ISRU propellant production - energy requirement for the BFR?

SpaceNut · 2019-10-06 18:59:01

the kilowatt reactor is not hundreds of tons for the... 1,000kg is 1 tonnes

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

The prototype KRUSTY 1 kWe Kilopower reactor weighs 134 kg and contains 28 kg of 235U. The space rated 10 kWe Kilopower for Mars is expected to mass 1500 kg in total (with a 226 kg core) and contain 43.7 kg of 235U

SpaceNut wrote:

Power consumption to make methane in this article:
https://www.inverse.com/article/21492-s … ction-mars

https://aerospaceamerica.aiaa.org/depar … seriously/

https://fortune.com/2018/01/19/nasa-spa … r-reactor/

https://ntrs.nasa.gov/archive/nasa/casi … 001430.pdf
Potential Improvements to the Nuclear Safety and Launch Approval Process for Nuclear Reactors Utilized for Space Power and Propulsion Applications

https://ntrs.nasa.gov/archive/nasa/casi … 012354.pdf

https://ntrs.nasa.gov/archive/nasa/casi … 005435.pdf
The Kilopower Reactor Using Stirling TechnologY (KRUSTY) Nuclear Ground Test Results and Lessons Learned

Nothing to see here curtiousy of Oldfart1939
https://ntrs.nasa.gov/archive/nasa/casi … 011723.pdf

kbd512 · 2019-10-06 21:01:02

Louis,

I don't have a mass estimate because I don't have anything more than cursory design specifications from SpaceX on their giant new rocket that's never flown, much like SLS.

If their rocket requires 1,100t of propellant, then the propellant production plant must produce at a minimum rate of 1.046kg of propellant per second to produce 1,100t of propellant in 730 days, not accounting for boil-off or other losses.

The only mass figures I can provide for propellant production come from commercial water electrolysis O2/H2 production plants, that have known production rates and masses. I have already provided that info in other posts on this forum, so I'm not going to repeat it here. A H2 plant that could produce enough H2 for a LOX/LH2 fueled ship to leave Mars after 730 days would weigh about 30t. Oddly enough, it also requires about 1MWe of continuous power. The point is that nobody has ever built such a LOX/LCH4 plant at the scale required, and therefore it's never been tested. In contrast, those H2 plants that I referenced are in use around the world as I write this, so we know exactly how they'll perform.

You've got to admit that if transporting 100 reactors to the surface is too challenging, then transporting thousands of solar panels and connecting them in arrays is an even more daunting logistical challenge. All the challenges you listed don't magically go a way for solar power, they're just an order of magnitude more difficult and time consuming due to the size of what must be constructed and the total number of pieces. 1,000 piece puzzles aren't faster or easier to complete than 100 piece puzzles.

Kilopower Challenge Answered - For The 10th Time
Kilopower is made from Aluminum (radiators), Steel (containing Sodium metal for coolant in the heat pipes), Copper & Iron (Stirling engines), Beryllium Oxide (reflector), Uranium-Molybdenum alloy (core material), Boron Carbide (single control rod), Tungsten (High-Z shielding on top of the core), Lithium-Hydride (Low-Z shielding on top of the core). There are no electronics in the reactor, but the single control rod servo is electrically operated. It requires a power source equivalent to a single D cell battery for operation. Since there are no electronics required or included for operation, there are no electronic components that can fail.

If the entire heat removal system was removed from the reactor while it was operating at 100% of its rated output, temperature would rise to about 1100C over the course of an hour and then drop back down to 800C over the next hour or so, which is the reactors equilibrium temperature that the reactor operates at if power is not taken off the core in the form of thermal transfer to power removal / generation equipment (radiators and Stirling engines). They know this because they actually tested this by entirely removing the heat transfer equipment while the reactor was operating at full power. You'd know all that if you read what I posted or the documents and interviews with the design team that I also posted about, but you didn't because you anti-nuclear enthusiasts have religious experiences every time someone proposes something that involves the word "nuclear".

Storage
The "storage" of a Kilopower reactor is pretty simple. You strap or bolt it down, like any other piece of cargo. The Bigelow BEAM inflatables have nearly the exact same mass as a 10kWe reactor. The reactor was designed to be partially disassembled if you want to make extra, extra sure it can never "turn on". By removing the removable reflector from the reactor, there isn't sufficient neutron reflection, or activity, for it to ever "go critical", with or without the control rod inserted. It's almost as if it was "designed" that way. It's nothing more than a lump of really heavy metal at that point, roughly the same size and shape as a large coffee can (40cm in diameter x 50cm in length) and roughly the same weight as a cast iron big block V8 engine (for the entire core, the fuel is only 44kg). All the rest of the mass is radiators / generators / shielding. The radiator panels were also designed to be removable for ease of transport.

Deployment
The reactor will have to be craned off the ship, just like any other piece of cargo, be it a rover or a solar array or a battery or a habitat module. Once the reactor is on the ground, a rover can carry the reactor to where it will be emplaced. If the rover doesn't work, then there will be no power, irrespective of whether or not the power system is solar or nuclear. The reactor will then be partially buried in a hole about 50cm in diameter and 1.5m deep. If you can't drill that deep, then you have no ability to drill to obtain water for return propellant, either.

Cabling
Since there are only 100 of these reactors, versus thousands of solar panels, strings of 5 to 10 reactors can be connected to a central power transformer. The power from the reactors is already AC power, so only step-up / step-down of voltage and/or amperage need be performed using an ordinary transformer. That means no power inverter or other things controlled by microchips are required.

Safety Issues
Don't play near reactors when they're operating. Don't sleep with nuclear power sources at night. Real life is not a Hollyweird movie. Hollyweird movies are to real life what a wet fart is to an actual aerospace engineering exercise. I think that just about covers it.

Notes:
1. You've never once provided questions about actual safety issues, so it's impossible to address something that you've never brought up. If you have actual safety issues that you'd like me to address, then please formulate an actual question about an actual safety issue.

2. Don't regurgitate Hollyweird lunacy that you've watched in a movie at some point in your life and expect me to address the magical thinking about how nuclear power works that comes from people who are doing drugs most of the time and lack the mathematical capability to balance their checkbook, much less operate a nuclear power plant.

3. I'd love to discuss the operational aspects of using nuclear power, so please put forth some effort to ask valid questions or make valid arguments about things you've noted are operational issues. No more hiding behind vague statements that have no actual meaning.

SpaceNut · 2019-10-07 20:41:44

https://ntrs.nasa.gov/archive/nasa/casi … 001421.pdf
An ISRU Propellant Production System to Fully Fuel a Mars Ascent Vehicle

https://nssdc.gsfc.nasa.gov/planetary/m … ssurf.html
A Crewed Mission to Mars...

https://ntrs.nasa.gov/archive/nasa/casi … 004427.pdf
Methane Propulsion Elements for Mars

https://tfaws.nasa.gov/files/2_ISRU-Soi … S-2018.pdf
ISRU Soil Water Extraction:Thermal challenges

https://ttu-ir.tdl.org/bitstream/handle … sequence=1
Evaluation of CO Evaluation of CO 2 Adsorber, Sabatier Reactor, and Solid Adsorber,and Solid Oxide Stack for Consumable, Propellant, and Power Oxide Stack for Consumable, and Power Production – Potential in ISRU

http://www.marspapers.org/paper/Zubrin_1991.pdf

SpaceNut · 2019-10-07 21:25:59

One problem is the duration that we have to produce fuel within, as we will need a 9 month transit and one month of margin, ISRU production must take place in 16 months (480 days) stay on the surface as it took 6 months to get there for the mars cycle of 2 years 7 weeks for alignment.
That pushes up the power requirements due to the short production time....

kbd512 · 2019-10-07 21:27:43

SpaceNut,

There will also be significant power requirements to keep that much propellant cold over such a long period of time.

SpaceNut · 2019-10-07 22:48:09

I think after getting the numbers for the energy for the active cooling system the mass will be the next issue for the ability.

https://www.ccohs.ca/oshanswers/chemica … ogen1.html

http://www.operoenergy.com/products-and … as-plants/

https://www.hydrogen.energy.gov/pdfs/90 … ession.pdf

https://www.sciencedirect.com/topics/en … ic-cooling

https://ntrs.nasa.gov/archive/nasa/casi … 016225.pdf

https://cryohub.eu/public/downloads/2G_ … torage.pdf

louis · 2019-10-08 00:27:31

Pay attention Spacenut! To power the propellant production facility for a Starship, some analysts say you need 1 Mwe continuous.

That would require 100 Kilopower Units (at 10 Kw each). Each unit will weigh at least 1,500 Kg (1.5 tons), so 100 will weigh at least 1500 kgs (that's without shielding or packaging).

One unit might power the base, but that would be about it.

The paper you cite later on how much energy is required to make the return propellant states that return propellant will mass a paltry 29.7 tons!!!

"The total propellant needed for ascent is 7.0 mT of methane and 22.7 mT of oxygen."

That is clearly nothing to do with a Starship which requires perhaps 30 times as much - something like 1000 tons.

SpaceNut wrote:

the kilowatt reactor is not hundreds of tons for the... 1,000kg is 1 tonnes
https://en.wikipedia.org/wiki/Kilopower
The prototype KRUSTY 1 kWe Kilopower reactor weighs 134 kg and contains 28 kg of 235U. The space rated 10 kWe Kilopower for Mars is expected to mass 1500 kg in total (with a 226 kg core) and contain 43.7 kg of 235U
SpaceNut wrote:
Power consumption to make methane in this article:
https://www.inverse.com/article/21492-s … ction-mars
https://aerospaceamerica.aiaa.org/depar … seriously/
https://fortune.com/2018/01/19/nasa-spa … r-reactor/
https://ntrs.nasa.gov/archive/nasa/casi … 001430.pdf
Potential Improvements to the Nuclear Safety and Launch Approval Process for Nuclear Reactors Utilized for Space Power and Propulsion Applications
https://ntrs.nasa.gov/archive/nasa/casi … 012354.pdf
https://ntrs.nasa.gov/archive/nasa/casi … 005435.pdf
The Kilopower Reactor Using Stirling TechnologY (KRUSTY) Nuclear Ground Test Results and Lessons Learned

louis · 2019-10-08 00:32:16

The NASA paper cited by Spacenut is for production of under 30 tons of propellant - a tiny amount - and so is irrelevant to the, as yet, only Mars Mission really on the table - the Starship mission.

I suspect that a proper review of energy requirements for the Starship propellant at around 1000 tons could be less than the 1 Mwe given by one detailed analysis, but it is going to be a v. large amount and we might as well look at a worst case scenario. It's not just the chemical processes, it's all the mining, transport and pumping requirements as well.

At 1 Mwe 100 Kilopower units are required.

kbd512 wrote:

SpaceNut,
There will also be significant power requirements to keep that much propellant cold over such a long period of time.

louis · 2019-10-08 01:17:20

kbd512 wrote:

Louis,
I don't have a mass estimate because I don't have anything more than cursory design specifications from SpaceX on their giant new rocket that's never flown, much like SLS.
If their rocket requires 1,100t of propellant, then the propellant production plant must produce at a minimum rate of 1.046kg of propellant per second to produce 1,100t of propellant in 730 days, not accounting for boil-off or other losses.
The only mass figures I can provide for propellant production come from commercial water electrolysis O2/H2 production plants, that have known production rates and masses. I have already provided that info in other posts on this forum, so I'm not going to repeat it here. A H2 plant that could produce enough H2 for a LOX/LH2 fueled ship to leave Mars after 730 days would weigh about 30t. Oddly enough, it also requires about 1MWe of continuous power. The point is that nobody has ever built such a LOX/LCH4 plant at the scale required, and therefore it's never been tested. In contrast, those H2 plants that I referenced are in use around the world as I write this, so we know exactly how they'll perform.
You've got to admit that if transporting 100 reactors to the surface is too challenging, then transporting thousands of solar panels and connecting them in arrays is an even more daunting logistical challenge. All the challenges you listed don't magically go a way for solar power, they're just an order of magnitude more difficult and time consuming due to the size of what must be constructed and the total number of pieces. 1,000 piece puzzles aren't faster or easier to complete than 100 piece puzzles.I don't accept the absurd idea that we will be putting in place the sort of stormproof steel frames for PV power that you see on Earth. The max wind power on Mars ever recorded was the equivalent of 16 MPH on Earth. We'll be laying down ground PV in my view and that takes seconds per Kw rating not hours.

I quoted this link on another thread:

https://www.bbc.co.uk/news/uk-wales-sou … s-41443312

Quote from the article: "The Rapid Roll system allows flexible solar panels to be unrolled like a carpet from a trailer in two minutes."

Clearly that is the sort of system that the Space X team will be looking at in my view. That's 2 mins unloading time for 11 Kws (max presumably) on Earth.

There is no shortcut like that available for deployment of anything up to 100 Kilopower units at 1.5 tons a time (minimum).

Kilopower Challenge Answered - For The 10th Time
Kilopower is made from Aluminum (radiators), Steel (containing Sodium metal for coolant in the heat pipes), Copper & Iron (Stirling engines), Beryllium Oxide (reflector), Uranium-Molybdenum alloy (core material), Boron Carbide (single control rod), Tungsten (High-Z shielding on top of the core), Lithium-Hydride (Low-Z shielding on top of the core). There are no electronics in the reactor, but the single control rod servo is electrically operated. It requires a power source equivalent to a single D cell battery for operation. Since there are no electronics required or included for operation, there are no electronic components that can fail.
If the entire heat removal system was removed from the reactor while it was operating at 100% of its rated output, temperature would rise to about 1100C over the course of an hour and then drop back down to 800C over the next hour or so, which is the reactors equilibrium temperature that the reactor operates at if power is not taken off the core in the form of thermal transfer to power removal / generation equipment (radiators and Stirling engines). They know this because they actually tested this by entirely removing the heat transfer equipment while the reactor was operating at full power. You'd know all that if you read what I posted or the documents and interviews with the design team that I also posted about, but you didn't because you anti-nuclear enthusiasts have religious experiences every time someone proposes something that involves the word "nuclear".

Implying that something is "intrinsically" safe isn't really the right attitude for Mars in my view.

They have spent years on development of Kilopower and the reason is that the radioactive nature of the device means that they have to incorporate lots of failsafe mechanisms to ensure it can operate safely and/or shut down safely without human intervention. But that doesn't mean you can assume it will operate as planned. My understanding is you can't have people working near them unshielded. So that in itself will create issues for how you manage their deployment and the base.

Storage
The "storage" of a Kilopower reactor is pretty simple. You strap or bolt it down, like any other piece of cargo. The Bigelow BEAM inflatables have nearly the exact same mass as a 10kWe reactor. The reactor was designed to be partially disassembled if you want to make extra, extra sure it can never "turn on". By removing the removable reflector from the reactor, there isn't sufficient neutron reflection, or activity, for it to ever "go critical", with or without the control rod inserted. It's almost as if it was "designed" that way. It's nothing more than a lump of really heavy metal at that point, roughly the same size and shape as a large coffee can (40cm in diameter x 50cm in length) and roughly the same weight as a cast iron big block V8 engine (for the entire core, the fuel is only 44kg). All the rest of the mass is radiators / generators / shielding. The radiator panels were also designed to be removable for ease of transport.

Going by photos of the KP units, it looks to me like they will need specialist packaging, more so than a Bigelow unit for instance and definitely more than a roll of flexible PV.

Deployment
The reactor will have to be craned off the ship, just like any other piece of cargo, be it a rover or a solar array or a battery or a habitat module. Once the reactor is on the ground, a rover can carry the reactor to where it will be emplaced. If the rover doesn't work, then there will be no power, irrespective of whether or not the power system is solar or nuclear. The reactor will then be partially buried in a hole about 50cm in diameter and 1.5m deep. If you can't drill that deep, then you have no ability to drill to obtain water for return propellant, either.

I think a roll of PV array will be much more manageable. You might be able to zip wire them down or use a chute and have them bounce off an inflatable bed on to the Mars surface. Just an idea - but you certainly couldn't do that with a KP unit.

Cabling
Since there are only 100 of these reactors, versus thousands of solar panels, strings of 5 to 10 reactors can be connected to a central power transformer. The power from the reactors is already AC power, so only step-up / step-down of voltage and/or amperage need be performed using an ordinary transformer. That means no power inverter or other things controlled by microchips are required.

Fair enough, but still a lot of cabling work especially if they are located well away from the habs and work areas. Cabling could be integrated into the PV systems more readily I would suggest.

Safety Issues
Don't play near reactors when they're operating. Don't sleep with nuclear power sources at night. Real life is not a Hollyweird movie. Hollyweird movies are to real life what a wet fart is to an actual aerospace engineering exercise. I think that just about covers it.

I accept there is hysteria about radiation threats - mixing up of the effects of a nuclear explosion and a nuclear power device - but on the other hand we all know that the nuclear power industry has to be extremely cautious about safety. There are real threats to human health and safety, and that is one of the things the KP unit is being designed to address. These safety issues are far more complex and significant than in relation to PV power.

Notes:
1. You've never once provided questions about actual safety issues, so it's impossible to address something that you've never brought up. If you have actual safety issues that you'd like me to address, then please formulate an actual question about an actual safety issue.
2. Don't regurgitate Hollyweird lunacy that you've watched in a movie at some point in your life and expect me to address the magical thinking about how nuclear power works that comes from people who are doing drugs most of the time and lack the mathematical capability to balance their checkbook, much less operate a nuclear power plant.
3. I'd love to discuss the operational aspects of using nuclear power, so please put forth some effort to ask valid questions or make valid arguments about things you've noted are operational issues. No more hiding behind vague statements that have no actual meaning.

1. Well I think I have. The KP unit will be radioactive to a degree that could harm human health when activated is my understanding and therefore humans cannot be allowed to work close to them. The KP unit is being designed to shut down automatically in the event of a meltdown. That means there is the risk of a meltdown.

2. I don't base my opinions re a Mars base on Hollywood movies (and that goes for that ridiculous dust storm in "The Martian" as well as "The China Syndrome").

3. I don't think we have enough info on how the KP units will operate to tell. I was struck by the phrase "hands on" in the publicity about the KP unit development - they needed to ensure hands-on work could be undertaken safely was my reading but it was difficult to say whether this meant during the development work or operational maintenance. It sounded to me like the unit might at some point need hands on maintenance. That kind of goes against its billing as being an automated system - so I am not clear on that point I am not sure what is being referred to. Until we have full details of how a KP unit will work, how it will be offloaded, located, deployed and possibly shielded, we won't know all the operational issues. Not my fault.

Oldfart1939 · 2019-10-08 08:03:14

Louis-

You seem to have this irrational fear of anything involving radiation. In my long career as a chemist, I've worked with a lot of things that terrify me more than working with radioactive isotopes, and probably #1 on my list is Phosgene. In spite of it being an insidious poisonous gas, I handled a lot of it during my 50 year career. I worked with C14, Tritium, and I forget which isotope of radioIodine. The keys to working with hazardous materials are (1) knowledge, and (2) use of proper PPE (personal protective equipment). As a graduate student, I was the teaching assistant for Professor Victor Ryan at the University of Wyoming. Professor Ryan was the professor of Nuclear Chemistry, and I worked with him in the course of teaching Physical Chemistry Laboratory; the key experiment I recall was measuring the decay lifetime of Neutron Irradiated Silver, and it was done by placing a number of silver coins in the critical mass nuclear reactor, and doing a neutron bombardment of the samples. I was allowed to operate a full critical mass Thorium based reactor as a Grad Student, with Professor Ryan standing beside me. It was no bigger deal than driving a car. This reactor is, sadly, no longer there because of the actions of Green Freaks, worried about anything NUCLEAR being on the campus. It was retired and dismantled in the late 1980s.

My advice is: GET OVER IT!!

Last edited by Oldfart1939 (2019-10-08 11:18:49)

GW Johnson · 2019-10-08 11:36:13

Rodger:

I've told Louis at least twice, in other places on these forums, exactly how you shield a Kilopower unit. He just doesn't want to know.

You set it up, troubleshoot your connections, and then bulldoze a berm around it. Then you turn it on, and never go inside that berm again. Until the end of its useful life many years into the future: bulldoze the berm over it to bury it.

The active word here is "bulldoze". A settlement on Mars or the moon is going to need the space-rated rechargeable battery analogs of Earthly bulldozers, front end loaders, and such like. Have you noticed nobody is working on them?

NASA should be coordinating the timely making-ready of all these things, but is not! That's how I know the Artemis mission plan is just another flags-and-footprint stunt plus some corporate welfare, not a real base or settlement. If it flies at all.

GW

SpaceNut · 2019-10-08 18:14:41

Louis, You have seemingly forgotten how to scale up numbers when they are given as a means to see if we are even close to your projected video reference numbers not engineered in any reference documents.

lowest yield regolith, a full ISRU system would weigh 1.7 mT to produce 7.0 mT of methane and 22.7 mT of oxygen in a 16 months (480 days) period continuosly 24x7 until we leave. curiosity rover uses a power source that produces 110We and ~2KW thermal so the system power is oxygen-only ISRU system, is the simplest system 0.9 mT and 34 kW and methane system is 1.7 mT and power to 52 kW every hour. Since men are involved we need life support oxygen and water which makes for a total system of 2.2 mT and 80 kW

1200 mT is the fully loaded starship though we know that we do not need all that fuel as the payload mass going home is going to be less.
30 mT makes for a multiplier of 40
total mass no life support scaled up 680 mT for the system to process co2 and water into the fuel for the trip home..
total energy for fuel manufacturing no life support 2,080 kw from the constant supply power..

add in life support and 36mT plus 1,360 kw more

which brings the total mass to 716mT and power of 3,440 kw

kbd512 · 2019-10-08 19:30:56

SpaceNut,

If we're going to try to do this in a single cycle, then I think we're going to need a bigger rocket, or a real interplanetary transport system that consists of a ship that stays in space. If we do that instead of trying to manufacture 100's of tons of propellant from scratch using a solar array the size of a commercial solar farm here on Earth or MW-class nuclear reactors, then our power requirements plummet. That small reusable lander that GW talked about is looking better and better all the time.

SpaceNut · 2019-10-08 20:39:48

Moxie for life support air is still waiting to get a real mars test and if it scales up well its mass and power levels are expected to drop as to compared to what we started with in the above referenced document...

There are some improvements in the methane but still this is the biggest part of any mars refueling system to crack....

louis · 2019-10-09 01:48:50

A constant power requirement of 3.4 Mwes doesn't sound right to me. Way over the top I would suggest.

I have never seen a reliable indication of how much propellant-fuel is required for the return journey of a Starship. Have you?

SpaceNut wrote:

Louis, You have seemingly forgotten how to scale up numbers when they are given as a means to see if we are even close to your projected video reference numbers not engineered in any reference documents.
lowest yield regolith, a full ISRU system would weigh 1.7 mT to produce 7.0 mT of methane and 22.7 mT of oxygen in a 16 months (480 days) period continuosly 24x7 until we leave. curiosity rover uses a power source that produces 110We and ~2KW thermal so the system power is oxygen-only ISRU system, is the simplest system 0.9 mT and 34 kW and methane system is 1.7 mT and power to 52 kW every hour. Since men are involved we need life support oxygen and water which makes for a total system of 2.2 mT and 80 kW
1200 mT is the fully loaded starship though we know that we do not need all that fuel as the payload mass going home is going to be less.
30 mT makes for a multiplier of 40
total mass no life support scaled up 680 mT for the system to process co2 and water into the fuel for the trip home..
total energy for fuel manufacturing no life support 2,080 kw from the constant supply power..
add in life support and 36mT plus 1,360 kw more
which brings the total mass to 716mT and power of 3,440 kw

louis · 2019-10-09 01:51:58

Of course you can shield it. But it will add mass to the 1.5 tons. Even at 1.5 tons, the nuclear power system for 1 Mwe constant power output is going to be at least 150 tons, for 100 units (without associated equipment - I normally add on 30% for that).

GW Johnson wrote:

Rodger:
I've told Louis at least twice, in other places on these forums, exactly how you shield a Kilopower unit. He just doesn't want to know.
You set it up, troubleshoot your connections, and then bulldoze a berm around it. Then you turn it on, and never go inside that berm again. Until the end of its useful life many years into the future: bulldoze the berm over it to bury it.
The active word here is "bulldoze". A settlement on Mars or the moon is going to need the space-rated rechargeable battery analogs of Earthly bulldozers, front end loaders, and such like. Have you noticed nobody is working on them?
NASA should be coordinating the timely making-ready of all these things, but is not! That's how I know the Artemis mission plan is just another flags-and-footprint stunt plus some corporate welfare, not a real base or settlement. If it flies at all.
GW

louis · 2019-10-09 01:55:36

Take it up with NASA. They are the ones spending years on development to address radiation safety issues, not me!

Not everyone on a Mars Mission can be a trained chemist or nuclear physicist and it's not going to be a lab experiment. Everything needs to work in the rough and tumble of a starter settlement.

Oldfart1939 wrote:

Louis-
You seem to have this irrational fear of anything involving radiation. In my long career as a chemist, I've worked with a lot of things that terrify me more than working with radioactive isotopes, and probably #1 on my list is Phosgene. In spite of it being an insidious poisonous gas, I handled a lot of it during my 50 year career. I worked with C14, Tritium, and I forget which isotope of radioIodine. The keys to working with hazardous materials are (1) knowledge, and (2) use of proper PPE (personal protective equipment). As a graduate student, I was the teaching assistant for Professor Victor Ryan at the University of Wyoming. Professor Ryan was the professor of Nuclear Chemistry, and I worked with him in the course of teaching Physical Chemistry Laboratory; the key experiment I recall was measuring the decay lifetime of Neutron Irradiated Silver, and it was done by placing a number of silver coins in the critical mass nuclear reactor, and doing a neutron bombardment of the samples. I was allowed to operate a full critical mass Thorium based reactor as a Grad Student, with Professor Ryan standing beside me. It was no bigger deal than driving a car. This reactor is, sadly, no longer there because of the actions of Green Freaks, worried about anything NUCLEAR being on the campus. It was retired and dismantled in the late 1980s.
My advice is: GET OVER IT!!

elderflower · 2019-10-09 07:39:17

A reactor inside a berm or in a pit can have a support structure with insulation to protect the substrate. When you bury it the residual heat will no longer be lost to atmosphere and will warm the ground. If the ground has ice under it or is loose stuff bound together with ice, you can have an unstable situation. Your reactor will sink through an ice mass pretty quickly.
Spent reactor fuel continues to produce a lot of heat and the fuel assemblies are kept under water for years on earth.

GW Johnson · 2019-10-09 13:36:42

If I am not mistaken, a pit or a berm is exactly what NASA has in mind for using Kilopower. There's the reactor itself, integral with heat piping, that in turn leads to a closed-loop Stirling engine (at least I think it is a Stirling, it is some sort of heat engine regardless) driving an electric generator.

It's about 10 KWe output at full power, and 25% thermal efficiency. That means there is about 30 KWth waste heat to deal with. The Kilopower setup has a coolant loop and a big radiator pointed at the sky to handle that. You put all this in the pit or inside the berm, as I understand it. Only the electric cable comes out.

If your berm is spiral in shape, you don't even have to finish closing it off. Just barricade the entrance. The spiral shape precludes straight-line view of the hazard.

This thing was intended to function on Mars, on the moon, or even just out in space. Same package does all these applications. Fairly versatile, that is. I kinda like it. I just wish there was also another one scaled-up under development; say nearer 100 KWe than 10 KWe. There was one for a while, but no longer. The attention is now all on the 10 KWe Kilopower.

GW

Last edited by GW Johnson (2019-10-09 13:40:54)

louis · 2019-10-09 14:42:49

Not really my job to argue for Kilopower but does it really make sense to put them on the surface? - why not spread them across 5 Starships (20 each) that aren't carrying humans back to Earth and operate them from within the Starships. Wouldn't that avoid a helluva lot of grief with unloading, unpacking, creating berms and all the rest...?

GW Johnson wrote:

If I am not mistaken, a pit or a berm is exactly what NASA has in mind for using Kilopower. There's the reactor itself, integral with heat piping, that in turn leads to a closed-loop Stirling engine (at least I think it is a Stirling, it is some sort of heat engine regardless) driving an electric generator.
It's about 10 KWe output at full power, and 25% thermal efficiency. That means there is about 30 KWth waste heat to deal with. The Kilopower setup has a coolant loop and a big radiator pointed at the sky to handle that. You put all this in the pit or inside the berm, as I understand it. Only the electric cable comes out.
If your berm is spiral in shape, you don't even have to finish closing it off. Just barricade the entrance. The spiral shape precludes straight-line view of the hazard.
This thing was intended to function on Mars, on the moon, or even just out in space. Same package does all these applications. Fairly versatile, that is. I kinda like it. I just wish there was also another one scaled-up under development; say nearer 100 KWe than 10 KWe. There was one for a while, but no longer. The attention is now all on the 10 KWe Kilopower.
GW

GW Johnson · 2019-10-09 16:32:42

Two very good reasons that you cannot turn on a KP unit inside a landed Starship, Louis.

(1) You start one of those inside a landed Starship, then you cannot ever go back inside that vehicle for any purpose, just like you cannot ever re-enter the containment vessel in a power plant. That just lost you a Starship, even if this scheme was workable.

(2) This scheme is NOT workable at all! The waste heat radiator CANNOT work within any enclosed space. Period. End of issue. It MUST see the sky as its heat sink. That is what it was designed to do. You would never have even suggested this scheme, if you had the faintest understanding of thermodynamics.

Just bulldoze the berms and get on with the war.

And go look up how a heat engine works on Wikipedia. Then look up "thermodynamics". And before you come back at me with some snide comment, be aware that I majored in this stuff in engineering school, and I used it every single day in a 20-year aerospace defense weapons career, along with a whole lot of other stuff, including aerodynamics from 5 mph to Mach 25.

GW

Last edited by GW Johnson (2019-10-09 16:40:22)

louis · 2019-10-09 16:36:23

1. If you emptied the Starship of its other cargo, what's the problem? You weren't intending to fly it back to Earth...

2. Well that seems a more serious objection...I am v. happy to hear that because it means PV wins hands down!

GW Johnson wrote:

Two very good reasons, Louis.
(1) You start one of those inside a landed Starship, then you cannot go back inside that vehicle for any purpose, just like you cannot re-enter the containment vessel in a power plant. That just lost you a Starship, even if it this scheme was workable.
(2) This scheme is NOT workable at all. The waste heat radiator CANNOT work within any enclosed space. Period. End of issue. It MUST see the sky as its heat sink. You would never have even suggested this if you had the faintest understanding of thermodynamics.
Just bulldoze the berms and get on with the war.
GW

SpaceNut · 2019-10-09 16:44:31

louis wrote:

Not really my job to argue for Kilopower but does it really make sense to put them on the surface? - why not spread them across 5 Starships (20 each) that aren't carrying humans back to Earth and operate them from within the Starships. Wouldn't that avoid a helluva lot of grief with unloading, unpacking, creating berms and all the rest...?
GW Johnson wrote:
If I am not mistaken, a pit or a berm is exactly what NASA has in mind for using Kilopower. There's the reactor itself, integral with heat piping, that in turn leads to a closed-loop Stirling engine (at least I think it is a Stirling, it is some sort of heat engine regardless) driving an electric generator.
It's about 10 KWe output at full power, and 25% thermal efficiency. That means there is about 30 KWth waste heat to deal with. The Kilopower setup has a coolant loop and a big radiator pointed at the sky to handle that. You put all this in the pit or inside the berm, as I understand it. Only the electric cable comes out.
If your berm is spiral in shape, you don't even have to finish closing it off. Just barricade the entrance. The spiral shape precludes straight-line view of the hazard.
This thing was intended to function on Mars, on the moon, or even just out in space. Same package does all these applications. Fairly versatile, that is. I kinda like it. I just wish there was also another one scaled-up under development; say nearer 100 KWe than 10 KWe. There was one for a while, but no longer. The attention is now all on the 10 KWe Kilopower.
GW

Was suggested and ignored was thought to only be on a crewed vehcle which is not what was said...

As for the waste heat we could reclaim it as that is what is being used for some of the other green energy machines here on earth.

GW Johnson · 2019-10-09 16:47:58

PV win hands down? No, it does not!!! Go look at the photos from Opportunity before and during the dust storm that killed it, using the website URL for the NASA document that I provided. NASA's own published data says your belief system about solar-only is BS.

I know you don't like this answer, but your only truly practical power combination on Mars or the moon is a nuclear baseline plus a lot of solar during the day when demand is higher than baseline. Better get used to that! It's true, despite how fervently you wish to disbelieve it.

As Musk gets closer to sending one of his Starships to Mars, and actually begins contemplating what is really needed there, he will agree with me, not you. There simply is no other known technological answer for Mars. Or the moon. It's even worse on the moon with that 14-day-long night. When the sun don't shine, there is NO solar power.

GW

SpaceNut · 2019-10-09 16:49:35

GW Johnson wrote:

Two very good reasons that you cannot turn on a KP unit inside a landed Starship, Louis.
(1) You start one of those inside a landed Starship, then you cannot ever go back inside that vehicle for any purpose, just like you cannot ever re-enter the containment vessel in a power plant. That just lost you a Starship, even if this scheme was workable.
(2) This scheme is NOT workable at all! The waste heat radiator CANNOT work within any enclosed space. Period. End of issue. It MUST see the sky as its heat sink. That is what it was designed to do. You would never have even suggested this scheme, if you had the faintest understanding of thermodynamics.
Just bulldoze the berms and get on with the war.
And go look up how a heat engine works on Wikipedia. Then look up "thermodynamics". And before you come back at me with some snide comment, be aware that I majored in this stuff in engineering school, and I used it every single day in a 20-year aerospace defense weapons career, along with a whole lot of other stuff, including aerodynamics from 5 mph to Mach 25.
GW

Add a control line down to the base of the ship to isolate or retract the rods. Wait until cool and bring dosimiter and giger counters to test the radiation levels is all that we need. slide it along a rail until its got the readings that you need from a distance from the unit. Bring portable shields to isolate crew from high levels as barriers. We will have tested the unit on earth before repacking it on the ship so adding in an extra set of control wires for mars should not be any issue.

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