What if future spacecraft used the stars as GPS?

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In a prepublication, an astronomer proposes an interstellar navigation system based on the triangulation of stars. In short, it is a kind of space GPS. This proposal comes as NASA thinks it can use pulsars for its vessels like ships with lighthouses.

A questioning of the idea of ​​NASA?

In 2018, NASA unveiled an equivalent of GPS for space navigation taking pulsars into account (see image below). Recall that pulsars are neutron stars emitting a strong electromagnetic radiation in the direction of their magnetic axis and capable of rotating very quickly on themselves. According to the US agency, this would guide robotic spacecraft to the outer reaches of space as part of missions impossible for humans to achieve.

Credit: NASA’s Marshall Space Flight Center / Flickr

In the Solar System, it is possible to transmit control signals from our planet as is the case for probes. However, things get complicated from the moment we pass the heliopause, that is to say the limit where the solar wind from the Sun is stopped by the interstellar medium. The time for sending and receiving signals then becomes too long. This turns out to be a major obstacle as part of journeys to the depths of space.

The idea of ​​NASA is therefore to use an X-ray system to find one’s bearings with pulsars. Coryn AL Bailer-Jones, astronomer at the Max Planck Institute, believes, however, that the dispersion of pulsar signals in the interstellar medium could be the source of errors concerning their measurement. The precision, essential for successful navigation, would then be too low.

Adaptive triangulation

Coryn AL Bailer-Jones detailed another solution in a pre-post to the platform arXiv. He believes that we should be based on the stars that we already know while taking into account parallax, aberration and the Doppler effect. These three effects cause the position of stars and their speed to change as we move away from the Sun. To put it simply, the astronomer offers adaptive triangulation throughout the trip.

In his report, the researcher is based on an experimental model to say that from about twenty stars, it is possible to measure the position of a vessel at three astronomical units near and its speed at 2 km / s. However, the greater the number of stars integrated in the triangulation, the more the precision increases. The astronomer finally recalls that his study is mainly conceptual, because interstellar travel is still impossible to envisage in the short and medium term. The fact remains that it is all the same a concrete research axis.

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