Lightsail | Stability on the beam

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. Because of this requirement, very small differences in the properties of the sail, or beam non-uniformities, will shift the center of pressure from the center of mass of the sail and so offset the sail thrust vector.

Because of this, the sail properties and beam properties must be controlled to high precision. These properties include: composition, density, reflectivity, and absorptivity. By modulating the beam modes, get greater uniformity could be attained, and feedback between the nanocrafts and the beamer array would allow real-time adjustments.

Currently, the optics coating industry achieves the required level of control on mass-produced items, with Angstrom-thick tolerance on common items such as cell phones and telescope optics. These manufacturing procedures and approaches are already mature, but the actual sail material is currently not available and will have to be developed. Mitigating approaches also include beam shaping and spinning of the sail to average out slight sail imperfections in its properties.


Comments (25)


    We could incorporate these MEM's gyroscopes into the design to keep the sail orientated correctly and allowing for on-sail active control.

  2. Breakthrough Initiatives:

    "Dec 06, 2016 08:30 Posted on: Centauri Dreams
    The 2D laser can be made very, very small
    If we use pyramids taking advantage of the total internal reflection principle we could reduce the mass down quite a bit, the material between the pyramids can be a polymer to aid flexibility, lower weight and can be coated with a reflective metal to act as a telescope with a high surface area. With the light sensitive control sensors they can distributed around the sail surface and locally electrical connected to a nest of reflectivity/transparency control pyramids (truncated) which would minimise weight."

    Thank you for your help in this matter. It is not clear that a pyramid shape is a stable shape or meets the needs of the material requirements.

    - Pete Klupar, Breakthrough Starshot


    The beauty of this miniaturisation is that it can be tested in labs without the need for great expense.


    'Thank you for your help in this matter. It is not clear that a pyramid shape is a stable shape or meets the needs of the material requirements.'

    Pyramids offer total internal reflection benefits and lower mass than say a 40 layer dielectric mirror for the same thickness, the pyramids can also be stabilised by having 'diamond' CVD bridges upon which nanotube 'perhaps capillary metal filled' can be used for electrical communications. Although the nanotubes themselves could add to the stiffening of the structure.


    What is interesting is using this capillary action to join nanotubes together, we could make much larger nanotubes to string our device together and use it for circuitry. If we had two nanotubes touching the metal/material bead and it is then heated to melting point both nanotubes will pull the material into their tubes and bring the nanotubes very close together. If a catalyst material is used or it may even be hot enough they will join together to form a longer nanotube which would make a great building material.

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