Relative value of Mars Vs. Mars Orbit

[j05h]

The first human Mars flights should establish an orbiting outpost instead of landing. This is a project (unlike Mars or Moon landings) that can be built right now. Instead of worrying about site selection on Mars, bring dozens of rovers and balloon-kites and explore the whole planet from above. Seek ground truth and mining opportunities further along.<br /><br />We covered this extensively as a Phobos operation in my "Private Mars Missions" thread, and I'd like to expand it. We've been discussing the Mars Direct ERV and favorite Mars architectures lately. Well, what is the value of landing at a single site on Mars (and developing a range of new tech) raised against establishing an ISS-scale station in Mars orbit? This Mars outposts could control dozens of robots across Mars and the moons while operating in a known environment. Thoughts?<br /><br />Everybody favors landing on Mars for the adventure, but is the real value in staying in orbit there? Is "Phobos First" the answer to early and sustainable Mars exploration? It seems like an easier first step that can further lead to landings and settlements. <br /><br />Here's the old thread as well, it's pretty interesting:<br /><br />http://uplink.space.com/showflat.php?Cat=&Board=businesstech&Number=503952&page=&view=&sb=&o=&vc=1 <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[qso1]

This would seem to be the prudent and logical approach normally characterized by NASA projects. You may not necessarily need an ISS sized craft in mars orbit. Getting something that large to mars would probably be as costly as a modified Zubrin landing/base mission.<br /><br />But I would favor this approach as opposed to manned flyby.<br /><br />There are a few reasons why we should go that have little to do with pure adventurism. One is seeking out evidence of life or fossilized remains. If life were found, the next step would be cataloging by species as its likely more than one specie of microbiota will be found. Cataloging and studying life if discovered, would be ideal if done on site. As you mentioned, an orbital mars mission could be a stepping stone to eventual landing missions.<br /><br />Obviously microbiological life forms could be discovered by robots remotelly operated from the orbital station but eventually, I would think we would want to send humans to do the detailed work that is or may be beyond the grasp of robotic capabilities. The orbital base could lead to the robotic mission to find life and if life is found...lead to humans on mars.<br /><br />The downside is that politically, as long as the effort remains within the realm of taxpayer funding, the timetable to a human landing from the first orbital outpost could be a decade or more and subject to the political winds as a result.<br /><br />The other problem is that much of the unmanned missions that can be conducted from an orbital station can also be sent direct from earth as we do them now. The possible exceptions being large unmanned craft that might require a way station in mars orbit. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[keermalec]

Economically speaking I would also favor setting up an orbital station around Mars, to actually landing on the surface. However, as Zubrin pointed out in his Mars Direct scheme, one reason against this is the high level of radiation encountered in Mars orbit, due to the absence of a magnetic field: 20-50 rem/year.<br /><br />According to Zubrin, on the martian surface itself, combining the effects of Mars' distance from the sun and its thin atmosphere, cosmic radiation is reduced to 6-13 rem/year.<br /><br />According to NASA regulations indicated on this site, maximum acceptable radiation dose for an astronaut is 50 rem/year. This is way more than the current US law limit for radiation workers at 5 rem/year. <br /><br />Finally, according to this article, radiation doses in Mars orbit would be roughly the same as that experienced on the ISS, ie 0.1 REM/day or 36.5 REM/year. However, doses in transit would be twice that, or 73 REM/year.<br /><br />Considering the amount of radiation absorbed during the trip to Mars, it seems more prudent that astronauts there spend most of their time on the surface rather than in space. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[Boris_Badenov]

If science were the only reason to go, that would be the most cost effective mission plan. But, colonization cannot be accomplished in this way. <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>

 

[scottb50]

Economically speaking I would also favor setting up an orbital station around Mars, to actually landing on the surface. However, as Zubrin pointed out in his Mars Direct scheme, one reason against this is the high level of radiation encountered in Mars orbit, due to the absence of a magnetic field: 20-50 rem/year......<br /><br />I don't think we need to leave a manned Station. Just a couple of Modules to serve as a lifeboat. The first few missions will establish a base. The first leaving when the second arrives. Once a base is established and manned, less frequent flights could be phased in. <br /> <div class="Discussion_UserSignature"> </div>

 

[j05h]

<i>> If science were the only reason to go, that would be the most cost effective mission plan. But, colonization cannot be accomplished in this way.</i><br /><br />This is about the near-term value of orbital and ground exploration. I thought I was pretty clear that this was about the first flights to Mars, and that landing, settlment and mining are all in the cards. My post is inspired by the fact that we already have the technology to explore Mars from orbit. Once a "base camp" is established in Mars' orbit, landers, Habs and other surface hardware can be stockpiled there. The difference, to me, in the two approaches, is that we could have an FGB and Nautilus orbiter within 10 years, whereas current plans put landing on Mars in the 25-50 year timeframe. <br /><br />I actually see the orbital base-camp as a way to fast-track settling Mars. It'd put Mars in-your-face from the end of the Rover missions until first landing, instead of putting Mars in the back seat. <br /><br />One last point, too, is that we should be planning on colonizing more than just Mars: Phobos, Deimos, Ceres and the Main Belt should all be early candidates. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[Boris_Badenov]

IMO, the only thing stopping us from beginning colonization of Mars right now, & I really do mean today, is the availability of affordable travel to <i> & from </i> Mars. But this is not a show stopper. The first steps to colonization can be taken by beginning to stockpile supplies & equipment right here on "Old Terra"<img src="/images/icons/smile.gif" /> & as transport becomes available start shipping the stuff at that time. While your orbital outpost has it's benefits, stockpiling right here dirtside does too. <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>

 

[qso1]

Keermalec:<br />Economically speaking I would also favor setting up an orbital station around Mars, to actually landing on the surface.<br /><br />Me:<br />Good point. I had forgotten the radiation problem. Bad as it is on mars, its apparently worse in mars orbit and I say that because I thought the rad levels were the same for both. I didn't think there was enough atmosphere to shield the surface. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[j05h]

<i>> IMO, the only thing stopping us from beginning colonization of Mars right now, & I really do mean today, is the availability of affordable travel to & from Mars. But this is not a show stopper. </i><br /><br />Any kind of travel would enable this, but yes, cheap travel would ramp it up. The journey is definitely the hardest part, followed by surviving. Elon Musk has said that one of his goals is a $9M ticket to Mars for individuals as a long-term goal of SpaceX/himself. <br /><br />This is part of my questioning the value of going planetside, especially early in Mars exploration. This is especially true with either a pure-exploration approach or an industrial approach if Phobos or Deimos are hydrous. Don't get me wrong, I'd like to be boots-down there someday. But, we already know how to live in freefall, and have the systems for it off-the-shelf (or nearly -see MarsPost). Mars orbit and a few comsats offers global control and exploration across Mars, in realtime. Of course you could do the same ground-side with an uplink <img src="/images/icons/wink.gif" /> but that includes the added expense of landing and supporting that crew. For exploration, this is a huge leverage over a single site approach, considering our advances in robotics. Imagine having dozens of MER rovers working in realtime across Mars while a crew works in a bunch of modules in orbit. This is an expedition we could build today, on a macro level. Another argument for Mars orbit (or Phobos First) is bio-protection. We don't know what awaits there, and a massive robotic look-see first might make sense. My preferred platforms are rovers and balloons like the Planetary Society's Mars Snake. Of course the goal is eventual mass colonization (across the Solar System and BEYOND!) but what are the near-term implications of staking out the high ground first? <br /><br />On an industrial level, Phobos and Deimos offer a huge potential as mining operations to provide volatiles and building material. <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[brellis]

The 'orbit' should cycle between Earth and Mars. This reduces transportation costs and opens more possibilities early on, like sample-return and mining of Pobos and our own Moon for ice, fuel, etc. <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[thereiwas]

'orbit' in quotes. You couldn't really coast back and forth, because both endpoints are moving. You would need an adjustment at each end each time around.

 

[dragon04]

I can't see spending the money and resources to fly to Martian Orbit and not make planetfall in terms of a manned mission.<br /><br />Robotic missions do it much more cost effectively all the time. <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[dragon04]

Moreover, given the realties, how do you sell a manned Mars Orbital mission to the taxpayer and Congress in terms of what an expensive manned mission could return for the investment as opposed to several robotic orbital/rover/sampling missions could do for the same money?<br /><br />Nothing short of an American Flag on the Martian surface planted by an American Astronaut would seem to suffice if anything sufficed at all. <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[gunsandrockets]

<Moreover, given the realties, how do you sell a manned Mars Orbital mission to the taxpayer and Congress in terms of what an expensive manned mission could return for the investment as opposed to several robotic orbital/rover/sampling missions could do for the same money?><br /><br />Manned vs unmanned is a false dichotomy. A manned plus unmanned partnership is the most effective way to explore. <br /><br /><Nothing short of an American Flag on the Martian surface planted by an American Astronaut would seem to suffice if anything sufficed at all. /><br /><br />An orbital mission is okay if it is understood as a stepping stone to a later manned landing mission.<br /><br />A manned landing mission to Mars is a huge step. It's best to approach that goal in smaller meaningful steps. The first step should be a small manned flyby mission. The second step as a fully crewed orbital mission. Leading to the third step of a manned landing mission.<br /><br />It's not as if an orbital mission would be pointless for a manned mission. Other than real-time control of Mars surface rovers the crew would focus on exploring the moons of Mars. Perhaps even establishing an outpost on Deimos that future crews could return to for shelter or for refuelling their spacecraft.

 

[Kalstang]

I just skimmed through the thread but I didnt think anyone mentioned this...<br /><br />I think money wise it would be smarter to land on mars to build the base. You can tell where a good landing spot would be from Earth. Not just a "landing" spot but also spots that could be high in the mineral deposits that you will need so as to make building easier. ie why transport a steel rod which not only takes up more space but also because the weight uses up more fuel when you can just make one when ya get there? I would imagine that you could save enough space and fuel by just adding a small portable smelter and a few molds when compared to bringing along a bunch of rods or beams in order to make either a camp on Mars or a space station above it. <br /><br />I agree that a SS would be far more perferable. But perhaps a planet base would be more feasable. <div class="Discussion_UserSignature"> <font color="#ffff00"><p><font color="#3366ff">I have an answer for everything...you may not like the answer or it may not satisfy your curiosity..but it will still be an answer.</font> <br /><font color="#ff0000">"Imagination is more important then Knowledge" ~Albert Einstien~</font> <br /><font color="#cc99ff">Guns dont kill people. People kill people</font>.</p></font><p><font color="#ff6600">Solar System</font></p> </div>

 

[gunsandrockets]

<Economically speaking I would also favor setting up an orbital station around Mars, to actually landing on the surface. However, as Zubrin pointed out in his Mars Direct scheme, one reason against this is the high level of radiation encountered in Mars orbit, due to the absence of a magnetic field: 20-50 rem/year.><br /><br />The radiation factor makes it even more imperative that a Mars orbital mission focus on exploration of the moons of Mars.<br /><br />Instead of a free flying Mars orbital habitat, the crew should place themselves on the surface of one of the moons of Mars. A surface habitat would have the moon underneath as radiation shielding. The material of the moon could be sandbagged for top cover radiation shielding. There might even be a convenient crater that the habitat could be placed into to improve shielding.<br /><br />I favor Deimos over Phobos for manned presence for a few reasons. Deimos is higher in the Martian gravity well than Phobos, which would save vital spacecraft propellant. And the long orbital period of Deimos is almost synchronous with the rotation of Mars, making Deimos an ideal platform for direct communication with remotely controlled rovers on the surface of Mars. <br /><br />Since both moons are tidally locked the same face is always towards Mars, so a surface habitat on the side of Deimos facing Mars could be in direct continuous contact with a rover on the Martian surface for over 60 hours at a time. This is ideal for a network of surface rovers which are on opposite sides of Mars. Long uninterrupted contact is possible but access to the other rovers is also possible, as Demos orbits slightly more slowly than Mars rotates.<br /><br />Even though I think Deimos is the best place for long term orbital habitation, any orbital exploration mission should also visit Phobos. But if Phobos was chosen for habitation over Deimos, one advantage is Mars is so close to Phobos that Mars would provide some overhead radiation shielding t

 

[j05h]

<i>> I think money wise it would be smarter to land on mars to build the base. You can tell where a good landing spot would be from Earth. Not just a "landing" spot but also spots that could be high in the mineral deposits that you will need so as to make building easier. ie why transport a steel rod which not only takes up more space but also because the weight uses up more fuel when you can just make one when ya get there?</i><br /><br />Manufacturing will probably come once there are sizable numbers of people and robots there. At that point all of cis-Mars space will be utilized. This thread is more focused on where to start. No one is going to go there and start making I-beams immediately - there is exploration and water-collection (and other stuff) that needs to happen first. <br /><br />What are the pros to Mars for starters? What are the cons? Same for Mars orbit and moons - what are the real advantages and limiters?<br /><br />From a space-systems standpoint, we already know how to live in freefall. It's expensive to get there, moreso to get down to the surface and back. It's probably safer once you are groundside, but you still have at least a launch to survive after (vs. a fairly simple TEI burn from orbit). The surface has science and resources, but the moons also probably have volatiles in quantity. The major advantage, IMHO, to Mars' moons (if they are water-bearing) is that once the technology and skills are there to mine them, the same can be extended into the Main Belt and it's untold riches. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[j05h]

<i>> The radiation factor makes it even more imperative that a Mars orbital mission focus on exploration of the moons of Mars. </i><br /><br />Mars may or may not have a more benign radiation environment than orbit. There is conflicting data. The only real solution is living under water or plastic for protection. Water is much easier to aquire, polythylene is easily transported. Digging into Phobos or Deimos offers many opportunities along with decent radiation protection. If water can be mined on the moons, a hard slag "cement" could be used and injection-molded or sandbagged. My prefered location is Stickney crater, a massive structure facing Mars on Phobos, gotta love those tidal-locked moons. <br /><br />Phobos does receive some thermal moderation from Mars, not sure about Deimos. <br /><br /><i>I favor Deimos over Phobos for manned presence for a few reasons. </i><br /><br />For supporting surface operations, Phobos will be easier to reach. It's the opposite, of course, if you are shipping water and methane back to Earth orbit. Interesting points on telecom, I've always assumed that an orbital outpost would deploy a bunch of relay satelites. I'm not sure the advantage of a slow-moving moon if the goal is global C-n-C, both are close enough to Mars, but Phobos is only 3000 miles above the surface.<br /><br />Deimos has a 30+ hour orbital period, so it cruises slowly eastward to a Martian viewer. Wiki says it is visible for 2.7 days before setting, so that is how much time a crew would get to operate a rover line-of-sight. It would be interesting because it would allow the crew to move from one locale to another and focus on each for several days at a pass. Phobos orbits fast enough to rise from the west and cruise eastward, which is why I assumed baseline of relay sats in the old "Private Mars Mission" thread.<br /><br />The real determinant between the two moons, IMHO, is where is the water? If one is hydrous, that should be our focus (along with telepresence Mars expl <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[j05h]

<i>> Moreover, given the realties, how do you sell a manned Mars Orbital mission to the taxpayer and Congress in terms of what an expensive manned mission could return for the investment as opposed to several robotic orbital/rover/sampling missions could do for the same money?<br /><br />Nothing short of an American Flag on the Martian surface planted by an American Astronaut would seem to suffice if anything sufficed at all.</i><br /><br />Dragon, you're assuming business as usual to get there. This is not necessarily the case. Mars exploration may be carried out by NASA, but it could just as easily (moreso in some ways) be done by another entity or consortia. With enough money, you could buy your way there starting now. The first Mars flight, even a rude flyby or modest orbiter, is going to be the media event of the century. Perhaps billion$ in Internet and pay-per-view offerings. My working assumption is that the first Mars/cis-Mars explorers will be there with profits and notoriety in mind.<br /><br />If Mars-Orbit-First were proposed by NASA, they would have to explain it simply, directly, to the People. "We're going to drop 2 dozen Rovers on the surface and drive them like crazy for a couple of years. While we're doing that, our mining partners will be creating a water mine on Deimos" or whatever the reasoning. I'd take a Mars orbiter over Apollo-the-Retreaded any day. What would make you think they have the capability to do it? By the time they can, everybody will already have access to Bigelow hardware. <br /><br />What would be the advantages or disadvantages for a first-flight by NASA of the surface or orbit? What about for the putative private consortia? Got any pros or cons to add? <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[scottb50]

I think it's the chicken or the egg thing, do we pile on Deimos then go on to Mars, or do we do both at the same time?<br /><br />I think Deimos could be used as a base for a number of reasons, if everything goes to @*%$ on Mars it would be a safe place to await rescue. Docking to a Module on Deimos, a six year old could do it after five minute training with a game-boy or x-box.<br /><br />It would be nearly identical with docking to a Module or a group of Modules anywhere in Space, the little bit of gravity would require adjustments, a few thruster firings would be needed but again it should be easily done manually and performed automatically with even better results.<br /><br />I would definitely leave at least three Modules on Deimos to accept inbound Cyclers; provide a safe haven and provide Mars wide communications and an Earth link.<br /><br />Generally it would be unmanned, or intermittently staffed. When a Cycler arrives the Deimos base gets maintenance and operates manually, when inbound flights are not planned a caretaker staff, researchers, support staff and tech people might be on board or the Station is controlled from Earth or Mars, or hopefully both, if empty.<br /><br />Of course you can also easily get to the surface of Mars from Deimos, or back. A station at a lower orbit would use less propellant both ways, but the protection provided by Deimos is worth it when you are transiting people. <br /><br />I'm all for going to both, with Deimos being a regrouping and jumping off point to Mars. After that first cycler it gets easier. <br /><br />With the first trip the Cycler stays until the Deimos and Mars base are up and running and the next Cycler arrives. Future missions are coordinated as needed based on need and orbital geometry.<br /><br />Fifty years ago nobody climbed Everest, now it's a junk yard. And there's nothing there, except being there. I haven't been there. I would rather be on Mars than there, if it came to it. <br /><br />You can drop as many rovers a <div class="Discussion_UserSignature"> </div>

 

[brellis]

hi T.I.W. <br /><font color="yellow">'orbit' in quotes. You couldn't really coast back and forth, because both endpoints are moving. You would need an adjustment at each end each time around.</font><br />I was making quick casual reference to the Cycler-Orbiter as described in Buzz Aldrin's Mars Cycler plan. <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

 

[JonClarke]

I would say it is a given that Mars surface has a more benign radiation environment that Mars orbit. The atmosphere provides 6 g/cm of shielding at the zenith at Martian datum, more shielding for oblique radiation.<br /><br />As for water on the Martian moons there are several things we need know first before we can factor it it to our plans. Whether there is any water (there is a good chance that both moons are similar to the anhydrous weathered S-type chondrites rather than the water - and carbon - bearing C type). How to mine, extract and purify the water in essentially zero G. How to dispose of the waste materials. I think it is reasonable to assume these challenges have been met for later missions, but we had better not count on them for initial ones.<br /><br />Incidently the whole challenge of waste rock disposal has never been addressed in any asteroid or small moon mining scenario I have seen. But a solution is absolutely essential.<br /><br />Jon<br /><br /> <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[scottb50]

The problem with Aldrin's cycler is it would still need about the same amount of energy to accelerate the payload to rendezvous with the cycler and to then get it onto Mars and visa-versa, as it would to just go to LMO from LEO. You got to get into the same orbit as the cycler at both ends. <br /><br />This way cyclers would get maintenance and overhaul time in LEO. Who knows liberty at Mars might turn into a big business. <br /><br /> A Cycler consists of seven Modules, three Standard Modules and four Extended Modules. Each Module is divided into three sections with movable pistons with bank vault hatches in the center. <br /><br />Typically the aft section would be filled with water, as that end always faces the Sun, it would provide protection while in open Space. The middle and forward sections could be set up in any size and configuration needed by simply moving the pistons. <br /><br />One Outer Module would be the Bridge in the forward section, crew quarters and services in the middle section. The other Outer Module would provide passenger accommodations and services.<br /><br />Four extended Modules, having two additional Segments, would connect the three standard Modules so that they spin around the central Module. Additional Modules could be added to increase gravity in the end Modules. The central Module could be a zero G playground, or mostly water and cargo with a small playground. <br /><br />Additional Modules, or groups of Modules, are added or removed as needed.<br /><br />Power comes from Upper Stages used as Tugs. The number needed Dependent on loading. A number of Tugs would detach and return to LEO after providing a good boost to the outbound vehicle. Others would be refueled en-route and used to enter LMO as well as for return to LEO.<br /><br />For the return to LEO a number of Tugs would also return to LMO, others would be used to get into LEO, the Core and any cargo Modules, and a bunch of empty fuel tanks would dock in LEO to a Station. Rendezvous Tu <div class="Discussion_UserSignature"> </div>

 

[j05h]

<i>> I would say it is a given that Mars surface has a more benign radiation environment that Mars orbit. The atmosphere provides 6 g/cm of shielding at the zenith at Martian datum, more shielding for oblique radiation. </i><br /><br />Good point on the oblique angle protection. Something I read recently indicated (as w/ spacecraft protection) that Mars' atmosphere caused dangerous decay products at surface level (from cosmic rays and solar particles). Either way, future settlers and explorers will probably live under a layer of water for protection.<br /><br /><i><br />As for water on the Martian moons there are several things we need know first before we can factor it it to our plans. Whether there is any water (there is a good chance that both moons are similar to the anhydrous weathered S-type chondrites rather than the water - and carbon - bearing C type). How to mine, extract and purify the water in essentially zero G. How to dispose of the waste materials. I think it is reasonable to assume these challenges have been met for later missions, but we had better not count on them for initial ones. </i><br /><br />What is required is a serious effort to catalog both moons, preferably with landers. If they are bone-dry S-types then they wouldn't be as useful as hydrous C-types. Water really is king. As for mining, my working assumption is either zero-G tunnel-boring machines that chew regolith and split water from other material, or bag-and-heat schemes that do the same. These are both for reclaiming ice, not processing hydrocarbons. <br /><br /><i>> Incidently the whole challenge of waste rock disposal has never been addressed in any asteroid or small moon mining scenario I have seen. But a solution is absolutely essential.</i><br /><br />Some have addressed it, but usually the assumption is to just let it drift, which is awfully short-sighted. My solution following a tunnel-boring harvester would be for the "shield" of the TBM (the long casing on it) to have outlets <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>