Imagine if there were hundreds of "startups" aiming to sink stuff for some reason to the bottom of the Mariana Trench. Sure, doing that is difficult and fun to think about from a science fiction perspective, but the bar to show how such a thing could be useful is and should be quite high.
I asked GPT to give me the 5 most compelling space startups created since 2020. Here's what it gave me:
* Space refueling
* Getting things back from space more cheaply
* Removing space debris
* Getting things to space more cheaply
* Microgravity life sciences
Of these, only the last one is an actual product. The others are just picks and shovels for nonexistent products. And, I don't see why microgravity life sciences requires the ability to deploy unlimited quantities of crap to low-Earth orbit.