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  • Ancient people saw them as messages from the Gods, as supernatural winds that blew from

  • the realm of spirits.

  • Modern science has linked these polar light shows, called auroras, to vast waves of electrified

  • gas hurled in our direction by the sun.

  • Today, researchers from a whole new generation see this dynamic substance, plasma, as an

  • energy source that may one day fuel humanity’s expansion into space.

  • What can we learn, and how far can we go, by tapping into the strange and elusive fourth

  • state of matter?

  • A

  • small cadre of scientists has come to Fairbanks, Alaskato realize what may seem an impossible

  • dreamto revolutionize space travel.

  • Dr. Ben Longmier and his team from the University of Michigan have designed a whole new type

  • of rocket engine that promises a faster and more efficient way to get around in space.

  • They are here to test components of this rocket by sending them aboard helium balloons to

  • an altitude of 30 kilometersinto the harsh environment of space.

  • Above the north and south poles, conditions are about as harsh as you can get. Our planet

  • is bombarded with a steady steam of charged particles from the Sun.

  • Earth’s magnetic field accelerates and channels them, turning the night into a spectacle of

  • color.

  • While most astronauts train to live and work in zero gravity, or to move around in bulky

  • space suits, these would-be space explorers are preparing to negotiate some of Earth’s

  • harshest environments.

  • Once they launch their payload, it will rise slowly into the upper atmosphere.

  • After drifting through the night, above 99% of Earth’s atmosphere, the payload will

  • detach from the balloon and parachute down to the ground.

  • Where it goes and finally lands will depend on highly variable wind conditions. The team

  • must be prepared to retrieve it across a large stretch of Alaska’s snowy wilderness.

  • To understand the revolutionary nature of the idea they are pursuing, we go back to

  • the dawn of rocketry.

  • In over a hundred years, the technology of a rocket has hardly changed.

  • Fill a cylinder with volatile chemicals, then ignite them in a controlled explosion.

  • The force of the blast is what pushes the rocket up.

  • Nowadays, chemical rockets are the only ones with enough thrust to overcome Earth’s gravity

  • and carry a payload into orbit. But they are not very efficient.

  • The heavier the payload, the more fuel a rocket needs to lift it into space. But the more

  • fuel a rocket carries, the more fuel it needs.

  • One of the fabled Saturn V rockets of the Apollo era, for example, weighed in at 177,000

  • kilograms. Filled up with fuel, it weighed almost 16 times that.

  • The space shuttle, with maximum payload, weighed about 100 thousand kilos. Add tanks and fuel,

  • and it lifted off at 2 million kilograms.

  • Regardless of weight, for a spacecraft to escape Earth’s gravity and go into orbit,

  • it must reach a minimum speed of 40,000 kilometers per hour.

  • The energy needed to do that meant there wasn’t enough fuel for a sustained acceleration to

  • more distant planetary shores.

  • Most missions beyond Earth have relied instead on their initial launch speed to coast to

  • their destination.

  • The twin spacecraft of Voyager, for example, did not have enough speed to reach its current

  • position at the edge of the solar system.

  • To give them a boost, flight planners sent them into Jupiter’s gravitational field,

  • using its pull to sling shot them out to Saturn.

  • Voyager 2 got further assists from Saturn and Uranus. Voyager 1 used Saturn to accelerate

  • to almost 63,000 kilometers per hour.

  • Ben’s rockets promise far greater gas mileage than traditional chemical rockets, but with

  • enough power to reach distant targets more quickly.

  • The idea is that once in space, his rockets use electricity to create a weak force, which

  • over time can accelerate them to very high speeds.

  • They run on the same fuel that nature uses, literally, to power the cosmos.

  • Not long after its explosive beginnings, the universe was awash in vast stores of hydrogen

  • gas.

  • But even as the universe continued to expand, gravity drew clumps of matter into ever-denser

  • concentrations. The earliest stars took shape, immense balls of hydrogen gas, hundreds of

  • times the mass of our sun.

  • As they contracted inward, they heated up and ignited.

  • Intense radiation now began to flow through the voids. That had the effect, all through

  • the universe, of stripping electrons away from the primordial gas.

  • The universe became filled, not with solids, liquid, or gas, but with a fourth state of

  • matter: plasma.

  • On our planet, plasma occurs only in rare circumstances: in a hot flame, a bolt of lightning,

  • or in a blown electrical transformer.

  • Made up of negatively charged electrons and positively charged ions, plasma is in most

  • cases electrically neutral since the charges balance each other out.

  • That led the physicist Irving Langmuir in the 1920s to compare it to the clear liquid,

  • plasma, that carries blood cells through our bodies.

  • The development of radio led to the discovery, high above the Earth, of a natural plasma

  • ceiling, the ionosphere. It hovers above us, reflecting some radio frequencies and absorbing

  • others.

  • Its importance became clear when engineers noticed that radio waves could, under some

  • conditions, travel beyond our line of sight.

  • They discovered that signals could be bounced deliberately off this conducting layer, in

  • what’s calledskywave propagation.”

  • In World War 2, a whole new age of global communications came of age when radio was

  • used to execute complex worldwide logistics of troop and ship movements.

  • The presence of the ionosphere is due to a steady stream of charged particles, or plasma,

  • that comes from the sun.

  • A spacecraft with complex computer components must be able to survive constant exposure

  • to these particles.

  • As part of their design process, Ben and team want to test some of the specialized components

  • of their rockets in the plasma-fill environment of our upper atmosphere.

  • Those components will be mounted on a simple frame attached by rope to a high-altitude

  • balloon. The frame is also outfitted with an array of novel sensors to take independent

  • readings. One holds a colony of bacteria.

  • The idea is that the bacteria itself can detect radiation. So it mutates in a certain way

  • or in a very known way so that if you send it into an environment with a lot of cosmic

  • rays and perhaps a lot of x-rays from the aurora itself, it mutates. And so well

  • detect sort of the level of radiation it’s exposed to by looking at these mutations after

  • weve recovered the baceria after flying them to the edge of space in one of these

  • balloon capsules.

  • Another is a series of tiny GoPro cameras converted to record the intensity of infrared

  • and ultraviolet light normally hidden to the human eye.

  • The team uses Argon gas to insulate instruments against the cold, with chemical packets added

  • for warmth.

  • They stabilize the frame with tiny gyroscopes, and outfit it with GPS devices for tracking.

  • This team is doing much more than just designing instruments to survive a rain of charged particles.

  • Their goal is to design spacecraft that actually harness the explosive properties of plasma.

  • Unlike most matter on Earth, plasma conducts electricity and responds to magnetic fields.

  • In space, these properties influence the formation of structures like galaxies and nebulae.

  • And they play a role in some of the most violent processes in the universe, such as the formation

  • of a black hole.

  • It forms in the wake of a giant star’s death, when matter collapses into its core. It swirls

  • in along what’s known as an accretion disk.

  • Magnetic fields take shape on the disk, rising and twisting around the polar regions. They

  • draw huge volumes of plasma up, then shoot it out at high speeds.

  • These plasma jets can extend far beyond the largest black holes. You can see them blasting

  • continuously from the centers of galaxies, reaching thousands of light years into space.

  • Studies of one giant nearby ball of plasma show what a complex and volatile substance

  • it can be.

  • In the core of our sun, high heat and crushing pressures cause hydrogen atoms to crash together.

  • That sets off a nuclear reaction in which hydrogen atoms fuse into heavier ones like

  • helium and carbon, generating heat.

  • This heat slowly rises to the surface of the sun in vast plumes of plasma.

  • You can see evidence of this process, called convection, in a pattern of ever-evolving

  • blobs known as granules. They are like the tops of thunderstorms.

  • Even as energy builds within, the sun's gravity and density can stifle its escape.

  • What carries it out are magnetic fields. They twist and wrap around, channeling energy to

  • the surface.

  • The fields can power immense loops of hot gas, about 60,000 degrees Celsius, then rise

  • up from the solar surface and fall back.

  • The largest eruptions, called coronal mass ejections, can reach up to 6 million miles

  • per hour as they hurtle out across the solar system.

  • They can literally slam into Earth’s own magnetic field.

  • Because solar particles are charged, a portion follows the orientation of Earth’s magnetic

  • field lines.

  • Finding an opening at the poles, these particles race down into the atmosphere.

  • You know this is happening when you see the beautiful lights of the aurora borealis in

  • the far north, or the aurora australis in the south.

  • They appear when charged solar particles collide with oxygen molecules in the upper atmosphere,

  • causing them to glow blue, red, and green depending on altitude.

  • Flying 350 kilometers above the earth, astronauts in the international space station watch in

  • awe as the aurora shimmers, framed by the glow of stars and cities at night.

  • Back in Michigan, Ben and his team have set up a lab to harness this strange substance

  • in a whole new generation of rocket engines.

  • The lab recalls an earlier period of space exploration.

  • It features a giant vacuum chamber, built in the 1960s in hopes of winning a contract

  • to test Apollo moon rovers.

  • The chamber has given this small university team the ability to accelerate their research

  • into the physics of plasma and rocket engine design.

  • They are actually part of an larger community of plasma rocket scientistswithin NASA

  • and within private companies like Ad Astra of Houston, Texas.

  • Because plasma does not occur naturally on Earth, the challenge is to create it, then

  • harness it.

  • The teams inject a gas, commonly argon, into a chamber. They bombard it with radio waves,

  • which strip electrons from the gas and turn it into a plasma.

  • The soup of electrons and ions accelerates as it moves through a magnetic field generated

  • by superconducting magnets. A second radio blast heats it up to a million degrees Celsius.

  • That’s enough to blast it out and propel a spacecraft.

  • The idea of using plasma to power rockets is not a new one.

  • The Polish physicist Stanislav Ulam is said to have been inspired by atom bomb tests in the

  • 1940s. He speculated that waves of plasma from small nuclear detonations could propel

  • a spacecraft to extreme speeds.

  • In the 1950s, that idea animated dreams of exploring the solar system in spacecraft like

  • this 360-ton Mars-bound vehicle.

  • The idea gained funding in the Orion project, with the idea of driving a spacecraft with

  • nuclear pulses and landing on Mars in only a month. Concerns about radioactive exhaust

  • helped doom the project.

  • Plasma rockets, energized by nuclear reactions, were revived in the Daedalus and Nerva projects

  • of the 1960s, and again at the beginning of this century as part of a proposed journey

  • to Jupiter’s moon Europa. Rising costs killed that mission.

  • Newer plasma rocket concepts have switched to solar energy to power their engines.

  • Among the most ambitious, the DAWN mission was sent into orbit aboard a Delta 2 rocket

  • in the year 2007. It then headed out on a ten year mission to the asteroid belt.

  • It uses only about 10 ounces of xenon gas fuel per day. With engines designed to fire

  • for over 2000 days, over time it is expected to gain an additional 38,000 kilometers per

  • hour.

  • After a gravity assist from Mars, Dawn arrived at the asteroid Vesta in 2011.

  • It spent a year mapping its surface and seeking clues to its interior structure.

  • Now headed for Ceres, a dwarf planet located within the asteroid belt, Dawn will be the

  • first probe ever visit.

  • Made up of rock and ice, Ceres may well have an internal ocean of water and ice. It takes

  • us back to the formation of the solar system, when objects like this grew and developed

  • into planets.

  • Long range missions like Dawn are just one of many uses for plasma rockets.

  • So nasa launches spacecraft with ion engines and hall thrusters on board. Almost every

  • new geostationary satellite that a company will invest in and put up in orbit will have

  • some sort of electric propulsion device on board to do station keeping, to do little

  • changes in attitude and maneuvers to keep it in its geostationary orbit.

  • NASA is planning to use a plasma rocket to do some even heavier lifting, as early as

  • 2016.

  • Flying at an altitude of three hundred fifty kilometers, the International Space Station

  • whips around the Earth every one and a half hours.

  • To stay aloft, it must maintain a speed of 28,000 kilometers per hour. But its solar

  • panels and crew modules smack into so many tiny molecules in the upper atmosphere that

  • it gradually slows down and loses altitude.

  • To stay aloft, the station uses up around 4,000 kilograms of fuel per year. That fuel

  • must be flown up from Earth, which in turn reduces the amount of food, water, people,

  • and equipment that a resupply mission can deliver.

  • The idea is to use a plasma rocket to help boost the station to a higher altitude, powered

  • by electricity generated by solar panels aboard the station.

  • Plasma rocket builders like Ben hope to one day scale up the technology to power a long-range

  • human mission.

  • After weeks spent accelerating in earth orbit, the rocket would make a break for Mars. Cutting

  • flight time from a year to several months would lower costs and crew hazards.

  • In the meantime, Ben has his sights set on what he sees as an even larger revolution

  • in space explorationusing plasma rockets to power a fleet of miniature spacecraft.

  • Ben’s rockets are so small they can fit into your carry-on luggage.

  • So here we have a cube sat. This is a small spacecraft, it’s total mass would be something

  • on the order of 5 kilograms, that's about 10 pounds. It’s 30 centimeters x 10 x 10.

  • This is considered a 3U spacecraft , 3 units of 10x10x10. And we’d like to send this

  • small spacecraft up with one of our new propulsion elements in it. This is a rapid prototype

  • propellant tank. So we would use this tank to store our propellant. Initially we have

  • an idea to use a very simple propellant.

  • The NASA craft Dawn uses the inert gas, Xenon, as fuel.

  • Ben’s team has turned to another type of fuel, that’s more compact, can store more

  • energy, and is less volatile.

  • Distilled water.

  • Well ionize that propellant with radio waves and that will form a plasma, so well

  • strip off some electrons. We'll have this sea and collection of ions and electrons.

  • We accelerate, we superheat that plasma and then we accelerate it through a magnetic nozzle.

  • The plasma never touches a material boundary so it never cools off. All of that could be

  • contained within the spacecraft so the propellant tank is designed to be the right size and

  • dimension and we have a propulsion module within the cube sat itself. This is an early

  • prototype circuit board, just this component, that would sit inside the cube sat and it

  • would take the DC power from some sort of solar panel on the surface, change that DC

  • power into our radio waves that we need to ionize the propellant into a plasma.

  • We then shoot this plasma out the back and we apply just a little bit of force, it’s

  • not a whole lot, it’s something like the force of a sheet of paper sitting in your

  • hand. And because there’s very little drag in space, we apply this small amount of force

  • applied over a very long amount of time to accelerate to very high velocities with this

  • spacecraft. So if we do that we can send these little micro spacecraft, nanosats, we can

  • send them to places like the moon, we can send them to mars, and someday we’d like

  • to send them even as far as Jupiter and maybe put some little sensors on board and be able

  • to detect possible life on some of these moons near Jupiter and Saturn.

  • So instead of a 1 billion dollar nasa mission to explore the moons of Jupiter, we can get

  • away with something like a million dollar spacecraft mission with one of these small

  • sats. So that’s the real advantage, being able to have a very low barrier to entry financially

  • and technologically to make some of these innovations really quickly, go fly them, go

  • fly often, and make these discoveries.

  • Already, hundreds micro, nano, and even smaller satellites are in orbit. They get into space

  • by piggy backing on commercial or government launch vehicles. Their missions range from

  • communications and intelligence to Earth imaging.

  • Because the cost of building them is so low, the number of tiny satellite missions is on

  • the rise.

  • With an array of plans already materializing, the team is tapping into satellite traffic

  • and orbital communications systems. Ben and his team plan to start with a series of orbital

  • missions, then to go interplanetary.

  • Ben imagines that his little group could take center stage in a project that space visionaries

  • have long seen as essential to the quest to extend our eyes and minds across the solar

  • system.

  • We also envision that a large cadre of these small spacecraft could form what would be

  • an initial interplanetary internet. You can think about a large number of these spacecraft

  • orbiting the earth, orbiting the moon, being spread out between earth and mars, and providing

  • little data relays between all of these positions so we can get a lot of data back and have

  • the beginnings of a real solar system internet going beyond the Earth.

  • Back in Alaska. Their latest payload has flown all night at an altitude of over 100,000 feet.

  • Then in the low air pressure, the balloon burst and the payload parachuted to the ground.

  • From GPS signals given off by the payload, they have a good idea of where it is. But

  • that doesn’t mean retrieving it will be easy.

  • Now we're right here. And see where it says Sled Road? That's the trail we're going to

  • be following down. John knows where there's a cut off that's going to take us off that

  • Sled Road over to Dune Lake. And this little pond or lake right here just to the west maybe

  • a mile north is where we believe the target is. So we're going to come down here, we're

  • going to look for the turn, head off to Dune Lake and then we're going to be off trail

  • from here all the way up to here.

  • Wow.

  • About five miles

  • Okay. Then we're going to have, both Hans and I have these GPS locater devices

  • So we've got our first payload, Aurora One, that we are going to go recover and track.

  • You see snow machines to recover. We've got two expert guides that go track these things

  • for a living. One guy is a retired military helicopter pilot. And we've got GPS units,

  • all the coordinates plugged in. We're about 26 miles from here as the crow flies. We're

  • about thirty, thirty-five miles by trail, the last five miles being really off trail

  • so we're going to have to break new trail.

  • The plan is to navigate well-worn snow trails and get within striking distance.

  • But if the payload has landed away from the trails, theyll have to brave wilderness

  • landscapes and deep snows.

  • It takes nearly all day to get to a point about seven miles from the payload.

  • Team members set out across hills and ravines.

  • They get to within two miles. With time running out, they turn around.

  • It's not going to happen today. We're going to go back, recoup, probably send a skeleton

  • team down tomorrow and try for a second recovery. Really disappointing we couldn't get there.

  • I feel like we're so close. this thing came 50 miles from the initial launch site. It

  • was floating around in the atmosphere for ten hours, and it's so frustrating to get

  • to within two miles.

  • The next day, a long hike on snowshoes finally gets them to the payload.

  • Later on theyll say it was worth the effort.

  • One of Ben’s goals is to help boost a whole new approach to space travel that’s now

  • emerging.

  • May 2012 marked a major milestone in the rise of free enterprise in space. The SpaceX Company

  • successfully docked an unmanned space capsule with the International Space Station. It followed

  • that up six months later with the first commercial resupply mission.

  • That’s just the beginning. NASA is looking to companies to supply orbital launch services,

  • and to be long-term partners in future manned missions beyond the moon.

  • Hoping to make big bucks, companies are developing orbital habitats and space planes, laying

  • the groundwork for missions geared to mining, exploration, and even tourism.

  • To Ben, this new race to space will go to the swift and the innovative.

  • Today, because of weather and winds, he and his team have chosen to launch their payload

  • from the spectacular Ruth Glacier in Denali National Park.

  • Amid the rugged terrain, this immense river of ice sweeps down into a perfect natural

  • runway.

  • The payload and frame have been preassembled. The team makes a few last-minute adjustments.

  • They inflate the balloon with helium gas.

  • With dusk approaching, balloon and payload

  • are ready.

  • Off it goes.

  • The balloon drifts up through the dense polar air.

  • With night falling, it rises up to the edge of space.

  • Meanwhile, overhead, a solar storm is raging.

  • Aboard the International Space Station, astronaut Don Pettit is making observations of northern

  • aurorae to complement what Ben’s team finds.

  • He passes over the Arctic several times during the balloon’s flight.

  • The auroras he photographs are an indicator of the amount of solar particles that will

  • pummel Ben’s rocket components.

  • This is a time of high solar activity, approaching the peak of an 11-year cycle.

  • The Arctic Circle is framed by a ring of dancing auroral lights.

  • Curtains of green and red and blue drape our planet’s graceful curve.

  • This university-based experiment operates on the remote edge of modern sciencedominated

  • by large international projects such as the Hubble Space Telescope, the International

  • Space Station or the Large Hadron Collider.

  • So this technology that we are trying to miniaturize is significant in the sense that it sort of

  • opens up new frontiers, in the same way that miniaturizing computer technology to a point

  • where it fits in your pocket. Everyone carries around a cell phone. They have these miniature

  • computers. It does a lot of data processing. It gets you to your destination by GPS. That

  • sort of technology didn't exist 20 or 30 or 40 years ago when you have these big mainframe

  • computers that were at national labs. So were trying to change the paradigm of space exploration

  • from the national lab case to the cell phone case, the miniature case, to be able to do

  • a lot more and to improve our capability as a species.

  • Working small, Ben’s team believes they are onto something big. Their goal is not

  • only to open new avenues of space exploration, but to actually seize the initiative.

  • It’s a romantic idea of individuals challenging the odds and striking out to new frontiers.

  • With technologies that are getting smaller and more powerful, the obstacles to private

  • space exploration appear to be falling.

  • Who will hold back this new breed of explorer?

Ancient people saw them as messages from the Gods, as supernatural winds that blew from

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宇宙之旅--重塑太空飛行之旅。 (Cosmic Journeys - Reinventing Space Flight)

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