Soyuz 5 was a dual mission with Soyuz 4 that conducted the first-ever docking of two crew vehicles together in orbit and the first time crew transferred from one craft to another. Soyuz 5 launched with three crewmembers. The meeting marked the first docking for the Soviet Union. Afterward, two crewmembers from Soyuz 5 spacewalked over to Soyuz 4. The crew transfer proved a cosmonaut could spacewalk between two vehicles, a vital part of the Soviet Moon landing plan. Soyuz 5 became the first human spaceflight to return to Earth with fewer people than when it launched. During landing, the Service Module did not separate and the Soyuz descent module reentered nose-first with little thermal protection. Mere seconds before the hatch burned through, the Service Module was torn off and Soyuz 5 settled into its proper heat-shield-first orientation. The parachute lines then tangled and the braking rockets failed, resulting in broken teeth for the single cosmonaut aboard.