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Views of IKAROS (and a Memory)

This is what a solar sail looks like in space. The images below were taken by a camera flown aboard the IKAROS mission and then separated from it using a spring, according to the Japan Aerospace Exploration Agency (JAXA).

These pictures (and you can find several more here) take me back to my first reading of Cordwainer Smith’s ‘The Lady Who Sailed the Soul,’ in which a far future sail mission involving a sail tens of thousands of kilometers across plays against the tangled relationship of two lives (full text here). IKAROS may be far smaller, but if seeing a deployed sail in space doesn’t fire the imagination, what will? A brief snippet from the story:

The first sailors had gone out almost a hundred years before. They had started with small sails not over two thousand miles square. Gradually the size of the sails increased. The technique of adiabatic packing and the carrying of passengers in individual pods reduced the damage done to the human cargo. It was great news when a sailor returned to Earth, a man born and reared under the light of another star. He was a man who had spent a month of agony and pain, bringing a few sleep-frozen settlers, guiding the immense light-pushed sailing craft which had managed the trip through the great interstellar deeps in an objective time-period of forty years.

“The Lady Who Sailed the Soul” was published in Galaxy‘s April, 1960 issue, and still has a prized place on my shelf, along with all the other Galaxy issues of that era. If you haven’t yet made the acquaintance of Cordwainer Smith (Paul Linebarger), I envy you. Not only did he lead an unusual life (scholar, diplomat, spy and successful author), but the images he created with his words offer up a far future that is at once alien and deeply human. I wish he could have seen these pictures.

IKAROS will now be used to measure the effect of photon pressure from the Sun even as the spacecraft team examines the effectiveness of the thin film solar cells built into the sail. Just how navigable will IKAROS turn out to be, and how much can it teach us about future sail deployment and operations? We learn more day by day as this extraordinary mission continues.

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  • Edg Duveyoung June 16, 2010, 9:57

    As an aside, I ask: if light can push on sails, why isn’t it the case that the universe is internally pressurized thusly such that the expansion of the universe is at least partially accounted for? Is “light pressure” anything like “dark energy?” How much bigger would a star be if there were no radiation pressure upon it from the surrounding universe? Is background radiation left over from the big bang actually a measuring of this pressure?

  • Rose Weisburd June 16, 2010, 10:23

    Cordwainer Smith’s exploration around the edges of what it means to be a person amidst technological and social upheaval stands the test of the ages.

  • James M. Essig June 16, 2010, 13:55

    Hi Paul;

    Thanks for the personal account of reading “Cordwainer Smith’s ‘The Lady Who Sailed the Soul”. My mother who does not a have a technical background was completely captivated by the solar sail concept as she read a Planetary Society article on Light Sail 1, and she was obviously very enthusiastic as I described to her the basic principles behind light sails in the context of IKAROS.

    For an extreme value of M0/A = [0.8 x (10 EXP −8)] kg/(meter EXP 2) for a solar dive and fry sailand an approach of 0.03 AU, ,the terminal velocity = 0.251 C. This could get us to Alpha Centauri in 16 years and to Barnard’s Star in about 24 years. We could send humans out to every one of the 33 stars within a 12.5 light year radius of Earth in under 60 years transit time.

    Regarding practical sail capture areas, I thought that the reader would appreciate the following brief summary.

    An M0/A = [2 x (10 EXP – 5)] kg/(meter EXP 2) could conceivably be achieved for monolithic sails made of 10 nanometer thick metalized Boron Nitride Nanotube material or Carbon Nanotube materials in the form of a weave or a knit with ion beam deposition, or chemical vapor deposition of highly refractive elements.

    An M0/A = [2 x (10 EXP – 4)] kg/(meter EXP 2) could conceivably be achieved by similar means except now the sheet would be 100 nanometers thick. Here, we assume that the effective volumetric density of the sail is roughly twice that of water at STP.

    An M0/A = [2 x (10 EXP – 6)] kg/(meter EXP 2) might be achieved for a sail composed of a cross weave of 10 nanometer wide Boron Nitride Nanotubes or Carbon Nanotubes that are metalized and where parallel fibers are separated by 200 nanometers.

    An M0/A = [2 x (10 EXP – 7)] kg/(meter EXP 2) might be achieved for a sail composed of a metalized sheet of graphene which is a one atom thick membrane made of carbon atoms.

    An M0/A = [0.8 x (10 EXP – 8)] kg/(meter EXP 2) might be achievable by a cross weave of 8 nanometer wide metalized graphene strips, where parallel strips are separated by 160 nanometers.

    A 10,000 metric ton space craft that has a payload mass of 1,000 metric tons and a sail with an M0/A = [2 x (10 EXP – 4)] kg/(meter EXP 2) would have a capture area of about {[2 x (10 EXP – 4)] – 1}(10 EXP 3)(10 EXP 4) = [5 x (10 EXP 10)] square meters = 50,000 square kilometers. This is a reasonable 250 kilometers by 200 kilometers.

    A 10,000 metric ton space craft that has a payload mass of 1,000 metric tons and a sail with an M0/A = [2 x (10 EXP – 5)] kg/(meter EXP 2) would have a capture area of about {[2 x (10 EXP – 5)] – 1}(10 EXP 3)(10 EXP 4) = [5 x (10 EXP 11)] square meters = 500,000 square kilometers. This is a reasonable approximately 700 kilometers by 700 kilometers.

    A 10,000 metric ton space craft that has a payload mass of 1,000 metric tons and a sail with an M0/A = [2 x (10 EXP – 6)] kg/(meter EXP 2) would have a capture area of about {[2 x (10 EXP – 6)] – 1}(10 EXP 3)(10 EXP 4) = [5 x (10 EXP 12)] square meters = 5,000,000 square kilometers. This is a reasonable approximately 2,500 kilometers by 2,000 kilometers.

    A 10,000 metric ton space craft that has a payload mass of 1,000 metric tons and a sail with an M0/A = [2 x (10 EXP – 7)] kg/(meter EXP 2) would have a capture area of about {[2 x (10 EXP – 7)] – 1}(10 EXP 3)(10 EXP 4) = [5 x (10 EXP 11)] square meters = 50,000,000 square kilometers. This is a reasonable approximately 7,000 kilometers by 7,000 kilometers.

    A 10,000 metric ton space craft that has a payload mass of 1,000 metric tons and a sail with an M0/A = [0.8 x (10 EXP – 8)] kg/(meter EXP 2) would have a capture area of about {[0.8 x (10 EXP – 8)] – 1}(10 EXP 3)(10 EXP 4) = [5 x (10 EXP 11)] square meters = 750,000,000 square kilometers. This is a large but still plausible approximately 75,000 kilometers by 10,000 kilometers.

    Obviously, the larger sails would not handle as high of accelerational loading as the smaller more dense sails due to the need for the sails to incorporate tethers which can snap under their own puling force imposed by the payload and the mass of the cable tethers.

    However, it is instrumental to note that we have macroscopic systems of every day size that can handle 100,000 Earth Gs. This are high velocity hunting or combat rifle bullets that accelerate to velocities on the order of 1,000 meters per second in about 1 millisecond to yield an average acceleration down the rifle barrel of roughly 1,000,000 meters/(second EXP 2). At this rate, a velocity of a better part of the speed of light would be reached in about 5 minutes. A system accelerating at 10,000 Earth G’s will reach a better part of C in about 50 minutes, and a system accelerating at 1,000 Earth G’s will reach a better part of C in about 500 minutes or about 8 hours.

    Perhaps the crew member’s bodies could be encased in hydrostatically sealed breathable liquid containing vessels with an optional mechanism to magnetize and/or electrically charge the crew members bodies wherein a magnetic field or an electric field would then be used to cancel out the G-force loading. Frogs and rodents have been safely suspended in mid air by intense magnetic fields that induce a dipole moment within the atomic and molecular constituents of the animal’s bodies whereby the bodies then become magnetized.

    The exiting velocity of the solar dive and fry sail can very closely approach C, if a Stellar Cycler, dive and fry, iterative process was ussed and several to numerous cycles were performed and this says nothing about the potential for inertial rest mass reduction technologies such as including negative mass in the sail and/or space craft composition or perhaps by using Higg’s field density reduction technologies. Also, the rest mass specific, energy capture area can be greatly increased for net like sails at exiting speed close to C, wherein the grid spacing can increase in proportion to the redsjift factor of Z.

  • Gregory Benford June 17, 2010, 12:32

    James Essig is right about getting high velocities with a “solar dive and fry sail” — also known as a sundiver. But at 0.03 AU there will be many torques from solar plasma, as well, and the heating problem is immense. Some flight control may deal with the torques but the heating requires even better materials than his cases. JPL studied high temperatures, but in an oven, so radiation was isotropic. This doesn’t matter much for really thin films, but the pressure and torques are one-sided, usually. Flying a sundiver will be an art and a science.

  • Rick York June 17, 2010, 15:13

    Didn’t Larry Niven’s Ptaavs use a solar sail to reach our solar system.

    Cordwainer Smith was a miraculous discovery for me. Anyone who has not read him should.

    Though I’ve not done much myself isn’t planet bound sailing both an art and a science.

  • James M. Essig June 17, 2010, 17:17

    Hi Gregory Benford;

    Interesting points.

    Also, I wonder if CNTs, BNNTs, Diamond Fiber, Graphene and the like materials could be formed into refractory materials with extreme reflectivity such as with very smooth depositions of Tantalum Carbide, Tantalum hafnium carbide (Ta 4 HfC 5) with a melting point of 4,488 K (4,215 °C, 7,619 °F), and Tungsten with a melting point of 3695 K, 3422 °C, 6192 °F.

    Now if we can just get Carbon to form much stronger bonds than it does in Diamond, this would be a great thing. The possibility of forming diamond that is considerably harder and therefore having stronger atomic bondings then natural diamond was one of the subjects of a popularization book on the subject of Nanotechnology I read back in the 1980s. To the best of my knowledge, it was one of the first such books to appear in the book store and on public library shelves.

    We will have to wait to see what the materials science and solid state physics geeks come up with, but I remain hopefull in this regards, especially given the growing field of nanotechnology and self assembly.

  • Jon July 13, 2010, 12:39

    Can anyone tell me the mass of Ikaros in Space. Everyone lists the mass on earth but was wondering if anyone knows the mass of the object in space….or is it the same?

    I think it is the same because mass is constant and weight changes based on gravity….is that correct?