Nuclear power is safe

louis · 2019-10-17 16:27:47

I accept that a Mars Mission will rely on sound engineering and you can't have multiple levels of failsafeness. But nuclear power is intrinsically unsafe, just like rocket fuel or wires carrying electricity. I think there is certainly a question mark over adding intrinsic unsafeness to a Mars Mission, when a perfectly viable - and in the view of many, including Space X, it would seem so far, better - alternative is there for the picking.

Calliban wrote:

"And if nuclear is "safe" why do nuclear reactors on submarines have a 100 tons of shielding."
The same reason that power cables from solar plants will be insulated and even safe cars are equipped with seat belts and brakes. Safety comes from sound engineering. It is all about the relative risk that people face from using the thing, whatever it is. It doesn't mean that accidents are impossible. It means that with the engineering in place, your chances of dying that way are small compared to other risks that you face. Without a certain amount of good engineering, nothing that humans build would ever be safe. Your house is only safe because the man that designed it followed building regulations. A shack built out of sand glued together by sugar would not be safe and poorly designed buildings have killed countless people over the years. That doesn't mean that using buildings is inherently unsafe. I'm guessing that your house is safe because it was designed to be fault tolerant. It is possible that it could collapse in an Earthquake tomorrow crushing you to death. But it is unlikely and hence, your house is relatively safe. I bet you don't lay awake at night worrying about your house collapsing. Likewise, I don't sit around worrying about reactors without shielding, because I know they are designed with shielding and that no magic wand is going to make it disappear. I could rattle on some more, but hopefully you get the point.

SpaceNut · 2019-10-17 18:05:21

https://en.wikipedia.org/wiki/Radiation_protection

Fundamental to radiation protection is the avoidance or reduction of dose using the simple protective measures of time, distance and shielding. The duration of exposure should be limited to that necessary, the distance from the source of radiation should be maximised, and the source shielded wherever possible.

The first is why we are not being blasted by the suns output

lots of different materials are used to reduce the exposure level at distance. lead, bnnt fabric, water, hydrogenated plastics

https://www.sciencedirect.com/topics/en … g-material

https://www.sciencedirect.com/topics/en … -shielding

Its not as bad as we would think once we remember that people living around granite are being dosed with radon...

https://www.bhienergy.com/assets/RP-4.pdf
Radiation Protection

https://www.canadametal.com/wp-content/ … elding.pdf
A guide to the use of lead for radiation shielding

https://www.nrc.gov/docs/ML1122/ML11229A721.pdf
Shielding Radiation; Alphas, Betas, Gammas and Neutrons

https://www.mne.k-state.edu/~jks/books/Ch11fulltext.pdf
Radiation Shielding and Radiological Protection

keep in mind there are members who have worked plus lived on those submarines and they are still amoungst us to tell you about it.

tahanson43206 · 2019-10-17 18:47:52

For SpaceNut re #77 ...

Your comment about US nuclear submarines piqued my interest, so I found this:

https://www.epa.gov/radtown/nuclear-sub … t-carriers

The page above confirms that there ** is ** radiation on nuclear submarines and aircraft carriers, but strong safeguards are in place both during operation and after disposal.

Your offhand mention of granite led me to run a quick search on it, and while radon was listed as a component of radiation from granite, I was surprised to learn that granite may contain seams of radioactive material, depending upon the source and the cut. There were several links collected by Google about granite counter tops, for example.

(th)

Calliban · 2019-10-18 02:26:22

louis wrote:

I accept that a Mars Mission will rely on sound engineering and you can't have multiple levels of failsafeness. But nuclear power is intrinsically unsafe, just like rocket fuel or wires carrying electricity. I think there is certainly a question mark over adding intrinsic unsafeness to a Mars Mission, when a perfectly viable - and in the view of many, including Space X, it would seem so far, better - alternative is there for the picking.

Since no amount of logic will sway you on something that you clearly believe in passionately, I give up trying. Believe what you want to believe.

GW Johnson · 2019-10-18 11:37:57

Coal has radioactive materials in it naturally. So the smokestack plume from burning coal is very slightly radioactive. About 1/3 of the average natural background radiation world wide is said to be due to coal power plant emissions.

Natural background world wide average is near 300 milliREM (0.3 REM) annual accumulated exposure. Some locations are up to 10 times higher: high altitudes and igneous rocks are associated with this.

As for Louis's statement that nuclear power, rocket fuel, and wires carrying electricity are inherently unsafe, that is emotion not fact. He prefers a (false) belief system to facts. If rocket fuel is so inherently unsafe, then how does he expect to get to Mars? If wires carrying electricity are so inherently unsafe, then how does he expect to get the power from his his solar panels to wherever it is needed?

The flip side of that very statement is that nuclear power is no more unsafe than rocket fuel or wires carrying electricity. Also ridiculous, considering that every single one of us has wires carrying electricity in our homes. But not rocket fuel!

There's unsafe and there's unsafe, in various degrees, which Louis's statement completely ignores (and THAT is why it is a ridiculous statement). The dangers or risks a technology presents are inherent and unique to that technology. And ALL technologies present dangers and risks, even knapped stone tools, or just simple campfires! There are ways to deal with those dangers and risks. In many cases, people died discovering them, or the need for them.

You simply deal with the dangers and risks, if you want or need to use the technology. It's that simple, and that hard to do. The only "unsafe" thing is not dealing properly with the dangers and risks.

GW

Last edited by GW Johnson (2019-10-18 11:41:48)

louis · 2019-10-18 11:42:07

I believe a 100 tons of shielding on a nuclear submarine is a bit of a tell...

Calliban wrote:

louis wrote:
I accept that a Mars Mission will rely on sound engineering and you can't have multiple levels of failsafeness. But nuclear power is intrinsically unsafe, just like rocket fuel or wires carrying electricity. I think there is certainly a question mark over adding intrinsic unsafeness to a Mars Mission, when a perfectly viable - and in the view of many, including Space X, it would seem so far, better - alternative is there for the picking.
Since no amount of logic will sway you on something that you clearly believe in passionately, I give up trying. Believe what you want to believe.

GW Johnson · 2019-10-18 12:05:16

100 tons of shielding in a ship displacing 6000-7000 tons is not unreasonable at all!

What do you think the bulldozed berm around a kilopower unit will mass, maybe 100 tons?

Don't need to fly that 100 tons of shielding to Mars. Just use 100 tons of the local dirt. Fly a 2-5 ton electric (rechargeable) bulldozer to Mars instead!

What is so damned hard to understand about how to deal VERY EFFECTIVELY with the radiation from a kilopower unit?

Which means you DON'T turn it on during the flight to Mars! Flying in space, where solar works 24/7-no-matter-what, as long as you can face that solar wing towards the sun. Unlike the situation on, or in orbit around, a planet.

GW

Last edited by GW Johnson (2019-10-18 12:09:35)

louis · 2019-10-18 12:14:16

My approach is perfectly logical: it is to minimise the unnecessary use of inherently unsafe technologies. Rocket fuel is currently necessary. But it is inherently unsafe as we saw with the two Space Shuttle disasters. If we can find other, safer launch technologies of comparable power, we should use those.

I accept that safety is on a continuum. Call rocket fuel and nuclear power "high impact risk" if you prefer.

GW Johnson wrote:

Coal has radioactive materials in it naturally. So the smokestack plume from burning coal is very slightly radioactive. About 1/3 of the average natural background radiation world wide is said to be due to coal power plant emissions.
Natural background world wide average is near 300 milliREM (0.3 REM) annual accumulated exposure. Some locations are up to 10 times higher: high altitudes and igneous rocks are associated with this.
As for Louis's statement that nuclear power, rocket fuel, and wires carrying electricity are inherently unsafe, that is emotion not fact. He prefers a (false) belief system to facts. If rocket fuel is so inherently unsafe, then how does he expect to get to Mars? If wires carrying electricity are so inherently unsafe, then how does he expect to get the power from his his solar panels to wherever it is needed?
The flip side of that very statement is that nuclear power is no more unsafe than rocket fuel or wires carrying electricity. Also ridiculous, considering that every single one of us has wires carrying electricity in our homes. But not rocket fuel!
There's unsafe and there's unsafe, in various degrees, which Louis's statement completely ignores (and THAT is why it is a ridiculous statement). The dangers or risks a technology presents are inherent and unique to that technology. And ALL technologies present dangers and risks, even knapped stone tools, or just simple campfires! There are ways to deal with those dangers and risks. In many cases, people died discovering them, or the need for them.
You simply deal with the dangers and risks, if you want or need to use the technology. It's that simple, and that hard to do. The only "unsafe" thing is not dealing properly with the dangers and risks.
GW

Calliban · 2019-10-18 12:14:17

GW Johnson wrote:

100 tons of shielding in a ship displacing 6000-7000 tons is not unreasonable at all!
What do you think the bulldozed berm around a kilopower unit will mass, maybe 100 tons?
Don't need to fly that 100 tons of shielding to Mars. Just use 100 tons of the local dirt. Fly a 2-5 ton electric (rechargeable) bulldozer to Mars instead!
What is so damned hard to understand about how to deal VERY EFFECTIVELY with the radiation from a kilopower unit?
GW

You don't need to move the 100 tonnes of dirt at all if you put the reactor in a pit, some 50cm wide and 3m deep. To do that, you only need to shift 1-2 tonnes of dirt and rock. Much easier than trying to push 100t around the core. Either way, its not a big deal I guess. The bigger the reactor is, the more it benefits from self shielding effects.

louis · 2019-10-18 13:38:40

That leaves you with a problem if you land in the middle of a severe dust storm.

According to nuke-enthusiasts here you won't be able to generate power in the middle of such a storm but you won't have switched on your nuclear reactor yet...

I don't actually believe you will be generating zero PV power, but I am looking at this from the point of view of those who back nuclear.

GW Johnson wrote:

100 tons of shielding in a ship displacing 6000-7000 tons is not unreasonable at all!
What do you think the bulldozed berm around a kilopower unit will mass, maybe 100 tons?
Don't need to fly that 100 tons of shielding to Mars. Just use 100 tons of the local dirt. Fly a 2-5 ton electric (rechargeable) bulldozer to Mars instead!
What is so damned hard to understand about how to deal VERY EFFECTIVELY with the radiation from a kilopower unit?
Which means you DON'T turn it on during the flight to Mars! Flying in space, where solar works 24/7-no-matter-what, as long as you can face that solar wing towards the sun. Unlike the situation on, or in orbit around, a planet.
GW

Calliban · 2019-10-18 14:58:15

Louis, you aren't going to deploy a large solar array covering acres of ground in a dust storm either. It's a good idea not to land in a dust storm for all sorts of reasons.

SpaceNut · 2019-10-18 16:38:27

That is also a problem in that we are only aerobraking to be able to enter mars atmosphere to land.. We are not staging by performing the braking to make it orbit. So once we commit to the target being a landing versus orbiting we are not going to be able to stay in orbit as we will be depleting the energy we have along with many other resources to which we will be looking to use them on the surface.

"The Martian surface is covered with a thin layer of radioactive substances including uranium, thorium and radioactive potassium -- and ... "Maps of gamma rays on Mars show a big red spot.

The background radiation of mars is also not going to be without risk and here is the one which could be used for power in later missions once we can process the ore to make it workable.
Map of Martian Thorium at Mid-Latitudes

https://mars.jpl.nasa.gov/odyssey/galle … 04257.html

https://www.lpi.usra.edu/meetings/lpsc2012/pdf/2852.pdf
ANALYSIS OF URANIUM AND THORIUM LINES IN MARS ODYSSEY GAMMA SPECTRA AND REFINED MAPPING OF ATMOSPHERIC RADON.

https://www.lpi.usra.edu/meetings/lpsc2011/pdf/1097.pdf
EVIDENCE FOR A LARGE, NATURAL, PALEO-NUCLEAR REACTOR ON MARS

https://www.hou.usra.edu/meetings/lpsc2015/pdf/2660.pdf
EVIDENCE FOR LARGE, ANOMALOUS NUCLEAR EXPLOSIONS ON MARS IN THE PAST

Potassium, having the chemical symbol K, is a naturally radioactive element and is a minor constituent of rocks on the surface of mars.
map is simular to the others

GW Johnson · 2019-10-18 16:43:52

In a bizarre way, Louis makes a very good point: What do you do, if you happen to land during a dust storm? Mariner 9 was surprised to find Mars utterly blanketed 15+ km deep when it arrived.

It'll be very, very hard to set up a nuke or a PV system in dust storm conditions. I guess you better have a lot of batteries, because the storm is going to slow down greatly the setting-up of whatever power system you use.

Why should we worry about this contingency? Well, on the off-chance that you survive the landing in the dust storm, you have to do something, or else die.

As for landing in the storm, you cannot predict at launch whether there will be a dust storm raging when you arrive 6 to 9 months later. And if you're landing direct from the interplanetary trajectory. you have no choice at all: you MUST land, dust storm or not, unless your transit trajectory had a period of EXACTLY 2 years. That is because unless you meet that 2 year period criterion, you cannot expect the Earth to be there, when you arrive back at perihelion.

All I can say is, solar don't work when the sun don't shine. But as Louis fears, you cannot stand the radiation hazard to turn on a nuclear reactor, until you have some shielding. That's life.

Now, if you have enough battery to do life support for a few days, and you have a rechargeable electric-powered bulldozer, I don't see why you cannot bulldoze a bit of a pit in a couple of hours, lay your kilopower in it, and then spend a day or so bulldozing-up the berm around that pit. This is driving a bulldozer inside a protected cabin-type work. Despite the lousy visibility, that's relatively low hazard work.

The most dangerous part is the EVA suit work in a blinding dust storm: hooking up the cables down in the pit to the reactor, and then back to the ship. It would help an awful lot if the space suit design was such that an astronaut who falls over can actually get up without help. I DO NOT SEE THAT in the latest designs NASA unveiled.

Get those cables hooked up, and you can turn the kilopower down in that bermed pit on, before ship's batteries run out.

That the conceptual notion at least, of how to survive a landing in a bad dust storm. That assumes you survive the landing itself, which I personally think is a long shot.

GW

Last edited by GW Johnson (2019-10-18 16:51:37)

louis · 2019-10-18 16:53:35

My proposal would involve the following:

(a) Involves taking an emergency store of methane and oxygen to power methane generators, which could be deployed on the Starship in an emergency situation. It's extremely unlikely that would be required.

(b) Mobile ATK fan style PV panels could be deployed on the surface from the lower cargo holds immediately.

(c) There will be Starships on the surface that will have been there for two years and their batteries will be fully charged. Robot battery rovers can travel from the human-passenger Starship to other Starships to charge up as necessary.

(d) The Starship PV fins will continue to produce power. There will never be zero output.

It is wrong to think we couldn't lay out the PV in a dust storm. Using flexible PV on a roll it could be laid directly on the ground from robot rovers. We mustn't run away with the idea that dust storms on Mars will be anything like the one in "The Martian". They will be an annoyance and prevent us producing as much methane and oxygen as we would like to, that is all.

Calliban wrote:

Louis, you aren't going to deploy a large solar array covering acres of ground in a dust storm either. It's a good idea not to land in a dust storm for all sorts of reasons.

SpaceNut · 2019-10-18 16:59:41

Thats when you would use the onboard fuel cell power generator with any of the left over fuels from landing...
The other thing is you only need 1 or 2 at most of the 10kw units in survival mode where power is conserved.
All you really need is the life support for air systems running as you wait it out in the ship.

louis · 2019-10-18 17:17:24

As above, I recommend taking a special methane/oxygen store on the human passenger Starships and 2 x 10 Kwe methane generators.

That deals with the unlikely event that you can't enough PV generation on the surface. I think my calculation was that 3 tons of methane and 12 tons of oxygen would give you about 100 sols at 10Kwe. I would also have a charged battery system of about 30 tons on board. So that would give you another 30 sols perhaps. You've also got the other Starships to draw power from.

One thing, if there is any chance of landing in winter or early spring (bearing in mind the much longer year on Mars), that would be best as dust storms originate in summer, not winter. That might affect whether you go early or late from Earth in a transfer window.

GW Johnson wrote:

In a bizarre way, Louis makes a very good point: What do you do, if you happen to land during a dust storm? Mariner 9 was surprised to find Mars utterly blanketed 15+ km deep when it arrived.
It'll be very, very hard to set up a nuke or a PV system in dust storm conditions. I guess you better have a lot of batteries, because the storm is going to slow down greatly the setting-up of whatever power system you use.
Why should we worry about this contingency? Well, on the off-chance that you survive the landing in the dust storm, you have to do something, or else die.
As for landing in the storm, you cannot predict at launch whether there will be a dust storm raging when you arrive 6 to 9 months later. And if you're landing direct from the interplanetary trajectory. you have no choice at all: you MUST land, dust storm or not, unless your transit trajectory had a period of EXACTLY 2 years. That is because unless you meet that 2 year period criterion, you cannot expect the Earth to be there, when you arrive back at perihelion.
All I can say is, solar don't work when the sun don't shine. But as Louis fears, you cannot stand the radiation hazard to turn on a nuclear reactor, until you have some shielding. That's life.
Now, if you have enough battery to do life support for a few days, and you have a rechargeable electric-powered bulldozer, I don't see why you cannot bulldoze a bit of a pit in a couple of hours, lay your kilopower in it, and then spend a day or so bulldozing-up the berm around that pit. This is driving a bulldozer inside a protected cabin-type work. Despite the lousy visibility, that's relatively low hazard work.
The most dangerous part is the EVA suit work in a blinding dust storm: hooking up the cables down in the pit to the reactor, and then back to the ship. It would help an awful lot if the space suit design was such that an astronaut who falls over can actually get up without help. I DO NOT SEE THAT in the latest designs NASA unveiled.
Get those cables hooked up, and you can turn the kilopower down in that bermed pit on, before ship's batteries run out.
That the conceptual notion at least, of how to survive a landing in a bad dust storm. That assumes you survive the landing itself, which I personally think is a long shot.
GW

GW Johnson · 2019-10-18 18:34:23

I put NASA's own images from Opportunity (right before it died in the cold) on my exrocketman site.

There is no solar power when the sun don't shine, Louis! THAT you cannot deny! Go look at the damned images! And when you do, remember that what killed Opportunity was nowhere near as bad as what Mariner 9 saw from orbit.

My calculations regarding Starship are obsolete in that the weight statement I used is no longer applicable. That was 85 tons of dry unladen ship, 1100 tons of propellant, and 100 tons of delivered payload. I had less than 15 tons of propellant remaining after touchdown, and potentially zero. That depended upon how difficult the landing was, and it would be difficult indeed in a raging dust storm.

I think your methlox generator idea is worthless because of the very real risk that there is no significant propellant left after landing, to use in such a device. And there is as yet NO such device existing, that is rated to run at Mars conditions. Plus, there is no guarantee that your actual landing site is anywhere near any of the other cargo ships that may have preceded you. 50-500 km away is just as out of reach as 5000+ km away. Even 5 km away is cripplingly unreachable under dust storm conditions.

The prudent thing to do is plan for zero sunlight available in the dust storm (assuming you actually survive landing in it, which I strongly doubt), and to plan for no help from anything outside the ship you landed in.

Whatever the power source is, you'd best plan on (1) being able to erect it in zero visibility conditions, which implies fully dark conditions, and (2) you'd best be prepared to do that under such harsh conditions, or else die when your ship's batteries go dead.

I can GUARANTEE you that Spacex has yet to think their way through THAT scenario! They have enough on their hands making a two-stage fully-reusable giant Earth-orbital transport work at all!

What finally does work will bear little, if any, resemblance to anything in the presentations, or the test vehicles yet to fly, so far. THAT I CAN guarantee you! I used to do shit like that for a living.

GW

Last edited by GW Johnson (2019-10-18 18:42:31)

louis · 2019-10-18 19:13:12

I have read that Space X are definitely using a planetary pass on the return to Earth but may also use one for the Mars landing.

SpaceNut wrote:

That is also a problem in that we are only aerobraking to be able to enter mars atmosphere to land.. We are not staging by performing the braking to make it orbit. So once we commit to the target being a landing versus orbiting we are not going to be able to stay in orbit as we will be depleting the energy we have along with many other resources to which we will be looking to use them on the surface.
"The Martian surface is covered with a thin layer of radioactive substances including uranium, thorium and radioactive potassium -- and ... "Maps of gamma rays on Mars show a big red spot.
The background radiation of mars is also not going to be without risk and here is the one which could be used for power in later missions once we can process the ore to make it workable.
Map of Martian Thorium at Mid-Latitudes
https://www.jpl.nasa.gov/spaceimages/im … _hires.jpg
https://mars.jpl.nasa.gov/odyssey/galle … 04257.html
https://www.lpi.usra.edu/meetings/lpsc2012/pdf/2852.pdf
ANALYSIS OF URANIUM AND THORIUM LINES IN MARS ODYSSEY GAMMA SPECTRA AND REFINED MAPPING OF ATMOSPHERIC RADON.
https://www.lpi.usra.edu/meetings/lpsc2011/pdf/1097.pdf
EVIDENCE FOR A LARGE, NATURAL, PALEO-NUCLEAR REACTOR ON MARS
https://www.hou.usra.edu/meetings/lpsc2015/pdf/2660.pdf
EVIDENCE FOR LARGE, ANOMALOUS NUCLEAR EXPLOSIONS ON MARS IN THE PAST
Potassium, having the chemical symbol K, is a naturally radioactive element and is a minor constituent of rocks on the surface of mars.
map is simular to the others
https://upload.wikimedia.org/wikipedia/ … itudes.jpg

SpaceNut · 2019-10-18 21:05:01

Assembly of the core

Here is the answer for nuclear in that Krusty is a 10-kWe machine just 11 feet (3.4 meters) tall, and the reactor component would be the size of an old-school metal garbage can. With shielding, the entire 10-kWe reactor would weigh about 4,400 lbs. (2,000 kilograms). One can also use the water we are taking with us for an extra shadow shielding with what we are bringing. You only need 1 on each ship to take care of the energy required once on mars...that is the safety net for dust storms which block at 100% and allows for energy that is less than all of the solar that a day would recieve in a good dust free day.

GW Johnson · 2019-10-19 08:56:40

Here's something to consider when planning where to set a nuclear reactor up. Initially, the crew will be living in the ship they landed in, whether it is a Spacex vessel or not. It seems likely the inhabited space of any such vessel will be in its nose, located at some height off the ground, as landed.

There are practical limits to how deep a pit and/or how high a berm the crew can excavate with the analog to a bulldozer. So, in order to maintain shadow shielding of the nose of the landed ship, the reactor site must be at sufficient distance from the ship. It's a simple similar triangle geometry thing.

That makes me wonder whether the reactor core and heat extraction hardware ought not to be inside some sort of cargo container-like structure, capable of being fully buried. Otherwise, you are looking at reactor pits and berms located something like a kilometer away from the ship, which would be really hard and dangerous to do, if they landed in a dust storm.

The reactor is safe enough to work with before it is turned on. If it were packaged in a burial-capable container, then only the heat transfer gear sticks out of the ground, leading to the heat engine and waste heat radiator above the surface. Whether you need a berm around that, or just a barricade, I dunno. But with regolith over the core, siting requirements in terms of distance from the ship would seem likely to relax, making installation more feasible in a dust storm.

I worry about the landing in a dust storm, because storms are unpredictable, and the transit trajectory, if direct to surface instead of orbit, will most likely not allow aborting the landing. If they land in a bad dust storm, solar won't work (too dark), and EVA activity gets dangerous due to poor visibility, even with lights. They have only as long as the ship's batteries will last to get the nuclear power plant up and running. Failure is death.

GW

Last edited by GW Johnson (2019-10-19 08:58:49)

louis · 2019-10-19 09:04:37

So that's 200 tons mass to generate 1 Mwe with 100 KP Units - even before you've added in all the additional equipment required. It's way more than a PV system requires. But it will create huge demands on the pioneers in terms of activating them all.

SpaceNut wrote:

Assembly of the core
https://cdn.mos.cms.futurecdn.net/icPZu … 650-80.jpg
https://cdn.mos.cms.futurecdn.net/vC5XT … 650-80.jpg
Here is the answer for nuclear in that Krusty is a 10-kWe machine just 11 feet (3.4 meters) tall, and the reactor component would be the size of an old-school metal garbage can. With shielding, the entire 10-kWe reactor would weigh about 4,400 lbs. (2,000 kilograms). One can also use the water we are taking with us for an extra shadow shielding with what we are bringing. You only need 1 on each ship to take care of the energy required once on mars...that is the safety net for dust storms which block at 100% and allows for energy that is less than all of the solar that a day would recieve in a good dust free day.

louis · 2019-10-19 09:09:42

I think you are now engaging with the real difficulties of using nuclear on a first Mission.

As Calliban suggested there isn't really much evidence that these KP units as currently designed are suitable for anything else but robotic deep space missions.

GW Johnson wrote:

Here's something to consider when planning where to set a nuclear reactor up. Initially, the crew will be living in the ship they landed in, whether it is a Spacex vessel or not. It seems likely the inhabited space of any such vessel will be in its nose, located at some height off the ground, as landed.
There are practical limits to how deep a pit and/or how high a berm the crew can excavate with the analog to a bulldozer. So, in order to maintain shadow shielding of the nose of the landed ship, the reactor site must be at sufficient distance from the ship. It's a simple similar triangle geometry thing.
That makes me wonder whether the reactor core and heat extraction hardware ought not to be inside some sort of cargo container-like structure, capable of being fully buried. Otherwise, you are looking at reactor pits and berms located something like a kilometer away from the ship, which would be really hard and dangerous to do, if they landed in a dust storm.
The reactor is safe enough to work with before it is turned on. If it were packaged in a burial-capable container, then only the heat transfer gear sticks out of the ground, leading to the heat engine and waste heat radiator above the surface. Whether you need a berm around that, or just a barricade, I dunno. But with regolith over the core, siting requirements in terms of distance from the ship would seem likely to relax, making installation more feasible in a dust storm.
I worry about the landing in a dust storm, because storms are unpredictable, and the transit trajectory, if direct to surface instead of orbit, will most likely not allow aborting the landing. If they land in a bad dust storm, solar won't work (too dark), and EVA activity gets dangerous due to poor visibility, even with lights. They have only as long as the ship's batteries will last to get the nuclear power plant up and running. Failure is death.
GW

SpaceNut · 2019-10-19 15:48:07

louis wrote:

So that's 200 tons mass to generate 1 Mwe with 100 KP Units - even before you've added in all the additional equipment required. It's way more than a PV system requires. But it will create huge demands on the pioneers in terms of activating them all.
SpaceNut wrote:
Assembly of the core
https://cdn.mos.cms.futurecdn.net/icPZu … 650-80.jpg
https://cdn.mos.cms.futurecdn.net/vC5XT … 650-80.jpg
Here is the answer for nuclear in that Krusty is a 10-kWe machine just 11 feet (3.4 meters) tall, and the reactor component would be the size of an old-school metal garbage can. With shielding, the entire 10-kWe reactor would weigh about 4,400 lbs. (2,000 kilograms). One can also use the water we are taking with us for an extra shadow shielding with what we are bringing. You only need 1 on each ship to take care of the energy required once on mars...that is the safety net for dust storms which block at 100% and allows for energy that is less than all of the solar that a day would recieve in a good dust free day.

Why are you still trying to take all units shielded, which is not at all what you need to do for the Krusty as these are only required to have on the powered up units on ships carrying crew for safety of dust out storms and for minimum cargo protection if they are unattended. All others can be later moved robotically lowered to the ground by crane and rovered to the place that is prepared for them. Connect them up in there hole or berm as per layout interconnections and move away. Active by remote and measure the levels and place markers. If levels are need to be lower a secondary berm can be moved into place by robotic dozer and a retest for levels done with new markers.

1Mwe solar needs to be designed for 5 to 7 Mwe for the array to produce the continous power that the nuclear solution can give you even after all of the power wall, batteries on the fins extra wiring for each array section to balancing nodes to allow for the supply to be regulated accross the power grid. The higher power required by each unit that is a dc power source means more convertor mass for each item and with power going up so does there mass. Thats also why we need to create the ac grid on mars as we have here on mars for all of the equipment to be designed closer to off the shelf.

louis · 2019-10-19 16:43:36

It's difficult trying to pin down what the nukists are proposing...

So, if you are using KP units without shielding, you're saying they need to be deployed on the surface with berms around them...well that is a tremendous logistical effort.

So these units have no packaging on board? They aren't secured in to frames on the Starship as others have suggested?

The object of the exercise is to provide energy for the base, for transport and exploration and for propellant production PV plus methane can cover all that.

PV for 1 Mwe continuous equivalent does not require x 5 to 7 that amount in PV. We expand the propellant production facility on the PV Plus solution, so we can better from peak solar without needing to store it. That's extra mass but only a few tons, nothing like 170-220 tons required for nuclear (without any additional PV and batteries you might still wish to bring along).

I am always happy to add 30% to the mass of the PV system itself to account for all the additional electrical equipment required.

SpaceNut wrote:

Why are you still trying to take all units shielded, which is not at all what you need to do for the Krusty as these are only required to have on the powered up units on ships carrying crew for safety of dust out storms and for minimum cargo protection if they are unattended. All others can be later moved robotically lowered to the ground by crane and rovered to the place that is prepared for them. Connect them up in there hole or berm as per layout interconnections and move away. Active by remote and measure the levels and place markers. If levels are need to be lower a secondary berm can be moved into place by robotic dozer and a retest for levels done with new markers.
1Mwe solar needs to be designed for 5 to 7 Mwe for the array to produce the continous power that the nuclear solution can give you even after all of the power wall, batteries on the fins extra wiring for each array section to balancing nodes to allow for the supply to be regulated accross the power grid. The higher power required by each unit that is a dc power source means more convertor mass for each item and with power going up so does there mass. Thats also why we need to create the ac grid on mars as we have here on mars for all of the equipment to be designed closer to off the shelf.

Last edited by louis (2019-10-19 17:30:12)

SpaceNut · 2019-10-19 16:56:57

I am still trying to figure out what plan is being used....
A. 2 cargo that land and start manufacturing enough fuel for a starship that will come on the next launch cycle
B. 2 cargo that land and start manufacturing enough fuel with 2 more cargo and a crewed starship that will come on the next launch cycle
C. 2 cargo that land and start manufacturing enough propellant for a crew that lands with them.

Each has different requirements for power, fuel creation time and risk mitigation safety requirements.

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