{"id":10596,"date":"2016-12-27T16:14:04","date_gmt":"2016-12-27T08:14:04","guid":{"rendered":"http:\/\/stuif.com\/blog\/?p=10596"},"modified":"2016-12-27T16:21:25","modified_gmt":"2016-12-27T08:21:25","slug":"neighbour-here-we-come","status":"publish","type":"post","link":"https:\/\/stuif.com\/blog\/?p=10596","title":{"rendered":"Neighbour, here we come!"},"content":{"rendered":"

In a recent blog, Our nearest neighbour?<\/a> , I reported about the discovery of the planet Proxima b, orbiting around a star, “only<\/span>” 4.22 lightyear away from Earth. In several\u00a0media it was suggested that within a few decades a spaceship could be launched to reach this planet. A spaceship<\/span> is science-fiction, but there exists\u00a0an ambitious plan to send a swarm of space-chips<\/span>\u00a0to Proxima b within a few decades. I promised to write a separate blog about this\u00a0Breakthrough Starshot<\/a>\u00a0 Here it is.<\/p>\n

In 1865 the French\u00a0novelist Jules Verne wrote\u00a0De la Terre \u00e0 la Lune<\/span> (From the Earth to the Moon<\/a>), in which he describes how three adventurers travel to\u00a0the moon in a projectile, shot from the earth by a large cannon. I\u00a0have read it spellbound when I was a teenager. You can read it online here<\/a>\u00a0, it is fascinating (and hilarious too).<\/p>\n

The illustrations are beautiful. Here \u00a0are some. From left to right\u00a0the three adventurers climbing into the projectile, the comfortable interior and the firing of the canon.
\n\"verne1\"<\/a> \"verne2\"<\/a> \"verne3\"<\/a><\/p>\n

Why this introduction? We know now that this method is not used in our space age.\u00a0We don’t shoot\u00a0our spacecraft to the moon or other planets, we use rocket propulsion<\/a>. \u00a0The\u00a0 Voyager 1 (825 kg) was launched by a Titan-Centaur rocket (600.000 kg).\u00a0The images show the launch, the Voyager spacecraft and a structure diagram of the rocket. The Centaur is mounted on top of the Titan. A huge amount of fuel is needed to launch a “tiny” payload!<\/p>\n

\"Voyager<\/a><\/p>\n

\"voyager_001\"<\/a><\/p>\n

After completing its mission, the Voyager is now leaving our Solar System with a speed of more than 60.000 km\/h That is fast but it would still take about 75.000 year to reach Proxima b, if it was going in that direction (which is not the case).<\/p>\n

So we\u00a0can forget about \u00a0space travel to the stars, using rocket propulsion<\/span>, at least in the foreseeable future. Is\u00a0there another option, more in the style of Jules Verne?<\/p>\n

Actually there may be one…:-)<\/p>\n

One year ago Travis Brashears<\/a>, a graduate student at the University of Santa Barbara in California, and his supervisor, Philip Lubin<\/a>, professor of\u00a0astrophysics and cosmology at the same university, published a paper\u00a0Directed Energy Interstellar Propulsion of WaferSats<\/a>\u00a0in which powerful lasers\u00a0“shoot” miniature (~ 1 gram only!)\u00a0electronic chips away from earth in the direction of a nearby star, with a speed approaching the speed of light!\u00a0Here are the (main) writers , Brashears left and Lubin right.<\/p>\n

\"brashears-lubin\"<\/a><\/p>\n

Does this sound as science fiction? For me it does.\u00a0But apparently not for\u00a0these guys.<\/p>\n

Sure, light exerts pressure, there are several projects going on, using sunlight propelling a solar sail<\/a>\u00a0, a bit similar\u00a0to the\u00a0sail of a sailing boat being blown by the wind. One successful project is IKAROS<\/a>, a solar sail of 196\u00a0m2\u00a0<\/sup>\u00a0(!) , launched in 2010 by Japan. Here an artist impression of the sail, with Venus, its destination. The sail is so big. because the thrust of the sunlight is only small.<\/p>\n

\"Ikaros\"<\/a><\/p>\n

Next year March the LightSail 2<\/a> will be launched. To the left the actual spacecraft, a so-called cubesat<\/a>. To the right an artist impression of the LightSail in space, with a deployed sail. Notice how small the cubesat is compared to the sail!<\/p>\n

\"lightsail-table-002\"<\/a><\/p>\n

\"lightsail1_space\"<\/a><\/p>\n

These projects are using sunlight. The project of Brashears and Lubin is futuristiic.<\/p>\n

    \n
  1. A ground-based laser will be used as a “shotgun” \u00a0Estimated power needed 100 GW. That is a lot! The Three Gorges Dam<\/a> in China, the largest power plant in the world, generates 22.5 GW.<\/li>\n
  2. The spacecraft will be a chip with a mass of about 1 gram, with a light sail of ~ \u00a01\u00a0m2 \u00a0<\/sup> . The plan is to prepare about 1000 of these miniature “spacechips” and launch them simultaneously in a mothership, orbiting the earth. From there the starchips will be shot, one after another on a daily basis, during 3 year.<\/li>\n
  3. The laser will give a\u00a0spacechip in about 10 minutes a speed of 20% of the speed of light. That is fast , 60.000 km\/s<\/li>\n
  4. The spacechips will reach Proxima b in about 20 year. Hopefully at least a few of them will have survived the journey.<\/li>\n
  5. They will send back pictures to earth.<\/li>\n
  6. Estimated cost of the project US$ 5-10 billion.<\/li>\n
  7. Proposed launch date about 20-30 years from now.<\/li>\n<\/ol>\n

    Here is an artist impression of the launch. Mind you, the spacechip is the tiny dot in the center of the light sail!<\/p>\n

    \"lightsail-starchip\"<\/a><\/p>\n

    Futuristic indeed. The time span of 20-30 year is because much\u00a0of the technology still has to be developed. Designing\u00a0a spacecraft on a\u00a0centimeter-size, gram-scale chip, developing\u00a0a light sail with a thickness of 1 micron or less, building a 100 GW laser and many more challenges.<\/p>\n

    Here another artist impression.\u00a0The plan is to build a so-called “phased” \u00a0array of smaller lasers, with a combined power of 100 GW. If you use 100 kW lasers (\u00a0at the moment the maximum power available), you need a staggering 1 million of them.<\/p>\n

    \"Laser<\/a><\/p>\n

    I am skeptic, as usual…:-) But not everybody is. Yuri Milner, for example is optimistic. \u00a0This Russian\/American tech entrepreneur and multi-billionaire, \u00a0started as a physicist and is very interested in the big question “Are we alone in the universe<\/a>“. In July 2015 he announced, together with the\u00a0British physicist Stephen Hawking, the\u00a0Breakthrough Initiatives<\/a>\u00a0, a program\u00a0to search for extraterrestrial intelligence. At that time the program consisted of two parts.<\/p>\n

      \n
    1. Breakthrough Listen<\/a>. \u00a0Basically a large-scale version of the SETI<\/a> project. Funded by Milner with US$100 million.<\/li>\n
    2. Breakthrough Message<\/a>.\u00a0A prize pool of 1\u00a0US$ 1 million for the best (digital) messages that could be sent out into deep space. No concrete plan to actually send these messages,\u00a0because for example Hawking thinks it might not be advisable to do that. See my blog Anybody Out There?<\/a><\/li>\n<\/ol>\n

      In April\u00a02016, part 3, \u00a0Breakthrough Starshot, <\/a>was announced by Milner and Hawking.\u00a0Milner and Mark Zuckerberg (FaceBook) will contribute another US$ 100 million to explore the technological feasibility of the program outlined above.<\/p>\n

      \"Milner,<\/a><\/p>\n

      From left to right Yuri Milner (holding a protoype of a spacechip in his hand), Stephen Hawking and “eminence grise” Freeman Dyson, a physicist and cosmologist, now 93 year old. If you are interested in really futuristic ideas, have a look at his Dyson Sphere<\/a> \ud83d\ude42<\/p>\n

      Below\u00a0is an animation of the process. A few comments may be useful.<\/p>\n

        \n
      1. There are\u00a0135 lasers in the array. You need at least 1 million.<\/li>\n
      2. The spacechips are launched simultaneously in a container, but released and shot one after another.<\/li>\n
      3. When they reach Proxima b\u00a0after ~ 20 years, they will pass the planet\u00a0at full speed (60.000 km\/s). So fast that the\u00a0camera on board\u00a0can only\u00a0take a few pictures. Also data will be collected about magnetic fields etc.<\/li>\n
      4. These data\u00a0will be sent back to earth, using miniature lasers on the spacechip, focused with the help of the light-sail.<\/li>\n
      5. \u00a0About 4.22 year\u00a0later, the ground-based laser array will receive\u00a0these data. Hopefully…:-)<\/li>\n<\/ol>\n