Read the following paragraph and cross out TWO irrelevant sentences.
    Each of the Russian manned space exploration projects had specific major goals. For example, the Vostok project was designed to test whether or not human beings could survive and function in outer space. For another example, the Voshkhod project was intended to find out whether people could work in the weightless environment of space. One Voshkhod cosmonaut(苏联宇航员) experimented with weightlessness by taking a "spacewalk". That is, he floated in a spacesuit outside his Voshkhod spacecraft, connected to it by a tether(系绳, 系链). The cosmonaut who did that was Alexei Leonov. Several weeks later, Leonov's spacewalk was followed by that of U.S. astronaut Ed White. Finally, the Soyuz project, with three cosmonauts, had goals of testing spacecraft and spaceflight skills so that people could fly long missions in Earth orbit. China's spaceflight skills are catching up.