric power is about 50 GW. Using the
numbers in this thread for 747s, it would sustain 150 of them flying
24h/day, which for sure you will not find in its sky.
Actually this agrees with the airlines protests about greenhouse gases
reduction efforts: they often state that the airline sector only
contributes for 2% of the total CO2 generation. Since electric power is
about a third of the global energy CO2 emission, the power output should be
similarly bigger. Or even more, if you consider that a good fraction of
electric power is generated with hydro and nuclear. It is reasonable to
conclude that air travel could be powered easily (for optimistic values of
"easy": you still need a suitable fuel which can be produced with
reasonable efficiency).


> On Wed, Jul 16, 2014 at 5:58 AM, Keith Henson <hkeithhenson at gmail.com>
> wrote:
>> On Tue, Jul 15, 2014 at 3:37 PM,   "Robert G Kennedy III, PE"
>> <robot at ultimax.com> wrote:
>> snip
>> >
>> > Yes, hundreds of Mt. Other than a first prototype article, we're not
>> > thinking of boosting any of it off Earth. Too dang expensive. For a
>> > project of this scale, it's off-world materials or nothing.
>> I suggest that even the prototype might be built of asteroid materials.
>> Though if sunshades come after power satellites, the transport cost
>> can't be very high.
>> > Now, I will concede that 2/3 of that mass in space is driven by the
>> > power generation function we're piggybacking on the sunshade function.
>> If you are mainly after energy, and building up space industry so it
>> could build sunshades, it might be better to populate GEO with power
>> satellites first.  If we eventually tap L1 for energy, the GEO power
>> sats could be converted to relay stations.  If we were pouring energy
>> captured at L1 into the earth system, sunshades might be required to
>> keep the energy gain down.
>> Keith
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