Lift off and touch down

TonyTMarsBeginner · 2016-10-04 01:48:25

There are so many interesting areas dealing with Mars and two of these that I (new to all of this) seem to keep struggling with are the earth take off and the Mars landing. With our atmosphere it takes so much fuel to just get to space and the more you carry the more fuel needed so there seems to be an exponential of fuel needs and associated costs thereof. But with Mars landing is it the same problem but in reverse? Not very much atmosphere equates with too much speed so more fuel is needed to slow down and more weight causes more speed leading to more fuel needed for heavier loads etc. To me it seems like these two obstacles are central to everything else that is to eventually be accomplished. I mean it appears to me that everything is going to be prioritized according to weight, fuel, and cost. This is stating the obvious in some ways but in others it isn't. Especially when politics are tied up and in with the costs in the form of governments and politicians saying yes or no to budgets etc. I would bet on the importance of getting the most bang for your buck or the most possible resources on the first couple of trips before programs or politicians get changed. These issues play into long term stays vs short, permanent colonies or occasional visits, and a myriad of other things. So my questions are these- how much fuel would be needed to land all the prioritized tools, robots, and resources on the surface of Mars (not counting earth take off) - how would this happen would it be many little lightweight trips or a few large fuel burning trips to the surface- and lastly could fuel be realistically harvested from space or Saturn or someplace and held in orbit above Mars for these trips down?

JoshNH4H · 2016-10-04 08:12:27

You've actually hit the nail on the head when you say that the mass increases exponentially. The equation governing these things is called the Rocket Equation, which is as follows:

R=exp(ΔV/Vex)

Where:

R is the mass ratio, which is the ratio of the mass of the rocket when fully fueled (Also known as "Wet Mass") to its mass after it has expended all of its fuel ("Dry Mass"). For example, if I build a rocket that weighs 1000 tonnes at liftoff but 900 tonnes of this are propellant and 100 tonnes are payload, structure, engines, etc., the mass ratio is 1000/100=10.

exp(X) is the exponential function, e.g. e (An irrational number approximately equal to 2.718; more information here if you're interested) raised to the power of X.

ΔV (Pronounced "Delta-Vee"; Delta in physics and engineering means "change in" and V means velocity) is the change in velocity associated with the mission. In free space with no air or gravity, this is the change in speed that the rocket would experience if it fired all of its fuel while pointing in the same direction. When you're firing in a gravitational field or in an atmosphere the actual change in speed will be lower. Wikipedia gives the delta V for a number of different maneuvers here, but for reference Earth surface to low Earth orbit is about 9,500 m/s and Mars surface to low Mars orbit is about 4,250 m/s.

Vex is the velocity of the rocket engine's exhaust. This can be measured in m/s or in seconds. If an Isp is given as 300 s, that means that a pound of rocket fuel can generate one pound of force for 300 seconds before it was all used up (This dates back to US engineers in the 60s and is falling out of favor now). When measured in seconds Vex is known as Specific Impulse, or Isp. You can convert between Isp and Vex as follows:

Vex=Isp * g

Where g is the acceleration due to gravity at Earth's surface, 9.8 m/s^2. For reference, Hydrogen/Oxygen rocket engines (as used on the Space Shuttle) have a Vex of about 4,500 m/s in a vacuum. Kerosene/Oxygen engines (As used in Falcon 9) generally get about 3,300 m/s, Solid Rocket Boosters (Also use on the Space Shuttle) will generally get about 2,700 m/s. At 1 full atmosphere, a good approximation is that you will get an exhaust velocity that is 20-25% lower than in a vacuum.

Rockets launching to Low Earth Orbit from the surface of the Earth are typically 1-5% payload by mass. This sounds like a very small amount (and it is) but it wouldn't really matter if it were cheap. Launch cost for a Falcon 9 is about $5000/kg.

I could go on, but the right way to look at it (in my opinion) is this: Although rockets are expensive, launch costs are actually a fraction of the total cost of the mission, most typically around 20%. Just as importantly, orbital assembly is fairly well-demonstrated at this point. Even if only 0.1% of the liftoff mass of the rocket on Earth makes it to Mars, that is not in itself a huge problem or a mission killer.

Dook · 2016-10-04 10:10:21

TonyTMarsBeginner wrote:

There are so many interesting areas dealing with Mars and two of these that I (new to all of this) seem to keep struggling with are the earth take off and the Mars landing. With our atmosphere it takes so much fuel to just get to space and the more you carry the more fuel needed so there seems to be an exponential of fuel needs and associated costs thereof. But with Mars landing is it the same problem but in reverse? Not very much atmosphere equates with too much speed so more fuel is needed to slow down and more weight causes more speed leading to more fuel needed for heavier loads etc. To me it seems like these two obstacles are central to everything else that is to eventually be accomplished. I mean it appears to me that everything is going to be prioritized according to weight, fuel, and cost. This is stating the obvious in some ways but in others it isn't. Especially when politics are tied up and in with the costs in the form of governments and politicians saying yes or no to budgets etc. I would bet on the importance of getting the most bang for your buck or the most possible resources on the first couple of trips before programs or politicians get changed. These issues play into long term stays vs short, permanent colonies or occasional visits, and a myriad of other things. So my questions are these- how much fuel would be needed to land all the prioritized tools, robots, and resources on the surface of Mars (not counting earth take off) - how would this happen would it be many little lightweight trips or a few large fuel burning trips to the surface- and lastly could fuel be realistically harvested from space or Saturn or someplace and held in orbit above Mars for these trips down?

Could fuel be realistically harvested from space or Saturn (or Venus) or someplace and held in orbit above Mars for refueling vehicles landing on Mars? The answer is no.

The spacecraft that did all of this work, harvesting CO2 from Saturn would have to be huge, beyond anything we can reasonably build. It would probably have to be built in orbit and once launched it would take years to make one round trip to Saturn or Venus and back to Mars.

Also, it would only get you CO2 which you would have to break down into carbon monoxide and oxygen. Rocket fuel is hydrogen and oxygen so you would only be getting one part of your rocket fuel so this harvesting spacecraft itself would have to be refilled with hydrogen periodically. Stored hydrogen would have to vent so you would lose a lot of it as it's going out to Saturn and back. The idea just doesn't work.

Years ago we actually had a discussion about this topic but it was about the need for getting a buffer gas like nitrogen to Mars. That topic was titled "Mars Needs Nitrogen". You should be able to find it.

It sounds like you haven't read Zubrin's book, "The Case for Mars". You should, it's all explained.

TonyTMarsBeginner · 2016-10-04 12:30:21

Thanks for the responses and I'll check out the book too.

louis · 2016-10-04 19:00:35

There are a number of ways at looking at this problem. A lot of mission architectures look to land on Mars (and return) a large craft.

But that sort of approach is not the only one. Another approach I favour is pre-landing supplies in smaller craft and having a small Apollo style lander go on to the surface (leaving behind the main transit vehicle in orbit). This approach also favour in situ resource utilisation - so it's important to get going on habitat construction, food growing, scaled down metal industry etc from the get-go.

TonyTMarsBeginner wrote:

There are so many interesting areas dealing with Mars and two of these that I (new to all of this) seem to keep struggling with are the earth take off and the Mars landing. With our atmosphere it takes so much fuel to just get to space and the more you carry the more fuel needed so there seems to be an exponential of fuel needs and associated costs thereof. But with Mars landing is it the same problem but in reverse? Not very much atmosphere equates with too much speed so more fuel is needed to slow down and more weight causes more speed leading to more fuel needed for heavier loads etc. To me it seems like these two obstacles are central to everything else that is to eventually be accomplished. I mean it appears to me that everything is going to be prioritized according to weight, fuel, and cost. This is stating the obvious in some ways but in others it isn't. Especially when politics are tied up and in with the costs in the form of governments and politicians saying yes or no to budgets etc. I would bet on the importance of getting the most bang for your buck or the most possible resources on the first couple of trips before programs or politicians get changed. These issues play into long term stays vs short, permanent colonies or occasional visits, and a myriad of other things. So my questions are these- how much fuel would be needed to land all the prioritized tools, robots, and resources on the surface of Mars (not counting earth take off) - how would this happen would it be many little lightweight trips or a few large fuel burning trips to the surface- and lastly could fuel be realistically harvested from space or Saturn or someplace and held in orbit above Mars for these trips down?

SpaceNut · 2016-10-05 19:36:44

Liftoff mass to what is delivered to its destination is a problem as the cost a total sum is why we are not going as the mass deliverable is not obtainable in 1 launch which makes for what space x is doing for recoverability and reuse so important to lowering costs. Next for Space x is the heavy version of there rocket which will aid in getting the mass to mars that we need.

TonyTMarsBeginner · 2016-10-18 18:14:09

louis wrote:

There are a number of ways at looking at this problem. A lot of mission architectures look to land on Mars (and return) a large craft.
But that sort of approach is not the only one. Another approach I favour is pre-landing supplies in smaller craft and having a small Apollo style lander go on to the surface (leaving behind the main transit vehicle in orbit). This approach also favour in situ resource utilisation - so it's important to get going on habitat construction, food growing, scaled down metal industry etc from the get-go.
TonyTMarsBeginner wrote:
There are so many interesting areas dealing with Mars and two of these that I (new to all of this) seem to keep struggling with are the earth take off and the Mars landing. With our atmosphere it takes so much fuel to just get to space and the more you carry the more fuel needed so there seems to be an exponential of fuel needs and associated costs thereof. But with Mars landing is it the same problem but in reverse? Not very much atmosphere equates with too much speed so more fuel is needed to slow down and more weight causes more speed leading to more fuel needed for heavier loads etc. To me it seems like these two obstacles are central to everything else that is to eventually be accomplished. I mean it appears to me that everything is going to be prioritized according to weight, fuel, and cost. This is stating the obvious in some ways but in others it isn't. Especially when politics are tied up and in with the costs in the form of governments and politicians saying yes or no to budgets etc. I would bet on the importance of getting the most bang for your buck or the most possible resources on the first couple of trips before programs or politicians get changed. These issues play into long term stays vs short, permanent colonies or occasional visits, and a myriad of other things. So my questions are these- how much fuel would be needed to land all the prioritized tools, robots, and resources on the surface of Mars (not counting earth take off) - how would this happen would it be many little lightweight trips or a few large fuel burning trips to the surface- and lastly could fuel be realistically harvested from space or Saturn or someplace and held in orbit above Mars for these trips down?

I think this is a better approach and good for safety and communication reasons. Would it be a good idea to have a humanoid robot as one of the resources so that work and projects could continue between the human missions?

kbd512 · 2016-10-19 13:11:26

The quantities of chemical propellants required to deliver elements of robotic and human exploration missions to the surface of Mars is of relatively minor consequence if we have truly reusable rockets that we can refuel on the surface of Mars. The problem is that true rocket reusability and LOX / LCH4 manufacturing on Mars are technologies that have not been demonstrated.

The first tool that we need to land on Mars is a small nuclear fission reactor that generates 100kWe (SAFE-400 weighs 1200kg). Current solar panel and battery technology can't generate the continuous power required to run a LOX / LCH4 plant capable of mass producing those chemical propellants using less mass than a small fission reactor. The solar irradiance Mars receives is approximately 44% of what Earth receives. The particulate matter suspended in the atmosphere of Mars further reduces the solar radiation that makes it to the surface of the planet. Mars also has an Earth-like day/night cycle, which means solar panels only receive enough light for useful power production for about six hours of that cycle and batteries are therefore required to store electrical energy to continue operations at night. The propellant plant and ice mining vehicles that deliver ice to the propellant plant also require power to operate.

Let's assume that our propellant plant requires 100kWe to operate. The best case solar irradiance on the surface of Mars is around 100W/m^2. Let's pretend that we have solar panels that are 50% efficient and no degradation in power output will result from the elevated UV-B and cosmic radiation or frigid surface temperatures. To produce 1kWe, we need 20m^2 worth of these notional solar panels. We need 2000m^2 worth of solar panels to provide that power for 6 hours to run the propellant plant. That's roughly 45m x 45m, so that's doable using multiple panels. We also need additional panels to charge a battery to power the plant for the remaining 18 hours of the day when our Mars base won't receive sufficient solar irradiance to charge a battery or produce the required power for propellant production.

The highest energy density graphene polymer battery that's about to enter commercial production for electric vehicles is rated at 1kWh/kg, so we need a 900kg battery to provide power during the remaining 18 hours of the day. The battery alone weighs 3/4 as much as the complete 100kWe fission reactor and its capacity is limited to providing power under normal operating conditions with no reserve capacity. The very best stretched lens solar panels come in at around 300W/kg, but we'll presume 500W/kg, so the mass of our notional 50% efficiency solar panels is 200kg and our solar panel and batteries solution is only 100kg lighter than the fission reactor.

We're ignoring the fact that a battery needs some reserve capacity since we can't drain 100% of the charge from the battery without damaging it. A practical battery would weigh around 1000kg. As previously noted, we have to charge the battery in addition to powering the propellant plant, which means more solar panels. We're also ignoring the dust storms on Mars that have been demonstrated to reduce solar power production by 60% to 70%. The dust storms can last anywhere from a few days all the way up to a month or so. In the real world, where our solar panel efficiency is likely to be nearer to 25% than 50%, we'd need to double the weight allocated for solar panels. The battery will also have to have substantially more capacity to contend with short duration dust storms. There's nothing we can do about longer duration dust storms except to shut down the propellant plant. That solution will easily exceed the weight of SAFE-400.

To provide some perspective on just how far battery technology has to progress to replace small internal combustion engines, I'll use a personal example. I'm building a small, single seat aircraft in my garage called a Taylor Mini-IMP.

Actual Internal Combustion Engine:
Type: Pegasus O-100 58hp 4-stroke, air-cooled opposed piston engine
Weight: 135lbs (61kg) (with electric starter, SDS EIS / EFI, exhaust stack, lithium-ion battery)
Fuel consumption at 75% of maximum rated power (nominal cruise speed) is approximately 2 gallons of AVGAS per hour
AVGAS weighs approximately 6lbs/gal (.721kg/l) and the wing holds approximately 12.5 gallons (72 lbs or 33kg) of gas
Total Weight of Engine and Fuel: 210 lbs (95kg)

Actual Electric Motor and Notional Battery (the electric motor is a real flight-tested electric motor and actual figures are provided):
Type: Zigolo 56kW air-cooled electric motor (actually provides substantially more maximum rated hp than the O-100 for takeoff, but we're only using 45 hp or ~34kW at cruise)
Weight: 10kg
Battery: 85kg lithium air (needs to store 170kWh to provide the same range as the ICE, so approximately 2kWh/kg)

The very best commercial graphene polymer batteries only have to double their energy density for me to obtain equivalent performance in my light aircraft. I will achieve a bit better aerodynamics with the electric motor because the air intake to cool the electric motor would be smaller than that required to cool a gas powered engine, but I still need that non-existent 2kWh/kg battery technology to directly replace the small piston engine. In simple terms, battery technology has quite a ways to go just to directly replace internal combustion engines too small to power most subcompact cars.

Absent leap-ahead battery and solar panel technology, nuclear fission is the most practical power production technology for the Martian surface environment. There are no technological issues to overcome with a small fission reactor, so the power production problem is merely a question of good engineering practices and the political will to overcome the aversion to using nuclear power in favor of a technology that works right now versus what may or may not work at some point in time in the future. We should continue to invest time and money into battery and solar panel development because those technologies are required for other uses, but using them for as a primary power production source for high power applications on the surface of Mars is a bridge too far.

I just don't see us landing fully fueled Earth return vehicles on Mars absent a mega rocket with the lift capability that SpaceX's ITS is intended to provide. The IMLEO requirement to do that is too high. Nuclear power is not a panacea, it's just the best technology we currently have for high power applications on the surface of Mars and an enabling technology for us to make use of local Martian resources in an effort to dramatically lower the IMLEO requirement and make the mission affordable with current NASA budgets and current chemical rocket technology.

louis · 2016-10-19 17:26:31

Hi Tony,

Personally I favour establishment of a permanent, continuous settlement (but with temporary colonists - people who spend maybe 2-4 years on the planet before returning to Earth, who are then replaced by others arriving from Earth, but with increasing numbers as time goes on). A humanoid robot is probably therefore not necessary (humanoids are very complex with multiple joints which I would imagine would pose failure issues in the generally cold environment of Mars). That's not to say robots wouldn't be used - but I imagine they would be things like robot rovers for exploration, robot diggers for water and iron ore mining, robot cleaners for cleaning photovoltaic panels.

I suppose something like Big Dog - the Boston Dynamics robot - would be a good "pack horse" for Mars e.g. for carrying mined material back to base if a mine was located in a difficult area. Generally, though, Mars's surface is good for wheeled robots, especially once boulders are cleared.

TonyTMarsBeginner wrote:

I think this is a better approach and good for safety and communication reasons. Would it be a good idea to have a humanoid robot as one of the resources so that work and projects could continue between the human missions?

TonyTMarsBeginner · 2016-10-20 08:33:42

louis wrote:

Hi Tony,
Personally I favour establishment of a permanent, continuous settlement (but with temporary colonists - people who spend maybe 2-4 years on the planet before returning to Earth, who are then replaced by others arriving from Earth, but with increasing numbers as time goes on). A humanoid robot is probably therefore not necessary (humanoids are very complex with multiple joints which I would imagine would pose failure issues in the generally cold environment of Mars). That's not to say robots wouldn't be used - but I imagine they would be things like robot rovers for exploration, robot diggers for water and iron ore mining, robot cleaners for cleaning photovoltaic panels.
I suppose something like Big Dog - the Boston Dynamics robot - would be a good "pack horse" for Mars e.g. for carrying mined material back to base if a mine was located in a difficult area. Generally, though, Mars's surface is good for wheeled robots, especially once boulders are cleared.

If colonists could cycle through a permanent continuous settlement this would probably be better for physical, mental, and emotional health and makes sense once a sustainable settlement is in place. There is something about Mars that I find interesting and scary at the same time and this is the continual bombardment of its surface with large meteors and other types of debris. This is interesting because of the possibility of finding new materials like unknown elements which might further technology or even life that might have hitchhiked from a distant intriguing place but scary for other reasons. It seems to me like the initial phases of setting up the colony is going to take many people hours which translates into calories which jumps over into food production and all of the fun challenges to figure out but what if after all the effort and time spent on the settlement an asteroid or meteor or comet crashes into it and everything has to begin all over? I was thinking that maybe an underground settlement or rather a portion of the settlement where people could get out of killer storms where equipment could be safely stored and worked on, where radiation is not such a problem, where impacts could be safely dodged etc. but this would have to be really deep I guess and would take up so many resources to build. I was guessing that maybe a robot like a human might be able to dig without having to eat or sleep and could maybe overcome some of the problems associated with low gravity but I suppose cold weather and dust causing problems with joints etc and breakdowns kind of rules this idea out. Would a movable settlement be possible in the beginning to avoid impacts, what is the plan for avoiding these, and how do they detect them in the beginning? And are there possible sites where impacts are not a worry?

louis · 2016-10-20 09:40:15

Yes, this is a serious issue. I too favour underground locations - specifically dig our a trench and put over it a Roman brick roof or similar steel arches which are then covered in copious amount of regolith. That should predict against all but a direct hit.

I think all your questions are good. Sadly I don't have the technical information to answer them! I would say that the cratered surface can be misleading as that of course is built up over billions of years.

Photovoltaic panels on the surface could be at risk, so we would need to keep a reserve safe below ground.

Meteorite strikes mean that we can never really have a single pressurised environment - we need multiple pressurised environments (and if they are connected they need air locks to connect.

I have come round to thinking that a pressurised rover will contribute a lot to an initial colony - and I guess one good feature might be it would offer a potential escape, although bombardments are probably over in a few seconds or minutes.

TonyTMarsBeginner wrote:

louis wrote:
Hi Tony,
Personally I favour establishment of a permanent, continuous settlement (but with temporary colonists - people who spend maybe 2-4 years on the planet before returning to Earth, who are then replaced by others arriving from Earth, but with increasing numbers as time goes on). A humanoid robot is probably therefore not necessary (humanoids are very complex with multiple joints which I would imagine would pose failure issues in the generally cold environment of Mars). That's not to say robots wouldn't be used - but I imagine they would be things like robot rovers for exploration, robot diggers for water and iron ore mining, robot cleaners for cleaning photovoltaic panels.
I suppose something like Big Dog - the Boston Dynamics robot - would be a good "pack horse" for Mars e.g. for carrying mined material back to base if a mine was located in a difficult area. Generally, though, Mars's surface is good for wheeled robots, especially once boulders are cleared.

If colonists could cycle through a permanent continuous settlement this would probably be better for physical, mental, and emotional health and makes sense once a sustainable settlement is in place. There is something about Mars that I find interesting and scary at the same time and this is the continual bombardment of its surface with large meteors and other types of debris. This is interesting because of the possibility of finding new materials like unknown elements which might further technology or even life that might have hitchhiked from a distant intriguing place but scary for other reasons. It seems to me like the initial phases of setting up the colony is going to take many people hours which translates into calories which jumps over into food production and all of the fun challenges to figure out but what if after all the effort and time spent on the settlement an asteroid or meteor or comet crashes into it and everything has to begin all over? I was thinking that maybe an underground settlement or rather a portion of the settlement where people could get out of killer storms where equipment could be safely stored and worked on, where radiation is not such a problem, where impacts could be safely dodged etc. but this would have to be really deep I guess and would take up so many resources to build. I was guessing that maybe a robot like a human might be able to dig without having to eat or sleep and could maybe overcome some of the problems associated with low gravity but I suppose cold weather and dust causing problems with joints etc and breakdowns kind of rules this idea out. Would a movable settlement be possible in the beginning to avoid impacts, what is the plan for avoiding these, and how do they detect them in the beginning? And are there possible sites where impacts are not a worry?

TonyTMarsBeginner · 2016-10-20 12:38:21

louis wrote:

Yes, this is a serious issue. I too favour underground locations - specifically dig our a trench and put over it a Roman brick roof or similar steel arches which are then covered in copious amount of regolith. That should predict against all but a direct hit.
I think all your questions are good. Sadly I don't have the technical information to answer them! I would say that the cratered surface can be misleading as that of course is built up over billions of years.
Photovoltaic panels on the surface could be at risk, so we would need to keep a reserve safe below ground.
Meteorite strikes mean that we can never really have a single pressurised environment - we need multiple pressurised environments (and if they are connected they need air locks to connect.
I have come round to thinking that a pressurised rover will contribute a lot to an initial colony - and I guess one good feature might be it would offer a potential escape, although bombardments are probably over in a few seconds or minutes.

Hi Louis, I like this idea of using arches as they would distribute much of the weight downward supporting much more weight on top and by having them in a trench this would eliminate the need for a complex drilling machine and a dozer or front end loader is simple to make in comparison. Instead of digging a trench though would it be good to erect the structure which could be prefabbed on earth within the Valles Marineris and then bull doze the regolith from above down onto it thus clearing a site above while at the same time accomplishing the work below of layers of protection? The walls of Valles Marineris would provide protection while driving to and from the structure during storms or impacts and temperature under tons of regolith might be more constant too? Harvesting wind and temp changes in and around the Valles Marineris might also be useful. An air locked garage made in the same way and connected to the underground location would allow for fast and easy escape and give protection to the rover.

louis · 2016-10-20 13:58:50

I think Robert Zubrin was the first to suggest Roman arches by the way but not as I recall combined with trenches.

The Valles Marineris is about 120 miles wide so not sure how practical it is to use that, but there must be smaller natural canyons that could be used.

I agree about air locked garages. Seems to be the easiest way to get around on Mars, rather than clambering into a cumbersome spacesuit (IIRC, it can take over an hour to get into one).

TonyTMarsBeginner wrote:

Hi Louis, I like this idea of using arches as they would distribute much of the weight downward supporting much more weight on top and by having them in a trench this would eliminate the need for a complex drilling machine and a dozer or front end loader is simple to make in comparison. Instead of digging a trench though would it be good to erect the structure which could be prefabbed on earth within the Valles Marineris and then bull doze the regolith from above down onto it thus clearing a site above while at the same time accomplishing the work below of layers of protection? The walls of Valles Marineris would provide protection while driving to and from the structure during storms or impacts and temperature under tons of regolith might be more constant too? Harvesting wind and temp changes in and around the Valles Marineris might also be useful. An air locked garage made in the same way and connected to the underground location would allow for fast and easy escape and give protection to the rover.

TonyTMarsBeginner · 2016-10-20 16:14:05

louis wrote:

I think Robert Zubrin was the first to suggest Roman arches by the way but not as I recall combined with trenches.
The Valles Marineris is about 120 miles wide so not sure how practical it is to use that, but there must be smaller natural canyons that could be used.
I agree about air locked garages. Seems to be the easiest way to get around on Mars, rather than clambering into a cumbersome spacesuit (IIRC, it can take over an hour to get into one).

I was sort of thinking the tail end of a small canyon in Noctis Labyrinthus, on the western edge of the Valles Marineris Rift System, close to the impact crater I am not sure if this would be too wide or not but it seems like it is close to interesting geology, wouldn't get as cold, would be close to equator for easier blast off, its closer to volcanoes which perhaps could provide valuable geologic resources like a mineral belt or gases etc, maybe even lave tubes, and green houses could be built on the rim in or by the craters. There seems to be a flat area for landing close by but I don't know if it is to soft to support a landing and I am not that knowledgeable about the height of the volcanoes near by but it looks like there is ice on them which might provide a water source that could be utilized without having to travel as far into the cold regions. Another thing that I was wondering about is whether it is possible to collect and harvest the ice fogs in this area for water etc?

TonyTMarsBeginner · 2016-10-20 17:59:02

kbd512 wrote:

The quantities of chemical propellants required to deliver elements of robotic and human exploration missions to the surface of Mars is of relatively minor consequence if we have truly reusable rockets that we can refuel on the surface of Mars. The problem is that true rocket reusability and LOX / LCH4 manufacturing on Mars are technologies that have not been demonstrated.
The first tool that we need to land on Mars is a small nuclear fission reactor that generates 100kWe (SAFE-400 weighs 1200kg). Current solar panel and battery technology can't generate the continuous power required to run a LOX / LCH4 plant capable of mass producing those chemical propellants using less mass than a small fission reactor. The solar irradiance Mars receives is approximately 44% of what Earth receives. The particulate matter suspended in the atmosphere of Mars further reduces the solar radiation that makes it to the surface of the planet. Mars also has an Earth-like day/night cycle, which means solar panels only receive enough light for useful power production for about six hours of that cycle and batteries are therefore required to store electrical energy to continue operations at night. The propellant plant and ice mining vehicles that deliver ice to the propellant plant also require power to operate.
Absent leap-ahead battery and solar panel technology, nuclear fission is the most practical power production technology for the Martian surface environment. There are no technological issues to overcome with a small fission reactor, so the power production problem is merely a question of good engineering practices and the political will to overcome the aversion to using nuclear power in favor of a technology that works right now versus what may or may not work at some point in time in the future. We should continue to invest time and money into battery and solar panel development because those technologies are required for other uses, but using them for as a primary power production source for high power applications on the surface of Mars is a bridge too far.
I just don't see us landing fully fueled Earth return vehicles on Mars absent a mega rocket with the lift capability that SpaceX's ITS is intended to provide. The IMLEO requirement to do that is too high. Nuclear power is not a panacea, it's just the best technology we currently have for high power applications on the surface of Mars and an enabling technology for us to make use of local Martian resources in an effort to dramatically lower the IMLEO requirement and make the mission affordable with current NASA budgets and current chemical rocket technology.

The solar panels don't have much of a life span even in good weather something like 15 years or so, if this is the case than large arrays would have to be retrofitted or even rebuilt over and over again leading to loss of time and resources along with opportunity costs. I like your idea of nuclear fission reactors as it seems more direct and versatile. Would it be possible to have multiple reactors and even one in a air locked rover to provide mobile energy/power to off site projects or rescues? Another question I have that is not directly related to this one is this - what would be a convincing reason for all of the effort to go to Mar and establish a permanent base that would be so compelling that world political figures/world leaders would be willing to pony up trillions in order to fast track everything? I can think of many reasons that I think important but many in power don't seem as interested in scientific inquiry. I was thinking that maybe rare earth metal deposits if they could be found on Mars in large enough quantities might be an enticement?

kbd512 · 2016-10-21 03:04:42

TonyTMarsBeginner wrote:

The solar panels don't have much of a life span even in good weather something like 15 years or so, if this is the case than large arrays would have to be retrofitted or even rebuilt over and over again leading to loss of time and resources along with opportunity costs. I like your idea of nuclear fission reactors as it seems more direct and versatile. Would it be possible to have multiple reactors and even one in a air locked rover to provide mobile energy/power to off site projects or rescues? Another question I have that is not directly related to this one is this - what would be a convincing reason for all of the effort to go to Mar and establish a permanent base that would be so compelling that world political figures/world leaders would be willing to pony up trillions in order to fast track everything? I can think of many reasons that I think important but many in power don't seem as interested in scientific inquiry. I was thinking that maybe rare earth metal deposits if they could be found on Mars in large enough quantities might be an enticement?

I'm far less concerned about the life of the solar panels than the ability to continuously produce and store 100kWe+. If lithium air batteries were available that could achieve half of the theoretical 10kWh/kg energy density and flexible thin film solar panels were available that could achieve 50% efficiency, then my concerns about power production and storage would go away. We're just not "there" yet, nor anywhere close to being "there".

SAFE-400's core dimensions are 18" in diameter and 23" tall. It weighs 512kg. To those dimensions and weight, you have to add the dimensions and weight of the radiator panels and heat engine to produce electrical power. The overwhelming majority of the weight associated with typical space nuclear fission power systems is shielding mass and radiator mass, with radiator mass dominating the weight category for high power output systems. For surface power applications, where the reactor will be buried in a hole, the surface of the planet provides most of the shielding mass. However, we're still left with substantial radiator mass. SAFE-400 weighs 1200kg with the mass of the radiator and heat engine included. The overwhelming majority is radiator mass.

Recently, NASA has started conducting focused research into the use of graphene for high temperature radiator panels. Mass reductions of 80% to 90% should be achievable using graphene. In addition to being extremely light, graphene is also a superb heat conductor. All said and done, we could have a 100kWe power source that can be stored within the dimensions of a 55 gallon drum and weigh around 700kg. That's substantially more compact than the notional solar power system I described in my previous post.

This reactor would be mounted in a small solar electric rover of somewhat novel design, modeled after NASA's ATHLETE robot. The reactor would sit on a steel base plate shaped like a drill head. The reactor would be slowly rotated until the core was augured into the Martian regolith. After emplacement, the radiator panels would be unfurled and a cable run from the planted reactor to the habitat module or propellant plant. Emplacing the reactor in a hole makes the actual exclusion zone quite small.

There should be no feasibility issues with delivering reactors and emplacement robots using Red Dragon spacecraft. Two Red Dragon spacecraft could prove the feasibility of the life support and propellant plant technologies required to send humans. The first lander has the reactor and ATHLETE / ice mining robot and the second lander has the propellant and breathing gas production plant demonstrator. After initial production has started, the manufactured propellants will be used to power a small methalox combustion engine to assist with ice mining and earth moving.

Small enough for off-site power? Sure. Rescues? Probably not, but that depends on what you had in mind. As far as convincing politicians to quit spending money on killing people and start spending it on exploring the greater part of the universe around us, good luck with that. Fortunately, we don't need trillions of dollars for space exploration. We just need to intelligently spend the funding that is provided. A lot more could be done a lot faster with half-way intelligent resource allocation. Again, good luck with that.

louis · 2016-10-21 03:35:02

There's more than one way to skin a cat as we say in the UK...

However, I think the drawback with nuclear is that it would be somewhat inflexible: you can't slice off 10% of it to set up an auxillary base somewhere. If it goes wrong, your whole energy supply goes wrong: a life threatening development.

I think PV plus methane will work and the beauty of that is you can land PV panels and methane production facilities before any humans land, so you know you have a reserve energy supply (the methane) available on landing. Accordingly, battery life is not a crucial issue (although, clearly, we would be taking a large stock of batteries- in the 100s of Kgs I would think - because they are very useful).

kbd512 wrote:

I'm far less concerned about the life of the solar panels than the ability to continuously produce and store 100kWe+. If lithium air batteries were available that could achieve half of the theoretical 10kWh/kg energy density and flexible thin film solar panels were available that could achieve 50% efficiency, then my concerns about power production and storage would go away. We're just not "there" yet, nor anywhere close to being "there".
SAFE-400's core dimensions are 18" in diameter and 23" tall. It weighs 512kg. To those dimensions and weight, you have to add the dimensions and weight of the radiator panels and heat engine to produce electrical power. The overwhelming majority of the weight associated with typical space nuclear fission power systems is shielding mass and radiator mass, with radiator mass dominating the weight category for high power output systems. For surface power applications, where the reactor will be buried in a hole, the surface of the planet provides most of the shielding mass. However, we're still left with substantial radiator mass. SAFE-400 weighs 1200kg with the mass of the radiator and heat engine included. The overwhelming majority is radiator mass.
Recently, NASA has started conducting focused research into the use of graphene for high temperature radiator panels. Mass reductions of 80% to 90% should be achievable using graphene. In addition to being extremely light, graphene is also a superb heat conductor. All said and done, we could have a 100kWe power source that can be stored within the dimensions of a 55 gallon drum and weigh around 700kg. That's substantially more compact than the notional solar power system I described in my previous post.
This reactor would be mounted in a small solar electric rover of somewhat novel design, modeled after NASA's ATHLETE robot. The reactor would sit on a steel base plate shaped like a drill head. The reactor would be slowly rotated until the core was augured into the Martian regolith. After emplacement, the radiator panels would be unfurled and a cable run from the planted reactor to the habitat module or propellant plant. Emplacing the reactor in a hole makes the actual exclusion zone quite small.
There should be no feasibility issues with delivering reactors and emplacement robots using Red Dragon spacecraft. Two Red Dragon spacecraft could prove the feasibility of the life support and propellant plant technologies required to send humans. The first lander has the reactor and ATHLETE / ice mining robot and the second lander has the propellant and breathing gas production plant demonstrator. After initial production has started, the manufactured propellants will be used to power a small methalox combustion engine to assist with ice mining and earth moving.
Small enough for off-site power? Sure. Rescues? Probably not, but that depends on what you had in mind. As far as convincing politicians to quit spending money on killing people and start spending it on exploring the greater part of the universe around us, good luck with that. Fortunately, we don't need trillions of dollars for space exploration. We just need to intelligently spend the funding that is provided. A lot more could be done a lot faster with half-way intelligent resource allocation. Again, good luck with that.

louis · 2016-10-21 03:38:52

Thanks for the clarification. I too favour using narrow canyons to develop pressurised earth-like environments, however I don't think they would be an early colony feature as their construction would take a lot of planning and effort. Maybe after 10-20 years of colonisation we might be looking into that sort of thing.

TonyTMarsBeginner wrote:

I was sort of thinking the tail end of a small canyon in Noctis Labyrinthus, on the western edge of the Valles Marineris Rift System, close to the impact crater I am not sure if this would be too wide or not but it seems like it is close to interesting geology, wouldn't get as cold, would be close to equator for easier blast off, its closer to volcanoes which perhaps could provide valuable geologic resources like a mineral belt or gases etc, maybe even lave tubes, and green houses could be built on the rim in or by the craters. There seems to be a flat area for landing close by but I don't know if it is to soft to support a landing and I am not that knowledgeable about the height of the volcanoes near by but it looks like there is ice on them which might provide a water source that could be utilized without having to travel as far into the cold regions. Another thing that I was wondering about is whether it is possible to collect and harvest the ice fogs in this area for water etc?

louis · 2016-10-21 04:06:56

As indicated, I don't agree nuclear fission is the best option.

It lacks flexibility. If you want to create a sub-base somewhere, you can't split it in 2. If it suffers a catastrophic failure for whatever reason, your colony's survival is in doubt.

A 100 x 100 metres PV array would produce about 400 KwE per hour, averaged across the day. A large proportion of that could then be converted into methane or ethanol, which would be your energy reserve. The mass could probably be somewhere in the region of 20-40 tonnes with cabling and transmission equipment, using ultralight panels.

Using this sort of system I think you could guarantee a continuous power level of at least 200 KwE, but also much higher peaks, as required, maybe up to 1 MwE, using a combination of direct electricity production, methane-powered electricity and batteries.

This would certainly support a 6 person colony and allow for a range of ISRU experimentation including food growing and scaled down industrial processes.

TonyTMarsBeginner wrote:

kbd512 wrote:
The quantities of chemical propellants required to deliver elements of robotic and human exploration missions to the surface of Mars is of relatively minor consequence if we have truly reusable rockets that we can refuel on the surface of Mars. The problem is that true rocket reusability and LOX / LCH4 manufacturing on Mars are technologies that have not been demonstrated.
The first tool that we need to land on Mars is a small nuclear fission reactor that generates 100kWe (SAFE-400 weighs 1200kg). Current solar panel and battery technology can't generate the continuous power required to run a LOX / LCH4 plant capable of mass producing those chemical propellants using less mass than a small fission reactor. The solar irradiance Mars receives is approximately 44% of what Earth receives. The particulate matter suspended in the atmosphere of Mars further reduces the solar radiation that makes it to the surface of the planet. Mars also has an Earth-like day/night cycle, which means solar panels only receive enough light for useful power production for about six hours of that cycle and batteries are therefore required to store electrical energy to continue operations at night. The propellant plant and ice mining vehicles that deliver ice to the propellant plant also require power to operate.
Absent leap-ahead battery and solar panel technology, nuclear fission is the most practical power production technology for the Martian surface environment. There are no technological issues to overcome with a small fission reactor, so the power production problem is merely a question of good engineering practices and the political will to overcome the aversion to using nuclear power in favor of a technology that works right now versus what may or may not work at some point in time in the future. We should continue to invest time and money into battery and solar panel development because those technologies are required for other uses, but using them for as a primary power production source for high power applications on the surface of Mars is a bridge too far.
I just don't see us landing fully fueled Earth return vehicles on Mars absent a mega rocket with the lift capability that SpaceX's ITS is intended to provide. The IMLEO requirement to do that is too high. Nuclear power is not a panacea, it's just the best technology we currently have for high power applications on the surface of Mars and an enabling technology for us to make use of local Martian resources in an effort to dramatically lower the IMLEO requirement and make the mission affordable with current NASA budgets and current chemical rocket technology.

The solar panels don't have much of a life span even in good weather something like 15 years or so, if this is the case than large arrays would have to be retrofitted or even rebuilt over and over again leading to loss of time and resources along with opportunity costs. I like your idea of nuclear fission reactors as it seems more direct and versatile. Would it be possible to have multiple reactors and even one in a air locked rover to provide mobile energy/power to off site projects or rescues? Another question I have that is not directly related to this one is this - what would be a convincing reason for all of the effort to go to Mar and establish a permanent base that would be so compelling that world political figures/world leaders would be willing to pony up trillions in order to fast track everything? I can think of many reasons that I think important but many in power don't seem as interested in scientific inquiry. I was thinking that maybe rare earth metal deposits if they could be found on Mars in large enough quantities might be an enticement?

TonyTMarsBeginner · 2016-10-21 10:24:50

kbd512 wrote:

Recently, NASA has started conducting focused research into the use of graphene for high temperature radiator panels. Mass reductions of 80% to 90% should be achievable using graphene. In addition to being extremely light, graphene is also a superb heat conductor. All said and done, we could have a 100kWe power source that can be stored within the dimensions of a 55 gallon drum and weigh around 700kg. That's substantially more compact than the notional solar power system I described in my previous post.
This reactor would be mounted in a small solar electric rover of somewhat novel design, modeled after NASA's ATHLETE robot. The reactor would sit on a steel base plate shaped like a drill head. The reactor would be slowly rotated until the core was augured into the Martian regolith. After emplacement, the radiator panels would be unfurled and a cable run from the planted reactor to the habitat module or propellant plant. Emplacing the reactor in a hole makes the actual exclusion zone quite small.
There should be no feasibility issues with delivering reactors and emplacement robots using Red Dragon spacecraft. Two Red Dragon spacecraft could prove the feasibility of the life support and propellant plant technologies required to send humans. The first lander has the reactor and ATHLETE / ice mining robot and the second lander has the propellant and breathing gas production plant demonstrator. After initial production has started, the manufactured propellants will be used to power a small methalox combustion engine to assist with ice mining and earth moving.

There would be more protection for the various reactors by having them in the ground thus eliminating the possible shredding that could happen to panels exposed to flying rock and sand debris in powerful storms. I wouldn't think that a catastrophic failure would be a problem with multiple reactors strategically placed in good locations and wired separately. I think that the first people on Mars are going to need to move fast with as little wasted time and movement as possible, getting a safe habitat completed. I would think that initially it is important to establish the necessities and in order of importance just as fast as possible in case Mars throws a storm or some other unforeseen danger at the crew. I think that the reactors would be quicker to install and provide power that could be depended on. Later on once safety was not as paramount, alternative power sources might be useful and even redundant systems as backup. I have some questions about methalox combustion engines? Will a supply of methane be brought down with the Dragons as a reserve in case it is more problematic to harvest methane on Mars than people think? And should the landing local be in the Tharsis region to be nearer to the methane in case it is relatively easy?

TonyTMarsBeginner · 2016-10-21 10:45:55

louis wrote:

Thanks for the clarification. I too favour using narrow canyons to develop pressurised earth-like environments, however I don't think they would be an early colony feature as their construction would take a lot of planning and effort. Maybe after 10-20 years of colonisation we might be looking into that sort of thing.

Volcanism and subsurface cracks, caves where water might be found forming underground aquifers, geothermal heat, methane, protection from storms, possibility of finding remains of life, wind harvesting, maybe even ice fog utilization, these are some of possibilities of the Tharsis region but is it even possible to land in this area and what locations do you find compelling?

kbd512 · 2016-10-21 11:07:23

louis wrote:

There's more than one way to skin a cat as we say in the UK...
However, I think the drawback with nuclear is that it would be somewhat inflexible: you can't slice off 10% of it to set up an auxillary base somewhere. If it goes wrong, your whole energy supply goes wrong: a life threatening development.
I think PV plus methane will work and the beauty of that is you can land PV panels and methane production facilities before any humans land, so you know you have a reserve energy supply (the methane) available on landing. Accordingly, battery life is not a crucial issue (although, clearly, we would be taking a large stock of batteries- in the 100s of Kgs I would think - because they are very useful).

You're absolutely right. There's more than one way to solve the problem. Going back to the tyranny of the rocket equation, which is part of the premise of the original post, how much mass do you want to devote to a power production and storage solution? The mass and volume of a solar power solution is guaranteed to be higher than the mass and volume of a nuclear fission power solution for continuous power output of 100kWe or so, using current technology or technology that will realistically exist within the next decade, given the history of solar panel and battery development improvements.

Obviously a backup power production and storage solution is required, so that would mean two fission reactors. The complications associated with deployment are digging a hole 18" in diameter, 24" deep, and connecting a power cable from the reactor to another piece of equipment. Everything about Mars is easier said than done, but does that seem like an insurmountable technical challenge to you?

We have rovers that have been driving around on Mars for years now, they have manipulator arms capable of performing complex tasks, and they have tools that can bore into rocks. I think we can manage deployment of fission reactors with core lengths equivalent to 30 pound propane tanks and 1.5X the diameter of the 30 pound tank, but we can also test all of that here on Earth.

Regarding setting up an auxiliary base, that's unlikely to happen. If we could move an entire base and there was a convincing argument for doing that, we would. We wouldn't just move one module to some random location. Here on Earth, we typically construct settlements (housing + work facilities + utilities) in places we think are favorable for whatever purpose the settlement serves and we use vehicles to transport people and products between those buildings. We typically don't pack up and move settlements or power stations, we build new ones in new locations. I want a settlement at this location to mine gold or platinum. Ok, then convince TPTB to foot the bill and we'll do it.

Batteries aren't in common use for utility grade power storage here on Earth and are unlikely to be mass-efficient for utility grade power storage on Mars. Batteries are ubiquitous in vehicles and I would think any land vehicle on Mars would likely use batteries for electric power storage.

Uranium's energy density is 1,539,842,000 MJ/L. The best lithium ion batteries are 3MJ/L. You could increase the energy density of batteries by multiple orders of magnitude and never remotely approach the energy density of fissioning Uranium. Simple physics will not be overcome to suite the personal proclivities of people who oppose using nuclear power over unfounded fears of radiation poisoning or any other artificially manufactured reasoning which ultimately comes back to unfounded fears of radiation poisoning. Nuclear power is as "safe" as any other power production method, for those who choose to believe in fictional human brain constructs that have no bearing on reality, it has demonstrated very high reliability, it has unmatched energy density compared to any existing equivalent solution using any other technology that we actually use for power production, it is affordable, and it is sustainable.

kbd512 · 2016-10-21 11:44:12

TonyTMarsBeginner wrote:

There would be more protection for the various reactors by having them in the ground thus eliminating the possible shredding that could happen to panels exposed to flying rock and sand debris in powerful storms. I wouldn't think that a catastrophic failure would be a problem with multiple reactors strategically placed in good locations and wired separately. I think that the first people on Mars are going to need to move fast with as little wasted time and movement as possible, getting a safe habitat completed. I would think that initially it is important to establish the necessities and in order of importance just as fast as possible in case Mars throws a storm or some other unforeseen danger at the crew. I think that the reactors would be quicker to install and provide power that could be depended on. Later on once safety was not as paramount, alternative power sources might be useful and even redundant systems as backup. I have some questions about methalox combustion engines? Will a supply of methane be brought down with the Dragons as a reserve in case it is more problematic to harvest methane on Mars than people think? And should the landing local be in the Tharsis region to be nearer to the methane in case it is relatively easy?

Did I mention that a 400kWe fission reactor is only a few inches wider in all dimensions, and a few hundred kilograms heavier, using nearly identical technology as those incorporated into SAFE-400?

Does we understand why we can never approach the power production capabilities of nuclear fission with any equivalent mass and size solar panel and battery solution?

Nuclear fission power output level does not scale linearly. A 4MWe fission reactor is a few inches wider than the 400kWe reactor, but uses slightly different power control (reactor control rods) and conversion (flowing gas) methods.

Any claim that a 4MWe solar panel and battery solution could ever approach the mass and volume of a nuclear fission solution is just laughable. The reason nuclear fission power utilizes such large and expensive solutions here on Earth are entirely related to factors other than power output. Our utility grade nuclear power plants are used to reprocess and store spent fuel rods here on Earth, they use low enriched Uranium to discourage theft of nuclear materials that could be repurposed as nuclear weapons, and virtually all use very poor power conversion methods such as steam to drive turbines, thus the gigantic cooling towers and gigantic pressure vessels to contain explosions from hydrogen gas build up associated with pressurized or boiling water coolant.

As louis previously stated, there is more than one way to skin a cat. You can use steam for power conversion or you can use working fluids like molten salts or metals or various gasses with far greater efficiency, with respect to specific work performed. At the end of the day, a nuclear reactor is just a heat engine with incomprehensibly high (to most people) heat output capacity. It doesn't have to be ridiculously efficient for utility in space power applications, it just can't use 1950's power conversion technologies when there are so many substantially more efficient methods available that have dramatically lower volume and mass.

Edit to add content:

SAFE-400 can transition from startup to maximum output in less than one hour and numerous startup/shutdown cycles have been demonstrated. Within minutes of shutdown, radiation and heat drop to a few percent or less of the levels associated with normal operations. Within approximately one hour of shutdown and most certainly after several hours, it's not biologically harmful or "safe" (there's that fabulous fictional word again) for humans to work on the reactor for an hour or two (put their hands on or otherwise handle something directly connected to the core). Nuclear power plant personnel routinely do this here on Earth when they remove fuel rods from the core of a reactor.

Many nuclear power plant personnel have died from falls in cooling towers and reactor buildings or have been electrocuted by high voltage equipment, but the number of people who have died from handling fuel can be counted on one hand since we've started using nuclear power (and the ones who died did ridiculously stupid things that they didn't know were stupid because experimentation with nuclear fuels was still in its infancy and "safety" precautions or prudent handling of nuclear materials, as I call it, didn't exist). Short of doing something ridiculously stupid that the astronauts would've been told to never do ahead of time (like standing on top of the core or in the immediate vicinity when the reactor is operating). And yes, if you do something that stupid the radiation from an operating reactor will kill you (typically within one hour if you were actually standing on top of the core, one day at most if you were within a several meters of the core).

Radiation output drops exponentially with distance from the core. The ground provides substantial shielding for every part of the core except the top of the core that is connected to the heat engine and radiators. We could bury the core several meters down so an astronaut would have to fall into the reactor pit to die from radiation. That'd be pretty damn hard to do since the pit is only 18" in diameter, but there's just no real need to do that. If you stay 100M away or more, there is no radiation output that is harmful to humans because there is virtually no radiation received. I personally think a compromise of building up a small berm around the reactor is sufficient. If the reactor is one meter below the surface, you have to get a lot closer than 100M to get fried. If the reactor is two meters below the surface, you have to stand in the hole to get fried.

Last edited by kbd512 (2016-10-21 12:53:40)

TonyTMarsBeginner · 2016-10-21 14:14:09

kbd512 wrote:

SAFE-400 can transition from startup to maximum output in less than one hour and numerous startup/shutdown cycles have been demonstrated. Within minutes of shutdown, radiation and heat drop to a few percent or less of the levels associated with normal operations. Within approximately one hour of shutdown and most certainly after several hours, it's not biologically harmful or "safe" (there's that fabulous fictional word again) for humans to work on the reactor for an hour or two (put their hands on or otherwise handle something directly connected to the core). Nuclear power plant personnel routinely do this here on Earth when they remove fuel rods from the core of a reactor.
Many nuclear power plant personnel have died from falls in cooling towers and reactor buildings or have been electrocuted by high voltage equipment, but the number of people who have died from handling fuel can be counted on one hand since we've started using nuclear power (and the ones who died did ridiculously stupid things that they didn't know were stupid because experimentation with nuclear fuels was still in its infancy and "safety" precautions or prudent handling of nuclear materials, as I call it, didn't exist). Short of doing something ridiculously stupid that the astronauts would've been told to never do ahead of time (like standing on top of the core or in the immediate vicinity when the reactor is operating). And yes, if you do something that stupid the radiation from an operating reactor will kill you (typically within one hour if you were actually standing on top of the core, one day at most if you were within a several meters of the core).
Radiation output drops exponentially with distance from the core. The ground provides substantial shielding for every part of the core except the top of the core that is connected to the heat engine and radiators. We could bury the core several meters down so an astronaut would have to fall into the reactor pit to die from radiation. That'd be pretty damn hard to do since the pit is only 18" in diameter, but there's just no real need to do that. If you stay 100M away or more, there is no radiation output that is harmful to humans because there is virtually no radiation received. I personally think a compromise of building up a small berm around the reactor is sufficient. If the reactor is one meter below the surface, you have to get a lot closer than 100M to get fried. If the reactor is two meters below the surface, you have to stand in the hole to get fried.

I would be more worried about GCRadiation falling onto the surface of Mars and the radiation already on the surface in the rocks etc than a reactor because there is no guess about where it is or how to deal with it, the variables are already established.

louis · 2016-10-21 14:15:56

It's surprisingly difficult to get some pointers to good landing sites. I think the key factors are fairly flat and firm landing ground, not too much sand, small sized boulders, no evidence of recent water flow. Ideally the landing/base location would be near a suspected water source and sources of useful minerals like iron ore, basalt and silica; would be a bonus if it was close to an interesting geological area e.g. a dried up river bed.

I think somewhere to the east of Valles Marieneris might be interesting.

TonyTMarsBeginner wrote:

louis wrote:
Thanks for the clarification. I too favour using narrow canyons to develop pressurised earth-like environments, however I don't think they would be an early colony feature as their construction would take a lot of planning and effort. Maybe after 10-20 years of colonisation we might be looking into that sort of thing.
Volcanism and subsurface cracks, caves where water might be found forming underground aquifers, geothermal heat, methane, protection from storms, possibility of finding remains of life, wind harvesting, maybe even ice fog utilization, these are some of possibilities of the Tharsis region but is it even possible to land in this area and what locations do you find compelling?

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