Real Engineering on Simulated Mars

Remember those old math questions you had in algebra class?  Where water is entering a container at a certain rate and leaving at a different rate and you need to figure out when it’ll be empty?  Well, that concept is critical to the “Mark Watney doesn’t die” project I’m working on.

– Mark Watney, from the book “The Martian”

In the book “The Martian” (and, I’m assuming, the movie too, we haven’t seen it yet), Mark Watney performs a lot of calculations.  He has very limited resources to work with to keep himself alive.  For example, he calculates the amount of calories available to eat from the potatoes he grows, and, from there, calculates how many days of food he has left.  He also calculates the amount of water he needs to grow his potatoes and keep himself healthy.

Here on simulated Mars, our situation isn’t anywhere near as dire as Mark Watney’s.  However, we still have limited resources that we have to manage carefully.  As the crew’s chief engineer, just like Mark Watney, I perform calculations to understand how we’re using those resources.

I haven’t done any calculations involving potatoes or protein bars yet – our plants tend to be handled by Cyprien and Carmel.  My tracking is instead focused on our system resources: that is, power and water.  I perform these calculations on a daily basis, looking for patterns in usage and consumption, in a process known as “trending”.  Although it sounds remarkably tedious – and it usually is, when everything is working correctly – trending gives the ability to find the subtle hints that something may be about to go wrong, before they have a chance to wreak havoc on the hab.  For example, an unexplained uptick in the amount of water used per day can indicate that a leak has sprung somewhere, slowly draining away the habitat’s limited supply.

Of all the habitat systems, our power system most resembles the real systems that a crew would use on Mars.  Our electrical power is chiefly provided by solar panels, which generate electricity and charge a pair of large storage batteries when the sun is shining.  We use the power from these batteries at night and during cloudy weather.  If the batteries run low and solar power isn’t available, then a set of backup hydrogen fuel cells turn on to provide power until the solar panels start charging again, usually around 7 or 8am.  Unlike the solar panels, the hydrogen that powers the fuel cells is a limited resource. Unless the astronauts on Mars have a way to harvest usable hydrogen from the environment around them, they’ll have to wait roughly two years between top-ups.

Of all the numbers I look at every day, the number that interests me the most with this system is how much we power we use.  This turns out to be fairly easy to calculate.  The habitat’s computers report the amount of power being drawn by the hab.   I simply take the recorded numbers, drop them into Excel, and integrate numerically over time using the trapezoid rule – for those that don’t speak calculus, that just means I’m adding it all up over time.  This gives the total power we used in kilowatt-hours-per-day.  Or, as Mark Watney called them, “pirate-ninjas”.

Pirate-ninjas.

Pirate-ninjas.

Here’s a chart of our pirate-ninjas…ahem, sorry, kilowatt-hours-per-day.  The days that led us to run low on battery overnight and spend hydrogen are colored red.  Looking at the chart, there appears to be a rising trend, especially recently.  I can explain that: as we’ve gotten settled in, we’ve started up some of our opportunistic research experiments, including some that involve plant growth.  Grow lights and water pumps use a fair amount of power, and it all adds up.

I’ve also tried calculating the amount of power we could be generating every day.  I found this to be a little bit more difficult.  Our solar radiation meter, which is wired to the habitat’s weather station, measures sunshine in Watts per square meter.  I multiply that by the area of the solar array, multiply by the panel efficiency from the spec sheet, and integrate over time, which gives an estimate of how much power we theoretically have available each day.  I say “theoretically”, because I’ve found my results are a bit optimistic.  I’m missing several effects, such as aging and degradation of the panels.  I’m also not including variations in power generation with temperature.

It turns out that this calculation doesn’t matter a whole lot, though.  The nights that cause us to spend hydrogen tend to come after very cloudy days that don’t allow us to charge our batteries completely – no big surprise there.  But, on most days, our batteries are fully charged by around noon.  At that point, any power that isn’t being used immediately has nowhere to go – it’s radiated away as heat, and essentially wasted.  Our big limit on most days is our battery capacity; we simply don’t have a way to use all the power we’re generating in the middle of the day, even if we plug in everything we have!

This observation has led us to change our approach to energy use a bit: we have a few 12-volt marine batteries that we can plug in and charge during the day to capture some of that wasted energy.  Later in the day, we can use these batteries to power our plant-growth experiments.  We’re considering ordering more for a future resupply to capture even more energy.

I’ll also talk about our water usage.  Water reclaimers like the one Mark Watney uses are a real, but very expensive technology – NASA uses one on the ISS to process urine and evaporated sweat back into pure, drinkable water.  For that reason, we don’t have one here at HI-SEAS.  Instead, we simulate water generation and reclamation by receiving a delivery of water to top off our pair of 500 gallon storage tanks every few weeks.  In between deliveries, it’s up to us to use our supply carefully.

Water usage is even more easy to measure and track than power.  I simply take the tank level measurement each day at midnight.  The change from the previous day’s measurement gives the total amount of water used that day.

WaterUseThis chart shows our daily usage, as well as the amount remaining at the end of each day.  There’s quite a bit of variation – our daily usage is heavily influenced by whether or not we use the washing machine, which drinks a thirsty 20 gallons of water per load of laundry – but, on average, we use around 30 gallons or so per day, about 5 gallons for each of us.  That’s pretty good…in comparison, the average family of four in the US uses over 400 gallons of water per day!  We work hard to keep that number down: we have composting toilets that don’t flush.  We limit ourselves to a couple of minutes of water per shower, and only a couple of showers per week.  We capture shower and sink water, and reuse it to mop floors.  It also helps that we don’t have a yard to water, a swimming pool to fill, or cars to wash.

There are a couple of days in mid-September that stand out, though.  What happened there?  Another easy explanation: we had been notified that a water delivery was coming in a couple of days.  The tanks are topped off regardless of what’s left in the tank when the delivery arrives, so we decided to make as much use of the remaining supply as we could before the delivery.  On the first high day, Carmel took 80 gallons to fill up her aquaponic plant-growth experiments.  On the second day, we put as many loads of laundry through the washing machine as we could.

Bring Andrzej to MarsJust like Mark Watney, each day brings more numbers and more calculations.  But, as the mission continues and I gather more data, perhaps more patterns will emerge, allowing me to gain more insight into our systems.  For now, we’re heading into winter.  We tend to base our power usage on how well we’re charging the battery, so I’m interested to see how the changing seasons will affect our power consumption and hydrogen usage.

…in the meantime, if you happen to know anyone over at 20th Century Fox, please let ’em know we’d love to watch “The Martian” here on simulated Mars!


This photo's for you, Justin!

This photo’s for you, Justin!

I have a big group of friends I play board games with regularly back home in Denver.  Thanks in large part to the culinary stylings of our friend Ryan, our game night group is usually well-fed.  Justin, who is a frequent commenter on my blog posts here, occasionally whips up biscuits and gravy.  For our brunch last Sunday, we were able to whip up some biscuits and gravy from our supply of shelf-stable ingredients: pre-cooked bacon, dehydrated sausage crumbles, buttermilk powder, and some of the sourdough starter that Shey talked about in her Mission Day 14 blog post.  We haven’t figured out how to replicate chili dogs just yet, but this was a nice reminder of home.

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16 thoughts on “Real Engineering on Simulated Mars

  1. dave gingerich says:

    Andrzej, do you have a way to trend conditions inside the habitat? For instance, are you recording the indoor temperature, humidity, and CO2 levels? I suppose the habitat isn’t airtight so that aspect isn’t high fidelity simulation …. but I’d be interested in how those levels change once your indoor plant life increases.

    I suppose a realistic indoor simulation with stale air, smells, and hard-to-control fluctuations in temperature and humidity would add another stressor to simulation and create interpersonal conflict.

    For instance, your crew cooks in the habitat — what is done with the cooking odors and humidity?
    Also, I imagine a composting toilet isn’t pleasant to host in your living room. Do you expect that it could become a problem?

    Your latest post just got me thinking about habitation stressors and whether HiSEAS has similar, less, or worse than current/future space travel and habitats.
    -daveg

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    • A lot of good questions Dave…enough for another blog post. So, rather than answer here, I’ll do just that! I’ve got a post on another topic that’s just about ready to go, so that’ll be next in line afterward. Thanks for the writing inspiration!

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  2. robert fostyk says:

    I find myself curious about a lot of the details that you write about but I am surprised that the solar panel and battery storage capacity was not sized by the habitat consumption rate experiments and all. I would think the hydrogen would be emergency use only such as long term overcast skies. Also, I am surprised the way water is replenished. I would have thought NASA would have loaned a water reclaimer for this experiment. I am thinking that this is one of the most critical parts of your undertaking and it would be nice to find out any problems now. Well thanks for all the info. It is appreciated.

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    • Thanks Robert!

      The hydrogen is essentially supposed to be backup only (overcast skies turn out to be a big driver of whether we burn H2 or not). It does take some effort on our part to stick to that, though. We have a few things in the hab that can be absolute power hogs: the treadmill and the kitchen, in particular. If we’re cooking a big dinner and not paying attention to the weather outside, it’s really easy to burn enough battery to put the system on a path to leaning on the fuel cells early the next morning.

      We got a bit cavalier after the first month of the mission…weather was good, and we didn’t hit the hydrogen at all. Over the last couple of weeks though, we’ve had to deal with cloudier days, and a malfunction in one of the fuel cells took us by surprise. Turns out that having to wake up and suit up at 4:30 in the morning to go outside and inspect a faulty fuel cell has a tendency to get your attention! As a result, we’re getting a bit more conscientious about how we use power, especially later in the day.

      We’d love to get a water reclaimer, but, sadly, it’s a bit outside the budget of our program for now. On the other hand, our main power system designer would love to get his hands on and install a hydrogen electrolyzer, which would have a big effect on power use.

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  3. Hi Andrzej

    You voiced concern as to whether astronauts on Mars could find a way to harvest usable hydrogen from the environment around them.

    I googled “make hydrogen on Mars” and found that Vibha Srivastava uring her Masters program developed an experiment to extract the in-situ resource water from the Martian surface soil. She used the same experiment set up to extract water and collect hydrogen from it at MDRS in Utah Desert as a part of crew 143 in early 2014 as detailed in the final mission summary at http://mdrs.marssociety.org/home/crew-134/final-mission-summary.

    Thanks
    Kenbigtrain

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    • Thanks for passing that along Ken! Being able to harvest hydrogen on Mars, and not having to rely on resupply, would be a major help to the crew, and would add a level of safety – a leak, for example, wouldn’t be as big an issue if there’s a ready way to fill the thanks back up. I’m glad to see active work going on in the area.

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  4. Hey Andrzej. Thanks for the photo! I saw it on FB as well. I have a little mini blog going on FB regarding my dinner each night of my first Fall Break (we get two, so that is great). One night I had B&G and gave YOU a shot out. That is hilarious.

    I started reading this article last night at 10:11pm local time. I immediately looked up The Martian at my local theater. There was a 10:30 showing, in 3D! I ran out to immediately watch it. I liked it. It made me think of you and your situation often.

    The first few questions have to do with sMars, specifically the s part. Do they throw you the occasional problem to work out? I assume the whole point is to naturally find where the problems occur, but I would not put it past anybody to throw a simulated problem. I know there are budget concerns compared to a mission to mars, but who set up your hab, and when? I would think the first of these sMars missions would have to do that. Is yours the first? It sounds like MDRS crew 143 has something similar. I assume you are not setting up the hab, which leads me to my next question. What do you do on sMars on a daily basis? What are your jobs and projects? I remember you had your actions planned to the minute on HERA. Are your projects planned by somebody, with a little time/room to do your own things?

    After the movie I was unable to stay awake long enough to come back to your blog. I did this morning. I may have written about it last time, but I definitely will this time. Your power/water consumption reminds me a LOT of my summer camp. A lot. We had solar panels that provided power. Our power was responsible for a pump in a well. Water was dependent on power. Water was also the biggest drain on our power, through toilet flushings and sink usage (no power is used to flush a toilet, but to resupply it with water). When multiplied by 24 kids and 6 adults, it can become problematic. Cloudy days were especially a problem in the Rockies. I assume our system was a little cheaper and we were probably a LOT less trained on how to deal with it. It was always an issue.

    Basically, your spending a year on a remote island isolated from civilians (like I did on DGar), in a situation like my summer camps. I have so many experiences to drive my replies.

    Well, when you started and I started replying was back in Late Aug., early Sep.. It is now mid Oct.. My school year has hit the first break (so nice!), and you are starting to have enough data to notice trends. You are trucking along.

    -Justin

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    • Sorry for the delay, I’ve been busy the last few days, and wanted to get a good amount of time to sit down and answer your questions.

      From what we’ve been told, they don’t plan on throwing any simulated problems at us. In official NASA parlance, these sorts of things are called “manipulations”…we had a bunch on HERA, though I’m not allowed to disclose the details. Anyway, they’ve found that the hab just has enough problems happen naturally that they don’t need to add any additional engineering problems on top of that. As it turns out, we’ve been working on an actual problem with one of the two fuel cells for just over a week now. They do, however, give us bi-weekly geology tasks that require us to EVA to take measurements, as real Mars crews would have to do the same sort of thing.

      The hab itself is actually privately owned by Henk Rogers, the man who owns the rights to the video game “Tetris” in the United States and founded The Tetris Company. I don’t know exactly when it was built, but it was sometime before the first mission, which started in April of 2013. He’s got personal interests in Mars exploration and sustainable energy, and built the hab at his own expense to further research in both – our power system is an exact duplicate of the one he has in the energy lab on his private ranch. Yeah, he has his own energy laboratory. And his own simulated Mars base. He’s kind of awesome like that. He also throws a mean luau!

      The hab was mostly set up when we got here, and largely in the condition the Mission III crew has left it, though the mission support crew had done some major rewiring of the computer networks between missions. Our first couple of days were taken up by inventorying what was actually here, and I spent a couple of weeks in the back room making adjustments to the new network and server setup, but the hab was pretty much ready to go otherwise.

      We’re at the point where we’re essentially doing normal operations now. We don’t have strict plans assigned like we did on HERA, but we still end up pretty busy. I spend time doing the engineering calculations I talked about, and working on fixing whatever’s broken, either with the hab or if someone needs help fixing or setting up their own experiments. We have crewmembers leave the hab on EVA two or three times a week for various reasons, and I’m usually either one of the folks outside or on the radio back in the dome serving as “HabCom”. We’ve set aside Tuesday mornings to respond to all of the requests from media we’ve received, and we’d like to start picking up more school outreach opportunities. We also have an hour or two of dedicated psychological research tasks for NASA four days a week. Sundays are my day to cook for the crew, so I spend most of that day in the kitchen. We also set aside an hour or two on Sunday as cleaning time for the hab…not surprisingly, I usually end up responsible for cleaning the kitchen. We try to work out every day, and I also try to set aside an hour or two every two or three days or so to write e-mail home.

      It sounds like your experiences at DGar and working at the summer camp have a lot in common with what we’re doing here. Cloudy days are a problem for us too, for the same reason (we’ve already had to rearrange today because the clouds came in early). If you have any experiences or wisdom you’d pass along, I’d love to hear it.

      Anyway, always good to hear from you Justin!

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  5. Anonymous says:

    Hey Andrzej. Just wondering, why don’t you use the old method taught in primary schools to get water? I mean, the one where you urinate in a basin, put a cup in the middle, cover the basin with plastic, and put a stone in the middle?

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    • Good question!

      It’s not something we’d really considered. We might have issues with having an open container of urine sitting out or the space it’d take up in the hab, but I don’t see any reason it wouldn’t work otherwise. That being said, without getting into too much detail, as it’s still active research…one of our crewmembers is performing experiments using a similar method to extract water from the volcanic rocks outside.

      We have been recycling urine another way, though…we’ve occasionally collected urine to reuse as plant food in some of the growth experiments.

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    • So, a follow up to my earlier comment. It’s been a couple of weeks since we’ve received any rain, so the ground is extremely dry. The crewmate I was talked about couldn’t pull any water out of the parched ground, and so has converted one of the experiments temporarily to distill urine until we get more rain again. Just like you’d suggested!

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    • The biggest adaptations for me have been learning how to live more efficiently and keeping touch with people “back on Earth”.

      We have limited supplies out here, and though we can get resupplied if absolutely needed, we’re expected to conserve as much as we can. For water, we take short showers – rinsing for a few seconds, turning off the water to soap down, and then quickly rinsing off. We reuse shower and sink water to mop the floors. We hand-wash some of our clothes to save water.

      Power’s a bit more constrained. There’s no wall outlet or power line up here on the side of Mauna Loa for us to plug into, so if we run out of power, we have no way to get more until the sun rises and starts charging the solar panels the next day. We have the hydrogen fuel cells as a backup, but one of them has been giving us some trouble over the last couple of weeks, so we can really only rely on the solar panels and battery until we get that fixed. We’ve got just enough battery storage to get through the night with a bit of margin, so we’ve had to be careful to make sure they’re fully charged at the end of the day. We’re doing things like turning off lights and appliances when they’re not in use, only cooking with the oven or using the treadmill in the middle of the day when it’s sunny outside, turning our heating down, that sort of thing.

      These aren’t anything that we couldn’t be doing back home to live more sustainably. But at home, if we ignore the impact to the environment, the worst thing that happens when we waste water or power is a bigger utility bill at the end of the month. But here, we run the very real risk of running out if we’re not careful with how we use our resources. That gives a lot of incentive to learn how to be less wasteful.

      For keeping touch with friends and family, we have e-mail, and can send photos and videos. But it takes a lot of effort to stay in touch with people this way. It’s really easy to talk and have a conversation with someone in person or over the phone, but it takes a lot more time to use e-mail. If I have a busy day – lots of NASA research, cooking, perhaps having to fix something – it can be hard to carve out enough time to get away from the responsibilities to answer all the questions from home and write something meaningful back. Sometimes the network has problems, and that slows things down too…I ran into a problem a couple of days ago when I was trying to send some video messages home, and couldn’t get them out until the next day. But that’s what we have to work with, so we work hard to make sure the folks back home know they’re on our mind.

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  6. Noel Hughes says:

    You guys haven’t seen The Martian YET?!?!?!?!
    This is a national disgrace!!! And, BTW, 20th Century Fox is missing a huge PR opportunity (although since The Martian appears to be a huge blockbuster, maybe they don’t need it) by not connecting the movie to you guys – crew reaction to first viewing, problems overcome similar to Watney’s , etc. etc.
    Noel

    Like

    • Heh, nope. There was some talk with Fox about sending us a screener, after they found out that we kept telling folks in interviews that we hadn’t seen it yet…but it fell through.

      From what I understand though, the movie’s coming out soon on DVD, right?

      Like

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