starship-design: Charting a Course to the Stars

["L. Parker" <lparker@cacaphony.net>]

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Charting a Course to the Stars
Largest Spacecraft To Sail the Galaxy




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a larger 198k view.
The vast wispy sheet, depicted in the NASA artist's concept at left,
is an interstellar kite -- a Space Sail -- that could power
interstellar flights beyond our Solar System.

Engineers at the Interstellar Propulsion Research Office of NASA's
Marshall Space Flight Center in Huntsville, Alabama, are devloping a
rigid-yet-lightweight carbon fiber material that could be used to
build just such a giant space sail.

NASA would like to be able to launch such a sailing craft --the
biggest, fastest interstellar probe ever -- toward exotic destinations
beyond our Solar System.

The thin reflective sails, made of composite materials, would span 440
yards. That's twice the diameter of the Louisiana Superdome. Sunlight
falling on the sail would push the probe out of the Solar System and
across our Milky Way galaxy.

Propulsion for later missions might use microwave beams or laser beams
to drive the sail.

Flat out fast. This spacecraft would be fast, very fast. It would
accelerate to a lightning-quick 58 miles per second, which is more
than ten times faster than a space shuttle's speed of 5 miles per
second in orbit. It could cover the distance from New York to Los
Angeles in less than a minute.

The first intentional interstellar probe probably would travel beyond
the edge of the Solar System to a distance of more than 23 billion
miles. To astronomers that would be a distance of 250 astronomical
units. One astronomical unit is the distance from Earth to the Sun --
93 million miles.

Alpha Centauri. By comparison, if the distance from Earth to the Sun
equaled one foot, Earth would be a mere 6 inches from the planet Mars,
38 feet from the planet Pluto, 250 feet from the outer boundaries of
the Solar System, and an immense 51 miles from the nearest star
system, which is known as Alpha Centauri.

Such a round trip from Earth out beyond our Solar System to the Alpha
Centauri star system and back to Earth would take about fifteen years.


People will follow. Sail propulsion will be used for robot missions to
distanct stars and then, later, for human travel.

How soon? Humankind's first planned venture outside of the Solar
System could begin as early as 2010. The challenging and unprecedented
15-year journey would be the most audacious deep space mission ever
undertaken.



Click the image to view a
288k QuickTime video movie
of interstellar travel by solar sail.
Then click Back to return here
The so-called "precursor mission" would travel five times faster than
the famous Voyager interplanetary probe launched in 1977. In fact, the
new sailing probe would pass the old Voyager in the year 2018. At that
time, it would have gone as far in eight years as Voyager would have
journeyed in 41 years.

Why use a sail? Old-fashioned booster rockets need so much fuel that
they can't push their own weight beyond the Solar System into
interstellar space. Space sails, on the other hand, require no fuel.

Imagine the wind pushing sailboats across water on Earth. The thin
reflective space sails would be propelled through space by sunlight,
microwave beams or laser beams.

Rays of light from the Sun would deliver Herculean momentum to the
voluminous structure. Nothing this big has ever been deployed in
space.

How big are they? The carbon fiber sailcloth would have a density of
less than one-tenth ounce per square yard. That's the equivalent of
flattening out one raisin so much that it covers a square yard.

Sails in space would have a very large surface area -- about a
half-mile wide -- but would be thinner than cellophane. The
sailcloth's carbon fiber material would have a thin coating of
reflective aluminum.

The composite material sailcloth, rigged for interstellar flight,
would be sent to space on an old-fashioned expendable space rocket.
There, it would unfurl like a fan.

Sailing through the galaxy. The concept of space sails is not new.
About the time Jamestown was being established as America's first
permanent colony at dawn of the 17th century, German astronomer
Johannes Kepler penned a letter to Italian astronomer Galileo,
advocating "ship or sails adapted to the heavenly breezes" to travel
to Jupiter or the Moon. Having observed that a comet's tail always
faces away from the Sun, Kepler concluded that light from the Sun must
exert a force that pushes its tail away.

Rays of light emanating from the Sun provide tremendous momentum that
could push a solar sail to a speed of about 150,000 mph. That would
allow space sails to travel an interplanetary route four to six times
faster than old-fashioned rocket propulsion systems. In addition to
moving remarkably faster than traditional systems, solar sails would
require no fuel. The Sun would supply all of the energy.

The invention of strong lightweight composite materials in the 20th
century made space sailing possible.



Click the image to see
a larger 198k view.
Space sail team. Team members from Marshall Center in Huntsville,
NASA's Jet Propulsion Laboratory in Pasadena, California, and the
University of Washington in Seattle are working to make space sails a
reality. JPL is responsible for NASA's interstellar missions, while
Marshall is responsible for developing transportation systems for
missions.

NASA's Advanced Space Transportation Program pushes technologies to
increase reliability and reduce costs. Marshall engineers are exposing
space sail composite materials to harsh conditions in a simulated
space environment and testing their performance and durability in
extremely hot and cold temperatures.

The team needs to figure out how to build, package and unfurl a solar
sail and control its direction of travel through space. Since the sail
would get very close to the Sun, thermal protection will be important.


Other ways to sail. A different concept of space sailing concept is
known as mini-magnetospheric plasma propulsion (M2P2). Rather than
sailcloth, it blows up a huge magnetic bubble for a sail.

The probe would sail away as the bubble was pushed along by charged
particles of the solar wind, instead of rays of sunlight. The charged
particles of the solar wind would interact with the magnetic field to
push the magnetic bubble.


Lee


"People do love to go to weird places for reasons we can't imagine --
mostly because they have too much money."
                            - Freeman Dyson

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