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.
Research:
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E Schamiloglu, “3-D Simulations Of Rigid Microwave Propelled Sails Including Spin”, Proc. Space Technology and Applications International Forum, AIP Conf. Proc. 552, 559, 2001
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Benford, J., Benford, G., Gornostaeva, O., Garate, E., Anderson, M., Prichard, A. and Harris, H. “Experimental Tests of Beam-Riding Sail Dynamics”, Proc. Space Technology and Applications International Forum (STAIF-2002), Space Exploration Technology Conf, AIP Conf. Proc. 608, ISBN 0-7354-0052-0, pg. 457, (2002).
Jan 05, 2017 02:28
Breakthrough Initiatives
Posted on: Breakthrough Initiatives
RE:
"Dec 06, 2016 08:30 michael.million@sky.com Posted on: Centauri Dreams
The 2D laser can be made very, very small
http://newscenter.lbl.gov/2015/10/20/exciting-breakthrough-in-2d-lasers/
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."
Answer:
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
Jan 05, 2017 16:02
michael.million@sky.com
Posted on: Centauri Dreams
The beauty of this miniaturisation is that it can be tested in labs without the need for great expense.
Jan 07, 2017 20:30
michael.million@sky.com
Posted on: Centauri Dreams
'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.
Jan 07, 2017 23:51
michael.million@sky.com
Posted on: Centauri Dreams
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.
http://www.nanowerk.com/spotlight/spotid=6371.php
Feb 02, 2017 18:53
Breakthrough Initiatives
Posted on: Breakthrough Initiatives
RE:
"Jan 07, 2017 23:51 michael.million@sky.com Posted on: Centauri Dreams
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.
http://www.nanowerk.com/spotlight/spotid=6371.php";
Answer:
Thank you for your consideration. This is a great idea, uncertain how it applies to the stability issue.
- Pete Klupar, Breakthrough Starshot
Mar 12, 2017 10:07
michael.million@sky.com
Posted on: Centauri Dreams
'Answer:
Thank you for your consideration. This is a great idea, uncertain how it applies to the stability issue.
- Pete Klupar, Breakthrough Starshot'
The nanotubes can be used to pull the surface into different shapes allowing attitude control and comm's dish changes.
Mar 21, 2017 18:48
Breakthrough Initiatives
Posted on: Breakthrough Initiatives
RE:
Mar 12, 2017 10:07 michael.million@sky.com Posted on: Centauri Dreams
Answer:
Thanks for your input. Yes, nanotubes maybe the enabling technologies we require.
- Pete Klupar, Breakthrough Starshot
Sep 10, 2017 03:37
jreed440@gmail.com
Posted on: Centauri Dreams
If the light sail were increasingly transparent toward the outer edges, would this not force the craft to follow the beam? for instance, if the sail were 1 foot round and the beam 1 inch.........
The theory being less thrust is imparted at the periphery and more at the center making it hard to get off beam?
maybe a precise beam would be more effective originating toward the darker side of the moon or some such?
Sep 21, 2017 20:43
Nathan Bemis
Posted on: Breakthrough Initiatives
jreed440,
I was thinking they could use the laser to control a sphere(ish?) designed craft and control it with the laser as an ice cream cone holds the ice cream. (only this cone would have full contact with its scoop), having the laser energy gradually be slightly stronger outwards from the center. A flat faced target I imagine, would require an incredible amount of calculation, programming, and perhaps luck to figure out for a reliable craft control system.
