Hey, it’s Star Wars. Parsecs are considered a unit of time. You can almost here Lucas say, “Hold my dunce cap.”
I notice stuff like this all the time. It is not me wanting to be a jerk or a nerd. It is not something I can turn off. But it can spoil a lot of films for me if the tale is not told well enough for me to suspend my belief and just enjoy it.
Correct physics does not make good cinema. If your drive jets mass out of the back to push you forward, it can probably throw a projectile. The drive is probably your biggest gun. If you are attacking something, you would do this at extreme range, and not like a Star Wars biplane dogfight. Shoot, move position, then wait a month for the bullet to arrive. It would be nice to see it done right just once, but the film might be a bit slow.
Explain nothing. Remember how ship stopped in ‘Dark Star’? There was no deceleration - they went from whooshing through the stars to motionless. My reaction was “They can’t do that!” followed closely by “Hang on - we didn’t object when they were accelerating. It may look like magic, but it is consistent.” If you have to tell a lie, make it a big one. Don’t try explaining ‘the force’.
Tell a good story. The first Star Wars had Space Princesses, Death Stars, Star Destroyers with clear ‘up’ and ‘down’ directions like battleships, and ‘The Force’ woo. Any of these would normally have spoiled it for me, but it was good enough and I stayed with it. But imagine Star Wars without Alec Guinness in it - I suspect it would have crashed and burned for me without him.
Earth ammunition has its own oxidiser. Gunpowder has potassium nitrate. If you had a cannon and used a flint or hot iron at the touch-hole, it would work in space. Yarr!
The Expanse is incredibly good with that sort of thing. They have weapon systems that take days or months to impact, ballistic weapons are almost entirely used to destroy incoming missiles rather than attack other ships and they are automatic turrets stationed all along the hull rather than big naval guns. Missiles are basically small spacecraft that can navigate on their own and, for example, stop and lie in wait for weeks if necessary. Railguns need thrusters to counteract them, etc.
It’s a very thought-through world. And of course it only takes place in our solar system (-ish, but that’s spoilers) so there’s no FTL or relativistic weirdness.
The Kzinti Lesson- a reaction drive’s efficiency as a weapon is in direct proportion to its efficiency as a drive.
Plus, of course, a spaceship with an autopilot is a reasonably effective weapon in its own right if you don’t mind losing the ship (and the autopilot doesn’t have ethical subroutines).
Taken together, I can imagine a setting where there isn’t much point banning weapons on spaceships, as the ship itself is just as dangerous…
A column by the arse* Jeremy Clarkson this week (no link - it’s behind a paywall) mused on the alleged reporting of US ‘hunters’ and other gun nuts now signing up for trips on ships off Somalia in the hope of coming across some ‘pirates’ and letting rip. Clarkson suggests most of these people are probably US dentists unable to shoot lions these days without too much bad publicity, so shooting Somalian pirates at sea suited them better.
*arse - his official title. He is the world’s biggest.
And many sci-fi stories (esp. those I read in decades old issues of Analog magazine) also have the aliens and are often clearly parables of European invasion of the US and its impact on the then natives.
This thread made my day. So many great insights in here.
I’m a sucker for the hardest of hard sci-fi and the more of the issues raised in this thread that are addressed, the more I like it. Current faves include The Expanse, Firefly, and Mote In God’s Eye.
Somewhere along the way I read a great article that makes the case that space combat will never exist. I can’t find the article now because people like to write around these topics so it’s lost in a sea of pop science articles about “why sci fi is wrong”.
The crux of the argument was this (as alluded to by others already)- space is too big. So so much bigger than any of us can ever hope to conceive. Even in orbit around the same planet, two ships could never even find each other. In interplanetary space? Forget it. You would spend your entire life moving between planets and never see another ship en route, even assuming shipping lanes of some sort. They made a good case.
The other issue not yet raised here is orbital mechanics. Nothing in space moves in straight lines. It’s all orbits. Changing orbits is incredibly expensive because altitude (from the thing you’re orbiting) equals velocity, and acceleration or deceleration cost a lot of energy. Even if you know where another ship is (perhaps spacedar or whatever), just trying to match each other’s orbits to have any kind of interaction is very difficult and expensive. The energy consumption would be immense, and combat would require imagining some energy source so immense that every ship somehow has ten suns in it.
Even a guided missile could never hit anything. It would take weeks of travel time, assuming your target was in a steady state (ie. basically trying to let you hit it) and you somehow knew where it was, the fuel consumption to try and match orbits would never be worthwhile. The energy would be way better spent meeting those people at their destination and doing your fighting there. Fighting in space would never make economic sense.
The bottom line of the article was that combat is not cost effective at best, and physically impossible at worst.
Oh, come on! Moonraker showed us just how it will work. 
/s
It’s far more destructive to not closely match the orbits, but just match the positions at an instant of time and let the difference in velocities do the damage.
The context here is not matching orbits as you would for a docking maneuver, but to create any kind of interaction or intercept at all. You have to change your orbit to do this. A lot. Whatever orbit you need to intercept the target, it’s not the one you are on, and it’s by definition very far from the one you are because space is so big. So getting an intercept orbit will never be cost effective or perhaps even possible if the target is trying even a tiny amount to not be intercepted.
And as for meeting at the destination you would need a lander customized for each planet. Differences in local gravity and atmospheric density govern all aspects of the vehicle’s shape, type of rocket nozzle, perhaps the propellant type too (wouldn’t want your rocket exhaust to be hyperbolic with the local atmosphere).
Essentially the space-saving vehicle would have to design and build each lander enroute assuming they don’t have detailed info prior, but information has a speed limit too.
Assuming chemical rockets and non-usage of aerospikes
It depends. If a spacecraft is doing a flyby of a planet, having it target a point on the surface or on an orbit around the planet is not very expensive.
In retrospect, that line makes absolutely no sense. If I were Neo, when I saw the Matrix, I would have said, “Why didn’t you just tell me?”
Do you think he may be over-compensating for something?
I like realism as much as the next person, but I don’t think slow (and boring) works well in a movie setting. Besides I think a lot of how this is viewed is through our lens of current physics. What if we invented a drive that could open, essentially a wormhole or jump point through space? If we had that technology why not a miniature black hole? Then just couple the two and you can jump a black hole bomb right next to a ship or planet.
I think there are lots of questions here, but usually I just end up enjoying the pew-pew in space.
It must be column envy.
