IEEE Spectrum April, 2012 - 62

into an orbit that would take it all the way out to explore the
asteroids-called the Trojans-that trail Jupiter in its orbit.
NASA's Nanosail-D2, approximately the same size as
IKAROS but lighter, went up in late 2010 and deployed in
January 2011, when the craft unfurled its sail in an Earth orbit
low enough for amateur astronomers to see it. It was also low
enough for atmospheric drag to affect the orbit. In this case, that
was a feature, not a bug, because the point of the mission was to
clean up space junk by docking with it and then using the sail to
drag it down to a fiery disposal in the lower atmosphere.
It's a good thing that solar sails have many possible uses.
This helps to defray the costs of developing a technology that's
likely to be valuable should we ever
discover a rogue asteroid headed our
way. It also helps in overcoming the
all-too-human reluctance to begin
working on a problem that requires
a planning horizon measured in generations or even centuries.
As with other approaches to asteroid def lection, the solar collector
would not work well on all classes of
As MIT's training and education portal for
interplanetary rock. If you tried to use
it on an iron asteroid, the metal would
scientists, engineers and technical professionals,
instantly conduct the heat away from
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the hot spot. Besides, there would be
knowledge at MIT, acquire new skills, and take
no volatile material there to vaporize
anyway. The asteroid would just coninnovative ideas back to work.
tinue on its merry way, undisturbed.
A rocky body without any volatiles
would also be impossible to shift in
this way. So, clearly, other techniques
ShORT PROGRAMS
for dealing with those kinds of asterRegister for a 2-5 day intensive course at MIT this summer.
oids must also be developed.
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It does seem, though, that a solar
collector could divert a 300-meter
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water-ice object enough to prevent
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an Earth impact, and while remainpart-time basis, while still working and contributing to your company.
ing on station for just a few months.
Even more ambitious is the notion
Earn grades, MIT credit, and a certificate of completion.
of using such deflection techniques
to steer smaller water-ice-bearing
cUSTOM PROGRAMS
objects
into high Earth orbit, where
Enhance your organization's capabilities and expertise through
we could mine them for materials for
customized programs tailored to meet your specific needs and priorities.
rocket fuel, life-support systems for
space habitats, cosmic-ray shielding
for
such habitats, the construction of
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and other purposes. In 2010, President
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nauts could test a solar collector and
other deflection techniques.
We have plenty of time to study
the matter. But we do not have all the
time in the world.
❏

These are early days for designing such delicate space hardware, space sails included. But that solar sails can be manipulated in orbit and used for various purposes is no longer in doubt.
In 2010, two such sails flew in space. The more ambitious
one, a square about 14 meters on a side, was launched by the
Japanese space agency on an interplanetary trajectory between
Earth and Venus. Called IKAROS, for Interplanetary Kite-craft
Accelerated by Radiation Of the Sun, it proved that solar radiation pressure can be used both for primary propulsion and for
attitude control. A follow-on craft, planned for around 2020,
would use its solar sail during a close pass of the sun. There
it could gain enough momentum from light pressure to swing

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Table of Contents for the Digital Edition of IEEE Spectrum April, 2012