Newsgroup: it.fan.startrek
Titolo: How Capt. Kirk Changed the World

http://science.nasa.gov/science-news/science-at-nasa/2010/04may_dawn/
May 4, 2010: "Standard orbit, Mr. Sulu." Captain Kirk barks out the order
with such confidence. He knows the USS Enterprise can slip in and out of
planetary orbits with ease. But it's only easy in the realm of science
fiction. In the real world, such maneuvers have been impossible --until now.
How Capt. Kirk Changed the World (Vesta orbit 200 pixels)
An artist's concept of Dawn in "standard orbit" around asteroid Vesta.
[larger image]
Enter Dawn, NASA's cutting edge mission to the asteroid belt.
Powered with a futuristic sounding new technology called "ion propulsion,"
this spacecraft will perform space moves rivaling those of the Enterprise.
At this very moment, Dawn is slowly climbing away from the sun, beyond
Mars, on its way to its first destination, asteroid Vesta. Dawn will enter
"standard orbit" around this rocky world for a year, exploring its
mysteries.
Then Dawn will do something unprecedented in real-world spaceflight: exit
the orbit of one distant body, and fly to and orbit another. The second
destination is asteroid Ceres.
"Dawn will be the first spacecraft ever built to orbit two target bodies
after leaving Earth," says Marc Rayman, Dawn chief engineer at NASA's Jet
Propulsion Laboratory. "There's not even a concept for doing such a mission
with conventional propulsion systems. The spacecraft would have to carry so
much fuel, it would be too heavy to launch."
Instead, Dawn relies on ion propulsion, which doesn't require a huge
spacecraft. Rayman first heard the term years ago while watching ï¿½ you
guessed it -- Star Trek.
How Capt. Kirk Changed the World (Kirk and Scotty, 568 pixels)
Scotty: "I've never seen anything like it--and ion propulsion at that!"
Youtube video.
Using solar arrays spanning 65 feet, Dawn collects power from the sun to
ionize atoms of xenon. These ions are expelled by a strong electric field
out the back of the spacecraft, producing a gentle thrust. The weightless
and frictionless conditions of space flight allow this gossamer force
effect to build up, so the spacecraft gains speed slowly and continuously.
"Dawn isn't exactly a hot rod," says Rayman. "It would take 4 days to go
from 0 to 60. But it ultimately achieves fantastically high velocity while
consuming very little propellant. It uses only a kilogram of xenon every 4
days."
Typically, conventional rockets thrust for a few minutes at most before
they run out of fuel, then they coast to their destination. Dawnï¿½s engines,
on the other hand, are almost constantly active.
How Capt. Kirk Changed the World (Marc Rayman 200 pixels)
Dawn's Chief Engineer Marc Rayman of JPL. In the Youtube video, William
Shatner likens Rayman to Scotty of the Enterprise.
"Dawn will thrust for 5 ï¿½ years!" says Rayman. "It's already been thrusting
for 591 days. That's 62% of the time it's been in space."
This means Dawn must be very fuel efficient. "A typical Mars orbiter could
consume more than 600 pounds of propellants to enter orbit around the red
planet," says Rayman. "With its ion propulsion system, Dawn could do it
with less than 60 pounds of xenon."
Add all of these advantages together and you get a spacecraft that can
accomplish ï¿½ well ï¿½ the impossible.
"Dawn is taking us, in the truest sense, up close to two distant, alien,
unexplored worlds."
Its destinations -- Ceres and Vesta ï¿½ are two of the biggest asteroids in
the solar system. Indeed, Ceres is so big, it is actually classified as a
dwarf planet, and Vesta is not far behind. Yet to date they've been studied
only from a great distance, so they're virtually unknown. What is known is
that they're not alike.
"Vesta is more like the rocky bodies of the inner solar system, one of
which is right under our feet," explains Rayman. "And Ceres is more like
the icy moons of the outer solar system. Scientists think it may even have
a subsurface ocean of liquid water!"
How Capt. Kirk Changed the World (Ceres and Vesta 568 pixels)
Hubble Space Telescope photos of Dawn's targets, giant asteroids Ceres and
Vesta. [more] Credit: NASA/HST
Dawn's instruments will collect data and images to uncover the secrets
these two bodies conceal and perhaps reveal why they're so different from
one another even though they inhabit such similar regions of the solar
system.
"This mission will help us understand what the conditions were when Vesta
and Ceres formed at the dawn of the solar system. It will fit more pieces
in the grand puzzle of how our solar system formed and evolved ï¿½ and
perhaps how others do as well."
Executing new cosmic maneuvers, exploring alien worlds, answering profound
questions ï¿½ Dawn has it all. But Rayman thinks the most compelling aspect
of missions like Dawn may be that we are, in a sense, going along for a
deep-space ride.
"Dawn is taking us all on a virtual trip through the cosmos. It's not just
a mission by the JPL team, or by NASA, or by the U.S and its partner
countries. It's a mission of humankind -- something that represents all of
us who share a spirit of adventure and curiosity, a passion for
exploration. It's an extension of ourselves into the universe."
As one Star Trek crew member with particularly pointy ears would say --
"Fascinating."
Author: Dauna Coulter
-- 
Jolan Tru
Filippo "Hytok" Simone
http://perestroika.iobloggo.com/

 
http://science.nasa.gov/science-news/science-at-nasa/2010/04may_dawn/
E' il link che ho postato nel messaggio "propulsione ionica".....
Ciao,
luigi
-- 
/
+--[Luigi Rosa]--
\
Se Dio avesse voluto dare agli uomini dei computer,
li avrebbe fatti con 16 dita.

E' il link che ho postato nel messaggio "propulsione ionica".....
Porc... sorry, non avevo ancora scaricato il NG...
