Realistic Science Fiction: What did Interstellar/the Martian get wrong?

[RainDreamer]

10 hours ago, Temstar said:

If you could make a SSTO like that you wouldn't make chemical rockets any more. It would be a bit like car makers hauling cars to the dealership using horses instead of trucks to save petrol.

In the context of the story, they probably don't want to do that because they have to minimize number of launches, and don't want to send another refueling launch after. NASA at that point became an underground organization after all, and launches have to be done mostly in secret. The resources on earth are dwindling too, so they might reuse old boosters to save cost.

[Temstar]

Nah its not a matter of resource, at the end of the movie they had baby Rangers coming out of their ears, presumably each equipped with one of those magical fusion engines.

Single stage delta-v to change your velocity by two digit percentage the speed of light and then back is an unimaginable amount of energy. I'll say it again if you could make that engine in mass (and they did with those tiny rangers) you wouldn't need to manipulate gravity to lift space colonies - you'll just attach some of those engines to the bottom and shoot it up like a giant rocket.

[KAL 9000]

Yeah, no kidding. I believe the baby Rangers are called Vipers.

[KerbonautInTraining]

Time to nitpick The Martian!

The MAV ascent/rendezvous me a bit disappointed. 

Why on Earth did they have to take manual control? Couldn't they have computers on the Hermes fly it for them?

Given that he took lots of weight out of the capsule, the acceleration would have been pretty close to nominal during the first stage and peaked during the second stage. 12 G's?! What sort of mass ratios we talking here? I'd assume a normal ascent would peak at less than 2 G's.

Today's inertial guidance systems could EASILY surpass an accuracy of, what, 20m/s? Total delta v of ~5km/s means an error of about 0.04%. Even an Apollo Era IMU could do better.

Why not plan for an intercept roughly a few hours after ascent? It would have given a lot of time for course corrections and velocity matching. Wouldn't have to blow the ship up, either.

I refuse to believe they used up any significant portion of their RCS propellant during a burn lasting <10 seconds. Such a short burn would impart a miniscule delta V unless their RCS thrusters happen to consist entirely of Space Shuttle Main Engines.

I can't bring myself to pick at the 'Iron Man' propulsion, it was just too perfect. 

Don't get me wrong though, I LOVED The Martian. (I got to impress a couple people by predicting they'd use a gravity assist. )

Edit: Is it just me or did the font size change a few times between paragraphs? I'm typing this on mobile so I can't actually control font size. 

Edited December 18, 2015 by KerbonautInTraining