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#201
Old 10-08-2015, 10:31 PM
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Yeah, the argument for not telling the crew is understandable. It's wrong, but it's understandable.

And the one thing that disappoints me about this movie is that the use of appropriate language might discourage teachers from showing it in schools. But if there was ever a movie that encouraged STEM education, it's this one.
#202
Old 10-08-2015, 10:34 PM
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What's STEM?
#203
Old 10-08-2015, 10:48 PM
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Originally Posted by Peter Morris View Post
What's STEM?
Science, Technology, Engineering, Math. Umbrella term for degrees and careers that are "techie" in nature.
#204
Old 10-08-2015, 11:52 PM
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Originally Posted by Elendil's Heir View Post
The Council of Elrond gag was funny, and Boromir was sitting right there! I'm impressed Teddy knew his Tolkien well enough to want to be Glorfindel.
That scene was straight out of the book, except in the book Annie's response was funnier. Dunno why they changed it. The move had her saying a tepid "I hate you all." In the book, she said something like, "Not one of you ever got laid in high school, did you?"


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Originally Posted by Mince View Post
You both misheard. It was a crushed Vicodin. The idea that "no one can stop me" implies it was something illicit, eliminating vitamins.
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Originally Posted by carnivorousplant View Post
Wife and I remember vicodin.
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Originally Posted by Dewey Finn View Post
I heard him say Vicodin, after noting that he'd run out of ketchup. And I wonder if he never ate another potato, after he returned to Earth.
Yes, he said Vicodin.
#205
Old 10-09-2015, 01:17 AM
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Saw it, liked it, haven't read the book, a few thoughts.

I heard Vicodin, too.

Thanks for the exposition, upthread, regarding the missing steps in creating water and the unteathered EVA, both took me out of the film a bit.

Would they really have let Martinez on another space flight? Especially the next Mars run.

I quite liked how they played the mission commander. I suppose some might complain she was wooden or flat, but it came across to me as a stone professional. When she gives the command to brace for impact as she's strapping herself into the EVA chair for this hail mary pass I thought, unflappable, doesn't miss fucking a thing.

Having said that, I thought the iron man maneuver was silly.

It's not unreasonable to keep the crew in the dark, esp during the early weeks, before they have something resembling a plan, or know that he's growing potatoes. Picture them imagining him starving to death day by day; we know that crew did everything right on the ground, but NASA only knows what they reported. If there were doubts or hard feelings and they festered for a year in space? Best avoided if there's no upside.
#206
Old 10-09-2015, 01:49 AM
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Originally Posted by outlierrn View Post
Having said that, I thought the iron man maneuver was silly.
The Iron Man maneuver was suggested in the book just like in the movie but dismissed outright, and they did not do that. The movie decided to go with it.
#207
Old 10-09-2015, 02:36 AM
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Originally Posted by outlierrn View Post
It's not unreasonable to keep the crew in the dark, esp during the early weeks, before they have something resembling a plan, or know that he's growing potatoes. Picture them imagining him starving to death day by day; we know that crew did everything right on the ground, but NASA only knows what they reported. If there were doubts or hard feelings and they festered for a year in space? Best avoided if there's no upside.
The upside to informing the crew is that they have lived on Mars, and have worked closely with Watney and would probably have a better sense of how Watney would react to his situation than anyone else. For example they might have figured out that Watney would try to find the Pathfinder to communicate with NASA.


Incidentally I was wondering why The Martian wasn't released on IMAX. According to this article:
Quote:
Unlike Gravity, The Martian isn't playing in Imax theaters. That's because Imax was committed to an exclusive run of Robert Zemeckis' The Walk, starring Joseph Gordon-Levitt as French artist Philippe Petit, who gained fame after he walked on a high wire between the Twin Towers of the World Trade Center in 1974.
A real pity. I am looking forward to the Walk but if I had to pick between the two I would have preferred the Martian on IMAX. It would have been nice if they could have figured out a way to give both films an IMAX release.
#208
Old 10-09-2015, 10:18 AM
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I saw it last night and loved it. I thought most of the differences between the book and the film were in the form of omissions and I didn't really mind them. The one difference that did bother me was the part where the commander goes out to get Watney using the MMU but when she gets to the end of the tether, doesn't even bother unhooking from the tether to use the MMU to go the rest of the way. Why bother with the MMU at all then?
#209
Old 10-09-2015, 10:22 AM
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Originally Posted by UncleRojelio View Post
I saw it last night and loved it. I thought most of the differences between the book and the film were in the form of omissions and I didn't really mind them. The one difference that did bother me was the part where the commander goes out to get Watney using the MMU but when she gets to the end of the tether, doesn't even bother unhooking from the tether to use the MMU to go the rest of the way. Why bother with the MMU at all then?
My impression was that the differences in the relative velocities would have made untethering to catch Watney suicidal - that if she caught him, the pair of they would have gone speeding away from the spaceship and the feeble jets in her MMU would have been insufficient to get them back to the ship.

She needed the MMU to go to the end of the tether and to stay there.
#210
Old 10-10-2015, 11:03 AM
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I loved the book, and I loved the movie. It was spectacular. So many scenes were visually quite a bit more interesting than a paragraph or 2 of text.

I especially liked how the movie contained a huge amount of details that they don't lampshade to the audience. It's there in the film but they don't make a big deal about it, it's just shown.

A few of the big ones : instead of saying "oh nutritional deficiency + no showers mean Watney is going to be in poor shape at the end of his stay", they show Matt Damon's greatly shrunken, skin lesion covered form. I found that to be a much more powerful image than him whining about how much it sucked to be stuck there for that long.

There's a different set of spacesuits for going to space versus walking around on Mars. I was actually thinking to myself that this was unnecessary but it was still super cool.

Those ladders have a power lift assist mode. It looked cool although actually it looked like you could lose a hand using it.

One question : is the Martian terrain really that dramatic? In the film, in 3d, the various plateaus and hills seem to jut out of the terrain huge dramatic distances, making finding a rover route quite a bit more difficult than it would be if the planet were flat.
#211
Old 10-10-2015, 02:45 PM
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Originally Posted by Habeed View Post
Those ladders have a power lift assist mode. It looked cool although actually it looked like you could lose a hand using it.
I thought it was a retractable ladder, and maybe not even meant to be retracted while someone was on it.

Quote:
One question : is the Martian terrain really that dramatic? In the film, in 3d, the various plateaus and hills seem to jut out of the terrain huge dramatic distances, making finding a rover route quite a bit more difficult than it would be if the planet were flat.
Stereoscopic vision only works for nearby objects. The human eye can't detect parallax between a boulder 100 yards away and the mountain 2 miles behind it. So in that sense, the 3D effect in the movie, where nearby hills seemed to pop out against distant mountains, is unrealistic.

But Mars does have a lot of dramatic terrain. This is an actual panorama taken by Curiosity (click on the image to get the full resolution image).

Last edited by scr4; 10-10-2015 at 02:45 PM.
#212
Old 10-10-2015, 04:11 PM
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Originally Posted by Lantern View Post
To be honest, the part about the crew-members not being told initially didn't make a lot of sense to me. One would expect that their relief at finding that Watney was alive would overcome any guilt they felt about leaving him behind especially if given the chance to communicate with him.
I don't know about that. For one, finding out that he hadn't died suddenly, but instead was doomed to die slowly of starvation isn't much of a relief. And that's what everyone thought at the time they chose not to tell the crew. For another, grief and emotions aren't rational. Finding out he was still alive and was going to die would send them through their grief process all over again.

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And how much work did they have anyway on the return trip? I would imagine almost everything was automated.
I bet NASA absolutely packed their days with experiments and exercise and maintenance and other scheduled tasks, just like they do for current astronauts on the ISS. Getting a person into space is so incredibly costly that every minute is used for a productive purpose if possible. I bet there are scientists on earth waiting in lines 10-deep to propose experiments and tests they could run with the extra time they had headed back (since they didn't have Martian rocks to analyze).
#213
Old 10-10-2015, 11:12 PM
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Originally Posted by iamthewalrus(:3= View Post
I don't know about that. For one, finding out that he hadn't died suddenly, but instead was doomed to die slowly of starvation isn't much of a relief. And that's what everyone thought at the time they chose not to tell the crew. For another, grief and emotions aren't rational. Finding out he was still alive and was going to die would send them through their grief process all over again.
Why would they have thought he was fated to to die imminently? The crew obviously had the means to return, and they knew that. At the time he established communications with NASA, Watney had reckoned he had at least a year (I believe) of rations (without rationing), plenty of time for them to return (I may be misrembering the sequence, but it doesn't make sense that he would undertake the relatively long and difficult chore of establishing communications with NASA before accounting his food supply). The only concern raised by NASA about the crew returning to Mars was fatigue, tedium, and possible emotional trauma (easily overcome with the resolve of rescuing a stranded crew member), not fuel, supplies, an injured crew member, a galactic storm, or an upcoming crew member's wedding. Like after finding out the truth about Watney, the professional astronaughts would have run around the bridge with their hands in the air, losing control of the ship, crashing into the moon.

Presuming he was fated to die before rescue, do you think they would have been less emotionally affected if they found out years later that he suffered and died? It would probably have been more emotionally gruelling because they would never have been given the chance to at least consider rescue options (what ifs). Grief and emotions are rational; sometimes our reactions to them are not. But nothing in the context of the movie (haven't read the book) suggests that the crew....anyone....thought returning in time was impossible. I understand time later became an issue when his crops died.

Last edited by Mince; 10-10-2015 at 11:16 PM.
#214
Old 10-11-2015, 12:29 AM
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Originally Posted by Mince View Post
Why would they have thought he was fated to to die imminently? The crew obviously had the means to return, and they knew that. At the time he established communications with NASA, Watney had reckoned he had at least a year (I believe) of rations (without rationing), plenty of time for them to return (I may be misrembering the sequence, but it doesn't make sense that he would undertake the relatively long and difficult chore of establishing communications with NASA before accounting his food supply). The only concern raised by NASA about the crew returning to Mars was fatigue, tedium, and possible emotional trauma (easily overcome with the resolve of rescuing a stranded crew member), not fuel, supplies, an injured crew member, a galactic storm, or an upcoming crew member's wedding. Like after finding out the truth about Watney, the professional astronaughts would have run around the bridge with their hands in the air, losing control of the ship, crashing into the moon.
At the time that NASA made the decision, no one had any idea that the crew could get back to Mars. That was the whole point of the Rich Purnell maneuver - that he figured out it was possible for them to accelerate toward Earth, slingshot around the planet (picking up more supplies on the way), and head back to Mars.

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Originally Posted by Mince View Post
Presuming he was fated to die before rescue, do you think they would have been less emotionally affected if they found out years later that he suffered and died? It would probably have been more emotionally gruelling because they would never have been given the chance to at least consider rescue options (what ifs). Grief and emotions are rational; sometimes our reactions to them are not. But nothing in the context of the movie (haven't read the book) suggests that the crew....anyone....thought returning in time was impossible. I understand time later became an issue when his crops died.
They undoubtedly still would have been emotionally affected when they came home. But they would not have been in the middle of piloting a spacecraft home at that point.
#215
Old 10-11-2015, 01:20 AM
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Originally Posted by ENugent View Post
At the time that NASA made the decision, no one had any idea that the crew could get back to Mars. That was the whole point of the Rich Purnell maneuver - that he figured out it was possible for them to accelerate toward Earth, slingshot around the planet (picking up more supplies on the way), and head back to Mars.
By "...no one had any idea that the crew could get back to Mars." you have to be referring to time. But how much time passed between the crew leaving Mars and Watney's first message to NASA? Certainly not more than a year (or I misunderstand the movie), and Watney estimated he had a year of food, without rationing or potatoes. And he must have known how much food he had left when he first contacted NASA because he would have determined that first, long before he underwent the lengthy task of contacting NASA. Why would anyone think they'd could not return in time?

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Originally Posted by ENugent
They undoubtedly still would have been emotionally affected when they came home. But they would not have been in the middle of piloting a spacecraft home at that point.
But my point about professional astronauts not acting like bumbling idiots upon hearing adverse news? They're trained to navigate space, colonize Mars (essentially), and return home. I think they'd perform ok under a bit of emotional pressure.

Last edited by Mince; 10-11-2015 at 01:25 AM.
#216
Old 10-11-2015, 03:24 AM
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Originally Posted by Chronos View Post
The one thing that I thought they got actually WRONG about the science was the mission coming back early. In reality, you don't really have options on your launch window for interplanetary missions. An early abort-to-orbit like they showed would have resulted in the crew waiting in Mars orbit aboard the ship for their window, and then coming back at the same time that they were planning on anyway. Was that addressed in the book?
As someone else mentioned, the Hermes did appear to be using some type of solar electric ion thruster; however, the discussion of using Hohmann transfer orbits and the timeline of the transfer suggested discrete impulse, not any kind of continuous thrust. There are cycler trajectories that allow faster and more frequent flybys between Earth and Mars (but not low enough delta-V to enter into orbit) but these are generally well out of phase with Hohmann transfer orbits. Since no details of the Hermes propulsion capabilies were presented in the film it is difficult to know just how much of a trajectory modification the vessel was capable of making to achieve a Mars return, but it does appear to be kind of a punt to allow for the dramatic tension of having Watney recovered by his crew.

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Does anybody know if it's accurate that one could take off in an open-air capsule like he did in a thin atmosphere like Mars, and not get hurt by the smallest speck of sand that he'd intercepted once he got up to orbit? Don't spacecraft take damage all the time from tiny random particles coming in at large relative velocities to the craft?
Although Mars atmosphere is not inconsequential for aerodynamics (in fact, it is the most difficult solild body in the Solar system to land upon owing to the thin but existent medium), for ascent barely any protection would be needed. The orbital velocity required is much lower, and if I recall correctly at max-Q the dynamic pressure is somewhere around 50 psf; enough to blow you off your feet if you were standing up, but not enough to injure someone through an EVA suit or shear limbs.

More problematic is that the MAV seems to have no propulsive capability--not even attitude control--after ascent booster burnout, and thus is tumbling. This really makes no sense, especially since the entire crew goes down to the surface. It also doesn't make much sense that they wouldn't have accounted for potential variance in the rendezvous calculations and planned the trajectory accordingly. No reason was given for the propulsive shortfall and no discussion of off-nominal performance, so the last minute 'Hail Mary' pass of blowing an airlock to eject the ship's air came off as being highly contrived.

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Originally Posted by scr4 View Post
What expenses? I think the rocket used for the first (failed) resupply launch was already being assembled for a future (Ares 4?) pre-supply mission. The Chinese rocket was already being assembled for their Mars probe. NASA employees don't even get overtime pay. They did have to modify 2 probes, but that cost should be miniscule compared to the whole ARES program cost.
There is still the cost of labor and mission planning, which is considerable. And contrary to your statement, NASA employees can get overtime as approved on a by-project basis. It is true that many programs do not authorize overtime pay and employees (and sometimes contractors) work unpaid overtime; nonetheless there is cost with any change in mission planning and operations. However, in a situation such as this, the public relations impact would be justification for nearly any cost. It isn't as if this would be at the expense of other critical funding for Medicare or disaster relief, and still probably a pittance compared to the overall expense of the program.

This does beg the question, however, of the apparent lack of contingency operations. Had the MAV fail to function (which is one of the major reliability drivers in studies of the NASA Design Reference Missions) it appears the crew would have had neither an alternate ascent method or contengency for a longer surface stay until replacement supplies arrived. This is a real problem in actual mission studies with no clear solution other than fully redundant ascent capability or a large surplus of supplies, but the problems they had keeping one astronaut alive would have been multiplied by a factor of six (at least) had the MAV failed to launch, and yet they appeared to have no thought toward the contingency. For that matter, they seemed to be doing little in the way of contingency studies for resupply trajectories, whereas in reality there is substantial effort put into contingency operations thoroughout all phases of planning. (That scene in Apollo 13 with engineers scrambling to figure out how to connect the CSM lithium hydroxide canisters to the LM systems? That was all worked out well in advance with the expectation that the LM could be used as a lifeboat.) The scale and capabilities of the Hermes also seem a little discongruent. It is clearly large enough to house a crew at least twice the size; perhaps this might be in support of future missions, but it still begs the question of why only a single six person crew was sent instead of multiple crews going to multiple ground destinations (which would be more cost effective) or backup crews in case of a primary failure.

There are a few other minor issues I have stemming from a more particular knowledge of Mars mission studies or differences between some of the geologic features in the film versus reality, but nothing that can't be explained as decisions made to improve the narrative and visual presentation. For the most part, the technical details were respectably accurate. My biggest complaint is how rushed the film is, and how it necessarily had to skip over many potentially interesting details and operations on the Hermes and back on Earth. The story could easily have spanned an eight or twelve hour miniseries rather than a two-plus hour film. The thing that really threw me out while watching the film weren't the techincal details but the the ultra-modern appearance of both Houston mission control and especially JPL, which in reality looks like a college campus that hasn't seen significant renovation since the early 'Eighties. I did like the nice touch, however, that a crewed mission had to rely on JPL (which for the most part works only on uncrewed missions except for their maintenance of the Deep Space Network for communications) for their communication via Pathfinder, and that the rover comms system apparently used a slight adapation of the same comm software as Pathfinder, which is actually not unlikely.

Overall, it was an entertaining film that clearly leveraged a lot of real science and engineering experience to tell a plausible story, and of course great performances by the always solid Matt Damon and a great supporting cast. I wouldn't put it on par with [2001: A Space Odyssey, but then very few films even achieve that milestone. It is certainly way better than anything you're ever going to see out of J.J. Abrams hack machine.

Stranger
#217
Old 10-11-2015, 05:13 AM
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Were'nt the Apollo astronauts also pretty much reliant on a single ascent engine, and screwed if it failed?

As it is, supplemental materials (with Neil Degrasse Tyson!) suggest that the Hermes is basically a mobile ISS and the outbound flight takes 4 months.
#218
Old 10-11-2015, 05:21 AM
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Originally Posted by Stranger On A Train View Post
As someone else mentioned, the Hermes did appear to be using some type of solar electric ion thruster; however, the discussion of using Hohmann transfer orbits and the timeline of the transfer suggested discrete impulse, not any kind of continuous thrust.
The Hermes did use an electric thruster, but it was powered by a nuclear reactor, not solar.

Weir did the simulations using a homebrew program and at least claims that the maneuver was based on a constant low-thrust engine. Simulating this stuff isn't extraordinarily difficult so I'm inclined to believe that it works out.

Of course, the Hermes had normal maneuvering thrusters as well (presumably a common hypergolic bipropellant). They used up much of the propellant reserve on the final capture. The main thruster wouldn't have been useful there--they only needed a few tens of meters per second, but the acceleration would still have been way too low.
#219
Old 10-11-2015, 06:49 AM
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Originally Posted by bup View Post
Well, you can do what you want, but it was clearly a pretense of the movie.

The idea to slingshot around earth and send the ship back to Mars to get Watney was hidden in an attachment that was supposedly a picture of Martinez' family. And that unauthorized transmission of information cost Henderson his job.
The email was addressed to Vogel in the book. Did they change that in the movie? (I remember because the bad German aroused his suspicion.)
#220
Old 10-11-2015, 06:49 AM
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Originally Posted by Mince View Post
By "...no one had any idea that the crew could get back to Mars." you have to be referring to time. But how much time passed between the crew leaving Mars and Watney's first message to NASA? Certainly not more than a year (or I misunderstand the movie), and Watney estimated he had a year of food, without rationing or potatoes. And he must have known how much food he had left when he first contacted NASA because he would have determined that first, long before he underwent the lengthy task of contacting NASA. Why would anyone think they'd could not return in time?
Because without the Rich Purnell manoeuvre, they couldn't. Hermes was already well on its way to Earth, and couldn't simply turn around.

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Originally Posted by Stranger On A Train View Post
More problematic is that the MAV seems to have no propulsive capability--not even attitude control--after ascent booster burnout, and thus is tumbling. This really makes no sense, especially since the entire crew goes down to the surface. It also doesn't make much sense that they wouldn't have accounted for potential variance in the rendezvous calculations and planned the trajectory accordingly. No reason was given for the propulsive shortfall and no discussion of off-nominal performance, so the last minute 'Hail Mary' pass of blowing an airlock to eject the ship's air came off as being highly contrived.
This is explained in the book: the MAV is designed to comfortably lob six astronauts (plus rock samples, etc) into low-Mars orbit. In this instance, though, it needs to rendezvous with Hermes on a high-speed flyby. Even stripped down and with only one passenger, it can't quite make it, but they calculate it can get within grabbing distance at a barely-acceptable speed difference. In the event, the canvas covering on the capsule comes loose and causes enough drag to interfere with the burn, so Watney ends up several kilometres further away than planned and too slow to grab.
#221
Old 10-11-2015, 07:09 AM
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Originally Posted by Cara mel View Post
The email was addressed to Vogel in the book. Did they change that in the movie? (I remember because the bad German aroused his suspicion.)
It was addressed to Vogel in the movie too, but there was no bad German to alert him. He just couldn't open the file and needed Johanssen's help.

Speaking of the book, it has a great opening sentence: "I'm pretty much fucked."
#222
Old 10-11-2015, 10:35 AM
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Originally Posted by Stranger On A Train View Post
As someone else mentioned, the Hermes did appear to be using some type of solar electric ion thruster; however, the discussion of using Hohmann transfer orbits and the timeline of the transfer suggested discrete impulse, not any kind of continuous thrust.
Did they mention the Hohmann orbit for the Hermes? I only recall them mentioning it for the supply mission.

Quote:
More problematic is that the MAV seems to have no propulsive capability--not even attitude control--after ascent booster burnout, and thus is tumbling.
The Ares-III had a OMS system, because the pilot used it to prevent the MAV from tipping over.

In the book, it says "The orbital maneuvering system has three redundant thrusters. We'll get rid of those." I'm not sure if that meant getting rid of backup thrusters, or all thrusters.

Quote:
No reason was given for the propulsive shortfall and no discussion of off-nominal performance, so the last minute 'Hail Mary' pass of blowing an airlock to eject the ship's air came off as being highly contrived.
The MAV was only designed to get to low Mars orbit, not match speeds with a flyby. They thought they reduced the weight enough to do this, but when the Hab canvas covering the front of the MAV blew away, the increased air resistance caused the shortfall in speed. At least that seems to be the excuse in the book.

This makes me wonder why anyone thought the Purnell Maneuver was a good idea, if there was so little margin in the MAV performance. They must have known from the beginning how much mass they needed to remove from the MAV to make it work, and what that entailed.

Quote:
There is still the cost of labor and mission planning, which is considerable. And contrary to your statement, NASA employees can get overtime as approved on a by-project basis.
OK, point taken. I still think most of the cost is opportunity cost (other missions being delayed or canceled to make the rescue possible) rather than dollar amounts, but that is still a cost.
#223
Old 10-11-2015, 10:38 AM
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Originally Posted by Stranger On A Train View Post
As someone else mentioned, the Hermes did appear to be using some type of solar electric ion thruster;

More problematic is that the MAV seems to have no propulsive capability--not even attitude control--after ascent booster burnout, and thus is tumbling.

This does beg the question, however, of the apparent lack of contingency operations. Had the MAV fail to function (which is one of the major reliability drivers in studies of the NASA Design Reference Missions) it appears the crew would have had neither an alternate ascent method or contengency for a longer surface stay until replacement supplies arrived. This is a real problem in actual mission studies with no clear solution other than fully redundant ascent capability or a large surplus of supplies, but the problems they had keeping one astronaut alive would have been multiplied by a factor of six (at least) had the MAV failed to launch, and yet they appeared to have no thought toward the contingency. For that matter, they seemed to be doing little in the way of contingency studies for resupply trajectories, whereas in reality there is substantial effort put into contingency operations thoroughout all phases of planning. (That scene in Apollo 13 with engineers scrambling to figure out how to connect the CSM lithium hydroxide canisters to the LM systems? That was all worked out well in advance with the expectation that the LM could be used as a lifeboat.)

and that the rover comms system apparently used a slight adapation of the same comm software as Pathfinder, which is actually not unlikely.

Stranger
Those panels on the side of the Hermes that are facing every which way I think are supposed to be nuclear heat radiators, Stranger. NASA didn't figure out that Watney was still alive for weeks after the Hermes left, because they were afraid of the bad PR of airing images of his body. (per the book)

I think you've got a major point regarding the MAV reliability. As for why it doesn't seem to have any attitude thrusters - I guess they could have removed the hypergolic fuel tanks, or vented them, in order to shed mass? 5.6 kilometers per second in a vehicle designed 3 or so is an enormous change, isn't it? I guess they left a limited amount of hypergolic fuel onboard for control during ascent, and there wasn't enough remaining after dealing with the unbalanced drag from that tarp coming loose. Per your max Q numbers, that is apparently totally plausible. Watney wasn't injured by the wind stream at max Q, he was injured by a peak acceleration of 12 G - they ran that MAV to the absolute limits at 120% throttle or something the entire ascent to eke out all the performance possible.

Stranger, if during the Apollo days they wanted to use the LM as a lifeboat, why didn't they make the lithium hydroxide canisters compatible with each other from the beginning? Actually, that brings up the question of why didn't they share life support components in general between the spacecraft to simplify design.

In the book, it's not that the rover used the same comm software as pathfinder. Basically, it was a bootstrap hack. They had very little bandwidth to talk to watney - they had to send commands to move the pathfinder camera servo while Watney was standing there with a clipboard, writing down the output in hex.

So what they did was, the hardcore hex hack of the rover essentially put it's radio into a mode where it listens on a frequency the pathfinder can broadcast on (the rover radio was probably software defined and able to do a huge frequency range) and it would accept a repeating binary message coming from the pathfinder lander and load that message, after correcting errors, as executable code and run it.

So the JPL guys created a whole software application that would run on the rover, and they just needed Watney to hack the rover so the rover would start loading the binary stream of that application. They found a way to do it that involved making very small changes to the rover software. Frankly, they may have used hacking techniques like deliberately buffer overflowing the rover OS and so on - that hex change that Watney made might have just been something like "listen on this frequency. When frame read, move instruction pointer to beginning of frame. Disable buffer overflow protection."

It was something simple like that, and then the message being broadcast by pathfinder would have done the rest, allowing NASA to ultimately upload a multi-megabyte patch if they wanted to.

Last edited by Habeed; 10-11-2015 at 10:42 AM.
#224
Old 10-11-2015, 10:42 AM
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Originally Posted by Siam Sam View Post
It was addressed to Vogel in the movie too, but there was no bad German to alert him. He just couldn't open the file and needed Johanssen's help.

Speaking of the book, it has a great opening sentence: "I'm pretty much fucked."
Now that I think of it, the German tag on the e-mail in the book was not bad German. It just said "Our Children" in German when actually he and his wife always called them by a pet name. He thought it odd that she didn't use it.
#225
Old 10-11-2015, 12:08 PM
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Originally Posted by Cara mel View Post
The email was addressed to Vogel in the book. Did they change that in the movie? (I remember because the bad German aroused his suspicion.)
It was addressed to Vogel in the film too, but he wasn't German, and the file was labeled "Our Children" instead of 'unserer kinder".
#226
Old 10-11-2015, 01:52 PM
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Looking around, I found this animation of the Hermes's course trajectories - the planned mission, the immediate return to earth after the abort, and the 'Rich Purnell' trajectory:

http://galactanet.com/martian/hermes.mp4

This is based on the book, where the abort was on sol 6, rather than on the movie where it happens a few sols later, but that shouldn't change much.

The Rich Purnell trajectory is something. The flyby with the Earth puts the ship into an elliptical orbit that takes it scarily close to the sun, coming within the orbit of Venus unless I'm mistaken, and would take it well outside the orbit of Mars too. After passing Mars and picking up Mark they have to aim the engines ahead of them and slow down hard to drop back and return to Earth. It's no wonder that the director at NASA didn't like the plan, there are multiple ways this could not just fail but cost them the only interplanetary ship they have.

Also worth noting that the MAV doesn't just have to make orbit around mars, it has to match velocity with a ship that's going far too fast to orbit. So if Mark doesn't get picked up, he's not falling back to mars, he's going into an elliptical orbit around the Sun.
#227
Old 10-11-2015, 04:09 PM
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Thanks, that is very good!
#228
Old 10-11-2015, 04:44 PM
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Originally Posted by AK84 View Post
Were'nt the Apollo astronauts also pretty much reliant on a single ascent engine, and screwed if it failed?

As it is, supplemental materials (with Neil Degrasse Tyson!) suggest that the Hermes is basically a mobile ISS and the outbound flight takes 4 months.
Yes, the LM had a single descent and single ascent engine. Had either of them failed in operation the LM would have crashed or been disabled with the astronauts stranded. This was considered the single largest reliability issue with the Apollo/Saturn lunar system and received corresponding scrutiny. The engine design that TRW came up with for the Descent Propulsion System used a highly throttleable engine with a pintle injector that has lineage to the TRW TR-106 Low Cost Pintle Engine which itself served as a basis for the original SpaceX Merlin engines, although the Merlin design has evolved significantly since (and uses RP-1 instead of LH2 as the fuel). The engine for the Ascent Propulsion System was even more simple, and yet Bell Aerospace (the contractor for the engine) had substantial problems in the development. The engine itself had to be rebuilt after every testing because of the low margins and materials that did not resist corrosiveness of the hypergolic propellants, and therefore could not be tested prior to use.

The lithium hydroxide canisters for the CSM and LM were not the same because there was no requirement early in the development and the notion of using the LM as a lifeboat and for alternate purposes was proposed by Grumman later in development. The difference in form factor was also governed by the relative space in the CSM and the LM. The LM was well behind schedule and had numerous problems in development such that it was on the critical path to flight during the entire development program and so making a radical change (which it would have been) would have badly compromised schedule for a contingency nobody considered particularly likely at the time. Although much was made of building the adaptor in the Ron Howard film, it really wasn't that big of a deal compared with some of the other challenges such as the multiple correction burns and loss of environment thermal control.

It should be noted that the Apollo program was very specifically a high risk program that, according to some estimates, had a 50% chance of failure for the first landing attempt despite all of the effort put into testing. It was just way more marginal than anything designed to operate under current crewed mission reliability requirements and the durations necessary for an interplanetary mission. That duration, and the number of unavoidably high risk operations for a crewed Mars mission increase the reliability burden dramatically such that going to Mars with a comparable risk level requires enormously more (by orders of magnitude) component level reliability and/or fully redundant operations, hence the large cost estimates for such a mission.

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Originally Posted by Dr. Strangelove View Post
The Hermes did use an electric thruster, but it was powered by a nuclear reactor, not solar.

Weir did the simulations using a homebrew program and at least claims that the maneuver was based on a constant low-thrust engine. Simulating this stuff isn't extraordinarily difficult so I'm inclined to believe that it works out.
Having not read the book or looked at supplementary information I wasn't aware of this but it makes sense. (I was so jazzed at just hearing the mention of using a Hohmann transfer orbit at all that I didn't really track that it was just for the resupply mission.) Yes, doing those trajectory simulations at a first order level is pretty easy, either using publicly available codes like POST or Copernicus, or the multitude of internal codes that JPL and the other NASA centers have developed for various purposes. I have a homebrew code written in Matlab and C that is only a few hundred lines to calculate ephemerides and map discrete impulse trajectories. What was a little silly is that one guy was apparently calculating the trajectory, as well as his sitting in a server farm with his laptop connected and waiting for the "Calculations Correct!" message to pop up. (I sure wish my analysis codes would just tell me that the solution is correct instead of relying on me to interpret the data and draw my own conclusions.) The briefing of a junior trajectory analyst to the director of NASA, sans any kind of briefing charts or review panel, was also a little absurd. But I realize that these were done for the purpose of dramatic tension and/or comedic effect. Nobody, and I mean nobody, wants to watch the five tiers of briefings and peer reviews it would take to get to that level even in an emergency.

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Originally Posted by WotNot View Post
This is explained in the book: the MAV is designed to comfortably lob six astronauts (plus rock samples, etc) into low-Mars orbit. In this instance, though, it needs to rendezvous with Hermes on a high-speed flyby. Even stripped down and with only one passenger, it can't quite make it, but they calculate it can get within grabbing distance at a barely-acceptable speed difference. In the event, the canvas covering on the capsule comes loose and causes enough drag to interfere with the burn, so Watney ends up several kilometres further away than planned and too slow to grab.
I didn't really understand what they were trying to accomplish with the covering. It didn't have enough structural integrity to protect against any significant impact, and of course it is going to come free during flight; we generally hate textile elements like rocket cozies or covers with a passion just because they are so unpredictable and tend to snag on things, like the STARS vehicle that failed flying out of Kodiak last year. However, it still doesn't explain why the MAV capsule doesn't have at least an ACS or RCS system on-board to correct for rotations and allow fine maneuvering at docking. It's a minor point, but I can't imagine designing a spacecraft of this type, intended to separate from the propulsion booster and its ACS system, that didn't have some kind of on-board ACS/RCS.

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Originally Posted by AndrewL View Post
The Rich Purnell trajectory is something. The flyby with the Earth puts the ship into an elliptical orbit that takes it scarily close to the sun, coming within the orbit of Venus unless I'm mistaken, and would take it well outside the orbit of Mars too. After passing Mars and picking up Mark they have to aim the engines ahead of them and slow down hard to drop back and return to Earth. It's no wonder that the director at NASA didn't like the plan, there are multiple ways this could not just fail but cost them the only interplanetary ship they have.

Also worth noting that the MAV doesn't just have to make orbit around mars, it has to match velocity with a ship that's going far too fast to orbit. So if Mark doesn't get picked up, he's not falling back to mars, he's going into an elliptical orbit around the Sun.
Not to mention losing the rest of the crew. It's really a pretty bad plan, but as pointed out, the resupply plan also had a large number of uncertainties and untested operations. In reality, I would expect that NASA would already have a contingency resupply plan sufficient to support the entire crew in the case of MAV failure or other problems (high ionized particle flux predicted during the transit profile or other problems that might strand astronauts on the surface for a longer mission duration).

If Watney missed the intercept he'll end up in solar orbit instead of around Mars, but he'd be dead either way, as he has no way to return to the surface (and apparently no supplies or habitat to survive in) so there really wasn't a fallback regardless. That's just the nature of orbital ballistics, and the same thing applies to planetary swing-by maneuvers and other critical energy operations; you will only get one shot to get it right, else you are sailing off into the black.

Mind you, these are all fairly minor nitpicks on the film. It got the technical details far more right than almost any other movie I can think of, and even the botany behind growing potatoes was plausible. I especially liked his speech in the end which didn't minimize the risks inherent in crewed spaceflight, and the necessity of "working the problem" over giving up or engaging in heroics, notwithstanding the 'Hail Mary' retrothrust maneuver by venting the bow airlock.

Stranger
#229
Old 10-11-2015, 07:51 PM
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Just came back. Pretty awesome but not anything at the top of the all-time SF list at least.

I thought the rover journey/ending was pretty rushed (the pacing all of a sudden got sped up towards the end), and they didn't mention the canyon that he had to navigate. I hope stuff like that gets put in an extended edition...
#230
Old 10-11-2015, 07:58 PM
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Originally Posted by John DiFool View Post
Just came back. Pretty awesome but not anything at the top of the all-time SF list at least.

I thought the rover journey/ending was pretty rushed (the pacing all of a sudden got sped up towards the end), and they didn't mention the canyon that he had to navigate. I hope stuff like that gets put in an extended edition...
It had imperfections, yet, but can you actually name 10 sci-fi movies that were better? I guess I'm giving it a lot of weight because it was "fictional science" - some technical errors but more or less it could physically have happened that way. The instigating event would have had to be something else, but it is possible for the crew to be forced to leave early. Even classics like 2001 both depend on alien space-magic for the premise, and as it turns out, the fusion spacecraft in 2001 is at the extreme limits of what is even vaguely plausible at all.
#231
Old 10-11-2015, 09:50 PM
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Originally Posted by Habeed View Post
The instigating event would have had to be something else, but it is possible for the crew to be forced to leave early.
I have a thought.
The night before their scheduled MAV liftoff to rendezvous with Hermes, the Ares III crew gather in the Hab. After a fight with Martinez, Mark Watney is sent to the third floor of the Hab, where he wishes that the crew would disappear. During the night, a power outage resets the alarm clocks and causes the crew to oversleep. In the confusion and rush to reach the MAV on time, Mark is left behind and the crew is unaware until they are already airborne.
#232
Old 10-11-2015, 10:20 PM
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Originally Posted by ElvisL1ves View Post
It was addressed to Vogel in the film too, but he wasn't German, and the file was labeled "Our Children" instead of 'unserer kinder".
Vogel is German.
#233
Old 10-11-2015, 10:39 PM
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Yes, Vogel was German in the film too. The e-mail was labeled "Our Children" in English in the movie, but I figured that was because non-German-speaking moviegoers might not know what "Unsere Kinder" meant. Or maybe it being in English was a clue to Vogel that something was up but the movie did not go into it.

Last edited by Siam Sam; 10-11-2015 at 10:41 PM.
#234
Old 10-11-2015, 11:17 PM
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In the book, the email title is "Unsere Kinder", which Vogel knew wasn't from his wife, because they always called their kids "Unsere Affen", "Our Monkeys".
#235
Old 10-11-2015, 11:20 PM
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Yes, but the movie decided not to go into it the esoterica of the e-mail line.

Vogel was definitely German in the movie. The book spelled it out, while in the movie his space suit carried an EU flag patch and he spoke with a German accent.

Last edited by Siam Sam; 10-11-2015 at 11:21 PM.
#236
Old 10-11-2015, 11:32 PM
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Originally Posted by Siam Sam View Post
Vogel was definitely German in the movie. The book spelled it out, while in the movie his space suit carried an EU flag patch and he spoke with a German accent.
I just saw the movie today (have not read the book), and while personally I didn't think his accent sounded very German it did seem clear that the character was meant to be German. I'm pretty sure he was jokingly referred to as a Kraut at least once -- I think Martinez made some crack about his "weird Kraut porn" or something along those lines.
#237
Old 10-11-2015, 11:39 PM
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That's right, Martinez did. I remember that now. Vogel's accent was not very pronounced, but it was there. I may have picked up on it more because I already knew he was German.
#238
Old 10-12-2015, 02:46 AM
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Originally Posted by Mince View Post
Like after finding out the truth about Watney, the professional astronaughts would have run around the bridge with their hands in the air, losing control of the ship, crashing into the moon.
Their reaction doesn't have to be absurd or cartoonish for the additional stress to potentially cause a problem. Trained astronauts aren't robots, and human beings have noticeably reduced capacity when dealing with grief and stress and guilt.

Quote:
Presuming he was fated to die before rescue, do you think they would have been less emotionally affected if they found out years later that he suffered and died? It would probably have been more emotionally gruelling because they would never have been given the chance to at least consider rescue options (what ifs). Grief and emotions are rational; sometimes our reactions to them are not.
Probably true. But if it happens on Earth, and not while they're piloting a $billion spaceship, well. I can see NASA choosing to let them suffer some extra anguish to improve the chances of the rest of the mission even slightly.

Quote:
But nothing in the context of the movie (haven't read the book) suggests that the crew....anyone....thought returning in time was impossible.
You're misremembering. Until he gets Pathfinder, NASA thinks he's going to starve before they can even get supplies to him. And no one knows about a way to get Hermes back until Rich Purnell figures it out, after the first failed probe launch, and after NASA has already told the crew about Watney (which they did because there was a viable plan to rescue him).
#239
Old 10-12-2015, 03:52 AM
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Originally Posted by ElvisL1ves View Post
I went in already highly inclined to love it, and did. Not gonna pick apart plot points, just gonna revel in it. Thanks, Andy!

Facebook-feed comment: Saving Private Ryan, Interstellar, now The Martian. The film industry has worked very hard to keep bringing Matt Damon home.
His film career began with everyone around him trying to convince him to LEAVE home.
#240
Old 10-12-2015, 11:11 AM
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Originally Posted by Stranger On A Train View Post
...The thing that really threw me out while watching the film weren't the techincal details but the the ultra-modern appearance of both Houston mission control and especially JPL, which in reality looks like a college campus that hasn't seen significant renovation since the early 'Eighties....
Guess they have some upgrades to look forward to in the next 20-some years.

Quote:
Originally Posted by AndrewL View Post
Looking around, I found this animation of the Hermes's course trajectories - the planned mission, the immediate return to earth after the abort, and the 'Rich Purnell' trajectory:

http://galactanet.com/martian/hermes.mp4....
Very cool - thanks! Wish they'd shown something like that in the movie.

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Originally Posted by Siam Sam View Post
...Vogel was definitely German... in the movie his space suit carried an EU flag patch and he spoke with a German accent.
Not an EU flag, but a German one.

http://i.imgur.com/S9fKd1J.jpg
http://screenrant.com/wp-content/upl...n-Exercise.jpg
https://40.media.tumblr.com/ef8a7b60...bmnzo1_500.jpg
#241
Old 10-12-2015, 11:17 AM
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Whats the difference. By 2030's they will be one and the same anyway.
#242
Old 10-12-2015, 12:08 PM
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Originally Posted by Mince View Post
By "...no one had any idea that the crew could get back to Mars." you have to be referring to time. But how much time passed between the crew leaving Mars and Watney's first message to NASA? Certainly not more than a year (or I misunderstand the movie), and Watney estimated he had a year of food, without rationing or potatoes. And he must have known how much food he had left when he first contacted NASA because he would have determined that first, long before he underwent the lengthy task of contacting NASA. Why would anyone think they'd could not return in time?



But my point about professional astronauts not acting like bumbling idiots upon hearing adverse news? They're trained to navigate space, colonize Mars (essentially), and return home. I think they'd perform ok under a bit of emotional pressure.
NASA discovered that Mark was alive around Sol 54 if I'm remembering correctly, and the rest of the crew had left at around Sol 20. So it's true that in terms of distance, the crew wasn't super far away.

But even if they could just turn the ship around and turn back to Mars (which I don't think is very easy or maybe even possible in terms of spaceflight), they didn't have a way to pick up Mark. I'm pretty sure they didn't have any capsules or ships or anything they could send down to the surface. The vehicle that Mark used to get into orbit was 8000 km away, much further than anyone had ever traveled in a rover. He mentioned in the movie how the rover only can go for about 32 km before being recharged. Also at the time they had no way to communicate with Mark. It was only after he went and got Pathfinder where NASA and the crew were able to communicate with Mark.
#243
Old 10-12-2015, 06:04 PM
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Originally Posted by Stranger On A Train View Post
Having not read the book or looked at supplementary information I wasn't aware of this but it makes sense.
Unfortunately I don't have the book at hand but I'll do a little plausibility calc using the numbers I do have.

I know that the engine was supposed to give 2 mm/s2 of acceleration. That's high compared to typical ion thrusters but not obviously crazy.

First thing is how much delta-V the ship has available. A typical Mars transfer needs in the ballpark of 4300 m/s, but continuous-thrust transfers always need more, which I'll ballpark roughly as 5 km/s. However, the Hermes obviously had plenty of extra delta-V available; enough to return from Mars orbit and do another swingby. They didn't stop at Mars on the second round but they needed something for the modified orbit. Let's go with a total of 10 km/s (again, very rough ballparking).

With a 5000 s Isp ion thruster, the Hermes would need a 20% propellant mass fraction for 10 km/s delta-V. Seems pretty reasonable given the way it looked. There were some rather large tanks at the rear, but still just a fraction of the total.

By my math, to accelerate 1 kg at 0.002 m/s2 requires a mass flow of 4.1x10-8 kg/s. At a 49 km/s exit velocity, that requires 49 watts of input power.

If we can dedicate 25% of the ship mass to the reactor and the electrical efficiency is 50%, then we need about 400 watts/kg of reactor performance.

Looking around a bit, I see this paper, which seems (after a very brief skim) to indicate that 100 W/kg might be achievable. So 400 W/kg seems high, though perhaps more advanced technologies (gas cooled, etc.) would improve matters. If you could dedicate 50% of the ship mass to the reactor and get somewhat better than 50% efficiency, then you only need 150 W/kg performance. Still high but better.

However, better than spending more ship mass on the reactor is to turn down your exhaust speed, since power does up with the square. If we dedicate 40% of ship mass to fuel, we can turn down the thrusters to an Isp of 2000 s (either in the design stage or using a variable-Isp engine like VASIMIR). That increases our energy efficiency by a factor of over 6, making the reactor far more plausible.

All in all it looks ok. Optimistic, sure, but not fantastic.

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Originally Posted by Stranger On A Train View Post
What was a little silly is that one guy was apparently calculating the trajectory, as well as his sitting in a server farm with his laptop connected and waiting for the "Calculations Correct!" message to pop up. (I sure wish my analysis codes would just tell me that the solution is correct instead of relying on me to interpret the data and draw my own conclusions.)
I did laugh at that, though at this in this case it's more like "firing solution found", which might look at millions of possible trajectories before finding one that met the constraints. Still, my code is more liable to print a single "done." at the console instead of popping up a fancy graphical window.
#244
Old 10-12-2015, 11:02 PM
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Originally Posted by Dr. Strangelove View Post
Still, my code is more liable to print a single "done." at the console instead of popping up a fancy graphical window.
Maybe in 2035, where every client OS is now something akin to android and the OS has easy to use GUI libraries baked in, it's just as easy to do a fancy window as a simple line of text. Or it's just sci fi.

Seriously, conceptually, showing a window is not much more difficult than printing a line of text. (the information you need to feed a library stack is not any more complex, even though the actual code to draw a window is far more complex) The issue is that the graphical tools like visual basic have dogshit programming languages behind them, while gcc doesn't have an easy to use GUI editor that lets you just draw up a gui in seconds and hook it to events in your code built in.

Last edited by Habeed; 10-12-2015 at 11:03 PM.
#245
Old 10-13-2015, 10:47 AM
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Yeah, the real silliness there was that Purnell was doing all that while physically sitting in the middle of the server farm.

Well, that, and he was aiming all of that processing power at the wrong target. It's really easy for a computer to take a rough orbital plan and polish it up for maximum efficiency, speed, economy, or whatever, or to verify that it can meet some set of constraints. Purnell's laptop by itself could do that easily. Heck, those tablets the astronauts had on their wrists could do it, if they had the right app (and why wouldn't they?). The really hard part, which might justify the use of the massive data center, is in coming up with the basic plan to begin with... but that all came out of Purnell's own steely-eyed head.
#246
Old 10-13-2015, 10:21 PM
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Huh. Coulda sworn I saw an EU flag.
#247
Old 10-13-2015, 11:40 PM
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Originally Posted by Chronos View Post
Yeah, the real silliness there was that Purnell was doing all that while physically sitting in the middle of the server farm.
Not strictly necessary, but I can't say that I've never done something along those lines. Usually to debug something that I need to see in person for whatever reason. I can imagine that Rich knows that he'll be stuck at the back of the job queue if he submits his job remotely, and being so junior has no way to bump the priority. But if he shows up and plugs in locally, he can disconnect the network between the farm and the rest of the facility, guaranteeing that his jobs will be executed first .

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Originally Posted by Chronos View Post
The really hard part, which might justify the use of the massive data center, is in coming up with the basic plan to begin with... but that all came out of Purnell's own steely-eyed head.
There's sort of a middle ground in this particular case. Although it's straightforward to compute the behavior of a continuous-thrust engine given a set of commands, the space of possible commands is immense. This is in contrast to impulse-thrust engines (chemical rockets) where there is some small finite number of thrust events, and they almost all occur at a periapsis or apoapsis.

So Rich might have come up with the basic swingby maneuver, using experience and intuition to predict that it's possible given the constraints, but still only have a vague idea of the engine commands needed to achieve that goal. That's where the heavy work comes in, to try zillions of possibilities (running an optimizer on each one) to find the best.

That said, Weir did his calcs on a ~2010 era PC, so technically we have proof that the server farm wasn't necessary .
#248
Old 10-14-2015, 12:06 AM
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Originally Posted by Siam Sam View Post
Huh. Coulda sworn I saw an EU flag.
I'm a flag guy and always tend to notice them. Never saw an EU flag in the movie myself.
#249
Old 10-14-2015, 03:34 AM
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Andy Weir says he wrote a program to calculate the course of Hermes, including the various rates of acceleration; he assumed the ship used a VASIMR drive, which requires a very efficient nuclear reactor on-board, but is otherwise reasonable.
#250
Old 10-14-2015, 07:58 AM
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Originally Posted by Dr. Strangelove View Post
So Rich might have come up with the basic swingby maneuver, using experience and intuition to predict that it's possible given the constraints, but still only have a vague idea of the engine commands needed to achieve that goal. That's where the heavy work comes in, to try zillions of possibilities (running an optimizer on each one) to find the best.
You would think that NASA would have something a lot more detailed than simulating a point under acceleration traveling through space for the Hermes. The simulator would be a full up discrete model of the whole spacecraft, modeling the fuel flows, radiation and temperature fluxes, component failures, with the data the simulation uses coming from information extracted from actual telemetry and maintenance records for the Hermes.

If you think about it, to find out if it's even possible, you need to check against a model of the ship breaking and factor in occasional engine failures, etc, during the flight. A model like this would be extremely memory hungry and there are many possible permutations to try. Not to mention, the model would do N-body gravity the way NASA does it, where each planet isn't just a point mass, it's modeled by an equation that determines the gravitational field at a particular position in orbit around the planet.
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