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June 12, 2013

Recent breakthroughs mean we are on the cusp of Big Graphene Solar Sails for crude interstellar missions

Columbia University worked out how to remove graphene from a copper substrate without damaging it. They have large sheets of graphene with a strength of 95 gigapascals. This is fifteen times stronger than kevlar. This is 90% of the strength of perfect molecular graphene and is stronger than molecular carbon nanotubes.

There are graphene factories being setup this year and next year that will produce hundreds of tons of graphene. Some of those factories could be adapted to produce the stronger undamaged graphene.




We need solar sails at least 100 meter on a side and 400 meters on a side to get really interesting missions

Solar sail missions in the near term

Note - the 100 meter on a side graphene solar sail, 400 meter graphene solar sail or even a 1000 meter on a side solar sail would be less one ton of graphene. It is a matter of making the big sheets of it.





Beryllium and Graphene solar sail performance projections

Here is a paper by Matloff on beryllium hollow-body solar sails. An abstract of another paper by Matloff indicates that a graphene solar sail would outperform the beryllium solar sail.

Spacecraft kinematics, peak perihelion temperature and space environment effects during solar-radiation-pressure acceleration for a beryllium hollow-body interstellar solar sail inflated with hydrogen fill gas are investigated. We demonstrate that diffusion is alleviated by an on-board fill gas reserve and electrostatic pressure can be alleviated by increasing perihelion distance. For a 0.1 AU perihelion, a 937 m radius sail with a sail mass of 150 kg and a payload mass of 150 kg, perihelion sail temperature is about 1000 K, peak acceleration is about 0.6 g, and solar-system exit velocity is about 400 km/s. After sail deployments, the craft reaches the 200 AU heliopause in 2.5 years, the Sun’s inner gravitational focus at 550 AU in about 6.5 years and 2,550 AU in 30 years. The Be hollow-body sail could be applied in the post 2040 time frame to verify general relativity predictions regarding the Sun’s inner gravitational focus and to explore particles and fields in the Sun’s inner Oort Comet Cloud.

Matloff talks about getting to Alpha Centauri in 1000 years using a graphene solar sail (without laser or microwave propulsion. This is about 285,000 astronomical units (4.5 light years) and would mean exiting the solar system at a speed of about 1400 km/s with a graphene solar sail.

Solar sails have been successfully deployed in space

The Solar Photon Sail Comes of Age (in 2010)

Solar photon sailing, spacecraft propulsion by the pressure of sunlight, has long been a theoretical concept. During 2010, two successful missions - one in Earth orbit and one in deep space - demonstrated the utility of the concept and advanced its technological readiness level. This paper reviews the history of the solar sail, near term mission possibilities and possible far-future developments. Both recent missions: the NASA Earth-orbital Nanosail D2 drag sail and the Japanese JAXA Ikaros interplanetary technology demonstrator are discussed. Used with close solar flybys or solar-orbital laser power stations, the photon sail is one of our few candidates for extrasolar and interstellar propulsion. It may also have application to Earth defense from asteroid impacts and terrestrial climate control.

The light sail, which is pushed through space by momentum exchange from impacting and reflected photons, is the only suggested method of interstellar propulsion that has thus far been successfully tested in space. The solar photon sail, unfurled as close to the Sun as possible, offers the possibility of ~2,000-year duration voyages to Alpha Centauri using currently existing sail materials and departure from the present-day Sun. Improvements in sail material technology and departure from more luminous stars may greatly reduce interstellar transit time. During interstellar cruise, the sail could be wrapped around the habitat to provide cosmic ray shielding. The sail could be unfurled late in the flight to decelerate the spacecraft to planetary velocities. Collimated laser and maser beams, projected from power stations closer to the Sun than the starship, could overcome the limitations imposed by the inverse-square law and allow higher interstellar cruise velocities, if beam aim and collimation can be maintained over trillion-kilometer distances. This paper reviews progress on interstellar light sailing, discusses combination with other interstellar propulsion modes, and indicates some directions for future research.

World ships with solar sails

World Ships: The Solar-Photon Sail Option

The World Ship, a spacecraft large enough to simulate a small-scale terrestrial internal environment, may be the best feasible option to transfer members of a technological civilization between neighboring stars. Because of the projected size of these spacecraft, journey durations of ~1,000 years seem likely. One of the propulsion options for World Ships is the hyper-thin, likely space-manufactured solar-photon sail, unfurled as close to the migrating civilization's home star as possible. Because the sail and associated structure can be wound around the habitat while not in use, it represents the only known ultimately feasible interstellar propulsion system that can be applied for en route galactic-cosmic ray shielding as well as acceleration/ deceleration. This paper reviews the three suggested sail configurations that can be applied to world ship propulsion: parachute, hollow-body and hoop sails. Possible existing and advanced sail and structure materials and the predicted effects on the sail of the near-Sun space environment are reviewed.

Adaptable for other purposes inside the solar system

There has been work and will continue to be efforts to produce graphene solar sails. Graphene could enable the use of better metals for different space sail applications without increasing weight or graphene could be used for super light and high performance solar sails for interstellar missions and other applications.

Graphene in solar sail applications, specifically as a lighter weight alternative to the Mylar support. Use of graphene is expected to reduce the total weight of the solar sail by ≈90%, while also conferring superior strength, thermal conductivity, and stability to the structure.

Graphene-metal sandwich structures are prepared from bilayer graphene through metal deposition methods. Through this route, chromium/graphene/aluminum hybrid materials can be generated to serve as a potential alternative to the chromium/Mylar/aluminum structures used in conventional solar sails. Graphene is envisioned as an attractive alternative in this application due to its light weight, atomic layer thickness, and exceptional strength.

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