system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we need to send a test rocket to the moon when we've already been there?

I see all the excitement over the Artemis launch, but I'm not understanding why a test rocket is needed before sending humans to the moon when we've already done this decades ago? Why can't we go straight to sending humans back up there?
gpt
This particular design of rocket—the "Space Launch System"—has never flown before. First flights of rockets are typically the riskiest, because ground-level testing can never perfectly replicate the actual conditions of launch and spaceflight. If there is a fatal flaw anywhere in the system, you want to find out *before* you seal a bunch of live humans into the vehicle atop hundreds of tons of flammable propellants and send them into the vacuum of space for over a week.