system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why is it going to take NASA until the 2030s to get humans to Mars?

Do we not know what is needed to actually make this trip happen yet?  If we already understand the technology needed to accomplish such a task, then why is it going to take another 16+ years to do it?
gpt
>Do we not know what is needed to actually make this trip happen yet?

Not really. Keeping people sufficiently healthy for the full trip is really hard. Launching a craft, either all at once, or piece by piece for orbital construction, is a really big feat that requires some pioneering. 

Keeping a closed-system livable for the full duration is also quite a stretch, especially since there can't be real-time communication with ground-control to be walked through time-critical tasks.

We'd also generally want to have better engines for the transfer craft for the shortest trip possible to prevent problems from various things.

>If we already understand the technology needed to accomplish such a task, then why is it going to take another 16+ years to do it?

Even with understanding it'd take years to design workable systems, prototype and test them, maybe even field-test them in space, select astronauts, train them, select backup astronauts and train them, review everything countless times to ensure it's functional and up to spec, revise things to meet power, time, fuel or other limitations, test the revisions, etc.

Plenty of people think 2030 might be a bit optimistic without significant budget... and even then there are those that'd call it a bit far-fetched.