Application of titanium in aerospace
The application of titanium in aerospace industry mainly makes use of its low density, high strength, high temperature resistance, corrosion resistance and other properties.
The application of titanium in the aerospace industry has also achieved the goal of reducing the launch weight, increasing the range, and saving costs. It is a popular material in the aerospace industry. In the rocket, missile and aerospace industries, it can be used as pressure vessel, fuel storage tank, rocket engine housing, rocket nozzle sleeve, artificial satellite housing, manned spacecraft cabin (skin and structural framework), landing gear, lunar module, propulsion system, etc.
Ti-6Al-4V alloy is widely used as the casing material of the first stage rocket engine in the United States. The alloy is also used for: giant cylindrical liquid rocket container; Multiple spherical and elliptical engine housings, such as intercontinental ballistic missiles and "Minuteman" missiles. On the other hand, because the interstitial elements of Ti-6Al-4VELI and Ti-5Al-2.5SnELI alloys, especially the oxygen content, are low and can be used at ultra-low temperatures, these alloys are used as liquid hydrogen containers for rockets and missiles, as well as the capsule of "Mercury" spacecraft and "Gemini" spacecraft, and as the main structural parts of the "Apollo" spacecraft successfully landed on the moon.
In addition to industrial pure titanium, Ti-6Al-4V, Ti-5Al-2.5Sn, Ti-6Al-4VELI and Ti-5Al-2.5SnELI, Ti-7Al-4Mo, Ti-3Al-2.5V, Ti-13V-1Cr-Ti-15V-3Cr-3Sn-3Al and Ti/B-Al composites are used in titanium and titanium alloys used in the aerospace industry.
The space shuttle is the first manned spacecraft in the world that can be used repeatedly. It was developed in 1972 and the first flight was successful in 1981. The spaceship consists of an aircraft with small wings, a 47m long external fuel container and two 500t solid fuel rocket boosters.
The orbiting spaceship, 37m long and 68t in weight, is roughly the same size as the jet transport aircraft DC-9. It is the largest manned spaceship so far. Its cargo bin is 18m long and 5m in diameter, and can transport 29.5t of cargo to the earth orbit.
The space shuttle can be launched like a rocket, and fly like a spaceship in an orbit with a maximum altitude of 1000km. It can glide and land like a plane without thrust. This kind of space shuttle is essentially a space transport ship. Therefore, one of the parameters to judge its usefulness is the effective payload for transportation between the earth and its orbit. In order to maximize the effective load, titanium alloy has become an important material for aerospace motor components.
The design life of the orbiting spacecraft is 100 flights, and each flight lasts for 7 to 30 days. The spacecraft is manned, so it is designed to adapt to the space environment (vacuum, extreme temperature difference on the orbit, heating when returning to the atmosphere, etc.) and be reused.
1. High pressure vessel
Titanium alloys are used in many places because they can reduce the total weight of spacecraft orbiting spacecraft. The main use part of titanium is the high-pressure container for filling necessary fuel and gas. The lightweight titanium alloy container has been successfully developed in NASA's twin constellation spacecraft and Apollo spacecraft two programs, using Ti-6Al-4V alloy. The iron pressure vessel on Apollo spacecraft has actually used the design with a safety factor of 1.5 without the previous example. Previously, it was designed with a safety factor of about 4. In order to further lighten the high pressure storage container of the orbiting space shuttle, the method of adding white finch fiber (aromatic organic fiber produced by DuPont) on the surface of the thin-walled titanium container was adopted.
Pressure vessel for storing compressed gas. The rover satellite and booster shared 14 titanium containers, reducing the mass by 272kg.
A pressure vessel for storing liquid propellant. Apollo spacecraft used about 50 pressure vessels, 85% of which were made of titanium. The weight of the Hercules III transition stage engine is reduced by 35% after the use of titanium alloy propellant tank.
2. Engine housing
Solid fuel rocket motor housing. The second stage rocket engine of the Minuteman intercontinental missile uses Ti64 alloy to reduce the weight by 30%~40%.
Shell of liquid fuel rocket engine. The pressure housing of the combustion chamber of the descending engine of the Apollo lunar module is made of Ti64 alloy.
3. Various structural members
Titanium alloys are also widely used in various structural parts. The pressure chamber of the Mercury spacecraft is mainly made of titanium, accounting for 80% of the cabin weight. The "Gemini Constellation" spaceship has 7 types of titanium alloy, and 570kg titanium parts are used, accounting for 84% of the structure weight. The brackets, clamps and fasteners of the Apollo spacecraft are made of titanium, and a total of 68t titanium materials are used.
4. Oil pressure piping
The oil pressure piping of the space shuttle uses seamless tubes made of Ti-3Al-2.5V alloy. Because of this alloy, the weight can be reduced by more than 40%. In order to reduce the sensitivity to fatigue fracture and improve the actual life of the system, various tubes are assembled by automatic forming.