Wjolcz Posted October 19, 2016 Share Posted October 19, 2016 How are they planning to deal with helium tanks on the reused stages? They are no good for reuse if they are faulty. Link to comment Share on other sites More sharing options...
Damien_The_Unbeliever Posted October 19, 2016 Share Posted October 19, 2016 3 hours ago, Veeltch said: How are they planning to deal with helium tanks on the reused stages? They are no good for reuse if they are faulty. Helium tank failure appears to be in second stage. None of these have been recovered or planned for reuse. Link to comment Share on other sites More sharing options...
DerekL1963 Posted October 19, 2016 Share Posted October 19, 2016 8 hours ago, Veeltch said: How are they planning to deal with helium tanks on the reused stages? They are no good for reuse if they are faulty. As Damien points out, the failed tanks are on the second stage. But if they were on the first stage, they'd handle it just like anyone else handles failed components - they'd simply go in and replace them. If their reflight plan doesn't include regular preventative maintenance and allow for occasional corrective maintenance, then they're in big trouble in the long run. That's long been my concern about SpaceX's whole scheme, that they've designed for maintenance and factored it in and that they can work their way through the infant mortality phase of the bathtub curve. (And determine when they reach the wearout phase and schedule a major refit or retire the vehicle as appropriate.) There's a lot of talk about how flown stages have "proven" their reliability in the same way aircraft and cars do... But aircraft and cars have decades of intensive engineering behind them to reach the point they are today. Rockets, not so much. Being able to re-fire a stage that's flown and been recovered once with minimal/no maintenance is great, but that says very little about ten, twenty, or a hundred flights down the road. Link to comment Share on other sites More sharing options...
sojourner Posted October 19, 2016 Share Posted October 19, 2016 2 hours ago, DerekL1963 said: they'd simply go in and replace them. I doubt that would be "simple". If it's an ongoing problem they'll have to redesign around it. Link to comment Share on other sites More sharing options...
todofwar Posted October 19, 2016 Share Posted October 19, 2016 3 hours ago, sojourner said: I doubt that would be "simple". If it's an ongoing problem they'll have to redesign around it. True, but the engines would be ok, which I understood to be the more expensive part. Link to comment Share on other sites More sharing options...
Wjolcz Posted October 21, 2016 Share Posted October 21, 2016 What will the launch of Mars Dragon look like? Since it's going to be launched on FH I would assume they are either going for a direct transfer or put it in a parking orbit first. Now a direct transfer injection will mean the middle core will be lost, right? If they would go for the parking orbit it would be easier to recover the middle core, but then there comes the question if the upper vacuum stage has enough dV to send the Dragon off to Mars. Link to comment Share on other sites More sharing options...
NeverEnoughFuel!! Posted October 21, 2016 Share Posted October 21, 2016 I know I'm at huge risk of being spat on in gallon amounts... but even if the rockets are perfect, what about radiation, low gravity, amount of supplies, little rocks who hit you at multiple speed of a bullet, psychological impact of empty black space for months... all that I'm trying to say is that WE are not built for space... the other day I saw an interview with some guy from NASA on Msn right after the famous video... at the reporter's question how realistic Musk is... guy laughed and the first thing out of his mouth was radiation... like "try to stand next to the broken reactor in Chernobyl for three months, and see what happens"... It would be nice to get there... but alive... Link to comment Share on other sites More sharing options...
Bill Phil Posted October 21, 2016 Share Posted October 21, 2016 (edited) 33 minutes ago, NeverEnoughFuel!! said: I know I'm at huge risk of being spat on in gallon amounts... but even if the rockets are perfect, what about radiation, low gravity, amount of supplies, little rocks who hit you at multiple speed of a bullet, psychological impact of empty black space for months... all that I'm trying to say is that WE are not built for space... the other day I saw an interview with some guy from NASA on Msn right after the famous video... at the reporter's question how realistic Musk is... guy laughed and the first thing out of his mouth was radiation... like "try to stand next to the broken reactor in Chernobyl for three months, and see what happens"... It would be nice to get there... but alive... We're not built for Canada, either. But people really live that far north. (most live in the very south of Canada, though) We're also not built for most of Earth, but we still live here. Radiation - Need shielding (which has mass, but can be solved) Low Gravity - Centrifuges (which entails mass, but also solve-able) Supplies - Easiest part, actually Micrometeoroids - Thick hull would help, but we've had to deal with it before, and it's not impossible to solve Psychological Impact - screen for psychological ability and resilience All of these save one are engineering problems, they're not demons. I agree that Musk is a little bit "out there," but really he's just being vocal about his ideas. Not much of a problem there. We live with radiation every day. Small amounts, of course, but they're still there. Chernobyl is much more dangerous than space is (not counting the high vacuum of space, of course), the comparison doesn't fit very well. Edited October 21, 2016 by Bill Phil Link to comment Share on other sites More sharing options...
Northstar1989 Posted October 22, 2016 Share Posted October 22, 2016 (edited) 6 hours ago, NeverEnoughFuel!! said: I know I'm at huge risk of being spat on in gallon amounts... but even if the rockets are perfect, what about radiation, low gravity, amount of supplies, little rocks who hit you at multiple speed of a bullet, psychological impact of empty black space for months... all that I'm trying to say is that WE are not built for space... the other day I saw an interview with some guy from NASA on Msn right after the famous video... at the reporter's question how realistic Musk is... guy laughed and the first thing out of his mouth was radiation... like "try to stand next to the broken reactor in Chernobyl for three months, and see what happens"... It would be nice to get there... but alive... (1) Cite your sources. I'm sure you did see somebody making a critique about space radiation (there are plenty of people, even at NASA who have overblown fears about it), but it would be helpful to everybody else if you linked to the video so people could draw their own conclusions about the validityof the criticism and qualifications of the person making it (just working at NASA doesn't nwcessarily make you knowledgeable about the risks of manned interplanetary travel- it's a large organization with lots of specialization of roles...) (2) Radiation is a drastically overblown fear. The dosage isn't comparable to standing next to the Chernobyl reactor at all. Though the sun emits huge amounts of radiation, it dissipates by the Inverse Square Law- so by the time it gets this far out in space it's actually not that concentrated. We have reliable data on radiation beyond Earth's magnetosphere from the Apollo program and interplanetary probes- it's really not that dangerous... The Apollo astronauts received about 1200 millirem over 10 days (for reference, the average adult receives around 620 millirem per year on Earth, and nuclear power plant workers can receive up to 5000 mrem per year without ill effect), and some of that was from passing through the Van Allen belts, where you receive up to 13,000 millirem per hour in some parts. Now, Musk's plan calls for a 90-120 day transfer, and it only has to pass through the Van Allen belts once. Beyond the Van Allen Belts, the Chandraayan-1 spacecraft showed us radiation exposure only averages 1.2 millirem per hour (note that this measurement was taken in 2008- a solar minimum). The lowest dose known to cause any ill health effects is 10,0000 millirem (a slight increase in cancer risk- about 1%- much less deadly than if you smoked), and it takes 100,000 millirem to cause acute radiation sickness. A 120 day journey to Mars would take 2880 hours, and thus during years of a solar minimum, like in 2008, would only equate to up to 3456 mrem of radiation exposure- less than the 7000 mrem received during a typical 6 month International Space Station stay. However, during a solar maximum radiation exposure in deep space can be close to three times as high, so about 10,050 mrem in 4 months is not unreasonable during a solar maximum. As can be seen, background radiation is NOT an immediate issue for a Mars journey- although it could slightly increase your risk of cancer. The main danger is actually from getting caught in a Solar Particle Event (aka. a "Solar Storm"). During one of these, exposures can reach over 1,000,000 mrem over the course of the event. A dose of 400k mrem will kill 50% of adult humans, so this is more than enough radiation to prove lethal without shielding... Fortunately, the radiation during an SPE is lower-energy than cosmic rays and thus easily absorbed (this actually makes them more dangerous if unprotected- most cosmic rays simply pass right through you due to their enormous energy levels, which is why your mrem levels end up being so comparatively low despite the huge number of cosmic rays). A 10 cm aluminum shield will block more than 98% of them, for instance- lowering the exposure from an SPE to a manageable 20k mrem or so... Water and plastic happen to make more mass-effective shields against solar flares than aluminum, according to some studies (one NASA article states polyethylene provides 50% better protection than aluminum, for instance)- and they don't produce problematic secondary radiation when bombarded by gamma rays like aluminum does, which can actually be more deadly than the gamma rays themselves... Lead and uranium are also useful radiation shields in an SPE- although they are heavier for the protection they provide, and still produce a lot of secondary radiation... So, the best solution is probably the one Robert Zubrin proposed long ago- to simply huddle in your pantry and use your water supply as a shield (even if you only brought it on the journey for this express purpose, water is still lighter than equivalent-thickness metal shielding, if far more bulky...) You don't need to shield the whole spacecraft- electronics can be rad hardened for far less mass than they can be shielded, unlike squishy humans- you only need to have a radiation barrier you can rotate between the crew and the Sun to create a "solar storm bunker" the crew can hide in when a SPE is imminent... In short, carry a bunch of extra water with you to Mars (preferably in a plastic or carbon fiber tank- aluminum, like I said, emits deadly secondary radiation of its own when bombarded by gamma rays) and use it as a mass-effective rad shield during SPE's. When you get to Mars, you can use it for life support and ISRU to reduce the need for local ice-mining for these purposes... The radiation issues with space travel are really only of immediate concern when it comes to solar storms. The rest of the time your radiation exposure should not pose a major health risk- only a slightly increased risk of cancer. Fortunately, Mars itself has enough atmosphere to provide a level of rad protection equal to 11-22 cm of aluminum (depending on altitude and weather). This is enough to protect against acute health effects from SOE's, but not enough for a permanent colony- where doses can accumulate for decades and chronic health effects will eventually emerge- but fortunately you have lots of soil available to bury your habitats. A few (4-5) meters of Martian rock and soil would probably provide enough protection to not have to worry much about adverse effects on fertility, pregnancy, or immune/skin health. If you skipped on burying your habitats, however, you would probably see a substantial increase in infections, skin sores/lesions, anemia, a high (10-20% lifelong incidence) risk of leukemia, reduced fertility, and birth defects emerge over a 15-20 year timeframe. These health effects wouldn't necessarily doom a Mars colony (early settlers if the Americas had it far worse- gaving to deal with disease, hostile natives, and starvation), but they would make it an extremely undesirable place to live- in turn making it difficult to attract new colonists. So burying habutats in the first year or two would be an extremely prudent measure... Regards, Northstar Edited October 22, 2016 by Northstar1989 Link to comment Share on other sites More sharing options...
kerbiloid Posted October 22, 2016 Share Posted October 22, 2016 Chernobyl now has a younger sibling: Fukushima. Link to comment Share on other sites More sharing options...
HebaruSan Posted October 22, 2016 Share Posted October 22, 2016 4 hours ago, Bill Phil said: Radiation - Need shielding (which has mass, but can be solved) Aren't they planning to orient the ship with the engines and fuel tanks facing the sun, or did I imagine that? I wonder if the captain will announce RCS burns over the public address system. Quote Low Gravity - Centrifuges (which entails mass, but also solve-able) Has SpaceX actually suggested they might try that? I thought the plans around the passenger compartment were still mostly unspecified (and so probably mostly incomplete). I hope the next big announcement includes more detail about the interiors. I'm very curious what they'll look like. Link to comment Share on other sites More sharing options...
Northstar1989 Posted October 22, 2016 Share Posted October 22, 2016 (edited) For those still worried about the radiation issue, I suggest looking up RXF1. It's a structural plastic that is both stronger and lighter than aerospace-grade aluminum, and due to its light elemental composition it emits very little secondary radiation- making it substantially better than aluminum not only on a mass-basis, but even a thickness basis as well! (That is, 1 cm if the stuff provides a better radiation shield than 1 cm of aluminum, in addition to being much lighter). Although it might not tolerate re-entry particularly well, there's no reason SpaceX couldn't build the interior structure out of the stuff. And it could certainly make for a useful and lightweight material for creating a bunker to shield the crew against solar storms (which you could bury in the middle of the food and water supplies for even better rad protection if you were smart...) The problem is, RFX1 is currently patented. So SpaceX would have to buy the rights to use it from the NASA researcher who developed it at God knows what cost... (this stuff is closely related to high-performance plastics used in helicopter armor, so the rights to use it probably won't come cheap...) Regards, Northstar Edited October 22, 2016 by Northstar1989 Link to comment Share on other sites More sharing options...
YNM Posted October 22, 2016 Share Posted October 22, 2016 (edited) 10 hours ago, NeverEnoughFuel!! said: ... guy laughed and the first thing out of his mouth was radiation... like "try to stand next to the broken reactor in Chernobyl for three months, and see what happens"... It would be nice to get there... but alive... Hmm... Pripyat is now practically a "tourist" destination. (Objection in 3... 2... ) that being said, MSN is pretty old for news source. upgrade that, mate ! Edited October 22, 2016 by YNM Link to comment Share on other sites More sharing options...
Bill Phil Posted October 22, 2016 Share Posted October 22, 2016 12 hours ago, HebaruSan said: Aren't they planning to orient the ship with the engines and fuel tanks facing the sun, or did I imagine that? I wonder if the captain will announce RCS burns over the public address system. Has SpaceX actually suggested they might try that? I thought the plans around the passenger compartment were still mostly unspecified (and so probably mostly incomplete). I hope the next big announcement includes more detail about the interiors. I'm very curious what they'll look like. I'm speaking about what can be done, not necessarily what SpaceX plans to do or what they will do. Link to comment Share on other sites More sharing options...
Bill Phil Posted October 22, 2016 Share Posted October 22, 2016 12 hours ago, kerbiloid said: Chernobyl now has a younger sibling: Fukushima. (off topic, but whatever) I don't recall Fukushima having a steam explosion... The two incidents are pretty much unrelated to each other. Link to comment Share on other sites More sharing options...
kerbiloid Posted October 22, 2016 Share Posted October 22, 2016 35 minutes ago, Bill Phil said: (off topic, but whatever) I don't recall Fukushima having a steam explosion... The two incidents are pretty much unrelated to each other. I mean fallout. Link to comment Share on other sites More sharing options...
magnemoe Posted October 22, 2016 Share Posted October 22, 2016 13 hours ago, YNM said: Hmm... Pripyat is now practically a "tourist" destination. (Objection in 3... 2... ) that being said, MSN is pretty old for news source. upgrade that, mate ! Chernobyl is an tourist destination. The towns around it who is taken over by nature is very interesting and its an historical site. Its places who is not safe but this is even more true on an mountain trip 5 hours ago, Bill Phil said: (off topic, but whatever) I don't recall Fukushima having a steam explosion... The two incidents are pretty much unrelated to each other. Fukushima had an hydrogen explosion because of super-heated steam, they waited too long before venting it, Fukushima is also an way smaller pollution source than Chernobyl. Note that the Apollo astronauts was still inside earth magnetosphere, it expend past Moon then its full moon. Link to comment Share on other sites More sharing options...
NeverEnoughFuel!! Posted October 23, 2016 Share Posted October 23, 2016 20 hours ago, Northstar1989 said: (1) Cite your sources. I'm sure you did see somebody making a critique about space radiation (there are plenty of people, even at NASA who have overblown fears about it), but it would be helpful to everybody else if you linked to the video so people could draw their own conclusions about the validityof the criticism and qualifications of the person making it (just working at NASA doesn't nwcessarily make you knowledgeable about the risks of manned interplanetary travel- it's a large organization with lots of specialization of roles...) (2) Radiation is a drastically overblown fear. The dosage isn't comparable to standing next to the Chernobyl reactor at all. Though the sun emits huge amounts of radiation, it dissipates by the Inverse Square Law- so by the time it gets this far out in space it's actually not that concentrated. We have reliable data on radiation beyond Earth's magnetosphere from the Apollo program and interplanetary probes- it's really not that dangerous... The Apollo astronauts received about 1200 millirem over 10 days (for reference, the average adult receives around 620 millirem per year on Earth, and nuclear power plant workers can receive up to 5000 mrem per year without ill effect), and some of that was from passing through the Van Allen belts, where you receive up to 13,000 millirem per hour in some parts. Now, Musk's plan calls for a 90-120 day transfer, and it only has to pass through the Van Allen belts once. Beyond the Van Allen Belts, the Chandraayan-1 spacecraft showed us radiation exposure only averages 1.2 millirem per hour (note that this measurement was taken in 2008- a solar minimum). The lowest dose known to cause any ill health effects is 10,0000 millirem (a slight increase in cancer risk- about 1%- much less deadly than if you smoked), and it takes 100,000 millirem to cause acute radiation sickness. A 120 day journey to Mars would take 2880 hours, and thus during years of a solar minimum, like in 2008, would only equate to up to 3456 mrem of radiation exposure- less than the 7000 mrem received during a typical 6 month International Space Station stay. However, during a solar maximum radiation exposure in deep space can be close to three times as high, so about 10,050 mrem in 4 months is not unreasonable during a solar maximum. As can be seen, background radiation is NOT an immediate issue for a Mars journey- although it could slightly increase your risk of cancer. The main danger is actually from getting caught in a Solar Particle Event (aka. a "Solar Storm"). During one of these, exposures can reach over 1,000,000 mrem over the course of the event. A dose of 400k mrem will kill 50% of adult humans, so this is more than enough radiation to prove lethal without shielding... Fortunately, the radiation during an SPE is lower-energy than cosmic rays and thus easily absorbed (this actually makes them more dangerous if unprotected- most cosmic rays simply pass right through you due to their enormous energy levels, which is why your mrem levels end up being so comparatively low despite the huge number of cosmic rays). A 10 cm aluminum shield will block more than 98% of them, for instance- lowering the exposure from an SPE to a manageable 20k mrem or so... Water and plastic happen to make more mass-effective shields against solar flares than aluminum, according to some studies (one NASA article states polyethylene provides 50% better protection than aluminum, for instance)- and they don't produce problematic secondary radiation when bombarded by gamma rays like aluminum does, which can actually be more deadly than the gamma rays themselves... Lead and uranium are also useful radiation shields in an SPE- although they are heavier for the protection they provide, and still produce a lot of secondary radiation... So, the best solution is probably the one Robert Zubrin proposed long ago- to simply huddle in your pantry and use your water supply as a shield (even if you only brought it on the journey for this express purpose, water is still lighter than equivalent-thickness metal shielding, if far more bulky...) You don't need to shield the whole spacecraft- electronics can be rad hardened for far less mass than they can be shielded, unlike squishy humans- you only need to have a radiation barrier you can rotate between the crew and the Sun to create a "solar storm bunker" the crew can hide in when a SPE is imminent... In short, carry a bunch of extra water with you to Mars (preferably in a plastic or carbon fiber tank- aluminum, like I said, emits deadly secondary radiation of its own when bombarded by gamma rays) and use it as a mass-effective rad shield during SPE's. When you get to Mars, you can use it for life support and ISRU to reduce the need for local ice-mining for these purposes... The radiation issues with space travel are really only of immediate concern when it comes to solar storms. The rest of the time your radiation exposure should not pose a major health risk- only a slightly increased risk of cancer. Fortunately, Mars itself has enough atmosphere to provide a level of rad protection equal to 11-22 cm of aluminum (depending on altitude and weather). This is enough to protect against acute health effects from SOE's, but not enough for a permanent colony- where doses can accumulate for decades and chronic health effects will eventually emerge- but fortunately you have lots of soil available to bury your habitats. A few (4-5) meters of Martian rock and soil would probably provide enough protection to not have to worry much about adverse effects on fertility, pregnancy, or immune/skin health. If you skipped on burying your habitats, however, you would probably see a substantial increase in infections, skin sores/lesions, anemia, a high (10-20% lifelong incidence) risk of leukemia, reduced fertility, and birth defects emerge over a 15-20 year timeframe. These health effects wouldn't necessarily doom a Mars colony (early settlers if the Americas had it far worse- gaving to deal with disease, hostile natives, and starvation), but they would make it an extremely undesirable place to live- in turn making it difficult to attract new colonists. So burying habutats in the first year or two would be an extremely prudent measure... Regards, Northstar Wow, real fan work... since I'm too lazy to type here are some pages, I couldn't find that Msn video but these pages should be enough: http://www.nasa.gov/feature/goddard/real-martians-how-to-protect-astronauts-from-space-radiation-on-mars http://www.smithsonianmag.com/science-nature/radiation-remains-problem-any-mission-mars-180959092/?no-ist https://www.nasa.gov/sites/default/files/files/1_NAC_HEO_SMD_Committee_Mars_Radiation_Intro_2015April7_Final_TAGGED.pdf Maybe it's just me, but thank you... no, thank you... I live in the Balkans, more precisely Bosnia, and I'm old enough to remember Chernobyl, who is btw about 1700 km far from here... I also remember a guy who was caught in the rain that day... tomorrow he didn't have a single hair on his head... freshly hatched chickens in the country died instantly in the moment the plant went boom...in the course of next six month my late mother (among thousands of others, but it was kept a secret) also had terrible health problems... all of that at 1700 km distance... I don't even want to know how bad Fukushima was... in this case "ignorance is bliss"... Disclaimer: I'm NOT trolling anybody or anything... I'm just trying to give some skepticism, and objectivity... I personally think Musk had bit more he can chew... same as that other guy... Mars One thing... Link to comment Share on other sites More sharing options...
tater Posted October 23, 2016 Share Posted October 23, 2016 There are 2 broad risk types, both entirely real, associated with a Mars mission. The first would be an acute exposure. This would be the result of a solar flare. It's at least time limited, but the possible exposures can be life threatening. The second, and entire sure risk is the one pictured on the chart above. Mostly isotropic cosmic radiation. As Mars has squat for a magnetic field, the solution there is just mass. Low doses were thought to be lifetime cumulative in the past, but it is my understanding that this is not necessarily the case. None the less, higher lifetime exposures are still associated with increased cancer risks. That's about the extent of it, it's a trade off for some increase in cancer risk vs going to, or living on Mars. Many people have happily taken greater risk for tobacco and twinkies, but the risk is still real. If kids become involved at some point, I imagine radiation will be more of an issue than for older folks. For ITS the concern would be the acute exposure issue, and making sure there is enough mass between the crew and radiation---in the case of flare it is not merely pointing the craft at the sun, such radiation spirals outwards, but it is certainly predictable, but it is also spread out, not just a 1/2 degree spot on the sky. Link to comment Share on other sites More sharing options...
Northstar1989 Posted October 23, 2016 Share Posted October 23, 2016 (edited) 6 hours ago, magnemoe said: Note that the Apollo astronauts was still inside earth magnetosphere, it expend past Moon then its full moon. Not to a degree that is relevant for this discussion. Beyond the Van Allen belts (which the Moon lies well outsude of) the Earth's magnetosphere may still be detectable, but it doesn't provides any protection against cosmis rays or SPE's. In fact, the astronauts on one Apollo mission very nearly missed being hit by an SPE a few days after they returned to Earth (Apollo had no protection from SPE's, so this would have killed the entire crew...) 4 hours ago, NeverEnoughFuel!! said: Wow, real fan work... since I'm too lazy to type here are some pages, I couldn't find that Msn video but these pages should be enough: http://www.nasa.gov/feature/goddard/real-martians-how-to-protect-astronauts-from-space-radiation-on-mars http://www.smithsonianmag.com/science-nature/radiation-remains-problem-any-mission-mars-180959092/?no-ist https://www.nasa.gov/sites/default/files/files/1_NAC_HEO_SMD_Committee_Mars_Radiation_Intro_2015April7_Final_TAGGED.pdf Maybe it's just me, but thank you... no, thank you... I live in the Balkans, more precisely Bosnia, and I'm old enough to remember Chernobyl, who is btw about 1700 km far from here... I also remember a guy who was caught in the rain that day... tomorrow he didn't have a single hair on his head... freshly hatched chickens in the country died instantly in the moment the plant went boom...in the course of next six month my late mother (among thousands of others, but it was kept a secret) also had terrible health problems... all of that at 1700 km distance... I don't even want to know how bad Fukushima was... in this case "ignorance is bliss"... Disclaimer: I'm NOT trolling anybody or anything... I'm just trying to give some skepticism, and objectivity... I personally think Musk had bit more he can chew... same as that other guy... Mars One thing... The radiation we're talking about here is nowhere near the scale that certainly unlucky people in diwnwind countries were exposed to after Chernobyl. It takes at least 50,000 mrem in a short timespab to cause radiation sickness- the doses astronauts/colonists would receive from cosmic radiation are chronic rather than acute and nowhere NEAR that scale... The cutoff NASA has officially established for the maximum "acceptable" dose for a Mars mission corresponds to a net 3% increase in lifetime cancer risk, which is frankly a ridiculously high bar to clear for something as dangerous as space travel... Even so, they are just barely shy of thinking they can accomplishing it with an aluminium spacecraft (which emits lots of secondary radiation) and a surface habitat that provides essentially no radiation protection of its own. If they used something like RFX1 plastic for rad shielding (stronger and lighter than aerospace-grade aluminum, and it provides better rad protection as it emits no secondary radiation- really some amazing stuff), and buried the habitst under a few feet of soil, they would have no problem meeting their goals... Also, I resent your accusation that my admittedly back-of-the-napkin math is merely "fan work" and somehow less credible than your gut feelings on the issue (which are unfortunately/sadly tainted by your personal experiences with loved ones suffering rad sickness- reducing your ability to objectively assess radiation risks). I am a trained scientist in real life, and quite capable of accurately assessing a wide variety of technical data from chemistry, biology (my field), and physics. Regards, Northstar Edited October 23, 2016 by Northstar1989 Link to comment Share on other sites More sharing options...
Northstar1989 Posted October 23, 2016 Share Posted October 23, 2016 (edited) 3 hours ago, tater said: There are 2 broad risk types, both entirely real, associated with a Mars mission. The first would be an acute exposure. This would be the result of a solar flare. It's at least time limited, but the possible exposures can be life threatening. The second, and entire sure risk is the one pictured on the chart above. Mostly isotropic cosmic radiation. As Mars has squat for a magnetic field, the solution there is just mass. Low doses were thought to be lifetime cumulative in the past, but it is my understanding that this is not necessarily the case. None the less, higher lifetime exposures are still associated with increased cancer risks. That's about the extent of it, it's a trade off for some increase in cancer risk vs going to, or living on Mars. Many people have happily taken greater risk for tobacco and twinkies, but the risk is still real. If kids become involved at some point, I imagine radiation will be more of an issue than for older folks. For ITS the concern would be the acute exposure issue, and making sure there is enough mass between the crew and radiation---in the case of flare it is not merely pointing the craft at the sun, such radiation spirals outwards, but it is certainly predictable, but it is also spread out, not just a 1/2 degree spot on the sky. Yeah, rad doses really aren't cumulative... A dose of 100,000 millirem over a year isn't nearly as dangerous as a dose of 100,000 millirem over an hour. Your body has some remarkable DNA repair mechanisms (I should know- one of my research specialties is Genetics), and it can fully recover from radiation damage given enough time. The danger of acute symptoms developing from chronic exposure is fairly low, provided your chronic dose can be kept low enough for the body to stay ahead of it... Acurlte exposure is in many ways better than chronic exposure when it comes to cancer-risk. When a cell experiences massive rad damage all at once, it won't try to repair the damage, it will commit apoptosis (programmed cellular suicide). This is actually the guiding principle behind radiation-therapy for cancer. If enough cells do this all at once, you can develop some acute symptoms like nausea and vomiting from a whole bunch of cells all dying at the same time (particularly those lining your gastrointestinal tract), but since those cells are DEAD they can't reproduce and don't pose a cancer risk. The health problems people sometimes experience after severe acute exposure are largely due to the depletion of bone marrow stem cells and bone-associated somatic cells (the stem cells themselves are actually highly-resistant to radiation, but if you kill off the cells that feed and support them, they will eventually starve...) due to intense radiation exposure. The loss of BMSC's, and other cells critical to bone-health like osteoblasts and osteocytes, leads to many bone, blood, and immune associated health problems. Fortunately, even a small number of surviving stem cells can eventually repopulate the BMSC niche (in fact, amplification of only a small number of BMSC's that reach the niche alive is the reason bone martow transplants work), so many of these problems may eventually dissipate as the BMSC population recovers (did I mention Stem Cell Biology is *another* one of my specialities? In fact, it's the one I have the most theoretical background in, as well as most substantial research accomplishments/contributions in...) Bone morphology, immune system, skin (another system with high sensutivity to radiation) and blood changes are mainly driven by the loss of marrow cells due to the death of capillaries (bone marrow stem cells, while directly resistant to radiation, aren't very tolerant of losing blood supply), and in nonlethal cases of radiation sickness, these losses are largely reversible. The most significant permanent (nonreversible) changes that are induced by sublethal rad exposure that I know of besides cancer (which will typically only manifest decades later) are an increased risk of cataracts, and cognitive decline (especially memory-loss and a heightened risk of certain mental illnesses)- both of which could admittedly prove quite detrimental to survival on Mars (blind, mentally-ill people with terrible memories *might* have a hard time surviving on an alien planet...) This is why I *REALLY * hope Musk goes and buys the patent on RFX1, and builds his spacecraft's internal structure out if it, if it's all it's cracked up to be... Regards, Northstar Edited October 23, 2016 by Northstar1989 Link to comment Share on other sites More sharing options...
Elthy Posted October 23, 2016 Share Posted October 23, 2016 In about 6 hours Elon Musk will do the AMA at the SpaceX subreddit. Im sure the questions will be better than at IAC, also i hope for good answers. Since SpaceX and Elon dont have any real competition on that plan they can propably give more detailed answers than usual, at least for the colony stuff. Link to comment Share on other sites More sharing options...
NeverEnoughFuel!! Posted October 23, 2016 Share Posted October 23, 2016 (edited) 13 hours ago, Northstar1989 said: Not to a degree that is relevant for this discussion. Beyond the Van Allen belts (which the Moon lies well outsude of) the Earth's magnetosphere may still be detectable, but it doesn't provides any protection against cosmis rays or SPE's. In fact, the astronauts on one Apollo mission very nearly missed being hit by an SPE a few days after they returned to Earth (Apollo had no protection from SPE's, so this would have killed the entire crew...) The radiation we're talking about here is nowhere near the scale that certainly unlucky people in diwnwind countries were exposed to after Chernobyl. It takes at least 50,000 mrem in a short timespab to cause radiation sickness- the doses astronauts/colonists would receive from cosmic radiation are chronic rather than acute and nowhere NEAR that scale... The cutoff NASA has officially established for the maximum "acceptable" dose for a Mars mission corresponds to a net 3% increase in lifetime cancer risk, which is frankly a ridiculously high bar to clear for something as dangerous as space travel... Even so, they are just barely shy of thinking they can accomplishing it with an aluminium spacecraft (which emits lots of secondary radiation) and a surface habitat that provides essentially no radiation protection of its own. If they used something like RFX1 plastic for rad shielding (stronger and lighter than aerospace-grade aluminum, and it provides better rad protection as it emits no secondary radiation- really some amazing stuff), and buried the habitst under a few feet of soil, they would have no problem meeting their goals... Also, I resent your accusation that my admittedly back-of-the-napkin math is merely "fan work" and somehow less credible than your gut feelings on the issue (which are unfortunately/sadly tainted by your personal experiences with loved ones suffering rad sickness- reducing your ability to objectively assess radiation risks). I am a trained scientist in real life, and quite capable of accurately assessing a wide variety of technical data from chemistry, biology (my field), and physics. Regards, Northstar So it's basically your expertise, (and many others who share your opinion), against Nasa's expertise? Sorry, but I choose NASA... my personal experience with Chernobyl was here just to illustrate danger of radiation...man, when I see that chart it's double of the amount of radiation we get here behind magnetic field shield. I don't doubt you are an scientist in real life, somebody without proper education couldn't write such thread, but you are biased to Musk's vision... I'm not, that's all. Should he coat ships in RFX1? Sure, if he can pay for it! In my humble opinion as a fan of science, KSP, and space travel in general he should coat them in a tank sandwich type armor made of gold/led/RFX1/water and whatever it takes, if he can launch it in orbit. Should he dig in habitats inside the mountain? Sure, if he can land robotic drillers there first, together with network of satellites to remotely control them! Again I think he bit more he can chew... we first need an infrastructure in orbit... a space dock for the beginning... his reusable rockets could help a lot there... space elevator would be even better. Also in my humble opinion he should hire those two guys from Skunkworks... Dr Harold “Sonny” White and the other one (I don't remember his name) and give them REAL proper lab and money... not a mediocre lab and a shoe lace budget... Again, in my humble opinion speed is the key here. And btw why does "scientific community" (whatever that means/is) delays publication of Emdrive peer reviewed paper for almost a year? Could it be because it's highly disruptive technology which renders all of the airplane's fleet's and airport's infrastructure's obsolete/useless in a very short time span? Like the famous comedian Russel Peters had said "somebody is going to be hurt really bad!" Sadly, all comes down to state, politics, and protection of "elite's" (bunch of crooks and thieves) interests and money... and we need much more than one Musk to get off this rock... On the other side of a coin, however noble his ideas and visions are, I'm going to be poisonously toxic here, and ask why he really want's to do this, boy's dream of being an astronaut? Maybe he want's Mars for himself, or at least good chunk of it's resources, whatever they are if there are any, and however ridiculously this sounded... call me whatever you like "conspiracy theorist/loon" etc. etc. ... This is a slight edit... for the sake of sarcastic sci-fi fun and stepping on romantic dreams of space travel... with taking into account a current state of world's economy and depletion of resources, maybe first massive crews on mars will not be rich tourists (we will find a much nicer place for them), but convicts sentenced to hard work in mines of rare metals and jewels... who cares about radiation protection... they are dead anyway... scary isn't it? True face of capitalism/modern bank/corporate slavery. Edited October 23, 2016 by NeverEnoughFuel!! Link to comment Share on other sites More sharing options...
tater Posted October 23, 2016 Share Posted October 23, 2016 NASA is not clueless, there are without question real risks, it's just a matter of where one draws the line. In the context of SpaceX (this being a SpaceX thread), it needs to be baselined to possible ITS mission profiles, which place the crew on the surface, even in early RT missions for substantial periods of time, and until construction equipment is brought, in habitats that are not buried. Using ITS as the hab is fine, but early missions (tiny crew) would probably want a storm cellar that protects from all directions, as once landed they cannot point the spacecraft they live in for protection. Missions with the insanely large 100 people crew are in a much different situation, frankly. This for large flare events with clearly dangerous radiation levels. Background levels might just be a chronic risk people face early on. Look at sea travel to the Americas. A huge % of Europeans that ended up in the Caribbean died to disease (look at the Leclerc Expedition to Haiti that Napoleon sent, they landed north of 30k troops, and over 15 thousand died of Yellow fever alone). Maybe people will put up with death rates that we would consider non-trivial now, that in the past would have in fact considered nothing at all to worry about. Link to comment Share on other sites More sharing options...
Gkirmathal Posted October 23, 2016 Share Posted October 23, 2016 @Northstar1989 Although off topic, a while back you were talking about a separate Mars LMO lander system. Might be someone is working on just such a design and system as we speak. Check out the following article: http://www.thespacereview.com/article/3085/1 Link to comment Share on other sites More sharing options...
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