http://www.thespacereview.com/article/226/1<br /><br />There are a number of advantages to using tried-and-tested SRBs with a liquid second stage, but:<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>There are technical issues that a SRB-derived launch system would have to address, notably the development of a new upper stage. However, in the long run the bigger challenges that an SRB-based launcher might have to face are perceptions: that the SRB is an old technology, best left to the past; that solid-propellant motors like the SRB, which can’t be turned off once ignited, are unsuited for manned spaceflight applications; that the EELV will need the anticipated volume of CEV launches to lessen the cost burden of the two vehicle programs on NASA and the Defense Department. Successfully handing those perceptions will depend on the champions the SRB design wins within NASA and industry. In a brief interview after his Mars Society presentation, Horowitz admitted that industry was skeptical about the idea at first but has since started to warm to it. There’s certainly a lot more work that Horowitz and others will have to do, though, to gain converts to an SRB-launched CEV.<p><hr /></p></p></blockquote><br /><br />What do you guys think??