viernes, 16 de junio de 2017

Mensajes amables de fin de semana: el láser y las velas que necesita Starshot para impulsar las naves interestelares al 20% de la velocidad de la luz



Estimad@s Clientes y/o amantes del LEAN:

Reconozco que este tema me ha apasionado, por lo que le voy a dedicar un segundo post, relacionado solamente con dos de los apasionantes retos técnicos a los que se enfrentará el Equipo de Breakthrough Starshot:
-El láser que impulsará las naves hasta alcanzar un 20% de la velocidad de la luz
-Las velas solares

El contenido de este escrito está sacado de la revista Investigación y Ciencia, en su número de Mayo 2017





Un láser de 100 Gigavatios

La forma de alcanzar una fracción considerable de la velocidad de la luz es empleando un láser 100 Gigavatios, potencia nada usual  
El Departamento de Defensa de EEUU ha fabricado láseres más potentes, pero solo se activaron durante billonésimas de segundo
Sin embargo, el láser de Starshot tendrá que actuar sobre cada vela durante varios minutos
Para alcanzar semejante potencia durante tanto tiempo, una batería de pequeños láseres de fibra óptica combinaría los rayos en un único haz coherente 
El Departamento de Defensa también ha construido baterías de láseres en fase, pero con 21 láseres agrupados en una red de no más de 20 cm de lado. Eso permite alcanzar unas docenas de kilovatios
Starshot tendría que incorporar 100 millones de estos láseres con potencias de kilovatios y disponerlos en una red cuadrada de 1 km de lado

Velas que soporten aceleraciones de hasta 60.000 g
Los Starchips estarían propulsados por la luz que incidiese y se reflejase en sus velas
Cuanta más luz se refleje, mayor será el impulso y más rápido avanzará la vela
Para alcanzar el 20% de la velocidad de la luz, la vela debería reflejar el 99,999% de la luz incidente
Las velas deberían ser enormemente ligeras, con un espesor de pocos átomos
En el ensayo más parecido efectuado hasta ahora, se empleó un haz de microondas para acelerar hasta 13 g una vela fabricada con una lámina de carbono
Sin embargo, la vela de Starshot tendrá que soportar aceleraciones de hasta 60.000 g
Y al igual que el StartChip, también tendrá que resistir el polvo interestelar: Hoy por hoy, no existe un material que sea a la vez ligero, fuerte, reflectante, resistente al calor y que no cueste millones de dólares
    
¿Cuán lejos queda eso de la tecnología actual?..........apasionante ….¿no?


(Mi escrito anterior)

La revista Investigación y Ciencia del mes de Mayo recoge en portada que una serie de científicos de prestigio, entre los que se encuentra Stephen Hawking ( el famoso astrofísico británico en silla de ruedas ) está trabajando en serio para explorar los problemas técnicos a los que se enfrentaría el reto de mandar una misión a Alfa Centauri, el sistema solar más cercano al Sol
El plan está financiado por un multimillonario, Yuri Milner
El Proyecto se llama “Breakthrough Starshot”, y pretende usar láseres para acelerar una flota de microchips al 20% de la velocidad de la luz
Los retos técnicos son inmensos, pero como dice Philip Lubin, físico de la Universidad de Californiaaa en Santa Bárbara, que escribió el artículo base del inicio de los trabajos, titulado “Hoja de ruta para un viaje interestelar”: Puedo explicarle por qué es difícil y por qué es caro, pero no por qué es imposible
Básicamente, se trataría de usar láseres para acelerar una flota de microchips al 20% de la velocidad de la luz; las naves tardarían 20 años en llegar. Una vez allí, captarían imágenes y tomarían datos que tardarían 4,3 años en llegar ( los años luz a los que se encuentra Alfa Centauri de la Tierra )
En líneas más abajo, adjunto los links más interesantes que he visto por ahí

Breakthrough starshot



                                          https://breakthroughinitiatives.org/Initiative/3


Challenges

Sub-gram scale 1W diode lasers are currently widely available at very low costs. The manufacturing trend has seen power double for the same mass every two years. It is anticipated this trend will continue for these devices for some time. More...
Comments: 51. Last comment by morekenlouise@yahoo.co.jp – Apr 10, 2017 08:29.
Sub-gram-scale 2 megapixel cameras are currently widely available at very low costs. The trend has been a doubling of pixels for the same mass every two years. More...
Comments: 17. Last comment by michael.million@sky.com – Apr 29, 2017 10:34.
Sub-gram scale microprocessors are currently widely available at very low costs. The trend has been a doubling of processor count for the same mass every two years. It is anticipated that these devices will continue this trend for some time. More...
Comments: 21. Last comment by Robert Clark – Jun 06, 2017 02:56.
Battery design is one of the most challenging aspects of the mission. Currently under consideration for the energy source onboard are plutonium-238, which is in common use, or Americium-241. 150mg has been allocated for the mass of the battery. This includes the mass of the radioisotope and the ultra-capacitor. More...
Comments: 34. Last comment by michael.million@sky.com – Apr 29, 2017 07:45.
The power available needs to be balanced with the tasks that need to be completed on the nanocrafts. The radioisotope power sources establish the power budget in the most conservative design. More...
Comments: 9. Last comment by Breakthrough Initiatives – Mar 21, 2017 18:46.
A protective coating is required for the dust collisions and the erosions caused by atomic particles in the interstellar medium. More...
Comments: 26. Last comment by Breakthrough Initiatives – Jan 05, 2017 02:18.
To inform the study, a beamer in the 100 GW class was considered. If, for example, 10-5 of the energy is absorbed by a 4mx4m sail, it will be heated by about 60kW per m2, which is roughly 60 times more than sunlight illumination on Earth. This will heat the material but not melt it. More...
Comments: 57. Last comment by Breakthrough Initiatives – Apr 04, 2017 22:41.
Building a skeleton structure that will be able to hold the sail in shape during launch, be resilient to the interaction with the interstellar medium and potentially be able to modify the shape of the sail, is a major challenge given the gram-scale mass constraint. More...
Comments: 29. Last comment by michael.million@sky.com – Apr 29, 2017 10:36.
Beam shape and lightsail structure should be optimized for stability during the launch phase. In this period, on the order of 10 minutes, an illumination energy of order 1TJ is delivered to the sail. More...
Comments: 28. Last comment by Breakthrough Initiatives – Mar 21, 2017 18:48.
The estimated cost of the laser array is based on extrapolation from the past two decades, and the prospects of mass production to reduce the associated cost. More...
Comments: 35. Last comment by michael.million@sky.com – Apr 22, 2017 20:18.
In order to test the feasibility of the system, the case of a meter-scale sail was examined. For example, to focus the light beam on a 4mX4m sail across an acceleration distance of 2x106 km requires a focusing angle of 2 nano-radians (0.4 milliarcseconds), which is the diffraction limit for a kilometer-scale light beamer operating at a wavelength of 1 micron. More...
Comments: 30. Last comment by michael.million@sky.com – Apr 11, 2017 09:14.
The atmosphere introduces two effects: absorption (or ‘reduction of transmission from unity’), and loss of beam quality (or ‘blurring of the beam spot’). The transmission of the atmosphere at a wavelength of 1 micron is extremely good, exceeding 90% at high altitude ground-based sites. More...
Comments: 35. Last comment by moh kranis – Apr 29, 2017 09:55.
Power generation and storage at the launch site is challenge. Developing a site with adequate infrastructure to generate the energy at a high altitude site is difficult. More...
Comments: 42. Last comment by Robert Clark – Jun 06, 2017 03:22.
The light beamer must focus a spot smaller than the sail onto the sail, as it orbits 60,000km above the Earth’s surface. More...
Comments: 12. Last comment by khokolateKke@gmail.com – Jun 06, 2017 23:54.
There are a number of effects that make this task difficult. These include beam instabilities, laser mode issues, differential forces on the sail, differential heating of the sail, and instabilities in the atmosphere induced by the energy of the beam. More...
Comments: 21. Last comment by Nathan Bemis – Apr 22, 2017 17:54.
In order to bring a nanocraft to within 1AU of a planet in a system like Alpha Centauri, accurate locations of all the bodies near the path of flight would be required. More...
Comments: 6. Last comment by Breakthrough Initiatives – Nov 05, 2016 03:32.
The most challenging element in terms of cooling the laser array system would be the small optical instruments in front of the primary mirror. This would be addressed with conventional cooling systems and possibly by cooling the beam director assemblies (lens assemblies). More...
Comments: 8. Last comment by Breakthrough Initiatives – Feb 28, 2017 11:05.
The radiative flux on an object such as a bird, airplane, or spacecraft moving through the beam would be about the same as the output energy flux at the beamer, or 100 kw/m2 – about two orders of magnitude above sunlight on Earth. More...
Comments: 6. Last comment by Peter Jaquiery – Apr 20, 2017 03:30.
Space debris is a serious challenge, both for detection and mitigation. More...
Comments: 3. Last comment by Peter Jaquiery – Apr 20, 2017 03:28.
Breakthrough Starshot has no intention of colliding any nanocraft with any object in space. Even though an accidental collision between a nanocraft and another object is a remote possibility happens, the resulting effects must still to be examined. More...
Comments: 13. Last comment by Breakthrough Initiatives – Nov 05, 2016 04:31.
Based on estimates of the density of dust in the local interstellar medium, over the course of a journey to Alpha Centauri each square centimeter of the frontal cross-sectional area of the StarChip and lightsail would encounter about 1,000 impacts from dust particles of size 0.1 micron and larger. However, there is only a 10% probability of a collision with a 1 micron particle, and a negligible probability of impact with much larger particles. More...
Comments: 30. Last comment by Stuart Heinrich – Apr 10, 2017 16:14.
Since the trajectory to Alpha Centauri would take the nanocrafts away from the ecliptic plane of the solar system, there would be much less impact from solar system dust than from interstellar dust. Little is currently known about the dust content in the Alpha Centauri star system. More...
Comments: 6. Last comment by Breakthrough Initiatives – Dec 06, 2016 18:31.
The mean free path and Larmor radius of interstellar plasma particles is far greater than the size of the nanocraft, meaning that they would impact the nanocraft walls independently rather than forming a bow shock. More...
Comments: 12. Last comment by Breakthrough Initiatives – Aug 01, 2016 14:55.
The voyage from earth to our nearest neighbor, at up to 20% of the speed of light, takes about 20 years. Maintaining the functioning of a sophisticated nanocraft through the rigors of deep space over this time is a challenging task. More...
Comments: 2. Last comment by Breakthrough Initiatives – Aug 01, 2016 14:58.
During an encounter with an exoplanet, the nanocraft’s camera would need to rotate in order to image the target. More...
Comments: 14. Last comment by Robert Clark – Jun 06, 2017 12:53.
Finding the Earth should be reasonably straightforward, given its proximity to the Sun, which would be bright from the vantage of Alpha Centauri. The on-board star tracker would also be useful, as would locking onto the Starshot laser system. More...
Comments: 28. Last comment by Simon Dawson – Apr 13, 2017 02:12.
Images of the target planet could be transmitted by a 1Watt laser onboard the nanocraft, in a ‘burst mode’ which uses the energy storage unit to rapidly draw power for the power-intensive laser communications mode. Upon approach to the target, the sail would be used to focus the laser communication signal. More...
Comments: 35. Last comment by Breakthrough Initiatives – Mar 21, 2017 19:02.
Recent advances by groups at MIL Lincoln Labs and the Jet Propulsion Laboratory have demonstrated that it is possible to detect single photons emitted by lasers from very large distances. More...
Comments: 18. Last comment by Breakthrough Initiatives – Mar 21, 2017 19:03.
Clearance for launches will be required from all the appropriate government and international organizations. More...
Comments: 18. Last comment by Breakthrough Initiatives – Feb 02, 2017 19:02.


Videoclip de animación








Que disfrutéis cada hora del fin de semana
Un cordial saludo
Alvaro Ballesteros       




No hay comentarios:

Publicar un comentario