Comment by Scarblac
According to the first Google hit, https://scitechdaily.com/nasas-parker-solar-probe-the-fastes... , the fastest we've made so far went 430k mph (falling towards the sun), or about 0.064% of c. Good guess.
According to the first Google hit, https://scitechdaily.com/nasas-parker-solar-probe-the-fastes... , the fastest we've made so far went 430k mph (falling towards the sun), or about 0.064% of c. Good guess.