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Psawhn
Jan 15, 2011


zandert33 posted:

Although the trailer does provide some spoilers, I don't think it's that crazy. It really only touches on things that happen in the first half of the book, it's not that bad.

Yeah, I agree. Even though those who've read the book will recognize scenes from throughout the entire book, to anyone else they're context-less "Explosions! Rockets! Drama!"

Those cuts which are obviously spoilers (Pathfinder, Hermes' mutiny and rescue ) are actually misleadingly edited so don't actually spoil anything that much of importance.

Even then, I can't wait to see the movie in all its glory.

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Psawhn
Jan 15, 2011


hmmxkrazee posted:

Quick book question:
Was Hermes going to go to Mars regardless whether or not the probe resupply on the Earth flyby was successful? I thought if that failed the rescue mission would just be cancelled. What was the point of the plan where the rest of the crew would commit suicide leaving Johannsen (?) to survive?


Disco!?


Keeping book spoilers under wrap until we learn the spoiler rules on the book.

The crew of Hermes committed to the Rich Purnell Maneuver months before even getting to Earth. Because the ion engines thrust so slowly, if the Hermes was going to stop at Earth it would usually have needed that much time just to slow down, decelerating the whole way. They sped up, instead, so by the time the resupply mission even launched the fastest way to stop at Earth really would have been via Mars no matter what.

Psawhn
Jan 15, 2011




I am bad at gifs.

Anyway, I have a very nerdy and question about the final -esque action scene in the book. The better audience for this is probably the spaceflight thread, but I didn't want to CIA document FOIA with black bars over everything over there.

On their missed rendezvous to Watney they were going to miss him with a relative velocity of 11 m/s at a closest approach distance of 68 km, 39 minutes after the Ares 4 MAV finished its burn. They had about 30 m/s dV of RCS fuel and an unlimited dV (for our purposes) of ion engine at 2 mm/s/s. My experience tells me that that kind dV for the rendezvous is plenty, especially because they're traveling on an escape trajectory out of a planet 5x bigger than Kerbin so orbital mechanics doesn't come into play. At the very least, they could cancel out the 11 m/s relV at closest approach, then use the remaining 20 m/s of remaining RCS fuel to inch closer to Watney, arriving an hour or so later.

But the best way to adjust rendezvous is to burn as early as possible, as soon as they realize how badly they're going to miss. I mathed out that a 15 m/s RCS burn immediately, (at an angle 59.6 deg away from Watney), followed by turning on the ion engine for 43.35 minutes, then turning the ion engine around and firing the other way for the remaining 43.35 minutes, then a braking RCS burn of 11.8 m/s (at an angle of 51.1 deg away from relative velocity), will rendezvous Hermes to Watney at 0 m/s relV, only about 48 minutes after the book does. Is my math correct? Is the main reason Andy Weir wrote the existing sequence of events (complete with blowing the airlock for ~30 m/s dV) because he doesn't play KSP enough?

Psawhn
Jan 15, 2011


I rationalize that in my head as imagining he left his USB with his own music/TV on Hermes. Because they were only going to be on Mars for only a month and they'd be busy with surface ops he could go without it, and he didn't want to risk leaving it on the surface and going the whole 6 month-long voyage back missing it all.

Psawhn
Jan 15, 2011


Terrible Horse posted:

The commander still had her chair thrusters to stabilize them.

One thing that bugged me was that they let Beck go outside the Hermes without a tether. Nothing came of it but for a movie that emphasized real processes and being safe, it seems insane to send the guy just climbing along the outside of the ship and hope he doesnt slip.

Even better, he didn't need to do anything at all. The whole reason he needed to climb around the outside of the ship in the book was because the airlock doors weren't automated and they wanted to blast a hole in the inner airlock door, not the outer door. In the movie they had motorized doors they could control from the cockpit.

Psawhn
Jan 15, 2011


I agree that, in real life, as soon as they found out Watney was alive there'd be somebody running the numbers of how soon they could get Hermes back to Mars, and the Rich Purnell maneuver would be on the table from the get-go. I didn't mind it for the movie, though, of which one reason is that constant-thrust ion drives are non-intuitive enough, and orbits are finicky enough, that the answer to the question "Can we do a gravity assist?" is often either "No" or "Not for a few years."

Here's an article about genuine mission planners talking about The Martian's courses:
https://www.insidescience.org/conte...ht-martian/3251
Turns out the post-Earth-slingshot trajectory puts the Hermes within Venus' orbit, which is pretty scary from a solar radiation perspective.

Psawhn
Jan 15, 2011


Such disastrous storms are probably so rare in-universe that the best plan probably could be "hope one doesn't happen, and if it does, abort." If the cost of designing and sending five MAVs that could survive such 1-per-1000 year storms would be greater than the cost of simply sending an extra MAV, then don't bother. If it gets tipped due to a freak storm, they'd either delay Hermes' launch until a new MAV gets to Mars or, if Hermes was already on its way when the MAV gets wrecked, pass right by Mars and try again next time. Worst that can happen is a freak storm while they're on the surface, and note that they already had pre-set abort limits for wind speed; Lewis scrubbed the mission really quickly, it just turned out the thresholds were too loose. (Obviously Ares 4 and 5 will have set even stricter tolerances for dust storms.)

Psawhn
Jan 15, 2011


I think I've read some of that bulk in modern EVA suits is micrometeorite protection, which Mars' atmosphere is still thick enough to protect against.

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Psawhn
Jan 15, 2011


NotJustANumber99 posted:

Also he seems to have some big botany book with him? Or is that just his own CV? That would be odd.

That's probably his mission experiments plan or activity schedule or something. A big binder with a billion procedures and checklists for his parts of the mission.

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