Updated: Nov 27, 2022
1. Settore bellico e spazio
Currently, space is unarmed. There are no weapons deployed in space or on the ground (in the air, at sea or on the ground) intended to attack space objects, such as satellites. Nor are there any satellite weapons deployed against terrestrial targets. Space is used for communications, surveillance and targeting on battlefields; for weather forecasting; for mapping and positioning military assets; for early warning of missile and air attacks; and for general military, economic and technological intelligence around the world. Thus space is 'militarised' even if not yet 'armed'. However, even countries like India - which has no history of military activity in space - have begun to enter the field, when the Shakti Mission was launched on 27 March 2019. India's test illustrates the dilemma faced by many space-faring countries: should they act independently and aggressively in this arena to protect their interests, or should they put their trust in international forums to try to contain the current space arms race?
Space weaponry poses two major threats. First, it poses a security threat, as unilateral actions by countries to arm space increase uncertainty within the international system. For example, some space researchers have recently warned that the proposal to establish a US space force increases the risk of conflict and exacerbates tensions with its rivals. Secondly, it poses an environmental threat, since anti-satellite weapons experiments have led to the creation of large amounts of space debris and increased the difficulty of conducting near-Earth operations. If the process of weaponizing space were to accelerate, space could become dangerous and less accessible to actors who would make commercial and scientific use of it.
2. World leaders' approach to the militarisation of space
The United States, Russia and China constitute the three main space superpowers: they have independent capabilities to develop, launch and control satellites for all space orbits and manned space programmes. The medium-sized space powers are the European Union, India and Japan, which have the capabilities to independently develop, launch and control advanced satellites but do not have a manned space programme (India plans a manned launch in 2022, ESA in 2021 launched a new call for 5 astronauts). Diplomatically, the United States consistently opposes treaty proposals such as the Prevention of the Placement of Weapons in Outer Space and of the Threat or Use of Force against Outer Space Objects (PPWT), expressing concern over its ambiguity in defining the concept of 'space weapon' and its lack of confidence in the intentions of Russia and China. At the UN General Assembly on 1 November 2021, US representatives declared: 'We will explore and use outer space for the benefit of mankind, and ensure the safety, stability and security of activities in outer space'. The US prefers that the domain of space remain conflict-free, yet it has repeatedly noted that both China and Russian Federation have aggressively developed and deployed technologies designed and intended to extend future conflict to outer space, he said. "Therefore, empty and hypocritical efforts such as the PPWT, which cannot be confirmed or verified by the international community, are not the answer."
The European Union has also opposed proposals by China and Russia to limit space weaponry, arguing that these proposals are neither clear nor sufficiently comprehensive. In contrast, the European initiative for a code of conduct for outer space activities, which would be legally non-binding, received support from the United States during President Barack Obama's term, which weakened after President Trump took office. Under President Biden, the US position on this issue has essentially been confirmed, with no desire to make "major structural changes".
Since 2008, the European Union has been leading this initiative to write a code of conduct for space activities with the aim of breaking the deadlock in the debate on space weaponry. Although the European Union's actions are intended to limit space weaponry, they also constitute its attempt to emerge as a central actor setting the regulatory agenda in this arena, as part of a broader approach to the importance of protecting space assets.
Russia and China are competing to become the main super-power in space and, together with the USA, are experiencing an escalation in technological supremacy, not least because they are three of the few countries with A-SAT (Anti-Satellite) military capabilities. Russia recently carried out an A-SAT test that put the ISS at risk. Other countries that are not normally considered protagonists in the space race are also trying to close the gap with the superpowers.
3. Are there other threats besides the human one?
The development of the military space sector has fueled a debate that has long fascinated experts, scientists and the merely curious: are we alone in the Universe? As science fiction as it may seem, since we cannot rule out the possibility that intelligent life has developed on other Earth-like planets, and since we have no data to base ourselves on the typical development of an intelligent species, we can only use the comparison with the human species to define the way in which an intelligent civilization typically progresses and expands.
Taking a first look at human history, it is already clear: we are dangerous. Not only to other species but also to ourselves. Our human nature has driven us to conquer every corner of our planet and soon we will be looking to the stars, both to expand our domain and to secure access to ever greater resources. And then we may come across others trying to do the same thing. Competition for life is also likely to take place on distant planets, so it is logical to assume that an alien civilization that came to dominate their planet would be similar to us in some ways. But if they are similar to us, they can also be dangerous. None of this means that conflict is inevitable. So far, the progress of the modern world seems to have made us more peaceful, not more violent, and perhaps this is true for other civilizations as well.
The existential problem we are facing is that if (or when) we encounter others among the stars, we have no way of distinguishing between those who are peaceful or aggressive and what their real intentions are. Furthermore, if we were to discover another civilization or vice versa, the light years that would separate us would mean years of delay in communication.Both sides would be in a state of uncertainty, wondering if the wisest move is not to just attack, because of the first strike advantage. If your opponent is light years away, sending an invasion fleet takes so long that by the time it arrives the technology used may be obsolete.It follows that war between civilizations might be a compulsory choice to remove an existential threat to oneself by eliminating the other. If we assume that most civilizations live on planets all you have to do is launch something huge at a planet to make it uninhabitable. Thus, the ultimate weapon of interplanetary annihilation is probably something like a Relativistic Kill Vehicle, a kinetic or nuclear missile fired at a planet at a significant fraction of the speed of light, already theorized by both Chinese and American research. This is not such an absurd idea - a civilization only slightly superior to us on the Kardashev scale (you can read the original paper here) would have enough energy to send multiple attacks against any planet it suspects of harboring life. What makes these weapons so sinister is how much they favor the strategy of attacking first, since they would be so fast that it might be impossible to protect oneself effectively against them once launched.Conflicts between civilizations might not be long affairs, but rapid situations in which the first to fire wins. This makes any civilization an existential threat to any other.
For now, however, there is fortunately nothing to worry about: it is unlikely that anyone has noticed humanity yet. The radio signals we have transmitted over the last 100 years have travelled a relatively small distance and have long since decayed into unreadable noise. At our technological stage, if we do not actively try to get noticed and if no one specifically observes our rather unremarkable solar system, we will remain hidden. But one day we will venture into space in a serious way, and we will have to consider these kinds of questions again.
The major superpowers are already considering what to do in the event of close encounters of the third kind, and the international community has also envisaged measures, albeit not very detailed ones, lacking any precedent. For example, through the establishment of UNOOSA, a UN body with the aim of promoting international cooperation in the peaceful use and exploration of space, assisting all UN member states to establish legal and regulatory frameworks to govern space activities.
So far, the great powers seem to be more focused on achieving technological supremacy in space, both in order to be the first to take possession of the nearest resources, as soon as the necessary funds and infrastructures are in place, and in order not to risk falling behind other states in satellite technologies, which, in addition to the observation and study of space, also involve the observation of the Earth and the acquisition of data, even extremely important and secret data.
The other countries, with the exception of powers that are trying to establish themselves (including Japan, Canada, Australia, India) can be divided into three categories: those who want to reap their benefits from the commercial (and peaceful) exploitation of space; those who are not yet ready to effectively enter this sector and tend to abstain from these discussions, at least at UN level; those, on the other hand, such as North Korea, India, Iran, Venezuela, join the position of countries like China and Russia in not wanting to manage the development of this sector in space at international level, a position they express by voting against it in UN Assemblies.
 The 'Treaty on the Prevention of the Placement of Weapons in Outer Space and of the Threat or Use of Force against Outer Space Objects' is a proposal that China and Russia have been putting forward to the United Nations since 2008. The proposal has come under constant criticism for its ambiguity when it comes to the definition of space weapons.  Peoples, 'The Securitisation of Outer Space,' 11-14.  Max M. Mutschler and Christophe Venet, "The European Union as an Emerging Actor in Space Security? "Space Policy 28, no. 2 (2012): 4-6.  Phillip A. Slann, "Anticipating Uncertainty: The Security of European Critical Outer Space Infrastructures," Space Policy 35 (2016): 8. Travel between stars is much slower than the speed of light; therefore, it takes much longer than simple communication. And during this time, the technological level of spacecraft is unlikely to improve. Their capabilities are 'frozen' at the moment of departure. This is a real problem if the spacecraft are a military fleet hoping to beat an adversary, as they will continue to improve their technology during that time. If we send an invasion force advanced enough to defeat an alien civilisation 50 light years away, and it is travelling at 10% of the speed of light, then it may be hopelessly outmatched when it arrives. The alien civilisation's level of technology may only improve by 1% year on year, but this is enough to make it 144 times more advanced by the time the spaceship arrives. Here is the calculation to be made: assumption of 1% annual technological improvement = multiply by 1.01. After 2 years, 1.01 x 1.01 = 1.0201 which is 102.02% or 2.01% better. So after 50 years, we get 1.01^50 = 1.64463 and after 500 years, 1.01^500 = 144.772. But why 500 years? Because Time = Distance/Speed = 50 light years / 0.1 speed of light = 500 years. Because it travels so close to the speed of light, it packs an incredible amount of energy. At 95% of the speed of light, each 1 kg of mass has a kinetic energy of 1.98*10^17 joules. A 63 kg projectile would have about 1.25*10^19 joules, which corresponds to the output of all the nuclear arsenals on Earth You can make your own relativistic energy calculations using the calculators you can find here: http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/releng.html The equation he uses is as follows: RKE = Mass * C^2 * ((1/(1 - B^2)^0.5) - 1) Con: RKE = Relativistic Kinetic Energy Mass in kg C = speed of light in m/s B = the fraction of the speed of light at which the bullet travels Perez, Cristina L., and Jeffrey O. Johnson. Vulnerability assessment of a space-based weapon platform electronics system exposed to a thermonuclear weapon detonation. No. ORNL/TM-12487. Oak Ridge National Lab., TN (United States), 1994. De Aquino, Fran. "Relativistic Kinetic Projectiles." (2013).  Due to the fact that a warning signal travels at the speed of light, whereas a 'classical' Relativistic Kill Vehicle (RKV) only travels close to the speed of light, a signal would be slightly faster than the rocket. Assuming that an RKV, fired from a civilisation 50 light years away, flies at 99.9% of the speed of light, a signal that could warn us would only reach us between two and three weeks before impact. That might be a little short to protect the Earth from annihilation. You can try out different scenarios using a simple formula: distance = speed of light * time (s = c * t).  This is what we have been doing for many decades, for example in the context of many SETI programmes (SETI = Search for Extraterrestrial Intelligence). In general, many SETI programmes focus on detecting any kind of signal from outer space (called 'techno-signals' or 'techno-signatures' by some people), such as the current 'Breakthrought Listen' programme: Breakthrought Initiatives (2021): About: https://breakthroughinitiatives.org/about Quote: "Breakthrough Listen is a $100 million programme of astronomical observations and analysis, the most comprehensive ever undertaken in search of evidence of technological civilisations in the Universe. The partners with some of the world's largest and most advanced telescopes, across five continents, to survey targets including one million nearby stars, the entire galactic plane and 100 nearby galaxies at a wide range of radio and optical frequency bands."  In 1901, Guglielmo Marconi confirmed the first transatlantic radio transmission. The radio signal traveled out into space and was reflected back into the ionosphere, a part of the Earth's upper atmosphere. #Belrose, J.S. (1995): Fessenden and Marconi: their differing technologies and transatlantic experiments during the first decade of this century. International Conference on 100 Years of Radio, pp. 32-43.  Now, let's ask ourselves "what is the smallest signal we can detect compared to noise? In general, you will be dealing with the cosmic background radiation, which varies with frequency - but a good approximation is to assume that it is at 3 degrees Kelvin and uniform in all directions: Boltzman's constant is 1.38E-23, so multiplying that gives about 4E-23 W/Hz/m^2 or -224 dBW/Hz/m^2. So, at one million km, the radio station is 53 dB louder than the background noise. So, let's move further away - it goes like an inverse square, so if we move by a factor of 1000, a billion (1E9) km from the earth, the radio station is now -231 dBW/Hz/m^2, which is below our noise by about 7 dB. This would make it very difficult to detect. Now, if you wanted to make a signal that could be detected easily, you would make a very narrow band transmission - Above, I assumed the radio station was essentially random noise with 10kHz BW. If we only transmit a narrow carrier (<1 Hz wide), then we take another 40 dB. So, at a billion km, we are now at -191 dBW/m^2, compared to -224 dBW/m^2. If we go into the Kuiper belt, where things like Pluto are, we are at 6E9 km, and our signal is another 15 dB weaker (-206 dBW), but still detectable. Out to 200 AU (3E10 km), we start to get closer - the signal is -220 dBW, and the noise is -224. But, if we go out as far as Proxima Centauri, 4.4 light years, or 4.16E13 km (which is about 41.6 trillion km), the signal has faded to well below background noise.  In addition to the 'step back and listen' approach mentioned above, one can also simply follow the 'shout it out loud' route (so-called 'active SETI'). For this purpose, messages are sent into space that are specifically addressed to extraterrestrials. One of the first and probably the best known radio messages of this kind is the 'Arecibo message', sent in 1974. At first glance, it seems like a riddle, but this message contains basic information about humans such as DNA, numbers or our location. It is sent to the star cluster M13 about 21,000 to 25,000 light years from earth. #SETI-Institute (2021): Arecibo Message: https://www.seti.org/seti-institute/project/details/arecibo-message There is a huge scientific debate about active SETI. In a nutshell, we are saying "Hello! Here we are!" to a civilisation that is probably hostile to us. #Musso, P. (2012): The problem of active SETI: An overview. Acta Astronautica, Vol. 78, pp. 43-54: https://www.researchgate.net/publication/256935145_The_problem_of_active_SETI_An_overview. Quote: "The main objection against the idea of transmitting messages from Earth always was, and still is, that, while passive SETI is surely not dangerous for us, active SETI may be, since ETs could be malevolent."
Saperstein, Alvin M. ""Weaponization" vs. "Militarization" of Space." APS Physics & Society Newsletter (2002).