Northstar1989

I not only read, but submitted a couple questions on that AMA, and they were on entirely different topics, but not answered. Why? Because there were literally HUNDREDS of questioms asked there. The only vain thinking here is your assumption that just because he didn't select the questions YOU wanted him to answer, that means he didn't have an answer for them. Your argument holds no water. Speaking of which, using the crew's food and water as a radiation shield is one of the possible solutions that's been proposed before- by Robert Zubrin (obviously you'd need additional shielding beyond this, but it helps), and it's something NASA is considering. In fact there are literally dozens of possible solutions NASA is thinking about, and your lack of awareness of the optimism many NASA researchers hold about the subject does *not* constitute actually thinking there is no solution in site.. Your description of Musk, on the other hand, betrays an egotism that you really should work on. Saying a famous, intelligent, *highly* successful billionaire who started from nothing, immigrated to the USA, and built not one or two, but FOUR wildly successful companies (SpaceX, Tesla Motors, Solar City, and PayPal) and is famously humble in the way he deals with his own employees and interviews is an incompetent braggart who can't help but mouth off, shows that you are unable to keep your own braggadacio in check. I would strongly suggest you stop talking about your personal impressions of Musk and start talking about the topic of this thread (SpaceX), because baseless personal attacks on somebody so much more successful than yourself only make you look jealous.. Neil DeGrasse Tyson is famous for having an ego the size of a planet. He regularly says things that are wildly scientifically inaccurate, and yet there are no famous people who are safe from his critiques. He's more of a celebrity than a scientist, in the flavor of Dr. Oz, and I very much suggest you find a more credible source if you're looking to level a legitimate criticism against Elon Musk. Even Bill Nye would be far more credible- at least he's humble (in fact I've met the guy when I was a student- like myself he's a Cornell alumni, though much older- and he's quite a humble person)- and I hear he's a bit skeptical of Musk's plans as well... Also, Tyson didn't even *mention* Musk or SpaceX in the video you posted (wrong one, clearly). Finally, "fool.com", seriously? THAT'S what you consider a legitimate source? Not to mention, their article is impeccably dumb. They literally calculate the cost-per seat to Mars by taking the initial R&D cost for the ITS, multiplying it by a factor of 3 because they believe it's over-optimistic, and then just dividing it by the 100 seats on a single ITS launch. That's just stupid, stupid, stupid of them. It's as if they never even read anything of Musk's plan (which they probably didn't). For one, they're completely ignoring that each ITS gets re-used 11 times (for 12 total uses)- so they would have to divide by 1200 if they only assumed Musk built one ITS ever. But of course, that's not his plan- it's incredibly obvious Musk intends to build dozens and dozens of them, and banks are well aware of the difference betwern "sunk" and marginal costs- so even if Musk was firced to pay for R&D out of his personal fortune banks would have no issue lending hom money to build additional ITS's after the first launch proved it could reach Mars (and probably long before that). Additionally, there are all sorts of tax-credits and write-offs Musk can take advantage of to help pay for R&D. That's not even counting that NASA is likely to give him some more grants, like the Air Force already did for the Raptor engine, or that SpaceX is likely to start selling tickets for IRS launches years in advance. In the end, that article is deserving of the website's name- and only a fool would take it seriously. I mean no offense, but you *really* need to work on your criticisms if those are the best sources you can come up with (Tyson, yourself, and a website literally called "fool.com"). Regards, Northstar

This is *exactly* what I think Musk and NASA both need to be aiming for... It's a roughly 3% lifetime risk of developing cancer NASA deems unacceptable, which is stupid, because you already have around a 40% chance of developing cancer just by being alive... Of course, the most likely types of cancer from rad exposure are aggressive skin cancers, bone cancers, and leukemia- but even so none of those are necessarily a death-sentence. The astronauts would increase their risk of cancer a lot more just by taking up smoking... Ignoring certain earlier fear-mongering, this risk is due to rad from both cosmic rays AND solar storms, combined. And we're perfectly capable of building a heavily-shielded plastic (RFX1) solar storm-shelter into the middle of the craft or near the fuel tanks and engines, and surrounding it with your food and water supplies for extra protection. Building the rest of the spacecraft structure out of RFX1 would also provide some baseline protection against cosmic rays (aluminum is *terrible* for this because it emits a lot of secondary radiation, which is almost as dangerous as the cosmic rays it absorbed), and save weight anyways, as it is both stronger *and* lighter than aerospace-grade aluminum. Which not only means better rad protection, it also means much cheaper and lighter-weight construction with better safety-margins (the safety margins are what allow for cheaper construction- when you've overenginerred something and are not riding the absolute limit of what is physically possible, you don't need to be *nearly* as precise about the exact number of millimeters of thickness of structural elements...) Regards, Northstar Unfortunately, I think it's a 3% or 10% increase in risk in absolute terms (that is, 3% of all people developing cancer specifically due to rad exposure early enoygh in life for it to be a problem) NASA meant when they drew the 3% line-in-the-sand, not a 3% increase in risk. Either way, though, your baseline risk of developing cancer early enough for it to be noticed is around 40% anyways. And something of 80-90% of males are found to have prostate cancer when they die of violence or age-related ailments when advanced in age, even though it was never a problem because something else bumped them off first... I understand NASA's concern- astronauts getting cancer is bad PR- but I think it's wholly inappropriate when you're talking about the fate of the human race here... (like Musk, I don't believe mankind will survive long as a nuclear-armed single-planet species) Regards, Northstar

No, everything I said is fully supported by NASA and other organizations' research. I just happen to look at the data and draw the line somewhere different than NASA. NASA thinks a 3% lifetime risk of cancer is unacceptable, I say a 10% lifetime risk of cancer is acceptable when we're talking about colonizing another planet... It doesn't MATTER how that level of radiation exposure compares to typical Earth exposure- only if it leads to unacceptable health effects. A typical adult human will be exposed to 620 mrem of radiation a year. An Apollo astronaut was exposed to 1200 mrem in 10 days. An ISS astronaut is exposed to 7000 mrem over 6 months without ill health effects. A Mars colonist migh be exposed to 12000 mrem over a 6 month journey to Mars and that would still be OK. The victims of the Chernobyl disaster were exposed to MUCH higher doses in a much shorter period of time. It's not comparable. Regards, Northstar

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

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

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

(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

So, I've been playing a bit of the old 4X game Sid Meier's Alpha Centauri a lot lately (by the way, if you don't have it they sell it on Steam, and GOG.com has regular sales of it) and felt like discussing it with other Kerbalites... Hopefully it's within the subforum rules to discuss this old game here? Anyways, Alpha Centauri was a game and a work of science fiction far ahead of its time in many ways. It powerfully envisioned the future in such a compelling way I still find myself quoting it from time to time (and I don't usually quote games). Here is one of my favorite quotes from the game, for instance: "Human behavior is economic behavior. The particulars may vary, but competition for limited resources remains a constant. Need as well as greed have followed us to the stars, and the rewards of wealth still await those wise enough to recognize this deep thrumming of our common pulse." - CEO Nwabudike Morgan, "The Ethics of Greed" - There are many other interesting and thought-provoking quotes in this game on everything from how to fight a war, to the nature of liberty. For instance: "Beware of he who seeks to deny you access to information, for in his heart, he dreams himself your master." - Commissioner Pravin Lal, "U.N. Declaration of Rights" - I'lI have to post audio clips of the in-game readings of these quotes some time, because Alpha Centauri's voice acting is simply superb. Anyways, for now that should be enough to bring back a few memories and stimulate some discussion. Go forth and converse! Regards, Northstar

ULA is very much part of the defense industry, and for decades they've had exclusive control of the satellite launch industry as what basically amounts to an illegal trust between Lockheed Martin and Boeing (that the government refuses to enforce antitrust laws against, due to lobbying and political donations...) My parents both used to work for defense companies, and have all kinds of stories. Sabotage is a reasonably common occurrence in defense, and a constant fear (as is/was spying). Defense industries engage in dirty market practices, anticompetitive bidding, and hire swarms of lobbyists to skew the political process. You're incredibly naive if you think sabotage isn't a very real and serious concern here... Regards, Northstar

New Borman???

It's tricky, absolutely. But you have a much larger margin for error on a plane with low wing-loading (you can turn more sharply without ripping the wings off, as your angle of attack more closely follows your prograde vector), so the key to doing this effectively would be to develop a really *long* spaceplane that's basically a flying-wing (so you can have low wing loading but still have high wing-sweep). This also lends itself well to hypersonic deployment, since a plane with lower wing-loading flies higher at the same speed (and thus flies in lower dynamic pressure). I've always been a fan of designing planes to have really low wing-loading, but in this case it makes a lot of sense. Larger wings mean the plane masses more- so its stability is less likely to be adversely affected by the deployment of a given size rocket- and planes with lower wingloading have an easier time dolphining above their max cruising altitude and deploying their payload in a stall, yet still safely recovering afterwards (as lower wing-loading also means lower stall-speed). Finally, since the spaceplane would, at best, only be suborbital (if it even crossed the Karman Line at all), it wouldn't have to worry about hauling those huge wings all the way to orbit, or indeed spending much of the flight profile at all at altitudes where wings would only be deadweight. The rocket in the cargo bay, meanwhile, would reap all the benefits of a higher deployment (thus enabling use of more fuel-efficient engines) without having to worry about extra mass... Honestly, I think the biggest problems with Stratolaunch previously were that they deployed a small solid rocket at a comparatively low altitude and speed, and with a small payload. Solid rockets are best for use in the lower atmosphere due to their high exhaust pressure (which suffers less from ambient pressure) and actually detract from aerodynamic stability due to concentrating mass at the wrong end. Stratolaunch should have used a liquid rocket (probably KeroLOX as it is least cryogenic) for its higher ISP, which would have meant a lower wing-loading on the plane due to a lighter rocket. Launching at a low altitude and speed were a mistake, meanwhile, because they detracted from the benefits of an air-launch. If they were going through all the trouble of designing their rocket to launch from a plane, they shouldn't have utilized a modified commercial subsonic plane (I can see that they did this to try and save on R&D, but it ultimately limited them to a very small rocket, which still proved quite complicated and expensive to air-launch, but derived very little benefit from the modified commercial plane's comparatively low cruising speed/altitude). Instead they should have raised the capital to design their own plane, and made it BIG (so it could carry a larger rocket), with huge wings and engines/shape optimized for hypersonic flight at very high altitudes... Sure, it would have been much more expensive to design and build in the first place, but it was the only way they were ever going to get their ongoing costs low enough to turn a real profit vs. conventional launches... None of it may matter too much now, as SpaceX and the British Skylon project (a true, orbital spaceplane- which could just as easily be modified to fly a suborbital trajectory and leave circularization for the cargo in order to carry a heavier payload on each flight) have rendered StratoLaunch largely irrelevant anyways. But it's nice to dream about what *COULD* have happened if only they had been a little more daring and ambitious in their plans... Regards, Northstar

There's ANOTHER project planned after New Glenn??? What do we know about it so far? Regards, Northstar

If you dolphin, no amount of speed is an issue. What I'm suggesting is basically exactly what you suggested- speeding up to Mach 6-8 and then releasing out of the atmosphere. You can't exit the atmo ar Mach 6 through a steady climb- you have to dolphin higher than your sustainable cruise altitude to get there... It is expensive, but it can easily be 100% reusable if you can fly the plane back to the runway. So it's really not that expensive to build once you amortize out all the launches, and thanks to lift/drag and the use of airbreathing engines it's much more energy-efficient than using a rocket first stage to reach a similar release trajectory... That being said, the R&D costs would be astronomical. So it's one of those things that wouldn't really be economical unless we adopted Microwave Beamed Power for spacecraft propulsion (the most important benefit it provides is that it's a compact and lightweight way to provide massive amounts of electricity to spacecraft to run electric/ion engines, at power-levels normally only associated with chemical rockets...) or developed compact, lightweight fusion reactors qualified for spacecraft propulsion usage (the most promising such tech is open-cycle reactions that harness the energy of fusion directly to heat working mass, as they avoid the need to develop energy-positive fusion electrical generators...) Conceivably, you could use such tech to develop thermal turbojets that operate very well even at very high internal airspeeds- and thus generate usable thrust at much higher speeds and lower pressures than any existing jet engines... (Look up Project Pluto. What I'm talking is a nuclear ramjet- except a fusion one- which would produce far less thrust at sea level, but operate up to incredibly high airspeeds and low pressures due to the very high temperature of the heat source...) Regards, Northstar

After nearly 5 hours messing with drivers and install settings, I finally got 1.8 working and loaded up the server. A Creeper than proceeded to blow up the newbie signs/ town bulletin board before I could read them.

It's survival ^ Mine's Northstar1989, of course. Regards, Northstar

MK *AND* ZooNamedGames on one server?! I'll HAVE TO join! Regards, Northstar

Ummm, I wrote my posts on pieces yo avoid login timeout. Even so, I believe that part was there since the first iteration posted... Not 100% sure though. My memory's a little fuzzy today. Regards, Northstar

My thoughts exactly. Did you read my entire reply? I emphasize that these discussions are off-topic at the end and that I will not participate in any further discussion of such topics. Regards, Northstar

Long Smokestack Theory is the repeatedly disproved hypothesis that electric cars actually produce just as much or more pollution than gasoline cars, just with the pollution displaced to power plants. It ranks as basically somewhere between crackpot theory and oil industry misinformation/propaganda, and I will not waste time disproving it fir you wgen it's bern disproved over and over and over by experts in economics, ecology, and other related fields. There is no evidence to support it- it is jyst a theory some people *want* to be true, and so choose to believe despute all evidence to the contrary. Global Warming is also not up for debate. No credible scientists deny anthropogenic climate change. And debating it would violate forum rules on discussing politics... If you choose to deny global warming, then you are taking a stance based on belief rather than facts, and creating your own reality. In that case, there is no hope for ever convincing you of the truth of the matter anyways. That is all I will say about it. Skepticism is healthy, but the level of publicly-available information about these subjects is so high that choosing to deny the widely-accepted scientific facts on a gut feeling is no longer skepticism, it's living in an imaginary world where science has no validity and facts are relative. Facts are facts, and the mainstream is under no obligation to indulge every crackpot theory that denies those facts on flimsy evidence. It's quite appropriate, and indeed a good thing, for denying widely accepted facts based on gut feelings to be treated as heresy. It saves the public a lot of effort dealing with people who can never be convinced by any amount of evidence, and who disrupt having a serious conversation about how to deal with the world's problems. These discussions are off-topic anyways. While having a serious discussion about the costs and benefits of different forms of electricity generation or the environmental impact of electric car batteries has a place on this forum, and these are legitimate issues, this thread is not the place for any of them. Keep the discussion SpaceX related only, please (as you can see from earlier, I take a pretty wide view of what is relevant- but electric cars and climate change clearly are not.) Regards, Northstar

Not from LEO as a starting point it doesn't. It's exactly 6.46 km/s (not including the Delta-V to LEO, which you shouldn't be counting here). Your statement is either wildly inaccurate, or including a Delta-V gap (cost to reach LEO) which you absolutely should NOT be accounting fior in a discussion of how much Delta-V it takes to reach certain asteroids *from LEO* (which has been the clear context of my discussion- you have no right to deceptively reframe it to make the numbers look bigger). They're almost certainly including the Delta-V to get to orbit. Also, plane-changes are deceptive- because it's perfectly possible to use other planets and moons to provide a large component of a plane-change Delta-V with enough time and gravity-assists. For that matter, if you're clever about using gravity-assists off of Mars to raise your apoapsis relative to the Sun, and perform your plane-change when the Ascending or Descending Node is near Apoapsis, you can get out to those asteroids for a lot less Delta-V than that. Coming back, gravity-brakes and aerobraking help (actually, aerobraking *at* Mars helps when getting to the asteroid belt too, since this raises your periapsis relative to the Sun... And if your target inclination is far enough from the orbital plane, you're actually better off aerocapturing and gravity-braking off its moons into orbit at Jupiter first instead, and then using its complex moon-system to gravity-assist into a closer trajectory to your target orbit on the way back out...) All this would probably take many, many years though, which makes those asteroids very poor candidates for mining. But your even bringing them up is a disteaction and a straw-man, there is literally no reason to go to any of those asteroids when there are hundreds of smaller asteroids in easier-to-reach orbits... Regards, Northstar

Delta-V requirements in the tens of thousands? That clearly can't be accurate for any Near Earth Object- it takes less than that to get to Mars or Venus. And you as a KSP player ought to know that Delta-V requirements have nothing to do with the mass of the object (you just get less Delta-V for the same fuel, not a higher requirement). Regards, Northstar

The burden of proof is on the person making the claim. I didn't claim anything based on a specific price for Iridium, but rather on the previously-cited overall value of certain Near Earth Objects, it was *you* who claimed Iridium (which is not the only metal you'd get when trying to cut out Iridium rich rocks from an asteroid- Iridium is frequently found near Platinum, for instance) sells at $20,000/kg and thus needed to cite your source. Respectfully, that link does absolutely nothing to back up your point. In fact, it speaks at one point of naturally-occurring uncombined Iridium deposits- so it contradicts it. The low concentrations of iridium found in some meteorites are not necessarily the same as those found in asteroids. Iridium is in fact sometimes found as an uncombined element- which would clearly indicate much higher concentrations than 0.5 ppm can be found... To quote an article from Los Alamos National Laboratory: "Iridium occurs uncombined in nature with platinum and other members of this family in alluvial deposits." If Iridium is found uncombined, that would imply that, while its overall abundance may be extremely low, rock sections can be found containing nearly pure Iridium veins- although they would be incredibly rare (and thus, the whole plan hinges on being able to locate asteroids containing such high-purity Iridium deposits in the first place, as opposed to those containing Iridium impurities in other ores). *Those* high-purity Iridium ores are what you'd recover to Earth's surface without refining- not the entire asteroid. As for the heatshield, RCS, de-orbit system, those were clearly part of my 1:10-1:12 mass ratio estimate for the capsule as a whole. The unpressurized chamber holding the ore itself, stuffed with rocks, would have something like a 1:50 or 1:100 mass ratio. The rest of the mass is for engines, heatshielding, etc. Your criticism is once again baseless and invalid. I made no "basic mistakes", although your use of that language is condescending. Once again, I find your attitude to be rude and condescending, and your criticism very, very weak in its factual basis when there is any to speak of. I am offended by your behavior, and wish to respectfully inform you that I do not appreciate it. Regards, Northstar

Why couldn't you make it on-site? Mars has all the requisite elements (in fact, the Wikipedia article on Mars' Composition states that Alumimum and Calcium are two of the most common elements in the Martian crust), and the actual manufacturing process is rather simple/easy once you develop the carbon nanotubes (which are by and far the mist difgicult oart of the optical rectenna to make). I'm sure that a Mars colony could bootstrap its industry to start making these fairly soon after planetfall... (within 10-12 years) Regards, Northstar

Mars has quite a lot of Aluminum ore, actually. Aluminum, Magnesium, and (of course) Iron are all incredibly common on Mars... There are large beds of dry clay in some places (the primary elements in clay are Aluminum and Oxygen), and significant veins of Calcium Sulfate in these same suspected ancient seas and riverbeds. The spectroscopy data we have on the planet also shows high Al content. So it's quite reasonable to expect we'll be able to mine these minerals on Mars... Regards, Northstar

The problem with cryogenics in space is static electricity buildup... Anyways, on an entirely different note, if Musk can achieve $140k/ton to Mars, that would be $140/kg to the Martian surface! Even though I think that's still a bit too high for large-scale Mars colonization without government financial assistance, that would have to mean an even lower launch-cost to LEO, enough to potentially revolutionize our use of space... For instance anything under $300/kg to LEO should allow profitable mining of Iridium ore from Iridium-rich asteroids brought to Low Earth Orbit (a small probe with very high-ISP engines could bring in such an asteroid over the course of a few years). You wouldn't even have to refine the ore in orbit- at $300/kg to LEO and a sale price for Iridium of over $20,000/kg (or even higher for Rhodium) you could profitably just recover the raw ore with a reusable capsule. Assuming each kg of capsule mass allowed you to recover at least 10 kg of ore with an unpressurized, propulsively-landed capsule, then at $300/kg to LEO you could recover more than 640 kg of ore for each kg of Iridium obtained from refining it... This only scratches the tip of the iceberg, so to speak. With launch-costs that low, I'm sure there are a LOT of new uses of space that would become profitable... Regards, Northstar