Kholod (�����) is the name of a rocket project. This project was developed in Russia. The engine of the rocket is called a scramjet. It was created to be faster than Mach 5.75. The prototype includes a Soyuz TMKB with liquid hydrogen and modified fillings from the SA-5 Gammon rockets. The rocket with the starting blocks (complete laboratory) is 12 meters long and has 750mm in diameter. NASA cooperated on the fourth flight in February 12, 1998. The speed of that flight was Mach 6.4. 95 million United States dollars were invested in this project. 