•New

In the next few decades it will be possible to send a spaceship to an asteroid, capture it and modify its trajectory so that it orbits the Earth. This is confirmed by trajectory calculations carried out in Asteroidretrieval, a Marie Curie project to be concluded in May 2015 within the Seventh Framework Programme of the European Union.

Joan Pau Sánchez states that the first missions to capture asteroids could start about ten years from now. These space missions would make a slight change in the velocity of near-Earth asteroids, modifying their trajectories towards an area in space where they could be naturally attracted by the Earth's gravity. Once captured, the asteroid would be maintained for as long as necessary at the points of gravitational equilibrium between the Earth and the Sun, or moved to secure orbits around the Earth.

The work of the UPC's researchers in the Asteroidretrieval project focused, first, on using the laws of astrophysics to calculate viable trajectories for capturing asteroids with the lowest possible energy consumption. Second, they analysed the feasibility of these missions, concluding that they could start within 10 to 50 years.

The researchers Joan Pau Sánchez and Josep Masdemont of the Barcelona School of Industrial Engineering (ETSEIB) are creating models of the combined gravitational effects of the Earth, the Sun and the Moon. The next step is to incorporate these models in the design of the complex engineering systems needed in the space ships and systems used to capture asteroids.

According to Joan Pau Sánchez, in January 2015 a total of 15 candidates had been detected among the 12,000 known near-Earth asteroids. These asteroids could be captured using space propulsion technology that is available now or likely to be developed in the next ten years. Sánchez states that "the 15 asteroids are selected according to their diameter and mass, taking into account the maximum mass that can be captured with space propulsion technologies”. These small, interplanetary rocks are about ten metres in diameter and involve no risk of impact on Earth because they would burn up on contact with the atmosphere.

The UPC researchers predict that, once the project is completed, the results will be applied in a future asteroid retrieval mission. When the technology has been proven to be feasible with smaller rocks, it can be tried out on larger asteroids with a greater mass.

Some asteroids can contain up to 40% of substances that vaporise easily, such as water, methane and other liquids and gases, in addition to metals and semi-conductors. Capturing large interplanetary rocks would allow these resources to be mined for use in space and on Earth.

For example, after hydrolysis by solar energy, the water extracted could be used to fuel space ships and equipment. Water could also be used to provide shielding for ships and astronauts against solar particle outbursts and cosmic rays. The metals in the asteroids, including precious metals, may have applications in industry or in the construction of space facilities, thus making it easier to install bases for space missions and mining. The semi-conductor materials could be used for space electronics and telecommunications.

If this project becomes a reality, a vehicle could travel to an asteroid, stock up on fuel or minerals and continue to space or return to Earth with its payload of interplanetary natural resources. In fact, two companies based in the United States are already helping to finance the development of asteroid mining technology. The challenge in this field is to find a way to separate the precious metals or water from the other components.

NASA is planning a mission in the mid-2020s to demonstrate how an asteroid can be redirected. In this case, according to Joan Pau Sánchez, the US agency is still deciding what type of system to use: an inflatable bag that envelops a small asteroid and transports it with space propulsion or a robotic landing module that takes a large sample from the asteroid. Sánchez thinks that the key difference between the NASA mission and the Asteroidretrieval project is that "the first focuses on lunar orbits, whereas the second focuses on geocentric orbits, though it could also be applied to lunar orbits”. Whatever technology is used, the asteroids will have to be redirected back into space when they are no longer useful.

The research into asteroid capture, published recently in the European Commission’s Horizon magazine, is a continuation of the European Visionspace project that was initiated by Sánchez and researchers from the University of Strathclyde (UK) with the aim of investigating orbital dynamics at extremes of spaceship length-scale. When this project was completed, a Marie Curie grant funded a two-year stay by Sánchez at the UPC in order to develop the Asteroidretrieval project with Josep Masdemont.