The rocket engines shown to the left are the most efficient rocket motors in their class. Burning a liquid oxygen/rocket grade kerosene fuel mixture (LOX/RP-1) they have the highest thrust to weight ratio of any rocket engine motor existing today.These NK-33 engines were designed and built over 40 years ago by the USSR government bureau designated OKB-276, a.k.a. Kuznetsov Design Bureau, as upgraded versions of NK-15 engines used in the failed N-1 Moon launcher. And these rocket engines have never been launched. Ever. Instead, when the USSR cancelled the manned lunar program, the engines and their blueprints were ordered to be destroyed. But apparently some low level bureaucrat had other ideas, and 150 of the engines were mothballed in a warehouse for over 25 years.
Then one day in the early 1990's several American rocket engineers visiting Samara, Russia had heard that some of the rocket engines from the N-1 program had survived and asked if they could see them. They were in Russia to look at Russian rocket technology for several companies interested in purchasing rights to use the technology in their own launch systems. The engineers were led into the warehouse and were dumbfounded at the near pristine 150 rocket engines that laid in their storage mounts.
Upon hearing this news, Aerojet, one of the first rocket motor companies to be founded in the US by Theodore von Kármán, Frank Malina, and Jack Parsons, became interested in acquiring some of the NK-33 rocket engines to utilize in the new Atlas V evolved launch vehicle being designed at that time. They managed to have one shipped to their test site in Sacramento, California where engineers were able to successfully test fire the engine and determine the NK-33 would meet the thrust and payload requirements for the Atlas launch system. Aerojet purchased 36 of the NK-33 for $1.1 million each. However, Lockheed Martin chosed the more well-known and reliable Russian RD-180 rocket engines from Energia to power the Atlas V. Thus, the engines were once again stored in another warehouse. 
Then, along came Kistler Aerospace who designed their K-1 reusable launch system/spacecraft around the NK-33 and NK-43 engines (NK-43 was a slightly modified NK-33 that was designed to operate at higher altitudes) in their new reusable launch system K-1. Kistler was developing the launch system to secure satellite launch business from broadband satellite companies like Iridium, LLC who wanted to launch a constellation of 77 satellites (77 is the atomic number of iridium). Kistler was able to purchase the 36 NK-33 engines and an additional 10 more engines via Aerojet along with the right of first refusal to purchase the remaining NK-33 engines in Russia. However, due to the high cost of satellite phone service and the emerging cellular communication market, Iridium and many of its competitors fell into bankruptcy in 1999. Kistler was able to secure private financing to continue operation and development for a short time beyond 2000, but by 2003 it filed for bankruptcy. By the end of 2005, Kistler was able to emerge from bankruptcy with a new majority partner, Rocketplane LLC, who merged the company into their operations and renamed it Rocktplane Kistler. The new company was able to secure one of the new Commercial Orbital Transportation Service (COTS) contract to launch ISS cargo resupply mission being offered NASA. Space Exploration Technologies (SpaceX) had secured the other contract slot. Rocketplane Kistler won contract in a large part because the K-1 launch system was already well into its developement phase by 2006. Unfortunately, Rocketplane could not secure additional funding to continue development since few venture captial firms were willing to risk investing in a bankrupt company. Consequently, by 2007, Rocketplane was unable to meet the milestone requirement for secured financing and NASA terminated its contract and awarded a new contract to Orbital Sciences.
Orbital Sciences aleady had a new design for the cargo launch system called Taurus II/Cygnus, rocket launcher/spacecraft. The company was interested in acquiring the NK-33 motors for the 1st stage of its Taurus II rocket launcher. Aerojet by this time had reacquired the NK-33 rocket engines to which they never received full payment from Kistler. Orbital Sciences contracted with Aerojet to finish developing and testing the NK-33 engines, now designated as AJ26-58 for the Taurus II.In the first 2 weeks of March, N.D. Kuznetsov, the now private rocket motor company, completed three long duration static fire tests performed on the NK-33/AJ26-58 engines in Samara, Russia test site in support of the Taurus II vehicle develpment under contract to Aerojet. The 3 tests racked up a combined total of 600 seconds of 'hot fire', more than double the duration of launch burn cycle. The rocket engines met all the technical performance requirements for the Taurus II launch system. Orbital Science will now be working to integrate the engines into their launch platform. The first flight of the Taurus II will be conducted in March 2011. Finally, some 40 years after being designed and manufactured, the most efficient, advanced rocket engines to ever be built will roar into the deep blue sky.
Supplemental: The NK-33 was based on the NK-15 design used in the N-1 Moon rocket. Below is a video of the last N-1 launch featuring the NK-15 engines:
Despite the apparent successful liftoff, the launch ended in failure after engine shutoff at 40 km. The first launch of the N-1 ended in a disaster killing several hundred people as can be seen below. The N-1 1st stage had 30 NK-15 engines mounted around its circumference. The engines did not fail, but the fuel pumping/transfer and injection systems did fail causing the explosion.
Note: Photos are courtesy of Orbital Sciences and Rocketplane Kistler
