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Thread: Solar sail type structures

  1. #1
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    Solar sail type structures

    Hey all, aquestion has just occured to me, and I wonder if anyone here knows much about it: Could a large and lightweight communicationa antenna for a spacecraft be built using the same approach as a solar sail? I was reading upon JAXA's IKAROS mission and wondered what other applications the technology might have.
    In space PR and Politics are as important as engineering and science. And no-one can hear you screaming about it.

    "There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy."

    Exploring other worlds with people is a great idea, but look at what has happened since the end of Apollo: How much could unmanned exploration (and astronomy) have discovered with all that money blown on paper rockets?

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    Sure. Mylar was used on the Echo satellites for passive microwave reflection and experienced solar sail effects, so the idea's not incompatible with reality. This assumes you're using frequencies suitable for use with mylar or kapton. (A sail made out of meta-materials on the other hand...) The only issue would be figuring out how to maintain the proper geometry for a reflector dish when you want to transform it to that purpose. Or if you want to leave it permanently in that configuration, the focal point might get overheated by solar energy, but maybe that would be useful too.
    Et tu BAUT? Quantum mutatus ab illo.

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    Quote Originally Posted by Ara Pacis View Post
    Sure. Mylar was used on the Echo satellites for passive microwave reflection and experienced solar sail effects, so the idea's not incompatible with reality. This assumes you're using frequencies suitable for use with mylar or kapton. (A sail made out of meta-materials on the other hand...) The only issue would be figuring out how to maintain the proper geometry for a reflector dish when you want to transform it to that purpose. Or if you want to leave it permanently in that configuration, the focal point might get overheated by solar energy, but maybe that would be useful too.
    How about an inflatable mylar sphere that's aluminized on the inside, but only in one hemisphere? Wouldn't a parabola-shaped antenna located near the center then produce a beam after reflection? I think a psi or two would be enough for it to keep it's shape.

    With the right cut of material, half of it could be a 3D parabola (aluminized) with a hemispherical non-reflective second half. Then you could use a standard horn antenna.

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    Quote Originally Posted by DoggerDan View Post
    How about an inflatable mylar sphere that's aluminized on the inside, but only in one hemisphere? Wouldn't a parabola-shaped antenna located near the center then produce a beam after reflection? I think a psi or two would be enough for it to keep it's shape.

    With the right cut of material, half of it could be a 3D parabola (aluminized) with a hemispherical non-reflective second half. Then you could use a standard horn antenna.
    That's clever. I wonder if the non-reflective film would absorb enough solar energy to be damaged or if it would attenuate the radio signal.
    Et tu BAUT? Quantum mutatus ab illo.

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    It wouldn't have to be a sphere. You could use two sheets, a hoop, and some gas. I imagine that with active components in the form of nanotube threads you could even control the shape of the mirrored surface to stay parabolic.
    Forming opinions as we speak

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    Yes but a sphere--like a balloon tank Atlas, could hold a gas, or maybe a cable suspended bottle at the focus of the suns rays, for solar-chemical combustion. Then the balloon deflates, and the solar sail you describe 'stages' then goes off on its own. A two stage solar sail.

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    (Spock eyebrow) Fascinateing! I had actualy been assuming that because of the need for an antenna to be pointed at a fixed point (Earth) two structures, one sail, and one antenna, would be needed. I was asking WRT in space communications, wondering if a sail type structure unfurled in space might be more economical, long term (given that in space you don't need to maintain a large antenna against the elements as you do a radio dish on Earth, nor build and maintain large support structures, allowing an antenna to be potentially very large but very lightweight), than building a very large antenna on Earth. My thought leading up to that being that a very large antenna ( a square Km or more) near Earth could mean less power needed for communications from distant space probes, and hence more room for science payload instead of power source.
    In space PR and Politics are as important as engineering and science. And no-one can hear you screaming about it.

    "There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy."

    Exploring other worlds with people is a great idea, but look at what has happened since the end of Apollo: How much could unmanned exploration (and astronomy) have discovered with all that money blown on paper rockets?

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    A sail trailing a long wire too--to be on the safe side. The focus solar 'reactor' would also be the feed horn...

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    a large parabollic refector can be spun about its main axis to maintain shape and to distribute incoming energy it also tends to retain its pointing direction and furthermore it could be spun out of a single point craft as a liquid which sets into an elastic solid or into a non evaporation liquid like a soap bubble, with metallic particles dispersed in it. In principle this could be just a few atoms thick. In the last case, a liquid, it would be set spinning at different rates perhaps to provide the right force balance between surface tension and centrifugal force at all points to maintain the parabola. Once spun out it could be polymerised by a burst of UV from the central craft. No inflation needed.

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    I had an idea for a conglomerate space station that used something similar as a sun shield and solar generator. It was housed on a section that rotated for centrifugal artificial 'gravity'.

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    Thanks, Ara.

    Another idea I had would be a spinning disk of aluminized Mylar, anchored at the central axis. centripetal force would keep it relatively flat, and any deviation from that caused by solar pressure would be relatively mild and mostly along the axis. No wires required, and it could be controlled from the hub, which might also serve as a storage container for the disk when it's not out there being spun.

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    I was thinking of a long wire just for communication in case something in the feed horn burned out...

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