Ad Astra: Flaws and Fixes. SPOILER-PALOOSA!

[KelvinZero]

MASSIVE SPOILERS. No need to use the spoiler tag here.
(subtitled: why don't script writers just come here to get their science sorted out?)

The goal is Flaws, but also Fixes.

I would like to go through the flaws, but also focusing on how they could be fixed with minimal alterations and budget. I saw a bunch of flaws that were also irrelevant to the plot, explanations that were unsatisfactory but also unnecessary, things that could have been pared away and actually make the movie tighter.
    Other things are integral, such as the Grand McGuffin at Neptune. How would you deal with that? (My feeling is that every movie is allowed one.. but don't give bad explanations if no explanation, an admitted mystery, would be better.) .. but I also had some thoughts about possible better explanations.

[KelvinZero]

One of the most blatant and straightforward was:

At the end he uses the nuclear blast to push his ship back home. Just don't do that. There was no requirement that he had any shortage of fuel, no big plot reason. Nothing. If you want tension then he still had to get to his ship and get to a minimum safe distance.

Also I think it would have been interesting to see an accurate simulation of what a nuclear blast would do to that local portion of a ring.

There was also some apparent nonsense about one ship being parked on one side of the rings and the visiting ship on the other. Was that nonsense? I can see how a low thrust electric propulsion vehicle could have trouble getting past a ring.

This also raises a lot of questions I have always had about rings that I would love to have explained graphically, how they would really appear up close.

Although rings are bunches of rocks in space it seems to me they probably have very low velocity compared to their neighbours. They can't all be bashing into each other at orbital velocity all the time.

Could a ship get mired in a ring without getting bashed to bits? I could imagine it gathering a snowy ring sort of like those saucer-shaped moonlets that form in the rings of saturn. What are the particles in rings like anyway? Are they dense lumps of ice or super fluffy crystaline things?

If a ship was mired say a few 10s of km into a ring then the journey to and from it would be quite interesting. A ship would have to park further out in the same plane, (or you would have to visit and leave within half an orbit) I imagine you would travel very slowly in over what locally would look like an infinite plane. A tiny bit of thrust occasionally would keep you "above" the plane. You might even be able to travel out again hopping with a spacesuit.. depending what the relative velocities you are likely to encounter really are.

There was a great opportunity for them to explain to us what a ring actually is, up close.

[Martin.cz]

There was also some apparent nonsense about one ship being parked on one side of the rings and the visiting ship on the other. Was that nonsense? I can see how a low thrust electric propulsion vehicle could have trouble getting past a ring.

Well, the same ship has enough TWR to fatally slam someone to bulkhead just by activating its engine (unless there were two high thrus booster stages, not just one). Also for the ridiculously short transfer times (Moon->Mars in 19 days, Mars->Neptune in 79 days) it simply needs to have a reasonable amount of trust to achieve & break the speeds needed.

But still, lets say you don't want to maneuver too close with a bulky space ship next to effectively an unstable antimatter time bomb. Still you likely want to tethter your rocket pod at the destination or else it will predictably float out of your reach forever.

Also using a sensible approach speed when docking or landing would not be a bad idea - every time a ship attempts to dock or launch in this movie it makes the Falcon 9 hoverslam seem like a slow motion movie.

This also raises a lot of questions I have always had about rings that I would love to have explained graphically, how they would really appear up close.

Although rings are bunches of rocks in space it seems to me they probably have very low velocity compared to their neighbours. They can't all be bashing into each other at orbital velocity all the time.

Could a ship get mired in a ring without getting bashed to bits? I could imagine it gathering a snowy ring sort of like those saucer-shaped moonlets that form in the rings of saturn. What are the particles in rings like anyway? Are they dense lumps of ice or super fluffy crystaline things?

If a ship was mired say a few 10s of km into a ring then the journey to and from it would be quite interesting. A ship would have to park further out in the same plane, (or you would have to visit and leave within half an orbit) I imagine you would travel very slowly in over what locally would look like an infinite plane. A tiny bit of thrust occasionally would keep you "above" the plane. You might even be able to travel out again hopping with a spacesuit.. depending what the relative velocities you are likely to encounter really are.

There was a great opportunity for them to explain to us what a ring actually is, up close.

These are really good points! Given how many particles are there and how little external force is normally acting on them - basically just any nearby Neptune moons, light pressure and collision with other particles - then any other force, even very small, could lead to interesting interactions.

I can imaging the Lima being parked there for so long possibly acting as a very small shepherd moon, possibly creating a detectable gap in the rings as well as some material potentially accreating on it.

As for exploring the rings with a space suite or a pod, I wonder what the effect of reactive propulsion would be in the ring particles. Even cold gas thrusters have (according to Google ) an exhaust velocity of ~600 m/s and some of that gas molecules will impact the ring particles. This could result in nothing at all (particles being too big or extra energy damping out via collisions) to spectacular with visible "wawes" in the dust stream and possibly more complex interactions. As for exploding a nuclear bomb next to a bunch of antimatter inside of Neptunes rings - seems like a perfect submission for the next round of New Horizons mission proposals. ;-)

[KelvinZero]

As for exploring the rings with a space suite or a pod, I wonder what the effect of reactive propulsion would be in the ring particles. Even cold gas thrusters have (according to Google ) an exhaust velocity of ~600 m/s and some of that gas molecules will impact the ring particles. This could result in nothing at all (particles being too big or extra energy damping out via collisions) to spectacular with visible "waves" in the dust stream and possibly more complex interactions.

That could be really spectacular especially when the sun is behind it. I wonder if you would get prismatic effects? I wonder what confidence scientists have in what a ring really looks like up close. Im guessing they have a fantastic amount of data on particle sizes and the physics of how clumpy the particles are. Surely they have done huge simulations to see if they can duplicate the various features we have gleaned from detailed animations of saturn's rings. A rendering that actually showed us the reality a ring could be as iconic as the scientifically based black hole rendering in Interstellar. Not quite as cosmically scaled but a lot closer to home.