Radiation Exposure in Space

[Tad Blanchard <Tad.M.Blanchard.1@gsfc.nasa.gov>]

Hi all,

        Sorry about the lag in response to this question.  

        Someone wanted to know what Shannon Lucid's six-month exposure was.

        I contacted the Head of the Radiation Physics Office here at Goddard
Space Flight Center.  In summary, he told me that cosmic ray exposure in
space is insignificant.  The estimate is based on exposure to solar
radiation at "Solar Minimum", a finite slab of aluminum shield, 4 Pi
exposure, 6 months duration with radiation components considered as Trapped
Electrons, Bremsstrahlung (<0.1%), and Trapped Protons.  

        Actual TLD results are the best to determine exposure but that info
is not available to me.  However, an estimate can be determined by
calculating the approximate skin dose (Rad/H2O) >99% from protons.  Here's
the chart that I was provided.  (Note:  The MIR spacecraft has variations in
density therefore the chart denotes various shield thicknesses)

                            TOTAL DOSE (Rad Aluminum)*

Shield     Altitude-500km   Altitude-600km   Altitude-550 km    Approximate
Thickness   Inclination       Inclination     Inclination       Skin  Dose
(gm/cm-2)   50deg   60deg    50deg   60deg       55-deg         (rads/H2O)

   2         32.6    26.1     62.1    56.3        ~44.3             ~59
   3         25.8    20.6     50.6    44.9        ~35.5             ~47
   4         21.3    17.1     46.4    37.5        ~30.6             ~41
   5         18.0    14.5     39.5    32.0        ~26.0             ~35
   6         15.5    12.6     34.2    27.8        ~22.6             ~30
   7         12.0     9.8     26.7    21.8        ~17.6             ~23

*Note:  Rad Aluminum dose is not equivalent to rem/tissue dose.

The total dose experienced by Shannon Lucid is a function of "altitude,
inclination, shield thickness in a 3-mass distribution, composition of
shielding, and specific target location (e.g., skin, blood forming organs,
eyes, gonads, etc).  

This information was provided by Dr. E.G. Stassinopoulos.  He will be the
guest speaker at the Baltimore-Washington Chapter of the Health Physics
Society Meeting to be held at Goddard Space Flight Center on Wednesday,
November 13, 1996.  The meeting will include a tour of NASA-Goddard, steak,
shrimp, and free beer.  If you're in the area, plan to attend.  It should be
an interesting meeting.  
**************************** /^\   /^\ *********************************
Tad  Blanchard              /__ \ /___\    NASA-Goddard Space Flt Ctr 
Nat'l Health Svc, Inc            O             Greenbelt, Maryland     
Sr Health Physics Tech          / \            Phone: 301-286-9157     
                               /___\           Fax:   301-286-1618       
                  Tad.M.Blanchard.1@GSFC.NASA.gov                   
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