 Most of the decommissioned Titan II ICBMs were refurbished and used for Air Force space launch vehicles, with a perfect launch success record.For orbital launches, there were strong advantages to using higher-performance liquid hydrogen or RP-1 (kerosene) fueled vehicles with a liquid oxygen oxidizer; the high cost of using hydrazine and nitrogen tetroxide, along with the special care that was needed due to their toxicity, were a further consideration.Lockheed Martin decided to extend its Atlas family of rockets instead of its more expensive Titans, along with participating in joint-ventures to sell launches on the Russian Proton rocket and the new Boeing-built Delta IV class of medium and heavy-lift launch vehicles.