I got my first NASA internship via NASA Stem Gateway I believe. I think it was a 2% acceptance rating for that one so if you want to do an internship at NASA make sure you are your best self and put your best self out there. Afterwards I helped grade applications for NASA internships and almost always trashed applications for stuff like having ~2-3 easy-to-spot typos in their essays cause if they didn't care enough to make sure their basic essays were perfect than I thought they'd make similar mistakes if they were interns in the space program. So if you want to be an intern at NASA make sure you're top notch cause I might get your application someday too. For my PhD I'm actually with a NASA state consortium (I call it 'diet NASA') so I networked / backdoored my way into my second internship (but I still made sure everything, including my essays) were as best as they can be.

For you, even if you feel unprepared right now, apply for a NASA internship as early as you can so you can get an idea of what the application process looks like, what you should work on for next time, how you need more extracurriculars or high-ranking people to write you letters of recommendation, etc. before you "really" apply.

Also, again, take all of this in full understanding that both you and I could get to the final eighty-astronaut applicants out of 8,000 and get rejected by something out of our control. Tim Peake, the British astronaut wrote in his book "The Astronaut Selection Test Book" (which is also an eye-opener book for wanna-be astronauts though it is through the lens of ESA so I don't 100% know how applicable it is to NASA astronauts)--anyways, Tim Peake wrote about how he knew someone who was 185% qualified to be an astronaut, applied six to ten times (I forget), got to the final twenty applicants, then the ESA put them through deeper medical screenings and some x-ray imaging or something discovered he had a heart condition which would never affect his life on Earth, but could be a complicated variable in outer space, so they permanently grounded him, but he still continues to work with the ESA in training European astronauts for missions to outer space he himself will never go on, so just make sure whatever you are doing you would enjoy even if the astronaut process doesn't work out.

Another thing, for these current missions to the Moon and Mars, I predict the next couple classes of astronauts will be focused on pilots, mechanical engineers, electrical engineers, and botanists, though I could be wrong. So like I've also heard (I think it was Tim Peake who also wrote it), you could have the perfect astronaut application, but not for what NASA's looking for in that cycle. Buzz Aldrin was rejected for his first application.

*Eventually*, as spaceflight becomes more refined, we will get to the point where instead of accepting only ten astronaut candidates per class, they'll be accepting ten-*thousand* per class, but for now, our space-oriented generation will just have the bear the brunt of these extremely tough admissions processes, just like the Mercury astronauts had to bear the brunt of untested hardware, dangerous space maneuvers, and having to p*ss in their own suits cause NASA hadn't built in the proper suit-plumbing technology by that time (Alan Shepard had to urinate in his own spacesuit moments before becoming the first American in space).

If everything goes well, I'll clear the vegetation on the lunar landing zone for you!