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Destination Tomorrow - DT11 - SpaceSails

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Subido el 28 de mayo de 2007 por EducaMadrid

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NASA Destination Tomorrow Segment explaining how solar pressure-powered sails may one day be used to propel spacecraft deep into space.

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Throughout humankind's early history, the quest for greater knowledge and understanding 00:00:00
fueled the need for exploration. 00:00:09
For centuries, the vehicle most early explorers used to achieve this exploration was a ship 00:00:11
with sails. 00:00:16
But because these ships depended on wind pushing against the sails for forward motion, they 00:00:18
were generally very slow, unpredictable, and often very dangerous. 00:00:23
Today, with the multitude of ways that humans now possess to travel, the sail, with all 00:00:27
of its limitations, has been relegated to recreational status rather than a serious 00:00:32
tool for exploration. 00:00:38
But a new idea might change the way we think about sails. 00:00:40
NASA researchers are actually developing a new type of sail that will use the sun's light 00:00:43
to propel spacecraft deep into space. 00:00:48
These solar sails are so promising that someday they may replace slower, more costly propulsion 00:00:51
systems for deep space exploration. 00:00:56
I spoke with Dr. Keith Belvin at NASA Langley Research Center to find out more. 00:00:59
The idea for solar sails has been around for a very long time. 00:01:04
Maxwell, back in 1873, predicted the existence of solar pressure lights. 00:01:07
So we've known about solar pressure for a long time. 00:01:12
But it wasn't until recently that we were able to build solar sails with the lightweight 00:01:16
materials and structures that are needed. 00:01:20
Tell me about these lightweight materials and structures. 00:01:22
How are they being used? 00:01:24
Well, the key to building a solar sail is, of course, to make it very large and very 00:01:26
lightweight. 00:01:30
For a useful solar sail, it has to have a weight of less than 10 grams per square meter. 00:01:31
For example, copier paper has a weight of 70 grams per square meter. 00:01:38
So we're talking about some materials that are much lighter than that. 00:01:42
One of the things that NASA's done over the last decade is to work on materials that can 00:01:46
be processed to just a couple microns. 00:01:50
That's a couple millionths of a meter thick. 00:01:53
And these lightweight, thin materials then are made space-durable so they can withstand 00:01:56
the radiation and temperatures of space. 00:02:01
Dr. Belvin, tell me how a solar sail works. 00:02:04
The basic principle is much like a ship on the sea that uses sails to capture the wind. 00:02:07
The sun is constantly emitting light, or photons, in all directions. 00:02:12
Since the photons have mass and are in motion, their momentum produces a pressure when reflected 00:02:17
by a surface. 00:02:22
When a spacecraft uses a solar sail for propulsion, the sail's reflective surface transfers a 00:02:23
continuous force from the photons to propel the craft through space, much like a sailing 00:02:30
ship uses wind to push it across the water. 00:02:35
Since the pressure being emitted from the photons is very low, the force is small. 00:02:39
And because the sail will have a constant source of energy, it is continuously accelerating 00:02:43
and can reach speeds upwards of 155,000 miles per hour. 00:02:49
This speed could cut years off travel time during long-duration interstellar flights. 00:02:53
In addition, the constant propulsive force provided by the sun's light allows the spacecraft 00:02:59
to travel in orbits that are not affordable using conventional propulsion. 00:03:04
So can solar sails be used on all types of missions? 00:03:08
Well, in addition to solar sails having to be lightweight for various missions, the spacecraft 00:03:11
they're propelling has to be very lightweight. 00:03:17
But there are many missions where, with the miniaturization of electronics, that the spacecraft's 00:03:19
science sensors are very small and lightweight. 00:03:24
And those systems are very amenable to being propelled by a solar sail. 00:03:27
For example, we're looking at missions in the future where we do interstellar transfer 00:03:32
of science instruments using solar sails. 00:03:37
So do we see solar sails only being used in deep space? 00:03:40
Well, there are missions where solar sails can be used close to the Earth's orbit. 00:03:44
They don't all have to be long-duration, interstellar-type missions. 00:03:50
The constant acceleration that a solar sail produces gives it an orbit trajectory that 00:03:54
is not achievable by some other means. 00:03:59
For example, we can fly a science payload to measure the magnetic storms emanating from 00:04:02
the sun. 00:04:09
How do you deploy such a large structure into space? 00:04:10
To deploy a solar sail in space is quite a challenge. 00:04:13
First of all, the sail has to be packaged in a small size to fit into the launch vehicles. 00:04:16
Near-term sail missions are on the order of 70 meters to up to 150 meters in size. 00:04:22
And so it's a real challenge to package those tightly and then deploy in space. 00:04:27
Two aspects probably are most important for deploying a solar sail. 00:04:32
The first is deploying the booms that hold the membranes in place. 00:04:36
We're using inflation to push the booms out and to the right location. 00:04:40
And then we cool the booms to rigidize them. 00:04:46
The second aspect is deploying the sail, the thin-film membranes that we've talked about. 00:04:48
Those will incorporate ripstop so that if there's a small tear, it doesn't propagate 00:04:54
very far. 00:04:58
In addition, we have to deploy those so that we don't affect the sail's reflective performance. 00:04:59
And so special measures are taken to maintain the integrity of that sail. 00:05:04
What is the future of this program? 00:05:09
I would say within the next dozen years or so, solar sails will be used routinely to 00:05:10
propel spacecraft. 00:05:15
Continual improvements in the sail technology will allow them to be used for extreme environments 00:05:17
like near-sun missions. 00:05:22
Over the next 20 years, most importantly, we'll have the technology in hand to do interstellar 00:05:24
missions. 00:05:29
These are kilometer-sized solar sails that weigh only one to two grams per square meter. 00:05:30
The technology being developed today at NASA is going to enable us to unlock a lot of the 00:05:35
secrets of the universe. 00:05:40
Not only will we be able to look at distant places using telescopes, we'll actually be 00:05:42
able to send science instruments to some of those locations using solar sails. 00:05:47
Did you know that the inspiration for solar sail technology came from the 17th century 00:05:53
astronomer Johannes Kepler? 00:05:57
Kepler deduced that winds blew objects around in space after he observed comet tails blown 00:05:59
by what appeared to be a solar breeze. 00:06:03
Kepler suggested that eventually ships might navigate through space using sails that could 00:06:06
catch this wind. 00:06:10
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Idioma/s:
en
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Autor/es:
NASA LaRC Office of Education
Subido por:
EducaMadrid
Licencia:
Reconocimiento - No comercial - Sin obra derivada
Visualizaciones:
645
Fecha:
28 de mayo de 2007 - 17:05
Visibilidad:
Público
Enlace Relacionado:
NASAs center for distance learning
Duración:
06′ 13″
Relación de aspecto:
4:3 Hasta 2009 fue el estándar utilizado en la televisión PAL; muchas pantallas de ordenador y televisores usan este estándar, erróneamente llamado cuadrado, cuando en la realidad es rectangular o wide.
Resolución:
480x360 píxeles
Tamaño:
36.25 MBytes

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