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IT’S ALL GREEK: In his
class, West traces the roots of space knowledge.
Linda
A. Cicero |
Let’s say you want to cruise by the
outer planets. How long would it take to get to Neptune?
The principle of Hohmann transfer orbits tells us that
if the launch velocity were 41 kilometers per second,
you’d arrive in 31 years. But the Voyager 2 spacecraft,
launched in 1977, got to Neptune in 1989—only 12 years
after liftoff. Why? It had a gravitational assist, picking
up lots of extra speed as it swung around Jupiter.
From Hohmann transfers to heliocentric frames, Aeronautics
and Astronautics 279: Space Mechanics looks at the orbits of
near-earth satellites and interplanetary probes, as well as
the sun’s and moon’s effects on earth satellites. “It’s
some of the oldest stuff that’s taught in engineering
here, and it deals with classical problems of celestial mechanics
and orbital mechanics that date back to Newton,” says
assistant professor Matthew West. “It’s concerned
with problems such as how one makes observations of the current
positions of the planets and predicts where they’ll be
in the future, or how one knows when a comet is going to come
back.”
West grew up in the era of Star Wars and says he’s always
been fascinated with space—“from the point of view
of the problems, and from the romantic side of space travel.” As
a 4-year-old, he wanted to be an astronaut, and so do many
of the students who apply for graduate programs in the
aeronautics and astronautics department (Stanford has
graduated 18). “It’s a common aspiration
in the personal statements they write,” West says. “It’s
definitely cool.”
Courtney Kettenburg thinks she was probably 14 when she
saw the movie Apollo 13: “That did it for me. I knew
I wanted to design things to go into space.” One of five
Lockheed Martin engineers enrolled in West’s course,
Kettenburg is working toward a master’s degree in mechanical
engineering and applying just about everything she
learns in class to her day job. “At work, I build satellites.
Then I come in here and talk about how they’re going
to be launched and transported,” she says. “It’s
neat.”
West launches his course with the ancient Greeks, whose
achievements he calls “astounding.” Long before
Columbus challenged flat-earth fears by crossing the Atlantic, “the
ancient Greeks not only knew the earth was a sphere, but they
knew what the radius of the sphere was,” West says. “And
they knew how far away the moon was by careful observation
of eclipses.”
These days, designing the multiple-body trajectories that
boost satellites into orbit is a complex computational business.
So West challenges would-be space explorers to understand
the fundamentals behind fancy calculating tools like Matlab.
As he covers blackboards with velocity changes, cosines,
eccentricities and inclinations, West encourages
students in his classroom and those watching the Internet
broadcast from their desks at Boeing to ask hard questions—about
Bode’s law of mean distances of principal planets
from the sun, or Kepler’s laws of planetary motion. “These
days there are computer packages that do much of this material
for them,” he says. “But they still come here to
understand what the software is doing.”
Many of the class members are starstruck by NASA’s
plans for robotic and manned missions to Mars. To shoot
straight toward the Red Planet, West tells them, would
be “horrendously
expensive.” Instead, mission planners aim to arrive on
Mars at a certain altitude above the surface, using aero-braking
and hyperbolic approximations, and adjusting height and
velocity trade-offs up until the last moment. “It’s
all math and equations,” West says. “And the basic
equations haven’t changed since Newton discovered
them.”
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