Light weight nuclear reactor, updating Mars Direct

RobertDyck · 2014-02-23 19:40:48

SpaceNut wrote:

I have been reviewing the power systems for ISS and have begun to wonder why so little power is needed for the HAB on Mars. What am I missing that makes the level on the ISS so High or is the level for mars to low.

Do you have a break-down of power for ISS? For life support, I used figures I could get for ISS equipment. Scaled up for one additional crew member. Remember figures I listed in this discussion thread are for life support only; they don't include temperature control, lighting, science equipment, etc.

SpaceNut · 2014-02-27 21:16:06

I finally found the power distribution for the ISS design from Boeing http://www.boeing.com/assets/pdf/defens … System.pdf

I am still looking for the individual module specifics.

From what I know from solar the first loss is from heating of panels and on the ISS that must be quite a bit in the direct sun. Then there is the charging system interface and being of high voltage design to lower the size of wire mass that still is some. Then there is the buss distribution which looks like that feeds the modules which steps the High voltage DC power to a more local voltage and then finally if the unit in the module needs AC power there is still more loss.

I would say for the 80kw that we would recieve that we must be down to 50kw to 60kw questimate useable power.

RobertDyck · 2014-03-04 02:35:46

Found an discussion thread where I posted mass of ISS dehumidifier, and regenerator for spacesuit CO2 removal systems.

Hamilton Sundstrand Regenerable CO2 Removal System is designed to support the spacesuit (EMU). It is located in the airlock and is already on orbit. It replaces non-regenerable lithium hydroxide (LiOH) carbon dioxide (CO2) removal system located in the EMU’s Primary Life Support System. The Metox system consists of two principal components: (1) a regenerator assembly; and (2) a metal oxide sorbent canister. The process involves carbon dioxide removal and the subsequent regeneration of the sorbent material. The metal oxide canister integrates a set of metal oxide sorbent sheets for CO2 removal with an activated charcoal bed for Trace Contaminant Control. After each EVA, the Metox Canister is removed from the EMU LSS “back pack” and placed in the regenerator assembly. The Metox regenerator assembly is designed for use in the ISS Airlock to regenerate up to two Metox Canisters at a time. The metal oxide sorbent is regenerated by flowing air at approximately 400º F at 7.5 scfm through each expended canister for a duration of 10 hours. This is followed by a 4 hour cool down period to return the canisters and oven to a “safe touch” temperature. Specifications:
Canister is designed to maintain the inspired partial pressure CO2 at less than 7.6 mm Hg up to and including a metabolic rate of 1,600 BTU/hour (469 Watts) for a total loading of 1.48 lbs. (0.67kg) of CO2, minimum
Metox system will maintain this CO2 removal performance for at least 55 adsorb/desorb cycles
Power: 1000 watts peak (Metox Regenerator)
Pressure: Canister can withstand pressures of 0 - 16 psia during EMU CO2 removal, 14.5 - 15.2 psia during airlock regeneration
Size: 17.72 in. high x 19.0 in. wide 30 in. deep (Metox Regenerator), 10” x 14” x 3.5” (Metox Canister)
Weight: 105 lbs. (Metox Regenerator), 32 lbs. (Metox Canister in regenerated state)
Dehumidifier
The Common Cabin Air Assembly (CCAA) in the U.S. On-Orbit Segment modules of ISS provides the capability to control the cabin air temperature, maintain the cabin air humidity level within limits, and generate ventilation air flow. The CCAA includes orbital replaceable unit (ORU) subassemblies for the fan, condensing heat exchanger, water/gas separator, liquid & temperature sensor, temperature control valve, and an electronics box. The Common Cabin Air Assembly is used in four U.S. modules: Hab, Lab, Node 2, and Airlock.
Air flow rate is 300 - 500 cfm, coolant water flow rate is 600 - 1,290 lbs./hr
Power: Peak sensible heat removal is 2,032 watts, Peak latent heat removal is 1,000 watts
Moisture removal is 0.76-3.20 lbs./hr
Size: 17.5" x 53.5" x 20.34"
Weight: 212.6 lbs. max

Ravaun · 2014-04-26 00:32:50

Estimated mass of Curiosity Mobility System, including computers, not including power: 210 kg. Estimate based upon Lunokhod chassis mass x2, which should be roughly equiv. (+/- 40 kg) to modern systems, including computer controls and differential.

At 210 chassis+computer estimate plus 1pi shield and remote core robot, estimated mass: 2,681 kg.

Assumes 2x chassis, 1.5x computers, 1000 lb screen matrix--to be filled with chess-mix of sintered regolith by addition of bottled, salt water (est. 1275 kg), sintered from top of shield wall to base, creating a slurry-like concrete. Successive applications will build a complete wall, capable of blocking alpha, beta, gamma/x-ray and neutron radiation. Remote core insertion/shield assembly/sinterator robot: 585 kg. Robot similar to bomb-disposal Cobham tEODor, mass of 375 kg, est. 585 kg adapted for Mars use, including sinterator gear. Screen matrix composed of polyethylene glycol in a plastic which expands upon exposure to microwave heating.

EOD robot can be used to manufacture building foundations, prior to arrival of crew, following activation of reactor and creation of shield wall. RAD-hardened chips would be required for logic. During shield wall construction, jeep (Extended Curiosity Mobility System) would be parked well away from construction zone, likely 1000 meters. Robot to use wireless link to CMS chassis computers to enhance visual acuity.

You could also go with the NASA design, which would run to about 3,850 kg, using their specialized 6 wheel mobility chassis. It should approved for use sometime near 2030 for use on Mars. I think the EOD robot could be adapted, with a 120 - 150 kg sinterator unit in much less time. They have versions which can switch out from a manipulator tool to a simple steam-shovel type set-up. (If not, it wouldn't be too difficult to build...simple mechanical levers using low-wattage motors...assumed as part of the mass estimate.)

Sources: http://cdn.intechopen.com/pdfs-wm/6841.pdf
http://www.nrc.gov/about-nrc/radiation/ … asics.html
http://www.cobham.com/about-cobham/miss … tract.aspx

Robot Mobility Systems for Planetary Surface Exploration – State-of-the-Art and Future
Outlook: A Literature Survey. Aravind Seeni, i, Bernd Schäfer and Gerd Hirzinger.

Institute of Robotics and Mechatronics
German Aerospace Center (DLR)
Germany

RobertDyck · 2014-06-23 11:03:18

In this discussion thread, I proposed a module docked to the nose of a Dragon spacecraft, packed with recycling life support equipment. The module would be a cylinder, with just enough room inside for a single crewmember. I calculated size of this module.

Life support equipment for ISS is installed in an ISS payload rack. Those racks are: 2 m (79.3 in) high, 1.05 m (41.3 in) wide, and 85.9 cm (33.8 in) deep. There is a little air space between pieces of equipment in life support racks, but not a lot. So assuming a cylinder the same hight as an ISS payload rack, just barely enough room in the centre for a single crew member, then equipment depth to the cylinder walls the same as the depth of an ISS payload rack. That adds up to 8 feet diameter: 3.8" equipment either side, which gives 28.4" diameter centre space for the crew member. Cygnus is 10.1 feet outside diameter by 2.67 metres long, pressurized volume. This module would be 8 feet inside diameter by 2.0 metres (78.74" or 6.56 feet) long.

Last edited by RobertDyck (2014-06-23 11:03:45)

RobertDyck · 2014-06-23 11:07:22

Dragon V2

JoshNH4H · 2014-06-23 12:35:43

I wouldn't regard the life support aboard the ISS as anything like a final version

RobertDyck · 2014-06-23 14:10:14

NASA thought it "way too advanced" when I suggested in-vitro chloroplasts. So I'm trying to use existing technology.

I do have some ideas, things to add to the ISS system. The current toilet is basically a garburator: an air current draws any drops or lose stuff in, then air is squeezed out. The result is packaged in plastic bags for disposal. I would have the toilet bake feces with an electric oven to extract moisture. The Russians came up with a vacuum desiccator. Whichever works best. The other thing is Direct CO2 electrolysis, to extract some O2 from the CO2 that the Sabatier cannot use. And it would be nice to have a zero-G washing machine; something to launder clothes and washcloths. ISS doesn't have a shower, so they use washcloths. And a capsule certainly won't have a shower. The water processing unit is supposed to handle wash water, the only catch is collecting the water. A clothes washer for an RV is similar to an apartment washer/dryer, but one appliance with one drum acts as both washer and dryer. For a capsule, I would like an extra small one.

Here's a camping washer, perhaps something this small but for space…
http://www.portablewasherdryercombo.com … ne-review/

But all that is new, and none has been approved by NASA. So for this exercise I assume the same stuff as ISS.

Last edited by RobertDyck (2014-06-23 22:28:56)

JoshNH4H · 2014-06-23 21:04:36

The issue with ISS technology is that, while it has been tested and space-certified, it has also been shown to simply not work well enough for any long-duration mission.

RobertDyck · 2014-06-23 22:08:13

Actually, that's a reason not to abandon the ISS design. They found a problem by in-space experience. There are proposals to fix the problems with calcium scale. Once they get that problem fixed, they should demonstrated it on ISS, then use the working design for Mars.

JoshNH4H · 2014-06-23 22:31:06

I'm not arguing, but stating a fact: The life support equipment aboard the ISS isn't reliable enough to be used on a mission to another planet, especially not one that will take many months

RobertDyck · 2014-06-23 22:40:21

Any untried equipment is even less reliable. Because it's untried. Since before ISS was built I've been saying we need to use it as a testbed for long duration life support.

JoshNH4H · 2014-06-23 23:39:21

I can certainly see the politician in you. You're always big on saying how long you've held an opinion, as if that has any bearing on its validity. No offense intended, of course, just pointing it out!

With regards to the particular opinion being expressed, the issue with not-yet-existing hardware is not its reliability or unreliability but the fact that we don't know whether it will be reliable or not because it doesn't exist yet. Meta-unreliability, if you will. ISS hardware is unreliable but meta-reliable, since we know that it's not good enough for long term missions. This means that we necessarily need to develop new hardware, or make significant improvements to hardware that already exists, which is effectively the same thing. Obviously in-space testing, be it aboard ISS or elsewhere, is a good idea, and one could make a strong argument that it's necessary.

But regardless, the life support hardware on ISS is not going to Mars.

RobertDyck · 2014-06-24 00:44:53

Ok. Today's city newspaper says the NDP party has just nominated a new candidate for my riding (electoral district). I thought they might. He lost the last election. This has been an NDP stronghold since the riding was created in 1979. I was a teenager in high school back then. For our American members, the NDP is socialist. They are "liberal" in the sense that the American Republican party likes to use that word. The candidate for my party who got the nomination instead of me, got the lowest proportion of the vote for any candidate for my party in this area. I checked election results all the way back to Confederation (when Canada became a country). Checking every riding (electoral district) that encompassed even a portion of what is now my riding. The candidate who replaced me for the 2008 election set an all time low for my riding, but the candidate for 2011 set an even lower record. That's my argument why they should nominate me. But I'm not all that good at organizing support, so they may pick someone else. Party brass likes rich individuals, who can bring a lot of money to their campaign. And certain individuals want to pull our party to the left, so they don't like me. I may be stuck as an unemployed computer software developer.

So you don't want to hear how long I've said this or that. My current concern is Congress wants to decommission ISS. They should have installed US life support long ago. And when they identified a problem, it should have been fixed promptly. I'm worried that Congress will order ISS de-orbited before they demonstrate a life support system that is reliable enough for Mars. They need to stop sitting on their ass, and get the job done!

And anyone who thinks ISS can be replaced by a less expensive station is dreaming. Corporate executives for military contractors do not see any value in space. They treat all space projects as simply an excuse to funnel money into their pocket. Any new station would be the same. I'm sure there are executives arguing to replace ISS because they want Congress to pay another $100 billion. Don't believe me? How much money has NASA saved since Shuttle was decommissioned? None. Decommissioning ISS would simply pour all the money spent down the drain, requiring even more for the next station. And no work on life support will be possible until that new station is operational. That fastest and least expensive solution for Mars is to use the station we have now.

A couple additional facts: I spoke to an engineer for Boeing who worked on ISS. I know several who worked on Shuttle; they all complained their ideas to reduce costs were overruled by corporate executives. But this one worked on ISS; he told me that Boeing didn't get the contract for the Advanced Tactical Fighter, so they had to recover their costs for the YF-23 somehow. They deliberately overcharged for work on ISS. That's how black projects are paid for. YF-23 was not a black project, but that's what they did. I believe that's why prototypes for the Joint Strike Fighter were funded as X projects: X-35 and X-32. The X-35 won, becoming the F-35. It was an X project so the loser wouldn't have to recover costs like YF-23. NASA paid anyway, may as well do it in the open.

The other fact is military contractors contribute funds to Congressional election campaigns. How many NASA projects were approved in exchange for campaign fund contributions? We hear about Congressmen approving projects that create jobs in their electoral district, but how about campaign contributions? Congress has to balance the budget, which means reducing total spending. But congressmen have to raise funds for their election. Those contributions aren't supposed to be kick-backs, but how well is it tracked? If Congressmen (and women) treat NASA as a means to gain election contributions, then they won't try to reduce cost. I notice no NASA centers were closed after Shuttle was decommissioned. They created projects to justify keeping those centers open, and those people employed. I would like to argue to Congress that those centers would be necessary for a Mars mission. That a mission like Mars Direct would cost about what NASA gets now. Just redirect Constellation project funding to Mars. After Columbia, funds were cut from ISS to pay for returning Shuttle to flight. That meant engineers lost their jobs, but they didn't stay unemployed. Those same people were employed to return Shuttle to flight. So redirecting funds from one NASA project to another, just moved personnel. Obama cancelled Constellation, but Congress revived it, living on as a zombie, sucking funds and occupying personnel even though the objective of the Moon has been prohibited by presidential order. Redirect those funds and personnel to Mars.

The first step is to use ISS. Finish developing a reliable long-term life support system. And demonstrate that system in space for at least the duration of a Mars mission. I would prefer the centrifuge module as well, to test long term exposure to Mars level gravity. But we don't have it. So use what we have.

Those arguing to replace ISS with yet another station are just arguing to not go to Mars within our lifetime.

But I should directly address your point. Hardware on ISS that got clogged by calcium deposits are components common with any serious alternative. So there is no radical alternative. What will go to Mars will be an incremental improvement on what we have on ISS now.

Last edited by RobertDyck (2014-06-24 11:29:36)

Tom Kalbfus · 2014-06-24 05:14:19

A Presidential order can be countermanded by another Presidential Order, and Obama has just 2 years left in office, if he doesn't get impeached. I think keeping the rocket around just in case the next President decides to send humans to the Moon is a good idea! It is an easy first step on the way to Mars. Forbiding travel to th Moon doesn't make going to Mars any easier, and the hardware requirements for going to the Moon is less than for a Mars trip, it can easily be accomplished within one Presidential Term, while going to Mars requires the cooperation of successive Administrations as the hardware is built in space. Going to the Moon is also less risky. What happens if someone dies on the way to Mars? There is more time for someone to die on the way to Mars, as that Mission lasts 3 years, going to the Moon can last from 1 to 2 weeks, there is less time for someone to die, therefore such a death is less likely on a Moon mission than a Mars Mission.

JoshNH4H · 2014-06-24 07:59:32

RobertDyck-

I think the biggest issue with NASA is that they don't really expect to be getting anywhere any time soon either. I think we all accept that a fully functional space station could be done for much less than the ISS was. As much or more than the contractors, the blame falls on NASA for being a bad customer and not finding another way when it was getting screwed.

At this point, though, the ISS represents a hundred billion dollar sunk investment whose upkeep costs are a billion or so per year. It's probablymcheaper tomleep it up there and keep doing experiments with it. Though I would not be opposed to a COTS-like solution, where the government simply says that it will pay let's say one billion dollars for a fully functional space station placed in orbit. For comparison purposes, the ISS's internal pressurized volume of 837 cubic meters corresponds to a house with 335 square meters (3600 square feet), which is large but certainly not unheard of. Alternatively, it corresponds to a cube about 9.5 m on a side. No piece of cake, but all told it's really not that much hardware.

RobertDyck · 2014-06-24 13:11:55

The point of this discussion thread was to show that most of the technology and hardware for the Mars Direct ERV is now Off-The-Shelf. I won't call a military nuclear reactor "Commercial", but it is ready. Experience with life support on ISS tells us it isn't sufficiently reliable to put in the service module where it can't be repaired in flight. Astronauts need access so they can perform repairs. Ok, we discussed that earlier in this discusison thread. That's why I suggested a module docked to Dragon's nose rather than converting the turnk into a service module and putting life support there. Does life support need more work? Yes, a little, but not a lot. And I want to downplay that to Congress, to emphasize how little work is left to do.

JoshNH4H · 2014-06-24 13:19:57

To Congress, sure. But I'd be quite shocked if any Congressman or Congresswoman ever frequented this forum. The ability to service the life support is important, of course, and for what it's worth the idea of adding a life support module is a good one*. But from a technical perspective we can't reproduce the ISS's life support systems because they're just not reliable enough. From a development perspective I agree that it's a relatively trivial budget/time item, but it's a vital one nonetheless.

*Is it possible that the life support could be damaged or degraded by radiation? If so placement becomes important.

Tom Kalbfus · 2014-06-24 13:43:49

If you apply enough energy to the problem, you can separate the oxygen from carbon-dioxide.

JoshNH4H · 2014-06-24 14:00:23

We can do a lot of things. Using a sabatier reactor we could work it all the way down to Carbon and Oxygen. The question is reliability.

RobertDyck · 2014-06-24 14:16:50

For radiation to degrade metal requires intense radiation over years. Nuclear reactors have to worry about that in coolant pipes in their core, but life support equipment of a spacecraft will not receive sufficient intensity or duration for any significant impact to metal. So metal pipes and plastic membranes of a reverse osmosis filter will not have to worry about radiation. A greenhouse would have to worry about radiation, but plants can endure more radiation than humans, and the ISS system is not a greenhouse. It's membranes in animals that are so sensative to radiation.
::Edit:: Animals of the phylum Chordate have membranes sensitive to radiation. That includes mammals, lizards, and fish. Insects aren't chordate, and are more resistant to radiation. Fish normally don't worry about radiation, because the water they swim in protects them.

The radiation issue is another argument against Mars Direct. The Mars Direct habitat has a radiation shelter in case of coronal mass ejection, but the ERV doesn't. But this discussion thread is about updating Mars Direct, not redesigning it.

Last edited by RobertDyck (2014-06-24 14:49:33)

JoshNH4H · 2014-06-24 15:06:18

Well, I thought it was a concern worth raising. Presumably sensitivity is high for any system with large numbers of very small scale components. Semiconductors might be sensitive-- in fact we know they are, now that I think about it-- but otherwise I'm willing to accept that radiation is not a big risk.

Tom Kalbfus · 2014-06-26 05:43:55

There are semiconductors in the unmanned probes we send to Mars. Perhaps we ought to start with monkeys in a space capsule and see what happens.

GW Johnson · 2014-06-27 10:02:13

Radiation from nuclear weapons is not the same as GCR or solar flare outbursts, but it is sort-of similar. My experiences working in the defense business told me that electronics and biology are susceptible to nuclear radiation, while basic electrical hardware and basic materials, not so very much. Oddly enough, the old-time vacuum-tube electronics were generally (not always) nuclear-hard, while the solid-state stuff was extremely susceptible. Terrestrial insects were more nuclear-hard than terrestrial reptiles and mammals, for reasons outlined in another post above somewhere.

Solid-state electronics can be made nuclear-hard by appropriate shielding. The same thing works for biology, you just need an even-better shield. It'll take either a Star Trek EM screen or else many meters of material to shield against GCR "effectively" (to levels like here at home) for men, women, and children in space. It takes more meters of material because of the secondary-shower effect, which you have to contain as well. But 20 cm of water works for solar flare outbursts, and (I suspect) the stuff circulating in the Van Allen belts (and their analogs at the other planets).

In the inner solar system, GCR cycles with the sun's activity between 24 Rem and 60 Rem (annual dosage), according to NASA's best data. It might be worse further out. NASA's annual limit for astronauts is 50 Rem, which is not very much different from that max value. This is complicated by a career limit (accumulated exposure over multiple years) that varies with age and gender. Astronauts currently are expected to accept a higher risk than us surface civilians (nearer or under 1 Rem). Under these rules with nominal 2.5-year missions, a crew can go to Mars once, but not twice, unshielded in any way from GCR. Two missions hits the career limits.

The 20 cm of water as a shield is too thin for there to be a secondary shower effect, but it does act to reduce GCR exposure slightly. I'm not sure, but I think it might actually reduce 60 Rem outside to right at 50 Rem inside the 20 cm water shield. In other words, we know enough RIGHT NOW to get a crew to Mars and back without overexposing them to GCR or solar flare outbursts. It's just that no one wants to bite the bullet and design-in that 20 cm water shield about a designated radiation shelter space. Why? Because that'll be too heavy to fly as a single launch of an SLS-type vehicle, and it'll be too heavy for a direct shot to Mars.

The problem isn't the shield, or its weight, it's the mission design.

You'll have to have that mass of water on board anyway in terms of life support and waste treatment for a long voyage. So, use it! For the radiation shield. The design decision regarding health protection is obvious to the casual observer! The smarter designer would wrap that water shield around the command flight deck, so that critical maneuvers could be made no matter the solar "weather" outside.

Designs like that will have to be assembled in LEO from multiple components docked together. You don't need an SLS to do that, but it might help if its launch cost were under $2500/pound delivered, where we are now with Atlas-5, Delta-4, Falcon-9, and several European and Russian rockets. These all exist in forms capable of delivering 10+tons to LEO, some up to 20 tons. I think there is a version of Atlas-5 capable of 25 tons, but I'm not sure it has ever flown. We built ISS with stuff up to 15 tons, we just did it with an idiotically-expensive launcher at $30,000+/pound. LEO assembly SIMPLY NEED NOT BE AS EXPENSIVE AS BUILDING THE ISS WAS!

This kind of design approach sort-of rules out Mars-direct type mission designs. Unfortunately. But, it was the original Apollo design, before they went with lunar orbit rendezvous, which got them down to one Saturn-5 launch per mission ("moon direct"?). We knew that long ago it (assembly in LEO) could be made to work, and we have since acquired most or all of the skills needed to make it work for Mars.

Doing both LEO-rendezvous/assembly and Mars orbit rendezvous (a lander like Apollo) pushes you right back to the 1950's concept of an orbit-to-orbit transport assembled in LEO, with landers to use at destination. That's the mission design with minimum launched mass that also meets what we now know we must have for life support and health protection. Sorry, that's just life. Not fair. Nobody ever said it was.

So, as it turns out, that orbit-to-orbit transport idea from over half a century ago always was the best idea. Plus, today, we already have the skills and technologies to make it work. We've known everything we need to know since about 1995-ish. The health protection requirements weren't really known until about then.

The kind of direct (minimalist) missions to Mars that have worked so well sending probes is just not the best choice for sending men. It is past time to face up to that unpleasant fact. The life support and health protection requirements simply point in a different direction. Microgravity diseases (plural) and radiation shielding requirements do dictate that different path, until and unless there are major technological breakthroughs in both propulsion and magnetic screens. Like "warp drive".

Don't hold your breath for those breakthroughs, I certainly won't. If you want to live long enough to see men on Mars, then we need to push for doing it with what we have right now. Very few technology-development programs ever actually fly anything in the way of useful vehicles. The ones that produce useful flying vehicles use off-the-shelf stuff. Another little unpleasant fact of life.

GW

RobertDyck · 2014-06-27 14:35:56

Well, as I said before, I proposed that in Yet another Mars architecture. That design calls for a reusable spacecraft to travel from Earth orbit to Mars orbit and back. Not a cycler, a reusable spacecraft. No need for warp drive, or Harry Potter magic wand. And does involve on-orbit assembly.

Last edited by RobertDyck (2014-06-27 16:03:43)

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#76 2014-02-23 19:40:48

Re: Light weight nuclear reactor, updating Mars Direct

#77 2014-02-27 21:16:06

Re: Light weight nuclear reactor, updating Mars Direct

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#79 2014-04-26 00:32:50

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