🚀 go-pugleaf

>
>
>        For Christmas I received a Space Shuttle model with instructions to
>paint the underside black.  This brought up the question "Why is the
>bottom of the Shuttle black?"  It occurred to us that a black surface might
>absorb a lot more radiation and that in space there might be greater
>exposure to radiation than on earth, so why isn't the whole shuttle white
>or perhaps silver to reflect as much as possible?
>
>        Perhaps a simple posted response would be better than everyone
>sending mail to me, only to have me follow up with a post.
>
>--
>/*______________________________Jeff Tannehill_______________________________*

    The shuttle uses many different types of thermal insulation. There
    are tiles and thermal blankets, and there are varieties of each.
    The black tiles are rated for the highest temperatures and are used
    where the shuttle gets the greatest heating (the underside, the nose,
    and the leading edge of the tail). White tiles are next, with the
    second-highest rated protection, and are used on the forward fuselage,
    the aft area, and the tail. The lowest temperatures on the shuttle
    are experienced on the upper surfaces, i.e., the tops of the wings
    and the tops of the payload bay doors. In this area, NASA switched
    from white tiles to thermal blankets in 1984, so Discovery, Atlantis,
    and Endeavour have blankets while Columbia still mostly has tiles.
    Both are white, but you can see the differences in good photos.
    
    That's a simple, but not complete or 100% accurate description. The
    Shuttle also uses a grey thermal insulation on the wing leading
    edges, but I'm not sure which category they belong to.
    
    Please note that the tiles and blankets have proven very effective
    in the years since the 1981-82 test flights, despite their
    reputation for being a maintenance nightmare. The average flight
    requires the replacement of only a half-dozen tiles (more on the
    dry-lake runways at Edwards, less on the concrete at the Cape.)
       
    -Brian

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Brian S. Thorn                                    "If ignorance is bliss,
BrianT@cup.portal.com                               this must be heaven."
                                                -Diane Chambers, "Cheers"
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