SpaceX has announced their Falcon Heavy lift rocket. It consists of two liquid fuel rockets astride a longer center rocket. Each of the three rockets has 9 Merlin rocket engines. SpaceX claims it will lift 53 metric tons into low earth orbit- twice the payload of the Space Shuttle and more than twice that of the Delta IV. Depending on configuration a launch will cost between $80 and $125 million.
This seems to be real progress for the space business.
Lamentations on Chemistry 
The propellant cross-feed system is the most interesting technical feature. Emptying out the side tanks first allows you to drop the mass of the strap-on boosters as soon as possible after launch, leaving the centre tank almost full. It is a superb application of the physics of multi-stage rockets, in exchange for the extra complexity, weight and risk of failure that comes along with the cross-feed piping.
Hi Joe,
Thanks for sharing that technical morsel. So, this makes the center section a type of second stage. Even though the strap-on sections use 18 liquid fuel engines, the economics apparently favors this over solid motors. Maybe.
Perhaps the use of strap-on solid motors with the center section liquid would necessitate a 9 engine start while in flight to get the benefit of staging. My guess is that a ground start may be more desirable over a supersonic start at elevation. So, the cross-feed that you mention has the side benefit of assuring that the 9 center section motors are functioning properly rather than relying on an 9 successful starts in flight. This may have been a design consideration.