New Mars Forums

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."

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.

"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.

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."

In my ignorance,  I would guess the most practical source of oxygen on Mars to be mined water.  One would use the vapor pressure rise upon heating to self-compress a batch of confined ice to usable pressures (near 1 atm).  Then just do solar PV electrolysis.  It's a whole lot easier to compress the hydrogen and oxygen from 1 atm into 2000 psig bottles than it is from 6 mbar. 
What one does with the hydrogen is not well understood by me.  It should be possible to make methane from it and the CO2,  but the source of the CO2 makes a big difference to practicality.  Compression from 6 mbar is a real practical problem,  while dry ice can only be mined at the poles (same self-compression mechanism as water ice). 
GW

DEEP BLUE ICE? The Martian regions depicted in dark blue may hold buried deposits that are up to 50 percent water ice. Light blue regions may hold lesser amounts. White arrows at left and right denote the approximate landing sites (red dots) of Viking 1 and Viking 2, respectively.

Feldman and Boynton note that the discovery of hydrogen-rich material on Mars needn't have waited until the 21st century. The lander on each of the Viking missions, which arrived at Mars in the mid-1970s, scraped trenches 10 to 20 cm deep to sample the arid soil. The new data from Odyssey suggest that Viking 1 dropped into an area on Mars with little if any buried ice. Viking 2, however, descended in a region apparently endowed with some buried, hydrogen-rich material. After a trip of more than 100 million kilometers, the lander may have stopped digging just a few centimeters shy of striking ice.

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What I do see though is a lot of frustration people have with NASA coming up with ridiculously large mission mass. And thus a lot of architectures that are attacking the problem from particular directions. Mars direct is largely a response to the NASA overkill. I kinda like it in some ways. Its got a certain minimalism. But, for me the solution ultimately lies in something a bit more considered, a bit more conservative, but still not wasteful either...

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The problem is low frontal thrust density in the thin air above 60 thousand feet.  All airbreathers are afflicted by that.  Not even flying super fast with scramjet overcomes it.  You either stay low and lose all your impulse advantage in drag,  or you have to burn rocket and airbreather in parallel to achieve enough frontal thrust to climb/accelerate in the thin air.  I just don't see any way around that dilemma.  I see the potential for a lot of "gravy train" R&D programs,  but I don't see much potential for anything we might actually fly. 
The UK Skylon engine faces the same problem.  They're pretty much done the airbreather by 80 thousand feet,  gone to rocket only mode.  For them,  that's about Mach 4.  Surprise,  surprise!
GW

For a launch from a carrier aircraft, the aircraft speed will directly reduce the Δv required to attain LEO. However, the majority of the Δv benefit from an air launch results
from the angle of attack of the vehicle during the release of the rocket. An
ideal angle is somewhere of the order of 25° to 30°.
A study by Klijn et al. concluded that at an altitude of 15250m, a rocket launch with the
carrier vehicle having a zero launch velocity at an angle of attack of 0° to
the horizontal experienced a Δv benefit of approximately 600 m/s while a launch
at a velocity of 340m/s at the same altitude and angle of attack resulted in a
Δv benefit of approximately 900m/s. The zero launch velocity situations can
be used to represent the launch from a balloon as it has no horizontal velocity.
Furthermore, by increasing the angle of attack of the carrier vehicle to
30° and launching at 340m/s, a Δv gain of approximately 1100m/s
was obtained. Increasing the launch velocity to 681m/s and 1021m/s produced a
Δv gain of 1600m/s and 2000m/s respectively.
From this comparison, it can be seen that in terms of the Δv gain, an airlaunch is
superior to a ground launch. As the size of the vehicle decreases, this superiority
will have a larger effect due to the increased effective drag on the vehicle.

GW Johnson wrote:

The stuff I came up with is extremely experimental,  but it handled as if it were commercial Styrofoam (somewhere near 0.03 g/cc).  I used 0.2 inches of it in a ramjet combustor running at almost 4000 F,  and it withstood the extremely-violent effects of rich blow-out combustion instability repeatedly,  while serving for hours of accumulated burn in dozens of tests.  I cannot go that hot for entry,  I must avoid shrinkage cracks by staying under 2350 F,  just like shuttle tile.  but,  that's where refractories can take us.  I think they are the ultimate winner for entry heat shielding.

Have you patented this? You should think about doing so.

I posted a handful of times pre-crash. I'm delighted to (belatedly) discover that the New Mars Forums are up and running again. Well done!

Yesterday I attended a seminar given by Don Hassler, the PI for the RAD instrument on MSL. The topic was the radiation flux observed during cruise from Earth to Mars, and what conditions have been like on the Martian surface.
The fairly constant background of Galactic Cosmic Radiation (GCR) dominated the cruise dose, though he pointed out that if you had a big enough solar flare it could have delivered a comparable dose (they did in fact see 5 moderate flares during cruise, but they contributed only ~5% of the total amount of radiation).
Being inside the MSL capsule in cruise provided a significant amount of shielding, comparable to that on the ISS (something on the order of 20g/cm2). About 500 mSv was accumulated during cruise, which would be roughly half an astronaut's typical career allowance. Don mentioned that a manned cruise would be designed to be shorter for than a robotic mission, and pointed out that shielding around sleeping quarters using drinking water/propellant tanks could significantly reduce the amount of radiation received.
On the Martian surface RAD has seen radiation fluxes values ~1/2 of what it did in cruise. This is basically because half the sky is blocked by the planet. The thin Martian atmosphere itself offers a level of protection comparable to the MSL capsule structure.

Midoshi:

Do you know what orbit that the Kepler telescope is in?  Could this trajectory thingy get us a trajectory to rendezvous with it? 

I ask,  because repairing Kepler would be a very worthy mission for men to undertake outside LEO.  The more-challenging analog to repairing Hubble.  And that had very widespread support. Both in Congress and among the people.   

Something like that is the kick-start needed to get men flying beyond LEO again.  Get that done,  and Mars is not far behind,  asteroids or not. 

GW