Monday, September 10, 2012

A Piece Of Paper Above An Asteroid

Another way-out-there milestone occurred yesterday, [“yesterday” was Wednesday 9/5] when the Dawn spacecraft departed the giant asteroid 4 Vesta after a 13-month-long stay. Pushed along by a xenon-fueled ion thruster, Dawn has been gradually escaping from the gentle gravitational grip of Vesta since May and is now en route to its second destination, the even larger asteroid 1 Ceres, which it should reach in February 2015.

While at Vesta, the spacecraft did everything mission scientists hoped it would — and then some. The original timetable had a 40-day contingency in case the spacecraft had difficulty slipping into orbit around Vesta or while operating its suite of three instruments. But mission ops went so smoothly that, once a two-month-long stint in an especially tight orbit just 110 miles (180 km) above the surface ended, the entire 40-day pad remained unused. So the team returned Dawn to a higher-altitude mapping orbit, where it lingered long enough to record regions at Vesta's north pole that had been in shadow earlier in the mission.

Dawn Bids Vesta Adieu
at Sky and Telescope

At maximum thrust, each engine produces a total of 91 millinewtons -- about the amount of force involved in holding a single piece of notebook paper in your hand. You would not want to use ion propulsion to get on a freeway -- at maximum throttle, it would take Dawn's system four days to accelerate from 0 to 60 miles per hour.

Chemicals changed to electricity.

If I draw for instance a woman’s face
on a piece of paper the pencil point
pressing against the paper generates
enough force if applied in outer space
to move a spacecraft from one asteroid
slowly but surely to another one.

I’ve always wondered if something gets lost
when photography replaces drawing.

It’s still not clear exactly what gets lost
but that energy that used to push down
to create a drawing of anything
must have exerted in a physics way
that is an alchemical physics way
an equal and opposite reaction
and pushed the artist up whatever up
means in an alchemical physics way.

I’ve always wondered if something gets lost
when photography replaces drawing.

A spacecraft sent to study asteroids
is doing alchemy in outer space.

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