Tuesday, April 1, 2014

A mission of (anti-)gravity

More than sixty years after its first publication, Mission of Gravity by Hal Clement (the pen name of Henry Clement Stubbs) remains one of SF's premier examples of world-building. Clement, a chemist, gave much thought to the physics, chemistry, climates, and biology of the fictional world Mesklin.

And a wondrous place Mesklin is, too. For valid -- if unusual -- reasons, its surface gravity varies from about three times Earth normal at the equator to hundreds of times Earth normal at the poles.

A classic
Mission of Gravity is also a great adventure yarn.

Last year's movie Gravity was very popular, widely praised, received ten Oscar nominations and just recently was awarded seven Oscar wins. It is, without doubt, an exciting tale. The cinematics are stunning. The crafting was meticulous.

The science, alas, is atrocious. You needn't take my word for it, since Entertainment Weekly has it covered. See, " 'Gravity': Panel of astro-experts on the science behind the film." I weep for the science adviser (whom, I suspect, is relieved to have gone unmentioned on the screen credits).
The ISS: it's BIG

Most fiction requires the willing suspension of disbelieve -- my own stories, too, doubtless -- but that's hard to sustain when the underlying premise of the movie (a chain-reaction debris storm of space junk, big enough to destroy the International Space Station) is so jarringly improbable. The ISS is longer than a football field. It masses about a million pounds. Its critical systems are replicated.

What the scriptwriters might call stage-setting, we SF authors call world-building. That's a use of "world" in its broadest sense: the overarching context. The "worlds" SF authors build encompass such story settings as artificial environments (e.g., spaceships and space stations), alternate histories, imagined futures, and, yes, planets and moons.

Let's shift to world-building in that describe-a-planet sense. How many ways are there to mess up that sort of world-building? Lots, of course. Here is io9's stab at answering that question: "Blunders People Make in Inventing Fictional Alien Worlds."

(io9 also offered this advice to the aspiring SF author: "10 Things That Every Brand New Creator of Science Fiction Should Know." The first tip -- "You're still just telling personal stories" -- might seem to downplay the emphasis of this post. Not so. Personal stories and SFnal background are complementary. Both are vital to the genre -- as this top-ten list gets around to at item 9: "Doing your homework is half the battle."

So how does one get the science right (besides heeding the science adviser one has hired)? Perhaps through learning by example. Check out (from Astronomical Society of the Pacific), "Science Fiction Stories with Good Astronomy & Physics: A Topical Index."

Lots of good reading there ...


Anonymous said...

shane~aka p.h.
nice shot on the science fact article june 2014 analog
nothing to add.
good bibliography
hard work noted

Edward M. Lerner said...

Thanks, Shane.

For anyone puzzled by Shane's telegraphic comments ... my contribution to the June issue of Analog (a magazine's cover date indicates when an issue goes off sale, not when it comes on) is the latest in my essay series about the science behind common SF tropes. This latest installment deals with what has been called, variously, ESP, psi, and the paranormal.

- Ed

Anonymous said...

Hi Ed. I'm an orbital mechanic, but I VERY much enjoyed the movie "Gravity". I did so, because I was able to edit a plausible backstory in my head as I ran into things that didn't match anything currently flying. First off, it was obvious that this was taking place a few years in the future AFTER the space shuttle has been put back into service. In the intervening years, A few things have changed. First, an earlier shuttle mission had retrieved the HST and hauled it back down and it was re-launched into an orbit that matched, but led the ISS by a few miles so that HST servicing missions that went bad could easily reach the ISS. Further, the Chinese had launched their Station into an orbit which trailed both the ISS and HST for the same reason.

The problem with the destructive ASAT test was that it was initially launched from the same latitude at the ISS inclination, but instead of following a direct orbit (eastward), it is in a reverse orbit (westward) and had just been placed in a Hohmann transfer orbit to reach geo-sync altitude moving in the opposite direction from the rest of the Geo-sync satellites. (ASAT are normally launched into REVERSE orbits since they're typically "kinetic-kill" weapons, and nothing says "kinetic" like a satellite passing you at 2x orbital velocity). The transfer stage suffered a catastrophic failure shortly after the initial transfer burn which created a debris cloud moving in a reverse Hohmann transfer orbit between reverse LEO and reverse GeoSync orbit. When the debris cloud crossed the GeoSync orbit headed the wrong way, it destroyed a communication satellite which began a cascade of satellite failures running backwards along the geosync orbit. The same thing then happened when the debris cloud passed the LEO launch path headed in the opposite direction at the bottom of its Hohmann Transfer orbit.

As to Matt falling off the ISS, that wasn't due to gravity. The impact of the debris caused the ISS to begin to rotate. As the two astronauts bounced through the rotating space station, they got hung at the far end of the rotating structure. The force they are experiencing is not gravity, but rather rotational inertia. He's not falling, but instead being "slung" off the slowly spinning ISS.

Edward M. Lerner said...

That's quite clever, Anonymous. Thanks for sharing it.

If asked, I somehow doubt the script writers could have come up with that explanation ...

- Ed