Cancer Posted January 23, 2012 Report Share Posted January 23, 2012 Re: More space news! I think you're being somewhat pessimistic (although you may have access to better data than I do). At this point in its mission' date=' the alien equivalent of Kepler wouldn't have confirmed the existence of the Earth.[/quote'] Actually ... at this point, it could, if it was looking in the same way Kepler is, and we happen to be in its target field, and they happen to be spang on Earth's orbital plane. The only data that have been released by the Kepler team officially and in a comprehensive form are from the first four months, but at this point if there was a real Earth clone to be seen, they would have it now. Quote Link to comment Share on other sites More sharing options...
Christopher Posted January 23, 2012 Report Share Posted January 23, 2012 Re: More space news! And we can state that as a fact from half a dozen sample return missions? I wouldn't bet on it yet. They just recently formed the "two moons" theory and GRAIL in paticaular is out there to measure it's gravity field - wich could give us information about the presence of heavier materials, espcially on the "impact site". But overall it's mean desity is less than earth (3.3 g/m² vs 5.5 g/m²) and it's basically just earth crust placed in space. So it's doubtfull there will be anything but light materials - that we have on the earth, easier avalible. It's the economics of mining a particular asteroid and moving the output where it's useful. Because of the perceived low cost of extraction and the favourable energetics of getting there and back' date=' the asteroids look like our best target. Will we turn out to be wrong? See above.[/quote'] Cargo is way easier to transport into space than people. And what you save on that area (because of lower gravity) you propably have to pay to make machines and man survive and thrive in 0-G and Vacuum environment. Even such simple things as cooling can become a big problem in space (as contrary to popular believe, vacuum isn't cold). Quote Link to comment Share on other sites More sharing options...
megaplayboy Posted January 23, 2012 Report Share Posted January 23, 2012 Re: More space news! Or long lived. Or patient. Or better at setting long range goals. Trouble with trying to solve the Fermi paradox is the solution has to apply to every tech savvy species that might ever evolve. Interstellar colonization is either impossible or highly, highly improbable. But if it is highly improbable, that first species that hits the jackpot will be the 800 pound gorilla. For that reason, if no other species has done it, I think we should give it our best try. I agree...but as a long-term survival strategy, probably best to hedge our bets by fixing as much as possible down here, rather than betting it all on red, so to speak. We can do both. And fixing our problems here makes it easier to work together and assemble the resources necessary to undertake such a monumental project. Quote Link to comment Share on other sites More sharing options...
McCoy Posted January 23, 2012 Report Share Posted January 23, 2012 Re: More space news! There's a place for skepticism, and a place for planning. We have a theory, to this point well supported, about what mineral distributions are like on the Moon and in the asteroid belt. Now it's time to plan our future in space. That means working on our best understanding of what's out there, not acting out randomly on the basis that our theories might be wrong. Will they turn out to be wrong? Maybe. Who knows? Boy, will there be egg on our face if that happens! But there'll be a lot more, and justifiably so, if we go ahead and build Moonbase Alpha on the hope that mining the Moon will turn out to be practicable. Those are our choices? I was thinking more along the line of a couple dozen uncrewed missions, remote controlled prospector rovers, communications arrays at L-2 and either L-4 or L-5 to control rovers on the far side, and the option of an uncrewed automated sample return mission if the rovers find anything interesting. Quote Link to comment Share on other sites More sharing options...
Old Man Posted January 24, 2012 Report Share Posted January 24, 2012 Re: More space news! Actually ... at this point' date=' it could, if it was looking in the same way Kepler is, and we happen to be in its target field, and they happen to be spang on Earth's orbital plane. The only data that have been released by the Kepler team officially and in a comprehensive form are from the first four months, but at this point if there was a real Earth clone to be seen, they would have it now.[/quote'] That might be a useful research project--figure out which systems might have spotted us by now using a Kepler-like instrument. You know... just in case. Quote Link to comment Share on other sites More sharing options...
tkdguy Posted January 24, 2012 Author Report Share Posted January 24, 2012 Re: More space news! Strongest solar storm since 2005 hitting Earth Quote Link to comment Share on other sites More sharing options...
Gnaskar Posted January 24, 2012 Report Share Posted January 24, 2012 Re: More space news! And we can state that as a fact from half a dozen sample return missions? "It was raining on Mongo that morning." The sample return missions, not so much. Thermal, visual and radio scanning from lunar orbit, on the other hand, provides a fairly good idea. Mind you, we won't know for sure until GRAIL finishes it's mission in May. "within a kilometer of the surface" is easy to say when (afaik) most of them are already that size. The difficulty I was talking about was the huge distance from one "mining site" to the next. The moon has a 1.6 km/s gravity well to overcome, while few asteroids have more than 50 m/s gravity wells (meaning near-Earth asteroids are "closer" by the usual space standards, allowing the same launcher to move about 80% more payload to a NEA). And you can use a far cheaper railgun (and lighter) to move the resources back to earth. By the way, these aren't some small temporary mining sites we're talking about. A single small asteroid weighs on the order of a trillion tons. For comparison: Earth's total iron use in 2004 was about a billion tons. Cargo is way easier to transport into space than people. And what you save on that area (because of lower gravity) you propably have to pay to make machines and man survive and thrive in 0-G and Vacuum environment. Even such simple things as cooling can become a big problem in space (as contrary to popular believe' date=' vacuum isn't cold).[/quote'] Technically, what little mass there is in vacuum is cold. There just isn't enough mass there to transfer heat away from a ship faster than it is produced. Mining is complicated enough that no matter where you do it, you will probably need human supervision*. And the only real difference on the Life Support side between moon and asteroid is the gravity. Soviet testing on mice indicated that lunar gravity is not enough to prevent bone degeneration, so the indicators we have currently imply that there is no actual difference except that you can move more payload (be it robots or habitats) to the asteroids. * Or, at least, I hope so. Mining is one of those things that could get humans into space, a great way to open the frontier to the rest of us. I agree...but as a long-term survival strategy' date=' probably best to hedge our bets by fixing as much as possible down here, rather than betting it all on red, so to speak. We can do both. And fixing our problems here makes it easier to work together and assemble the resources necessary to undertake such a monumental project.[/quote'] I can handle rocket science. It is, when you break it down enough, just math. You can solve math. Solving world peace on the other hand is not so easy. But if you can come up with a political system that protects the freedoms of it's citizens (including minorities), and will save us from yet another oil war while keeping all extremists happy enough to disincentivize terrorism while simultaneously promoting growth and sustainability, then I'd happily stand beside you on the barricades. But until the social sciences get back to us on that one, we engineers have to stick to what we know. Those are our choices? I was thinking more along the line of a couple dozen uncrewed missions' date=' remote controlled prospector rovers, communications arrays at L-2 and either L-4 or L-5 to control rovers on the far side, and the option of an uncrewed automated sample return mission if the rovers find anything interesting.[/quote'] Why land the prospectors on the surface? Say three orbital satellites using triangulated radio scanning (from orbit you can only expect about 50 meters depth and maybe a 5 meter resolution, but that's all we're realistically interested in anyway). An orbital laser (or a probe launching device if you don't feel developing an orbital laser weapon is a useful side effect) can be used to force any interesting matter to eject ala LCROSS. Quote Link to comment Share on other sites More sharing options...
McCoy Posted January 24, 2012 Report Share Posted January 24, 2012 Re: More space news! Why land the prospectors on the surface? Say three orbital satellites using triangulated radio scanning (from orbit you can only expect about 50 meters depth and maybe a 5 meter resolution' date=' but that's all we're realistically interested in anyway). An orbital laser (or a probe launching device if you don't feel developing an orbital laser weapon is a useful side effect) can be used to force any interesting matter to eject ala LCROSS.[/quote'] 5 meter resolution? Sounds like a good preliminary study, but isn't that a little coarse for prospecting? Allows us to find all the gold nuggets larger than eight feet across? Quote Link to comment Share on other sites More sharing options...
Gnaskar Posted January 24, 2012 Report Share Posted January 24, 2012 Re: More space news! 5 meter resolution? Sounds like a good preliminary study' date=' but isn't that a little coarse for prospecting? Allows us to find all the gold nuggets larger than eight feet across?[/quote'] Say a gold micro asteroid crashed somewhere "recently" (in geological terms). It would deposit itself over a wider area as a dust or small pebbles. An area 5x5x5 meters with enough such pebbles and dust to be worth mining would have a slightly higher density than the surrounding regolith. To find out what type of heavy matter the area is rich with (most of them are valuable, but some are easier to extract), aim the laser/chuck a probe at it, and analyze the resulting dust cloud. EDIT: I've stolen this method from the excellent board game High Frontier, in which the three main prospecting methods are Laser, Probe and Rover. Quote Link to comment Share on other sites More sharing options...
Cancer Posted January 24, 2012 Report Share Posted January 24, 2012 Re: More space news! That might be a useful research project--figure out which systems might have spotted us by now using a Kepler-like instrument. You know... just in case. Not a hard problem. We are visible (via that method) to systems that within about 4.69 milliradians -- a bit more than a quarter of a degree -- of the Ecliptic. The Ecliptic is the great circle on the sky which is the projection of Earth's orbital plane onto the celestial sphere. Quote Link to comment Share on other sites More sharing options...
Old Man Posted January 24, 2012 Report Share Posted January 24, 2012 Re: More space news! The question then becomes, are the Kafers in that slice of sky? Or more realistically, has our Kepler found any candidate systems in it? Quote Link to comment Share on other sites More sharing options...
Cancer Posted January 24, 2012 Report Share Posted January 24, 2012 Re: More space news! The latter can be answered: definitively not. Kepler is staring at a field in Cygnus, well away from the Ecliptic. Quote Link to comment Share on other sites More sharing options...
megaplayboy Posted January 24, 2012 Report Share Posted January 24, 2012 Re: More space news! Are there any systems in the Galactic Habitable Zone that could spot us with a Kepler-type approach? Quote Link to comment Share on other sites More sharing options...
L. Marcus Posted January 24, 2012 Report Share Posted January 24, 2012 Re: More space news! The question then becomes' date=' are the Kafers in that slice of sky? Or more realistically, has our Kepler found any candidate systems in it?[/quote'] The latter can be answered: definitively not. Kepler is staring at a field in Cygnus' date=' well away from the Ecliptic.[/quote'] And the Kafers came from beyond Arcturus. Quote Link to comment Share on other sites More sharing options...
Cancer Posted January 24, 2012 Report Share Posted January 24, 2012 Re: More space news! Are there any systems in the Galactic Habitable Zone that could spot us with a Kepler-type approach? If you mean known systems ... I'd have to check. I don't think any known exoplanet systems are that close to the ecliptic, but I would have to go through the list to be sure. If you mean sort of an indefinite "ought such systems exist", then certainly yes. Quote Link to comment Share on other sites More sharing options...
McCoy Posted January 24, 2012 Report Share Posted January 24, 2012 Re: More space news! The latter can be answered: definitively not. Kepler is staring at a field in Cygnus' date=' well away from the Ecliptic.[/quote'] Interesting. IIRC that's pretty much 90 degrees from the disk of the galaxy? Most stars would be coreward (toward Sagittarius A*)? Cygnus is, um, more galactic North than any other direction? Guess they chose that direction for fewer background stars? Quote Link to comment Share on other sites More sharing options...
McCoy Posted January 24, 2012 Report Share Posted January 24, 2012 Re: More space news! Not a hard problem. We are visible (via that method) to systems that within about 4.69 milliradians -- a bit more than a quarter of a degree -- of the Ecliptic. The Ecliptic is the great circle on the sky which is the projection of Earth's orbital plane onto the celestial sphere. So assuming that works in reverse, we have to be within a quarter of a degree of Earth II's ecliptic for Kepler to see it, and assuming that exoplanet's orbital inclination is somewhat random* from our point of view, we have less than a 1 in 700 chance of seeing Earth II? *somewhat random: I assume exoplanet's orbits will tend to cluster near their primary's ecliptic, 90 degrees from the star's axis of rotation. What I don't know is if there is a preferred direction for the axis of a star's rotation. If stars' axes tend to line up more-or-less galactic north-south (as I believe our sun's does), then targeting Kepler toward Cygnus seems a strange decision. Quote Link to comment Share on other sites More sharing options...
Cancer Posted January 24, 2012 Report Share Posted January 24, 2012 Re: More space news! Interesting. IIRC that's pretty much 90 degrees from the disk of the galaxy? Most stars would be coreward (toward Sagittarius A*)? Cygnus is, um, more galactic North than any other direction? Guess they chose that direction for fewer background stars? Actually, they chose that direction for other reasons entirely. You need to stare continuously at the same place, ideally for as long as the mission runs. You can't do that to a location that's in the plane the ecliptic, because the Sun blunders through that part of the sky every year. So instead you stare at a place out of the plane of the ecliptic so the Sun (and Moon and planets) never get in the way. Now, you don't look at the ecliptic pole, because that is an "elegant solution" to the problem and there are already more space missions that spend a lot of time in that direction (and artfiicial spacecraft are annoyances that you'd like to avoid if you have the option). Also, the star density isn't large in that direction. Instead, you choose a place that is well out of the plane of the ecliptic (for reasons already discussed) close to the main plane of the Galaxy, so there's lots of stars in that direction well away from the orbital plane of the Moon too (for obvious reasons; the orbital plane of hte Moon is tilted about 5 degrees from the ecliptic) well away from the celestial poles, because all the nice spy satellites in polar or near-polar orbit go through that patch of sky once every f***ing orbit in the north celestial hemisphere, since this is an American space mission and the US has a bunch of ground telescopes in the north and not so many in the south, so you can get lots of groundbased support observations with cheap local facilities There's some other subtle criteria, but Cygnus is the spot that was chosen as Kepler's target field. McCoy 1 Quote Link to comment Share on other sites More sharing options...
RexMundi Posted January 25, 2012 Report Share Posted January 25, 2012 Re: More space news! When is our new Mars Dune Buggy supposed to crash into Mars? Anyone keeping track of this thing? ~Rex Quote Link to comment Share on other sites More sharing options...
Cancer Posted January 25, 2012 Report Share Posted January 25, 2012 Re: More space news! So assuming that works in reverse' date=' we have to be within a quarter of a degree of Earth II's ecliptic for Kepler to see it, and assuming that exoplanet's orbital inclination is somewhat random* from our point of view, we have less than a 1 in 700 chance of seeing Earth II?[/quote'] Yes. Which is why you choose to look at a big piece of sky with a high density of stars, so you can observe at least hundreds of thousands of them all at once, to beat back that factor of several hundred you can't deal with otherwise. *somewhat random: I assume exoplanet's orbits will tend to cluster near their primary's ecliptic, 90 degrees from the star's axis of rotation. What I don't know is if there is a preferred direction for the axis of a star's rotation. If stars' axes tend to line up more-or-less galactic north-south (as I believe our sun's does), then targeting Kepler toward Cygnus seems a strange decision. No, the Sun's rotation axis (which is pretty much the same as the ecliptic pole direction, but not exactly) is tipped by about 60 degrees with respect to the plane of the Galaxy. There's lots of statistics about how much stellar rotation axes are tipped with respect to the line of sight, but not nearly as much about how they are oriented in the plane of the sky. The exception to that is with visual binary stars (pairs of stars in mutual orbit, where you can observe each star individually, and measure their motions over time): with that data you can identify uniquely the orientation of the orbital plane of the two stars. And those ARE oriented randomly. Lucius 1 Quote Link to comment Share on other sites More sharing options...
McCoy Posted January 25, 2012 Report Share Posted January 25, 2012 Re: More space news! Instead, you choose a place that is close to the main plane of the Galaxy, so there's lots of stars in that direction No, the Sun's rotation axis (which is pretty much the same as the ecliptic pole direction, but not exactly) is tipped by about 60 degrees with respect to the plane of the Galaxy. There's lots of statistics about how much stellar rotation axes are tipped with respect to the line of sight, but not nearly as much about how they are oriented in the plane of the sky. The exception to that is with visual binary stars (pairs of stars in mutual orbit, where you can observe each star individually, and measure their motions over time): with that data you can identify uniquely the orientation of the orbital plane of the two stars. And those ARE oriented randomly. OK, those were the puzzle pieces I was missing! Thank you very much! Must spread the wealth before giving Cancer somewhat random rep! Quote Link to comment Share on other sites More sharing options...
SteveZilla Posted January 25, 2012 Report Share Posted January 25, 2012 Re: More space news! OK, those were the puzzle pieces I was missing! Thank you very much! Must spread the wealth before giving Cancer somewhat random rep! Got him for you. McCoy 1 Quote Link to comment Share on other sites More sharing options...
Christopher Posted January 25, 2012 Report Share Posted January 25, 2012 Re: More space news! The moon has a 1.6 km/s gravity well to overcome' date=' while few asteroids have more than 50 m/s gravity wells (meaning near-Earth asteroids are "closer" by the usual space standards, allowing the same launcher to move about 80% more payload to a NEA). And you can use a far cheaper railgun (and lighter) to move the resources back to earth.[/quote'] Don't asume anything like "Space borne laser" or "Railgun" is going to be built anytime soon. Simple political reasosn: If you can put it into Mars/Asteroid Orbit, you can put it into earth orbit. Any project/solution that could be reseonably weaponized is out of the question, just to prevent us from starting a space arms race. We rather keep our "Mutual Assured Destruction" with nuclear weapons. Mining is complicated enough that no matter where you do it' date=' you will probably need human supervision*. And the only real difference on the Life Support side between moon and asteroid is the gravity. Soviet testing on mice indicated that lunar gravity is not enough to prevent bone degeneration, so the indicators we have currently imply that there is no actual difference except that you can move more payload (be it robots or habitats) to the asteroids.[/quote'] I meant simpler things. A little gravity might slow bone deterioation. Having a "down" helps a lot when moving stuff (even if the pull is weak). Quote Link to comment Share on other sites More sharing options...
Cancer Posted January 25, 2012 Report Share Posted January 25, 2012 Re: More space news! When is our new Mars Dune Buggy supposed to crash into Mars? Anyone keeping track of this thing? ~Rex August of this year, IIRC. I am sort of living in dread that it will in fact crash and be lost. The landing scenario is almost out of Rube Goldberg. Quote Link to comment Share on other sites More sharing options...
McCoy Posted January 25, 2012 Report Share Posted January 25, 2012 Re: More space news! When is our new Mars Dune Buggy supposed to crash into Mars? Anyone keeping track of this thing? ~Rex Countdown clock on the mission web site. Little over 193 days as I write this. August of this year' date=' IIRC. I am sort of living in dread that it will in fact crash and be lost. The landing scenario is almost out of Rube Goldberg.[/quote'] What do you mean "almost?" Landing system Landing a large mass on Mars is a difficult challenge. The atmosphere is thick enough to prevent rockets being used to provide significant deceleration, as flying into the plume at supersonic speed is notoriously unstable.[96] Also, the atmosphere is too thin for parachutes and aerobraking alone to be effective.[96] Although some previous missions have used airbags to cushion the shock of landing, the MSL is too large for this to be an option. Curiosity will be set down on the Martian surface using a new high-precision entry, descent, and landing (EDL) system that will place it within a 20 km (12 mi) landing ellipse, in contrast to the 150 by 20 km (93 by 12 mi) landing ellipse of the landing systems used by the Mars Exploration Rovers.[97] For this, the MSL will employ a combination of several systems in a precise order, where the entry, descent and landing sequence will break down into four parts.[98][99] Guided entry: The rover is folded up within an aeroshell which protects it during the travel through space and during the atmospheric entry at Mars. Atmospheric entry is accomplished using a Phenolic Impregnated Carbon Ablator (PICA) heat shield. The 4.5 m (15 ft) diameter heat shield, which will be the largest heat shield ever flown in space,[100] reduces the velocity of the spacecraft by ablation against the Martian atmosphere, from the interplanetary transit velocity of 5.3 to 6 km/s (3.3 to 3.7 mi/s) down to approximately Mach-2, where parachute deployment is possible. Much of the reduction of the landing precision error is accomplished by an entry guidance algorithm, similar to that used by the astronauts returning to Earth in the Apollo space program. This guidance uses the lifting force experienced by the aeroshell to "fly out" any detected error in range and thereby arrive at the targeted landing site. In order for the aeroshell to have lift, its center of mass is offset from the axial centerline which results in an off-center trim angle in atmospheric flight, again similar to the Apollo Command Module. This is accomplished by a series of ejectable ballast masses. The lift vector is controlled by four sets of two Reaction Control System (RCS) thrusters that produce approximately 500 N of thrust per pair. This ability to change the pointing of the direction of lift allows the spacecraft to react to the ambient environment, and steer toward the landing zone. Prior to parachute deployment the entry vehicle must first eject the ballast mass such that the center of gravity offset is removed. Parachute will deploy at about 10 km (6.2 mi) altitude at about 470 m/s (1,500 ft/s).[97] Parachute descent: When the entry phase is complete and the capsule has slowed to Mach 2 and at about 10 km altitude, the heat shield will separate and fall away. The Mars Science Laboratory will then deploy a supersonic parachute,[97] as was done by previous landers such as Viking, Mars Pathfinder and the Mars Exploration Rovers. In March and April 2009, the parachute for the MSL was tested in the world's largest wind tunnel and passed flight-qualification testing.[101] The parachute has 80 suspension lines, is over 165 feet (50 meters) long, and is about 51 feet (16 meters) in diameter.[101] The parachute is capable of being deployed at Mach 2.2 and can generate up to 289 kN (65,000 pounds) of drag force in the Martian atmosphere.[101] A camera on the bottom of the rover will acquire about 5 frames per second (with resolution of 1600×1200 pixels) below 3.7 km during a period of about 2 minutes until the rover software confirms successful landing.[102] Powered descent: Following the parachute braking, at about 1.8 km altitude, still travelling at about 100 m/s, the rover and descent stage drop out of the aeroshell.[97] The descent stage is a platform above the rover with 8 variable thrust mono propellant hydrazine rocket thrusters on arms extending around this platform to slow the descent. Each rocket thruster, called a Mars Lander Engine (MLE),[103] produces 400 N (90 pounds) to 3100 N (700 pounds) of thrust and were derived from those used on the Viking landers.[104] Meanwhile, the rover will transform from its stowed flight configuration to a landing configuration while being lowered beneath the descent stage by the "sky crane" system. Sky crane: The sky crane system will lower the rover to a soft landing –wheels down– on the surface of Mars.[97] This consists of 3 bridles lowering the rover and an umbilical cable carrying electrical signals between the descent stage and rover. At roughly 7.5 m (25 ft) below the descent stage the sky crane system slows to a halt and the rover touches down. After the rover touches down it waits 2 seconds to confirm that it is on solid ground and fires several pyros (small explosive devices) activating cable cutters on the bridle and umbilical cords to free itself from the descent stage. The descent stage promptly flies away to a crash landing, and the rover gets ready to roam Mars. The planned sky crane powered descent landing system has never been used in actual missions before.[105] Aerobraking, parachutes, and rockets all have problems, so let's use all three? How on Mars did they not include a balloon? The "variable thrust mono propellant hydrazine rocket thrusters" sounds like they're steerable. Must be some pretty robust software to control that. Hope it goes well, but this is kind of the opposite of KISS. Quote Link to comment Share on other sites More sharing options...
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