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Thanks GW
Sounds like you are talking about using the lander as the manned transit vehicle. From a dead-head return propellant standpoint, Apollo showed it is better not to land the return vehicle (hardware and/or propellant). Just take down the minimum landing vehicle and surface stay supplies and equipment. I think the habitat required for a surface stay of weeks is different from the transit habitat for years in space.
My vehicle will get all the water propellant for the return trip melting a surface ice pack on Mars, so I have imagined to land on Mars the whole spaceship, but I'm only an SF writer not an engenier like you, so I dont know if it's a good idea.
From a radiation shielding standpoint, there is merit to your sideways cylinder geometry with the nuke in the middle. Depends upon the numbers whether the surface crew could stay in the vehicle cabin while on the surface. In the vertical geometry I looked at, they could not. How big a surface habitat is needed depends upon both crew size and length of stay. Different mission plans have different surface stay requirements of the landers. Cannot generalize.
GW
I have no idea how much the ship has to be long for radiation shielding.
I'm not sure there is a way to get effective shielding in a nuclear lander, because it needs to be short and squat for landing stability on rough ground. If it were a long slender shape, the propellant and tankage structure actually maker a pretty good shield. Trouble is, things like that tip over way too easily upon landing.
GW
Is it possible to directly project the lander as a long slender body, with the habitat at one extremity; the ISRU and the rover bay on the other; and the water tank and the NTR in the middle, perpendicular to the long axis?
Such a vehicle will land on the thermal protected belly and take off in the same way, with the central NTR, balanced by ballast water tanks and chemical rockets on the two extremity.
Douring the transfet, the slender body will tumble for artificial gravity.
At the moment, the only place where where we are certain of the presence of water, exept polar caps, is the Ice Lake Crater: we can send a probe to test the salinity and the acidity.
In the worst case we cannot find water in equatorial latitude, we can land the first mission near the ice lake and use it for ISPP. Douring the winter, astronaut may moove sauth with the rover and explore other site.
But, in this work ( http://www.nature.com/nature/journal/v4 … 03379.html ) planetologists suggest the existence of a 800x900 km x 42 m surface ice pack in western Elysium (5° N 150° E).
It would not be difficoult for an unmanned probe to verify the claims, drilling for 1-5 meters and test the salinity and the acidity of the water.
Rather than make the colony mobile, if we do end up needing to get ice from vastitas borealis, wouldn't it make sense to have a small base up there with a rotating crew to oversee mining and transport operations, and send the ice straight south a couple tonnes at a time?
It may be a good option: a little tank truck to bring the ice to ice lake to the base in Elyisium Planetia that is almost 3300 km south.
Where should the first permanent human base/settlement be located? My criteria:
flat and smooth -- to enable safe landing
low altitude, at least below datum, ideally -2km -- more atmosphere provides greater protection from heavy ion Galactic Cosmic Radiation
close to equator, at least between northern and southern tropic, ±25.19° -- relatively warm, no winter
identified source of water (ice)
other resources
interesting science
One potential location is the "Frozen Sea" also known as "Pack Ice" in Elysium Planitia. The ESA team reported this in 2005. Analysis of image data showed it's 900km x 800km and an average of 45m deep. However, that's the result of studing "sploosh" craters and layered deposits. It's apparent this was formed by water, and was pack ice at one time. The feature appears to have been formed no more than 5 million years ago. However, there remains a question whether water ice still remains.
If we will find ice, Elysium Planetia may be the best site (is it possible to send a Red Dragon in Elyseum Planitia with the hardware to drill 45 m deep to verify the presence of ice?)
If there is no water ice in equatorial latitude, we can imagine some form of migrating colony: a fleet of wheeled habitats that stay in Vastits Borealis Crater in spring and summer and migrate south in autumn with a water reserve for the winter.
This in the first times. When the colony will grow, we can imagine a pressurized dome around Vastitas Borealis crater, warmed via greenhouse effect douring the winter, with the ice lake partially melted that act like an heat sink, tempereting climate.
Hi Quaoar:
Nope, my design is an old-fashioned "do-it-the-hard-way" design. I used propulsive burns for capture at Mars, precisely because we have not done aerocapture with men anywhere but Earth (coming back from the moon). Our atmosphere is very predictable at entry altitudes (140 km on down to around 30 km). Mars's atmosphere varies by factors of 2 or more at entry altitudes there (135 km on down to 10 or 20 km). That's too variable to trust very much with men. Even probe designs have had difficulties with this variability.
My rough-out design is posted in an article over at http://exrocketman.blogspot.com as the article titled "Mars Mission Study 2013", dated 12-13-2013, if you want to go look at more details. I have updated that article with second thoughts and extra data, and will continue to do so. As posted, it represents an upper bound on the costs for a mission that accomplishes a huge return no matter what happens, with all-chemical propulsion and all reusable-or-salvageable hardware.
When I use the term "rough-out" design, I'm talking about something better than a bounding analysis, but less than a full design analysis. I used the simple rocket equation, with empirical "jigger" factors for drag and gravity losses where applicable (the same sort of stuff von Braun was doing in the 1940's and 1950's to show what is possible before embarking upon real designs, and we all know how that turned out during the 40's, 50's, and 60's).
I used a very old entry approximate analysis originally developed for warheads. I used some very approximate terminal descent kinematics from constant-acceleration physics, modified by intuitive safety factors that hopefully are very conservative.
I did work out the appropriate volumes and shapes to go with my weight statements, just good enough to get realistic diameters and lengths for the vehicles. My volume allowance is near 60-100 cubic meters per person, in both the transit habitat and the lander, but I didn't work out the details of how much is for congregating together vs being alone. I doubled and tripled the typical allowances for for food air and water for the crew, because I think frozen food and water-based cooking are going to be required (the artificial gravity enables this, too).
GW
Thanks very much!
I've noted your landers (and all the rockets of your ship) use LOX-LH2 to save propellant mass: how do you solve the problem of boil-off douring a year long mission?
I wouldn't be too surprised if it works at low temperatures. But I wouldn't know either. In any case I think meth-lox is a pretty strong contender, given that the chemistry of synthesis is less complex.
You're right. Propylene/CO-LOX has the only vantage to be synthetyzed with the little water vapor of Mras atmosphere, without bringing hydrogen form home. Probably it will be more simple to land in a place where we know there is ice, and use it to synthetyze LOX-LCH4.
The volume, mass, and/or number of propellant tank modules in any design far exceeds the volume, mass, and/or number of all other types of things, in any conceivable Mars ship, chemical or nuclear. The only thing needing artificial gee is the crew hab, which is 1, 2, maybe 3 of these small components. That being the case, I saw no reason to build a spinning wheel for a habitat. That way lay "battlestar galactica" stuff.
What I came up with was something about the same volume allowance as the old Skylab for a crew hab, with a crew of 6. That's twice the crowding the old Skylab crews of 3 saw, but still spacious compared to Mir and ISS. I did a combined parallel-series stackup of propellant modules to achieve a length between about 100 and 200 meters, with pusher engines at the tail end. It spins like a baton end over end to put 1 full gee at the farthest crew deck, less at higher decks, but still over half a gee. The whole ship was in the 300-500 ton class, but assembled of modules small enough to launch with Atlas-5, Delta-4, and a few Falcon-Heavies.
No need for a hugely-expensive SLS. It's tonnage to launch multiplied by unit launch cost (per unit mass of payload), which is only low if the launcher flies fully loaded. You launch all this tonnage at the anticipated unit costs for SLS, and the economics become politically unsustainable, no matter what size objects you launch. $1000-2500/pound is something we can tolerate. 10,000/lb is not. Period. I see no point to an SLS-class launcher until commercial space sees a need for it, and does it at well under $1000/lb. And someday, they will. But not in the next several years.
The landers went separately, each pushing the landing propellant supplies as dead-head cargo. These went unmanned and unspun. Still modular, using exactly the same common propellant tank modules as the manned ship. I did not rely on in-situ propellant, and I did not jettison so much as a single tank into deep space. I recovered every single item in my design for reuse or salvage, either at Mars or in Earth orbit. No free return, either. So my mission design represents a generous upper bound on what has to be launched and assembled. The three unmanned ships, pushed by the landers themselves, were in the 1000 ton class, each. That's in the neighborhood of 4000 tons that has to be launched and assembled. A nuke would be around half of that, this was a LOX-LH2 chemical rough-out.
This verges upon "battlestar galactica" problems, yes, but it also accomplishes much more than most mission plans I have seen. I budgeted the propellants from Earth to spend the first 5 or 6 months at Mars making 6 separate landings plus a visit to Phobos from low Mars orbit. The best site explored (presumably with lots of massive buried ice to mine), would be selected for a base. The remainder of the year at Mars would be spent there at the best site, building that base, all 6 on the surface with all 3 landers. If the ISPP actually works at the base site, it produces the extra propellants to support suborbital lander flights to explore additional sites. Icing on the cake, it would be. But we get a huge return, even if it doesn't work. Including a functioning base waiting for folks to return on the next trip.
As I said, an upper bound. You get exactly what you pay for. But you must also remember that nothing is as expensive as a dead crew. So, don't be too cheap. Cheap kills. We've already seen it.
GW
Your modular spaceship looks very intresting: once arrived on Mars, will she insert in orbit propulsively or via aerocapture?
In the last case, do you use some kind of foldable aeroshell on the head module?
I have soy milk powder; from a local store called the Bulk Barn. It's just defatted soy flour; no additives. And I have Crisco brand soy oil.
Is not simple to extract oil from soy, corn or sunflower seed: you need solvents and a very good system to remove them. Whitout a chemical industry, on Mars is better to use olive oil that can be extracted by pressure only.
What about this NASA 500 KW small nuclear reactor?
http://spaceref.com/nuclear-propulsion/ … otype.html
It may be perfect to ISPP.
I'm not sure there is a way to get effective shielding in a nuclear lander, because it needs to be short and squat for landing stability on rough ground. If it were a long slender shape, the propellant and tankage structure actually maker a pretty good shield. Trouble is, things like that tip over way too easily upon landing.
If you really want a nuclear lander, you have to limit your inherently-unavoidable radiation dose by limiting the time you are aboard. That means you have to pitch your surface habitat remote from your ship. There's just no way around that dilemma with solid core nuke rockets. Might be fixed with open-cycle gas core, but we don't have those things yet. But it does buy a very large payload fraction for a ferry design.
GW
Douring the transfer the habitat may be detatched from the engine via a long cable for artificial gravity. After landing we can imagine a wheeled habitat that move far from from rocket platform. Leaving Mars, the habitat may return on the platform before take-off to separate again via cable after orbital inserction. So crew will be exposed only douring landing and take-off.
Do you think that dissolving the acetylene in CO at low temperatures would be enough to make it safe?
Landis thinks an acetylene-CO 50% mixture may be stable enough. I'm not an expert.
http://io9.com/5664014/making-a-baby-in … l-involved
I think there have been a number of experiments showing the risk to embryo development.
You have also to note that the experiments was not performed in microgravity, but in simulated microgravity, with a Earth based device that countinously change orientation, to not have a stable up-down position. So we have only extrapolated data on embryo develpoment in real microgravity, and completely no data on a 0.38 gee low gravity.
I've found this interesting article by Geoffrey Landis about a new rocket propelled by LOX and a mixture of acetylene and CO at 50%: it has an Isp about 350 s: the hydrogen needed is less than 1% the total propellant mass, and so the little amounth (0.03%) of atmospheric water vapor may be enough to drive the production, without bringing hydrogen from Earth.
IMO the VASIMR guys are not being totally honest about the performance of their system. They've been quite big on plans (They keep repeating that 39 days to Mars lie over and over again, after all) and very nonspecific on achievements.
Anyway, given actually available power sources I don't think Isp really matters that much once it gets higher than 3000 s or so.
A 39 days to Mars may be achived only coupling VASIMR with a Bussard's Polywell fusion generator, if it will work. But Bussard has just designed the probably more efficient high thrust-high Isp electric propulsion QED engine, to couple with his Polywell.
However VSIMR stody may be of some interest, for undertanding magnetic nozzle.
I was very impressed in reading GW Johnson's post in the VASIMR topic about a 500 s Ips water NERVA spaceship that can go everywhere in the soilar system, melt the ice, refuel and came back.
If we project this kind of ship as a bipropellant rocket with one tank for water and one tank for liquid CO2, we can have a ship that depart from LEO using water, land on Mars and get liquid CO2 from atmosphere: LCO2 has very low Isp, but it can be used to expolore Mars, moving from site to site via suborbital hopping. At the end of the mission, the ship will hop to one of the polar cap, refuel of water and return to Earth.
It may be very interesting, but to perform aerobraking and land the ship has to be compact (I imagine some kind of Dragon like 8-12 meter diameter capsule with the rocket in an openable compartment in the centre of the thermal shield, but I'm not an engenier) and I have no idea how to protect crew from radiation douring orbital transfers, when the water propellant tank is empty (the drinkable water tank may be enough to give such a shielding?), or after landing when the crew enter and exit.
It is possible to project some sort of extesible truss/boom to keep the habitat far from the engine douring travel (it may also be used for artificial gravity) that may be oriented orizontally after landing?
Have you considered launching it unfueled? That's a nice safety feature but given cost constraints it might be worth asking oneself whether it could be worth it to try to make up for he reduction in safety some other way.
For example, if experience shows the Falcon series of rockets to be much safer than other rockets, it would sill be an improvement in safety to do multiple launches and then do some kind of rendezvous.
Is it possible to launch with Falcon H vehicles larger than payload fairing (like an 8 meters large upgraded Dragon), if they have a good aerodinamical design?
louis wrote:1. Procreation will require some extended replication of 1G
What do you base this on? We have no data between zero and one gee.
Probably 0.38 gee is enough for a correct embryo-fetal development, but as you correctly say, we have no data (if not, it would pose a serious limit on animal breeding)
A one gee facility will be very likely needed for a correct body development of the martian children.
100 meter at 3rpm wil get you near the 1g level but what I am concerned about is the fact that we can barely land a 10 meter diameter space craft. That said where are the materials coming from to build something so large and massive. The power drain to move a large mass will be hard to generate. The motor or motors to make it move.
In the first times, when there will 1-3 habitat and 4-6 crew member, who stay only 500 days, I think the best they can do is to avoid procreation, so they probably dont need a centrifugue.
The surface centrifugue will be built only in a second time when the colony is able to use in situ matherials and the first settlers will start to procreate.
I am also very interested in the effects of .37 g. The issue with saying anything at this point is that we don't know. We know what happens to humans when they're subjected to 0 g for long periods of time: The primary health issue related to this is bone loss. And then we know what happens at 1 g, which is to say that bone mass is relatively steady as a function of time.
However, there are some promising results in this domain, even in 0 g. Because these symptoms are quite similar to the symptoms of osteoporosis, it was found on the ISS that Osteoporosis medicine significantly decreases the rate of bone loss in microgravity. It was shown that the efficacy of these drugs decreased with time.
The study you quote was performed with Alendronate: it may give a good medium mineralization, but the bones may become brittle: bone strenght depend not only on mineralization, but also on the correct orientation on bone trabeculae in counteracting weight, that is difficoult to obtain in microgravity. Bone is continously created by osteoclasts and destroyed by osteoblast, in the way to achieve a perfect orientation of trabeculae, giving the maximal strenght with the minimal mass. Alendronate blocks osteoblast activity shifting the balance on the side of osteosinthetys, but in long terms, the not perfect orientament of trabeculae may result in thigh bone spontaneos fracture. This "frozen bone" effect may happen in Earth gravity environment: we have no data on microgravity, but probably it may be worst.
We also know hormons like myostatin, wich rises in microgravity environment, resulting in muscular mass loss: on STS 188 mission a new myostatin inhibitor was tested on mice, with very good preliminary data http://www.dsls.usra.edu/meetings/hrp2012/pdf/4203.pdf
In a future, I belive it will be possible to solve via pharmacology all space releted problems, like microgravity and cosmic ray protection. But at the moment our knowledge of human physiology is too much incomplete to relay only on drugs for long term space exploration missions. The best we can do now is to recreate as much is possible an Earth like environment, using artificial gravity.
What really pops out to me is that bone mass is a "use it or lose it" deal. The reason why it goes away in space is that the microgravity environment requires much less bone mass than does Earth. The body naturally responds by making less bone. We can artificially increase the rate of bone production or decrease the rate of bone elimination (both of which are natural processes that happen all the time in our bodies here) but in time the body will increase its efforts to equilibrate with its surroundings, and bone loss will eventually ensue.
Given that we use .38 g (Mars' gravity is closer to .38 than .37) I would expect bone loss to ensue 62% as quickly as it did in microgravity, give or take (That is to say, 1-.38 times as quickly). This would make a 900 day round trip Mars mission equivalent to a 550 day stay in LEO-- still unacceptable. However, with the additional provision of osteoporosis medication, and still including exercise (Given that there will be some gravity in the hab, by putting handles on e.g. containers of water the astronauts can actually lift weights and perhaps even do things like MMA fights) I would expect things to be fine.
Probably, Mars gravity, plus weighted clotes, 2-4 h/day of walk in spacesuit, plus squat, aerobic exercise may result in good muscolar and bone manteinment.
and perhaps even do things like MMA fights
I'm very courious about martial arts in microgravity and low gravity: if you are interested we can open a new topic about it.
All of this goes out the window if you don't care about a return to Earth. Because the decreasing bone density is an adaptation to lower levels of gravitation, there is not necessarily any issue with this in the context of a permanent trip to Mars. I would expect bone density to be much lower for people and animals raised on Mars (and experiments on animals during missions can certainly test this), but I wouldn't expect this to be a problem so long as they remained on worlds with no more than 1.5 to 2 times as much gravity as Mars (5.6-7.4 m/s^2; There are very few places in the solar system with this level of gravity. So far as I know, the next-lowest surface gravity in the Solar System after Mars is Venus, with 8.9 m/s^2).
People on Mars are likely to be tall and lanky, with less muscle than Terrans. For someone born on Mars, it would take the equivalent of a bodybuilder to be able to go to Earth. I would imagine that more arduous for a Martian than the trip would be the months of exercise and special drugs that would be needed to go to Earth.
If I will be a Mars settler I will not like my personal life choise must be a point of not return even for my children. I will like to have healty children with a corrected developed body, able to visit Earth if they like and free to return living on it if they want. So, why not built in the colony a one gee facility?
I think in terms of raising children on Mars there is a bigger problem. I believe it is the case that studies in zero G have shown abnormal development in embryos. Accordingly, we will need 1G facilities either on the surface, or in Mars orbit, where a woman can gestate the embryo safely. There may be a trend towards artificial insemination with a view to gestating twins.
I have never considered 1G facilities on the surface a practical solution but am happy to be persuaded otherwise.
Homebox genes seems have difficoult in microgravity to recogize where is the right place to make the head and to make the feet. 0.37 gee may be enough to give such orientation, but we have no data. Before procreate, it will be better to test if animal embrion can develop correctly. If not, pregnat woman will live in a one gee centrifuge.
There are a lot of topics about artificial gravity douring space flight, but we are not sure that Martian 0.37 gee is enough to avoid muscular hipotrophy.
Probably 2-3 hour day of walking in a heavy spacesuit, puls weighted clothes, squat training and aerobic exercise and an appropriate diet may be enough to mantein the muscular strenght and the bone mineralization of an adult astronaut for the 500 days of a mission.
But if we look foreward, to a permanent settle, what will happen to a Mars borne child?
Are 0.37 gee, plus gym and weighted clothes enought to develop normal muscolar and bone, that allow him to return to Earth in a future?
Having no reliable data, I think may be better to built a centrifugue facility, where the coloniest can train 2-3 hour day in a high gravity environment.
Regarding mobile habitats:
First, I'd like to suggest that the Hab probably won't be that big. It certainly won't move very fast, and air drag will be immeasureably close to nil. We don't care about high accelerations. If it takes 20 seconds to get up to cruising speed of 15 kph, that's fine! Rather than driving through or over rocks, it should be possible to build a mechanical system where a wheel rises upon hitting an obstacle, in order to save energy. Large wheels will keep the hab from sinking very far into any sand that might be around.
I would expect that with proper lubrication, and the aforementioned techniques, I propose that the hab would be able to drive at a speed of 15 kph with a power of 20 hp. That's about 15 kW. 15 kW for say 15 hours of the day (when there will be no power production occurring) amounting to a total storage requirement of 810 MJ.
This would necessitate more than a tonne of batteries, which is unreasonable. On the other hand, should methlox be used the low efficiency of internal combustion engines means that a large area of solar panels would be necessary.
I propose instead that driving be limited to daytime when enough power is being generated to support it. By upping the driving speed to 25 kph (15 mph) and driving for 10 hours out of the day, it would be possible to circumnavigate the Martian globe in 85 days; However, I'm not suggesting a full circumnavigation.
So, if I've understood, your mobile habitat will be powered by an orientable solar array, only during daylight, with only little buffer batteries as a reserve of power and to feed the life support system douring the night. It's right to not drive in the night: it may also be dangerous.
I'd imagine that driving halfway around the globe would be sufficient to cover lots of good potential colony sites, and realistically it would be rather difficult to drive across Tharsis. I'm thinking a drive from the eastern part of Valles Mareneris, straight east to Elysium would be the way to go. It looks to be 10,000 km or so, and covers a whole lot of good-looking territory.
Valles Marineris may be very interesting: starting from Elysium Planetia, do you suggest to reach it cruising only in the northen depression, avoiding highlands (go eastward, circumnavigate Tharsis and reach Vallis Marineris) ?
In this case we can explore Cerberus Fossae that is very interesting. It may also be interest to circumnavigate the Elysium Volcano wit a stop in the ice lake in the Vastitas Borealis.
The drive could be one motor for each wheel, for a total of (I figure) 8 4 kW electric engines, so that a higher-than-average power can be used to drive over obstacles or up slopes. This would involve some amount of battery storage, of course, but not nearly as much as driving overnight.
All in all, I would expect it to add a tonne or two to mission mass. But the increase in mission capacity will make it much more than worth it.
Eight electric motors will also provide a good redundancy in case of failure.
I would think that they would want to go to one of the more equatorial regions, perhaps those where large underground seas/glaciers have been found. I would expect that water from these would locally migrate up to the surface, at a slow rate.
It's important to perform first an unmanned prospection mission to know exactly how deep is the water pack.
How much deep can we drill, with the hardware that can be realistically stowed in a lander?
Hi Louis:
First time I'd seen it, thanks. Any manned settlement Mars One establishes is going to need a large supply of water (locally as ice). They need to develop some ground truth about buried glacial deposits of ice at all the sites they are considering. I've never seen a lander or an orbiter equipped to do that. Saw nothing in the article about that, either.
Water content in the Martian soil suffers from two really serious problems: (1) 1-2% ice-in-soil is an awfully diffuse resource to recover, and (2) an awful lot of that soil-bound ice seems to be far too salty for human or agricultural use without some sort of chemical cleanup.
In contrast, a buried glacier would very likely be real freshwater. Especially if it once was pack ice from a vanished ocean.
To find out what's really down there, and how much there really is, takes a drill rig capable of drilling as much as a kilometer down. Based on the probe designs I've seen, we'll not get data like that until men go, and even then only if their rover has the drill rig on it. Needs a digging blade, too. Basically, we need a backhoe/front-end loader, but with a drill rig on it.
I surely would hate to see people settled onto a site that turns out to be a dry hole. Because then we'd have to watch them all die without realistic hope of rescue. Commercial or governmental, doesn't matter; there is nothing as expensive as a dead crew. That's been the history of it, going back to the first manned flights in the 1960's.
GW
This place must be very good, because we are sure there is water. http://www.space.com/1371-ice-lake-mars.html
It's in Vastitas Borealis and in winter it may be too cold, but we can built a mobile habitat that stay near the lake in spring, summer and autumn, acumulate a water reserve and move south in winter.
Marry Xmas to all!