Chain mail for rockets, or protection in a grid

A program developed by Russian scientists under support from the International Science and Technology Center (Project 1917) helps to protect spacecraft from orbital debris that rushes at great speed, in the most effective and economic manner.

The system, under development by Russian scientists with financial support from the International Science and Technology Center, effectively and economically protects spacecraft from meteoroids and orbital debris. First tests, conducted by the researchers in the laboratory and on special test grounds, have confirmed their reliability.

The odd-sounding word “meteoroid” is not used here by chance. A meteorite is the luminescence brought about by the combustion of a meteoroid. And a meteoroid is a small solid celestial body, impact with which at times threatens the lives of the crew of a spacecraft.

However, it is not meteoroids that present the greatest threat to spacecraft, but so-called orbital debris, as a rule – metallic pieces of cosmic waste of a technogenic origin, that travel at times at great speeds, up to 16km a second, and which could easily penetrate the shell of a spacecraft or orbital station. One could say that humans have already dropped enough litter in space to make the trash out there a threat to themselves of no small consequence. It has reached such an extent that special protection is now required. And perhaps this protection is precisely that which the specialists from the State Research Institute of Aviation Systems RSA, the Institute of Applied Mechanics and their colleagues from several other Russian research institutes are now developing.

The idea of protection from such high velocities of impact was proposed by the American researcher Fred Whipple, back in 1947. Rather than making the shell ever thicker, he proposed that a screen be placed in front of it. The orbital debris will of course break through it, but it would itself be turned to dust.

But over the years the cosmic trash pile has grown larger and the sizes of space modules have also increased; accordingly, so has the mass of the Whipple protection. Yet the delivery of each kilogram to near-Earth orbit incurs costs exceeding ten thousand US dollars.

The solution proposed by the Russian scientists is directed towards increasing the effectiveness of the protection while reducing its weight. This is how the authors propose the implementation of their idea.

They believe that it should first be defined for which sections of a spacecraft or space station the risk of damage from orbital waste debris is the greatest and for which the risk is lowest. A correlation should be made of the direction of motion of the spacecraft, the direction of motion of debris, expected velocity of impact, probability of rupture, and so on. In other words, an understanding should be reached as to the level of protection that would be optimal for each section of the spacecraft. This means defining the number of “levels” (“floors”) of protection required in place and at what interval they should be placed between one another, thus ensuring there is no unnecessary clutter, while providing the required level of protection. It also means the selection of the material from which certain sections of the protective screen should be made. It is the program developed by the authors that can calculate all this.

The second part of the work is to devise the materials for the various sections of the protective screen. “Together with a modified Whipple protection, multi-level, solid screens, we propose the use of cellular screens,” explains scientific project leader Mikhail Kononenko. “They are lighter than solid screens and with the correct selection of thickness and material of wire from which such screens are made, they are no less stable than solid equivalents.

“Furthermore, the object that is flying at speeds of over 5km/sec, will inevitably break up on impact with the screen. But our screen is not only a passive barrier. It should actively mill the orbital debris and promote the expansion of the cloud in a transverse direction. This is a so-called concept of semi-active protection, or a mechanical-chemical means of protection.

“We propose the application of a special substance onto the surface of the protective grid – its composition is not being discussed in open print. However, the essence lies in the fact that the energy from the impact leads to a chemical reaction between this substance and the source of the impact. Energy is produced in an instant and gaseous reaction products, like in a micro-explosion, spread the impacting particle into a literal cloud of dust, which for the shell of the spacecraft is in comparison quite safe”.

The authors have to verify the effectiveness of the developed protection here on Earth. At the test site aluminum pellets of 1cm in diameter are fired at a screen, made from the material of the potential protection. The pellets are fired from a special cannon, with which the pellet can reach a speed of over 7km/sec. The project authors have already completed the first tests, which have proved successful, with the protection coming into action as required. The computer program, under development by the scientists, enables, using all these varied materials, the reduction to a minimum of the total mass of the protection, without detriment to the efficiency. So in future craft will fly to the Moon and to Mars with a new protection, made with the support of the ISTC.

It is interesting to note that last year at the international conference “Systems and Technologies for the Future Study and Assimilation of Cosmic Space”, Neville Mazwell from the California Institute of Technology, NASA-Jet Propulsion Laboratory, Pasadena, USA) said that, in his opinion, the greatest problem now facing science as a whole, and of space research in particular, lies in the fact that we have to explain to the taxpayers why such huge sums of money are pumped into this research. Why is it actually necessary for people? Mikhail Kononenko, who also took part in this same conference, has his own answer to this question. “To question Nature and achieve new knowledge is becoming an ever more expensive pursuit for individual countries. However, projects such as the ISS, and space research as a whole, are able to unite nations, force them to see themselves not as representatives of isolated nationalities, at times at odds with others, but as people living on the same, relatively small and very fragile, planet.”