Unfortunately, this is not very realistic. This uses clone, which in real life, does exist. This means that it can go on forever, while the real solid rocket boosters (this is taken straight from the nasa site) only last 2 minutes. I managed to make one of these that went for 15 seconds using no clones, only nitro, wood, broken coal, and rubidium.
@Ipquarx Well, yea, but we can't have everything, can we? I was going to make it without clone, but I figured I'd get loads of noobs on my ass complaining. And, after all, most of my realistic creations get about 4 votes then sit there doing nothing forever. 1 little thing does not make something go from 'quite realistic' to 'not very realistic'. The whole point is that it doesn't use loads of PUMP, which increases realism. a few pixels of clone shouldn't counter that.
It barely even matters. It'd be unrealistic without clone, as it would last about 5 seconds and the fuel tanks would have to be out of proportion for the time it takes to burn.
@code1949 My version with no PUMP or FAN is actually less realistic, as it generates barely enough thrust to move forward slowly. :P It's also less stable.