Ilon Musk explained why Starship will be stainless steel
SpaceX is actively working on the Starship super heavyweight carrier (previously called BFR ). It is this space transporter that will be able to provide delivery of cargo to the Moon and Mars, which will allow a person to start exploring space more actively. According to SpaceX engineers, the best material for creating such a rocket is stainless steel. Not aluminum or carbon fiber, but steel.
The other day, Ilon Musk explained why this is so. The main reason is that it is much easier to build a rocket body using stainless steel than from aluminum, carbon fiber and other materials. Yes, the body of carbon fiber and aluminum will be much lighter than steel. But development in this case will be delayed, and after all Musk wants to realize his plans as quickly as possible.
In addition, steel has other advantages. So, it is much cheaper than modern "space" materials. For example, one kilogram of carbon fiber costs about $ 135. When creating a rocket body, the entire volume of this material will not be able to be used due to its specific properties. About 35% of carbon is a marriage. Therefore, its notional value increases to $ 200 per 1 kg. But a kilogram of sheet steel costs only $ 3, and many companies produce stainless steel, it will become very short in short supply.
In addition, stainless steel (specialized alloy) better makes temperature drops. It is resistant to external factors, and for designers it is important that the material does not form microcracks, which can lead to critical failures that are unacceptable. Moreover, special steels with the addition of chromium and nickel are resistant to ultra low temperatures. Fuel for missiles has an extremely low temperature, so the tank material must withstand it.
If ordinary steel is cooled with liquid nitrogen and then hit with a hammer, it will break like glass. This behavior of the tank material is unacceptable for the space industry. And stainless steel with the addition of chromium and nickel - the way out. It is not subject to the damaging effects of ultra-low temperature. It is also resistant to vibrations and overloads. Ordinary steel under the conditions of operation of space transport can give a crack, which then can not be repaired. Nickel-chromium alloys are not as fragile as other steel grades.
Also stainless steel will helpcreate a reusable heat shield. Mask plans to replace heat-resistant tiles, which are now used to protect the hull of space ships on a two-layer steel “sandwich”. The body will consist of two layers of steel, between them - the usual air. To protect the ship from high temperatures, water will be injected into the space between the layers. In the case of carbon, there will be not two layers, but from 60 to 120 layers.
Steel can easily cope with a temperature of 800 degrees Celsius, which aluminum and carbon cannot boast. The latter begins to deform already at a temperature of 150 degrees Celsius. Aluminum melts at 660 degrees. Thus, the ship will be perfectly protected from many factors that threaten the critical failures of modern rockets made of aluminum and carbon. Due to this heat shield can be much easier, and more - cheaper than carbon or aluminum.
By the way, it was precisely stainless steel that NASA engineers tried to use when creating the Atlas. Then they abandoned this idea because they could not create an alloy with the required qualities. But now the metallurgy is much more perfect than what engineers had in the middle of the last century, so Ilon Musk is sure of success.
According to the entrepreneur, SpaceX will use steel 301 marks. Yes, it sounds strange in the space age, but the main thing here is practicality and efficiency. Steel 301 marks are often used to create pipes that are resistant to aggressive media. Resistance to negative external factors is a valuable feature that the space industry needs.
SpaceX, according to Ilona Mask, has its own team of material scientists. They came to the conclusion that at this stage the best option would be 301 steel grades. Later, it may be used a different alloy.