One more clarification: The refurbished Russian engines that Orbital Sciences is using were not developed for an ICBM, but for the N1 rocket the Soviets tried to build to compete with the Saturn 5. See: http://www.orbital.com/Antares-Cygnus/ (scroll down to January 2013.)

The N1 was intended as their rocket to transport astronauts to the Moon, but it failed at every launch and was abandoned. The failures were not related to the engines themselves but to other quality control issues.

Thanks for the clarifications.

In this case you are mistaken. The Merlin engine is the first new American-built rocket engine in decades. The engines that are refurbished Soviet-era engines are the engines on Orbital Sciences’ Antares rocket.

SpaceX has been attempting to recover its first stage from day one, with little success. This is why they are testing Grasshopper, which they say will return to the ground vertical.

No. The Merlin is a brand new engine designed and built entirely in house by SpaceX.
You’re thinking of the Aerojet AJ26 engine which is to be used on Orbital’s Antares rocket. That was the engine originally built in Russia, bought by Aerojet and updated with modern electronics. etc. The Antares has 2 AJ26 engines.
The Falcon 9 has 9 Merlin 1c engines.
By the way this was the last flight of the merlin 1c engine. SpaceX’s next flight (june) will be the Falcon 9 v1.1 which will feature the new Merlin 1D engines.
The merlin 1c had 53 flights for 52 successes. 51 if you count F1.003 as a failure. The Merlin performed flawlessly on that flight but the 2nd stage recontacted the first stage after seperation leading to loss of mission.

They are trying.
Their plan is to make both first and second stages reusable.
Whether they succeed or not is still to be decided.
SpaceX’s Grasshopper is all about teaching a first stage to land gracefully and not like a brick.

After the rebuild and certifications they just renamed them Merlin.

And that they only have about 120 of them total. And if they don’t start recovering and reusing them they stand a chance of running out of them before the final launches.