. >> could i add in case my earlier comments were misint rhetted. first i would defer to the technological wizards dean and bob and but second based on my degree of knowledge, i see no evidence to suggest that in the 2030 timeframe we'll get to something that would allow national capabilities with either rail gun or directed energy but point defense will be vaveble. but what happens is two kinds of filters are applied. the first one says well if i'm russian or chinese or if i'm the united states looking at their capabilities i have to think about not just what they have today but in 15 years so i will be projecting forward. second there's a degree of uncertainty associated with what's present today as well. so it means that even as we see the potential early deployments of tactical uses we need to be thinking about their implications and the perceptions of our partners and of russia and china as well. >> the time for one more question. yes right there. a twin dynamics at work and i'm unclear which one might emerge dominant. and this relates to what