Space craft shielding

[holmec]

nacnud wrote in my "Space ships and vehicles" post<br /><br />"I don't know if future systems will be able to get away with being as lightly built as the Apollo vehicles were. For example a reusable Luna Lander that was stored in space between visits would probably have to have similar meteorite protection as the ISS, plus a heavier blast shield if the same engine is going to be used for decent and assent."<br /><br />Here is my next question.<br />With the physics we know, what shielding would different Astronaut carrying Space craft need for protection against: cosmic rays, debris, dust, solar stroms...etc??<br /><br /> <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[vogon13]

Whipple shields on comet exploring craft have been adequate, so far, but if it's my arse in the capsule, I want a meter of titanium, thank you very much.<img src="/images/icons/laugh.gif" /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[holmec]

What about a magnetic field encompasing the craft (like earths magnetic field)? Would that provide some shielding? <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[spacester]

Working without a net here . . . the following is all very much IIRC:<br /><br />The best two materials for blocking both CBR (Cosmic Background Radiation) and CME stuff (Coronal Mass Ejection) are water and polyethylene. This statement has nothing to do with their expense in dollars, they are flat out the best two materials, pound for pound at blocking the two kinds of radiation.<br /><br />I don't remember exactly which one is better, I think PE - cheap plastic - is better at blocking CBR and liquid H2O is better at blocking CME stuff by a little bit each way.<br /><br />So this long exposure spaceship designer immediately is thinking about plastic tanks filled with water around the perimeter of the habitat volume, and maybe a cylindrical tank at each end as well.<br /><br />An 8 inch wall of water within a tank with one inch thick walls would provide fantastic protection for Mars travelers and dwellers. More would be required for the "fallout shelter" needed if you've got a big blast coming at you from the sun - uh about 45 minute long events IIRC.<br /><br />An interesting factoid is that the Suns 11-year cycle (from solar max to solar max) has kinda the opposite effect you might expect. At solar max, the sun's higher output <i>partially blocks and reduces</i> the background radiation from outside the solar system, so you actually get less exposure to that type. The trade-off is that you have a higher risk of CME events.<br /><br /><font color="yellow">What about a magnetic field encompasing the craft (like earths magnetic field)? Would that provide some shielding? </font><br /><br />It's been proposed. The leader in the field is a clever guy named Winglee. Myself, I prefer present tech over future tech, so I say go with the plastic water tanks. <div class="Discussion_UserSignature"> </div>

 

[alpha_taur1]

For a lunar base, lunar regolith would be pretty useful for shielding against Cosmic rays. I wouldn't worry about the highest energy Cosmic Rays up around 10^18 eV +. They can penetrate solid rock. Generally the higher the penetration, the less the damage to human tissue. Simple helium nuclei or alpha particles are the worst, being about 20 times more 'toxic' than gamma rays. Fortunately they can be stopped by a few layers of dead skin. Higher energy Helium nuclei from the sun are slightly more of a problem. <br /><br />From memory, around 93% of all CME radiation is high energy electrons, somewhat like beta particles.<br /><br />Another good shielding material is sodium/potassium eutectic, which can be used for heat storage for energy during the lunar 'night'.

 

[holmec]

Great info.<br />Given a system like this I have a questions.<br />Can you use the shielding water as drinking and cleaning water, or do you need to use filters, or you have to have your drinking water in a different storage tank? <br /><br /> <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[tap_sa]

<font color="yellow">"The best two materials for blocking both CBR (Cosmic Background Radiation) and CME stuff (Coronal Mass Ejection) are water and polyethylene."</font><br /><br />I had a vague memory that hydrogen is good to and with a bit of googling came up with this.<br /><br /><i>Optimum protective materials. The requirements for a high performance shield<br />material is to maximize the number of electrons per unit mass, maximize the nuclear<br />reaction cross section per unit mass, and minimize the production of secondary particles<br />[1,2]. Thus, the transmitted LET spectra of hydrogen shows almost universal attenuation<br />above a few keV/m resulting in good attenuation of biological effects independent of<br />biological model used. On the other hand, materials with less hydrogen content such as<br />water experience attenuation only above 20 keV/m [1]. The maximum performance is for<br />liquid hydrogen which we use to define the maximum performance limit of any material<br />as shown in Fig. 3. It is a challenge to materials research to develop materials<br />approaching these high performance levels.</i> <br /><br />Of course water and polyethylene are much easier to work with than LH2. If hydrogen content is the key then how about methane, CH4? Much easier to handle than hydrogen. Maybe the foam layers of Bigelow's inflatable walls could be soaked with it.<br /><br /><br />

 

[grooble]

I wonder if that firepaste would block any of that out

 

[nacnud]

Water is probably the easiest to use and it can be multi-functional, drinking water can be used as shielding, as can waste water. Fuel cells generate water which rather than being dumped can be used. Perhaps why water hasn't been used yet is the bulk of storing it but with the new inflatable designs this might not be a problem. <br /><br />I think that at least shielding the most commonly inhabited module with an internal water blanket made from polythene is a very interesting solution.<br />

 

[tap_sa]

No idea until the inventor reveals it's composition. Very interesting stuff, it should be tested with arc jet to see if it can withstand re-entry conditions.

 

[grooble]

If it can, what would it potentially mean?

 

[holmec]

I guess the main problem with water is getting it off the ground. Sending up hydrogen and oxygen to orbit then using them in a fuel cell might be the way to go. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>