November 27, 2011

Men on Mars: Why it won't happen soon

Wikipedia has an entry entitled "Manned mission to Mars." Since I started writing my thoughts independently of looking at it, I'm going by what I have written, with brief references to it.

Shorter take? Illustrations of such a trip look great, don't they? Well, drool away, because those illustrations are about as close as we're getting in your lifetime or mine to landing people on Mars, in my opinion.

There's three main reasons why that image is all we'll be seeing in the foreseeable future. They're called space psychology, space safety and space engineering.

And, most of those are connected with the idea that, at minimum, we're talking 1.5 years of travel, with distances far greater than lunar travel. And, the low-fuel journey, for one-quarter of what the "fast" trip takes, involves 2.8 years, more than half of that on Mars.

This will tax engineering, certainly tax human psychology, and without massive advances in shielding from cosmic rays, will kill astronauts -- not on the actual trip, but more surely, and with at least as much life reduction on average, as smoking two packs of Camels a day.

In short, until we address all of this, we're not even close to sending a manned mission to Mars. We're at least 30 years away, in my opinion, and that's plenty of time for improvements in robotics in particular, and unmanned spaceflight in general, to push that timeline back even further.

Details on the "why" of all of this below the fold, updated to reflect how NASA's current manned mission planning is woefully inadequate, starting with the spacecraft.




1. Space psychology. A trip to Mars will take about 400-450 days round trip. Once on Mars, astronauts either have to wait about 1.5 years for an optimal window for return, or else burn much more fuel to get back to Earth after a relatively short one-month stay. Details of both options, as well as a faster outward trip, are here. Having to burn 3x as much fuel for a faster outward trip, and 5x as much for an earlier return is not a negligible consideration.

Here's the bottom line:
A. Hohmann transfer both ways plus 1.5 years on Mars = 2.8 years.
B. Fast trip out plus 1 month on Mars plus slow trip home = 1.5 years.

So, we've got astronauts away, well away, from Earth for a minimum of 1.5 years. And, if we want to maximize the "return" on going to Mars, we've got them there three years.

Even in near-Earth orbit, and with less than a year's time, we've seen psychological stress on some outer space crews. Yes, there have been simulated Mars trips, but, given the many minor things that can go wrong in real space, and the simple psychological factor of knowing that Earth is "just outside the door," I'm not sure how well you can simulate the psychology of such a trip.
2. You certainly can't simulate space health effects. As for the effects of solar wind? In its articles on magnetospheres and solar wind, Wiki talks about Mars' lack of magnetic field and results thusly: Mars, with little or no magnetic field, is thought to have lost much of its former oceans and atmosphere to space in part due to the direct impact of the solar wind, with an atmosphere now 1/100 that of Earth. Venus, with its thick atmosphere is thought to have lost most of its water to space in large part owing to solar wind ablation. (The solar wind stretches the "downwind" side of Venus' atmosphere almost to Earth.)

For just about all the trip, astronauts will be outside the protection of Earth's magnetosphere. Dangerous, in terms of radiation? Yes, enough to make some people rethink the whole idea as potentially fatal:

"The estimate now is you would exceed acceptable levels of fatal cancer," said Francis Cucinotta, chief scientist for NASA's space radiation program at the Johnson Space Center in Houston. "That's just cancer. We also worry about effects of radiation on the heart and the central nervous system."

Cucinotta says these estimates do take into account protective shielding around a crew vehicle, probably some form of polyethylene plastic. Lead shields actually create secondary radiation when struck by cosmic rays, while water, perhaps the best form of protection, would have to be several meters thick to get enough protection. ("Houston calling Water Balloon 1, do you copy?") 

Lead and water, in any case, are very heavy for the quantities that would be required, making them an expensive shielding to launch.
And, now, March 8, 2013, we read about how a fair chunk of the memory of the Curiosity rover got zapped by a cosmic ray.

And then, there's the gravity issue. We'd have either 450 days of zero gravity and one month of 1/4 Earth gravity, or 450 days of the former and a little more than that of the latter.

At the same time, while Mars' gravity is low, low enough to not be "good" for Earth-accustomed astronauts, it's heavy enough to be problematic after 225 days of no gravity, as the story above notes;

"What happens if they land on Mars and try to lift an object that's fairly or reasonably heavy, they could herniate their discs," said Alan Hargens, an orthopedic surgeon at the University of California San Diego who studies the effects of gravity on astronauts. "One of the main issues is that when they arrive at Mars, there's nobody there to take care of them. If they have some issue due to de-conditioning in that six month period, they'll definitely have a problem."
It's true. Even with treadmills and other gravity simulators on the spacecraft, in the first few days on the Martian surface, there would be a high risk of muscle pulls, muscle and tendon tears, hernias and broken bones, and possibly heart attacks due to stress.

Because you'd definitely need "backup," that means not just one, but two members of each crew would have to be physicians. (One could be a psychiatrist, to address issues under point No. 1. We're going to need a psychologist anyway.

There's also another medical problem that's already hit some shuttle/ISS astronauts: Vision problems.
According to one NASA survey of about 300 astronauts, nearly 30 percent of those who have flown on space shuttle missions — which usually lasted two weeks — and 60 percent who completed six-month shifts aboard the station reported a gradual blurring of eyesight.
It's obviously progressive. A trip to Mars would have worse effects on a higher percentage of astronauts. It's fairly serious, and so far, recovery has not been complete in those who have suffered it.

3. Space engineering. This is going to subsume several things.

Let's start with a bottom line that also relates to point 1: the communication time gap. When Earth and Mars are at opposition, it's 20 minutes one way for communication.

So, if an Apollo 13 type event happens, during almost all the journey, astronauts are on their own.

That affect Earth engineering. We can't have an Apollo 13 problem, as far as improvised fixes, of trying to mate square canisters and round holes or vice versa. Can't have it. That means that the U.S. government, U.N., EU, a consortium or whatever, has to ride a very, very heavy herd on private contractors. That, in turn, ramps up the price.

Second, radiation shielding. Unless you have astronauts who sign "death sentence waivers," our current engineering simply can't protect against it. Period.

Third, crew composition. Let's say we have a crew of seven.

As I noted above, we have to have two M.D.s, one a psychiatrist. Both to study human changes in space and explore Martian life, person No. 3 is a Ph.D. biologist, of course. No. 4 is a mechanical engineer who's spent time at all those private contractors' sites. (Every astronaut, though, for reasons mentioned above, will have a crash course in engineering.) No. 5 is a geophysicist. No. 6, whether military or not, as commander, has to have a leader's presence. No. 7 is No. 2 in charge, and No. 1 in piloting skills. These two may have some backup training in sciences, but, their primary backup training will be the leads, along with person No. 4, in engineering and constructing a Martian base, on the first flight, which will be the high-fuel, quick-return version.

Of course, we' re not getting there anyway. But, that would be a minimum. Arguably, even on the first flight, you'd want an eighth person, another engineering/construction person. That then said, what crew capsule size are we talking about? And, are we conforming a crew to a capsule or vice versa? In either case, seven is a minimum, I think.

Don't forget all the food that means. All the water conversion and air filtration that means, with multiple redundancies on systems.

Meanwhile, NASA's Orion crew vehicle only seats four. NASA's skimping a LOT on both human backup needs, legitimate crew needs and space psychology issues. More reason to say both that we're not going to launch a manned mission to Mars any time soon, and we shouldn't, at least not under current planning.

There's one more "engineering" option. Let's call it "financial engineering." Throwing aside radiation, building a spaceship that can offer some exercise protection against zero-G debilitation, be big enough to offer some small bit of buffer against space psychology, be big enough to, over a few trips, carry Mars base construction raw materials, etc. ....

Will cost at least $1 trillion in today's money to build and launch.

The U.S. is not doing that alone. And even a consortium isn't likely to do that. Money, engineering, and project outsourcing arguments will torpedo that. And, given cost overruns private contractors have had with NASA in the past, that $1 trillion estimate might be low.

Curiosity rover
Meanwhile, as the launch of the Curiosity rover has shown, and this slideshow of future projects illustrates, NASA has PLENTY of unmanned planetary exploration it can do.

I can understand a gung-ho, headline seeking, science-challenged cowboy like George W. Bush promoting a manned trip to Mars in our lifetimes. Scientists, especially astronomers, who know better, oughtn't be doing that.

I can also "understand" Apollo-era astronauts still trapped in a Cold War mentality, of wanting us to do "The Right Stuff." But, the right stuff today is unmanned exploration of anything further away than the moon, until further notice. And, if the idea of manned lunar missions is primarily to "practice" for Mars, well, we can save that money, too.

Oh, and private space travel touters? Please. Elon Musk would have to charge $500 million a trip to have any chance of scrambling up money for Mars, and as opposed to $20 mil to fly to the ISS with the Russkies, nobody's coughing up that money.

And, as for would-be professional, not tourist, astronauts? Lobby NOAA to start an aquanaut program instead. No, seriously. We could benefit more from manned oceanic research than from manned space missions.

2 comments:

Sheldon said...

Are you recycling posts, or is it deja vu?

Gadfly said...

Updating, but moving up the queue if I think the update is significant enough. Given what I was just reading about Orion, plus the launch of the unmanned Curiosity, I moved it up.