I may be wrong, but I'm pretty sure the Russians were experimenting with multi-engine boosters back in the 1950's - 1960's. The planned and canned (in 2011) Rus-M vehicle was to use 3 x RD-180 engines for the first stage, but the complexity seemed to be not worth the gains.
>"We have come to the conclusion that we do not need a new rocket, we can continue using those we already have," said Vladimir Popovkin, head of Russia's space agency [1]
I love that rocket development seems to be one of the areas where safety is a balance between redundancy and simplicity. If you put 3 highly-explosive engines with a low probability of failure next to each-other, you don't get redundancy unless you really control the failure modes :-)
>"We have come to the conclusion that we do not need a new rocket, we can continue using those we already have," said Vladimir Popovkin, head of Russia's space agency [1]
I love that rocket development seems to be one of the areas where safety is a balance between redundancy and simplicity. If you put 3 highly-explosive engines with a low probability of failure next to each-other, you don't get redundancy unless you really control the failure modes :-)
[1]: http://en.wikipedia.org/wiki/Rus-M