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#1 2003-10-02 09:36:35

jabe
Banned
From: toronto Canada
Registered: 2003-10-02
Posts: 24

Re: Nuclear power - How much is needed?

My main reason for asking is I'm trying to develop a high school physics assignment to talk about masses needed to get to Mars and I want a range of masses to have the students discuss pros and cons of taking certain amount of mass along.  With costs obviously playing a key role.

I have done a fair amount of reading about getting to Mars and the need for nuclear power.  (both as a source of heat/power for a nuclear rocket engine and a power source when on the planet)

Since the energy available on the surface is ideal for high transmission rates and  In-Situ creation of fuels for a return trip and for fuel for a martian "buggy" when we actually get there, the  more power available the better.

So my question is kind of open ended.
Are there any specifics of what MINIMUM requirement would be needed and what amount would be good to have?
Since greater power will require more shielding, there has to be a happy medium for mass consideration. 
Any specifics or resources to read would be greatly appreciated.

cheers

John Berrigan

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#2 2003-10-02 14:13:33

Ad Astra
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Registered: 2003-02-02
Posts: 584

Re: Nuclear power - How much is needed?

Most of the Mars missions that have called for nuclear power have specified using the SP-100, a 100 kW reactor.


Who needs Michael Griffin when you can have Peter Griffin?  Catch "Family Guy" Sunday nights on FOX.

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#3 2003-10-02 21:49:52

RobS
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From: South Bend, IN
Registered: 2002-01-15
Posts: 1,701
Website

Re: Nuclear power - How much is needed?

The Case for Mars appears to be inconsistent, talking about 100 kilowatts in one place and 75 kilowatts in another. One place that gives details specifies a 3.5 tonne, 100 kilowatt electrical power source. It also says the conversion will use thermocouples (thermionic conversion?) that are 5% efficient, thus the thermal power output is 2,000 kw.

The Michael Duke "Lunar Reference Strategy" article I often quote speaks of a one tonne solar or nuclear power source that produces 25 kw. It sounds like he's assuming a 1 tonne reactor can make 25 electrical kilowatts.

A recent article I read somewhere says the new thermionic converters may get far above 5%; 15% may be possible. This suggests a Duke-sized one tonne reactor may be able to put out 75 kw, which is more the size that Mars Direct needs. A Stirling engine can also convert thermal energy into electricity at 15 to 20% efficiency or maybe better; I am not sure. All this suggests to me that a 1-tonne, 500 thermal kilowatt reactor may be enough when the technology matures sufficiently (which it hasn't yet).

The energy need to run a four person base is not that high; maybe 10 kw or so. Mars Direct is designed to function on 5 kw solar power on the flight out. But running a Sabatier reactor takes energy because you have to crack CO2 into CO and oxygen. This takes something like 5 kilowatt-hours per kilogram of fuel you make. If you have to make 100 tonnes (100,000 kg) of fuel, that's 500,000 kilowatt-hours. A 100-kilowatt reactor puts out 2400 kilowatt-hours per day, so that means it makes roughly a half tonne of fuel per day and needs 200 days to make 100 tonnes.

        -- RobS

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#4 2003-10-03 10:50:32

Tyr
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Registered: 2002-09-14
Posts: 83

Re: Nuclear power - How much is needed?

here's an interesting link: http://www.inspi.ufl.edu/research/gcr/index.html

if you search for more sites on vapor core reactors, not to be confused with gas core nuclear rocket engines, you will discover some amazing possiblities for the future.

also of interest: http://www.ga.com/atg/sp/space.html

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#5 2003-10-06 08:22:38

jabe
Banned
From: toronto Canada
Registered: 2003-10-02
Posts: 24

Re: Nuclear power - How much is needed?

Thanks guys,
Appreciate the input.  Looks like the numbers are a "work in progress" so there are no hard and fast values.  Using a thermocoupler  with the reactor for energy transfer does seem the simplest solution..no moving parts so no maintenance (makes up for the relatively low conversion process).  The excess heat could probably could be used as "heat pump" as well if push comes to shove.

Regarding

The Case for Mars appears to be inconsistent, talking about 100 kilowatts in one place and 75 kilowatts in another. One place that gives details specifies a 3.5 tonne, 100 kilowatt electrical power source. It also says the conversion will use thermocouples (thermionic conversion?) that are 5% efficient, thus the thermal power output is 2,000 kw.

So the 100 kW is the electrical output energy of the reactor after the conversion?  Makes a big difference if they improve the efficiency of the conversion process they use.  A small improvement in the energy conversion can makes a huge difference in the amount of energy output.  Almost free energy if they have a fixed reactor design and then start trying different methods of conversion.
Is there a schematic somewhere of the type of reactor that they will use?  which leads to the question...  For the 3.5 t , 2,000 kW thermal reactor, how much urnanium/plutonium is that and what is its useful life span?  Then the big question...  How can it be safely brought into orbit to satisfy the nuclearphobic?  i.e. send reactor up with out the fuel..and then carry the fuel up in small amounts on various flights in a "sealed" container so if rocket does blow up nothing is released into the Earths atmosphere.
thanks again ..
John

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#6 2003-10-06 08:40:55

RobS
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From: South Bend, IN
Registered: 2002-01-15
Posts: 1,701
Website

Re: Nuclear power - How much is needed?

I have never seen a design for a reactor or details like what sort of fuel it would use. The Case for Mars, page 205, talks about a reactor with a 100 kw electrical output and a 2000 kw thermal output that would last ten years. It also says the reactor would weigh 4 tonnes. On page 93, the chart of masses to launch to Mars shows a 3.5 tonne reactor identified as 80 kw of electrical output. Possibly Zubrin wants a 100 kw reactor but Mars Direct was designed for an 80 kw reactor because of lack of mass.

Reactors are not radioactive until they are turned on, so the safest thing to do is assemble the entire reactor on Earth and not turn it on until you get to Mars. The fuel pellets can be encased in hard shells--including the reactor vessel itself--to prevent release of radioactive material in the event of a launch accident. You would not want to launch a little fuel at a time because they multiplies the number of launches that could fail, and then you have to handle the stuff in space, which would be tricky and require the launch of equipment into low earth orbit that could get radioactive and later reenter the atmosphere. Robert Dyck can comment on this further.

       -- RobS

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#7 2018-11-25 17:13:37

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 23,908

Re: Nuclear power - How much is needed?

bump great question

Fixed topic artifacts

The size of the power plant depends on the science, mission insitu level of implementation and so much more.

A realistic amount for a small crew of 6 seems to be about what we use in our homes (40KW hr a day) but that not counting energy requirement for life support of for transportation.

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#8 2018-11-25 21:26:15

kbd512
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Registered: 2015-01-02
Posts: 4,923

Re: Nuclear power - How much is needed?

I believe NASA has already answered this question with the KiloPower reactor system and documents have been posted in other topic threads indicating what the expected power consumption will be.  They intend to take 4 (40kWe) to 5 (50kWe) of these units to Mars to have redundancy, reduce power cable mass, and to produce enough power for a small base and a small LOX/LCH4 powered lander.

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#9 2018-11-26 01:09:45

louis
Member
From: UK
Registered: 2008-03-24
Posts: 7,087

Re: Nuclear power - How much is needed?

There is no Kilopower system. There is only experimentation to test out the Kilopower design.

kbd512 wrote:

I believe NASA has already answered this question with the KiloPower reactor system and documents have been posted in other topic threads indicating what the expected power consumption will be.  They intend to take 4 (40kWe) to 5 (50kWe) of these units to Mars to have redundancy, reduce power cable mass, and to produce enough power for a small base and a small LOX/LCH4 powered lander.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#10 2018-11-26 09:13:30

kbd512
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Registered: 2015-01-02
Posts: 4,923

Re: Nuclear power - How much is needed?

Louis,

There is no ITS, BFR, or Starship, either.  There is only experimentation to test out some design, whatever / whenever that becomes.  NASA actually built and operated their test fission reactor at rated thermal output at the Y-12 Nevada National Security Complex.  Starship, or whatever SpaceX calls it tomorrow after their next marketing ideation falls flat, still only exists in PowerPoint and nowhere else.  Right now, KiloPower is further along in its development path than everyone's favorite PowerPoint rocket is.  I can post a photo of KiloPower, rather than a PowerPoint graphic, because DOE and NASA already built it.  You can't post a photo of this new Starship because it doesn't exist.

Oh, look, there's KiloPower:

KiloPower - The fission reactor Louis wants to pretend doesn't exist

Welcome to the Kilopower Press Conference

Apparently NASA intends to offer it for sale to commercial users, too:

Lee Mason, NASA Kilopower overview and mission applications

Who would take 50 tons of batteries to Mars when 10 tons of reactors could get the job done?

The people who subscribe to SpaceX religion, that's who.  God (or just Elon Musk to the rest of us) said it.  Hand waive any logic.  Hand wave any math.  Who wants an extra 40 tons of food or water?  Then there's that magical ITS/BFR/Starship that we haven't even seen in mockup form as of yet.  There's also a magical LOX/LCH4 plant that hasn't even begun testing, so even if we shipped a 1,000 tons of batteries to Mars using a rocket that still doesn't exist, there's no way to get it back.

Where's Captain Picard when I need him to give us his world-famous facepalm?

Maybe he's too busy running his Hollyweird mockup of the starship they call Enterprise, which is still more real than the SpaceX Starship, to be bothered with the minor details of getting to Mars.  One thing that's sure to irk him is when Scotty tells him that no amount of photovoltaic panels will generate enough power to warp his studio production set to Mars.

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#11 2018-11-26 09:47:26

louis
Member
From: UK
Registered: 2008-03-24
Posts: 7,087

Re: Nuclear power - How much is needed?

They might have built a mock-up.  As far as reactors go, so far all they seem to have done is build a small prototype.

kbd512 wrote:

Louis,

There is no ITS, BFR, or Starship, either.  There is only experimentation to test out some design, whatever / whenever that becomes.  NASA actually built and operated their test fission reactor at rated thermal output at the Y-12 Nevada National Security Complex.  Starship, or whatever SpaceX calls it tomorrow after their next marketing ideation falls flat, still only exists in PowerPoint and nowhere else.  Right now, KiloPower is further along in its development path than everyone's favorite PowerPoint rocket is.  I can post a photo of KiloPower, rather than a PowerPoint graphic, because DOE and NASA already built it.  You can't post a photo of this new Starship because it doesn't exist.

Oh, look, there's KiloPower:

KiloPower - The fission reactor Louis wants to pretend doesn't exist

Welcome to the Kilopower Press Conference

Apparently NASA intends to offer it for sale to commercial users, too:

Lee Mason, NASA Kilopower overview and mission applications

Who would take 50 tons of batteries to Mars when 10 tons of reactors could get the job done?

The people who subscribe to SpaceX religion, that's who.  God (or just Elon Musk to the rest of us) said it.  Hand waive any logic.  Hand wave any math.  Who wants an extra 40 tons of food or water?  Then there's that magical ITS/BFR/Starship that we haven't even seen in mockup form as of yet.  There's also a magical LOX/LCH4 plant that hasn't even begun testing, so even if we shipped a 1,000 tons of batteries to Mars using a rocket that still doesn't exist, there's no way to get it back.

Where's Captain Picard when I need him to give us his world-famous facepalm?

Maybe he's too busy running his Hollyweird mockup of the starship they call Enterprise, which is still more real than the SpaceX Starship, to be bothered with the minor details of getting to Mars.  One thing that's sure to irk him is when Scotty tells him that no amount of photovoltaic panels will generate enough power to warp his studio production set to Mars.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#12 2018-11-26 10:08:23

kbd512
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Registered: 2015-01-02
Posts: 4,923

Re: Nuclear power - How much is needed?

The reactor used in the test was 10% scale.  The core diameter for the 10% scale prototype is 4 inches (101.16mm).  The core diameter for the 100% scale unit is 6 inches (152.4mm).  Either way, the core fits in a coffee can.  I'm sure that's a quantum leap for you, but in objective reality it's not.  All the materials and functional components used in the reactor test are exactly what they intend to use on the flight test article that goes into space.  They've completed all reactor tests.  Now they're building a flight test article.  NASA can launch it on a Falcon 9.  Since Falcon 9 is a SpaceX rocket, and SpaceX can do no wrong, there should be no conflict with the religious faithful who worship at the altar of SpaceX.

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#13 2018-11-26 19:01:53

louis
Member
From: UK
Registered: 2008-03-24
Posts: 7,087

Re: Nuclear power - How much is needed?

10% scale but also not yet space rated, Mars surface rated or human rated.

But perhaps most importantly, Musk has no intention of using nuclear power on Mars. Quite right I think from a number of angles. And Space X are the only outfit that will get there any time soon.

kbd512 wrote:

The reactor used in the test was 10% scale.  The core diameter for the 10% scale prototype is 4 inches (101.16mm).  The core diameter for the 100% scale unit is 6 inches (152.4mm).  Either way, the core fits in a coffee can.  I'm sure that's a quantum leap for you, but in objective reality it's not.  All the materials and functional components used in the reactor test are exactly what they intend to use on the flight test article that goes into space.  They've completed all reactor tests.  Now they're building a flight test article.  NASA can launch it on a Falcon 9.  Since Falcon 9 is a SpaceX rocket, and SpaceX can do no wrong, there should be no conflict with the religious faithful who worship at the altar of SpaceX.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#14 2018-11-26 19:11:41

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 23,908

Re: Nuclear power - How much is needed?

Well the scale model worked in ambient air where mars will cool it while in operation. A unit can fail sure but with enough of these very light mass units sent there is not hardship of energy rationing as would happen in a solar condition. Sending even extras that are not used is still mass efficient.

Solar plus batteries eat up the mass to mars and can fail hard for either part and they only collect in the day and once the batteries are empty there is no more until the next day to recharge everything.

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#15 2018-11-26 22:37:50

kbd512
Administrator
Registered: 2015-01-02
Posts: 4,923

Re: Nuclear power - How much is needed?

louis wrote:

10% scale but also not yet space rated, Mars surface rated or human rated.

Launch vehicles and spacecraft are human-rated, Louis.  A wrench isn't human-rated.

On that note, BFR isn't space-rated or human-rated.  In fact, it's never been built in mockup form.

louis wrote:

But perhaps most importantly, Musk has no intention of using nuclear power on Mars. Quite right I think from a number of angles. And Space X are the only outfit that will get there any time soon.

Did you ask Elon Musk what his intentions were?

If not, then how do you know what he's thinking?

SpaceX has never sent anyone into space.  Count your chickens after you get some eggs.

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#16 2020-09-18 15:19:23

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 23,908

Re: Nuclear power - How much is needed?

bump

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#17 2021-08-13 07:25:26

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 1,336

Re: Nuclear power - How much is needed?

Food for thought.  The 10kWe Kilopower reactors will each contain some 44kg of highly enriched uranium.
https://en.m.wikipedia.org/wiki/Kilopower

If these shut down after ten years having depleted some 10% of fissile atoms, then some 40kg of highly enriched uranium will remain.  This uranium can be extracted by dissolving the entire unit in concentrated nitric or sulphuric acid.

The uranium sulphate or nitrate can then be used to fuel aqueous homogenous reactors.
https://en.m.wikipedia.org/wiki/Aqueous … us_reactor

The Kema reactor produced power up to 1MW-thermal using just 6kg of 235U, mixed with 85% thorium, dissolved in D2O moderator.  On this basis, a single Kilopower unit could provide the starting material for a reactor with power of several MW.  This would breed additional 233U from native Martian thorium, to replace the 235U that is spent and to fuel additional startup reactors.  In this way, a single 10kWe Kilopower unit, could provide the starting material needed for a breeder reactor programme eventually generating thousands of GW of power for a heavily colonised Mars.  The initial aqueous homogenous reactor, could be constructed from high silicon cast iron, with an integral cooling jacket built into the cast iron vessel.

On Earth, 1GWe-year involves the fission of about 1000kg of uranium atoms.  Operating at 10kWe for 10 years, a single Kilopower unit will fission just 0.1kg of uranium, a volume about the size of a cherry.  This suggests that of the ~40kg 235U that the unit contains at beginning of life, only 0.25% will be consumed by fission after 10 years.  Some 99.75% of uranium will be available to support second generation, Mars-built AHRs during the colony building phase.

Last edited by Calliban (2021-08-13 07:43:49)


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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