The massive application of titanium in spacecraft began in the United States. In 1972, the United States began to develop the "Mercury" spacecraft, which was launched for the first time in 1981 to send people into space. The spacecraft has a mass of 2t, is bell-shaped, and is divided into 3 parts: the base part, the airtight chamber (pressure chamber), and the top. The pressure chamber has a volume of 1.4m3, and the main structure is made of titanium alloy, accounting for about 80% of the total mass of the structure, weighing 168kg, and the amount of titanium used is about 240kg (purchasing quality). The airtight cabin can carry astronauts. Its inner skin is welded with a 0.25mm thick pure titanium sheet. The reinforcement rib is a Ti-5Al-2.5Sn titanium alloy extruded material, which has medium mechanical strength, and a part of the skeleton ring It is made of Ti-6Al-4V alloy, and the inner skin plate is welded to it. Ti-6Al-4V is one of the most used titanium alloys. It is a very comprehensive alloy. It not only has high mechanical properties but also can be used for a long time at 480°C. It has a high heat resistance and good weldability. The welding seam has excellent airtightness, which is extremely beneficial for adjusting the pressure in the cabin. This kind of spacecraft is launched with Atlas rockets. Many structural parts of the rocket, such as reinforcement rings and connecting rings, are made of titanium alloy. Ti-5Al-2.5Sn alloy composition (mass%): Al4.5-5.75, Sn2.0-3.0, Fe0.50, C0.08, N0.05, H0.020, O (oxygen) 0.20.
In 1984, the American "Gemini" spacecraft launched into space. This is an improved version of the "Mercury" spacecraft. It is also bell-shaped, but the amount and variety of titanium alloys are more numerous, sharing 7 kinds, and the net weight of titanium structural parts is about 570kg, Accounting for 84% of the net mass of the structure. The inner wall of the spacecraft is double-layered and welded with 0.25mm thick industrial pure titanium plates. The spherical pressure vessel made of Ti-6Al-4V titanium alloy is shown in the figure below. Its tensile strength can reach 900MPa; the structural parts of the landing gear are subject to large forces and are forged with high-strength Ti-7AI-4Mo titanium alloy. The strength can reach 1100MPa or more.
The spacecraft must slow down when it returns to the atmosphere. This task is completed by 4 round rockets loaded with solid fuel. Each rocket has 2 Ti-6Al-4V welded titanium alloy semi-circular spheres. The material thickness is 1.0mm. The deviation is 1.0mm. Strictly +0.17mm, -0.01mm. The oxygen cylinder in the passenger compartment is made of Ti-6Al-4V or Ti-13V-11Cr-3Al titanium alloy. The volume of the oxygen cylinder is 2.5L, the pressure is 2059MPa, and the mass is 160kg.
"Apollo" spacecraft. This ship is similar to the lunar exploration project Change 5 launched by the China Space Administration in 2020. But Change 5 was not manned, and "Apollo" sent people to the moon, landed on the surface of the moon, and then returned to Earth. It consists of a spacecraft hull and a large "Saturn-V" rocket. The spacecraft has a mass of 50t and a rocket mass. 2900t. The spacecraft contains a command cabin with a volume of 7.65m3, a mechanical cabin, and a lunar module. The spacecraft and rocket structure shared 68t of processed titanium. All brackets, fixtures, and fasteners of the spacecraft are made of titanium. The command module, mechanical module, and lunar module shared 1190kg of titanium.
The tower structure of the launch traction system is made of titanium alloy, and the liquid hydrogen containers and ducts of the command and mechanical compartments, and the cryogenic containers of the lunar module are all made of Ti-6Al-4V alloy. The container of the descending part of the lunar module needs to have greater plasticity, so it is made of Ti-5Al-2.5Sn alloy. The "Apollo" spacecraft has more than 40 pressure vessels, about 85% of which are made of titanium alloys, and Ti-6Al-4V and Ti-5Al-2.5Sn alloys are used to make dinitrogen tetroxide, helium, nitrogen, and fuel vessels. . Because Ti-5Al-2.5Sn alloy has high toughness at -252.7°C, liquid hydrogen and supercritical helium containers are made of this alloy.
The space shuttle is a means of communication between the ground and the space station, so it is also called a space ferry. It must be used multiple times, preferably 100 times or more. When it enters the atmosphere, the upper half of its fuselage and wings The temperature can reach 180℃-815℃. Therefore, some parts of the components need to be made of heat-resistant titanium alloy. For example, the upper fuselage frame is made of Ti/B-Al composite material, and the tail, wing beam, and ribs are all The hydraulic piping is made of titanium alloy. The oil pressure piping is a Ti-3Al-2.5V alloy seamless pipe. At the same time, the quality of the system is reduced by more than 40%. In order to reduce the sensitivity to fatigue fracture and improve the service period of the system, various pipe fittings The forming and assembling are all automated.
