u/MiamisLastCapitalist

https://nss.org/the-colonization-of-space-gerard-k-o-neill-physics-today-1974/

I wanted to write a space opera with good scientific realism. My universe has no FTL.

A major gigantic piece of world building was going to be that aliens gave us advanced propulsion-technology to more easily reach ultrarelativistic speeds, so we can travel between our colonized star systems at nearly but not quite lightspeed. Time dilation high jinx ensue. And I think I have a really neat idea for how to do this too. So I sort of have my own version of a Lighthugger. Cool.

Only... I found 2 problems with this the more I learned and the more I thought about it.

1 We kinda don't need it.

You can reach ultrarelativistic speed with dyson swarm style solar collectors or stellasers. It may take many kilometers of foil mirrors, but when you've got robotic automation and millions of small metallic asteroids to choose from that's not difficult. The sun has ample energy to spare to beam people up to ultrarelativistic speed with photon pressure alone on the regular. It's not quite as exciting as having an engine but scientifically pretty solid as far as sci-fi goes. Whether or not we choose to spend that much of our solar budget on getting ships up to 99% c vs a more modest 30% c though is another story.

2 I can't find a reason for the aliens to give us something that cool.

At first my rational was that the aliens would basically license this propulsion technology to us, becoming something like the Spacing Guild from Dune. The tech would be totally black-boxed and they'd still be in control of it, they'd just be our space-ubers. It even gives them a measure of soft-control over us by making us dependent on them. Modern geopolitics proves its better to control someone economically than militarily.

Only... The aliens can get what they want for much cheaper, really. They are aloof and mostly benevolent, they honestly want to study and interact with us because intelligent life is rare and precious in the universe. Which is all fine, but they don't need to give us super-engines to get our cooperation on that. They could just whisper some modest tech tips to us once in a while and they'd already be improving us. "Pssst, try getting fusion this way." "No no, you don't want to configure AI that way, trust us." We really don't have any leverage on these guys. We couldn't stop them from collecting data on us if we wanted too. Just the fact that they'd be willing to trade any knowledge with us at all is generous. So why would they give us some incredible clarketech super-engines to go hog wild across the stars with?

So... What do you all think I should do?

Should I embrace the hard-scifi beam sail answer, or is there another logical reason the aliens would give us super-drives for our ships? Or maybe one of you mad lads has an entirely different perspective I should consider.

EDIT: A bunch of you are suggesting reverse engineering, which is a maybe... I don't think something this advanced is something humans could make, however it could possibly have certain von neumann qualities to it. So I'll pin that as one possibility.

https://x.com/BryanLarsenArts/status/2043701206099611787/