Here I am, on the road again. Can you guess where?
Enough  for now. I’m tired and off to bed!
 Great. I fix the picture and WordPress changes it right back!
 That’s a hint, y’all!
Here I am, on the road again. Can you guess where?
Enough  for now. I’m tired and off to bed!
 Great. I fix the picture and WordPress changes it right back!
 That’s a hint, y’all!
I was given a valuable reminder last week. I took part in my favorite science fiction convention  and had a great time as usual. But what wasn’t usual was the interaction that I had with the Guest of Honor. I’d only heard of him by hearsay  on another blog that I follow; his name had come up following some possibly ill-considered remarks of his about who won the Hugo  or, more specifically, why it was awarded. I was therefore prepared to see him as a sort of nerdy Kenye West.
Instead, he was one of the most gracious and consistently amusing people I’ve ever met . He listened to the opinions of others on the panels, unlike some authors I could name , and when he chimed in it was usually to add an illustrative anecdote. Even better (for my ego at least), he remembered me and would go out of his way to greet me in the halls whenever we passed. But best of all was when I went to the dealer’s room to buy a book. As I perused the various volumes by the author that were for sale, someone tapped me on the shoulder and said “No, don’t buy that one; this one is better”. You guessed it – it was the author! To top it off, he autographed both of the books I bought with quotes from Shakespeare. Now that is an author with class!
So the next time I’m tempted to play the “so-and-so doesn’t like him so he must be bad” game, remind me of FenCon, will you?
 And by “took part”, I mean that I was officially on two panels and unofficially dragged onto several more.
 Remarks about the value of hearsay would not be inappropriate here… [a]
 The Hugo is both the most and the least important award in science fiction. Named for Hugo Gernsback, who published the first science fiction magazine, it is voted on by the fans who attend the annual World Science Fiction Convention. It therefore reflects the views of those who care enough to go to the cons (the creme-de-la-fen, as it were) as opposed to those who publish and write science fiction (that would be the Nebula). You can spend many an entertaining hour arguing the relative merits of the two awards.
 You may now say “I told you so!
 One author earned himself a reputation at WorldCon by mansplaining how women should be glad that privacy is dead and upskirt photos are common.
[a] Which is why I’m not naming him; you should be allowed to meet him free of either my early dubiousity or later fanboyishness.
One of the frustrating tings about my job is that, in the oil and gas industry, companies change on a daily basis. Sometimes the changes are minor (e.g., a reshuffling of upper management ) and sometimes they are major (e.g., a merger ). Right now, my company is going through a medium-size change; it has just moved from one location in Houston to another. And that has caused me to go through a major change. I’m moving (again ).
Why would I voluntarily put myself through the pain and torment of moving? Money and time (but mostly money). In its old location, I could travel to my company in fifteen minutes and never had to get on the highway . In the new location which is located twelve miles from the old one, I have to either drive an extra hour and a half and pay no tolls or drive an extra forty-five minutes and pay $5 in tolls each way. If you add up the extra distance (20 miles @ $0.5/mile * 20 days/month = $200/month) and the extra tolls  ($10 per day * 20 days/month = $200), I’m paying $4,800 each year for the privilege of working in the new location .
And that’s why I’m moving. I can sell my house in Katy and make a nice profit on it (about 25%) and use most of that money to buy a new place and the rest to pay off a mortgage on one of my rental homes. I’ll end up with a new home that is closer to the office, which will save me that $400/month, and a lower mortgage payment, which will save me even more, and pay off a mortgage, which will – well, you get the picture. So, as is often the case, I’ll have to go through a little short-term pain (moving, selling the place, setting up the new one) in order to reap a long-term gain.
Just call it the story of my life…
 Which only matters if the upper management starts moving “downstream”; i.e., becoming less involved with oil and gas and more involved with making money. That inevitably signals a shift to a company that is less focused on finding hydrocarbons and more focused on making money. Strangely enough, once that happens, they inevitably make less money. Go figure.
 I fully expect a wave of mergers in the oil and gas industry sometime soon. If you look at the annual balance sheets (the “book value” of the company) and compare them to the stock capitalization (the “market value” of the company found by multiplying the number of shares by the price per share), you’ll see that most oil and gas companies are undervalued by 20-40%. Put another way, they are on sale for 40% off. A big company could snap up a little one for cheap and increase its assets at a lower cost than actually drilling for oil and gas.
 This will be my tenth move overall and my second since coming back to Houston.
 In Houston, this is a good thing. Though they aren’t as bad as Miami drivers, Houston drivers still exude a combination of machismo and idiocy that lends a certain piquant uncertainty to every trip.
 There ain’t no way I’m sitting in that traffic. I value my sanity and my time much more highly than that!
 For the record, Houston mass transit doesn’t go to the new location (unless you want to go downtown, swap buses and come back out) and my company doesn’t have van pools.
Before we look at the final scorecard for the four options, let’s do a quick review:
Rather than spending money on exploring space, we should invest in exploring Earth – specifically the “inner space” of the ocean. Doing so would open up large areas to development and use and allow many more people to take part than any space program could.
We should return to the Moon and establish a permanent base there, with the aim of developing resources such as the ice that we think is located at the poles and the helium-3 that we think is located everywhere else. Doing so would create a permanent manned presence in space and reduce the costs of further, future exploration.
We should skip the Moon and head directly to Mars where there are more and more known resources (e.g., water, oxygen, iron). Doing so would firmly establish us as an interplanetary species and would set the stage for later exploration of the rest of the Solar System.
We should skip the Moon and delay Mars in order to explore the asteroids. Doing so would provide us with a view of the primitive Solar System even while it provided the same resources that are available on the Moon at a lower cost in delta vee (but longer times) and would prepare us for longer missions (e.g., going to Mars).
In the course of the discussion with Hop David and others, it has become clear that one more metric need to be added to the scorecard: whether or not the mission can be done with the technology that we currently have and if not, how long do we expect the development to take . In order to judge that, we’ll need to look at the technology that is required to accomplish each mission based on what the proponents claim (e.g., what rockets are called for in Spudis’ lunar base proposal?) and see if it is off-the-shelf, in development, or notional. Interestingly, those plans which rely on notional technology may actually do more for our exploration that those that rely on off-the-shelf technology.
Below is the scorecard for the four options, along with a brief reminded of why each metric matters.
What do we learn?
As a scientist, this is the question that I find most compelling (but others may disagree). The point of exploration isn’t just to plant a flag; it is to discover something new. For example, Lewis and Clark were sent out to establish an American claim to the West, but they were also tasked with cataloging what they saw, from the animals to the geology to natural resources. And the HMS Beagle was sent out as a demonstration of British naval might but it was also intended to increase their knowledge of geology and biology. So how do our four options fare?
|Earth Now||Moon First||Mars Next||Asteroids Someday|
|This option would teach us much about the geology of the Earth and would help determine how we will reduce our effects on the oceans even while we increase our use of them. It would also provide new living space to many, many more people than could be accommodated under any of the other plans, simply due to the much lower costs of transportation.||This option would help us learn more about the formation of the Earth-Moon system and the development of the Solar System. It could also serve as a base for radio or visual telescopes , and provide a relatively safe place to experiment with new forms of technology.||This option would provide use with a second baseline on our understanding of how terrestrial planets form. It would also provide information on how planets gravitationally capture asteroids (Phobos and Deimos) and would allow us to study two asteroids up close and personal. Mars is also a much likelier place to find extraterrestrial life than either the Moon or an asteroid; the impact of such a finding would outweigh almost any other discovery ever made.||Where setting up bases on the Moon or Mars would teach us about the end-stage of planetary formation, going to the asteroids would tell us about the early stages. In effect, we’d be looking at the baby pictures of the Solar System. The asteroids provide selections of each stage in planetary formation from the primordial system to initial accretion to differentiation into planetsimals.|
What can we do next?
If the path we are on leads to a dead end , then it isn’t a good path for us. And if the path uses up so much of our resources, be they time, money, or brainpower, that we cannot accomplish anything else, then it isn’t a good path for us. But if the path opens up possibilities of doing other things faster or less expensively, then it is an excellent path – even if it seems a digression.
|Earth Now||Moon First||Mars Next||Asteroids Someday|
|This path leaves us on Earth with little improvement in our ability to go elsewhere. Though many of the life support technologies developed for deep ocean exploration can be used in space exploration, very little of the other work is so useful.||Placing a permanent base on the Moon would provide us with at least two way stations (one on the lunar surface and one at LEO or a libration point) that could be used for further exploration. And, if the presence of water on the lunar surface in economic quantities is proven (right now it is just very likely), then we could reduce our costs for chemical rocket fuel; instead of needing to bring up enough fuel to go to Mars from the Earth’s surface, we could rendezvous with a fuel depot in LEO and head for Mars from there. And, though the lunar regolith appears to be limited in the other elements that are necessary for building spacecraft, the elements that are there could be used for growing food and simple buildings.||Putting a permanent base on Mars would significantly extend our reach in the Solar System. The known presence of water and carbon dioxide, along with enough of an atmosphere to simplify extraction, make Mars a prime spot for developing a supply station. Indeed, some have suggested that Mars is so well suited for colonization that we should develop it first and then head back to the Moon. A station on Mars would serve as a way-station to the asteroid belt and open up that region for exploitation and exploration. In addition, if a more robust ion drive is developed as part of the Mars effort, then transportation times become significantly shorter.||Exploring the Near Earth Asteroids would allow us to test out the technologies that will be needed for missions to Mars and other places in the Solar System. In addition, sampling the various asteroids would allow us to develop materials extraction technologies (similar to those being developed on Earth) that would allow for the development of way stations throughout the Solar System.|
What does it prove?
An unstated (at least in public) but obvious part of the Apollo program was a demonstration of America’s ability to put one right between the eyes of the USSR; the program was a national security project as well as a national prestige project. So what will each option do for our security and our resources?
|Earth Now||Moon First||Mars Next||Asteroids Someday|
|This option would do the least to publicly promote US national security interests, but might have a large indirect effect. Because most of the results would be in areas that few people consider important , there wouldn’t be much interest outside of specialists.|| This would have a mixed effect on the public’s perception of US national security. For many, there would be a dismissal of a return to the Moon as “been there, done that”. Though a permanent manned base on the Moon could provide us with a steady supply of water for further space exploration and with a stronghold for national security ; the Moon could also be used as a very high security bacteriological
||Going to Mars would demonstrate that we still have the biggest and most accurate rockets (which was the point of the space race in the first place). It would also allow us to forestall any claim on the Red planet by another superpower. The known existence of water on Mars would provide a much-needed boost for deeper space exploration but wouldn’t help much in the Earth-Moon region.||Exploring the asteroids has the potential to be one of the largest disruptors of commerce, ever. Given the literally astronomical estimates placed on the mineral resources of some asteroids, bringing one back could cause the value of gold, silver, platinum, and other “precious metals” to drop precipitously even if the asteroid in question was “only” water rich. Given the impact that this could have on US commerce, being in control of the process would seem to be prudent.|
What does it cost?
Just as what the family invests in (new car, new home, new TV) depends on how much money they’ve got in the bank, which exploration path we take will have to be influenced by the cost. Though I won’t claim (as others have) that we cannot afford any of these exploration options , I will claim that we should explore in the most cost-effective manner possible (a goal that NASA hasn’t always managed ). And please note that the costs are all given in 2012 dollars in order to provide an apples-to-apples comparison and that only the costs to taxpayers are included; any private investments are considered to be “free” as they are factored into the investment. Costs will also be given in the equivalent of FY2012 annual NASA spending and FY2012 annual DoD spending.
|Earth Now||Moon First||Mars Next||Asteroids Someday|
|This is the least expensive option. A full-blown inner space exploration program could be had for just $3 billion per year. Over the course of a ten-year program, that’s a total cost of $30 billion.||Surprisingly, this could be one of the more expensive options. NASA’s Constellation program was expected to have a lifetime cost of $231 billion and even Spudis’ inexpensive alternative would run at least $93 billion. That is the equivalent of increasing NASA’s budget by 40% for the duration of the project.||Cost estimates for this range from wildly expensive ($911 billion – NASA’s 90 day plan) to surprisingly affordable ($91 billion – Zubrin). The range in costs are partly due to a range of scopes (e.g., the 90 day plan included a lunar base and Zubrin’s plan does not) and partly due to uncertainty over the cost of developing the necessary technology. NASA’s budget would need to be increased by 30% for Zubrin’s plan and doubled for the more ambitious one.||The cost estimates for this option are still rather unsettled. The Keck plan suggests that we could return a single asteroid to cislunar orbit for around $3 billion and accomplish it within ten years; other estimates place the costs closer to $20 billion (but accept the decadal time scale).|
| Time: Ten years
Money: $30 billion (1.8 NASAs, 0.05 DoDs)
| Time: Fifteen – thirty years
Money: $93 billion (5.4 NASAs, 0.14 DoDs) – $231 billion (13.4 NASAs, 0.35 DoDs)
| Time: Fifteen – thirty years
Money: $91 billion (5.3 NASAs, 0.14 DoDs) – $911 billion (53 NASAs, 1.4 DoDs)
| Time: Ten – fifteen years
Money: $3 billion (0.2 NASAs, 0.005 DoDs) – $30 billion (1.8 NASAs, 0.05 DoDs)
What does it need?
Finally, as noted above, “who bells the cat” is an essential question in exploration. If the path we choose can only be done with a supply of pure unobtanium, then we’ve chosen the wrong path. But if it merely requires us to use known technologies or to develop improved versions of what we already have, then it may be the best choice for us even if it isn’t the fastest or least expensive.
|Earth Now||Moon First||Mars Next||Asteroids Someday|
|For most ocean exploration, no new technology is required. We already have submersibles that an reach the bottom of the ocean and long-duration facilities that can open up the sea floor. If we want to mine the ocean or farm the ocean, then only modest improvements in current technology is needed. The only place where new technology would be required (and is already in development) would be for long-duration deep dives.||The Spudis plan assumed only modest changes in the current state of the art. By having most of the robotic activity done via teleoperation and by scaling back the landers to be more like Apollo than Constellation, the amount of new technology is kept to a minimum. The only untried technology that the plan assumes is a heavy launch vehicle that is currently on the drawing boards . The manned bases are only mostly untried; adapting a Sealab-style habitat could be done with minimal costs where developing a new habitat module specifically for the plan would increase the costs. Space suits will need to be improved to deal with caustic lunar dust and other hazards.||This plan includes the most untried elements. Simply landing on Mars would require the development of either a new vertical landing rocket suitable for use in atmosphere or an improved glider/shuttle style lander. In addition, long-term (1-3 year) free-fall habitats would need to be developed for the trip out and back, along with habitats for the martian surface (though those could be adapted from Sealab). In addition, where the Moon can be resupplied with food from Earth if necessary, the Mars mission will need to either take along enough food or develop ways of growing it en route. Similarly, fuel storage will be a large problem due to rapid changes in tank temperatures as they are exposed to and hidden from sunlight.More speculatively, development of an improved ion engine would significantly reduce travel times and increase the payload.||This plan falls somewhere between the Mars plans and the lunar base. It would require development of medium-term (6 mo – 1 year) free-fall habitats, along with testing of alternative mining methods.It is just barely possible to tote along enough supplies for an extended mission of this length, but development of methods to grow fresh food would make it easier.Development of autonomous vehicles would simplify the missions but leave us stuck on Earth.As with Mars, development of an improved ion engine would make everything easier.|
I hope that I have demonstrated that there is no single, obvious, best answer (no matter what the various partisans say). Each option has something to offer and each option has drawbacks. Going to the Moon is expensive but may give us a fuel depot. Going to Mars is even more expensive but may give us life (and a fuel depot). Going to the asteroids is inexpensive but requires longer trips. Going to the oceans is cheap but doesn’t help us get off of this rock.
Based solely on cost considerations, exploring the asteroids is the most viable choice. It is lower cost and can be launched faster than either a return to the Moon or exploring Mars. However, both the Moon and Mars plans have allies in Congress; the asteroid plan has very little support (and exploring the oceans has no support at all). As a result, the current wrangling over our direction in space is likely to continue.
What do I think?
The real problem isn’t that we don’t have good places to go (all of them qualify there) but that we have political leadership that changes the plan every four to eight years and that consistently under-funds the plan. The only reason that they have gotten away with this for so long is because they have been able to divide the space exploration community into factions: manned vs. robotic, Moon vs. Mars, HLV vs. EOR. Each group was promised something by one administration only to have it taken away by another (“You want more probes? Right after we finish the shuttle!” “You want to go to the Moon? Convince those Martians!”) and the only constituency that has been consistently served is the pork-barrel one .
If the universe were perfect and money were no object, my preference would be do to it all. Set up bases on the Moon. Colonize Mars. Explore the asteroids. Live in the oceans. Send probes to the places that we cannot go . That’s because doing any one of these things will inevitably make doing the other things easier. Unfortunately, money is an object as Congress keeps reminding us. The way things stand right now, we would be lucky to get funding to do any one of the things on the list, much less all of them. Which is why I suggest that we should cheat.
The only reason that we haven’t made more progress is because every time that Congress and the White House change NASA’s goal, NASA throws out everything that’s been done and starts over with a clean sheet of paper . However, much of the equipment that needs to be developed for a mission to the Moon is exactly the same equipment that would be needed on a trip to Mars or the asteroids. Both the Moon mission and the Mars mission and even the asteroid mission would benefit from a HLV, so we should keep developing one . Similarly, all three missions need long-duration facilities, so that should be developed in a consistent manner. Sure, when the White House says “OK, now we’re going to the Moon/Mars/Ceres/Oz” NASA should nod their (collective) head and say “Yes, boss”. Maybe they should even change the name of the systems (“OK, the rocket is now the ‘Ruby Slipper’ and the habitat is now ‘Emerald City’”). But what they shouldn’t do, even though they’ve been doing it for forty years now, is throw everything away. If we do that – if we use our brains and prove that we are not only better educated but actually smarter than the politicians that keep trying to set us against each other – then we’ll actually be able to make some progress and accomplish all of our goals. Maybe.
 I fully expect that latter question to be the most controversial, simply because it may indicate that some of our plans aren’t reasonable even if they are beautiful.
 However, some believe that the presence of a lunar atmosphere and possible electrostatically-charged dust may limit the utility of the Moon for either use. The atmosphere may be ionized just enough to interfere with signals, and the presence of dust is never good. In addition, the best places for the observatory are all on the far side of the Moon, far away from the planned bases.
 As the current path of doing nothing under the guise of doing everything does.
 E.g., food supply, rare-earth minerals. Despite a decade-long information campaign, many people don’t realize the poor state of fish stocks, nor do they understand the importance of China’s current strangle-hold on rare earth minerals. Much as was the case with oil in the 1980s, people only realize that other people control our supplies when the other people start limiting our supplies.
 Those wondering how you can use the Moon to support national security when the Outer Space Treaty specifically outlaws basing nuclear weapons in space are encouraged to read The Moon Is A Harsh Mistress (if you like your facts fictionalized for easy digestion) or the wikipedia (if you prefer them amalgamated).
 Indeed, I would argue that we cannot afford not to explore. Why? First and foremost, because exploration makes money for the United States. NASA inventions have paid back the cost of the space program several times over. Inventions like digital image processing (used in digital cameras and MRIs), the weather satellite, and communications satellites. The problem is that most NASA and NOAA and other exploration-related discoveries are so fundamental to our way of life that we never notice them. But think what travel would be like without the now-ubiquitous GPS or what television would be like without the use of relay satellites or what medicine would be like without the many sensors that space and ocean exploration have created and you’ll start to see why it is vital that we keep moving ever outward.
 Indeed, NASA is notorious for its inability to get the prices right. For example, the original five space shuttles were forecast to cost $5.15 billion and ended up costing $6.74 billion or 30% more than expected. The Apollo program was expected to run $7 billion and ended up costing $23.9 billion, or 241% more than expected. And perhaps the most egregious example is the James Webb Space Telescope started in 1993 as a $500 million telescope that would orbit by 2007; in 2013, the project is now expected to cost a total of $8,700 million (1640% overrun) and won’t launch for five more years.
 One of the more amusing things about the Spudis plan is that he consistently refers to Atlas IV and Delta V launch vehicles and rather pointedly leaves out the Space X Falcon 9 and Falcon 9 Heavy (which are less expensive than his preferred rockets but launched by a company that has a CEO who has publicly endorsed a plan to go to Mars). Nevertheless, the HLV is a hidden cost of the Spudis plan. If we rely on the SLS, then another $18 billion should be added to the cost. If instead it uses the Falcon 9 Heavy that is currently in testing and expected to launch at least two years before the SLS, then the added costs go away (as they are included in the launch costs).
 NASA upper management isn’t completely guilt-free in this, either. They have played the pork-barrel game themselves,trying to make programs so politically useful that they won’t be cancelled (e.g., the twelve different NASA centers that just happen to be in eight states with influential Congressmen, or the insistence on using more contractors for Constellation than were used for the Shuttle); this inevitably drives up costs and reduces safety.
 E.g., the moons of Jupiter. They are another place where life might hide in the Solar System, but the intense radiation belts around Jupiter mean that any human trip to the area is a death sentence.
 That’s part of why the return to the Moon was estimated twice what it cost to go there the first time. Instead of just starting with Saturn V and updating it, NASA decided to go with a brand-new design. The other part is because NASA didn’t use a completely clean sheet; the parts that were in politically-powerful areas (e.g., the solid booster rockets) became “mission essential”, warping the design to fit the politics instead of the physics.
 Unless, as seems likely to happen, a commercial variant becomes available. One of the lessons that NASA and Congress have yet to learn is that private enterprise can offer many things for much less than government contracts. NASA is finally getting out of the satellite launching game, after three decades of squashing private companies that horned in on “their” territory and to nobody’s surprise but NASA’s the private companies are doing a better job for less. If a commercial HLV becomes available, then NASA should immediately stop work on the SLS and simply use the commercial launcher.
The final destination I’d like to consider is the asteroids. But before we get into the wherefore and whyhow, we should spend a little time dispelling the most common myths about the asteroids, simply because those myths frequently distort the arguments.
Myth #1: All asteroids are located between Mars and Jupiter.
There are actually asteroids located in just about every region of the Solar System, from inside Mercury’s orbit to outside Pluto’s. Though asteroids are more plentiful between Mars and Jupiter, there are also significant families of asteroids that bounce between Earth and the Sun (the “inner Earth Objects”, at least 6), those with nearly circular orbits that cross the Earth’s orbit (the Apollos, at least 5,000), those with elliptical orbits that cross the Earth’s orbit (the Atens, at least 500), and those that cycle between the orbits of Earth and Mars (the Amors, at least 2600) . All told, there are more than 620,000 asteroids and 3200 comets  known to be in the Solar System.
Myth #2: All asteroids are big/small
Asteroids have a wide range of sizes, from as large as a planet (1 Ceres, 590 miles across) to as small as a grain of dust. Though most of them are very small, due to a combination of how they formed and how they collided, there are more than 10,000 known asteroids with a diameter of more than ½ mile . The trick is to find an asteroid that is big enough to be useful but not so big that it cannot be handled.
Myth #3: All asteroids are identical rocks.
To put it simply, asteroids are the leftovers of the Solar System. They are the pieces that either never got incorporated into a planet or got knocked apart during planet building. That’s why they come in such a wide range of sizes. And that’s why they come in such a wide range of compositions, as well. Some asteroids (the C-group) were just barely cooked; they fell together and generated just enough heat to form small inclusions (“chondrules”) but not enough to drive off the water. Based on the meteorites we’ve observed on Earth, C-class asteroids can be up to 22% water along with organic molecules and primitive rocks. Based on the spectral composition of asteroids, some 75% of them are C-group .
If you cook the asteroids a bit more, either by slamming them together at higher speeds or by making larger asteroids out of them or by bringing them in closer to the Sun, then the amount of water goes down and you are left with a stony or S-type. Because the process takes time and energy, only about 17% of asteroids are S-class.
If you make the asteroid large enough and hot enough, then it may differentiate and form an outer stony crust and an inner metallic core; current thinking has this happening within the first 100 million years of Solar System formation. If you then break those large asteroids apart through collisions, you’ll get E-type asteroids (named for the mineral enstatite in their rocks) and M-type asteroids (named for the metals that they hold); together, these represent about 5% of all asteroids.
Most of the remaining asteroids are P-type, which are believed to be rich in organic materials and various ices . The interesting thing about P-type asteroids is that their compositions are very similar to those of comets. In addition, there are groups of comets that are known to have very short periods (called, logically enough, “short period comets“). One famous set of 470 known comets has a maximum distance from the Sun near the orbit of Jupiter and are known as the “Jupiter comets“. And then there are minor planets that have characteristics of both comets and asteroids, such as the Centaurs.
The point here isn’t to confuse you with a barrage of technical terms, but merely to point out that asteroids have a wide variety of compositions, ranging from pure metal to nearly pure ice, and to remind you that nature rarely puts hard boundaries on categories so that dismissing something as “an asteroid” or “a comet” does the science a disservice.
Myth #4: Asteroids stay in one place or one orbit.
Something that frequently gets lost on those not in the planet-building biz is that orbits are dynamic things. As the various chunks of stuff wing through the Solar System, they interact with each other. Sometimes, the interaction is subtle, as in the 8:13 orbital resonance between Venus and Earth . And sometimes, the interaction is pretty obvious, as in the time that Jupiter tore apart a comet and ate it. Orbital resonances are common in the Solar System and play an important part in how it has changed over time. Currently, most planetologists think that an orbital resonance between Jupiter and Saturn in the early stages of formation was responsible both for their migration to their current locations and for the Late Heavy Bombardment that gave the Moon its pock-marked puss.
And they help change asteroid orbits. As a simple example, consider an asteroid in the main belt that is jiggled outward by getting too close to another asteroid. Soon enough, it falls into one of the gaps in the belt caused by orbital resonance with Jupiter. Every time that Jupiter gets near the asteroid, its gravitational pull tugs on the little rock, distorting the orbit more and more until it finally is thrown farther out or forced inward. And it isn’t just Jupiter that causes this sort of interaction; those asteroids that come close enough to Earth may find their orbit perturbed in weird and wonderful ways. Indeed, orbital resonance is one of the reasons that Earth typically has a temporary, small, second Moon drawn from the asteroids that pass near it. So, though the asteroids may have been in the Solar System since it formed, they haven’t been where they are for all that time.
Myth #5: Asteroids are hard to get to
This is one of the more persistent myths about asteroids. Unlike the other myths, there is a tiny shred of fact buried deep in it. You see, many asteroids are both easy and difficult to get to. In terms of the amount of delta vee required to get to an asteroid, there are at least 10 known asteroids that require less than 4 km/s, along with 461 more that need between 4 and 5 km/s, and another 1,804 that would require a delta vee between 5 and 6 km/s. All told, there are some 2,275 asteroids that are known to require less energy to get to than the Moon.
But, as we saw when discussing the Moon, energy is only half of the problem; the other half is time. It takes just three days to get from LEO to the Moon. If you want to get to the lunar poles, it will take a little longer (how much longer depends on how much energy you want to spend). Getting to an asteroid takes much longer. Unless the asteroid is one of Earth’s temporary moons (and we can’t really plan a mission based on a temporary phenomenon), the travel time is likely to be between three and six months for a Near Earth Asteroid . Traveling to an asteroid in the Main belt could take anywhere from six months to several years. If we restrict ourselves to a round trip that lasts less than a year, has a delta vee of less than 6 km/s, and includes a stay at the asteroid of at least a week, then there are 79 different known places we could go. If we want a trip that lasts less than six months with a delta vee of less than 6 km/s and a stay of more than a week, then it drops to just fifteen different known asteroids . (NB: These numbers are based on the assumption that we want a human to actually go out to the asteroid. If we instead decide to send a DAWN-type probe, then the travel time problem becomes much less onerous.)
Myth #6: Asteroid have no (usable) water
There are two roots to this myth. The first is the misperception that asteroids are mostly stony or iron instead of being largely carbon- and volatile-rich; fortunately, the spectra that we’ve recorded provide some pretty strong proof that a typical asteroid should have (or have had) water. The second is the belief that water ice is incredibly unstable under typical asteroid conditions and will quickly sublimate away. There is some science behind that statement, but it doesn’t bear up to scrutiny.
We need to start with the idea of the “snow line” or “frost line”; it is the innermost location at which hydrogen-rich compounds would have condensed into ices during the formation of the Solar System. Most experts put the snow line at about 3.5 AU , which is well beyond where most asteroids now live. So if the asteroids formed in their current location, then they couldn’t have a lot of water because the combined heat from the Sun and from collisional accretion would have driven it off. However, the current view which is based on observations of “hot jupiters” that have been seen around other stars is that the asteroids didn’t form in situ but were pushed into their current location by the inward migration of Jupiter and the other planets, though the exact amount of inward movement is (to put it mildly) a topic of some debate. As evidence of this, there is the example of asteroid 24 Themis, which has an orbit stretching from 2.7 AU to 3.6 AU and is known to contain water ice, along with that of 1 Ceres, which has an orbit going from 2.5 AU to 3.0 AU and a thick layer of water ice. Given that they couldn’t have formed where they are and have ice, they must have formed farther out and moved into place.
And it is that movement that matters now. It is indisputably true that as an asteroid moves closer to the Sun, it gets hotter. We can even use the black body temperature equation calculate how warm it should be , or, more correctly, how hot the surface of the asteroid should be. But an asteroid isn’t all surface and doesn’t heat all the way through instantaneously. If you’ve ever walked into a cave or used a heat pump then you know why: there is a thermal lag between the temperature at the surface and that in the interior. In general, it takes about three months for a temperature change to make its way from the surface of an asteroid to a point one meter deep and the amount of the temperature change is just ~1/3rd that of the temperature change at the surface. So if you were to move a ten-meter asteroid from 4 AU to 2 AU, its surface temperature would increase from 130 K to 194 K. If you left the asteroid there for three months, then the surface would still be 194 K and the temperature would quickly drop to 154 K a meter in and 138 K two meters in and remain at 130 K in the center. If you then moved the asteroid back out to 4 AU (as orbits are wont to do) and left it there for three months, then the surface temperature would be 132 K (the extra is from the interior heat flow) and the temperature would rise to 136 K one meter in and drop back down to 132 K two meters in and remain at 130 K in the center. Because the asteroid would spend more time at the farther end of the orbit, the average temperature would end up being closer to that at the far end than that at the near.
In addition to creating thermal lag, the blanket of soil would also act to reduce the sublimation rate because it would have lower permeability than open space (i.e., it would slow down the escape of any sublimated gasses) along with a higher tortuosity (i.e., the escape paths would be longer, which again decreases the rate of loss).Some experts think that just s thin blanket of loose soil could reduce the loss of water by a factor of ten to twenty. But is that enough? Well, given that one expert has found that a 1 km sphere of pure water ice would last 3,000 years at 1 AU and 3,000,000,000,000 years at 3.5 AU before the effects of thermal lag, permeability, and tortuosity are taken into account, the answer appears to be yes.
Of course, even if all of the water ice is gone, there will be plenty of water left in the form of hydrous minerals, such as gypsum and kaolinite. This is especially true of the asteroids that stay entirely within the Earth’s orbit. Will this bound water be no better than the water trapped in concrete? No. Simply grinding and heating gypsum to 425 K will extract ¾ of the water locked up in the mineral (this is how they make sheet rock). Similar methods work on other hydrous minerals. So, even if there is no water ice, there will be plenty of water on most asteroids.
Myth #7: Mining on an asteroid will be just like mining on Earth or on the Moon
One of the more interesting things that they teach in business school is that the first company to jump into a new technology almost always goes broke. Why? Because, instead of adapting their work to the new technology, they adapt the technology to their work. For example, when electric motors began to take over for steam engines and water mills as a power source in factories, the factory owners would usually buy one electric motor and place it at the end of a long belt that it would run; when workers needed power, they would link to the belt. It was done that way because that was the most efficient way to do it for a water wheel. But electric motors allowed each tool to have its own power source instead of working off of a common one; using it like a steam engine lowered the efficiency of the factory and made many of them go broke. When they began to use tools that were individually powered, the factory’s efficiency went up and the costs went down.
The moral of the story is that mining on the Moon will be different than mining on Earth. And mining on an asteroid will be different from either mining on the Moon or mining on Earth. For example, electromagnetism to separate ores is used on Earth but not extensively because the magnet has to fight gravity and only finds the highest iron content ores. On an asteroid, finding the iron ores may be as simple as running a magnet over the surface. Similarly, one could use a mass spectrometer to separate elements from an asteroid; the same could be done on the Moon but only much less effectively.
But the biggest difference may be how the ores are collected for processing. On Earth, it is generally not cost-effective to carry ores very far for processing ; it is likely that the same will hold true on the Moon. For example, the Spudis plan for mining the Moon requires 16 robotic missions to bring all of the gear simply because there are limits to how much one lander can carry. But because many asteroids require less delta vee to go to than the Moon and because you don’t land on an asteroid so much as co-orbit, that limitation is no longer in force; what takes 16 missions on the Moon can be accomplished with one mission to an asteroid – everything can be assembled in LEO  and then launched to an appropriate asteroid in one large package .
Or, if we’d rather not expose astronauts to the tedium and dangers (and dangerous tedium) of a long voyage, we can bring the asteroid to Earth for processing. Though logic would place the asteroid in LEO for ease of access, NASA has proposed a plan that puts it into cislunar orbit as a way of giving Orion something to go to . Placing a twenty meter C- class or S-group asteroid into LEO would pose no risk to Earth as it would break up in the atmosphere in an event like the recent one in Russia . We could send out a robotic tug that would either capture the asteroid in a giant air bag or lasso it or use the tug’s gravity to slowly shift the asteroid’s orbit. The good thing about sending robots is that it would be less expensive and easier than sending people; the bad thing is that we’d have to either work with an abominable time lag (due to the amount of time it takes each signal to go and return) or develop autonomous robots that could work semi-supervised. (Of course, if the robots are good enough, we could have them process the asteroid and just send back the good bits.) The only sure thing about an asteroid mission is that trying to run it like a lunar mission will ensure its failure while running it like an asteroid mission will make it more likely to be successful.
Mining the asteroids
OK, with all of that in mind, what will an asteroid mission look like? Well, just as has been the case for the Moon and Mars, we’d start by finding where we want to go. We need to do a full-sky survey that will locate, track, and spectrally identify every asteroid or other object more than five meters across in the inner Solar System. NASA has been working on that survey for nearly twenty years now, but it has always been underfunded . Though NASA now has the orbital elements for about 230,000 asteroids and has identified another 390,000, that is by no means a complete catalog! Fortunately, private industry may be stepping up to help. Recently Planetary Resources announced the funding of their first space telescope dedicated to finding asteroids; they hope to have several dozen of them in orbit before they are done.
Once several targets are identified, the real work begins. They would want to have several options because work schedules may slip. Thus, they wouldn’t train to go to “asteroid 23456″ or “asteroid 31415″; instead they’d train to go to an asteroid. As noted before, there are at least 79 different possible asteroid targets that are known right now. So the number of targets isn’t a big problem, nor is the frequency of launch windows. Indeed, there are more launch windows for asteroid targets than there are for lunar and Mars missions combined!
If we are sending people, then they would launch into LEO along with their living quarters, propulsion unit, and mining equipment. Once in orbit, the whole mass would be joined into one ship that was launched toward an asteroid. The crew would head toward the asteroid and then extract the water and other valuable materials  before heading back to Earth. Net time, about a year. Net gain, damfino.
If we are sending robots then we would still want to assemble everything in LEO before shipping it off to the asteroid. But that is a much simpler problem as we don’t need shelter or food for the robots (unless you count batteries). The robots could be sent on a slower trajectory than people, which would allow for longer mission times. The real question with robots is do we process the asteroid in place or bring it back home?
The real sticking point for an asteroid mission is that we haven’t really done one yet. Right now, we are in the same place that the US was with Apollo 6 or 8: we’ve sent probes to the general area that we want to go (Surveyor and Ranger for Apollo, DAWN and Hyabusa for asteroids) but haven’t actually put boots on the ground yet. As Apollo 13 showed, there can be a lot of unexpected things that go wrong with any space mission and a long duration deep space mission has a much slimmer margin for error than just about any other type of exploration.
So, with all of that in mind, how does exploring the asteroids look on our four point checklist?
What do we learn?
This is perhaps the best part of going to the asteroids. Where going to the Moon or Mars teaches us about mature planets, going to the asteroids teaches us about planets before they formed. We get samples of the primordial muck that formed the Solar System (C-group) along with samples from planets that almost formed (S- and M- types) and possibly even some prebiotic matter that could have kick-started life on Earth (the P-type). We would learn at least as much as we would from going to a planet, and possibly much, much more. In addition, a six-month or year-long visit to an asteroid would help us as an intermediate step between the short week-long jaunts out to the Moon and the much more arduous three- to five-year trek to Mars. Finally, learning to move asteroids would help us the next time that a dinosaur killer takes aim at Earth.
What can we do next?
This is a at least as great a strength for the asteroids as it is for the Moon. The asteroids are as rich in resources as the Moon and have a much lower delta vee budget (though a longer travel time). If the asteroid resources are used in space (e.g., water for fuel, metals for manufacturing), then they save the cost of shipping everything up from the Moon’s gravity well and back into the ecliptic plane, albeit at the cost of longer delivery times. That cost can be minimized by having multiple asteroid missions running concurrently.
What does it prove?
This isn’t as great a strength as it was for Mars, but better than it is for the Moon. As with Mars, asteroids are implicitly but not explicitly mentioned in the OuUter Space Treaty so exploiting them for resources may not be forbidden (just very, very difficult – I see committees – lots of them). And going to the asteroids also demonstrates that our technology has continued to improve in a way that returning to the Moon won’t.
What does it cost?
This is where the asteroids wins, hands down. Where a return to the Moon would cost somewhere between $93 and $280 billion, and going to Mars would cost in the neighborhood of $91 to $911 billion, going to the asteroids could be done for free. More exactly, it could be done in such a way that it makes money for the taxpayer. If NASA goes to the asteroids, then it would likely cost between $2 and 20 billion for a robotic mission. And most experts believe that the costs for a private mission would run about the same. However, unlike NASA, a private mission could sell the water and minerals extracted from the asteroid and make several billion dollars , almost all of which would be taxable. So the company would make $10 billion and pay $2 billion in taxes to the US government, meaning that we would get the mission for free.
The next post will summarize everything we’ve discussed and try to come to some conclusions.
 Please notice the “at least” in each of those statements. Those are the asteroids that we know about. But asteroids are tricky little buggers to catch. They are small, dark, and fast moving, all of which make it very hard to identify them and track them. The numbers that I give are based on the known asteroids; there are probably at least 1/3 more in each group that haven’t been discovered (i.e., I wouldn’t be surprised if we found out that there were actually 6700 Apollo asteroids out there).
 Why I include comets will be obvious in a moment.
 This is actually a bit of a circumlocution because the actual situation is much murkier. Because asteroids are so small, we cannot measure their sizes directly. Instead, we measure the amount of light that they reflect (the “H magnitude”) and assume that the asteroid is spherical (a bad first approximation for the smaller asteroids) and has an albedo of .15 (a good first approximation); from that, we can relate the amount of reflected light to the asteroids size and distance. But an oddly shaped asteroid can have a magnitude that is too big or too small, and the asteroid’s composition can change the albedo dramatically. But this works for a first approximation.
 There are lots of subdivisions and overlaps that show two things: (1) we haven’t learned enough about asteroid formation to develop a consistent system, and (2) planetologists are splitters not lumpers.
 Please remember that, to a planetologist, an ice is any solid material that would be liquid or gaseous at Earth normal conditions. So you can have water ice, ammonia ice, and even formaldyhyde ice.
 The 8:13 tells you how many orbits the outer planet makes (Earth, 8) compared to the inner planet (Venus, 13).
 I’m assuming a free-fall Hohman-style orbit, simply because they are the current best way of getting between planets in space. As mentioned on the Mars Next post, if we had a better ion drive then we could speed from Earth to an asteroid in under a week but that will require drives at least ten times more powerful (and efficient) than we currently have.
 You may have noticed that the word “known” keeps popping up. That’s because, as noted previously, we haven’t discovered all of the asteroids. If you increase each number by about 1/3, you’ll probably be in the right ballpark (though some have suggested that a factor of ten may be more appropriate).
 Just a quick reminder for the non-science geeks reading this: an AU is an “astronomical unit”, equal to the mean Earth-Sun distance and set at 149,597,870,700 m. Just as parsecs and light years are handy yardsticks for interstellar distances, AUs are useful for comparing distances in the Solar System.
 That equation is one of the strongest proofs of the greenhouse effect as it predicts the average temperature of the Moon almost perfectly but not that of Earth.
 The Keystone pipeline is an exception, not a rule. If it were easier to build a refinery in Canada or the northern US, then the pipeline wouldn’t be built and the ores would be processed there and the oil shipped here.
 Just as God and Werner von Braun intended…
 How large? Consider NASA’s notional ion drive to Mars, which was assembled in LEO before heading off to the red planet. The fleet had five ships, each massing 360 tons, that all set off for Mars at the same time.
 As of right now, that plan appears to be a non-starter. The House wants to cut NASA’s budget severely, the Senate wants to keep the budget where it is but use it to build a rocket to nowhere, and the White House wants to send people to an asteroid and not asteroids to the people.
 I’m assuming a density of 3000 kg/m3 and a relative velocity of 17 km/s (i.e., way too high). If you’d like to play with the parameters yourself to find out how large a rock we can drop before things get ugly, head over to the Imact: Earth! website.
 At one point, the search for asteroids was paid for by the US Air Force because NASA stopped funding it!
 This is one place where the asteroids have the Moon and Mars beat all hollow. A single asteroid such as Eros could have enough precious metals and other valuables to be worth $20 billion!
 Some folks put the estimates into the trillions for some of the more exotic asteroids. This may be where some of the frustration from the Moon First and Mars Next crew comes from; no economic analysis of those missions ever shows them as doing more than breaking even – which is why it is so hard to get private companies interested in those missions other than as NASA contractors.
Our third candidate for exploration is Mars. Though the planet is less than half the size of Earth and has but ¼ g, it has some advantages that are unique to space exploration, namely an atmosphere, known massive deposits of water ice, and the possibility of extraterrestrial life. The first is important because it allows the spacesuit that would be required to be simplified somewhat , because it reduces the temperature extremes that the Moon or an asteroid will experience, and because it provides a vast reservoir of CO2 and other gasses for industrial use (e.g., growing food). And the second is important because it would provide the opportunity to synthesize rocket fuel for the journey home while it also provides a growth medium for crops (and people). And the third is important because it would be the most significant scientific finding of the century.
But having an atmosphere also means being subjected to the vagaries of weather. Mars is famous for its dust storms, with winds that whip across the plains at up to 60 mph; these dust storms can last for a month at a time, leaving behind a slowly thinning haze of dust in the air. As is the case with lunar soil, it is possible that the Martian dust would be a health hazard. Unlike the lunar soil, the Martian dust does not appear to be electrostatically charged and so astronauts should be able to clean themselves by passing through a simple water curtain in the airlock but the problem still needs more work. And an airlock will definitely be required. The Martian atmosphere is 0.09 psi at what would be sea level if Mars had seas; that is roughly equivalent to the atmospheric pressure you’d find 31 miles up in the Earth’s atmosphere. However, though Mars’ atmosphere is thin, it is also very thick; the Martian atmosphere extends nearly 50% further out than Earth’s simply because Mars has a much smaller gravity field.
As a result, we can use aerobraking on Mars as a way of reducing our speed; thus, you can actually land objects on Mars more easily than you can land them on the Moon. That’s the good news. The bad news is that it is harder to launch something from Mars than it is to launch it from the Moon, simply because the atmosphere gets in the way . So you need no delta vee (or very little ) in order to land on Mars, but you’ll need at least 5 km/s to get back up into orbit.
Once we are on the surface of Mars, the planet is our oyster. Mars has a wider variety of geology than the Moon thanks to its much more complex history. Mars probably underwent a brief, abortive period of plate tectonics before settling into being a one-plate planet and has also had wind and water acting as geopmorphic agents in addition to the impact cratering which serves as the Moon’s main form of resurfacing. Mars has the tallest known volcano, a chasm larger than the USA, and abundant (possible) hot springs which could have once teemed with life – or may still harbor life today!
And that last point is the most important. It is incredibly unlikely that there might be life on the Moon; the conditions are just too extreme. But Mars is just barely within the range of possibilities for life; we already know of terrestrial organisms that could live under Mars conditions. So, though the Moon offers us ice, Mars offers us ice and the possibility of life. It is easy to see why Mars Next types are in favor of going there next.
But is it possible? Unlike the Moon, where trip times are typically just a few days and launch opportunities are plentiful, a free-fall trip to Mars and back would take a minimum of 450 days with a 500 day stay on Mars if we want to take advantage of the lowest energy orbits ; a launch window for one of these missions opens every 26 months. Though some astronauts have lived onboard space stations for as long as 437 days, that was with continually changing crews and fresh food delivered on a regular schedule. There have been attempts to simulate a Mars mission on the ground (e.g., Mars 500, H-SEASI) but these did not include all of the effects of microgravity or the increased radiation exposure that astronauts would face on such a long voyage.
However, being unlike the Moon isn’t all bad when it comes to trip times. Unlike Moon missions, which were all launched from Earth and sent to the Moon directly, Mars (and asteroid) missions would probably be launched from Earth into LEO where the various parts would be assembled into a single unit before being launched toward the final destination. The most common cause of missed launch windows is weather; by launching from LEO, the problem of missing a launch window is reduced (but not eliminated). In addition, launching from LEO allows for the use of ion drives such as the one on DAWN which is powering the probe as it flies from Vesta to Ceres. Using an ion drive means that the usual orbits no longer apply; instead of a 250 free-fall orbit to Mars, you can take a faster one  or choose a new and better launch window .
The long trip times do more than take up time; they also increase the risks of the venture. The reason that we were able to get the Apollo 13 astronauts back safely when their oxygen tank exploded was because they were only three days away from Earth. If that accident had happened on a Mars mission, then they would not have survived. Similarly, the odds of having a major solar flare during a three day journey are much lower than the odds of having one during a 250 day one. Finally, it is possible (but not easy) to pack a small command module with enough oxygen, food, water, and toilet paper to last for a week. It is not possible to do so for a three-year voyage. Going to Mars will require advances in recycling , radiation protection, and (perhaps most importantly) social group stability .
However, strange as it may seem, the one thing that the longer trip won’t do is run up the costs. According to NASA’s 90 day plan , a unified strategy of going back to the Moon and then heading out to Mars would cost $911 billion (2012 dollars), or roughly seven times what Apollo cost. But others, such as Robert Zubrin, have developed plans that would put us on Mars for a mere $91 billion (2012 dollars), or about the same cost as the most economical lunar plan.
So with all that in mind, how does a trip to Mars stack up on our four metrics?
What do we learn?
This was a good one for the Moon; it is even better for Mars. Leaving aside the question of “Is there life on Mars?” , Mars is a wonderful example of what happens when plate tectonics fails on a planet. Mars also has a wider variety of landforms than the Moon and more and more interesting ways of modifying those landforms. Where exploring the Moon would illuminate the Earth-Moon system, exploring Mars would tell us more about planets and planet formation in general.
What can we do next?
This is a strength of Mars, but not as great as it would be for the Moon. Mars could serve as a stepping stone for further exploration. Bases on Phobos and Deimos fed with water and food transported up from Mars’ surface could provide a way-station on the route to the asteroids and outer Solar System. And a telescope in Mars orbit could be coupled with one in orbit around the Moon or Earth to provide images of the surfaces of extrasolar planets .
What does it prove?
This is a strength in going to Mars. Unlike the Moon and asteroids, Mars is rich in known resources of (mostly) known size, including water, oxygen, and iron. These resources could be used to support the in situ exploration as well as providing supplies for those going into the outer Solar System. And Mars’ legal status is murkier than that of the Moon; though any exploration of Mars may also be limited by the Outer Space Treaty, it was never explicitly included in the treaty as the Moon was. And going to Mars demonstrates that our technology has continued to improve – something that a return to the Moon won’t do.
What does it cost?
This is a weakness of going to Mars. The price tag is likely to be huge, and few private groups have shown any interest in exploring the planet on their own dime . The lowest estimate is on par with a return to the Moon, and the highest estimate is simply astronomical.
So that’s the case for going on to Mars. Next post – the asteroids!
 Some have suggested that you could explore mars with what amounts to a modified scuba dry-suit.
 For example, a spot on the Moon’s equator will alternate between a high temperature of +250 F and a low temperature of -250 F. An asteroid such as Eros will alternate between +212 F and -238 F [i]. But Mars runs average temperatures that are between -23 F and -128 F, which are roughly equivalent to those near the South Pole.
 That’s why rockets on Earth go up and then head into orbit: to get out of the atmosphere. If the Earth had no atmosphere, then rockets could launch at a tangent to the surface which would make circularizing their orbits simpler.
 Those who follow planetary science know that this is actually a bit of an oversimplification. The reason that Curiosity had to do such a Rube Goldberg landing was that aerobraking only takes care of part of the problem. Though the aerobraking does kill most of your speed relative to the planet, it still leaves you with the problem of being very high up in a gravity well. Parachutes don’t work well on Mars, thanks to the thin air. Gliders have been suggested as a means of getting from orbit to the ground (and for getting around), but they are not well-tested under Mars conditions. So a combination of parachutes and rockets will probably have to be used for any manned landing on Mars.
 If we use one high-energy transfer, we can cut the stay on Mars down to 60 days. This reduces the need for supplies somewhat, but at the cost of limiting the science that can be done and increasing the mass of rocket fuel that needs to be carried along by a factor of about ten. Given that every pound we spend on rocket fuel is a pound we don’t have for food or scientific instruments, most people prefer the slower but less energetic mission.
 “How much faster?” turns out to be a very complicated question. There aren’t any exact solutions for constant-thrust orbits, but we can make some approximations. It turns out that it would take about
611 days 62.1 days (see discussion below) to fly from Earth to Mars at 0.01 g (about what DAWN’s thruster puts out). If we increase that to 0.1 g then the transit time drops down to about 211 days 19.6 days, saving us 231 days on the Hohmann orbit. And it becomes a blazingly fast 67 days 6.2 days at 1 g [ii].
 You can also use gravity assist to get to Mars or the asteroids by looping around the Moon a few times, but that doesn’t cut as much time off of the flight as you might think.
 Read: getting people to get along in the most dangerous environment they’ve ever encountered under the highest pressure they’ve ever faced. We’ve already learned valuable lessons in this from the US Navy and Air Force (submarines and missile silos, respectively) and have gained more insight form the ISS. But a lot more needs to be learned in order to keep the astronauts from going “HAL9000” on us.
 The 90 days refers to the amount of time NASA had to work on the plan, not the amount of time it would take to get to Mars.
 Given that we’ve already answered that question as “Yes!”, “No!”, and “Maybe!” using robotic probes, the only way to be sure will be to go there. And even then, there will be those who claim that we brought the life with us.
 NASA actually had a plan to do this with robotic telescopes in the 1990s, but it was cut back due to (what else) budget constraints.
[i] The temperature for an asteroid is particularly vexing as many of the asteroids have highly elliptical orbits which bring them closer to the Sun (and hence warmer) before sending them back to the colder, more distant parts of their orbits. And, of course, there are bunches of different asteroids in different types of orbit. But we’ll get into that in the next post.
[ii] So how does the VASIMR ion engine get us to Mars in just 39 days? Simple – they don’t use the over-simplifications that I did in calculating the time. A faster ship won’t follow a Hohmann orbit; instead, it will follow a tighter ellipse, which cuts down on the distance travelled and the travel time. The times for 0.01 g and for 0.1 g are about right, but the others are off and the higher the acceleration, the more they are off.
As my previous post demonstrates, one could make a strong case that the best way to further human exploration is to stop exploring space  and focus on the Earth. However, one can also make a strong case that the best way to explore space is to do what we said we were going to do in the 1960s – explore the Moon and put a permanent base on it. But why would we want to explore space? And why should we look at the Moon?
There are many reasons for exploring space, ranging from the banal (“Because it is there” ) to the political (“We gotta beat them Russkis”) to the scientific (“How did the Moon and the other planets form?”) to the economic (“There’s gold in them thar hills!”) to the practical (“You’re telling me you don’t have a backup plan, that these eight boy scouts right here, that is the world’s hope, that’s what you’re telling me?” ). And those reasons apply no mater where we decide to explore, be it the Moon, Mars, the asteroids, or some other destination. So why should we focus on the Moon?
The first, and most obvious reason, is because the Moon is both easy and difficult to get to. In terms of time, the Moon is very close; Apollo missions took just under 56 hours to fly from the Earth to the Moon. But in terms of energy , the Moon can be very difficult to get to, indeed. It takes about 6 km/s to land on the Moon following an Apollo-type trajectory. But those all landed near the lunar equator. If you want to land at the lunar poles, it takes another 2 km/s to change the plane of your orbit so that you pass over the Moon’s North (or South) pole and then another 2 km/s to change the orbit back so that you can land on Earth . There are quite a few other destinations in space that require less energy to get to than that 10 km/s (but most of them require a lot more time as well).
The next reason that we should focus on the Moon is because it is the nearest body that is known to have water ice. This is important because water is used for more than just drinking in space; it is also the basis for fuel. When the Saturn V and the Space Shuttle went up, their main engines burned oxygen and hydrogen together to form energy (in the form of thrust) and water (in the form of a whopping huge vapor trail). By harvesting lunar ice and processing it to make liquid oxygen and liquid hydrogen, we could save ourselves the cost of bringing fuel up from Earth. How much does that save? An estimated $11,000 per kg! So the 126,000 kg of fuel burned to put an Apollo module into a typical Earth-Moon orbit would cost $1.4 billion in space! If mining ice from the Moon cuts the cost by just 25%, that’s a savings of $350 million.
However, the lunar ice that we know about is located near the poles. There are suspected deposits in both the northernmost and southernmost parts of the Moon. Those in the south pole are generally (but not universally) taken as proven, thanks to the probe that NASA crashed into the Moon; it raised a plume of OH which is likely to be related to the presence of water ice (but could be due to other minerals). Some estimate that there may be as much as 600,000,000,000 kg of water ice laid out in thick deposits. But others have fairly convincing evidence that the lunar ice is actually much thinner and sparser than the optimistic estimate. The only way that we will know for sure is if we go and check, either in person or by robot.
Of course, ice isn’t the only goody to be found on the Moon. There are also abundant deposits of aluminum, iron, magnesium, and possibly even rare earth elements , not to mention the philosopher’s stone of He3 . In addition, the Moon would make an amazing place to put a radio telescope (placed in a crater, shielded from Earth’s radio noise) or even an optical telescope (no need for adaptive optics means Hubble-quality images with much less fuss). However, working on the Moon may prove to be a bit of a problem; all of the mining techniques we know well have been developed to work under Earth gravity; using them under 1/6th g will necessarily change many aspects. In addition, some medical researchers suggest that the fine-grained dust that coats the Moon may pose a health hazard not unlike asbestos.
But let’s assume that we can overcome those problems and that water ice (or other, equally valuable minerals) is plentiful. How would we go about getting it? In 1959, Werner von Braun proposed building a permanent lunar base after assembling many of the parts in low Earth orbit . If we had followed his Project Horizon blueprint, we’d have had a completed moonbase by an optimistic 1966 and a realistic 1974 at a cost of just $46 billion  and seven years. But we didn’t start heading for the Moon until 1961 and we insisted that we be there in less than nine years. That meant that Project Horizon wouldn’t work; instead, we went with Apollo at a cost of $130 billion . But Apollo was supposed to continue past the landings; NASA had plans for an Apollo-based lunar base. Called the Apollo Extension System, it would have cost an additional $14 billion at a time when the nation was in an extended economic slump and when the new administration was hostile to the work of the previous one . As a result both Apollo and the AES died a quiet death.
If we want to go to the Moon today, we’ll need to redevelop the entire program. Under Bush43, that was exactly what was proposed: a return to the Moon, with the goal of establishing a permanent base. Called Constellation, the program would have cost an estimated $280 billion or more than twice what Apollo did . Fortunately, there are alternative. One of the main promoters of the Moon First doctrine is Paul Spudis, who has proposed going back to the Moon at a bargain-basement cost of just $93 billion (assuming no cost-overruns). His plan would involve sixteen launches of pathfinder robots that prepare a lunar base before the first human launch in the sixteenth year of the program, which works out to about $5 billion (or 1/3 of all NASA spending) per year. So it is clear that we can return to the Moon; what isn’t clear is if we can afford it.
And that brings us to our four metrics. How does returning to the Moon score?
What do we learn?
This is one of the strengths of heading to the Moon. Yes, we’ve been there six times before, for a total of 80 hours and 26 minutes. That’s like saying that you’ve seen America after spending the night in six different airports. There are enormous amount of things to be learned about the Moon, much less what we can learn by using the Moon as a base for radio astronomy. We still don’t know much about cratering (other than that the Moon gets hit hundreds of times each year), or the formation of the mares, or the Moon’s internal structure. Going here would help us add another planet and another data point to our understanding of how planets form.
What can we do next?
This is another strength of going to the Moon. Many of the problems that we face on the Moon are the same problems that we face elsewhere in space: airlessness, radical temperature changes, unrelenting radiation, and magnificent desolation . And some of the problems that we face in microgravity (e.g., going to the toilet, cooking food, bone loss) are somewhat less acute under 1/6th g.
What does it prove?
This is a weakness in returning to the Moon. Though the Moon might provide us with He3 and water ice in abundance, it might not which makes it risky as a national resource. And the Moon has the added problem of the Outer Space Treaty which limits the amount of benefits (some claim to “none”) that any nation can gain from it.
What does it cost?
This is another weakness of returning to the Moon. The only time we did it, it cost $130 billion and NASA expected/wanted to spend twice that to go back. Even if we use Spudis’ rather optimistic estimate of $93 billion, that still makes it much more expensive than exploring Earth or the asteroids. And, though there are a few companies attempting to do this via free enterprise, they have not been notably successful in raising either enthusiasm or capital.
So that’s the case for going back to the Moon. The next post: Mars!
 Note: I do not support this view. I merely admit that it makes some good points.
 Elevated geek points for the reference!
 Cheesy geek points for the reference!
 In space, the best measure of how hard something is to get to is a mixture of time and energy. There are usually many different orbits that will get you where you want to go but the ones that take the least time often take the most energy and the ones that take the least energy take the most time. So mission costs are usually counted in both elapsed time and in delta vee (change in velocity) which is a measure of energy.
 Or you can actually launch so that you’ll miss the Moon and change the plane of your orbit at apogee (the farthest point away from the Earth in your orbit) which costs less energy, ride the new orbit back to Earth and back out to the Moon [i] and then enter into a lunar polar orbit. But that takes a minimum of 180 hours (just over a week). You could repeat the performance on the way back, adding another week to the total mission time, just to save 4 km/s.
 Which aren’t that rare but are badly distributed on Earth.
 Helium-3 (a helium atom missing one neutron) is widely considered to be the key to practical fusion. If we had a plentiful supply of He3 right now, we’d also have working fusion reactors, which would mean all the benefits of nuclear power (cheap, reliable, safe electricity) with very few of the drawbacks (e.g., nuclear waste, weapons-grade plutonium). And the Sun gives off large quantities of He3. Because the Moon has just been sitting there, soaking up the rays for 4.5 billion years or so, scientists think that the surface of the Moon may be saturated in He3.
 A process called “Earth Orbit Rendezvous”. It was von Braun’s favored way to get us to the Moon because each step left us with something permanent: a rocket that could get to orbit, a space station, and a lunar station. We didn’t follow that route because of time constraints.
 All costs will be given in 2012 dollars so that we can compare things apples-to-apples.
 This is another example of the time vs money problem endemic to space and space exploration. Doing it faster cost us nearly three times as much as doing it more slowly would have.
 A pattern that continues to this day, sadly.
 The egregiously high cost (coupled with the low level of support in Congress) is what ultimately doomed Constellation. One common complaint was “how could it cost twice what Apollo did to go to the Moon when we already knew how to do it?”
 Godly geek points for the reference!
[i] Passing through the van Allen radiation belts twice on the way.