We might one day combine tardigrade DNA into our own cells.
One method is epigenome engineering and would target genes advantageous for space. Another method is to combine the DNA of other species (i.e. tardigrades) with human cells to make humans better fit for space.
Could well be needed. It's not fully understood, but human space travel - even to the surface of relatively nearby Mars - might not even be viable. Aside from the radiation issue after leaving the Earth's magnetosphere, zero gravity changes the body. When astronauts land they're carefully assisted to get out and placed onto soft bedding. From Chris Hadfield's autobiography, merely standing up after coming home from a few weeks/couple months on the ISS was like standing on a bed of needles. It took about 2 weeks to be able to move around again, which makes me wonder how we'll ever get people on the surface of Mars. The Moon is pretty easy in comparison, much lower gravity and not that far away.
The complexities involved, even with solutions, are just too much for current humans. Genetically engineering ourselves could work, though I'm more in favor of just digitizing ourselves ha.
there's no construction material in outer space. Therefore, no or few spare parts. Everything that's lost (think leaks) can only be replenished after 6 months.
artificial gravity?
has to be self-sustaining and able to develop and grow.