Yet another Mars architecture

RobS · 2013-08-13 06:43:32

My guess--I don't know whether my guess is worth much--is that if one drills down 50 to 100 meters, one will encounter disseminated ice; basically, a frozen water table. Mars has ice at the equator every few million years when the axial tilt gets high, and it may evaporate away later, but some will remain underground. But we will need a team on Mars to drill down to get the disseminated ice, and we will need to experiment with the technology. Getting the ice out may not be hard; circulate warmed Martian air down the hole and extract the water vapor from it when it comes back up.

RGClark · 2013-08-13 08:44:15

RobS wrote:

My guess--I don't know whether my guess is worth much--is that if one drills down 50 to 100 meters, one will encounter disseminated ice; basically, a frozen water table. Mars has ice at the equator every few million years when the axial tilt gets high, and it may evaporate away later, but some will remain underground. But we will need a team on Mars to drill down to get the disseminated ice, and we will need to experiment with the technology. Getting the ice out may not be hard; circulate warmed Martian air down the hole and extract the water vapor from it when it comes back up.

The very key fact is that at mid latitudes it does not have to be 10's of meters below the surface but in fact 10's of centimeters below surface. Note these are not polar locations or even near polar locations. The latitude is comparable to that of New York City on Earth.
This is a very exciting discovery in relation to the life on Mars question because with the salts expected to be on Mars such locations in the near surface would be within the temperature range for liquid water brines. Here is another article discussing the Mars Odyssey discovery:

Mars Water, Odd Surface Features Tied to Life.
By Leonard David
Senior Space Writer
posted: 07:30 am ET
28 March 2003

"It really is changing the way we think of how the ice formed," Boynton told SPACE.com . The idea that water vapor eked down to depths deep enough and cold enough to condense out does not seem to account for the vast amounts of water ice detected, he said.
There's no telling how deep the ice might extend just below surface on Mars, Boynton said. It could be several hundreds of feet to well over a mile in depth.
"All of a sudden you're starting to talk about a pretty significant amount of water," Boynton said. "It looks like the Viking 2 landing site was actually right on top of this ice. If its robot arm had dug just a little bit deeper they would have found it," he said.
As for life being preserved in the ice or still kicking today, Boynton said that, with reasonable confidence he believes there's loads of ice on Mars. "If there is something that is happy living in ice…it is going to be very happy there," he said.

http://web.archive.org/web/200310110853 … 30328.html

This near surface ice at mid latitudes on Mars has been confirmed by Mars Reconnaissance Orbiter:

Water Ice Exposed in Mars Craters.
by Andrea Thompson | September 24, 2009 02:18pm ET
090924-ice-crater-02.jpg?1292269321

The craters are about 12 feet (, which ranged from 1.5 to 8 feet (about 0.5 to 2.4 meters) deep, were located at five Martian sites.
Though the MRO researchers had identified 80 to 90 craters around the Martian globe before, this was the first time the spotted ice in the bottoms, likely because most of the others were more southerly and outside of the likely area of subsurface water ice.
Byrne told SPACE.com that it was surprising to the team to find the bluish ice, though "in retrospect maybe it shouldn't have been." Scientists knew of the existence of underground ice and had been monitoring craters as they formed, but "I guess we didn't put the two together," he said.
Several of the craters were also near the landing site of the Viking Lander 2. Viking also looked for water ice on Mars, but was only able to dig down about 6 inches (15 cm) below the surface ? about 4 inches (10 cm) shy of where Byrne and his colleagues think the ice table sits.
"It's a shame that didn't happen," Byrne said. "You might have been having this conversation 30 years ago."

http://www.space.com/7333-water-ice-exp … aters.html

I don't know which of the methods of producing propellant from either the air or the subsurface ice would be easiest. I'd like to see both of them tried by precursor robotic lander missions.

Bob Clark

GW Johnson · 2013-08-13 08:58:54

Seems to me that someone identified what may be dust-covered glaciers or other massive ice in the northern lowlands. That would be in the ancient sea-bottom, near the old shoreline. I don't remember exactly where this was, and it was reported a few years ago. I never heard how this discovery panned out, but I do remember photos of what looked like dirt-covered chunks of sea-surface pack ice. I don't remember the scale of the photos, but my impression was that these chunks were very large, perhaps km in dimension.

If this interpretation could be confirmed, then we have have a promising landing site with scads of minable water not covered with monolithic rock. We'll need to include a deep drill rig and probably some kind of bulldozer and backhoe with the ISPP/ISRU plant that we land. There's your hydrogen (and some oxygen).

In the northern lowlands, it might not be that hard to freeze-out some dry ice, precisely because it is cold. Once solid, it's easy to pressurize CO2 to many bars by confined (solar or waste) heating, no moving parts, nothing to regenerate. Even easier than that absorption thing, and maybe lighter and more reliable, too. There's your carbon. LOX-methane is a nice propellant combination. Better than kerolox Isp, and almost as dense.

I wonder whatever became of that identification of dirt-covered ice, and if there is any way to confirm/deny it with the data we have, and the assets already orbiting Mars? That would seem to be a very important piece of info that we need for planning any manned landing.

GW

RGClark · 2013-08-14 09:09:14

Mars rover confirms dangers of space radiation.
Future manned missions to Mars will need internal shielding and advanced propulsion systems to shorten transit times, minimizing exposure to space radiation, scientists say.
by William Harwood May 30, 2013 3:06 PM PDT

Chris Moore, deputy director of advanced exploration systems at NASA headquarters, said shorter transit times and improved shielding will be needed to protect future deep space crews.
"To get really fast trip times to cut down on radiation exposure we'd probably need nuclear thermal propulsion, and we're working with the U.S. Department of Energy to look at various types of fuel elements for these rockets," Moore said.
"But it's a long-range technology development activity and it will probably be many years before that is ready. But it is part of our design reference mission architecture for sending humans to Mars.... That could probably cut the (one-way) trip time down to around 180 days."

http://news.cnet.com/8301-11386_3-57586 … radiation/

An expensive and far off development using nuclear propulsion that is already controversial and would still only make the travel time 6 months(!)
This is a big reason why I argue for getting the propellant from the Moon. That way we would have virtually unlimited amount of propellant to drastically cut the travel time, no new expensive, (potentially) dangerous, far off propulsion systems required.
I estimate by using a Saturn V size vehicle with all hydrolox propulsion, launching from low lunar orbit or L2, we could make the trip in two weeks.

Bob Clark

Last edited by RGClark (2013-08-14 09:10:58)

GW Johnson · 2013-08-14 15:01:02

Sorry, Bob. I was responding to Terraformer's question about a reusable SSTO spaceplane, presumably horizontal takeoff.

Actually, I quite agree with you about one-shot throwaway SSTO rockets. The original Atlas was very nearly one. The Titan II first stage certainly was one. You can have a higher payload fraction as TSTO, but at a higher launch price. Whichever flings payload to orbit at lowest overall $/payload mass is the choice most folks will select (especially if they fail to consider the effects of not flying at full load). The 1960-on engine technologies and the modern stage structural fractions in the 5-10% range make SSTO vertical launch rockets quite feasible.

A reusable vehicle is another ball game entirely. There is just no way, even with modern materials, to survive entry and fly again with structural fractions in the 5-10% range. I'd be very surprised (and pleased) to see a design at 20% inerts that actually proves-out reusable with a "reasonable" life. I think real vehicles like that will fall in the 25-35% structural inert range.

Not even the miracle composites we now have are going to help, because of ascent and descent aeroheating, tumbling airloads aside. All the organic composite matrices are debris and powder by 290 F (143 C). Tumbling airloads just make that problem immensely worse, or else you must carry the weight for thrusters and drogues to control vehicle/stage attitude very carefully.

And we haven't even begun to talk about ocean or dry-land surface impact loads with any practical chutes. There's a reason 1/4 inch steel plate is considered to be "wastepaper trim material" by marine/shipbuilding engineers, and it is a bloody good reason, too.

GW

Terraformer · 2013-08-14 21:06:43

The correct thread is here. Perhaps Josh will move the post and merge it?

RobS · 2013-08-14 23:02:41

Regarding the radiation issue, nuclear thermal doesn't help. If you go to Mars faster, you can't aerobrake; the atmosphere isn't thick enough (according to Zubrin) if transit times are less than 5 months. So if you go faster, you have to haul along the fuel to stop, then the fuel to return to Earth faster as well. It's simply not feasible, from everything I have read.

RobertDyck · 2013-08-15 01:06:36

GW Johnson wrote:

Seems to me that someone identified what may be dust-covered glaciers or other massive ice in the northern lowlands.

That's right! That may be the ideal spot.

EU Space Probe Photographs Pack Ice on Mars - February 28, 2005
Radio-Transparent Deposits in the Elysium Region of Mars as Observed by MARSIS and SHARAD Radar Sounders - 2007
8° North, below the datum, flat/smooth, and ice.

RGClark · 2013-08-15 06:59:33

RobS wrote:

Regarding the radiation issue, nuclear thermal doesn't help. If you go to Mars faster, you can't aerobrake; the atmosphere isn't thick enough (according to Zubrin) if transit times are less than 5 months. So if you go faster, you have to haul along the fuel to stop, then the fuel to return to Earth faster as well. It's simply not feasible, from everything I have read.

If you have unlimited propellant such as from lunar-derived propellant depots that's not a problem with either nuclear propulsion or chemical propulsion. I prefer chemical propulsion since it's already here.

Bob Clark

RobS · 2013-08-15 07:41:11

Well, you never have "unlimited propellant." There are always costs and complexity issues. It is also not clear the radiation hazard is that serious. Some people are worried by the data; some are not. You could also wrap hydrogen and oxygen tanks around the crew compartment, or even ten tonnes of water, and reduce the radiation hazard. That'd be cheaper than thousands of tonnes lunar propellant.

Last edited by RobS (2013-08-15 07:44:00)

Terraformer · 2013-08-15 07:57:46

If you have lunar fuel, you can afford to build a 2-300 tonne mothership with plenty of radiation shielding. Use the Falcon Superheavy, two launches, maybe. Or launch an empty hull, just a basic spacecraft with rockets, fuel tanks and space for a habitat, then use a load of smaller launches with whatever cheap small craft we have by then to outfit it, before loading it up with fuel to launch it to L1. Then loading it again with it's fuel and crew to get to Mars. At Mars, use Deimos to repeat the process...

RobS · 2013-08-15 07:59:09

A great plan with a LOT of assumptions!

Terraformer · 2013-08-15 08:37:31

There's only really two - a Lunar infrastructure, and Musk delivering on his promise. Three if you include the ramjet TSTO...

RobertDyck · 2013-08-15 09:44:00

You will never afford heavy radiation shielding. Cost will always be an issue, and that means mass will always be an issue. Always. You could try for light weight shielding, such as mini-magnetosphere, or just go anyway. It's already been pointed out that risk of cancer from radiation for a trip to Mars and back is less than smoking.

RGClark · 2013-08-15 10:03:40

RobertDyck wrote:

The neutron spectrometer on Mars Odyssey detected hydrogen in the surface of Mars. It was estimated that space radiation (solar and GCR) that is the basis of this instrument had penetrated up to 1 metre. The Gamma Ray Spectrometer detected large chunks of ice. These instruments found a great deal of ice at or near the poles. However, there's practically none at or near the equator. There is a little at the bottom of ancient river channels, but you don't want to land in the bottom of a canyon. You want to land somewhere flat and smooth. You also want to send a human mission to some place relatively warm (not so cold). Ideal is near the equator, or at least between the lines of latitude that is the tropics. It feels odd talking about tropics on Mars, but it's the line of latitude that equals the axial tilt. Only one location has subsurface water, and flat/smooth, and tropical latitude. Unfortunately it's a high plateau, so relatively little atmosphere to protect against radiation. That's Meridiani Planum, where Opportunity landed. Opportunity examined the ground, and did not find obvious ice like Mars Phoenix did. Subsurface ice is not EVER going to be easy, so designing a mission to rely upon it is foolish.

A high hydrogen content area near the equator is actually Arabia Terra which is next door to Meridiani Planum. See the image in this article:

July 31, 2012
How Much Water is Inside Mars?
--- The interior of Mars appears to be as wet as the interior of Earth.
Written by G. Jeffrey Taylor
Hawai'i Institute of Geophysics and Planetology

Map of the H2O concentration in the upper few tens of centimeters of the martian surface, as measured from orbit by the Mars Odyssey Gamma Ray Spectrometer (GRS). Equatorial Mars (about 45 degrees north and south) contains between 2 and 7 wt.% H2O, and polar regions contain much more. The GRS actually measured hydrogen (H), but those concentrations have been converted to H2O. In reality, much of the water may be in the form of OH bound in minerals.
http://www.psrd.hawaii.edu/July12/water … -Mars.html

The Mars Odyssey scientists because it is a near equatorial site suggested the water was most likely in chemically bound form such as clays. It still will be possible to remove the water by heating but not as easily as for the case of pure ice.

The Opportunity landing site is at 2 degrees South, 354.5 degrees East (5.5 degrees West).This is about at the center of this map, not in the relatively high water area of Arabia Terra, which is a little higher and to the right. Even here though judging from the graphic, the GRS readings suggest approx. 5% wt. water there. This is expected to lie 15 to 20 cm (6 to 8 in) below the surface according to the GRS, with hydrogen-poor soil above. Interestingly Opportunity did dig a trench at the landing site:

February 17, 2004
Opportunity Digs; Spirit Advances.
http://marsrover.nasa.gov/newsroom/pres … 0217a.html

But this was only 10 centimeters (4 inches) deep. We wouldn't want a scenario like what happened with Viking 2 with the ice just inches below the depth of the trench it dug. I suggest Opportunity also be tasked with digging deeper trenches to the depth expected of the material with the high-hydrogen content.

Bob Clark

RobertDyck · 2013-08-15 18:35:03

Excellent map! This one is from the gamma ray spectrometer, not neutron. Different data, this one looks for high concentrations. Most maps available recently do not clearly show anything. It's amazing how poor calibration can obfuscate. This one shows a much larger, but less localized deposit on Arabia Terra. And a second just south of the equator, at 180° longitude. But that's where Spirit landed. It looked promising, but Spirit had difficulty finding water. Elysium Terra is a very large area, but some is below the datum. Definately worth looking at; potential Mars base location. But again, Spirit landed there. Water isn't going to be easy to find.

RobertDyck · 2013-08-18 04:37:30

I'm watching the Mars Society Convention via livestream. Thursday they had a plenary about what should be the next mission. It sounded like that talk was based on this discussion. So they're reading our stuff! Dr. Zubrin argued against sample return, basing his argument on a ridiculously complicated mission architecture.

Today the JPL manager for Mars rovers gave a talk, and one question was about sample return. It turns out JPL is planning the 2020 rover to collect samples, then cache them in a container about the size of a coconut. A second later rover will have to come pick them up. Then a return vehicle will send them to a location near Earth, where a human mission with an Orion spacecraft launched by SLS will rendezvous and grab the samples. That will return to Earth. What!?!?!? He argued ISPP is not mature enough to actually use it. The person who asked the question raised the point the current architecture is far more risky. The JPL manager calmly claimed all technologies in his plan are demonstrated, including rendezvous with manned vehicle. He also referred to sample return as a $4 billion mission.

In another talk, Robert Zubrin said for the same weight as Curiosity, you could land a fully fuelled return vehicle and a tiny rover to collect samples from the immediate vicinity.

I would like to propose an alternative. Since the 2020 rover is a copy of Curiosity, which is great but by 2020 it will be "been there, done that". So my proposal is to replace that mission with a less expensive one. Rather than land a fully fuelled return vehicle, instead use ISPP. Fully demonstrate Robert Zubrin's ISPP, which means bringing hydrogen from Earth. If this requires another technology demonstrator in a laboratory on Earth, then do so. The Mars lander would include a rover about the size of Sojourner. While Spirit and Opportunity were the size of a golf cart, and Curiosity the size of an SUV, Sojourner was the size of a radio controlled toy car. Return the sample directly to Earth, similar to JPL mission "Stardust".

Cost of this mission? Mars Phoenix cost $325 million; but used previous equipment. They started with the Mars 2001 Lander, which was never launched, then modified it to become Phoenix. The Mars Exploration Rovers, Spirit and Opportunity, cost $820 million. Continued operation adds to that, but that's what they cost to develop, build, launch, and land. This proposal is for just one lander. Could it be done for $400 million, full-up? That would put it in the category of "Scout", not "Discovery" or "Flag ship". The Scout program required $485 million or less. That program was retired in 2010, MAVEN will be the last Scout. But still, keeping the budget to that constraint would make it more likely to happen.

Last edited by RobertDyck (2013-08-22 22:03:49)

GW Johnson · 2013-08-22 08:25:51

Can't do probes forever, unless we never send men. There seems to be little interest in sending the "right" probes: it's boiling down to either/or sending ISRU demos vs. sample return, not both. This is not looking very good.

GW

RGClark · 2013-09-24 22:21:42

RGClark wrote:

Mars rover confirms dangers of space radiation.
Future manned missions to Mars will need internal shielding and advanced propulsion systems to shorten transit times, minimizing exposure to space radiation, scientists say.
by William Harwood May 30, 2013 3:06 PM PDT
Chris Moore, deputy director of advanced exploration systems at NASA headquarters, said shorter transit times and improved shielding will be needed to protect future deep space crews.
"To get really fast trip times to cut down on radiation exposure we'd probably need nuclear thermal propulsion, and we're working with the U.S. Department of Energy to look at various types of fuel elements for these rockets," Moore said.
"But it's a long-range technology development activity and it will probably be many years before that is ready. But it is part of our design reference mission architecture for sending humans to Mars.... That could probably cut the (one-way) trip time down to around 180 days."
http://news.cnet.com/8301-11386_3-57586 … radiation/
An expensive and far off development using nuclear propulsion that is already controversial and would still only make the travel time 6 months(!)
This is a big reason why I argue for getting the propellant from the Moon. That way we would have virtually unlimited amount of propellant to drastically cut the travel time, no new expensive, (potentially) dangerous, far off propulsion systems required.
I estimate by using a Saturn V size vehicle with all hydrolox propulsion, launching from low lunar orbit or L2, we could make the trip in two weeks.

Further on the radiation issue for manned flights to Mars:

Manned mission to Mars an unlikely proposition.
Current limits on exposure to radiation make chances of flight in near
future pretty slim.
Sep. 22, 2013
Written by Todd Halvorson FLORIDA TODAY

It's "the elephant in the room," NASA Chief Astronaut Robert Behnken
recently told a National Academy of Sciences committee.
"We're talking about a lot of ionizing radiation, almost a guarantee for
cancer, and you are really close to the edge of the range for lethal
exposure," said Kristin Shrader-Frechette, a University of Notre Dame
professor and a specialist in ethical issues that arise in scientific
research and technology development. "If we can't get shorter transit times
in space, and we can't get better shielding, then we really can't do (a
Mars) spaceflight."

http://www.floridatoday.com/article/201 … roposition

A near term solution is already apparent: lunar derived propellant depots.

Bob Clark

GW Johnson · 2013-09-25 10:06:19

Bob:

I found a NASA document on-line that describes the astronaut rules for radiation exposure, which allow higher levels than for civilians here on Earth. There's a monthly limit of 25 REM, an annual limit of 50 REM, and a career total limit that varies by gender and age.

Using GCR that varies sinusoidally from 24 REM/year (2 REM/month) at solar max to 60 REM/year (5 REM/month) at solar min, and 2.5 years for a total mission time, the total absorbed GCR can range 60 REM to 150 REM on the mission.

This ignores the half-sky shielding effect for the year spent on Mars or in close orbit, waiting to return.

GCR is fundamentally un-shieldable by any technology or science that we have. But, the other source is brief bursts of solar flare radiation, which we can shield, with about 20 cm of water or wastewater packaged around some designated shelter area. So, the leakage through the flare shield adds what the planet-shielding effect subtracts, roughly. And my doses listed above serve as good estimates of the rates and totals of all forms.

Monthly is no problem. Annual is a problem at solar min conditions, with 60 REM/year vs 50 allowable. Career limits are no problem at solar max at all, and no problem at solar min for males as young as age 25, being right at the 150 REM limit. Females need to be about age 31 or 32 to have a limit equal to the solar min exposure total of 150 REM. They have no problem as young as age 25 for solar max career exposures.

The only problem I see is for annual exposures is during a mission pretty-much "centered" at solar min, when the annual exposure rate is higher than allowed under those astronaut rules. But, lots of (nearly all) astronauts will still volunteer for this mission, in part because it's not that big a violation of the limits, at 60 vs 50 REM annual. For missions "centered" the other 68-69% of the solar cycle, the exposure will not exceed the 50 REM annual limit.

My point is, under NASA's own rules, radiation is not a show-stopper for sending men to Mars. These rules are at least 20 years old now. Why this is being ballyhooed in the press of late is a mystery to me, unless it is really being used to justify deciding not to go.

However, I would recommend that any Mars mission crewmembers not fly in space outside the Van Allen belts ever again. They will be close to career exposure limits after going to Mars, especially for a mission flown near or at solar min.

GW

Last edited by GW Johnson (2013-09-25 10:12:18)

RobertDyck · 2013-09-25 19:56:23

GW Johnson wrote:

GCR is fundamentally un-shieldable by any technology or science that we have.

Actually, that depends. Reports from the team for the MARIE instrument on Odyssey include estimated shielding for Mars atmosphere. The atmosphere of Mars itself is very effective shielding against heavy ion GCR. However, the lighter the particle, the less effective.

Their bar graph shows about 90% blocked at a 2km above the datum, such as Meridiani Planum. And about 98% blocked at the datum. The chart doesn't show data below the datum. It does show at different altitudes; I'm calculating percentage based on cell hits from this chart's data for 8km altutide. So this is atmosphere only; half-sky shielding is included in 8km data, what I'm using for the base-line. Note: Gale Crater is 2km below the datum, and Utiopia Planetia is 3km below. Unfortunately atmosphere is much less effective vs medium ion, and even less so vs light ion.

My conclusion is never even think of leaving astronauts stranded in Mars orbit. Get them down to the surface right away. That's the only protection against GCR.

GW Johnson · 2013-09-27 07:27:43

That's amazing that such a thin atmosphere could be such an effective shield against GCR as it is. I would not have expected that.

My statement about "non-shieldable" was referring to spacecraft design. Wasn't thinking about atmospheric shielding down on the planet.

GW

RobS · 2013-09-27 08:42:17

Robert, can you send us a link for the web page you are looking at? I am skeptical, if GCR is galactic cosmic radiation. Certainly, the Martian atmosphere is reasonably effective at stopping solar radiation; it provides 170 kilograms per square meter or 17 grams per square centimeter of shielding (remembering that you have to convert 7 mb of pressure into mass by multiplying by 2.6). But cosmic radiation would zip right through that, it seem to me.

RobertDyck · 2013-09-28 03:42:48

Please pardon the capitals, the title is copy-and-paste from the paper itself. I saved a copy on the local chapter website, to ensure it's available.

RADIATION CLIMATE MAP FOR ANALYZING RISKS TO ASTRONAUTS ON THE MARS SURFACE FROM GALACTIC COSMIC RAYS

http://chapters.marssociety.org/winnipe … -Paper.pdf

Look at the 3D bar charts on page 20. There are two charts: solar minimum, and solar maximum. The caption says:
"Figure-4. Comparison of calculated particle hits per cell per year at the skin on the Martian surface for solar minium and solar maximum conditions. Calculations include the average body shielding on the skin for the 50% percentile male [16]. Results for protons, alpha, light, medium, and heavy charge groups are shown."

RobS · 2013-09-28 06:02:05

Thanks, the paper is very complete and clear. It's too bad it's so hard to shield against light particles! But this also makes it clear that a shelter on Mars or even on the moon that is well shielded by water or regolith will provide good protection.

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