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I've seen a lot of questions about the $\Delta V$ required to reach the Sun from the Earth (~22-30 km/s if I remember correctly), firing a bullet into the sun, etc.

But has this ever happened? Has any object launched into space from Earth deliberately or accidentally gone into the sun and never come out? I.e. being engulfed by a solar flare and surviving doesn't count. The expectation is that the object would keep falling deeper into the sun until it disintegrated.

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    $\begingroup$ "Has any object launched into space from Earth ... gone into the sun and never come out?" Could anything (except photons) go into the Sun and then come out? $\endgroup$ – RonJohn Sep 9 '19 at 18:48
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    $\begingroup$ @RonJohn I've submitted an edit to remove the word "permanently" from the title, since it accomplishes nothing but confusing people who read it. $\endgroup$ – Monty Harder Sep 9 '19 at 21:46
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    $\begingroup$ @peterh If you just want to drop something into the sun, starting from earth you need about 21.78km/s. See e.g. here: space.stackexchange.com/questions/38604/… $\endgroup$ – Polygnome Sep 9 '19 at 22:53
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    $\begingroup$ @MontyHarder "the title [... confuses] people" [citation needed]. I put the word "permanently" in the title to prevent language lawyers from claiming objects like MESSENGER or Mariner 10 have been in the sun. $\endgroup$ – CJ Dennis Sep 9 '19 at 23:18
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    $\begingroup$ @EricTowers good point on neutrinos. Would a black hole go into the Sun, or would the Sun go into the BH? Ditto neutron stars? $\endgroup$ – RonJohn Sep 9 '19 at 23:55
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No, not yet. The Parker Solar Probe became the closest ever artificial object to the sun on October 29th, 2018, surpassing Helios 2 which held the record since 1975 [1].

No other human-made object has been closer to the Sun. The probe will repeatedly touch the outer corona until mission end in 2025, with the closest approach being 3.83 million miles [2]. It will then lose altitude [sic] control and will end up as debris field around the sun, while parts of it may fall into the sun in the next few billion years [3].

The spacecraft reached the low perihelion by repeated gravity assists from Venus.

References:

  1. https://en.wikipedia.org/wiki/Parker_Solar_Probe
  2. http://parkersolarprobe.jhuapl.edu/The-Mission/index.php
  3. https://www.telegraph.co.uk/science/2018/08/09/nasa-probe-will-still-circling-sun-end-solar-system-say-scientists/
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    $\begingroup$ "It will then lose altitude (sic) control..." needs a source, there might be a possible mission extension unless you're sure that that's scheduled and inevitable. $\endgroup$ – uhoh Sep 9 '19 at 8:16
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    $\begingroup$ @uhoh I've included a link to an interview with the program manager of the parker solar probe as reference for that. $\endgroup$ – Polygnome Sep 9 '19 at 8:21
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    $\begingroup$ I'm pretty sure "altitude" should be "attitude" in that article. $\endgroup$ – JohannesD Sep 9 '19 at 16:46
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    $\begingroup$ Once it runs out of propellant and/or its reaction wheels fail loss of attitude control is inevitable. Components hiding behind the sun shield will get slagged down when exposed to direct solar radiation; but anything burned off I'd expect to be blown away in the solar wind. To fall into the sun, drag during its passes through the Corona would need to be sufficient to de-orbit the remnant. Is drag actually strong enough to accomplish that it was the interviewee speaking figuratively? $\endgroup$ – Dan Is Fiddling By Firelight Sep 9 '19 at 17:53
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    $\begingroup$ @DanNeely I think drag is not enough for that. It will be still $\approx$ 3 solar diameter away, and the solar atmospheric density decreases exponentially. After the loss of attitude control, the probe will quickly die, later starts to rotate. Probably its tungsten shield will last the longest, it is hard to calculate, when will it fully evaporate. Possible, that it is will survive until billions of years (note, it will heat only until $\approx$ 2000C, and tungsten melts at 3400C). $\endgroup$ – peterh - Reinstate Monica Sep 9 '19 at 22:03
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It is not possible for a probe to go accidentaly into the sun, the necessary delta v could not be reached by accident. A two stage rocket is needed for an Earth orbit, about 8 km/s delta v. About 22 km/s for an Earth to Sun trajectory would require about 5 to 6 stages with a delta v of 4 km/s per stage. Such a rocket was never build.

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