🚀 go-pugleaf

In article <BwwE85.Cox@netnews.jhuapl.edu> ejhof@netnews.jhuapl.edu (Hoffman Eric J.SDO 5186 ) writes:
>...the relative launch energy costs of--
>
>    a) direct ascent from Earth to Sun
>    b) into Sun via inner planet gravity assist
>    c) into Sun via outer planet gravity assist
>    d) direct ascent to Moon
>    e) direct ascent to Venus
>    f) into solar system escape trajectory?

Actually, the crucial issue is cost, not energy.  It's not *that* expensive
to just put the stuff into a hole in the ground, even if it's a hole designed
by DoE.  Being cost-competitive requires minimizing cost per kilogram.  The
cheap launch systems like laser launchers and electromagnetic catapults tend
to prefer lots of small packages over a few big ones.  The result is a very
strong cost preference for systems that do *not* require the individual
packages to carry navigation and propulsion systems, especially highly
reliable ones.  Those systems are damned expensive.

This rules out gravity assists and direct hits on planets.  The planets
themselves are tiny, and the gravity-assist aiming windows smaller yet.
To hit them, you really need precision tracking and course corrections.

The one marginal exception might be the Moon, since it's pretty close.
Hitting it with dumb packages might be feasible, especially with a launch
system like a laser launcher that can deliver thrust after the package
leaves the atmosphere (i.e. can correct for atmospheric effects on the
trajectory).  It would help if you're not too fussy about where on the
Moon the stuff ends up... but the Moon is too useful to turn more than
a small part of it into a trash dump.

The two targets you can hit without precision navigation are the Sun and
escape velocity.  The Sun is big and its gravitational field gets you a
lot of free focusing of trajectories.  And solar escape velocity is solar
escape velocity, regardless of exact direction.  Here the tradeoff is
quite simple:  escape velocity is sqrt(2) times circular velocity, so
to get a package into the Sun, we need to kill nearly all of Earth's
30 km/s circular velocity, while to get it to escape, we need only add
another 12 km/s or so.
-- 
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  henry@zoo.toronto.edu  utzoo!henry