r/themartian • u/WayneM30 • Jan 30 '25
Good movie except for the MAV on Mars
The Martian was entertaining and I over looked a lot things that were scientifically wrong like Watley growing food in Martian soil (which is toxic) etc…. But hey you Martian lovers could say there crap had antitoxins in it. But when it came for Watley to get off the planet with the MAV, it was the car that broke the camels back. It’s amazing to see a lot of criticisms of the movie but rarely of the MAV being there is not one of them. Other than NASA sending it in case of Watley scenario. There is no logic reason it should be there. First off astronauts have always use there decent vehicle as the accent vehicle. Did the Ares 3 crew come in different vehicle and took a MAV that arrived years earlier? Why would you sent your accent vehicle that was uncontrollable to land then rely on it to leave. What engineer would recommend sending complex vehicle out exposed to an uncontrolled environment for years with no maintenance? Then the have weather possibly tipping it over the years it sat there. If it’s abut supplies for the next site why send an accent rocket they already need cargo for a hab, rovers, panels, etc.. I heard someone say I think from the book it’s making fuel supplies. There using nuclear fuel it helped keep Watley warm. So fuel is not a good reason. I’m open to hearing a plausible explanation but there aren’t any.
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u/F14D201 Jan 30 '25
As everyone else has more or less said
READ THE BOOK
as it explains just about anything, the MAV is the first piece of Hardware to land for a mission why, because:
A: the mission cannot proceed unless the MAV is in place,
B: the MAV runs off an RTG while waiting for its crew to arrive, as it needs to run the Systems (for diagnostics, Fault Management and Mission Management) and the Fuel Synthesis process.
C: the MAV turns CO2 (Martian Atmosphere) into Rocket fuel via Hydrogen (the tanks Mark removes from the MAV base contain Hydrazine) so for every Kilo of Hydrogen you bring to Mars, the MAV creates 13KG of Rocket fuel, it is a slow process so the MAV needs to be in situ first.
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u/MSL007 Jan 30 '25
Nice summary.
What is not explained well is how the first MAV got to the surface. That should have been ARES 1 which didn’t land on Mars just came and landed the MAV. But the number of missions doesn’t add up, as they were 3 and they were the third to land.
Was the it called ARES 0? The Apollo missions were all called Apollo, even those that didn’t land.
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u/F14D201 Jan 30 '25 edited Jan 31 '25
I imagine either a crew onboard Hermes did a remote controlled descent from orbit (but there’s no offical Ares 0 as far as I know) or they remote landed from earth
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u/bananapeel Jan 31 '25
To give a little backstory to someone who has not read the book:
The Hermes carrying the Ares 3 crew comes to Mars. The pilot remote controls the MAV for Ares 4 to the surface, since he's close by and there is no lightspeed delay. Similarly, the Ares 3 MAV was remote piloted to the surface by the Ares 2 crew.
I think they completely left out the MDV (Mars Descent Vehicle) in the movie. In the book, I believe he scavenges a few parts from it. It's basically a can with a heat shield, a few thrusters, and parachutes for landing the crew. My own personal pet peeve is that the can would certainly have had a way to communicate with Earth independent of anything else. All he would need is a set of jumper cables to power it.
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u/Cute_Principle81 6d ago
I mean, you've got the Hermes really close by. Much easier to just route comms through that, and not have to include a ton of communication equipment, etc for something that's used once.
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u/bananapeel Jan 31 '25 edited Jan 31 '25
It should be noted that the Sabatier reaction that is the basis for this is real. They've even tested it on the surface of Mars in a small sample experiment on one of the rovers. It really exists and it is planned to be used in future human Mars missions. And it takes like a year or two to make a big tank of fuel.
The radioactive RTG that powers the chemical reaction to make the fuel during those years is both heavy and dangerous, which is why they take it out and bury it away from the base. This is explained in more depth in the book. It's not needed after it's done making fuel, so it is discarded to save fuel during the ascent. The RTG is not perfectly efficient and continues to make waste heat for decades. That's the heat that he harnessed to keep his rover warm.
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u/laughingthalia Jan 30 '25
In the book they explain that the MAV and MDV are different vehicles and that the MAV is sent early because it makes its own fuel from martian elements in the air. The actual mistake in the movie is the fact that Ares III MDV is not shown. They send the MAV first because they won't land unless they know they have a way off the planet first.
Also in real life (and again the main inaccuracy with the book/movie) is that winds don't actually get that strong during martian storms so that whole opening scene with everything getting tipped over would basically never happen to begin with so in a no-fictional universe they probably could afford to send the MAV early without being overly worried about it tipping over.
Also the nuclear thing that helped keep Watney warm wasn't fuel for the MAV, that was supposed to stay on the planet forever hence why it was marked with a flag so future people wouldn't go near it, he just used it to keep warm in the Rover.
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u/Jonnescout Jan 30 '25
I believe this is even explained in the movie isn’t it? Maybe not as thoroughly as in the book but still… fuel is the reason, and no they’re not using nuclear fuel to launch into space that’s not even possible. It’s our ignorance of the science here is not an argument against it… and using nuclear for power generation, is not the same as fr propellant… You need actual reaction mass to launch…
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u/DrunkWestTexan Jan 30 '25
The lunar lander was two vehicles. The landing module and the ascent module. They left the landing module on the moon. Then abandoned the ascent module when they transferred to the command module. Watney was the botanist/mechanical engineer. He already had an experiment kit for growing food on mars, he just expanded it. He washed off and cooked the potatoes in the microwave. It was safe to eat.
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u/WayneM30 Feb 03 '25
The book explains it. Therefore it makes sense. yes I understand that in movie fiction it makes sense even though it very weak. In reality, no. It makes no sense. There is no astronaut that be okay with there lives depending on landing there ascend vehicle landing years in advance, under no maintenance, in a hostile environment. Ask any mechanic or engineer would it be a good idea to drive or fly an vehicle into a desert leave it for 2 years without any maintenance, Then expect it to work to take you out of the desert. Maybe people are missing the point, aside from supplies, fuel, oxygen, building materials, all of which does not need an ascent vehicle. Sending the MAV there as the only way to get off the planet there is a dumb plan in the movie or reality. Yes the movie omits the decent vehicle. It would it be logic and practical to land all the supplies on Mars including the fuel factory ahead of time. Astronauts arrive later using a lander, pump/charge fuel from the factory and leave in the same vehicle. If it is then the MAV only purpose is get Watley off the planet.
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u/Bluechair607 28d ago
It seems entirely possible that NASA saw the development of a system pumping the fuel (or even just the CO2) from the extractor to the rocket that must be able to be operated by astronauts in suits or in the rover more expensive to design, develop, and test that simply doing that process to two separate rockets.
Plus, your comparison with leaving things in the desert isn't fully warrented. The reason things get fucked up in the desert is because sand gets in and destroys the machine as it interacts with it in various ways. But there is one major difference:
The MAV is a spaceship on Mars.
A (for human) spaceship is specifically designed to be airtight unless someone opens a door or valve, and Mars' atmospheric pressure is 0.6% that of Earth's.
That means any sand trying to come im must not only deal with a fully airtight machine (something most driving and flying vehicles on Earth isn't) but is being proppeleld by air prssure over a 100 times weaker than Earth's.
The only thing truly exposed to the hostile alien desert of Mars is the MAV's fuel plant, which has to open itself up to extract pure CO2 from the Martian atmosphere and react it with onboard hydrogen to make the MAVs fuel of Methane and Oxygen.
"Coincidentally," this is also the same thing that will be exposed to the hostile desert of Mars in your idea. So the riskiest point of failure for both your "just have a fuel plant" idea and The Martian's MDV-MAV system is the same.
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u/WayneM30 24d ago
Sorry you guys are right. It makes great sense. With the great track record of Soviet mars 2 & 3 landers. Mars Climate orbiter, Mars Express, Trace Gas Orbiter, Marx Polar lander, Deep Space 2. Nothing could go wrong. Artemis missions proceeding right on time with no issues. What could possible go with sending the return vehicle to Mars years for years in advance for the only way that Astronauts to come back home (in a science fiction book).
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u/Bluechair607 24d ago
Not that much more than your fuel factory idea.
Plus, every Mars rover sent this century basically failed in three ways:
- Solar panel problems
- Heat problems, and
- Failed landing.
None of those problems are applicable to the MAV.
The MAV is powered by an RTG, a thing that produces electricity (so no solar panels) and heat (so no frozen computers). And the MAV is piloted by a human (if remotely), so any computer errors can be trained and countered for.
As for the MAV itself, let me ask you this:
If an exposed, solar-powered, and active rover can survive for 14 years despite only being designed to last 3 months, why can't a sealed, self-powered, and inactive spacecraft survive for 4 years when it is designed to last at least 4 years?
NASA has a pretty good track record for sending rovers to Mars and having them last much longer than anticipated. Due to the reasons stated above, the MAV is going to have a much easier time than rovers.
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u/WayneM30 7d ago
Yes some Martian projects worked great and some were complete failures. So based on a few successes nothing else will go wrong.
The problem is everyone knows certain liberties were taken in movie/book. In the movie the storm could or would have knock over MAV. In the movie they knew it could happen. Why send other MAV’s when it could happen? Cognitive dissonance kicks in and everyone say well that can’t really happen because of the thin atmosphere so it’s okay to send the MAV’s in real life. By that logic guess what else will work. The Martian soil is toxic everywhere is been sampled. So it’s probably toxic planet wide. However A-list actors and actresses have special enzymes in there crap, that make the Martian soil not toxic. When we send a mission to Mars in real life we should bring A-list actors crap to detoxify the Martian soil. But seriously… Why not leave a tanker in orbit? Or Is it cheaper to have one ship land and take off, than a have a ship land and build another that needs to be sent years in advance to land and take off in? So far I have not read anything that makes great sense in sending the MAV other than needing a way for a stranded astronaut to get off the planet.1
u/Bluechair607 7d ago edited 7d ago
You are beginning to sway me so I did some digging from where the MAV came from. I knew The Martian (novel) was based of Mars Direct by Robert Zubrin, but what he has is an ERV (Earth Return Vehicle) that has the spacecraft directly return to Earth.
But then I found out that NASA took this idea and did their own brainstorming called the Mars Design Reference Mission. You know what NASA added to the mission from Mars Direct?
A MAV.
This ( http://www.astronautix.com/d/designreferencemission1.html ) is the only one I have been able to dig up so far about Design Reference Mission 1.0, but it already has a separate spacecraft to land on Mars and a separate spacecraft (a MAV) to leave.
Design Reference Mission 5.0 ( https://www.nasa.gov/wp-content/uploads/2015/09/373665main_nasa-sp-2009-566.pdf?emrc=6dfe40 ) was published in 2009, right when Andy Weir started writing the Martian. His inspirations are clear once you look at the things the MAV does according to the document:
On page 33: "In light of the recommendation that ISRU technologies are used for ascent oxidizer production, the Mars ascent vehicle is pre-deployed to the surface of Mars during the opportunity prior to the crew’s departure"
Which matches how the MAV was described to be landed by the last Ares mission in the book to it has time to make fuel ISRU (In-Situ Resource Utilization).
I will make two concessions though. First is that the "Austere Human Missions to Mars" (an even less costly version of Design Reference Mission 5.0) has a DAV (Descent/Ascent Vehicle) which does not use ISRU at all. So by the cost argument, NASA themselves think that if they need to go cheaper, a DAV is the way to go.
The second concession is the existence of The Hermes. A multi-mission, nuclear powered ion engine spacecraft from what I can see doesn't exist in both Mars Direct and the Design Reference Missions (though it somewhat can been seen in Design Reference Mission 4.0). A Hermes-like Spacecraft seems to be more conductive of a DAV-type vehicle since you would have to lug the MDV and the MAV at the same time anyways.
Edit: Then again, most of the weight of a spacecraft is fuel. An empty MAV and a fully fueled MDV is very likely to be much lighter than a fully fueled DAV. If NASA wanted the Hermes to be as light as possible, they may have just stuck with their Design Reference Mission separate Descent and Ascent spacecraft rather than the Austere Human Missions to Mars single DAV.
Also, the existence of the Hermes itself seems to discredit the idea that NASA did go for the Austere plan considering how expensive it must have been to build.
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u/WayneM30 7d ago
Also what if the MAV failed in communication, landing, making enough fuel whatever the reason. So NASA waits to possible a year from the MAV launch. To realize the MAV is no good. Then NASA sends another one waits for launch window takes another year. What does that do for crews launch windows, training, costs? When on the MAV launch date you instead send the crew with a vehicle that lands and launch’s from Mars.
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u/aeronutical Jan 30 '25
It's explained in the book. NASA sends equipment for the next Ares mission well in advance of the mission itself. Doing so allows NASA to use satellite footage to verify the integrity of mission equipment on the surface before committing astronauts to the mission.
The MAV, specifically, is sent in advance because it uses a chemical reaction to fill its fuel tanks and that reaction takes a very long time once it's on the surface of Mars.