The fatal flaw in The Martian's ending

the ending of The Martian the 2015 movie based on the book by Andy Weir commits so many crimes against scientific accuracy that it almost ruins the rest of the movie that is a fairly controversial statement considering that the Martian is widely praised as being one of the most scientifically accurate science fiction films ever made without melting your brain like Interstellar did and honestly it's great I love this movie the level of scientific detail in it is astounding most scientific inaccuracies like Watney walking around on Mars as if it's got Earth gravity and subsequently Matt demon being ripped enough for this gratuitous shirtless scene these can mostly be explained Away by practicalities of filming but the ending the ending commits potentially the worst crime that any movie claiming scientific accuracy can commit it drives an astrophysicists like me to make a video like this picking it apart from being completely and utterly ludicrous the ending of The Martian centers on the rescue of Mark Watney who has been stranded on Mars for 549 Souls or to put it in Earth time 564 days Watney has already launched into space from the surface of Mars and not much more than a tent with a rocket on the back suffice to say issues ensue and he doesn't make it as high as intended he's too far from the Hermes where his crew are waiting to rescue him and they're traveling at wildly different speeds to rescue botany the crew build a bomb blow up their front hanger causing an explosive decompression of most of their living species to slow down the Hermes which solves most of the speed issue according to the crew but not the distance issue there's still some 312 meters between Mark Watney and Commander Lewis what Watney decides to do is cut a hole in his glove and fly like Iron Man using the thrust from the escaping air from his glove to propel him towards Commander Lewis and ultimate rescue this whole rescue attempt has so many issues that I'm gonna have to go bit by bit also I'm not Simon if you haven't noticed already my name is Thomas rental I am an astrophysics Master student and science Communicator who Simon's greatest invited to make a video for his channel there are a few differences between myself and the weatherman for one thing I'm Scottish for another I'm not over six feet tall but there's more about me at the end of the video for now let's let physics that is real physics not movie physics explain what really should have happened at the end of The Martian if we're gonna ignore the whole going into space on gratar the Martian atmosphere is essentially non-existent it's very very thin so you don't get the same levels of burnout per atmospheric friction that you get with Earth's atmosphere this brings us on to the speed difference between Mark Watney and the Hermes this is indeed a problem they need to essentially match speeds at least to the point that somebody could catch water to stop him flying off into space otherwise this rescue attempt is never going to happen anyone who's played a bit of Kerbal Space Program or done things properly and studied orbital mechanics we'll know that a bit of thrust in the right direction is what's needed the Hermes crew need to slow down the Hermes to Rendezvous with Watney but because the Hermes only has low thrust but highly efficient ion thrusters they can't use those to change speed fast enough to rescue Mark Whitney if you want to learn more about ion thrusters then check out Simon's recent PhD stories video where he talks to someone researching the technology since the thrusters are out of the question the Hermes crew decided to slow down by venting atmosphere in one of the most ridiculous ways possible the explosion wouldn't make it any better of us of a slowing mechanism there's nothing for it to push against you would get the same thrust from just opening the door and venting the atmosphere that way I know in the book they say that they can't just attack the Hermes and open the door but they could hack it before so I'm sure they could hack it now it's really dumb I know it's in the book but a bomb should not have been plan a but explosive decompression isn't the biggest issue with this whole rescue attempt the biggest issue in my opinion is thrust vectoring and specifically mark watney's insistence on flying like Iron Man I'd get to fly around like Iron Man this in particular annoys me because the movie even tries to take it into account first you have this line from Commander Lewis I can't see you have any control if you did that you'd be eyeballing The Intercept using a Thrust Vector you can barely control and then when Whitney does cut a hole in his glove he flies around inside the spacecraft you know like this so they tried to show it why am I taking issue with this I'm taking issue with this because about five seconds later they completely ignore it arm outstretch managing to control this thrust vector and going in a straight line this is an issue because of what thrust vectoring is thrust vectoring is the physical principle that the location of a force relative to a body's Center of mass affects how that Force acts on the body affects what it does if Watney had instead cut a hole in the bottom of his basement rather than in the glove then air would be escaping approximately below his Center of mass this would be like putting a rocket underneath a spaceship all that thrust going straight through the center of mass and sending you off in a straight line but the hole is Not underneath Mark Wally the hole is in the glove of his spacesuit this is held outstretched away from his Center of mass so it's going to cause more rotational motion than linear motion this is what we see initially when he cuts a hole in the glove you see him spinning around however the movie just expects you to completely forget about that seconds later when Mark Bonnie is flying like Iron Man over to Commander Lewis in her spacesuit with her jetpack what should have been happening here wasn't Mark watney's rescue but rather his human-sized centrifuge experiment as he builds up a rotation from the era escaping from his outstretched glove but fine let's suspend our disbelief a little bit more and assume that Mark Watney is some kind of superhero that can get this thrust Vector under control to be pointing the right direction to send him off on his merry way to Commander Lewis would the thrust from his glove even have saved him no not a chance physics once again not on his side we're gonna assume that NASA's technical specs have not changed between now and 2035 so Mark's spacesuit is going to be sitting at about 4.3 pounds per square inch of atmospheric pressure which is about one-third of the atmospheric pressure at sea level the reason it can be so low is because they don't put nitrogen into the suits they just put oxygen straight in because you you still want to be able to move around if it was held at our sea level atmospheric pressure it'd be like being in a massive balloon and they couldn't do anything we're going to assume that Mark Martin's suit is able to maintain this pressure of 4.3 pounds per square inch throughout his flight replacing any Oxygen loss to space with oxygen from a reserve tank great how big a hole is he reasonably going to be able to make it's probably only going to manage about a square centimeter that's not very much area so how much thrust can he reasonably expect to be able to get from his tiny little oxygen gas Thruster extended out on his glove it's not going to be very much the force from the escaping gas comes from a pressure gradient a difference in pressure between the one-third of sea level atmospheric pressure inside the suits and the complete lack of pressure in the vacuum of space and while there is enough air in the spacesuit to breathe oxygen is a fairly light gas with a density of only around 0.4 kilograms per cubic meter of volume inside the spacesuit there's not much mass there so even though each oxygen molecule is escaping at incredible speed the force they provide is pretty pitiful converting our NASA spec pressure back from Freedom Units to the metric system that pressure over the one centimeter squared hole in Mark's glove is only going to give him around 0.15 meters per second per second of acceleration towards the Hermes with that minuscule level of acceleration it it would take Mark Watney over an hour to cover the 312 meters between the Mars Ascent vehicle and the Hermes with the relative velocities when he sets off of about 11 or 12 meters per second the Hermes is going to be long gone by the time Mark has any chance of getting to their position flying like Iron Man was never ever going to work so what would have happened to Mark Watney after he poked a hole in his glove assuming that his skin wasn't pulled into the hole plugging it like we've seen with a real life space suit print trees chances are he would just build up a slow rotation inside the map while he first tries to get it under control assuming he can manage that he'd get a small linear motion towards the Hermes building up a very slow amount of speed ultimately we've established that would never get him there eventually likely hundreds of meters away from the MAV his oxygen would run out and he would drift off into space forever the Hermes having to return to Earth with the many months-long trip again one crew member down so how did Andy we are author of The Martian the book not the movie get this so spectacularly wrong in an otherwise really scientifically accurate story spoiler alert if you care at this point he didn't he completely dismissed all of this nonsense in the book hey what he said over the radio I've got an idea of course you do Lewis said what do you got I could find something sharp in here and poke a hole in the glove for my Eva suit I could use the escaping air as a Thruster and fly my way to you the source of thrust would be on my arm so I'd be able to direct it pretty easily how does he come up with this Martinez interjected you'd be eyeballing the intercept and using a Thrust vector and you can barely control I admit it's fatally dangerous what he said but consider this I'd get to fly around like Iron Man Iron Man Commander Iron Man Commander Lewis completely disregards this whole ludicrous idea from the offset the Hermes crew then uses a combination of using the attitude control thrusters and blowing up the valve yes they use the bomb in the book it's still dumb but desperate times I guess in the book this works they don't need the whole flying like Iron Man section and the whole thing is far more scientifically accurate so is the ending of The Martian scientifically accurate No with the ending from the book have been quite as good a spectacle for removing of course not am I still mad about it well yeah but I'm a parent with an astrophysics degree so I guess I'm just going to get used to it thank you very much for watching my video all the way to the end thank you to look for editing it for me and particularly thank you to Simon for giving me the opportunity to share a video on his platform I just really wish it was under better circumstances if you enjoyed this video then please do come and subscribe to my YouTube channel there'll be a link in the video description below as well as a button somewhere around here for you to do just that I am currently finishing off my master's degree in astrophysics at the University of Saint Andrews and I will hopefully someday soon be embarking on a PhD I make videos like this one to make physics and particularly astronomy accessible and entertaining and quite early in my YouTube Journey so it would be really good to have as many of you along for the ride as possible I also stream pretty regularly over on Twitch I post on Instagram and I scream into the void on Twitter those all have varying levels of science as part of them the handles for those will be on the screen and in the video description below if you want to come and check those out in the meantime all I have left to say is thank you very much again for watching the video like comment subscribe to Simon subscribe to me and I will see you in the next video over on my channel see ya

Channel: Simon Clark

Views: 306,369

Keywords: drsimonclark, dr simon clark, simonoxfphys, simonoxphys

Id: cg8cjYS-zgY

Length: 11min 28sec (688 seconds)

Published: Wed May 10 2023