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#1 Re: Human missions » Artificial Gravity using 3 Starships » 2019-12-16 13:17:37

GW Johnson wrote:

Y'all do realize that a variation on Spacex's refuelling concept for "Starship" is a way to get artificial gravity on "Starship"?

Conceivably, yes, and it's a concept explored wrt motivations, variations and applications at NasaSpaceFlight forum.

Some old posts: 

SingleWindowMarsWith38g.png

#2 Re: Terraformation » "Developing Mars": a room.eu.com Special Report, Spring 2018 » 2018-10-05 11:50:52

Void wrote:

1) Even if you can create Ozone in the "Hole", I wonder how it remains there against the wind.  I also wonder how it remains stable, in the presence of the rock of the crater walls, and in the presence of CO and CO2 it may very well react with chemically.  Without Ozone, you would not have any reasonable hope of an external biosphere of significant value to the purpose of terraforming.
2) The heat will keep ice melted or evaporated.  That is a problem.  Moisture tends to move from a source of heat and condense at cold spots.  How do you keep the moisture from migrating to the polar ice caps?  Won't you end up with a dry crater bottom?  Yes, if you continue to melt ice and have a canal refill the lake fine.  But I am not sure how much help the crater is then.
3) Day night and seasonal temperature flux.  How much atmosphere would you need to avoid nightly freezes outside of the lake?  Again, very much against the survival of significant plant cover.
4) What are you going to do about dust storms?

re your Qs:

1.  Ozone is slightly heavier-than-air on Mars, and hydraulic jump should slow wind in the crater, so that ozone is not lost quickly.  Soontiens et al. 2013. 

jas-d-12-0221.1-f2.gif

You'd just replenish at the loss rate, notionally with O2 manufacturing.  Or conceivably certain plants could perform that task; e.g. lichens, which can protect themselves against martian UV with screening pigments.  Brandt et al. 2015.

images?q=tbn:ANd9GcQyP1tHs6Vj-LEK4w2nRbyrxsx4Sc4i6lijkB4HE8unYlVEE4t1

2.  At most locations on the crater floor the impact debris and ice cover would limit evaporation and sublimation to < 1 cm per sol, and groundwater flow would at least partially replenish.  Detailed modeling of the post-impact water cycle will require a proper geological survey of the pre-impact site, but for some initial numbers, see this geophysical note.

3.  Nightly freeze is expected; very severe in winter.  Ice cover provides a measure of insulation, and ground heat can be distributed with hydrothermal irrigation channels, but you wouldn't expect all plants to survive the winter.  Some plants would be summer ornamentals, only, with annual reseeding.  Hence our term, "photosynthetic archipelago", indicating incomplete / discontinuous plant cover.

4.  The crewed facilities, as sketched, are subaqueous.  Therefore greenhouse plants would be protected against dust storms.  Storm effect on surface plants is tbd.

hab_rough_geometry_1280.png?zoom=1.125&fit=1280%2C598

Refs.

Brandt, A., de Vera, J. P., Onofri, S., & Ott, S. (2015). Viability of the lichen Xanthoria elegans and its symbionts after 18 months of space exposure and simulated Mars conditions on the ISS. International Journal of Astrobiology, 14(3), 411-425.

Soontiens, N., Stastna, M., & Waite, M. L. (2013). Numerical simulations of waves over large crater topography in the atmosphere. Journal of the Atmospheric Sciences, 70(4), 1216-1232.

#3 Re: Terraformation » Magnetizing Mars - Creation of a Martian Magnetosphere » 2018-07-27 20:33:16

SpaceNut wrote:

https://en.wikipedia.org/wiki/Saturation_%28magnetic%29

[Magnetic saturation] happens when the field will not get any large no matter how much power you apply to it.

No, the saturation of ferromagnetic-core electromagnets has nothing to do with the Omaha Field strength, obviously.  This is HTS current, commonly used to produce high-Telsa fields in fusion reactors.

Again, you're talking while in ignorance; overlooking the shielding results, along with the sim work and refs behind the results.

Can't you pull together even a casual post, after all this time?

2048x1536

#4 Re: Terraformation » Magnetizing Mars - Creation of a Martian Magnetosphere » 2018-07-27 17:35:51

SpaceNut wrote:

A loop field or something the size of a remnant field that already exist just stronger and is a power eater to maintain.

Oh, the physics dictate something like our Omaha Field.  In its first draft it's several orders of magnitude stronger than any remnant martian field, and once it's charged up it pulls < 80 kW indefinitely. 

Superconductors, you know?

If you don't read the Omaha Field material, you're just talking while in ignorance.  In which case, why bother with a forum?

#5 Re: Terraformation » "Developing Mars": a room.eu.com Special Report, Spring 2018 » 2018-07-27 15:17:50

Void wrote:

holes that are deep enough for a body of water to exist due to induced geothermal heat, and raised pressure, would be good places to locate cities, if it is not possible to elevate the entire atmospheric pressure of Mars in a reasonable time.

I wonder also if your impact causes a gain or loss of atmosphere.

Right, there's no net change in atmospheric mass, just a localized pressure increase on the new crater floor, to a seasonally-averaged pressure of ~ 1.3 kPa.  Enough for a lake and other reservoirs.

Void wrote:

You might also consider using an impactor to strike a deep ice deposit, creating a long term ice covered reservoir.  It could be quite useful as well.

The impactor does in fact strike ice.  The specifics are under NDA, but the selected target site is clearly ice-rich.

The resulting lake would be at least partially ice-covered through much of the year, unavoidably, due to the cold atmosphere above.

Void wrote:

If you can have one impact, why not others.

Did you see our note on asteroid 2005 LF8?

#6 Re: Terraformation » Magnetizing Mars - Creation of a Martian Magnetosphere » 2018-07-27 15:06:20

Elon has announced his method for re-creation of the martian magnetosphere.


MuskField.png?zoom=1.25&w=604


aka, "Omaha Field".


Fig7.png?resize=768%2C361

#7 Terraformation » "Developing Mars": a room.eu.com Special Report, Spring 2018 » 2018-04-23 23:18:27

Special Report topics:
- Mars consortia, to apply the best technology toward Mars habitation and industry
- Frontier commerce, in the spirit of the First Transcontinental Railroad
- Regional terraformation, for natural resources and improved environment at a selected Mars site
- Redirecting space mining investment: a possible shift from asteroids to Mars, for cost-effective mining and a Strategic Rare-Metal Reserve

Title and Link:
"Developing Mars"
https://room.eu.com/article/410.pdf

Abstract:
When people begin to live on Mars it is inevitable that fledgling businesses will spring up at permanent habitats. While there are a growing number of plans to transport people to the Red Planet, and even set up the first colonies, much remains to be done on the practicalities of settlement. Added resources such as ground heat, water and increased atmospheric pressure can be instrumental. The Lake Matthew Team (LMT) has invented the Mars Terraformer Transfer (MATT) to fill that void. In this bold vision the LMT proposes using laser-deflection technology to redirect a small celestial body to a 2036 Mars impact. The plan to create an impact crater, called "Omaha Crater", with lake, immense facilities and even summer plant life is innovative and not without risk. In this exclusive Special Report for ROOM two of those involved outline the idea and its ambitious goals, with a focus on the backbone of strategic and commercial opportunity.

First paragraphs:
This article introduces and outlines the MATT terraformation process and several core businesses that can put the terraformation resources to practical use. In doing so, it draws on analogies from frontier businesses of the First Transcontinental Railroad and the California Gold Rush in 19th-century America.

Terraformation resources can sustain and protect subaqueous natural-light habitation structures (‘habs’). Habs can be spacious, with practical scaling comparable to the largest terrestrial stadiums. This goal might seem unreasonable or impractical at first glance. However, the LMT has taken time to evaluate a suitable impactor and target site, and to detail reliable methods for a practical mission plan - practical in the programme-management sense of being attainable within reasonable constraints on time, money and resources. The mission plan completes a regional Mars terraformation in 2036, in good time to help pioneering crews...

ROOM_composite.png

#8 Re: Terraformation » Magnetizing Mars - Creation of a Martian Magnetosphere » 2018-04-23 23:11:11

IanM wrote:

Could anyone provide me a schematic/diagram for Lake Matthew Team's Omaha Field proposal, or a link to it? I've seen its claimed power requirements and energy-blocking capacity, but I'd like to be able to see a diagram of its circuitry and power sources if possible. Thanks!

The basic Omaha Field figures are given in the Mars Home Planet submission.  Note the use of straight cables, solenoids, and mixed cables in construction of the protective field.

Also the Omaha Field proposal is integrated into a greater Omaha Shield concept, described in a Nov. 16 2017 press release.

Bronze_votive_shield_icon.jpg

#9 Re: Human missions » Deep Space Gateway; a bad joke by NASA? » 2017-12-11 12:57:43

kbd512 wrote:

Any plan to fill BFS with 130t of water from an asteroid is an unnecessary and expensive diversion for something that's not an actual problem for the colonists and a problem that we just ignore for astronauts who repeatedly go to ISS.  The accumulated doses are no different, given their frequent missions to ISS...

Passive shielding is required for every space craft, but lighter passive shielding solutions exist right now (HDPE)...

Moon, not asteroid.  And Deimos is en route.

Water would be the easiest Deimos ISRU product, and easily transferred between Deimos and LEO.  Notably, unlike plastics or other fixed shielding, the water shield would not be lifted from a planetary surface, or lowered down to one.  The rocket equation really likes that.  Hence the given Omaha Trail flight efficiencies, which are not possible with a comparable fixed shield that's lugged from one planetary surface to another. 

Big efficiencies translate into big cost savings, which grow with the fleet; so the "expensive diversion" is actually status-quo thinking.

--

Speaking of status quo, yes, this is nominally a DSG thread.  And of course one can do a DSG one-off without water shielding, and just suffer per usual.  Why one would bother with that -- why one would spend far more than SpaceX to achieve far, far less -- is a question that needs asking. 

Likewise, the corollary question:  Why build an ITS infrastructure without first examining the efficiencies, cost savings etc. of the Omaha Trail?

#10 Re: Human missions » Deep Space Gateway; a bad joke by NASA? » 2017-12-07 20:41:11

SpaceNut wrote:
Lake Matthew Team - Cole wrote:
GW Johnson wrote:

It's fine (and fun) to dream up all these ways of doing things better,  utilizing resources predicted to be there at these various destinations.  The point I have tried to make in multiple threads on these forums is:  "you inherently do not know that those resources really are there,  until you actually go there and dig or drill".  Applies to Mars,  its moons,  asteroids,  comets,  and any other planet or moon. 

The feedback I keep getting is nothing but arguments-from-authority:  this or that paper or prestigious name says the buried resource stuff is there.  It's all based on remote sensing in one form or another,  precisely because no human has ever actually been there and dug or drilled...

Lumping us in with less informed [straw-man?] posters is inappropriate.  Rejected.  We do understand the literature, warts and all, and we apply it, even in our own novel designs.  As for Deimos:  We quantified the Deimos possibilities in forum, not you.  E.g. post 1, post 2.  That's not fallacious argument from authority, that's knowing more than you.

Anyone taking your own posts at face value would have been badly misinformed on that topic.  So before posting again, read our refs, and read something more; maybe then you'll have some information or self-correction for the thread.

And do keep it on-topic.  This is the thread for the new Omaha Shield proposal, specifically; not for rehashes of old and irrelevant text.

The origin of the Martian moons revisited by Pascal Rosenblatt Royal Observatory of Belgium 46th ESLAB Symposium: Formation and evolution of moons Session 5 – Observational constraints June 27th 2012 – ESTEC, Noordwijk, the Netherlands.

Like your above references these are all spectral for its color guess work via wavelength and other such optical, while they are probable and from other on the ground tests performed on Mars can be taken with a near acuracy for this data be used. Why as we used these same tools for mars before going and putting the rovers on the surface which has been comfirmation.

Abstract On the formation of the martian moons from a circum-martian accretion disk by Pascal Rosenblatt, Sébastien Charnoz

Rosenblatt et al. 2016 interprets previous work as setting an upper limit on the porosity of accreted moons:

Rosenblatt et al. 2016 wrote:

"up to 30% of the volume"

This max porosity is far below the 50%+ required of a dry Deimos. 

If a plausible mechanism is not found for 50%+ porosity, the magenta box will be not merely hard to hit, but edging off the dartboard.

Refs:

Rosenblatt, P., Charnoz, S., Dunseath, K. M., Terao-Dunseath, M., Trinh, A., Hyodo, R., ... & Toupin, S. (2016). Accretion of Phobos and Deimos in an extended debris disc stirred by transient moons. Nature Geoscience, 9(8), 581-583.

#11 Re: Human missions » Omaha Shield: radiation protection systems for Unlimited Mars Career » 2017-12-02 18:58:35

GW Johnson wrote:

I need not cite such papers for you,  go find them yourself.  I am not a name-dropper,  I don't have to be.  I have seen many dozens of papers in this topic...

Dozens.  Wow.

GW Johnson wrote:

I trust ground truth only.  As should you,  when lives are at stake.  Not to do so is unethical in the extreme.

As though no one had ever thought of these things, and more constructively. 

You should step away from the old punching bag; there are new things to talk about.

#12 Re: Human missions » Omaha Shield: radiation protection systems for Unlimited Mars Career » 2017-12-02 16:22:33

GW Johnson wrote:

It's fine (and fun) to dream up all these ways of doing things better,  utilizing resources predicted to be there at these various destinations.  The point I have tried to make in multiple threads on these forums is:  "you inherently do not know that those resources really are there,  until you actually go there and dig or drill".  Applies to Mars,  its moons,  asteroids,  comets,  and any other planet or moon. 

The feedback I keep getting is nothing but arguments-from-authority:  this or that paper or prestigious name says the buried resource stuff is there.  It's all based on remote sensing in one form or another,  precisely because no human has ever actually been there and dug or drilled...

Lumping us in with less informed [straw-man?] posters is inappropriate.  Rejected.  We do understand the literature, warts and all, and we apply it, even in our own novel designs.  As for Deimos:  We quantified the Deimos possibilities in forum, not you.  E.g. post 1, post 2.  That's not fallacious argument from authority, that's knowing more than you.

Anyone taking your own posts at face value would have been badly misinformed on that topic.  So before posting again, read our refs, and read something more; maybe then you'll have some information or self-correction for the thread.

And do keep it on-topic.  This is the thread for the new Omaha Shield proposal, specifically; not for rehashes of old and irrelevant text.

#13 Re: Human missions » Solenoid use with surface habitation units » 2017-12-01 15:38:38

A solenoid has low external B magnitude along its length, whereas a straight wire has maximum B magnitude.  For surface facilities, straight-wire shielding geometries are desirable.

For a first concrete example of a Mars facility field, see our initial design for the "Omaha Field," one component of the "Omaha Shield" proposal: 

Omaha Shield: radiation protection systems for Unlimited Mars Career

#14 Re: Human missions » Deep Space Gateway; a bad joke by NASA? » 2017-12-01 10:35:35

We can say that "Deimos' 1.5 g/cm3 is unlikely without volatiles," if we keep the possible components in mind.  For example, Rosenblatt 2011 lays out a range of conceivable porosity and water ice wt % values for several possible rocky components:

Deimos_Porosity_And_Water_From_Rosenblatt_2012.png

Duke et al. 2003 discusses lunar ISRU mining of 2 wt% water ice.  If we take that as the minimum useful %, and allow only anhydrous, dense rocks, an impractically dry Deimos has composition and porosity somewhere in the overlaid magenta box, at upper left in the second figure.

If that figure were printed and used as a dartboard, the small magenta box would be very hard to hit -- assuming blindfolded throws, of course.

Refs:

Duke, M. B., Blair, B. R., & Diaz, J. (2003). Lunar resource utilization: Implications for commerce and exploration. Advances in Space Research, 31(11), 2413-2419.

Rosenblatt, P. (2011). The origin of the Martian moons revisited. Astronomy and Astrophysics Review, 19(1), 1-26.  (Presentation 2012)

#15 Re: Human missions » Deep Space Gateway; a bad joke by NASA? » 2017-11-30 15:27:02

GW Johnson wrote:

I don't doubt that what you say is true.  I don't doubt that you are quoting some actual experts.  My point is that this is not the only explanation for a low density.  There is also (1) a dry rubble pile assembled with vacuum-containing voids due to extreme low gravity,  and (2) voids left behind when the water sublimed away long ago. 

But those aren't "popular" because they're unfavorable for planning missions based on exploiting local resources.  You don't need 50% water to achieve that low a density.  Something like ~25% vacuum-filled voids also explains it.  We've already seen other small bodies like that.

My other point is that you cannot know the buried (hidden) water content is really there until you actually go there and dig/drill for it.

"Popularity" isn't the driver here.  We do evaluate.  If you could be careful not to insinuate otherwise, that would be great.

--

Deimos' 1.5 g/cm3 is unlikely without volatiles.  Even Phobos' 1.9 g/cm3 is hard to compose dry.  Bell et al. note:

Bell et al. 1993 wrote:

To explain the observed [Phobos] density with pore space alone would require Phobos to consist of at least 50% empty space.  The only rocks with this much porosity are some lunar breccias which are soil rewelded by impact.  Thus an ice-free Phobos would have to be a rubble-pile consisting entirely of regolith.  This appears unlikely in view of the existence of large topographic features such as the walls of Stickney crater...

 
So a dry Deimos would need more than 50% empty space.  Britt and Consolmagno 2001 hypothesizes, qualitatively, that a dry Phobos and Deimos could be possible given a very robust macroporous size-sorting mechanism, but that hypothesis hasn't been pursued quantitatively.  And still, the magnetospheric data fits better with a volatile-rich origin than a dry origin.

Speaking of origin, the cometary possibility draws parallels with 3552 Don Quixote, a NEO cometary remnant having visible similarities to Deimos.  Lee 2017 reasons from the parallel for a hypothetical Deimos water ice component to 55 vol%. 

A Deimos sample mission would be needed to test everything, of course.

Anyway, there's reason to drive forward with ISRU research having Deimos as a proposed target.  New results and new ideas for ISRU are of interest. 

Refs:

Bell, J. F., Fanale, F., & Cruikshank, D. P. (1993). Chemical and physical properties of the Martian satellites. Resources of near-earth space, 887-901.

Britt, D. T., & SJ, G. C. (2001). Modeling the structure of high porosity asteroids. Icarus, 152(1), 134-139.

Lee, P. (2017, March). Phobos and Deimos: A Possible Comet Connection. In Lunar and Planetary Science Conference (Vol. 48).

#16 Re: Human missions » Deep Space Gateway; a bad joke by NASA? » 2017-11-29 21:23:02

SpaceNut wrote:

Since Mars had a remnant magnetic shielding in areas why no use long bar magnets on the hull to start the process of a shield and then create a static magnetic shield via RF transmission, one could seed the bubble with ionic elements that would be supended in the shield field.

I think that would also be subject to the M2P2 hotspot and breakage troubles Metzger was talking about.  Flares play rough.

For an EM shielding approach that does not use plasma, we can note the EU's SR2S effort, which ended in 2015.  That team innovated quite a lot, of necessity, but the work was not continued.

04.png
The pumpkin

Video:  SR2S Project Outcomes

Istituto Nazionale di Fisica Nucleare wrote:

The Roadmap

While we have found a new approach to the active protection with respect to the existing literature, we do not consider MT4 as the ultimate, optimized result. A systematic exploration could be carried on various kinds of “not fully confined” magnetic field configurations and geometrical coil layouts, which could deliver a similar or better result. The fractional contribution to the dose reduction due to the magnetic field suggests that there are “gaps” in the magnetic coverage, therefore the number of pumpkin coils can be increased/optimized. The mass of the coils could be further reduced by refining the optimization of the coil geometries and by applying advanced structural materials, whose cryogenic properties are not yet known.
Further steps of technical and conceptual developments have been identified and collected in the following SR2S roadmap:
- Increasing the TRL of the conductor (the SR2S prototype production allowed identifying the main issues);
- Optimization of the Active Shield configuration;
- Improving the pumpkin configuration in terms of number, shape, dimension and total current of coils as well as of their distance from the habitat;
- Studying new and innovative “not fully confined” magnetic field configurations and geometrical coil layouts, which could deliver a similar or better result;
- Deepen the knowledge of light structural materials. Within SR2S we proposed the use of many advanced materials but the cryogenic properties of most of them are not well known;
- Further development of the magnet cryogenics including enhancing of PHP TRL;
- Explore new solutions for quench detection and protections (non-insulated winding);
- Study of ancillary equipments like power supply or flux pump;
- More detailed studies of the shield assembling in orbit.

#17 Re: Human missions » Deep Space Gateway; a bad joke by NASA? » 2017-11-29 20:51:49

GW Johnson wrote:

I really,  really doubt whether there are any usable water resources at either Phobos or Deimos.  These resemble nothing so much as the small asteroids,  which seem to be very dry.  It is the much-larger asteroids that seem to be wet.  Somehow,  that should not be surprising,  since it takes cover with some weight to it to keep ice from subliming away in vacuum.

Actually, we chose Deimos with reason:  Low density of 1.5 g/cm3 is very hard to explain absent volatile component.  50 wt% is consistent with both density and magnetospheric evidence.  Water-evolution modeling suggests volatiles 20-60 m below polar surfaces.  CAVoR and coal gasification reactors frame ISRU methane, oxygen and water production, for breadboard benchmarking.

Refs:

Bell, J. F., Fanale, F., & Cruikshank, D. P. (1993). Chemical and physical properties of the Martian satellites. Resources of near-earth space, 887-901.

Berggren, M., & Zubrin, R. (2015).  Carbonaceous Asteroid Volatile Recovery (CAVoR) system.

Fanale, F. P., & Salvail, J. R. (1990). Evolution of the water regime of Phobos. Icarus, 88(2), 380-395.

Murchie, S. L., Fraeman, A. A., Arvidson, R. E., Rivkin, A. S., & Morris, R. V. (2013). Internal characteristics of Phobos and Deimos from spectral properties and density: relationship to landforms and comparison with asteroids.

Nichols, C. R. (1993). Volatile products from carbonaceous asteroids. Resources of near-earth space, 543-568.

--

Hi. 

We're the Lake Matthew Team

We don't need the grade and we don't work here, so please don't expect us to play along with dismissive hand-waving.

Thanks!

OmahaTrail5.png

#18 Re: Exploration to Settlement Creation » Radiation amount type risk mitigation » 2017-11-29 15:29:43

re: Radiation shielding produced by mini-magnetospheres

aka Sink or Swim in Space

Sure, transit EM shields are one complementary area of research; if an EM system could meet the GeV shielding requirement without crossing mass, power and safety redlines, why not consider it? 

However ISRU water shielding has some big advantages.  It works even when the fuse blows.  Also arguably it doesn't need multi-billion$ R&D to get off the drawing board. 

A better way of looking at it:  The Omaha Trail's ISRU water puts a cost-benefit curve out there.  Now it's a competition:  ISRU water vs. EM shielding.  :-)  If the EM curve can't rise above the water curve and deliver significantly more value for the money, EM transit shielding sinks, so to speak. 

As for M2P2 shielding, it doesn't look as though anyone's bothered with it, after that 2002 publication.  Maybe the issues raised in Metzger et al. 2004 were just too challenging.

Metzger et al. 2004 wrote:

...it seems to us that two problems exist.  First, the magnetic bubble has two poles located at the ends of the spacecraft, and therefore particles that follow the field lines will be directed in at both ends...  Second, it has been learned recently that magnetic structures in the solar wind frequently break the Earth's magnetic field lines and attach themselves to their ends.  This creates a direct thoroughfare of radiation into a "hotspot" region... the bubble might completely break and be swept away... leaving the spacecraft with no shielding at all just at the time it is needed the most.

#19 Re: Human missions » Deep Space Gateway; a bad joke by NASA? » 2017-11-29 13:04:47

GW Johnson wrote:

If you cluster some tanks like that around the outside of some part of the pressurized habitat,  they should make a pretty good solar flare shield.

Sure, but only for DSG, which isn't in transit to Mars.  Doesn't work for transit, because when it's time to return home from Mars... "Now where'd we put those external tanks?"

If mod wants to split this line of thought off to another thread, np.  Just wanted to apply your shielding knowledge to the challenge of cutting the 130-ton ITS water-shield.

#20 Re: Exploration to Settlement Creation » Radiation amount type risk mitigation » 2017-11-29 12:53:12

Antius wrote:

Regarding galactic cosmic rays - I wonder how much of the surface dose results from secondary particles generated in the Martian atmosphere?  These would presumably have lower energy but higher flux.  For lower energy charged particle radiation, a magnetic field would be an effective means of deflecting radiation and reducing dose rate.  A magnetic field protecting a base doesn't need to be mobile and a big iron core electromagnet might be an acceptable solution.  A vehicle could generate magnetic shielding whilst the engine was running and the crew could assemble a temporary dirt shield for those periods where the vehicle was not moving.

re: cosmic ray particles at Mars:  Yes, for example the proton flux peak is at lower energy at the base of the martian atmosphere than at the top.  Still, with a peak around 100 MeV, many of those lower-energy protons do still require robust shielding.

Omaha Field

If feasible, a magnetostatic shielding field would liberate surface operations considerably -- getting rid of the troublesome "dirt shield", for example.  Our "Omaha Field" proposal deflects protons near the martian surface, to ~1 GeV.  This catches more than half of GCR protons and nearly all solar flare protons.  (Max shielding in light green.)

Fig10.png

Suspended superconducting cables can deliver the required MA current for effective shielding, efficiently.  Our suggested field design makes use of them.

Fig5.png

#21 Re: Human missions » Deep Space Gateway; a bad joke by NASA? » 2017-11-29 11:44:32

RobertDyck wrote:

There's no oxygen in space. A liquid methane tank outside the pressurized hull would not have any chance of ignition.

Unless you plan on using your methane tank as an interplanetary heat shield, the methane adjoins crew quarters.  You think either is a good idea?

#22 Re: Human missions » Deep Space Gateway; a bad joke by NASA? » 2017-11-29 08:28:13

elderflower wrote:

How good is liquid methane as a shield?  Or even LOX. I'm thinking in terms of doughnut tanks with a shelter in the middle.

Methane's effective, yes, but there are many potential ignition sources in and around crew quarters.  I haven't heard of a crew shield design that accepts that risk.

#23 Re: Human missions » Deep Space Gateway; a bad joke by NASA? » 2017-11-28 21:41:39

SpaceNut wrote:

Space is cold so high temperatiure plastic will be brittle...but would work to hold the water....

Well, the additional shielding material would be in or around the water, and the water vessel adjoins crew quarters, so presumably the entire system would be held above freezing, which helps.

SpaceNut wrote:

Another materials is a blanket of Boron Nitride Nanotubes

So to get the water amount down such that we will have that mass for payload we will need more than 1 type of shielding method....

Yes, multiple methods could be used.  If some combination looks promising, we can work up a round-trip flight efficiency profile, to see how the numbers compare with Omaha Trail baseline. 

One complicating factor:  the water shield is transferred between Deimos and LEO, and between LEO and Mars EDL, so it's never included in the payload calculation.  That is, the water is never lifted from a planetary surface.  In contrast, any other, additional shielding material is lifted from planetary surfaces, and must be subtracted from payload.  For this reason any additional shielding material must reduce water mass very significantly, to justify itself. 

Mille-feuille (thousand-leaf)

One conceivable option:  Whereas small satellites might accommodate only a single graded-Z shield, an ITS spacecraft carrying Deimos water would have a much larger space for shielding.  Conceivably many extremely thin high-Z inserts could be stacked within the water vessel, arranged a bit like a mille-feuille pastry.  While each very thin graded-Z unit would give little shielding, the compounded iterative effect on primary and secondary particles might conceivably exceed first-order mass addition.  If, and only if, that proved to be the case, the effect would increase the net shielding beyond that of a single-insert design. 

It's just an idea; I wouldn't know if it's viable.  How to simulate accurately? 

Update:  SPENVIS is an interesting online tool for this purpose.  No guarantees of course, but it's a quick way to compare the merits of shielding ideas.  For example, a quick simulation of a 10-layer mille-feuille of tantalum and water is compared with a single unit of same mass.  First output suggests very similar proton shielding.

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#24 Re: Human missions » Deep Space Gateway; a bad joke by NASA? » 2017-11-28 14:45:10

Wrobel et al. 2017 Fig. 1 provides an existent analogue for the shielding case of "a thin layer of high-Z material... standing within the water volume".  The given polyetheretherkeytone / tungsten design is optimized for electronics shielding (protons + electrons), so it's not directly applicable.  It's just a tangible analogue for consideration, perhaps as starting point for thoughts on graded-Z improvements to the proposed water shield.

#25 Re: Human missions » Deep Space Gateway; a bad joke by NASA? » 2017-11-28 13:57:27

RobertDyck wrote:
Lake Matthew Team - Cole wrote:

A thin layer of high-Z material could be integrated into the water shield

Do you understand why that's a bad idea? First, you're using obscure terminology. 'Z' is simply the last letter of the alphabet, each field of science or engineering uses it for something different. In the field of radiation shielding, it's usually used to refer to atomic number. That is number of protons in the nucleus, or positive static charge of the nucleus. If you mean atomic number, then say atomic number.

Atoms with high atomic number also have high atomic mass. That's a problem, and something we've moved away from. The reason is heavy ion radiation of any sort (high energy or low) and medium ion radiation with high energy both cause secondary radiation on impact with anything with high atomic mass. Both the radiation particle and material from shielding split apart. Each heavy particle (radiation and shielding) becomes multiple smaller particles, each with lower energy. The shower of secondary radiation is far worse than the original radiation. A high calibre bullet becomes a shotgun blast. The shotgun pellets are smaller, lower mass, lower velocity, but there's a lot more of them. If you're at close range so you get impacted with most of the shot, it actually does more damage than the high calibre bullet. Same with radiation.

"High-Z" material is good for shielding against neutron radiation and gamma radiation. There isn't any neutron radiation in space. Any neutron radiation from stars outside our solar system are so far, the radiation takes so much time, that the half-life of a free neutron causes it to decay into a proton and electron, long before it reaches our solar system. Our Sun had nuclear fusion in its core, but no high energy fusion near the surface. I used to think neutron radiation would decay in transit from Sun to Earth, but nuclear physicists tell me the neutrons either are absorbed or decay before they leave the surface of the Sun. Some fancy 21st century instruments have used this, they detect neutron radiation created as secondary radiation from the impact of solar radiation with the surface of the planetary body (Moon or Mars), and measure what comes back. Most of that neutron radiation is absorbed by Mars atmosphere, but enough gets back to low orbit that instruments can measure the difference between high energy vs low energy neutrons. Of course, the Moon doesn't have an atmosphere, so the instrument works even better there; but Lunar Prospector had to be in low Lunar orbit to work. Bottom line: no neutron radiation in interplanetary space.

Lead or other "high-Z" material has been used for radiation shielding against nuclear bombs or nuclear reactors because they produce so much neutron radiation. Space is different, it has proton radiation and particle radiation consisting of atomic nuclei. Stopping that without causing more radiation than you're blocking requires "low-Z" material, preferably hydrogen.

Please don't pontificate: that was tedious.  And look at the noted research before posting.

Atwell et al. 2013 wrote:

This study investigated the use of Graded-Z materials for radiation mitigation of proton environments.  The results showed some slight dose reductions in using Tantalum or Tungsten with 5 g/cm2 of HDPE in a GCR environment...

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