Przejdź do głównej treści

Widok zawartości stron Widok zawartości stron

News

Nawigacja okruszkowa Nawigacja okruszkowa

Widok zawartości stron Widok zawartości stron

Space Petrol Station

Space Petrol Station

In February 2018 we could watch a spectacular launch of Elon Musk’s "Falcon Heavy" rocket. Unfortunately, its core component did not land successfully during the test-flight, due to the shortage of fuel blend necessary for the operation. Fuel reserve is one of the key elements of a successful space mission. One of the possible solutions to this problem has been described by the JU physicist Jakub Mielczarek, author of the blog Science-Technology-Future.

The costs of transporting sufficient amounts of rocket fuel to the surface of Mars are enormous. If humans were to establish a colony on this planet, a much more feasible and promising solution would be to produce rocket fuel on Mars itself.

What about hydrogen?

Liquid hydrogen obtained in the process of water electrolysis is the first candidate for rocket fuel. Martian soil is rich in water ice. Hence, the loose Martian surface rock (regolith) should be first heated in order to vaporise water, and then the liquefied water should be subjected to an electric current, for instance from a photovoltaic installation. It should be stressed that this process of water electrolysis also produces oxygen, which can be used both as the substance necessary for fuel combustion in engines (oxidant) and as an ingredient of breathing gas for astronauts. Yet, the hydrogen obtained in the process of electrolysis cannot be considered the best source of fuel for spaceships departing from Mars.

An artistic depiction of future fuel tanks on Mars. Source: NASA/John Frassanito and Associates

The problem is that hydrogen used as a rocket fuel must be stored in liquid form, which is a very demanding task due to its extremely low boiling point – about -253°C (20 K) under atmospheric pressure. Creating a system that would enable keeping hydrogen in such extreme conditions would be very difficult, at least during the initial stage of the functioning of a hypothetical Mars colony.

An indispensible ingredient

Fortunately, there is another useful substance, which constitutes 95 percent of Mars’ atmosphere: carbon dioxide.

The use of compressed carbon dioxide in combination with hydrogen allows scientists to carry out the reaction called methanation, which was discovered by Paul Sabatier, 1912 Nobel Prize laureate in chemistry. The reaction, also known as the Sabatier reaction, can be described by the following equation:

CO2 + 4H2 → CH4 + 2H20

The optimal temperature for this reaction is 300-400°C. It also requires a special surface which acts as a catalyst, made, for instance, from nickel or ruthenium.

The methane produced by the Sabatier reaction provides a reasonable alternative to hydrogen as a rocket fuel. The storage of liquid methane turns out to be much easier, since its boiling point is about -162°C (111 K), almost 100°C higher than that of hydrogen. The liquid methane storage technology is well-developed and commonly used in various conditions. Such fuel tanks are used, for instance, in LNG-powered buses (LNG stands for liquefied natural gas, which mainly consists of methane) and in tank ships known as LNG carriers.

Test version of a carbon fibre storage tank for liquid methane and liquid oxygen designed for BFR rockets. Source: SpaceX

SpaceX company has announced that it will use methalox, a rocket fuel consisting of liquid methane mixed with liquid oxygen (acting as an oxidant), in its planned Mars exploration mission. The company has developed the methalox-powered Raptor engine. The newly designed BFR rocket is to have seven such engines, along with fuel tanks capable of carrying 240 tons of liquid methane and 860 tons of liquid oxygen. Liquid methane has a density of about 423 kg/m³, which means that the tanks of the BFR rocket can hold about 567 m³ of this substance. The amount of liquid methane that could be stored in the LNG terminal in the Polish port city of Świnoujście would fill as many as 500 BFR rockets.

Not only in the outer space

Besides its use in space travels, methanation also has a lot of more ‘down-to-earth’ applications. The reaction is widely used in power-to-gas systems, which allow storing electric power surplus in the form of methane.

Another important feature of Sabatier reaction is its capability of transforming carbon dioxide into water and methane. The excessive emission of carbon dioxide to the atmosphere is considered the main cause of the current climate change. We can imagine a technology that would allow direct conversion of carbon dioxide produced as a result of combustion (for instance, in a coal-fired power station) into methane as a result of Sabatier reaction. The produced methane could be supplied to households. In that way, methanation process could possibly help to reduce CO2 emission and slow down the climate change.

Before creating a Mars fuel station capable of producing methane and filling rocket propellant tanks with this substance, prototype installations of this kind have to be first built and tested on Earth. It should be noted that such technologies as the Sabatier reactor can be used not only to explore the space, but also to help us survive here on Earth.

 

The original Polish text at www.nauka.uj.edu.pl was first published, in a slightly different version, on the blog Science - Technology - Future.

Polecamy również
Ambassador of Sri Lanka visits the Jagiellonian University

Ambassador of Sri Lanka visits the Jagiellonian University

Scientists continue to increase their knowledge of virus biology

Scientists continue to increase their knowledge of virus biology

Project co-authored by JU MC student awarded in the Direction: Space competition

Project co-authored by JU MC student awarded in the Direction: Space competition

Ambassador of Iceland visits the Jagiellonian University

Ambassador of Iceland visits the Jagiellonian University

Widok zawartości stron Widok zawartości stron