Thursday, June 2, 2011

Let's go on a Mars Cruise!

A photograph of  the residential cruise ship "The World," docked in Melbourne as captured by wikipedia user VirtualSteve. Is this a good home for Mars Mission Control?

In the run up to this year's analogue space mission deployments at UWO, I'm reliving the good old days of 2008 vicariously through Andrew Kessler's account of the Phoenix Mission. In his book "Martian Summer," Kessler captures in plain language the energy as well as the highs and lows of working at Mission Control for a Martian Mission. I'll have more to say about the book once I finish reading it, but there was one early comment of his about an interesting countermeasure to working on Mars Time that piqued my interest. I'll get to that in a moment, but first let me describe what we mean by "Mars Time."

Each planet in our solar system is its own unique individual with their own size, mass, density, composition, distance from the sun and rotation rate about its axis (just to name a few attributes). The Earth's rotation rate is one revolution per 24 hours giving rise to our familiar concept of a "day." But that isn't true of all bodies in the solar system. For instance, Jupiter revolves on its axis once every 9 hours and 56 minutes of Earth time whereas Venus takes 116 days and 18 hours of Earth time to make one rotation. Tantalizingly, Mars' rotation rate is once every 24 hours and 40 minutes, making it exceptionally similar to the Earth in terms of the length of its day.

That length of day is very tempting for mission planners. You see, ideally, you want to stick to the day/night ("diurnal") cycle of the body on which you have landed in order to make most effective use of your resources. Venus and Jupiter are so far away from our circadian cycle that it would be impossible to work to the Jovian day or the Venus day. But the length of the Mars day is close enough to our own circadian rhythms that Missions usually push their staff to work on "Mars Time," at least initially. This means that the staff at Mission Control keeps a Martian Day which drifts by 40 minutes relative to the Earthly Day.

You might think that getting up 40 minutes later each day is a great thing! After all, who wouldn't want to be able to get an extra hour of sleep? But while that might be great for a couple of days, the 40-minute progression is relentless. Eventually you shift from working during the daylight hours into the nighttime and back again. Kessler describes operating on Mars as continual jet lag, and for many* the symptoms are not pretty. Those unpleasant symptoms include increased levels of stress, brain fog, and eventually immune system compromise. What they do to you are described in visceral detail by Kessler who lived through each.

There is a large body of research that shows that for most people, the body just cannot continue this cycle for long periods. As such, we had a team on Phoenix that monitored our health and provided countermeasures. The key to those countermeasures was stimulating the responses expected by our circadian cycle. Thus, you feel much better if you get light into your eyes near 470nm (very much like the blue of the sky) in your "early morning" and eat your meals on a schedule of breakfast, lunch and dinner that processes with you as you move around the clock. Doing those things are very hard when your "Mars Day" becomes decoupled from the "Local Day" wherever Mission Control happens to be.

But what if you could sync up the Mars Day and the Local Day here on Earth? I'm not talking about sending Superman flying around to slow down the Earth's rotation, I'm asking the hypothetical question about taking Mission Control and moving it relative to the Earth! Kessler, in a provigil-induced haze himself brings this idea up (p79), so I figured, why not add some technical rigor to the suggestion? Specifically, Kessler suggests a "Mars Cruise" in which Mission Control is located on a boat that travels from time-zone to time-zone, keeping pace with the Martian day to ensure it is close to being synced to the local day.

First of all, what direction is that? In order to keep falling back by 40 minutes, we would need to head West and since local true solar time (LTST) is set by your longitude, you'd need to move something like 10° of longitude per day. At the equator, the Earth's circumference is a little over 40,000 km which means you'd have to cover over 1100 km a day to make up 10° of longitude, or a constant speed of 46.3 km/h. As someone who grew up on an island, trust me - that's a fairly rapid speed for a large boat with all the trappings of a mission control on-board. And it would be worse than that! A quick look at the map below (courtesy of wikipedia) will tell you that there's a lot of land in the way at the Equator, and an actual route for a ship, shown in red, is much longer:

This image from the wikipedia article on circumnavigation shows the most popular maritime route in red which is much longer than 40,000 km ** 

Where might be a better place to do such a cruise? Again, we can turn to maritime navigation and the route that is classically termed the fastest for circumnavigation is the UK-Australia Clipper Route, popular in the 1800s:

Clipper Route between the UK and Australia as created by wikipedia user Johantheghost.

Ignore for a moment the segment of the route between Cape Horn in Chile and London, England and imagine a ship plying a flat line through the Furious Fifties. Here the route is much shorter than at the Equator and there is open ocean all the way around. If we take a line of latitude at 56°S, just south of Cape Horn there is only a little over 22,000 km to cross and a constant speed of 26 km/h will do the trick. If you go further south and keep close to land you get a route just outside the antarctic circle at close to 65°S which stretches for less than 17,000km and would require a speed of only 19.6 km/h (ok, you do have to divert north for the antarctic peninsula, but otherwise the continent is rather circular). Of course, you have to be careful not to go too far south or else the terrestrial day itself gets noticeably lengthened or shortened by the latitude.

There are immediately some issues that come to mind. While modern satellite technology means that you would easily be able to operate a mission control on a ship from the perspective of uplink and downlink, it's hard to process data and hold meetings on a swaying platform. In particular, the operation of the engineering models in the PIT (Payload Integrated Testbed) would become much more difficult (this is a great mental picture). Not to mention that they don't call those latitudes the "Furious Fifties" for nothing. Up until now, the chances of loosing NASA personnel on a robotic mission were small. If you load them all up on a boat and traverse some of the most treacherous waters on the globe for months on end that chance increases noticeably. Further, a bad storm could knock out the antenna, which would be really annoying if it happened a couple of minutes before the DDULT (Drop-Dead Uplink Time).

On the up side, we would be close to one of the Earth's best Martian analogue environments, the McMurdo Dry Valleys. Researchers could just go ashore to test their hypotheses! As well, due to the strong currents, this part of the Antarctic Ocean remains ice-free the whole year long.

Maximum Sea Ice Extent surrounding Antarctic in September, 2010. Courtesy of the Snow and Ice Data Center.

There's even a ship that already does something similar. "The World" is described as a floating city that travels endlessly from port to port. The 250 crew cater to the needs of 100-300 guests, which is just about the right size for a complete mission control. As well, the maximum speed of 34.3 km/h means that it could keep the pace with margin to spare. It wouldn't be a cheap cruise - berths cost from $600,000 to $13.5 million and monthly dues are $20,000 per suite! Assuming a 90-sol mission on "Mars Time" and a decent interest rate for NASA of 2% per year (they are the government, after all) the cost of buying out the ship for 90 sols would be on the order of $5 million, comparable to the salary commitment for 200-300 mission control staff for that time.

As interesting a thought exercise as this has been, I think we may have to consign this idea to the dustbin. On the whole, the risks and annoyances don't outweigh the benefits. We would probably end up driving SOC Manager Chris Shinohara ragged with logistics in this kind of a mission control. But there is one very good advantage. As mentioned by Kessler, the folks in charge of the ORTs (Operational Readiness Tests) sought to make things difficult for the Science Team in order to get them to bond. Running a mission from a boat circumnavigating antarctic waters would be sure to do that in spades!

*From some work I did with one of Edna Fielder's Colleagues, George "Bud" Brainard at Thomas Jefferson University I know that just like planets, people are individuals with their own variations. It turns out that when you remove all indications of the time of day in isolated rooms (no windows, clocks, etc), people don't all stay on a 24-hour cycle. Some speed up their day and others slow it down such that "natural" circadian cycles for most people range from 21 hours to 27 hours. Bud was working on understanding what kind of circadian stimulation exists on Mars, in LEO or on the Moon (this is where Peter and I came in - we produced the simulated lighting systems including some for places Astronauts are unlikely to visit anytime soon, like HD-209458b) and trying to devise lighting systems to compensate.

This was how I got caught up in the monitoring for Phoenix (yes, I was one of those folks with a "Trader Joe" bag Andrew talks about). Through that experience, I learned something interesting about myself: my natural circadian rhythm is about 25 hours, and I've got the actigraphy to prove it. So, in effect, I'm a natural born Martian! While everyone else was getting bleary, downing coffee like it was water and experimenting with wakefulness-boosting drugs, I took nothing and felt great (at least until later in the mission when I tried to jump 12 time zones in one day;) ).

** (in case you're curious, the yellow line shows the "antipodean" route, i.e. the route as projected to the opposite side of the Earth. It's a key metric for determining circumnavigation because you need to have traveled to the exact opposite point on the earth from your start at least twice HINT: look at the UK and New Zealand and you'll see what they're driving at)

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