Is it possible to maintain a connection with space probes that are far away by sending other space probes behind it. For example -

[earth] ------1---- 2-------3--------4------5....and so on if required (it depends on the distance from earth)

These 1,2,3,4, 5 are space probes and they are supposed to pass the command given to them to the next probe?

My question is that, is it possible to navigate or maintain a connection with the last probe in that way?

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    $\begingroup$ Yes, theoretically. It hasn't been done yet, but Breakthrough Starshot is investigating it as a possible way to make lightyear-scale communication with nanosats easier. $\endgroup$ – Deimophobia Jun 5 '17 at 18:25
  • $\begingroup$ Regarding gravity, mass doesn't change trajectory - a smaller probe has a smaller force due to gravity, but also has less inertia and changes direction more easily, so it will have the same trajectory as a larger probe. However, it's lower inertia means that the same booster will accelerate it to a higher velocity, than although this improvement becomes less relevant as the mass of the probe compared to the booster becomes negligible. $\endgroup$ – Deimophobia Jun 5 '17 at 18:28
  • $\begingroup$ @Deimophobia thanks for the answer. $\endgroup$ – user8278 Jun 5 '17 at 18:34
  • $\begingroup$ @Deimophobia... If a small probe is compared with a larger probe, (both having the same boosters) which would travel fast? $\endgroup$ – user8278 Jun 5 '17 at 18:35
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    $\begingroup$ Related: space.stackexchange.com/questions/9984/… $\endgroup$ – 1337joe Jun 5 '17 at 19:22

That wouldn't be a good approach, for a number of reasons, but I'll focus on power here.

The strength of a signal drops off proportionally to the square of the distance, so probe #1, at half the distance, would have to transmit 25% of the power as the Earth to have the two signals be the same strength at probe #2. It's a lot easier to put a big transmitter on Earth, where we can plug it in to mains power, than on a spacecraft where it has to be powered by the solar array or RTG.

Putting some numbers to this, the Deep Space Network can send 20 kW, compared with a few 10s of Watts on a spacecraft.1

(The DSN also has 70 m diameter dishes, which allow the power to be concentrated into a much narrower beam than a spacecraft antenna does, giving the ground station an even greater advantage.)

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    $\begingroup$ Worth noting: this holds true for distances of scale of the solar system plus some. When it comes to distances of order of a light year, a series of relays may be better than a single, powerful source. (still, they'd need pretty strong power sources, and these, being heavy, are hard to accelerate to speeds that would cover light years in any reasonable time.) $\endgroup$ – SF. Jun 6 '17 at 22:39

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