2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
Elon Musk showed off the first prototype of the second stage of the BFR super-heavy rocket, which will be used next year for flight tests. In addition, he spoke about changes in the rocket design, including the abandonment of the carbon fiber body and passive thermal protection, SpaceNews reports.
The BFR is a two-stage super-heavy launch vehicle being developed by SpaceX as a replacement for the Falcon 9 and Falcon Heavy rockets. Both BFR stages are being developed as fully reusable, with the second stage simultaneously serving as a cargo bay for the payload or a manned spacecraft for the crew, depending on the version. The first stage of the BFR will use 31 Raptor engines that run on a mixture of methane and oxygen, while the second stage will have 7 such engines, adapted to operate in a vacuum.
The BFR project was originally introduced in 2017 and has undergone many changes since then. The main one is a decrease in the mass of the payload to be withdrawn when both stages are returned from 150 to 100 tons. In addition, according to the new version of the project, presented in September 2018, the second stage will be equipped with three landing legs, two of which will also act as a controlled tail assembly, as well as two aerodynamic rudders located in the bow. Also, in December, Elon Musk said that the designers decided to change the material of the rocket body from carbon fiber to metal.
At the end of December, Musk revealed new details about the BFR project itself, as well as about the test prototype, which will begin making short flights with takeoff and subsequent landing in the spring of 2019. Similarly, SpaceX engineers used a prototype called the Grasshopper, which they then incorporated into the Falcon 9 first stage landing system. The BFR (also known as Starship) second stage prototype will have the same diameter as the final rocket (9 meters), but will have a lower height. In addition, not seven, but three Raptor engines will be installed in it, since the prototype does not include an entry into orbit. Musk tweeted a photo of two prototype segments:
Musk said SpaceX has developed a new Inconel alloy that will be used in the Raptor engine. Inconels are austenitic nickel-chromium alloys characterized by high heat resistance, due to which they are often used in harsh conditions, including in rocket engines. The new SX500 alloy is able to withstand pressures in excess of 800 atmospheres while being exposed to an oxygenated gas mixture. Musk also said that the steel from which the rocket body will be made is inferior to carbon fiber in terms of specific strength (taking into account mass) only at room temperature, and at high and low temperatures, the choice of steel is more optimal.
In addition, the choice of steel as the main material of the rocket forced engineers to change the way the rocket was protected from heating up when entering the atmosphere. SpaceX engineers will develop a liquid cooling system for the hull using methane from a fuel tank. The body will not be covered with paint or heat protection. Instead, the steel will be polished for maximum reflectivity. Elon Musk also confirmed that the new version of the second stage of the BFR will be able to independently enter orbit without using the first stage. At the same time, it will not be able to launch additional cargo into orbit, so the company will not use it in this way. However, if the company manages to do this, BFR will be the first single-stage space system to be put into practice.
Other companies are also working on the creation of fully or partially reusable launch vehicles. For example, Blue Origin intends to launch the New Glenn heavy-class rocket in 2020. It also has a two-stage design and will be equipped with methane engines, but only the first stage will return to the offshore platform or spaceport after launch. In 2017, the company first tested the BE-4 engine for this rocket. In addition to New Glenn, the BE-4 will also be used in the promising Vulcan rocket of the ULA alliance. It will also be partially reusable, but not the entire first stage will be returned, but only the engine block - the most expensive component of the rocket.