Topic: Earth to Mars voyage radiation shielding.

[Nemesis]

Link to full article

Burrowing inside an asteroid whose orbit carries it past both the Earth and Mars could protect astronauts from radiation on their way to the Red Planet. The idea is being investigated with funding from NASA.

[NJAntman]

Reminds me of Heart of the Comet by David Brin.

[Commander Maxillius]

sounds like a waste of time and resources.  You'll still need a spacecraft to get to the rock, and there's the added trick of leaving it at the proper trajectory.  Also, the ship will still need to be shielded, so if it's safe enough to be in space at all, shouldn't it be good for the whole trip? 

As a side note, what are the radiation levels on Mir?  Wait, it burned up didn't it?  Don't suppose anyone has the readings on that before it reentered?

[Nemesis]

sounds like a waste of time and resources.  You'll still need a spacecraft to get to the rock, and there's the added trick of leaving it at the proper trajectory.  Also, the ship will still need to be shielded, so if it's safe enough to be in space at all, shouldn't it be good for the whole trip? 

The time to rendezvous would be relatively short compared to the whole voyage.  A radiation level that could be taken for that time would be unacceptable for the whole voyage so the ship would not need shielding at the same level as it would if it was making the whole trip.  Also if the solar radiation was high the launch could be cancelled until the next pass but not if it were high part way through the trip.

Also if the asteroid was used on repeated trips it could be customized over time to add facilities.  It could even be mined for materials to extend the habitable zone or even for use on Mars itself.  Imagine if the crew spent part of the time enroute making their own fuel or a space station to be left in Mars orbit of materials found on the asteroid.  It could be very economical.

[Just plain old Punisher]

The space station was still within the earths protective electro-magnetic field. Once you leave that field, doses of stellar and background radiation go up significantly.

[Soliton]

Doesn't most of the radiation worries come from our Sun? Maybe instead of burrowing into a rock, they could just use one as a moving shield, launching and travelling so that they always have something solid between them and the Sun. To actually use a big rock as a ship would be very expensive fuel-wise and to propel an ungainly rock might be more difficult than planned.

Also, we are totally broke. So until we fix that problem, we aren't going anywhere.

[Vipre]

Interesting, but if you hollow out the asteroid too much wouldn't that affect the mass and as a result it's orbit? That would put the brakes on using it as material for construction wouldn't it?

On a side topic, how come I can't remember ever hearing about orbital construction yards? Is this not a viable option to "Building shielding on Earth to launch with the spacecraft would add a lot of extra weight to the vehicle and would increase the cost of the mission as a result."? You could build and launch the shielding separate from the main craft then assemble it in Earth orbit.

Not to mention building spacecraft in orbit for lunar and planetary missions. We need a real space station in orbit not the tinker toy we have now.

[Nemesis]

Interesting, but if you hollow out the asteroid too much wouldn't that affect the mass and as a result it's orbit? That would put the brakes on using it as material for construction wouldn't it?

There is a lot of excess mass in an asteroid even 1 mile across compared to what would be needed for shielding.  Any useless material (slag from smelting for example) could be just packed on the surface to maintain shielding after being dug out of a volume to be inhabited and processed for useful minerals.

To actually use a big rock as a ship would be very expensive fuel-wise and to propel an ungainly rock might be more difficult than planned.

The concept isn't to use it as a ship but as a natural raft.  Board it and just coast with it on its natural trajectory as it orbits on a path that takes it near to both Earth and Mars.  No propulsion used on the asteroid just for the ship and crew to rendezvous with it and be carried well shielded to the destination.

(See cycler for an artificial version)

[Tus-XC]

Interesting, but if you hollow out the asteroid too much wouldn't that affect the mass and as a result it's orbit? That would put the brakes on using it as material for construction wouldn't it?

Technically, yes, however in comparison to the sun the mass of the astroid is so insignifcant that it would have little to no significant effect on the orbit.  Oribts can, using the restricted two body equation (ie no drag), be determined by their position vector and velocity vectors, and there is usually little need to account for mass especially if one of the masses is several orders of magnitude greater than the other.  Now what would happen is that you would have a change in kinetic energy by hollowing out the astroid, but i would wager that there would be very little, if any, change in the velocity (which btw, determines your orbit)

for more info check here and read the sections entitled Newton's Modification of Kepler's Third Law and Two Limiting Cases

[Soliton]

If you affix yourself to the surface of a rock, you will then have to orient that rock to make it useful as a radiation shield. That will take fuel.

In thinking about this idea, I really doubt there would be many useful candidates. Any big rocks that venture near either the Earth or Mars will be affected by the planet's gravity and most likely propelled into a different orbit. Probably all the rocks out there are in either pretty regular orbits (like planets) or in very eccentric orbits (more like comets), neither being terribly useful for this scheme.

[Nemesis]

If you affix yourself to the surface of a rock, you will then have to orient that rock to make it useful as a radiation shield. That will take fuel.

You dig in to the interior.  The asteroid can rotate all it wants and you stay shielded.

They do include an option to just stay near it but then the plan is to detach material and make a shell around the ship.  Seems like a lesser idea than digging in to me.

In thinking about this idea, I really doubt there would be many useful candidates. Any big rocks that venture near either the Earth or Mars will be affected by the planet's gravity and most likely propelled into a different orbit. Probably all the rocks out there are in either pretty regular orbits (like planets) or in very eccentric orbits (more like comets), neither being terribly useful for this scheme.

Such orbits are semi stable and when an asteroid gets into one it can stay for decades or millenia.  Approaching first one planet then the other and then returning.  The study has already identified 40 candidates.  That would seem to be enough.

[Commander Maxillius]

just seems to me that cheaper doesn't necessarily mean better.

What they should do is build an Intrepid-class starship then put in the required tech to make it work when it gets invented.

[E_Look]

Reminds me of Heart of the Comet by David Brin.

Or maybe Startide Rising by the same guy: the Earth ship slips under the hull of a dead enemy's ship for a short time to fool the other pursuers.

[Nemesis]

Or maybe Startide Rising by the same guy: the Earth ship slips under the hull of a dead enemy's ship for a short time to fool the other pursuers.

It sometimes seems like the SciFi authors beat the scientists all the time.  Using a comet as shielding for a ship has been done in SciFi for a number of years.  The earliest I recall offhand are in The Jupiter Theft where the first human (sublight) starship is leaving embedded in a comet that is both shielding and fuel tank or The Nitrogen Fix where aliens travel around the stars in comets.  For movies Life Force had the [spoiler]"Vampires" travelling in Halley's comet[/spoiler]