 how ineffective shielding is for stopping protons. Note the steep falloff in the electron dose with increasing depth and the relatively flat character of the proton curve. Increasing the shield thickness form 100 to 1000 mils only reduces the resulting dose by about 50%. For this reason, and others discussed later, shielding is often not the best technique for minimizing proton effects. Table 1: List of tables describing proton-related environments for ISSA [SSP-30512] Table Description 3.1.1-2 AP8MAX differential and integral flux energy spectra for trapped protons 3.1.2-1 One year dose at the center of a solid aluminum sphere (rads(Si)) 3.1.2-2 One year dose in semi-infinite aluminum medium (rads(Si)) 3.2.1.1-1 Daily average internal proton integral flux spectrum 3.2.1.1-2 Daily average internal proton differential flux spectrum 3.2.1.2-1 SAA pass internal peak proton integral flux spectrum 3.2.1.2-2 SAA pass internal peak proton differential flux spectrum 3.2.1.4-1 Combined integral flux LET spectra (WI =4) no solar flare flux 3.2.2-1 Maximum solar flare peak proton integral flux spectrum 3.2.2-2 Maximum solar flare peak proton differential flux spectrum WI = weather index AP8-MAX Integral Flux for ISSA 1.0E+08 1.0E+07 1.0E+06 1.0E+05 1.0E+04 1.0E+03 1.0E+02 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 Proton Energy (MeV) Figure 2. Integral daily proton flux for the example International Space Station Alpha orbit of 500 km X 51.6 degrees shows the large numbers of low energy protons that are easily shielded. Fluxes in the tens to hundreds of MeV can penetrate to sensitive components resulting in single event effects and both ionizing dose and non-ionizing dose. 1.E+05 1.E+04 Proton Dose (rad(Si)) Electron Dose (rad(Si)) 1.E+03 Total Dose (rad(Si)) 1.E+02 1.E+01 1.E+00 1.E-01 10000 Shield Thickness (mils Al) Figure 3. For the 500 km X 51.6 degree orbit for ISSA, the dose from trapped protons dominates for Al shield thicknesses above 200 mils. With increasing shield thickness, the average proton energy increases. 