Question about space craft materials.

[kelvinzero]

Ive noticed several materials used on space craft and satelite hulls, even mixed on the same craft. Could someone tell me about the different purposes of these materials and where you would expect to find them?<br /><li> silver coloured foil<li> gold coloured foil<li> white cloth (rather like space suit material)<li> matte white painted hard shell<li> unpainted metal shell<br /><br />..plus any others you have any interesting info about.</li></li></li></li></li>

 

[kelvinzero]

Obviously thermal issues are a factor. I had assumed being reflective or white related to this. What about dust impact?<br /><br />Why mix silver and gold coloured foil on the same craft, for example. Why are some areas foil, others cloth, others hard? I could make several uneducated guesses but would prefer to get info from someone who knows

 

[webtaz99]

Guessing here, but..<br />Silver = aluminized mylar = low weight, some thermal protection<br />Gold = Kapton = heavier, with high dielectric and better thermal protection <div class="Discussion_UserSignature"> </div>

 

[kelvinzero]

Thanks, it was useful just having the word 'kapton' since it gave me something to google.<br />http://en.wikipedia.org/wiki/Kapton (info including about space uses)<br />http://www.kaptontape.com/ (what it looks like)<br /><br />Any other useful terms for me to google?

 

[webtaz99]

Spacecraft materials is an evolving science. They did at least one "long duration experiment" you might want to check out. Some recent research was to protect the Deep Impact "mother ship". Hmmmm, seems Bigelow has some thoughts on this, too. <div class="Discussion_UserSignature"> </div>

 

[kelvinzero]

Thanks, found this link. Ill have a browse.<br />http://setas-www.larc.nasa.gov/LDEF/index.html

 

[jimfromnsf]

MLI - Multi layered insulation <br /><br />beta cloth<br /><br />Mylar<br /><br /><br />It is all thermal control. Unmanned spacecraft in LEO don't worry about impacts only manned spacecraft. The only planetary spacecraft that worry about impacts are the ones going near comets

 

[kelvinzero]

Thanks! I found reasonable references from those names. The first two have nice pictures to anyone that is interested.<br />http://www.rossie.com/mli.htm (multi layered insulation)<br />http://www.novaspace.com/AUTO/SINGLES/Bag.html (beta cloth)<br />http://en.wikipedia.org/wiki/PET_film_(biaxially_oriented)<br /><br />Does anyone know generally why you would choose one material over another? for example why is the ISS almost all white and largely cloth covered (Im guessing betacloth) wheras the images of the future moon lander show the tanks covered in gold film I guess is Kapton? <br /><br /><br />

 

[jimfromnsf]

Different thermal requirements. Lander tanks have cryogens, ISS has heat producing equipment and humans on the inside.<br />LEO is different than the lunar surface. 45 minute* nights and days vs 14 days of full sun.<br /><br /><br />* i know sometimes the ISS has full sun for multiple orbits

 

[tomnackid]

BTW the "foil" is actually aluminum coated mylar--like the mylar balloons you buy. The silver version is made by coating clear mylar with aluminum. The "gold" version is made by coating mylar with a yellow color--making the aluminum look like gold. This is used for thermal insulation in a vacuum. The mylar is crinkled then wrapped around the object to be protected (typically a fuel tank). The crinkles insure that ther is little surface area in contact between layers. The reflectivity of the aluminum reduced het transfer by radiation. The small amount of surface contact between layers reduces transfer via conduction and the vacuum of space prevents transfer via convection.

 

[jimfromnsf]

The yellow film is kapton

 

[kelvinzero]

Thanks! Lots of interesting points in your answers.<br /><br />I had wondered why my hot water cylinder was covered with a foil coated blanket, since Ive always associated metal with rapid heat conduction.

 

[tomnackid]

Sorry, I was using "mylar" as a generic term for polyester film when actually it is just a trade name for one specific form of polyester film.