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Forum:	Exploration: Moon to Mars
Topic:	NASA proposes 'gateway outpost' at L2

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Your Reply: HTML is ON UBB Code is ON Smilies Legend	[QUOTE]Originally posted by Blackarrow: [B]On reflection, I may be confusing the Lagrange points of the Sun-Earth relationship and the Lagrange points of the Earth-Moon system, in which case I suppose the Moon's gravity "tethers" a satellite orbiting higher than the Moon and the satellite flies a halo around the Earth-Moon system's L2 point, remaining roughly above the Moon's far side. Am I getting warmer?[/B][/QUOTE]
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<table border=0 cellpadding=0 cellspacing=0 width="600"><TR><td bgcolor="#000000"><TABLE BORDER=0 cellpadding=4 border=0 cellspacing=1 WIDTH="100%"><TR bgcolor="#660000"><TD COLSPAN=2><CENTER>T O P I C     R E V I E W</CENTER></TD></TR><TR bgcolor="#494949"><TD valign=top>Robert Pearlman</TD><TD>The Orlando Sentinel <A HREF="http://articles.orlandosentinel.com/2012-09-22/news/os-nasa-space-outpost-20120922_1_moon-rocks-space-launch-system-nasa-chief-charlie-bolden" TARGET=_blank>reports</A> that NASA officials have picked a leading candidate for the agency's next major mission: construction of a new outpost that would send astronauts farther from Earth than at any time in history. <BLOCKQUOTE>The so-called "gateway spacecraft" would hover in orbit on the far side of the moon, support a small astronaut crew and function as a staging area for future missions to the moon and Mars...Documents obtained by the Orlando Sentinel show that NASA wants to build a small outpost — likely with parts left over from the $100 billion International Space Station — at what's known as the Earth-Moon Lagrange Point 2, a spot about 38,000 miles from the moon and 277,000 miles from Earth.At that location, the combined gravities of the Earth and moon reach equilibrium, making it possible to "stick" an outpost there with minimal power required to keep it in place.To get there, NASA would use the massive rocket and space capsule that it is developing as a successor to the retired space shuttle. A first flight of that rocket is planned for 2017, and construction of the outpost would begin two years later, according to NASA planning documents.Potential missions include the study of nearby asteroids or dispatching robotic trips to the moon that would gather moon rocks and bring them back to astronauts at the outpost. The outpost also would lay the groundwork for more-ambitious trips to Mars' moons and even Mars itself, about 140 million miles away on average.Placing a "spacecraft at the Earth-Moon Lagrange point beyond the moon as a test area for human access to deep space is the best near-term option to develop required flight experience and mitigate risk," concluded the NASA report.</BLOCKQUOTE></TD></TR><TR bgcolor="#333333"><TD valign=top>GACspaceguy</TD><TD>I like it!!</TD></TR><TR bgcolor="#494949"><TD valign=top>nasamad</TD><TD>I would have thought L1 would be a more realistic target, wouldn't L2 require satellites in lunar orbit for communication?</TD></TR><TR bgcolor="#333333"><TD valign=top>SpaceAholic</TD><TD>That's one option... the other is placement of a single comms bird at either L4 or L5 for continuous coverage (satellites orbiting the moon for such a function would require a multiple constellation if full time coverage was needed). Downside to L4/L5 is gain and transmit power due to free space loss (remedied with larger antenna) and latency. </TD></TR><TR bgcolor="#494949"><TD valign=top>Fra Mauro</TD><TD>I like the concept but I will inject some realism here. Where is the funding? Also, isn't this funny how this idea comes out when both parties are doing their annual "We love space exploration" bit every fours years?</TD></TR><TR bgcolor="#333333"><TD valign=top>Robert Pearlman</TD><TD> <BLOCKQUOTE>quote:<HR>Originally posted by Fra Mauro: Where is the funding?<HR></BLOCKQUOTE> That's somewhat the purpose of NASA putting forth the proposal. <BLOCKQUOTE>The planning documents indicate the outpost is possible only with "modest increases" to the current budget — and that presumes none of the cost overruns that have characterized recent NASA projects. Indeed, the first construction flight in 2019 is labeled "unfunded" in briefing charts, as is a robotic "sample return" moon mission in 2022.One NASA supporter in Congress — U.S. Rep. Bill Posey, R-Rockledge — said he liked the idea. But he said it would require strong White House backing to convince Congress to finance it.NASA funding "always has been very precarious," Posey said. "And money is going to get tighter."</BLOCKQUOTE></TD></TR><TR bgcolor="#494949"><TD valign=top>Jay Chladek</TD><TD>The amount of work needed to put an outpost at L2 is indeed not that much different from putting relay satellites at the other Lagrange points. It is an interesting proposal as it would allow for deeper space research to be conducted without the pitfalls of being on the moon (i.e. dust contamination). And it makes use of hardware already potentially in place.The only problems I see is it would still involve "used" elements. Sure a space station in LEO doesn't necessarily get the same wear and tear as a mission on Mars. But, as we all know, things wear out. As I see it, to do this, any modules utilized would practically have to be gutted almost entirely during a refit to re-certify them for use on a new project that could last just as long and where a failure could be even more critical due to the distances from Earth.Another pitfall as I see it is it would take an increased support infrastructure to keep a station that far out resupplied. So while putting a station at L2 would only need a "modest increase" the support infrastructure would require more of an investment than that.Don't get me wrong, if NASA can succeed in getting a project green lighted, I am all for it. But they might be underselling just what is needed for it and we all know how Congress loves to underfund from day one and hate's budget overruns. So the work might end up cancelled after only a couple years of paper project studies and no hardware built.</TD></TR><TR bgcolor="#333333"><TD valign=top>SpaceAholic</TD><TD>A new generation of hoaxers will emerge who will claim the outpost doesn't exist because it cant be seen.</TD></TR><TR bgcolor="#494949"><TD valign=top>arjuna</TD><TD>I agree, and if only for that reason it's probably worth doing! </TD></TR><TR bgcolor="#333333"><TD valign=top>Robert Pearlman</TD><TD>NASA is serious about sending astronauts back to the moon's neighborhood and will likely unveil its ambitious plans soon now that President Barack Obama has been re-elected, SPACE.com <A HREF="http://www.space.com/18380-nasa-moon-missions-obama-election.html" TARGET=_blank>reports</A> experts as saying. <BLOCKQUOTE> The space agency has apparently been thinking about setting up a manned outpost beyond the moon's far side, both to establish a human presence in deep space and to build momentum toward a planned visit to an asteroid in 2025.The new plans have probably already been cleared with the Obama Administration but have been kept under wraps in case Republican candidate Mitt Romney won Tuesday night's (Nov. 6) presidential election, said space policy expert John Logsdon, a professor emeritus at George Washington University. "NASA has been evolving its thinking, and its latest charts have inserted a new element of cislunar/lunar gateway/Earth-moon L2 sort of stuff into the plan," Logsdon told SPACE.com. "They've been holding off announcing that until after the election."</BLOCKQUOTE></TD></TR><TR bgcolor="#494949"><TD valign=top>Rusty B</TD><TD>Found on the NASA Technical Reports Server: <BLOCKQUOTE><A HREF="http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120016760_2012017550.pdf" TARGET=_blank>Skylab II, Making a Deep Space Habitat from a Space Launch System Propellant Tank</A>, Jan 2012, PDF Size: 3.3 MB, Number of pages = 25. Updated/Added to NTRS: Dec 12, 2012.Abstract: Called a "House in Space," Skylab was an innovative program that used a converted Saturn V launch vehicle propellant tank as a space station habitat. It was launched in 1973 fully equipped with provisions for three separate missions of three astronauts each. The size and lift capability of the Saturn V enabled a large diameter habitat, solar telescope, multiple docking adaptor, and airlock to be placed on-orbit with a single launch. Today, the envisioned Space Launch System (SLS) offers similar size and lift capabilities that are ideally suited for a Skylab type mission. An envisioned Skylab II mission would employ the same propellant tank concept; however serve a different mission. In this case, the SLS upper stage hydrogen tank is used as a Deep Space Habitat (DSH) for NASA s planned missions to asteroids, Earth-Moon Lagrangian point and Mars.</BLOCKQUOTE></TD></TR><TR bgcolor="#333333"><TD valign=top>Blackarrow</TD><TD>In spite of doing some basic research, I just can't figure out how the L2 point works. Why would this be a stable point in space? If a satellite is in a higher solar orbit than the Earth, it ought to follow a slower path and, like Mars, take longer than 1 year to orbit the Sun. What is it about the proximity of the Earth that creates a stable point? Is the Earth's gravity "tethering" the satellite at L2, preventing it from drifting into a higher, slower orbit? And if that is roughly correct, what part (if any) does the Moon play in the stability of the L2 point? At first I thought a satellite at L2 remains hovering over a point on the far side of the Moon, but that can't be right, as the Moon orbits the Earth and must presumably be more than half-a-million miles away from the L2 point at what (for us on Earth) would be "new Moon." And if that is right, an outpost at L2 would only very briefly be close to the Moon once a month, and might never be "hidden" from view by the Moon, depending on the size of the halo the outpost would fly around the L2 point.There are diagrams available illustrating the gravitational forces which show that L2 (and L1 and L3) are in a line in the Sun-Earth relationship, which certainly suggests that the Moon's involvement is limited, but the diagrams don't actually explain WHY L2 is a stable point. This may simply be because my interest in science and space vastly outstrips my mathematical abilities! Is anyone willing to explain L2 in a few sentences?</TD></TR><TR bgcolor="#494949"><TD valign=top>Blackarrow</TD><TD>On reflection, I may be confusing the Lagrange points of the Sun-Earth relationship and the Lagrange points of the Earth-Moon system, in which case I suppose the Moon's gravity "tethers" a satellite orbiting higher than the Moon and the satellite flies a halo around the Earth-Moon system's L2 point, remaining roughly above the Moon's far side. Am I getting warmer?</TD></TR><TR bgcolor="#333333"><TD valign=top>Robert Pearlman</TD><TD>Maybe this will help: Phil Plait, the Bad Astronomer, explains the Lagrange points.<center><iframe width="400" height="300" src="http://www.youtube.com/embed/kD9qx6ZKc6k?rel=0" frameborder="0" allowfullscreen>

The European Space Agency also has a tutorial with animated illustrations. And Neil DeGrasse Tyson weighs in this 2002 article from Natural History magazine.

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