19. The rocket Eay carry one or sereral valhead.s, r^rhich nay be independentl-ytar6ete,l- the nultiple. initependently targetabLe re_entry .,Lniol. (Ufnvl ".r"1., vas tlevelopeal by the united states in the late 1g6os ana- is a"oioy"a-J"" ty tr,usoviet union. rn a Mr*vear systen, the separate re- entry vehici.es- are usuallycarried on a 'bustt r,rhich rel eases the Rvs one by one after eaking pre-seleetedchanges io speed. anal orientation so as to direci the RVs to their -="prrrtu targets.These RVs can reportedly land insicle an area of perhaps 150 ]""; -;y- t'OO-;r. Thus " they are not as compreteJ.y independent in a*ivar trne or location as they wourdbe vere thev on different rcBr'rs, and they provide less tarletin!- ir""itiritv. 20" triith increasing nissire accuracy and many Rvs per missile, MrRV has raiseilthe spectre that a frection of one siders rcBi{ forcis rnay in a ,'first strike',destroy the opponentrs rcBl.ls stil"l housed in their hardeneil silos. ?his woult! bepossible v-ith sufficient accuracy and reriabir.ity of the attacking Rvs, and. ifthe rcB4s to be attacrred. '.rere not raunched. before they nere destroyed. rtrissitua'bion is therefore considerecr. to be potentially unstabr-e, since in tine ofcrisis each sicle uay consid.er reunehing its r'issitls rather ihan risk theirdestruction, 2r' rf a target is vulnerabre to a particular pre.sure rever of the air bIast,its destruction mqy be achieved within a certain rexinum area around. the pointof d.etonation, The size of this area increeses with the weapon yield (e.g., by afactor 4 for an B-fold increase in yield or a factor loo for a r,ooo-for.d. increasein yield). By contrast, the area of destruction due to br-ast increases inproporti.on to the nuuber of veapons. This neans in practice that the degtructionis increasetl by increaslng the nurrber of varheads and lorering their ind.ividualRV yield; i.e., one Large varhead is not so effective as severel srnal-Ier ones ofthe same_total yield spread out over the taxget area. This is also iuustrsted by
**Analysis**
The text appears to be discussing the development and capabilities of a military technology, specifically a type of missile system. The language used is technical and focuses on the details of the system's design and functionality. The text also touches on the strategic implications of this technology, including the potential for a "first strike" and the need for retribution. This suggests that the category should be related to defense or military technology.

**Category**
Science and technology