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#26 2019-08-13 20:08:53

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 23,096

Re: Technology needed for Mars

Seems that we have yet another use for Carbon Nanotubes as these Damaged hearts rewired with nanotube fibers

Researchers at Texas Heart Institute and Rice University have confirmed that flexible, conductive fibers made of carbon nanotubes can bridge damaged tissue to deliver electrical signals and keep hearts beating despite congestive heart failure or dilated cardiomyopathy. Thin, flexible fibers made of carbon nanotubes have now proven able to bridge damaged heart tissues and deliver the electrical signals needed to keep those hearts beating.

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#27 2019-10-08 08:54:41

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 7,326

Re: Technology needed for Mars

For SpaceNut re topic ...

I let a newsletter offer tempt me into subscribing recently.

This item may be of interest to a forum reader down the line:

http://www.ti.com/lit/an/sboa344/sboa344.pdf

You have to sign up to see the full article but subscription is free.

Kirby Kruckmeyer
ABSTRACT
Historically, satellite programs have used space grade, hermetically sealed, QML-V qualified components
for enhanced reliability and radiation hardness. With the emergence of “NewSpace,” there has been more
interest in using plastic encapsulated microcircuits (PEM) in space for a variety of reasons. NewSpace is a
loosely defined term covering some of the trends in the space ecosystem, including the emerging private
spaceflight industry and programs that have reduced reliability, lifetime, and radiation requirements. PEMs
become more attractive because leading edge products are not available as space qualified products and
PEMs generally have smaller footprints and are lighter than the ceramic packages used in space qualified
products. It has been recognized that there is a quality and reliability risk in using commercial-off the shelf
(COTS) products and some space programs have been investigating using automotive grade AEC-Q100
products with more stringent qualification requirements. However, the extra qualification steps in Q100
parts do not meet all the requirements of a space application, even for those space applications with
reduced requirements. For instance, commercial low earth orbit (LEO) applications with a projected three
year life still have to meet radiation goals that many PEM products do not survive. One of the biggest
challenges for a satellite program is finding and then testing those products that meet the radiation goals.
Although radiation performance may be biggest obstacle to using some COTS or automotive products in
space, there are a number of other risks and factors to consider, such as tin whiskers, copper bond wires,
rated temperature range, and package outgassing. How is a customer to know if a product has the right
stuff to even be considered for a space mission?

I have omitted the name of the corporate underwriter to fit with forum tradition.

(th)

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#28 2019-10-08 16:53:29

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 23,096

Re: Technology needed for Mars

Some of the once damaging effects of radiation have gotten less as the parts get smaller and with much more testing after coating the parts with conformal coatings they are pretty much sealed from anything that would cause corrosion or moisture to get into the circuits.

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#29 2020-01-06 19:17:08

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 7,326

Re: Technology needed for Mars

For SpaceNut ...

The link below is from Lizard King of luf.org

It applies to more than one topic, so I'll be posting it where it seems to fit.

https://www.sciencemag.org/news/2019/09 … iquid-fuel

In this case, a Mars expedition would use this technology to capture water vapor and CO2 from the atmosphere.

(th)

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#30 2020-07-18 15:17:37

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 7,326

Re: Technology needed for Mars

For SpaceNut re Topic ...

I was looking for an existing topic where the suggestion which follows would fit...

It would fit just as well in a topic "Technology needed for Earth" ...

There is a business opportunity with multiple avenues for earning income while providing needed services.

When Magellan set sail for his Around the World venture, he included a barber in his crew.  That was 500 years ago, and the niceties of proper appearance were known to the aristocrats of the time, but in Magellan's case, I'm of the opinion he included a barber for ALL the members of the crew, and not just for the captains and other officers.

In the case of an expedition to Mars, I do ** not ** expect there will be a manifest slot for a barber.

Instead, a technology to allow individual crew members to trim their own hair would seem (to me at least) a reasonable capability to include. 

This is the first time I've thought about what members of the ISS do about keeping trim.

It would not be surprising if a bit of hair trimming is a part of the responsibility of crew members.

In any case, what this post is about is the business opportunity for Mars, ** and ** for Earth, for people to be able to cut their own hair.

There is a product or system called "Magic Mirror" that is (apparently) available for download from the Internet.

A local computer group gave a presentation on the system, and it is available for viewing on YouTube.  I'll post the link if anyone is interested. 

However, "Magic Mirror" turns out NOT to be what I was hoping for.

What I am imagining is a robot with a capability of maneuvering an electric clippers in one "hand" and a comb in the other, while the operator views a (presumably large) computer screen in order to guide the motions of the robot arms.

The potential market opportunity for Earth seems significant.

But ** here ** is the angle that I'm hoping you (in particular) SpaceNut will appreciate ...

I am interested in designing this system so that ** real ** barbers can operate the equipment remotely.

Thus, the potential exists to provide gainful employment for the thousands of Earth humans who have mastered the art of barbering, while at the same time eliminating travel time from the schedules of countless customers.

SpaceNut ... in the past, when I have offered suggestions for teleoperation, you have (on occasion) translated the suggestion into something involving AI level robotics!  This is ** not ** intended to be any such thing.

I am looking for opportunities to provide gainful employment for thousands of people alive today, and an ** not ** interested in eliminating jobs, as an AI level robot would do.

(th)

Last edited by tahanson43206 (2020-07-23 08:32:02)

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#31 2020-07-18 16:33:08

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 23,096

Re: Technology needed for Mars

Sort of an extension of the hand controls that allow the operator to sit in a booth and to work the controls so that the tools move to the places that we are telling them to move to. Sort of like a tactile suit to save movements to a computer program for later use.

The barber angle would mean comradery of crew such that they care for each others appearance.
There are lots of other activity which include medical that we would want to learn how to do for others...
A Floby was the vacuum cleaner like attachment that was used to groom hair but you are correct that having another person around that would want to do the hair could not be something that all would want to do for each other so a tactile computer interface to control robotic arms that would make use of the tools would seem quite challenging for the person that fears being cut by the tools.

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#32 2020-07-18 17:00:41

kbd512
Administrator
Registered: 2015-01-02
Posts: 4,615

Re: Technology needed for Mars

tahanson43206,

Out of necessity, Mars will have at least 10 "remote maintainers" to support each colonist braving the new frontier, at least initially.  This is no different than how our military functions.  For each person in our military, there are at least a dozen people directly employed, full-time, to supply all of the food / fuel / depot level maintenance of the machines, etc.  We can easily create standing armies of gainfully employed support personnel to supply our space exploitation / colonization endeavors.  This is how the endeavor will ultimately "pay for itself" (creating gainful employment to produce the goods and services that the colonists need to survive), not absurdly expensive trinkets or gaudy advertisements on rockets (things that are merely "here and there" bonuses if/when someone out there is willing to pay for them).

I can justify increased head count to provide engineering and maintenance support services in the form of someone who remotely provides expert guidance to a colonist to maintain a life support system or rocket engine, for example, but I can't justify putting someone on Mars to make watches or collect rocks for rich people.  Some of that stuff will inevitably happen and I'm not against it at all, but only after the basic necessities of life have been taken care of.  Our starting point on Mars must take us from nothing at all to a self-sustaining society, which means all the fundamentals that technologically advanced human civilization here on Earth requires are still required on Mars.  If we could put a million people on Mars, then I can see employing around 15 million people to keep everyone supplied / supported.  We would also have to create the education / health care / transportation support to support the maintainers.  If the US, EU, and Asia all did this, then I can see how we could guarantee the employment of at least a quarter of a billion in high-technology jobs with middle class salaries and benefits.

We're going to build a supply chain of maintainable, rather than replaceable parts, from Earth-to-Mars, using the military's system for maintenance / support of technologically advanced equipment.  The military keeps sophisticated equipment operating for decades through continual disassembly, inspection, re-machining or cleaning, and re-assembly of parts.  Some spares are required, but more often than not, complicated machines have their parts maintained rather than completely replaced.  Overhaul maintenance is a different proposition, as SpaceNut is aware, and a significant number of parts must be replaced at that time.  We'll have to figure out how to do that remotely.  In any case, the military's maintenance and supply system has proven itself capable of sustaining a forward deployed force for many decades now.  Mars is clearly an extreme case where the force in question has been forward deployed to another planet.

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#33 2020-07-19 09:57:53

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 1,154

Re: Technology needed for Mars

A high breeding ratio, fast breeder reactor.  Mars appears to have a poor abundance of fissile fuels.  However, a fast breeder reactor yields so much energy from such a small amount of fuel, that it hardly matters.  I would propose a gas-cooled fast reactor, with an S-CO2 direct cycle.  The reasons are:

1. A harder neutron spectrum than a sodium cooled FBR, resulting in a shorter doubling time.  For a sodium FBR, doubling time is typically 30 years.  For a fast growing Martian colony, we would want to get that down to a decade of possible.
2. Direct cycle means no bulky heat exchanges.
3. The S-CO2 power generation equipment is very compact. When combined with a high power density core and a direct cycle, this allows very high system power density.
4. CO2 is non-corrosive, so all parts of the system (minus perhaps the fuel) can be made from low carbon steel, with a pre-stressed concrete pressure vessel.
5. A relatively low temperature cycle might be compatible with metallic fuel, that is suitable for electro-refining.
6. A high temperature cycle could drive thermochemical hydrogen production through the sulfur cycle.  This would be the basis of synthetic fuel production, plastics and a Martian steel industry.

This probably wouldn't be the first reactor built on Mars.  We would probably start with light water reactors burning enriched uranium.  But as base power requirements grow and the spent fuel accumulates, we would eventually have enough plutonium to start an FBR programme.

Last edited by Calliban (2020-07-19 10:03:48)


Interested in space science, engineering and technology.

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#34 2021-06-10 15:36:31

kbd512
Administrator
Registered: 2015-01-02
Posts: 4,615

Re: Technology needed for Mars

Calliban,

If the CO2 is extremely pure, with no O2 and H2O vapor from the Martian atmosphere, then it should be compatible with low carbon steel.  However, even trace amounts of O2 or H2O will quickly corrode unprotected low carbon steel.  If the steel was coated with Nickel, possibly sourced from Nickel-Iron asteroids found on the surface of Mars, then I could see a CO2-cooled reactor being more practical.  Otherwise, Inconel is quite good at resisting high temperature driven oxidation from hot gas with impurities mixed in.  Incidentally, they tried this (using cheap low carbon steel) in Colorado in the gas-cooled reactor at Fort Saint Vrain, but ran into the same problems with impurities in the coolant gas corroding the steel used in that reactor.  They did eventually resolve the coolant's O2 and H2O contamination problems through strict process control for purifying the coolant gas (I think they used Helium, not CO2), but the reactor was subsequently shut down due to cost overruns shortly thereafter.  The nuclear core was removed and then they started burning natural gas in the same system to generate commercial electric power.

The new diffusion-bonded Printed Circuit Heat Exchangers (PCHEs) are not nearly as bulky and can be designed for very low pressure drops.  They're at least 5 and possibly 6 to 8 times smaller than traditional heat exchangers.  These are typically made from stainless or Inconel, so they'd probably have to be imported from Earth.  Anyway, it's better to keep the power generation loop separate to avoid radioactive contamination of the power turbine for ease of maintenance, since sCO2 gas turbines contain service life-limited consumable parts that must be periodically replaced, especially if the bearings use oil as a lubricant.  The benefit I see to the PCHE and sCO2 gas turbine tech is that it applies to both Earth and Mars, it applies to nuclear thermal, solar thermal, geothermal, and oxy-fuel combustion heat engines.  A Mars colony of any significant size will need one of those technologies to supply power at night, since batteries are impractical at the scale required and technologically demanding to maintain.  The low-cost thermal batteries suitable for grid scale application are all using hot liquid salts anyway, and Professor Donald Sadoway said that power can still be transferred via gas turbines if the thermal photovoltaics prove impractical.

If extreme power density is desired, why not opt for a liquid salt or liquid metal coolant with a sCO2 thermal power transfer scheme on the non-nuclear side of the plant?

I have a counter-proposal for consideration that's very similar to what you proposed:

The reactor containment building will use a Sulfur-based concrete mixed with an Iron Oxide aggregate, both collected right off the surface of Mars.  The reactor vessel itself will be cast ductile iron with a Nitride coating to inhibit oxidation.  The coolant and fuel will be molten salt, so that the reactor vessel itself is not pressurized and the salt-based fuel can have fission products chemically separated without shutting down the reactor.  The secondary loop will be a PCHE that's literally cast into the walls of the iron reactor vessel, to transfer thermal power to a sCO2 gas turbine.  It's an "almost direct cycle", or an "integrated heat pipe" design.  The radioactive fuel salt doesn't touch the power transfer fluid (sCO2), so there will be fewer complications than there otherwise would be with having hot CO2 in direct contact with the fuel.

My reasoning is that minimal processing of all the materials used in construction is required to produce the proposed reactor, most of these materials can be locally sourced from Mars, rather than imported from Earth, so only the nuclear fuel and complex precision machined parts like sCO2 gas turbines and electric generators would need to come from Earth.  Since the turbine and electric generator are relatively small and lightweight, it's feasible to import these machines with little effect on the overall colonization effort.  While the ability to produce cast iron is tantamount to steel production, in pretty much every case here on Earth, producing cast iron is easier, less labor-intensive, and therefore cheaper than producing steel.

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#35 2021-06-10 16:18:37

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 1,154

Re: Technology needed for Mars

I agree that an indirect cycle, using liquid metal coolant, is a better idea than a direct S-CO2 cycle with the development of compact heat exchangers.  Typical S-CO2 cycle inlet pressure is 20-30MPa.  At this pressure, volumetric heat capacity is reasonable even in a gas and the low viscosity of CO2 means good heat transfer coefficients and relatively low temperature drop needed across heat exchangers.

The contamination issues that you mentioned are only partially avoidable when CO2 is used as a reactor coolant.  The problem is that under high neutron and gamma flux, the CO2 breaks down to produce CO and oxygen radicals.  The oxygen then attacks metallic surfaces.  At the relatively low temperatures in Magnox reactors, it wasn't a big problem.  But in AGRs, corrosion became a concern and the graphite moderator suffers progressive loss of density after a couple of decades.  To attempt to mitigate the problem, British AGRs inject methane into the coolant to mop up oxygen radicals.  But that isn't a satisfactory option in a fast reactor.

Sodium is generally accepted to be the best overall fast reactor coolant.  It has excellent thermal properties, low viscosity, it is light enough to avoid eroding fuel surfaces when pumped and although it is a relatively light element, it does not soften neutron spectrum to an unacceptable level.  It does not require pressurisation, even at high temperatures up to 800°C.  Sodium cooled reactors, with metallic tube-in-duct fuel assemblies may achieve very high breeding ratio, which is what we want on Mars.  They are also very compact, with high power density.  With S-CO2 as secondary power generation fluid, the usual need for intermediate heat exchangers should be avoided.  The result would be a nuclear system that has high power density and high efficiency.  Two important drivers for low generating cost.


Interested in space science, engineering and technology.

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