Application of Titanium on U.S. Spacecraft-I
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 thickness 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 has not only the 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, all are made of titanium alloy. Ti-5Al-2.5Sn alloy composition (mass%): Al: 4.50 - 5.75, Sn: 2.00 - 3.00, Fe max: 0.50, C max: 0.08, N max: 0.05, H max: 0.020, O max: 0.20.
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.
