|Properly measuring and protecting against Martian radiation will be key|
to any manned mission to Mars./Space.com photo
That's because, as Space.com notes in a great new piece, we're just starting to figure out what we need to know about cosmic rays. And, the problems will be on Mars, not just in flight.
Let's take a peek at it, before doing an update on the possibility, and needs, of an actual scientific mission:
The Mars rover Curiosity has allowed us to finally calculate an average dose over the 180-day journey. It is approximately 300 mSv, the equivalent of 24 CAT scans. In just getting to Mars, an explorer would be exposed to more than 15 times an annual radiation limit for a worker in a nuclear power plant.So, double that for the return trip. Add 50 percent, off the top of my head, for time on Mars. That's 60 CAT scans, or 37.5 times the power plant worker's limit. Or, 750 mSv, which is 75 rem. Per Wikipedia, we're at a lifetime dose for a nuclear power plant or similar worker.
In short, while a trip to Mars isn't going to turn an astronaut into the cosmic-ray version of Frankenfood, without at least some shielding, it's going to definitely increase his or her likelihood of cancer. And, especially with men, it's going to increase the likelihood of sterility.
That said ...
Is this doable? Yes? Any time this decade? No.
It is a big sum to do this, unless we want a one-way trip, which somebody likely would volunteer to do. I think setting a target date of about 2035 allows out years to fatten that budget, do the R&D on radiation shielding, use more robotic missions to focus what a manned mission should do, etc. That also allows NASA plenty of time to work out details of a joint effort with Roscosmos, the European Space Agency, and maybe other partners.
Also, our current rockets are too small, specifically capsule size. As I've blogged before, unless you want to do the 1-day stop-and-return to have the lowest-energy return trajectory, you've got to have more than three people on that mission. And, that adds up to additional weight, space and food, plus additional weight and space for the exercise area. Mars' gravity is enough more than the moon's that, without adequate exercise in flight, an astronaut is liable to break a leg on landing.
That 2035 tracks pretty closely with the "30 years away" of my original blog post.
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 "cool" images are 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, beyond the illustration, we have to do R&D on human physiology for a long journey in "zero gravity," a certain amount of exploration into 1/4 Earth gravity, then a long journey back into zero gravity. We have to do the psychological R&D, more rigorous than Russia's mock trip to Mars, on a capsule of as many as seven people confined together for 6 months or more, and, on Mars, as far away as 20 minutes, one way, by communications link.
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. The Russian mockup was far short of that. First, they had the knowledge they could bail. Second, it only simulated a one-way trip; the time on Mars and the return time was not in the simulation.
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."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.
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.
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.
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.
However, Boeing's new capsule (update, May 8, 2015) does seat seven, and does so in comfort, style and modernity, as this story details, complete with the photo and more at the link.
Details note that the pilot's seat has had traditional switchgear replaced with tablet-like interfaces. In turn, that reduces cabin clutter.
Plastic has replaced metal in a lot of places, which reduces weight.
It generally looks much more ergonomic.
Now, this is being targeted to low-Earth orbit, for flights to the International Space Station and commercial use. But, the size is right and general design elements are right. No reason why something based on this couldn't be the Mars craft.
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. See above.
Partnerships also need to to "R&D" on the willingness of even the biggest government joint venture to shell out that much.