Guest Post – The invisible geometries of the Solar System

This is an abridged version of the article “The invisible geometries of the Solar System” by Roberto Flaibani,  first published in Italian on Il Tredicesimo Cavaliere, a blog that has already been featured in the past on The Earthian Hivemind and that is going to become a more regular source of contributions. I have included here some of its most notable parts, extensively quoting from the original, which I recommend checking out anyway; what I present in this post is just an outline, nowhere as detailed and interesting as the Italian version.


The article takes into exam something I have discussed in previous articles, namely the Lagrangian points, a set of five locations that can be found in every celestial orbit, provided that the bodies are massive enough. They are privileged location for spacecrafts, satellites, and even for captured asteroids. The focus here is specifically on the orbit Earth – Moon and its L points.

L1: Next Destination

L1 is about 60,000 km above the centre of the near side of the Moon, an ideal location for hosting an infrastructure that can serve for a number of useful operations, including the assembly of future missions to NEOs and Mars and the coordination of activity on the surface of the Moon. From L1, in fact, it is possible to interact in real time with the robots operating on the surface of the Moon, while this is not possible from Earth because of the delay of about three seconds, due to the greater distance between the two bodies. () Given to the fact that going from LEO to GEO costs more than a trip from L1 to GEO in terms of fuel consumption, using L1 opens the possibility to perform various operations in geostationary orbit. In GEO are located a large number of very sophisticated satellites for telecommunications, meteorology, espionage, and operations like maintenance, repair, recycling and disposal of scrap components could be thus been performed periodically by piloted vehicles, or robots, maybe remotely directed by an operator on the ground.”

Other locations on Earth-Moon orbits also present substantial value.

L1, L3 : strengthen the planetary defence against the dangerous asteroids


The network detection and control of NEOs, known as Spaceguard, and the nascent planetary defence system, has experienced a disturbing “blind side” in its field of view up to 2010. This is due to the characteristics of the trajectories followed by the NEO when approaching our planet. In fact, if the trajectory of an incoming NEO is outside the Earths orbit, the object will be visible in the night sky and its course easily predictable. If, on the contrary, the trajectory of its approach is internal, the object will appear, so to speak, in the daytime sky, therefore invisible to the ground-based optical telescopes. The detection will only be possible by radars and radar-telescopes, which, however, provide only short notice.”

The solution? The launch of a real “hunter of asteroids, a specialised tool that could be placed in orbit around L1, from where it will be possible to get a full view of the space inside the Earth’s orbit. Moreover, if L1 hosts the headquarters of Spaceguard, then L3 would accommodate the armed wing of the planetary defence system: batteries of missiles capable of diverting asteroids – small, but by no means harmless.”


Cool, isn’t it? But wait – it gets even better.

L1, L2 and the Interplanetary Superhighway

L1 and L2 are of direct interest to understand the so-called Interplanetary Superhighway, because they represent a special access to distant destinations. () Starships could enter the orbit around L1 or L2 (or any other Lagrangian points), although these are simply locations in space which does not correspond to any celestial body. These orbits originate a surface-shaped tube. Thus a ship with the appropriate initial speed could be launched along a trajectory that will take it around L2 of the Sun-Earth orbit (in green in the figure). The set of all trajectories similar to this forms the single tube of the Interplanetary Superhighway. Thanks to the physical properties of the tubes, whatever moves from one orbit around a planet and then flies away from it has to travel through that particular tube. A spaceship travelling a trajectory inside this pipe will go through L2 heading out of the Solar System (in blue in the figure), while one that crosses the outer tube will head to the Sun (in red in the figure). Note that the tubes are always in pairs: for each tube for approaching trajectories one exists in the opposite sense.


The spaceships can travel along the tubes but may change course by entering another tube, thanks to a small manouver possible with a common rocket engine. But there is a way to do that without any expenditure of fuel, using the natural exchange points of the Interplanetary Superhighway.

There are a few areas in the Solar System where the Superhighway could be tested: Jupiter, for example, thanks to his four main moons.

Finally, L4, L5 – the most stable  Lagrangian points of all – could accommodate entire space habitats, like O’Neill’s cylinders, Rama objects and other colonies hypotheses in the SF literature since decades – an even more exciting subject. Watch this for a nice 3D simulation:

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