The advanced space ships of tomorrow will
be crafted from far-out materials with extraordinary resistance
to the harsh environment of space.
by Patrick L.Barry
Fast forward 50 years into the future.
Humans, seeking signs of ancient Martian
life, have flown to the Red Planet aboard extraordinary ships capable
of shielding the crew from the intense radiation of interplanetary
The successors to the Hubble Space
Telescope have been in space for decades -- longer than today's
satellites can usually survive -- taking breathtaking photos of
the cosmos and helping unravel the history and workings of our Universe.
Dozens of Earth-observing satellites with long-lived mirrors and
lenses provide scientists with daily global maps of deforestation,
urban sprawl, stratospheric ozone, and other environmental factors
-- bringing unprecedented scientific knowledge to the political
Huge orbiting solar collectors as big
as a dozen football fields generate gigawatts of power that are
beamed down to the energy-hungry civilisation below. Space-based
radio antennas hundreds of metres long listen for the faintest of
signals from civilisation's elsewhere in our galaxy. And spacecraft
propelled by vast billowing solar sails stand poised to carry their
first passengers across interstellar space.
Such marvels are probably many decades
away, but scientists are preparing for them now with an experiment
on board the International Space Station (ISS).
The Materials International Space Station
Experiment, or MISSE for short (pronounced "Missy") consists of
two suitcase-like containers, each holding hundreds of advanced
materials that might someday be used to build solar sails, large
antennas, super-spaceships, or thousands of other far-out devices.
This tray of
material samples may look a bit like the ultimate children's
water-colour set, but the contents of these trays certainly
aren't child's play. Scientists and engineers will use this
palette to paint the future of space utilisation.
During a spacewalk recently (August
2001), shuttle crew members attached the "suitcases" to the outside
of the space station and opened them up to expose the material samples
to the harsh environment of space. MISSE will be the first externally-mounted
science experiment on the ISS. Once opened, the suitcases will require
no attention from the ISS crew until a year later, when they will
be returned to Earth, where scientists will examine the materials
and see how well they fared.
satellites such as this one need to be made of materials that
can withstand the punishing conditions of Earth orbit for
years on end. Degradation of many currently orbiting satellites
has been faster than expected -- particularly the power-generating
solar panels. This has led to shorter-than-expected lifetimes
for these expensive satellites, motivating the aerospace industry
to develop more durable materials to use in their next generation
"Materials are really the enablers
for all future technology," says Bill Kinard, senior research scientist
at NASA's Langley Research Centre (LaRC). Researchers at LaRC manage
the experiment, which is a co-operative venture involving NASA,
the U.S. Air Force, and members of the aerospace industry.
"[With] MISSE, we're testing the candidate
materials and components that people are planning to use in the
future," Kinard says. "The first question is, 'Are they stable?
Will they survive for a long period of time in space?'"
Many people think of space as completely
empty. If that were true, choosing materials for spacecraft would
be easy! But space is far from empty, and many types of materials
don't survive for long in the harsh space environment.
"In space, there are high-energy protons
and electrons, ultraviolet radiation, atomic oxygen, high and low
temperature extremes, hard vacuum, galactic cosmic radiation, micrometeors,
man-made debris and a lot of other things as well," says Sheila
Thibeault, LaRC's principal investigator for MISSE.
in Low-Earth Orbit (LEO), where the
ISS and most satellites are, the "public enemy number one" is atomic
Here on Earth, the oxygen we breathe
is molecular. It consists of two oxygen atoms chemically bonded
together (O2). Molecular oxygen is fairly stable and safe, but in
the upper atmosphere, radiation often splits molecular oxygen into
atomic oxygen (O). Many of these oxygen atoms recombine to form
ozone (O3). However, some of the oxygen atoms drift up
to LEO, where they pose a serious threat to spacecraft.
Atomic oxygen is highly chemically
reactive. When it encounters other materials, it can steal atoms
of carbon, hydrogen, nitrogen, and other elements from the surface.
Over time, this will erode the material away.
A dramatic example of this erosion
was provided by the Long Duration Exposure Facility. LDEF was a
bus-sized materials exposure experiment similar to MISSE launched
in 1984. LDEF orbited for more than 5 1/2 years before it was finally
Some of the
materials on MISSE may someday be used to build vast, ultra-lightweight
solar sails that would use the pressure of sunlight to propel
humans across interstellar space. With areas exceeding that
of a small farm here on Earth, these sails must be able
to withstand the inevitable impacts of micrometeors -- dust-
and sand-sized grains zipping through space at high speed.
MISSE will help determine if candidate materials are indeed
LaRC invited the other NASA centres
as well as the larger aerospace community to submit materials to
fly on MISSE.
"This time we're primarily using the
space station to perform experiments to benefit other people in
other programs, as opposed to just supporting the station," Kinard
says. About 1500 total samples were approved for the mission, roughly
half of which were installed recently. The rest will go up in two
more suitcases scheduled to fly in about 18 months.
The samples represent a wide range
of materials. New solar cell materials promise to improve the lifetime
of satellites, including commercial communications satellites. Lightweight
radiation-shielding films may someday help protect astronauts on
their long trip to Mars. Optical materials that can better withstand
atomic oxygen will improve the reliability of Earth-observing satellites.
Thin, micrometeor-resistant polymers could allow the construction
of huge, fold-up antennas, as well as inflatable mirrors and lenses
for solar power collection. And ultra-lightweight polymers flying
on MISSE could someday be used to build the solar sails that finally
take humans sailing to another star.
All of this from two modest, suitcase-like
containers affixed to the outside of the ISS -- and, of course,
the dedicated work of thousands of researchers with a vision of
what space technology 50 years from now could be.