Many may wonder that the fastest object ever built/ fastest object that traveled was a Bullet. Some educated people think that the fastest objects are spacecrafts which travel at 11.2 km/sec and many suggest that these objects need that kind of speed to travel vast distances like the projects which aimed at exploring beyond solar system. But Interestingly, the fastest spacecraft ever built weren't headed out of solar system at all but towards the Sun.
Helios Probes I and II
'Helios probes' are a pair of probes which are sent by NASA two years apart from each other i.e. one in 1975 and another in 1976, to study conditions close to the Sun for a period of more than 10 years.
To maintain stability their orbits around the Sun was kept elliptical and when they swing past the Sun at the closest approach, these probes reached speeds of over '70 kilometers per second' i.e. over '2,50,000 km/h'.
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This project was led by 'NASA' along with 'Federal Republic of Germany' and were launched from JFK space center at Cape Canaveral. These probes went into orbit and completed the primary missions successfully by the early 1980's but these probes were active till 1985. Till today these probes are still in the orbit around the Sun and are no longer functional.
'Helios probes' have set a notable maximum speed record at '2,52,792 km/h' or '70.22km/s' making it by far the fastest man made object ever built.
'Helios 2' flew close to the Sun in 1976 at a recording distance of '0.29 AU' or '43.432 million kilometers'.