It turns out that Starfield has a hidden, but surprisingly robust support for spacewalking - and all you have to do to unlock it is type a few commands into the in-game console.
Footage of a Starfield player leaving the bounds of their ship and flying around an asteroid field recently drew tons of attention over on the game's subreddit, and it's easy to see why. Here's something that isn't technically possible in the game being done in such a convincing fashion that it looks like an official expansion pack or a particularly robust mod.
But it's neither of those things, as Reddit user WeirdConcern4666 explains - it's just a matter of inputting two Starfield console commands. Just apply 'player.setpos x 10' to move yourself outside of the ship and 'setgravityscale 0' to turn off gravity. (If you haven't previously used console commands, be aware that they only work on PC and will disable achievements.)
With those commands entered, the game's existing zero-gravity controls take over and let you fly around as a proper space explorer. The only real indication that this is a kind of janky hack is the fact that you won't instantly die if you take off your space suit. You can even walk on asteroids if you activate gravity.
This is just a novelty for now, but the fact that the game supports spacewalking to this degree already certainly suggests that future Starfield mods will offer much more robust takes on the concept. Never underestimate the Bethesda modding community.
Official Starfield modding support is on the way next year, according to Todd Howard.