Application of Titanium on U.S. Spacecraft

The large-scale application of titanium in spacecraft began in the United States. The development of the “Mercury” spacecraft began in 1972, and it was launched for the first time in 1981 to send people into space. The spacecraft has a mass of 2t and is bell-shaped. It is divided into three parts: the base, 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 seat astronauts. Its inner skin is welded with a 0.25mm thick pure titanium sheet. The reinforcement is made of 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 more 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 high heat resistance, good weldability, The weld seam has excellent air tightness, 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, O0.20.

In 1984, the “Gemini” spacecraft was launched into space. It was an improved version of the “Mercury” spacecraft. It was also bell-shaped. However, the amount and variety of titanium alloys increased. There were 7 types in common. The net weight of titanium structural parts was about 570kg, accounting for the structure. 84% of net mass. 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 has a tensile strength of up to 900MPa; the landing gear structure is subjected to large forces and is forged with high-strength Ti-7AI-4Mo titanium alloy, and its tensile strength can reach 1100MPa Or bigger.

The spacecraft must slow down when it returns to the atmosphere. This task is completed by 4 round rockets filled with solid fuel. Each rocket has 2 Ti-6Al-4V welded titanium alloy semi-circular spheres, the material thickness is 1.0mm, and 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 Chang’e 5 launched by the China Space Administration in 2020. However, Chang’e 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 the rocket structure shared 68t of processed titanium. All brackets, fixtures and fasteners of the spacecraft are made of titanium. The command module, the mechanical module and the 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 compartment, and the cryogenic container of the lunar module are all made of Ti-6Al-4V alloy. The lower part of the lunar module container needs to have greater plasticity, so it is made of Ti-5Al-2.5Sn alloy. The “Apollo” spacecraft has more than 40 pressure vessels, of which about 85% 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 needs to 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 alloys, such as Ti/B-Al composite materials for the upper fuselage frame, and the tail, wing beam and ribs. The hydraulic piping is made of titanium alloy, and the oil pressure piping is Ti-3Al-2.5V alloy seamless pipe, which reduces the quality of the system by more than 40%. In order to reduce the sensitivity to fatigue fracture and improve the service period of the system, various pipe fittings Both forming and assembly are automated.