Why is mining asteroids difficult?
Mining on asteroids is a fantastic, for now, type of activity, which has recently been often spoken of as the near future. Only the companies that were aiming for such an occupation almost went bankrupt, having never reached a single asteroid. Let's see why it is so difficult.
An asteroid is a small cosmic body of natural origin, from several meters to hundreds of kilometers across, of predominant stone or metal composition, which distinguishes it from comets, where the main material is ice. The icy bodies of the solar system are mainly located far from the sun - beyond Mars and beyond, so it’s easier to get to asteroids from Earth. Most of the asteroids rotate in the Main belt, between the orbits of Mars and Jupiter, but a large part has orbits close to Earth or even crossing Earth's orbit. Relatively close to Earth or approaching asteroids are called near-Earth, and crossing the orbit are considered potentially dangerous to us. But achieving such asteroids with the help of spacecraft is much simpler, some asteroids can be reached by spending less fuel than in flight to the moon.
The composition of asteroids is also different, scientists divide them according to the spectral classes defined in telescopes from the Earth. There are three main types of asteroids: stone, iron-stone, metal (iron). The richest in various metals, including rare earths and platinum - metal, which are fragments of the nuclei of the first protoplanets formed and destroyed in mutual collisions at the dawn of the solar system. Some subspecies of stone asteroids contain more carbon and volatile compounds including water, which makes them similar to comets.
Any space miner, going hunting for asteroids, must choose a target for several reasons:
- Spectral class - to know what minerals are waiting there (it is useless to fly to a metal asteroid with a water production system).
- The difference in orbital speed with the Earth is to know how much fuel will have to be used for a round-trip flight. The difference between the speeds of the Earth and passing near-Earth asteroids starts at about 0.5 km / s. That is, to reach the asteroid and return to near-Earth orbit, the spacecraft will need a fuel reserve that will allow it to pick up speed of 1 km / s (0.5 km / s for acceleration and 0.5 km / s for braking). For comparison, a reach of 3.5 km / s is required to reach and land on the moon. You can save by gravitational maneuvers, but they will require an optimal trajectory and can significantly increase flight time. You can also save on braking in the atmosphere, but you will need to increase the mass of the returned capsule.
- Asteroid orbital inclination - both the Earth and asteroids rotate around the Sun in approximately the same plane, but even a small difference in orbital inclination requires significant fuel consumption. Approximately 0.5 km / s of speed increase is required to change the orbital plane of the spacecraft by 1 degree, and some asteroids rotate at an angle of up to 20 degrees to the plane of the Earth’s orbit.
As a result, only a few dozen asteroids are available for a relatively simple and inexpensive achievement and return of the extracted material. Even so, each kilogram of resources will cost tens or hundreds of millions of dollars spent on the development, production and launch of a mining spacecraft.
The most annoying thing for "space miners" is that asteroid material already regularly arrives on Earth in the form of meteorites. In addition, the Earth itself contains the same composition of chemical elements as the surrounding cosmic bodies. True, in metal asteroids, the concentration of heavy rare-earth metals is higher than the average in the earth's crust. Earth refers to bodies that have undergone differentiation, as a result of which heavy elements descended to the core, and only light ones remained on the surface, and metal asteroids are just fragments of ancient protoplanets. But here volcanism comes to the aid of earth miners. The results of ancient eruptions, such as the kimberlite pipes of Yakutia, the Conder Rangeor the Putorana plateau contains an increased concentration of metals, which mankind can still mine for hundreds or thousands of years.
Thus, in the coming decades, the commercial prospects of mining in space can be discussed only in the context of their use in space, without delivery to Earth.
Attempts to make money on the search for new asteroids also failed, since asteroids successfully open state scientific institutions, including NASA, at a budget expense.
The difficulties in achieving asteroids, and the availability of meteorite material on Earth, and most importantly - the lack of real needs of the Earth’s economy and astronautics in space material, have become the reasons for the lack of business interest in such projects as Planetary Resources and Deep Space Industries. The extraction of rare earth metals on Earth, despite all the difficulties, is orders of magnitude more efficient and easier than space miners could provide.
Prepared for the popular science portal Nplus1.ru , published in the original edition.