Downloaded from https://www.everyspec.com STRUCIURES TABLE 1-1. (Continued) 1-2- BALLISTIC MISSILE STRUCTURAL CONSIDERATIONS p Constant, creep lav.s The structural designer of a missile or an Prefsure airplane h&-, much les,, freedom in selecting Cceflcient of first harmonic of the external shape of -his design than the de- thermal stress distribution signc'r of a bridge or building strufcture. The -external form is largely prescribed for him P Critical pressure by other requirements. As a consequence his P End load on column t-zrk is a more difficult one.
The designer hast q Rate of cooling to work within the space available and inust Rate of heat generation in ele- ensure that sufficient strength is provided mental volume with the minimum amount of weight. The Rate ,.f het-t flow conservation of weight is of particuiar im- Cornstant, creep laws portance in ballistic miss"le 111_ ue to the mag- Q Quantity of heat nitude of the growth factor. This factor is r Muliiplying factor the additional weight of 'the fuel anid strue- R Rockwell hardness tural rnaterial requiredi by the addition of Radius one pound of n)ay!oad to the 3riginal payload.
Rc,, R~, R, Stress ratios, interaction formulas The most important difference between the PTemperature, Rankine scale structure of a ballistic missile and mrost other R.T. Room temperature structures is that the re-entry portion of the t Thickness tyliss~le structure must be designed to with- Time stand high rates of hcatinir This aerody- t~,Critical time narnic lheatng raises tl~e temperature of the T Temperature structure and influences -adically its load- u, v, w Displacements in x, y, z directions carrying capacity.
Of course, aerodynamic respectively healing is present in all supersonic aircraft, VVolume but it is h~i the ballistic missile that it a9ttains Shear force -its maximum importance. wSpecific weight For this _7eason a new parameter, namely x, y, z Space variables 4 enperaturL, enters the analysis of the struc- yDsncfrm euriaiina ture. The elevated temperature, in turn, in- must also be considered carefully in the GREEK VITTTERS analysis of missile structures.
While 'the a Thermal diffusivity structure of a conve ntional ground-based Coefficient of thermal expansion subsonic airplane in ,irindcpie lasts for an e Normal strain almost indefinite per.od, the hot sti uctural Emissivity ukuremets of missiles change their shape con- ly Half ape;: angle of cone tinuously under load until they become 'o Constant, creep Jaws deformed that they are incapablie of perform- vPoicson's Ratio ing their structural duties. Rate of radiant energy emissiop or Every structuare that has to perform at absorption very high temperature has, therefore, a defi- p Radius of gyration nite lifetime beyond wh~ich it cannot be a'Normal stress utilized.
The consideration of this lifetime Stpfaii-Boltzmann constant muakes the task of designing and analy:,sing Criti&. normal stress a missile strticture much more complicated Shear st;-ess than similar iasks Performed itn connectidn TlCritical shear stress with more conventional structilres, T~te "one- 2 2