[Server-sky] Server Sky transport energy comparison

Michael Turner michael.eugene.turner at gmail.com
Mon Jul 29 03:56:53 UTC 2013

EROEI could be a great way to sell Server Sky. But how sensitive are
the computations to style of launch?

Ground-based accelerators are suddenly back as a buzz topic with the
Slingatron KickStarter campaign.


It wouldn't be my first choice of what accelerator concept to throw
some money at, but I think all the promoters of the various
accelerator concepts talk about a range of $200-$600/lb under the
assumption of present-day energy costs.

What you might do is present EROEI projections in tabular format, with
the two dimensions being "thinsat generation" and "style of launch".
Ideally, the finance, economics and EROEI of thinsats still work out
nicely for rocket-based orbiters, even if SpaceX finds a launch-cost
plateau for rockets and accelerators never work out. But in a future
where energy is more expensive, EROEI will become ever more important.
All accelerator schemes require less total energy than rockets,
because so much less energy is expended on lifting fuel that's used to
lift fuel that's used to lift ....

Some accelerator schemes might feature a fair amount of energy
recovery as well. Carl Knowlen once told me that ram accelerators
could be recoilless (IIRC he even talked about /negative/ recoil), and
could recycle almost all of their post-detonation gases and much of
their heat energy. The Slingatron might "power down" regeneratively
for reloading -- with fast enough launch cycle times, maybe even
capacitative storage would make sense.

Michael Turner

Project Persephone
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Tel: +81 (3) 6890-1140
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turner at projectpersephone.org

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On Mon, Jul 29, 2013 at 3:23 AM, Keith Lofstrom <keithl at kl-ic.com> wrote:
> Launch costs a heck of a lot more per kilogram than ship/rail/truck,
> but server-sky thinsats produce a heck of a lot more energy per
> kilogram than a terrestrial solar panel.  The transport energy
> payback time for a Chinese solar panel sent to the New Mexico
> desert is 60 days, for a first generation thinsat is 22 days.
> Second generation ultralight thinsats, ballasted with harvested
> space debris, may have transport energy payback times of less
> than five days.
> See http://server-sky/Transport
> Third generation thinsats, manufactured in space from lunar
> materials (chips and rare materials still earth launched)
> will be cheaper still, but my crystal ball is too cloudy
> for usable estimates that far in the future.
> Keith
> --
> Keith Lofstrom          keithl at keithl.com         Voice (503)-520-1993
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