You are not logged in.
I have raised this post to explore the advantages and disadvantages of a Phobos-First approach for Mars exploration and colonisation.
I believe a Phobos First approach offers numerous advantages. Most significantly, it allows manned exploration of the Mars system to begin at lower state of technological readiness and with smaller initial investment than would be required for manned Mars surface missions and with more rapid returns of investment. As the Phobos regolith likely contains a high percentage of ejected Martian material, a Phobos scientific base would also allow the existence of Martian microbial life to be determined.
The idea of using Phobos as a first stop staging post for further exploration and colonisation of Mars has been floated since at least the 1950s. A Phobos mission negates the need for Mars atmospheric entry, powered landing and high thrust propellant stages. The delta-V required to reach the moon’s surface from Low Earth Orbit is 6.2km/s versus ~11.2km/s for Martian surface. With a surface gravity 1/2000th that of Earth and escape velocity of 11.4m/s, landing on the moon would consume negligible propellant. Practically all of the Earth-Phobos and return transfers can be accomplished at low thrust levels, whereas Mars landing and take-off require high thrust liquid propellant stages, with high mass ratio and low ISP.
The potential for the moon to serve as the site for initial manned missions and colonisation beyond the Earth has improved with the development of low thrust, high ISP ion engines. The recently developed NASA NEXT ion thruster has demonstrated a propellant throughput of 450kg without failure and a 750kg throughput is expected to be achievable without design modification. The thruster has a demonstrated efficiency of 70%, a power consumption of 10KW, a maximum thrust of 0.236N and an ISP of 4190 seconds. Each thruster has a mass of 4.8kg per KW thrust, suggesting a total mass of 33kg.
Using the rocket equation for an ISP of 4190s and delta-V of 6200m/s, reveals that a 10 tonne vehicle travelling from LEO to Phobos Lagrange 1 (2.5km above Stickney) would consume just 1.6tonnes of propellant. If ten ion thrusters are used and supplied with 100kWe of power from solar panels with a specific power of 0.2kW/kg, then the total propulsion system mass is 830kg with 1600kg of propellant. Throwing in another 500kg for reaction control, computer, Earth communication, payload faring and Phobos landing thrusters, still allows a total payload of 7 tonnes, for each 10 tonnes delivered to LEO.
The relatively small mass ratio would appear to put a manned Phobos mission within the payload budget of existing launch vehicles. The Delta-IV rocket is capable of delivering 28.79 tonnes to LEO at a cost of $170million. According to Zubrin’s original estimates, a two man crew would consume some 7.8 tonnes of food, water and oxygen over a 900 day mission. This would appear to allow a remaining 12.4 tonnes of mass budget for spacecraft structure and internal systems. Zubrin’s original estimates for the ERV included 3 tonnes for the ERV cabin, 1 tonne for life support systems (could presumably be halved for a crew of two), 0.5 tonnes for reaction control, 0.5 tonnes for furniture and interiors and 0.1 tonnes each for spacesuits. If these estimates are applied to the Phobos transfer vehicle, they would appear to leave a comfortable 7.2 tonnes of payload to spare.
If additional Delta II (6.1te to LEO, ~4te to Phobos) and Delta IV rockets are used to deliver the equipment required for a manned base to Phobos, then there is potential for the transfer vehicle to serve entirely as a human transport, carrying perhaps a dozen people to Phobos, within the Delta-IV mass budget.
Using a Phobos base, Mars surface missions could be carried out using some sort of reusable SSTO. This would appear to cut the cost of an individual surface mission by a substantial margin.
Offline
There are a lot of possible advantages to Phobos exploration. I think the down side to solve is that (1) if you land on the surface of Phobos and stay there for 18 months to wait for the planets to realign for the flight home, you will be able to protect yourself from cosmic radiation (by covering the habitation) but you will be stuck in zero gee; if instead you (2) stay at the L1 point above Stickney crater, you can spin the habitation for artificial gee, but you will be bathed in cosmic radiation for 18 months.
Offline
This sounds like a couple short stay missions are in order since there is so little to be learned from going and the great risk of cosmic radiation exposure unless we bore into it to make it a traveling moon base.
Offline
Ok, I can't help myself.
How about a giant robotic crab walking around on that moon, with a artificial gravity ring inside of it;
http://www.buildtheenterprise.org/gravity-wheel
Then of course it could have double walls, with soil materials from the moon filling the gap, providing radiation protection.
Water? That's a question mark.
I have a special spacesuit notion that might also help, but later with that I think
I am sorry if I am getting all over everything just now. I keep planning to go away actually.
I am starting to ask seriously "Why do I do this?"
Offline
Zero G would certainly be a problem. According to the American Society for Gravitational and Space Biology, astronauts exposed to zero-G lose (on average) 1.5% bone tissue per month. For a 30 month mission, that works out as 45% bone mass loss - yikes!!!!
Exercise has so far failed to be effective as a counter measure, apparently because equipment used so far cannot simulate full 1g conditions. This raises the question as to how effective Martian gravity would be in preventing BMD loss. For initial missions, Vitamin D and drug therapy might be another option, which have proven effective at slowing BMD loss due to osteoporosis, but do not appear to have been tested in space.
Radiation is a smaller but still significant problem. If the surface of Phobos and the proximity of Mars filter out 60% of cosmic rays, total mission dose would still be 320-800mSv.
I wonder how simple it would be to produce a shielded rotating habitat on the Phobos surface?
Offline
Just me, but I think for having off Earth significant mass to deal with are; 1) Moon, 2) Mars, 3) Phobos and/or Demos, 4) Asteroid belt.
As silly as my post seemed, I actually was serious. I think a mobile giant robot of that sort, a mobile base would be the thing for a small body like that.
If it's legs kept it a few feet above the surface, then it's robitic arms/scoops could work with devices on the surface, and also scoop up mass into the base. Also teathered humans in suits could work underneith it, be protected from most of the radiation by being between the mobile base, and Phobos, and the get inside and have the artificial gravitation.
If the issue of water were solved, then you would have security for humans in space, mass accessible to make machines from, and a rather small gravity well to transport manufactured materials out of, to other locations in the solar system, including Mars.
I am starting to ask seriously "Why do I do this?"
Offline
To generate earth level gravity in a rotating structure require a radius of rotation of at least 20m to avoid orientation sickness. A 40m diameter spherical habitat, equipped with 3t/m2 shielding would mass perhaps 5500 tonnes, with 90% of the mass being crushed surface rock. It would weigh only 2.8 tonnes on Phobos. Four truck wheels could support it. Your idea would appear to be workable.
Offline
That's a nice add on. Wheels.
I especially like the mobile sheltering effects of a gap between the surface of phobos, and the mobile base above them.
They would be sheltered from radiation to a large extent.
Sheltered from micrometeorites to a large extent.
Be sheltered from temperature extremes to a large extent.
So the suits could be simplified to a degree.
With a tether, on board life support for the suits could be minimized, and a power line provide energy to a battery pack in the suit from the mobile base.
Also it would be likely that an airlock door to jump into if the suit malfunctions, would be in close proximity most of the time.
Also there could be overhead lighting for performing the work. It would be like having a giant garage under it where you could work on things. For instance while some parts of the surface could be a stip mine, other parts could be a strip of solar cells. The habatat would move over it slowly while it was being referbished or orignally built.
Last edited by Void (2014-10-03 10:27:35)
I am starting to ask seriously "Why do I do this?"
Offline
Why try landing it on Phobos? You'd be better of keeping it free of the moon, perhaps at the L1 point.
Use Phobos as a source of resources, mining it for rock and perhaps water to build a space station.
Though, I'm a Lunar-L1 first person. Well, actually I'm an orbit first person - I'd rather develop cheap (>$100/kg) launchers before attempting anything else...
Use what is abundant and build to last
Offline
The initial query was should Phobos come before Mars.
The surface of Phobos appears to be dry. Specualtion has it that there could be ice inside.
Any moving material from Phobos to another location would likely involve rocket engines which need fuel.
Putting the soil into a Bin, and transporting the bin would involve some diffaculty. For instance if you stand on it with a shovel, how well is that going to work?
However create a base on it of the structure that has been previously proposed. It is anchored by gravitation due to it's mass. It provides humans with Earth like protections inside, and and improved environment under it. Under the bottom where the four wheels could be.
If robotic arms would then dig soil, they would be attached to the bottom of the device and could do their work. Perhaps a clam shell type shovel on a robot arm.
If humans deploy outside under the device but above the surface of Phobos, actually perhaps they are attached to a robot arm, like the Canada arm, and also have electric, Oxygen, and so on consumbles supplied to them through flexible wires/hoses. Perhaps the CO2 can be recycled.
What might the humans be doing there since a robot arm makes more sense for digging?
They might be constructing a long array of solar cells. The base rolls forward. The arm digs dirt. The dirt is processed. Solar cells made, power busses made. The human goes outside in a suit on a boom, and assembles an extension of the solar cell array with power busses, so that the base can draw power from the solar array. Eventually Phobos is a big solar power supply.
It is possible that some of the dug dirt will give sufficient Hydrogen when heated to supply water for the humans. It is less likely that it would provide large amounts for fuels.
Eventually if the solar power system did become built, and there was ice inside of Phobos, it could be reached.
It's not a bad plan.
Easier to get to than Mars, but would likely make Mars accessible eventually, while allowing the search for life on Mars to continue while the infrastructure of Phobos was being built up.
Might be more bite sized than our Moon actually. Providing similar resources, while allowing it to be a base for scientific research of Mars. Also samples from Mars are there.
A convergence of space interests is possible with Phobos. Money, Science, protect Mars from contamination. Might be able to get some conllection of entities to go for it. Not so much for other schemes I think.
I am starting to ask seriously "Why do I do this?"
Offline
The question of whether there exists within Phobos any volatiles at all is completely unanswered.
Betting lives on the supposition that ice exists there, is therefore a bad idea, until better information becomes available. Period. What you have to assume for a first landing is that no volatiles at all exist within Phobos. Period.
In contrast, we know already that ice in one concentration or another exists within the dirt on Mars itself. That makes a direct surface landing on Mars a surer bet than a surface landing on Phobos first. Period.
But, even so, it's still a poor bet, even going to Mars first. What we found with the Mars Polar Lander was tiny lenses of ice buried under several inches of soil, not the massive deposits that would be so much easier to mine and utilize.
So, the first mission to the vicinity of Mars (including Phobos) can assume NO utilizable resources, until verified in situ, after the fact of a landing. That means, you must bring everything you need from Earth, period, on that first mission. No exceptions. Nothing else is ethical.
If you find something local that you can use, well, that's "gravy". But the odds are you won't! Period. Based on what we know so far.
GW
Last edited by GW Johnson (2014-10-03 16:03:12)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
Offline
Hey GW!
Yeah, I have argued a best case for Phobos because Antius asked about it.
If we were actually sending a mission somewhere, the moral issues would be very high at this point, but we are a long way from that.
I do not anticipate the utilization of ices of Phobos real or imagined for a crew living in a "Zadanga" type giant mobile pseudo robotic horseshoe crab robot on Phobos.
I expect that there could be some reachable soil that may have small chemically bonded materials of value. Otherwise the surface materials are rather reduced by spluttering from the solar wind I believe. That itself may not be a bad thing.
So speculating on this plan, you have to weigh if going to the Moon makes more sense for the human race or going to Mars, or this thing?
I do think this. There are supposedly four types of human power. Priests, Warloads, Aquisitioners, and Intellectuals. For my money I think people very often make a mistake on what an intellectual actually is. But that is just another funny issue.
Drawing the interest of the maximum amount of potential contributors may be the best plan. For the Moon, yes there is a logic, which would eventually get the human race out all over the solar system. However many of our population have the diligence of a 3 year old towards concepts of the betterment of the human race, or they actually want to feed off of the human race, don't particularly want it to advance at all.
The Moon as a starting point may be too abstract because all most people can see is a bunch of dry rocks with an unfriendly environment.
Mars? Some people do not want us to go to Mars. Some because they would rather we clean their windows or bring them a hot toddy (For very low wages, or no wages at all).
Some because they have a compulsive obsessive problem that they project onto Mars, supposing that humans are dirty and will contaminate it. (Actually not all together wrong).
Some see that there are alien cultures that want us to serve them hot toddies, and clean their windows for free, so they want military hardware to prevent that.
Mars is a hard nut technically but also socially.
But if you can have a method to utilize to inhabit small worlds that cannot possibly foster life, and you can deliver reduced materials (Metals, Silica) back to Earth orbit), you might please the vast majority of factions, except the ones who hate you no matter what because you did not really want to be their free dinner.
Mars does have deep deposits of ice. I guess not where pathfinder was as you have told me.
But here is the deal the imagination of some humans is on this pseudo star trek thing, with the artificial gravity. If you could adapt that to tiny worlds like Phobos, and indeed have a protected underside like a horseshoe crab, where materials could be processed as previously spoken (I do have a different spacesuit concept that will suit this thing very well I think). Then if it builds a solar array with significant wattage on Phobos, it can not only assist the push to Mars itself, but might indeed clone itself, and not only that make a saucer section (Artificial gravity) which could be hooked up to a propulsion device, a propulsion device that could move that clone to an asteroid.
So, this concept goes beyond Mars and to Mars. It is worth more time and words I think.
I am starting to ask seriously "Why do I do this?"
Offline
Mars has an atmosphere. It also has gravity. Those two things make Mars the safest place in the solar system, second only to the surface of Earth. The surface of Mars has half the radiation of ISS, no micrometeoroids, and I still contend the 38% gravity is sufficient to prevent the negative effects of microgravity. Of course that was supposed to be tested in the centrifuge module on ISS, but that module was cancelled. Using aerocapture to enter Mars orbit, and atmospheric entry/descent/landing, landing on the surface of Mars requires less fuel than landing on the surface of Earth's Moon. If you ignore that and use propulsive orbit insertion, then land on Phobos that has no atmosphere for landing, it requires more fuel than Earth's Moon. I contend gravity on Phobos is not sufficient to prevent microgravity effects on humans; again that was supposed to be tested in the centrifuge module. And no atmosphere means micrometeoroids, and radiation that is twice ISS. Radiation in Mars orbit was measured by the MARIE instrument on Odyssey, calculated for Mars surface, then surface radiation was confirmed by instruments on Curiosity. So Phobos is not easier than Mars, it's harder.
Last edited by RobertDyck (2014-10-04 08:49:32)
Offline
Phobos offers some advantage only if we can use low thrust ion engines for virtually all of the propulsive work there and back.
If that is the case, then Phobos may offer some advantages as a nearer term objective and a staging post for colonisation of Mars, i.e. excellent mass ratio. If it isn't, then Phobos offers no advantage.
The consensus here appears to be that a trip to Phobos presents other difficulties that a trip to Mars would not: (1) Increased surface radiation; (2) Increased microgravity health risks. Both are difficult to avoid without large scale engineering, which tends to undermine the advantage of a Phobos-First approach in the first place, i.e. that it could be done on a smaller budget, with less development, existing US launch vehicles, etc.
Offline
Well, at this point in our history, long distance manned spaceflight presents serious challenges to us, analogous to the challenges of transoceanic travel 500 years ago. It's difficult, but not impossible. Only flying cislunar is relatively easy for us at this time, because trip times are measured in days not years.
That being the case, if we decide that now is the time to send men to Mars, it will be very difficult to get them there and back again. We're looking at a round-trip journey around 2.5 years long. We will have to solve (at one level or another) the problems of artificial gravity and radiation protection for that crew. Period. Or they won't come home alive, most likely outcome.
So, if we go to all the trouble of doing that, why would we not visit both Phobos and the surface of Mars, and maybe even Deimos, while the crew is there? To go to all the trouble to cross that vast distance, and not actually "go ashore and explore", makes absolutely no sense at all to me! It violates the very oldest basic characteristic of our species and its ancestors: which is to explore.
To do all of that in one trip is going to require basing or staging out of orbit around Mars. No way around that, because you have to send lots of propellant to do the landings and the return home. That naturally leads you to an orbit-to-orbit manned transport, equipped separately (or integrally) with some sort of landers.
The velocity requirement to land on Mars from orbit (mostly aerobrake + terminal propulsive landing, skip the chute; then rocket back to orbit) is just about same as to visit Phobos from low Mars orbit. The same lander can do both. Visiting Deimos might need more propellant. But this could be done fairly easily once the lander and some propellant tanks are in Mars orbit.
Any orbit-to-orbit transport could (and probably should) be made reusable, so that it can be used for more than one mission. That way mission costs can be substantially reduced by spreading those costs around. The same ship can be used for Mars, asteroids, Venus, and even Mercury. (You wouldn't need landers at Venus or the asteroids, but a Mercury lander will be bigger than a Mars lander, being two-way rocket only).
If we don't save costs that way, it is likely no governments will ever sponsor such missions, not until we have new physics and new technologies decades (or more) in the future. Even so, it is likely that there will be one and only one government-funded exploration mission to Mars. Anything else will be done by visionary private entities (rare as they are). Most of the world's governments, including ours, have proven rather feckless over the last 4 decades as regards manned spaceflight. We've even backslid away from being able to reach the moon with men. (That’s what Orion and SLS are really for: the moon, not Mars or asteroids. I think most of us know that.)
Similarly, the lander ought the rigged as reusable and one-stage, again, to save costs and spread them around. That way, the same machines can be used many times to make landings all over the planet. No two sites anywhere on Earth are the same, it'll be the same outcome on Mars. We need to explore and try out our first-attempts at living off local resources at many sites, before we decide what can and cannot be done. Again, if you go to all the trouble to make the trip, why make just one landing? Seems kinda stupid to me. Landers like that are simply inherently larger than most minimalist designs I see proposed. But, they can do so much more than minimalist designs!
That kind of mission is thus simply not a minimalist mission design; in point of fact, it cannot be! This is not (and can never be) something you shoot straight to Mars with one or two giant rockets. This is something you must assemble by docking in Earth orbit, and, you recover it there after every mission it does fly. Because it's assembled from smaller modules in orbit, in point of fact, you don't really need a giant rocket. The ones we have already fling stuff big enough to do this job.
There's two kinds of radiation to worry about: galactic cosmic rays, and bursts from the sun. The former are a slow drizzle of stuff so energetic that we cannot shield very effectively against it (the real trouble being the secondary shower effect unless the shield is too thin to do much good anyway). Just being in Mars orbit cuts the dose in half, because the planet fills half the sky. And exposures down on the surface are much lower still.
But, the dose from a 2.5 year mission spent all out in space will fall pretty much within the annual and career-limit criteria we currently use for astronauts. That takes care of cosmic rays on an exploration mission. It’s just that the crew who does this cannot ever fly outside the Van Allen belts again.
The solar flare stuff is erratic in occurrence, and variable in its lethality, but we know it can be as deadly as nuclear war fallout (death by radiation poisoning within a few hours, worst case). It turns out that 20 cm of water is an effective shield for this stuff, and is practical for a big ship design (but not for most minimalist concepts).
Sending men on a two-way trip is simply-and-inherently a whole 'nother ballpark from sending one-way probes. But it can be done, and right now. I just think that expecting the vehicles and mission design to look like the minimalist designs we use to send the probes is just plain wrong. If it's worth doing at all, it is worth doing right.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
Offline
I have a deep respect for all your opinions. If we were in power and had to make a choice now for a mission now. I would step back and not argue with you at all.
But it is a characteristic of "Advanced" animals/humans to play. So, I am playing.
http://www.universetoday.com/114871/mak … on-phobos/
They make an argument that NASA is sort of heading in such a direction anyway. I share your views that this might not have been the correct path, but it is the investment they have made. If possible, it would be good to utilize what they can provide (If it helps).
Phobos may be hydrated down deeper, but the surface is not so at all. As Antius has said, there is likely ejected materials from Mars mixed in with the surface of Phobos.
I state that I think that Phobos should have at least one unpersoned probe go to it before a human mission. If such a probe can reasonably determine it's probable potential and it is a negative report then Phobos can be eliminated completely from the competition. If samples can be returned then some information from Mars would also be gained I think.
If somehow there would be a positive report, then it is not unreasonable to ask if Phobos can be considered as part of a plan.
There are four reasonable contenders for human expansion into space I think. One has to exist, that is Earth to orbit, which we have and it seems SpaceX might make better.
Subsidiary plans are Moon and/or small asteroid capture to Earth orbit, Mars, Phobos and/or Demos.
NASA is not going to the Moon in any significant way, but says it will try to capture a small rock and visit it with humans. Some companies say they want to do similar,but perhaps with automation.
Japan wants to go to the Moon it seems, or at least someone in Japan wants that.
Many of us would like to see an experiment with a centrifuge in orbit on animals and humans. I suggest Mars level gravitation.
The some want to make a pseudo Star Treck Enterprise ship with a centrifuge process.
Some want to go to the Asteroid belt, and some want to establish a presence on Mars, or at least have humans visit it.
Some do not want humans to set foot on Mars for contamination reasons.
Some who it does not profit to work with simply want the human race stay here and serve them as servants.
Some who want to find life on Mars are simply interested, some want to dispute the foundations of religion. (Part of their plan to be god and be served I think).
Various pressures exist most of them favor some kind of expansion into space. Some will achieve some of these things regardless of what we want or do. So it is perhaps worth considering if most of these desires can be connected into a greater plan that most might accept.
If someone goes to Mars, fine. But until then, I suggest thinking about the possibility of a centrifuge device that would work in both microgravity and on the surface of small objects such as Phobos or a small asteroid.
I suggest low Earth orbit, the saucer plan from the Trekkies @ .38 gee.
Perhaps Space X can lower prices, or perhaps small asteroids are captured by then. Or maybe Japan or others are on the Moon by then. Resources to build it from that?
You want the data for centrifuges anyway for humans. And you also want to confirm that Mars gravity is enough anyway.
If Phobos is a valuable resource, and if the saucer technology is done in low Earth orbit, then how would you get it to Phobos? It has been suggested ion thrusters, which makes sense. However if it is saucer shaped can you also consider aerocapture to Mars orbit to help?
If the saucer were on the Mars facing side of Phobos, it would already have some radiation protection from two directions. In the beginning of habitation small storm shelters could be lined with soil from the outside to supplement this. Later the whole top surface could be protected in a similar fashion, and of course Phobos would offer protection to the underside.
Then there is the question of EVA's. A suit designed to be autonomous with it's own resources, is quite a challenge. I prefer a tethered approach.
The saucer in low Earth orbit would allow this and would allow resources from small captured asteroids or the Moon or from Earth to be manipulated. Mostly all of this is upside. However there would be a potential for an increase of crushing crushing events, but safety measures should be able to address those dangers.
Similarly, the underside of such a saucer on Phobos would provide a sheltered and tethered EVA potential.
Manipulation of materials could be done by robot arms, and suited humans and a combination of both.
I suggest that a long term suit be contemplated, that a person could be in for perhaps a week at a time. This would be a box on a manipulator arm, with some emergency supplies in the case where the tethered resource supplies (Hoses wires) failed.
I suggest a combination arm method where at the upper arms would be a triple seal. A simple representation of that would be you are in a bag suit, but your arms are in counterpressure apparatus. Around the transition point on the upper arms you have a cork stopper (This is for visualization only, I would expect something much more sophisticated).
Your long term suit is a box on a robot arm, it has ports for the arms that the "Corks" can be pushed into for a seal. So your arms (Or I prefer your best arm only) are outside of the box. But this is not so stupid if you also put a bag suit for the arms on the outside also joined. So your arms are in a pressurized bag suit and also inside of counterpressure suiting for the arm. Then unfortunately your circulation will be cut off if you don't depressurize the arm bags. So you do depressurize them You pump the air from these arm bags into the box you are in. Now you have your counterpressure protected arms in a vacuum.
There is an inconvenience involved, certainly you now have both the counterpressure arm covering and the depressurized bags around the arms, to impede your sense of touch and your grip. But you are not fighting to clench your hands against the pressure of a bag suit. During work with your arm(s) deployed, you are in the bag suit protected by it, and you are also having your arms protected by the counterpressure measures. You are also protected by the box and the bag arm/gloves. So you have double pressure protection.
Arm retraction:
In an emergency it might be possible to pull the cork out pull your arm into the box, if the cork were designed well. Then you would have to hope the arm/bag did not burst from sudden pressurization. However the ports that you put your arm through could also have hinged spring loaded doors that would shut. I even if the box depressurized, you would still be in your hybrid bag suit and it might keep you alive.
But for normal arm retraction you would simply repressurize the arm bags, and pull your arm(s) out, and the port doors would spring shut. (The arm/glove bags should still protect the pressurization of the box even if the doors fail.
So, you have retracted because you want to eat something or preform a body function, or go to sleep or you don't have a useful task to preform "Outside". Before you compromise your hybrid suit, you latch the port doors down.
Then you are inside, but unless you doff your arm counterpressure part of the suit pretty soon your circulation will be cut off. So you have one or two vacuum chambers that you can insert one or more of your arms into (Inside of the box), on a periodic basis, you do your body function, or eat, or take a break or you take your whole suit off for the night and get some sleep until the next work period.
And that is I think how humans could make it in such environments, and do useful work and have significant protection from harm. Obviously after a week the person should be rotated back to the saucer and do centrifuge therapy.
I think I did OK
Last edited by Void (2014-10-04 11:32:46)
I am starting to ask seriously "Why do I do this?"
Offline
I suppose I could add a few things.
You could take you bag glove off and then touch things with just your counterpressure protected fingers. That will reduce the amount of safety.
I also favor various configurations. Usually people use one hand to grip and object and another to work tools and parts.
So, I actually think the best mode would be to have only one arm out, and to have the other inside manipulating a mechanical arm. That may or my not involve electric power. It could be strictly mechanical with the inside arm manipulating a mechanical gripper arm outside. This then leaves the person free to do keyboarding on the inside, and to perhaps eat, and if needed attend to body functions, even though that will be a bit hard.
You could also have three arms or four. A mechanical vice arm. A voice operated motorized arm. 1 or two actual protected human arms projecting outside.
And I did actually think this thing up with Mars itself in mind. However the gravity field of Mars being much stronger, it will be harder to do.
Another feature is that if for some reason you wanted to pressurize the box with outside gasses on Mars, you could the person would be in a suit. This would add significant danger, and would make eating a problem, but a well designed suit might allow you to drop them and do #1 or #2 even in that case. I don't know why you would want to do it except then the box is a airlock, you are already in your suit with oxygen, you can just unhook, and depressurize the box, open a single door, and go outside if there is a reason.
So, it could have many modes of operation.
For one thing I think it could be good for constructing solar panel arrays, since for it to operate you would have to have a cart with a lift anyway.
It could also be good for installing and repairing pipelines on the ground, and power lines which might also be on the ground.
It would reduce slip and fall injuries, and would allow EVA's to be longer with some added comfort and reduced use of airlocks on your main hab.
But the potential for crush injuries would be a safety issue that would have the be well though out.
How do you rescue a person who has had their projecting arm crushed? How do you prevent it from happening at all?
I am starting to ask seriously "Why do I do this?"
Offline
There was, is, and will always be, a big difference between what should be done sending men into space, and what will actually get done. What gets done will fall short of what should have been done in many, many ways. It always has. It always will. My epistle above is just something that voices what should be done. How this actually gets done, will be different. And not as effective.
As for the spacesuits, I vote straight MCP suits. Except not the way NASA sometimes dribble-funds Dava Newman at MIT. They (NASA) are caught up with the "everything garment" concept: that the suit is a miniature spaceship that protects its wearer from every conceivable risk, all in the one garment design. That's just wrong, and it's why a shuttle suit was 300+ pounds, almost immobilizing to its wearers, and its stiff gloves ripped off astronauts' fingernails quite frequently.
The "right" way to do MCP pivots off the work of Paul Webb in the 1960's, but done with Dava Newman's modern tailorable-property materials. This right idea is nothing but vacuum-protective underwear (!!!!) with an O2 helmet for minimal-pressure breathing (around 0.15 to 0.20 atm, not NASA'a arbitrary 0.33 atm overkill requirement). Over that, one wears only whatever conventional earthly garments one needs for protection from heat, cold, or mechanical injury. For cooling, you just sweat right through the porous elastic underwear garment into vacuum. No airconditioner or moisture control is needed.
Further, with MCP, a rip in the suit is not fatal. You have perhaps 30 minutes to get inside, or to tape up the rip tightly with a vacuum-qualified duct tape and continue working. Sew up the rip later, after you do go inside. With the current full pressure suit approach, if there's any leak, you must get inside within the seconds it takes your suit to depressurize, otherwise, you die. Period.
MCP's ONLY vulnerability is a cracked O2 helmet. That's no change from a full-pressure suit. In every other way, MCP is VERY far superior! Only tradition is holding this back. The tradition of not doing anything different from "what we did before". And even that tradition is false: MCP sort-of worked as the primitive partial pressure suits worn by high-performance jet pilots in the late 1940's, throughout the 1950's, up to about 1960. What Paul Webb did in the late 1960's was better, but never used.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
Offline
These are a few things among many that I have posted about previously. This stuff is located at http://exrocketman.blogspot.com. On the left side of that page is a navigation tool that works by year, then month, then title.
My qualifications for knowing about these things are two degrees in aerospace engineering obtained long ago before I entered industry for two decades in aerospace weapons development work, plus a much more recent PhD in general engineering, plus about 2 more decades in civilian work and in teaching. My papers presented at Mars Society conventions have always startled the audiences that heard them, and have always received positive feedback.
Advanced spacesuits and advanced on-orbit assembly capabilities:
“On-Orbit Repair and Assembly Facility” 2-11-14
“Fundamental Design Criteria for Alternative Spacesuit Approaches” 1-21-11
“End of an Era Need Not Be End of a Capability” 8-2-11
Radiation and Microgravity Solutions:
“Space Travel Radiation Risks” 5-2-12
“Space Recommendations” 4-17-10
Colonization-level Propulsion and ship design:
“About Old Project Orion – the Nuclear Explosion Drive” 3-10-10
Living “off the land” on Mars:
““Icecrete”, a Substitute for Concrete as a Building Material on Other (Colder) Worlds” 3-11-12
“Aquaculture Habitat Lake for Mars” 3-18-12
“Pressurizable Domed Habitat Structures” 6-9-12
“Aboveground Mars Houses” 1-26-13
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
Offline
Well I appreciate your reply and am intimidated also. (By your credentials) I had to read twice. It seemed that you were a bit harsh at first which is uncharacteristic of you, but on the second reading I was more comfortable.
I agree that for Mars the points you have made are very strong. MCP suits would be a very good choice for early and later generalized work.
But I will argue my case for using what I proposed on worlds that are not as Earth like as Mars first, and then I will try to make a weaker case for the use of it on Mars.
As for evaporation cooling on dry worlds, that would be something to want to avoid I think.
For instance the Moon. Although you could get water from the poles, or perhaps in some other way, you would not want to squander it, except for special cases where what I propose as a suit simply will not do.
I agree I don't like the classic bag suits.
I would not actually like to begin the use of what I propose on either the Moon or Mars, because of gravitation, and the fact that such a device would be heavy, requiring strong motors to manipulate. Balance beam concepts would reduce the amount of lifting force required however, if possible to implement.
I do like it to begin with on the international space station, or a small world like Phobos. It largely allows the recycling of consumables.
If you see space walks with bag suits on the in Earth obit, they are for limited duration, are dangerous, and require a large degree of autonomous life support.
But we do see people in bag suits, attached to robotic arms doing tasks.
And without MCP suits, I guess it still makes better sense than what I propose because most of the tasks are one of a kind with scientific equipment. I am not saying that some of it could not be done with what I propose, but not enough of it can be yet.
Supposing it were developed (Existed) and you wanted to set up some kind of a materials processing facility at a location in a vacuum environment. Perhaps Moon or asteroid materials in a "L" location. You have a choice of bringing the materials into a large pressurized "Factory" or having a open vacuum factory.
If on the outside of your factory you had "Capsules" anchored on rails or robotic arms, then you can present the capsule to a work point. The human then uses whatever arms he/she has to manipulate a object to achieve a purpose. The capsule has far more consumable resources available than a person in a space suit. For instance they have electrical power from the mother object. They may have a Oxygen line in some cases, or be able to refill at certain locations. As for heat, a larger object will suffer less severe consequences than a person in a suit from thermal variations. Also having electrical power in relative abundance, the capsule could be heated by it when cold. Otherwise it could be quite reflective so as not to heat up too much in the sunlight.
CO2 could be recaptured and returned to the mother object for reprocessing.
Such an environment might be suitable for trying the method. Radiation will be a problem. But suppose the capsule weremade of Aluminum, and lined with Paraffin wax? That might help, and there could also be provision for a shielded garage which may or may not be practical. A person in a autonomous space suit would be even more at risk however they might resort to a garage and airlock escape from radiation storms, but would not have all that much protection from typical radiation.
Impacting objects could be an issue. If someone is in a suit, I think chances are they are dead in such an event, but perhaps this is also a case where the MCP suit gives a better chance of survival than a bag suit. A capsule offers a possible improvement however for that problem.
Phobos/Demos:
This thread is about Phobos though, and so I will stop there next. I saw an opportunity to find a better environment on tiny worlds for this, and Phobos or Demos seem to be the most local of opportunities.
There is the question of resources. The moons may not be suitable if they are truly lacking of critical ones. Then it would be necessary to go to the asteroid belt to do this thing. That seem unattainable at this point without first establishing a starting point nearer to Earth. But the future belongs to the people who will be there. It will almost certainly be different from what we have now.
Anyway, for a world like Phobos, the mother device would be mobile on the surface of the object, and would have child devices "Capsules" below it.
They also would draw electrical power from the mother device, and would very likely have hoses supplying Oxygen from it and have a return line for CO2.
Being below the mother device, they would be in a modified environment. It would have significant protection from radiation, be more thermally constant, and have the possibility of overhead lighting from the mother ship, so they would not be dependent on sunlight for vision. If reasonable, additional protection could be added by placing flexible stips of skirting around the perimeter of the mother device almost down to the ground level. But that would be a preferred add on, not a necessity.
Presuming that the mother device could gather soil and rocks, and could convert those into useful objects, the people in the capsules could assemble those components into a larger structure on Phobos, perhaps a strip of solar panels with two or more power buses. The task would be redundant. The mother device moving forward at a very slow speed could extract power from the power buses for the whole operation. There would be a large degree of protection from impacting objects.
The Capsule/Suit:
I feel that I may need to explain better what I am saying when I say the person in the capsule would be in a bag suit. The part of the body and head inside of the capsule would perhaps be inside of a minimal suit. It would not normally be pressurized relative to the pressure of the capsule, and would be cooled by a air pump/cooling fan if needed exchanging air between the suit and the capsule. In fact, if desired the heaters in the capsule would be turned off to make the interior cool/cold, and the bag suit might serve to keep the person more comfortably warm.
Check valves would protect the human from sudden decompression of the capsule. (If maintained properly).
As for the arm projected outside of an arm port, that arm/glove bag would only be pressurized during the insertion of the arm or the extraction of the arm. When the arm was pulled back into the capsule, the arm port door could be closed, but the arm/glove bag would add protection from capsule decompression if the port door did not seal properly.
To insert, first the suit is put on, emergency bag suit and helmet for the most of the body, and MCP method for the arm. After checking that the glove had maintained pressure properly, the port door would be opened. If depressurization happened at this point from a glove failure, the person is already in a full emergency suit that should allow them to survive the event. The arm is inserted, and a fixture on the upper arm docks with the port opening sealing it. Then the arm/glove has the air pumped out of it and into the capsule. The person may be able to put both arms out, and then after the depressurization of the arm/glove, may take off the glove(s).
My preference however would be to put one dominant arm out, and for the other arm have a hard arm that the other arm could be inserted into, that having a mechanical method for the hand and arm to open and close a exterior mechanical hand, perhaps as simple as a clamp, or perhaps more sophisticated. It would be modeled off of very deep sea diving suits.
The intent would be to use that hand to hold objects to be worked on by the other hand. Most people are right handed, so in many cases the arm/glove hand would be the right hand, and the hard suit arm would be the left one. It would be desired that the person could extract their left hand and arm from that apparatus at any time desired.
They could operate a keyboard. They also may be able to eliminate waste without extracting the right arm from the process, but that would be tricky business. With other suits you just have to go in your pants. However it would not be that much of a problem to remove the right arm from the Arm/bag suit, if you had to go #2. I presume that #1 can be handled that way or perhaps with some type of elaborate duct work device. I would like to suppose the person would extract both of their arms every two hours, and take care of eating, and eliminating waste, and then go back to work. A coffee break so to speak.
The MPC arm may or may not get too uncomfortable under air pressurization, so I have suggested a small vacuum chamber in the capsule to relieve that problem as desired.
It would be tied to the system that pulls the air out of the arm/glove device. Neither one would be intended to be vented to space vacuum.
Mars:
I did mention Mars briefly, said that it is what I originally thought this up for. It has less potential there, other solutions may often be better.
However I will make a special case for working on a pipeline or even more a power line. Those being on the ground, would allow this to be rather simple. You would be in a wheeled mobile device, and your arm ports would be on the bottom within reach of the ground (That's easy to say). It would likely need some type of elevation control at least for rough ground. It could roll up to the habitat when it's tour of duty was done, and could dock with it and allow the person to be extracted into the habitat. Or the person might be able to use the emergency pressure suit to make the exchange, but that would be for "emergencies".
On Mars the mother device and child device method will be less successful You could have a large cart with large solar arrays on it, but then it would make things more clumsy.
I do offer an improvement over other methods for the case of chemical contamination. I do know that for the MCP suit coveralls are proposed to help control that problem.
But if the person in this apparatus is never actually outside and had not either taken of their glove to touch objects, and if a successful docking to the habitat without resort to the emergency suit method was done, then the contamination problem would be very low. Granted, the air lock might have some residue on it,
Anyway, presuming you have actually read this very long reply, I have nothing but good intentions in doing this. Not trying to rock the boat.
I do understand that what will actually be done is much less than what could be done, but there are far more fantastic ideas floating around this site I think.
But maybe it is an honor to even be noticed
Last edited by Void (2014-10-05 22:53:10)
I am starting to ask seriously "Why do I do this?"
Offline
Hi Void:
Believe it or not, something sort-of similar to your capsule-suit idea was proposed in the mid 1950's, before there was a NASA. Take a look sometime at the old Disney "Tomorrowland" series about going into space. The EVA "suits" were powered capsules, with external manipulators operated from inside the capsule, which was a shirtsleeve environment. That's actually quite similar to your idea, and the manipulator arms presage the shuttle's manipulator arm.
Actually, I think something like that is a very good idea, particularly for construction operations like operating heavy machinery. A capsule suit becomes the operator's cabin on a bulldozer, etc. I do think there are other necessary activities that require a human protected against vacuum, but employing his fine motor skills. Such tasks would include things like fine wiring, small plumbing, and small nuts-and-bolts work. That'll never happen with a gas balloon suit.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
Offline
I do believe it, I am sure I was exposed to the concept as a child.
The whole idea has no element without presidence. I did think at one point that I had created the idea of poking the arm out into a alien environment, but then later remembered that I had been previously exposed to this:
http://en.wikipedia.org/wiki/John_Lethbridge
He did not have the technology that we do or I suppose he might have been able to do it better.
His challenge was actually worse though because the low pressure was to be in the capsule, and having higher pressure outside the barrel, caused his circulation to be cut off in his arms. He almost died several times. with the device, but made it work. But it was so long ago!
Anyway, one add on I think I could propose is that the arm ports should be put into a flanged part that would fix on the wall of the capsule.
The arm fixture that plugs into the port might stick at some time (although I would hope that it could be made better so that it does not). But Murphy's law being what it is, it needs to be possible to depressurize the capsule and undo the flange from the wall, if it did.
I would hate to think of someone stuck somehow in that fashion in the machine without a method of extraction except a cutting torch.
I am glad you see some utility for the methods.
Last edited by Void (2014-10-07 06:58:29)
I am starting to ask seriously "Why do I do this?"
Offline
One thing I think the device could be useful for early and perhaps aid in a push to Mars would be an Earth/Moon local factory utilizing captured small asteroids, which is what NASA is intending to demonstrate, and some space companies are proposing to do as well.
I have for quite a time been in favor of a small shell world, even before I was aware of other thinking on shell worlds. Those ideas are currently very well out of reach for actually doing, but this one is not so unrealistic.
I intend for a metal shell world, not a very thick wall either.
It is to serve several useful purposes.
It can hold solid objects that are manipulators, and solid objects that are to be manipulated.
It can hold devices like the Parent/Child devices we have spoken of, the third kind of spacesuit.
It will protect them from drifting away. Nuts, bolts, tools, etc.
It is also a micrometeorite protection.
You can mount solar cell panels on the outside of it.
You can have a door on it so you can bring small asteroids into it.
You might have several chambers. For instance if it were a cylinder, you could partition off each end, and have a baton type centrifuge such as you champion GWJohnson, one on each end. That device if designed to simulate .38 Gee maximum, would test human adaptation to that, and on it's smaller radius floors, simulations of gravitation for various smaller solar system objects could occur. And of course having a prototype would allow the bugs to be worked out for when it was used for an actual mission to Mars.
Ideally all the shell chambers could hold molecular pressure, but not viscous pressurization. Every air locks leaks, and various industrial processes will shed volatile substances. If you hold them in the shell, then you can try to build a collector, and recycle them. For my part I would attempt to use a bottle with a high static electric charge inside of it relative to the rest of the place. The intention is that will cause molecules to collect upon it's outer surface. Then I would try to use a piezoelectric pump to compress that skin of collected molecules into a pipette. Applying an electric force onto the crystal to make it oscillate making a plunger like situation which could push that skin of molecules into a funnel. Very tiny.
Lets call end chambers 1 & 2. And then there would be an middle large chamber to this shell world. You could put a double wall in place in certain places, perhaps you would not do that where the large door would be that you bring small space rocks (Asteroids) into, but otherwise you would have a double wall. The purpose is so that you can pinion the child devices, this 3rd type of space suit between walls. You could then electrify one wall as negative and positive, one each. Then you have a power buss, and can place machines into the gap between walls, and this would be your factory floor. Then you could actually have spacesuit type 3 (With the arm ports), in this location as well, to navigate through hallways between machines. Then you could have tires, that contact each wall, hold the device steady, power the suit, and propel the suit to locations where the human augmented arms can manipulate machinery. In this case, I could recommend a disk shaped suit as one option but there would be many other configurations. The suit should be able to move in any direction within the space between the two walls, and should be able to spin on their axis, providing quite a lot of ability to reach valves, junction boxes, ovens, pressure vessels, robotic arms, and other devices.
If this option was done. Then why can't you also do it at Mars?
But you would not have to before you set up a colony on Mars. The financial output from a factory such as this might pay for most of the development costs, for devices which could also be quite a bit of what is needed for hardware to access Mars, and to provide propellant.
From such a Shell world factory could come the projection of humans to various places in the solar system, including the Moon after a while. Mars of course, and since Phobos is the theme of this thread, I will mention it as well.
Last edited by Void (2014-10-07 08:05:42)
I am starting to ask seriously "Why do I do this?"
Offline
One thing I think the device could be useful for early and perhaps aid in a push to Mars would be an Earth/Moon local factory utilizing captured small asteroids, which is what NASA is intending to demonstrate, and some space companies are proposing to do as well.
I have for quite a time been in favor of a small shell world, even before I was aware of other thinking on shell worlds. Those ideas are currently very well out of reach for actually doing, but this one is not so unrealistic.
I intend for a metal shell world, not a very thick wall either.
It is to serve several useful purposes.
It can hold solid objects that are manipulators, and solid objects that are to be manipulated.
It can hold devices like the Parent/Child devices we have spoken of, the third kind of spacesuit.
It will protect them from drifting away. Nuts, bolts, tools, etc.
It is also a micrometeorite protection.
You can mount solar cell panels on the outside of it.
You can have a door on it so you can bring small asteroids into it.
You might have several chambers. For instance if it were a cylinder, you could partition off each end, and have a baton type centrifuge such as you champion GWJohnson, one on each end. That device if designed to simulate .38 Gee maximum, would test human adaptation to that, and on it's smaller radius floors, simulations of gravitation for various smaller solar system objects could occur. And of course having a prototype would allow the bugs to be worked out for when it was used for an actual mission to Mars.
Ideally all the shell chambers could hold molecular pressure, but not viscous pressurization. Every air locks leaks, and various industrial processes will shed volatile substances. If you hold them in the shell, then you can try to build a collector, and recycle them. For my part I would attempt to use a bottle with a high static electric charge inside of it relative to the rest of the place. The intention is that will cause molecules to collect upon it's outer surface. Then I would try to use a piezoelectric pump to compress that skin of collected molecules into a pipette. Applying an electric force onto the crystal to make it oscillate making a plunger like situation which could push that skin of molecules into a funnel. Very tiny.
Lets call end chambers 1 & 2. And then there would be an middle large chamber to this shell world. You could put a double wall in place in certain places, perhaps you would not do that where the large door would be that you bring small space rocks (Asteroids) into, but otherwise you would have a double wall. The purpose is so that you can pinion the child devices, this 3rd type of space suit between walls. You could then electrify one wall as negative and positive, one each. Then you have a power buss, and can place machines into the gap between walls, and this would be your factory floor. Then you could actually have spacesuit type 3 (With the arm ports), in this location as well, to navigate through hallways between machines. Then you could have tires, that contact each wall, hold the device steady, power the suit, and propel the suit to locations where the human augmented arms can manipulate machinery. In this case, I could recommend a disk shaped suit as one option but there would be many other configurations. The suit should be able to move in any direction within the space between the two walls, and should be able to spin on their axis, providing quite a lot of ability to reach valves, junction boxes, ovens, pressure vessels, robotic arms, and other devices.
If this option was done. Then why can't you also do it at Mars?
But you would not have to before you set up a colony on Mars. The financial output from a factory such as this might pay for most of the development costs, for devices which could also be quite a bit of what is needed for hardware to access Mars, and to provide propellant.
From such a Shell world factory could come the projection of humans to various places in the solar system, including the Moon after a while. Mars of course, and since Phobos is the theme of this thread, I will mention it as well.
Maybe a pre-stressed structure, made from microwave sintered blocks of asteroid or lunar material. These could be locked together and stressed using iron long bolts, made from carbon monoxide reduced iron oxide or pure asteroid iron, or alternatively, cast basalt fibres.
A spherical habitat could be constructed from uniform hexagonal blocks. If each block were 1m thick, it would also provide sufficient shielding against cosmic rays and micrometeorites. The pre-stressing bolts or fibres could be placed on the inside, so that they could be replaced without going into vacuum.
If the first shell were 400m in diameter and internal pressure was 30KPa, the stress within the shell would be 3MPa. If the blocks have the same compressive strength as ordinary concrete, that would give a safety factor of 10. Mild steel has yield strength of 250MPa, so using four bolts per metre with cross section of 0.012m2 each (12cm diameter), would give a safety factor of 4. Cast basalt tiles have a tensile strength of 36MPa, so a safety factor of 3 would require that they form 25% of the cross section of the block in each direction, but still doable.
If sintering takes place at 1000°C and the heat capacity of surface rock is 1KJ/KgK and density is 2200kg/m3, then the energy cost of 1m3 of sintered block (starting at 250K) is 1.65GJ. The energy cost of the entire 400m diameter sphere is 829,300GJ. If sintering takes place over 5 years, and the microwave oven is 60% efficient including heat losses, then the total power required would be 8.75MW. This is a modest amount of power, easily provided by a small nuclear reactor.
The quantity of iron required would be roughly 10% of the block volume, some 50,000m3 or 400,000 tonnes. If the iron is present in the form of reduced asteroid iron, this might be achievable. But sintered fibres would probably be more cost effective.
Offline
I have been trying to estimate the amount of Radiation shielding that can be achieved on the surface of Phobos, specifically in the bottom of Limtoc crater (inside Stickney).
I believe it may in fact end up being the best radiation shelter in the whole Mars system because Mars itself fills so much of the 'sky' above, their are virtually no un-impeded lines out to deep space. Limtoc crater is 2 km across and from images looks to be quite deep and cone shaped, and it points almost directly at Mars continuously because of Phobos tidal-locking. As you can see in this photo which is taken strait 'up' from low Mars orbit.
http://upload.wikimedia.org/wikipedia/c … Phobos.jpg
Stickney is rather shallow and dose not point directly at Mars, but Limtoc is slightly skewed and in the rim wall of Stickney and points more squarely at Mars. To determine the shielding we need to know the rough conic 'sky' angle out of Limtoc, the angular size of Mars from Phobos, and the degree of alignment between the two cones. Then we can compute the approximate amount of unshielded sky and the GCR dosage over time.
My very rough conservative estimate of Limtoc conic sky would be a 140-120 degree cone, or in other words the crater rim is 20-30 degrees above the horizon and reduces the sky by a modest amount. Mars in the sky from Phobos is 40 degrees. And for alignment I'd again guess that about 30 degrees off from being pointed directly at Mars, this would mean that the rim dose not block any of Mars and the open sky is just the simple subtraction of the two areas. I don't know how to do the calculation to subtract the conic intersections and derive a % of the remaining hemisphere that is exposed which would then tell us the % of GCR dosage vs open space or vs Mars surface.
Offline