Bard spotting on Bluesky 08 November 2024

Ms. Penny Oaken, SkyWitch (@skywitches.net):

So far the "hard sci-fi" criticism I have of The Expanse (outside of the Dark Matter realm physics of the macguffin) are two things,

1. Epstein drive (minor, no big deal)

2. interplanetary railguns accurate to what must be incredible fractions of arcsecond. (Major, sucked me out of suspension)

Curt Gebers (@curtgebers.bsky.social):

Is that any higher aiming accuracy requirement than the Hubble Space Telescope?

Ms. Penny Oaken, SkyWitch (@skywitches.net):

Telescopes have the benefit of image composition & stabilisation over multiple collections, in post.

Railguns don't.

It can be addressed by attitudinal thrusters in the projectile & a guidance system …

Curt Gebers (@curtgebers.bsky.social):

They can stack images for sure. But as I understand it (and I could be wrong about this), the Hubble takes up to 45 minutes of continuous exposure for a single image, and it has to hold the field of view perfectly still on the image sensor for that entire time while it orbits the planet every 95 min

Ms. Penny Oaken, SkyWitch (@skywitches.net):

To think of it a different way -

The star being observed is emitting a huge number of photons, millions of which (despite being a near infinitesimal fraction of its output) happen to be arriving at our telescope. We get lots of catch chances.

A rail gun, otoh - just one launch chance.

Ms. Penny Oaken, SkyWitch (@skywitches.net):

The smallest perturbation in velocity, angle, even the heat expansion of the track, can affect whether it reaches the intended target

Ms. Penny Oaken, SkyWitch (@skywitches.net):

The advantage of rail guns is that they allow a very, very high kinetic energy. They still have the same drawbacks as say, firing a .50 cal, with respect to precision.