what is its part in spaceflights?
There is a brief delay from the source to the receiver, which becomes more noticeable as distances increase; was significant for communications between ground control and Apollo 8
Speed of light
Similarly, communications between the Earth and spacecraft are not instantaneous. There is a brief delay from the source to the receiver, which becomes more noticeable as distances increase. This delay was significant for communications between ground control and Apollo 8 when it became the first manned spacecraft to orbit the Moon: for every question, the ground control station had to wait at least three seconds for the answer to arrive. The communications delay between Earth and Mars can vary between five and twenty minutes depending upon the relative positions of the two planets. 
who discovered the speed of light in a vacuum Witelo what is the numerical value of it? As a dimensional physical constant, the numerical value is different for different unit systems. how important is it in the field of physics? It is independent both of the motion of the wave source and of the inertial frame of reference of the observer. were there any experiments conducted to discover something faster than light? Yes, but they do not travel fast than light who did such experiments? UNANSWERABLE
wiki:19581023
Speed of light [SEP] Spaceflights and astronomy
NASA must wait several hours for information from a probe orbiting Jupiter, and if it needs to correct a navigation error, the fix will not arrive at the spacecraft for an equal amount of time, creating a risk of the correction not arriving in time. Receiving light and other signals from distant astronomical sources can even take much longer. For example, it has taken 13 billion (13) years for light to travel to Earth from the faraway galaxies viewed in the Hubble Ultra Deep Field images. Those photographs, taken today, capture images of the galaxies as they appeared 13 billion years ago, when the universe was less than a billion years old.