4 ms·

> We should then boost the perigee up to at least 1,000km. This would expose the occupants to significantly more radiation, would it not? The Van Allen belts s

> We should then boost the perigee up to at least 1,000km. This would expose the occupants to significantly more radiation, would it not? The Van Allen belts start at ~650 km, varying with latitude and solar weather.

areoform 3y ago
You're absolutely right! The inner belt starts at, > The inner Van Allen Belt extends typically from an altitude of 0.2 to 2 Earth radii (L values of 1.2 to 3) or 1,000 km (620 mi) to 12,000 km (7,500 mi) above the Earth.[3][13] In certain cases, when solar activity is stronger or in geographical areas such as the South Atlantic Anomaly, the inner boundary may decline to roughly 200 km[14] above the Earth's surface. I found a graph that shows the dose rates at given altitudes for circular orbits, https://ars.els-cdn.com/content/image/3-s2.0-B9780128140581000035-gr005.gif https://ars.els-cdn.com/content/image/3-s2.0-B97801281405810... You quickly get into the centuries range as you approach a 800km perigee, see, https://www.researchgate.net/figure/Orbital-decay-of-the-spacecraft-in-LEO-vs-initial-orbital-altitude-with-respect-to-the_fig15_268373551 https://www.researchgate.net/figure/Orbital-decay-of-the-spa... With the ISS' large cross section, it will experience more drag, but (and this is a guess) the reboost time would be measured in years and decades rather than months somewhere between 750km to 800km. Maybe there's an altitude here that's safe and doesn't poison humans? I also found a report of shielding required for given equatorial circular orbits at different altitudes, https://space.nss.org/wp-content/uploads/Orbital-Space-Settlement-Radiation-Shielding-Globus.pdf https://space.nss.org/wp-content/uploads/Orbital-Space-Settl... > Table 4 suggests that for settlements in low equatorial orbit (below 500 km), no shielding mass is required to meet the 20 mSv/year and only a tiny (equivalent to polyethylene 0.01 ton/m2) amount to meet the 6.6 mGy/year limit. The ISS has an average of about the equivalent of 200 kg/m2 aluminum shielding [Cucinotta 2013]. Thus the minimal shielding provided by a pressure hull, solar arrays, whipple shield, etc. should be sufficient to meet the pregnant woman threshold. This has radical implications for space settlement as discussed below. > There is a very high radiation level (mGy/year column) with no shielding at 600 km. This is mostly trapped protons that can be easily shielded as is seen from the rapid dropoff when small amounts of shielding are added. Increased inclination (such as the ISS' orbit), means increased radiation exposure as they pass through the south atlantic anomaly.

areoform 3y ago

You're absolutely right! The inner belt starts at, > The inner Van Allen Belt extends typically from an altitude of 0.2 to 2 Earth radii (L values of 1.2 to 3) or 1,000 km (620 mi) to 12,000 km (7,500 mi) above the Earth.[3][13] In certain cases, when solar activity is stronger or in geographical areas such as the South Atlantic Anomaly, the inner boundary may decline to roughly 200 km[14] above the Earth's surface. I found a graph that shows the dose rates at given altitudes for circular orbits, https://ars.els-cdn.com/content/image/3-s2.0-B9780128140581000035-gr005.gif https://ars.els-cdn.com/content/image/3-s2.0-B97801281405810... You quickly get into the centuries range as you approach a 800km perigee, see, https://www.researchgate.net/figure/Orbital-decay-of-the-spacecraft-in-LEO-vs-initial-orbital-altitude-with-respect-to-the_fig15_268373551 https://www.researchgate.net/figure/Orbital-decay-of-the-spa... With the ISS' large cross section, it will experience more drag, but (and this is a guess) the reboost time would be measured in years and decades rather than months somewhere between 750km to 800km. Maybe there's an altitude here that's safe and doesn't poison humans? I also found a report of shielding required for given equatorial circular orbits at different altitudes, https://space.nss.org/wp-content/uploads/Orbital-Space-Settlement-Radiation-Shielding-Globus.pdf https://space.nss.org/wp-content/uploads/Orbital-Space-Settl... > Table 4 suggests that for settlements in low equatorial orbit (below 500 km), no shielding mass is required to meet the 20 mSv/year and only a tiny (equivalent to polyethylene 0.01 ton/m2) amount to meet the 6.6 mGy/year limit. The ISS has an average of about the equivalent of 200 kg/m2 aluminum shielding [Cucinotta 2013]. Thus the minimal shielding provided by a pressure hull, solar arrays, whipple shield, etc. should be sufficient to meet the pregnant woman threshold. This has radical implications for space settlement as discussed below. > There is a very high radiation level (mGy/year column) with no shielding at 600 km. This is mostly trapped protons that can be easily shielded as is seen from the rapid dropoff when small amounts of shielding are added. Increased inclination (such as the ISS' orbit), means increased radiation exposure as they pass through the south atlantic anomaly.