Thanks, Seth and Mat -- I guess we'll just have to work on generating an artificial magnetosphere! But even if such a thing were possible, that wouldn't shield the crew from micrometeorites. I'm starting to understand the huge difficulties of space travel. -- Joe ------------------------------ On Thu, Nov 29, 2012 11:44 AM MST Seth Jarvis wrote:

Hi Joe,

No, the problem is with high speed solar protons and other nuclei that are part of the solar wind. The ISS is currently within Earth's magnetosphere, which does a great job deflecting these electrically charged particles. Earth's magnetic field funnels them to the poles, hence the aurora.

In interplanetary space you'd have the fun of worrying about micrometeoroids _plus_ the equivalent radiation of a chest x-ray per day or if you're lucky, per week. You'd need more mass between you and the solar wind on an interplanetary journey of any duration (like 3 years) to survive with your chromosomes intact.

The Apollo Command Module provided astronauts with more shielding than the ISS does. The LEM was pretty flimsy in this regard, but it wasn't designed for a transit of the Van Allen belts, its where the crew would spend most of their time, and it was only intended to house astronauts for a couple of days. Apollo-era LEM spacecraft couldn't provide a survivable level of radiation protection for more than about 10 days on the Moon.

In fact, the ISS crew have a system of "where can I hide" designated areas on the ISS when ground controllers send a warning of a solar event. They go to parts of the station that have more shielding than others and wait it out.

Seth

-----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Joe Bauman Sent: Thursday, November 29, 2012 11:33 AM To: utah-astronomy@mailman.xmission.com Subject: Re: [Utah-astronomy] Mars exploration

Thanks for a neat analysis, Seth. If automated supply ships met the station at various points in its travels, that would reduce its load. I don't understand the shielding problem because the astronauts already can spend a year on the station as it is -- is this problem due to higher radiation closer to the sun?

------------------------------ On Thu, Nov 29, 2012 9:57 AM MST Seth Jarvis wrote:

...

What a COOL thing to think about!

The ISS would need to be reinforced pretty substantially to withstand the accelerations needed to get it to Mars in a reasonable amount of time - say something on the order of 18 months. The ISS currently masses 420,000 kg. Maybe if you're lucky you could get the whole thing structurally ready to go to Mars at a mass of 500,000 kg.

Then there's the weight of the food, water and air for the crew for what would have to be about a three year mission.

Then there's the weight of the extra radiation shielding you'll need since you'll be in interplanetary space, beyond the protective bubble of earth's magnetosphere.

Then there is the mass of the fuel and rockets to power the ISS onto a trans-Martian trajectory.

Then there's the mass of fuel needed to slow it down so it can be captured by Mars' gravity.

Then there's the mass of fuel needed to leave Mars and return to Earth. Although it seems counterintuitive, going from an outer planet to an inner planet actually requires _more_ fuel than the original out-bound trip.

If you look at the fuel requirements to get the Mars Science Laboratory headed to Mars, excluding launch weight, one-way, to get a grasp on the payload mass - to - initial vehicle mass ratio as a guide, then you're still looking at a fuel load several times the mass of what you're trying to get to Mars and back. A few hundred metric tons of fuel is probably a very conservative estimate for how much fuel you'd need to carry. With bracing, shielding, extra rockets, fuel and life-support consumables for three years, you've got to be looking at a total mass of a few thousand metric tons.

In other words - don't hold your breath waiting for NASA to send the ISS to Mars.

But it _is_ a cool idea. Sort of a geekier version of "Space: 1999."

Seth

-----Original Message----- From: utah-astronomy-bounces@mailman.xmission.com [mailto:utah-astronomy-bounces@mailman.xmission.com] On Behalf Of Joe Bauman Sent: Wednesday, November 28, 2012 6:10 PM To: utah-astronomy@mailman.xmission.com Subject: [Utah-astronomy] Mars exploration

A question for the group: what is the feasibility of attaching propulsion units to the International Space Station and taking it out of Earth orbit, into Mars orbit, and back again?

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