NASA: We're sending humans to Mars

[mheslep]

I think Ceres would be a better place to go, expected to have a thick mantel that is largely water ice. Nearly 1000 km diameter.
Humans could tunnel into the ice and make an underground habitat, safe from vacuum, radiation, space debris.

Why is that an advantage? Humans could tunnel into Mars as well, which also has a little atmosphere to help out with radiation and descent.

More interesting place than Mars.

Why so?

 

[marcus]

Hello Mhes,
since you mentioned atmosphere helping with descent (e.g. parachutes) I will point out that it is costly to set things down on Mars surface and even more costly to get them up off the surface and in orbit.

The dawn (ion drive) craft is currently approaching Ceres gradually and will be captured by Ceres gravity around March 2015.
Ceres escape velocity is small. 500 meters per second

Water is valuable. Mars is comparatively dry and rocky, largely hardened volcanic residue. I would say it would be thankless job to bore tunnel into most places on Mars.

With Ceres, I am assuming (we will know more soon) that there is a thick outer ice layer that one could essentially melt a tunnel into. Not like boring into rock.

With a source of energy, to make heat and light, one could have several LAKES in ice caverns on Ceres. One lake might be home to aquatic life.

Another lake might be used for cooling the settlement's power plant.
====================

Why more interesting? I suspect Ceres is considerably OLDER material. More interesting to study.
Mars has undergone volcanism, geological changes similar to Earth, loss of volatiles. I suspect Ceres is closer to primordial solar system material.

Also more interesting to live in Ceres caves than in Mars caves, I suspect. Fun and challenging to learn how to thrive and remain healthy in lower gravity.
3% of Earth gravity. Humans could, of course FLY with their own muscle power, in a cavern's atmosphere. Flight could be a good way of getting exercise.:w

Surface gravity 0.28 m/s²

 

[mheslep]

Thanks for the response!

Hello Mhes,
since you mentioned atmosphere helping with descent (e.g. parachutes) I will point out that it is costly to set things down on Mars surface and even more costly to get them up off the surface and in orbit.

In other words, the difficulty of getting in/out of the larger gravity well trumps any advantages bestowed by the atmosphere (i.e. descent braking, radiation block)?

Water is valuable.

Good point. Plenty of oxygen in the surface material of the rocky planets and moons, but hydrogen seems to be rare on Mars.

Mars is comparatively dry and rocky, largely hardened volcanic residue. I would say it would be thankless job to bore tunnel into most places on Mars. With Ceres, I am assuming (we will know more soon) that there is a thick outer ice layer that one could essentially melt a tunnel into. Not like boring into rock.

Perhaps, though I'm skeptical. The large amount of energy required to heat and melt ice would melt several times as much common rock (Si, Al, Fe oxides).

...Fun and challenging to learn how to thrive and remain healthy in lower gravity.
3% of Earth gravity. Humans could, of course FLY with their own muscle power, in a cavern's atmosphere. Flight could be a good way of getting exercise.:w

Surface gravity 0.28 m/s²

Or 1/6th that of the Moon. I would have thought the Moon's gravity to be a low side limit for long term healthy and effective human operation.

 

[LeilaTesla]

Mars is in the development stage, and people only hamper

 

[Dotini]

A note of caution for deep space exploration from today's edition of spaceweather.com (12/7/14).

GROWING PERIL FOR ASTRONAUTS? NASA's successful test flight of Orion on Dec. 5th heralds a renewed capability to send astronauts into deep space. A paper just published in the journal Space Weather, however, points out a growing peril to future deep space explorers: cosmic rays. The title of the article, penned by Nathan Schwadron of the University of New Hampshire and colleagues from seven other institutions, asks the provocative question, "Does the worsening galactic cosmic ray environment preclude manned deep space exploration?" Using data from a cosmic ray telescope onboard NASA's Lunar Reconnaissance Orbiter, they conclude that while increasing fluxes of cosmic rays "are not a show stopper for long duration missions (e.g., to the Moon, an asteroid, or Mars), galactic cosmic radiation remains a significant and worsening factor that limits mission durations." This figure from their paper shows the number of days a 30 year old astronaut can spend in interplanetary space before they reach their career limit in radiation exposure:

According to the plot, in the year 2014, a 30 year old male flying in a spaceship with 10 g/cm2 of aluminum shielding could spend approximately 700 days in deep space before they reach their radiation dose limit. The same astronaut in the early 1990s could have spent 1000 days in space.

What's going on? Cosmic rays are intensifying. Galactic cosmic rays are a mixture of high-energy photons and subatomic particles accelerated to near-light speed by violent events such as supernova explosions. Astronauts are protected from cosmic rays in part by the sun: solar magnetic fields and the solar wind combine to create a porous 'shield' that fends off energetic particles from outside the solar system. The problem is, as the authors note, "The sun and its solar wind are currently exhibiting extremely low densities and magnetic field strengths, representing states that have never been observed during the Space Age. As a result of the remarkably weak solar activity, we have also observed the highest fluxes of cosmic rays in the Space Age."

The shielding action of the sun is strongest during solar maximum and weakest during solar minimum--hence the 11-year rhythm of the mission duration plot. At the moment we are experiencing Solar Max, which should be a good time for astronauts to fly--but it's not a good time. The solar maximum of 2011-2014 is the weakest in a century, allowing unusual numbers of cosmic rays to penetrate the solar system.

This situation could become even worse if, as some researchers suspect, the sun is entering a long-term phase of the solar cycle characterized by relatively weak maxima and deep, extended minima. In such a future, feeble solar magnetic fields would do an extra-poor job keeping cosmic rays at bay, further reducing the number of days astronauts can travel far from Earth.

To learn more about this interesting research, read the complete article in the online edition of Space Weather.

 

[Ken G]

That's an interesting analysis, but instead of plotting number of days for a given amount of shielding, they could equally plot the amount of shielding needed for a given number of days. That would seem to make more sense, and would not lead to such dire conclusions, merely a need for a small increase in shielding.

 

[marcus]

...
The large amount of energy required to heat and melt ice would melt several times as much common rock (Si, Al, Fe oxides).
...

You can melt ice with the waste heat from a power plant.
I don't know what kind of heating element you imagine being used to melt common rock. Might be more efficient to spend electric power to DRILL, in the case of rock.
In the case of ice you can use an electric powered drill to essentially the same effect, but also utilize waste heat at say 350 kelvin.

 

[marcus]

I think Ceres would be a better place to go, expected to have a thick mantel that is largely water ice. Nearly 1000 km diameter.
Humans could tunnel into the ice and make an underground habitat, safe from vacuum, radiation, space debris.
More interesting place than Mars. Dawn spacecraft is following Ceres along its orbit, gradually catching up with solar powered ion thrusters.
If successful should arrive at Ceres spring 2015, i.e. in a few months.

I favor robotic space exploration over human, as a general rule, but if humans are to colonize any time soon, don't bother with Moon or Mars, make it somewhere nice and icy.
http://neo.jpl.nasa.gov/orbits/fulltraj.jpg
You can see on the full trajectory map that the craft is now within 0.007409 AU of Ceres. the two dots are barely separable on the map. Here are some images from the craft's perspective.
http://dawn.jpl.nasa.gov/mission/live_shots.asp
I guess 0.007 AU is around a million km.

4 days ago (Thursday) when I posted last the Dawn craft was 0.007409 AU from Ceres, now the figure is 0.006721. The difference, 0.000688 AU, is 103,000 km
It is about 100 thousand kilometers closer to Ceres.
this 28 November entry is still the latest posting at the Dawn blog:
http://dawnblog.jpl.nasa.gov/2014/11/28/dawn-journal-november-28/#more-1533
The craft has been propelled almost exclusively by solar-powered xenon ion drive.

 

[mheslep]

The craft has been propelled almost exclusively by solar-powered xenon ion drive.

I would think a solar powered ion drive would not be useful past, say, Mars? And that therefore Dawn's ballistics were set well before approach to Ceres, with adjustments now made only by Dawn's hydrazine thrusters?

Ceres' orbit is 2.8AU, so solar insolation for Dawn nearby would be 1366/(2.8^2) or 174 W/m^2 if perfectly oriented. Assuming ~30% conversion PV, actual power collected is 52 W/m^2. Seems like weak sauce for an ion drive, and the remainder of the spacecraft power budget.

Edit: just watched a presentation by the Dawn Program Director:

...dominated by huge solar arrays... we're going far from the sun ... ion engines are power hungry. ... In fact when we launched, Dawn in 2007 this was the greatest tip to tip wingspan of any NASA interplanetary spacecraft : 65 feet from tip to tip...

http://www.jpl.nasa.gov/events/lectures_archive.php?year=2014&month=12

 

[zoki85]

Cool, but waste of money.

 

[marcus]

I would think a solar powered ion drive would not be useful past, say, Mars? And that therefore Dawn's ballistics were set well before approach to Ceres, with adjustments now made only by Dawn's hydrazine thrusters?
...

Apparently not so, though, Mheslep. The fulltraj link I gave earlier
http://neo.jpl.nasa.gov/orbits/fulltraj.jpg
shows that the ion thrusters have been on for almost the whole time since the craft left Vesta and started out for Ceres. And if you read the Dawn blog, e.g. http://dawnblog.jpl.nasa.gov/2014/11/28/dawn-journal-november-28/#more-1533
by Marc Rayman chief engineer and mission director, he reminds readers casually, but explicitly that it is the ion drive being used to get to Ceres.

Hydrazine is used primarily for controlling attitude. They had some mechanical trouble with one or more gyroscope wheels and had to use more hydrazine than expected to compensate, at one point. But it has never been the plan AFAIK to use hydrazine to, for example, get captured into orbit around Ceres.
You can see the very beautiful slow maneuver, ion-driven, that they plan to use, sketched in the 28 November edition of Dawn blog. I will get the link. Oh, already gave the link. Scroll down, the orbit plots are a ways down in the blog post.

 

[marcus]

The craft got out of its orbit around Vesta (using ion drive) in September 2012 and is now nearing Ceres. that is over 2 years. The solar powered ion thruster has been on nearly all that time. In the fulltraj map it looks like roughly halfway around the sun, a bit more, following an orbit intermediate between Vesta's and Ceres'. All that is well outside the orbit of Mars. Essentially all the impulse for that was solar-ion, not chemical.

If all goes as planned the craft will go into orbit around Ceres in March 2015 (using ion drive) So the solar powered thruster will have been on for about 2 and 1/2 years, getting it from Vesta to Ceres.

 

[mheslep]

Yes as I edited later, it appears Dawn has the most PV ever placed on an interplanetary craft (per Marc Rayman) something like 20 m^2 of PV, i.e. perhaps a kilowatt, largely to supply power to the ion drive. For thehttp://eo.ucar.edu/staff/dward/sao/fit/electric.htm (comparable?), a kilowatt apparently produced ~40 mN, or a delta-v of ~1300 m/s over a year for a 1000 kg craft (not counting the net gravitational forces).

 

[Monsterboy]

You can melt ice with the waste heat from a power plant.
I don't know what kind of heating element you imagine being used to melt common rock. Might be more efficient to spend electric power to DRILL, in the case of rock.
In the case of ice you can use an electric powered drill to essentially the same effect, but also utilize waste heat at say 350 kelvin.

How about Martian polar regions ? lots of water ice ,can be melted in order to build a base, right?

 

[marcus]

How about Martian polar regions ? lots of water ice ,can be melted in order to build a base, right?

Good thinking. I remember looking into that possibility some time back, to see if it had been studied. I tried to find information about the estimated depth, consistency (structural integrity) and year-round permanence of Mars polar ice.

that was before Google and Wikipedia :) so I spent a while at the Engineering library at the university campus near where I live. I didn't find much. Surely a lot more information about Mars "ice caps" is available now. Why don't you do some Google searches and see what can be found out.? Post some links for us.

For it to be interesting, the ice would need to be thick and solid enough that it would not develop leaks. It has to be able to contain a bubble of oxygen-containing atmosphere at pressure close enough to Earth normal for humans to breath comfortably.

The same structural concern applies to the idea of ice cave habitation on Ceres, which has the additional caveat about even lower gravity (3% of Earth normal).

A lot of information would need to be obtained about the actual composition and potential structural integrity of Ceres and or Mars polar ice material before people could actually seriously consider the ice cave idea. I still think it's quite interesting though.

I just checked the fulltraj page and saw that Dawn's distance to Ceres is now LESS than a million km.
http://neo.jpl.nasa.gov/orbits/fulltraj.jpg
Not much less, its range is now 0.977 million km.
You can see from the orbit map that from now on as it approaches it will be repeatedly turning OFF the ion thrusters for brief intervals. Little "blips" of zero thrust so as to gradually match speed. Not to overshoot when it arrives.
These show up as little gaps in the bright blue line on the map.

We should be able to tell something at least about the surface and mantel consistency from the pictures, assuming the craft makes its way successfully into orbit and starts taking photographs.

 

[Monsterboy]

Good thinking. I remember looking into that possibility some time back, to see if it had been studied. I tried to find information about the estimated depth, consistency (structural integrity) and year-round permanence of Mars polar ice.

that was before Google and Wikipedia :) so I spent a while at the Engineering library at the university campus near where I live. I didn't find much. Surely a lot more information about Mars "ice caps" is available now. Why don't you do some Google searches and see what can be found out.? Post some links for us.

For it to be interesting, the ice would need to be thick and solid enough that it would not develop leaks. It has to be able to contain a bubble of oxygen-containing atmosphere at pressure close enough to Earth normal for humans to breath comfortably.

The same structural concern applies to the idea of ice cave habitation on Ceres, which has the additional caveat about even lower gravity (3% of Earth normal).

A lot of information would need to be obtained about the actual composition and potential structural integrity of Ceres and or Mars polar ice material before people could actually seriously consider the ice cave idea. I still think it's quite interesting though.

I just checked the fulltraj page and saw that Dawn's distance to Ceres is now LESS than a million km.
http://neo.jpl.nasa.gov/orbits/fulltraj.jpg
Not much less, its range is now 0.977 million km.
You can see from the orbit map that from now on as it approaches it will be repeatedly turning OFF the ion thrusters for brief intervals. Little "blips" of zero thrust so as to gradually match speed. Not to overshoot when it arrives.
These show up as little gaps in the bright blue line on the map.

We should be able to tell something at least about the surface and mantel consistency from the pictures, assuming the craft makes its way successfully into orbit and starts taking photographs.

http://en.m.wikipedia.org/wiki/Planum_Boreum
The northern ice cap is about 3 kms thick and mostly water ice, the southern ice cap is also equally thick.
http://www.lpi.usra.edu/meetings/polar98/pdf/3048.pdf
It is said that dry ice will be too unstable to get that thick hence most of the ice cap must be made of water ice.

NASA could conduct experiments on Antarctica to build an underground(or under-ice) base , this might have been attempted already I don't know.

Maybe the next set rovers on Mars should be made to land on the poles and check out the ice.

Only reason why i don't feel comfortable with Ceres is that its gravity might reduce our bones to jelly and we will have to work out a lot to prevent that, Mars looks better on this aspect.

 

[mheslep]

I'm curious as to *why* the ion drive is cycled on and off, through out the entire mission per the trajectory map. I would guess to give time for heat rejection (ion drive grid?), but perhaps the cycling is a part of the trajectory scheme (which I don't understand).

 

[marcus]

I'm curious as to *why* the ion drive is cycled on and off, through out the entire mission per the trajectory map. I would guess to give time for heat rejection (ion drive grid?), but perhaps the cycling is a part of the trajectory scheme (which I don't understand).

Look at the fulltraj map record of the trip out to vesta and the trip from vesta to ceres (almost complete).

the ion drive (light blue) has been on for several months at a time. Evidently there is no need to operate intermittently.

it is only now as they are approaching Ceres that they plan to shut it off intermittently, less frequently at first, but more and more little breaks in operation as they approach the planet. It's a good lesson for us in how spacecraft with solar ion thrust operate, and maneuver.

I'm not sure but I think if someone is willing to learn (open to new concepts) they could also learn something from the 28 November Dawn block which shows plots of two different trajectories for approach to Ceres. the craft "eases" into the desired orbit in a rather graceful way. Several of us might enjoy checking that out.

 

[marcus]

Thanks for the links! 3 kilometers sources good!
You are right about under-ice experimentation. Pressurize to test for air retention. Measure factors involved in stability: stalactite growth, differential melt and freeze, structural strength and reliability, air-lock design for connection with surface, power plant operation with in-cave cooling. small nuclear power units as in submarines. Artificial light in the cave, to grow food. I haven't heard of any Antarctic experiments like that. Why don't you write a letter to someone in NASA?

...

NASA could conduct experiments on Antarctica to build an underground(or under-ice) base , this might have been attempted already I don't know.

Maybe the next set rovers on Mars should be made to land on the poles and check out the ice.

Only reason why i don't feel comfortable with Ceres is that its gravity might reduce our bones to jelly and we will have to work out a lot to prevent that, Mars looks better on this aspect.

I agree, a rover should land on one of the poles and check it out! this would be so fine! I don't understand why they have not done it already, the polar icecaps are the most interesting parts of Mars, in the long run.

About jelly bones, that is very serious, but humans are an adaptable species and might habituate to work out enough that they can thrive in 3% gravity.

Think about a circular bicycle track with almost vertical walls. If the radius of the circle is 10 meters then you have to pedal almost 10 meters per second in order to experience 1 gee. That is, V²/R. And if the radius is 20 meters, then you have to go 14 m/s. And there are those contraptions at the gymnasium.
Flying might help, not sure about that. Maybe with pedal-powered helicopters, and doing aerobatics. Vigorous airborne acrobatics. Challenging problems, requires creative solutions involving understanding what humans enjoy by way of exercise, mental emotional factors as well as anatomical.

 

[mheslep]

Look at the fulltraj map record of the trip out to vesta and the trip from vesta to ceres (almost complete).

the ion drive (light blue) has been on for several months at a time. Evidently there is no need to operate intermittently.

Probably so, though it may be that the lower solar loading on the spacecraft at Ceres' orbit allows for continuous operation.

 

[marcus]

Dawn's distance to Ceres now 900,000 km
More exactly
.006035 Astronomical Units = 902 823.15 kilometers
according to the current fulltraj update.
http://neo.jpl.nasa.gov/orbits/fulltraj.jpg

I'll check the mission director's blog ("Dawn Journal") to see if he has anything new:
http://dawnblog.jpl.nasa.gov/2014/
No, this 28 November entry is still the latest
http://dawnblog.jpl.nasa.gov/2014/11/28/dawn-journal-november-28/#more-1533

Ceres data:
http://en.wikipedia.org/wiki/Ceres_(dwarf_planet)

 

[Monsterboy]

Thanks for the links! 3 kilometers sources good!
You are right about under-ice experimentation. Pressurize to test for air retention. Measure factors involved in stability: stalactite growth, differential melt and freeze, structural strength and reliability, air-lock design for connection with surface, power plant operation with in-cave cooling. small nuclear power units as in submarines. Artificial light in the cave, to grow food. I haven't heard of any Antarctic experiments like that. Why don't you write a letter to someone in NASA?

This has not been done probably because NASA currently has no plans to build bases on Mars.
I don't know anyone in NASA ,perhaps some people in PF actually work in NASA ??

I agree, a rover should land on one of the poles and check it out! this would be so fine! I don't understand why they have not done it already, the polar icecaps are the most interesting parts of Mars, in the long run.

There was one attempt to land near the poles (Mars polar lander) ,it failed because it crash landed! ,i too don't understand why the polar ice caps remain unexplored ,perhaps there is some technical difficulty in landing something over the poles ?
If we land people on Mars ,it will mostly probably be near the poles right? radiation levels will be lower there and water will be available in the required quantity right?
If we ever find life on Mars ,that too is mostly likely to happen in the polar regions ,since several metres deep water ice can reduce radiation levels to that of Earth's hence photosynthetic life might be possible within the ice layers of the polar regions.

 

[Monsterboy]

http://astrobiology.nasa.gov/articles/2014/5/15/destroying-glycine-in-ice/
Now some astrobiologists say even under ice ,life is difficult to be sustained on Mars but the article doesn't mention depth of water ice required to sustain life.

 

[marcus]

It's really two questions. They were talking about photosynthetic life. that has to be near enough the surface of the ice to get light. So there is no question of going deep enough to be safe from radiolysis of glycine. Those are issues about the possibility of life emerging and evolving independently on Mars long ago, and issues about the preservation of traces of life, in the ice, from which we could learn about prior history.

But clearly those research issues do not affect the practicality of operating a base safely under Mars ice caps, only (indirectly) one of the motivations for doing so.

Thanks for the interesting links! I think you are right about all the points you made. I still suspect it would be more interesting to establish a human settlement on Ceres. Partly because there's expected to be a lot MORE ice---deeper and planet-wide---so room to expand and a good way to cool thermodynamic power cycles, if our species learns to thrive in 3% gravity. More place to go if you're successful.
Partly because the gravity is so weak it would be easier to land and take off.
Partly because IF our species ever finds reason to utilize or settle more parts of the solar system, Ceres could provide WATER MORE CHEAPLY than the Earth could. Water for life and industrial processes, hydrogen and oxygen for propulsion. So there is a long-range reason to want to utilize (if not actually settle on) Ceres.

We won't actually know much for sure about the place until the Dawn craft arrives in March 2015. So I'm just speculating. But it seems likely to be a ball largely of water ice (density estimated 2 g/cc) with escape velocity about 500 m/s, one is naturally interested :w

 

[Hercuflea]

Fabulous. Even though they could have done this in the 70s on nuclear thermal rockets...

I have more faith in private space companies.

 

[mheslep]

Fabulous. Even though they could have done this in the 70s on nuclear thermal rockets...
...

Do you have an example design in mind? Yes the nuclear power was available, the liftoff thrust was available, the specific impulse was an improvement over chemical rockets, but I don't know of anything in that era with the required specific impulse to go orbit hopping as has Dawn, i.e. an ion drive above 3000 seconds. Nuclear explosive propulsion (Orion) does not count.

 

[zoki85]

I think attempt to go to Mars in '70s had more chances to end in tragedy than not.

 

[HowardHughes]

So basically when NASA gets there, there will already be a fully established colony set up a decade before by SpaceX and co.

 

[marcus]

More about the conjecture that Mars might have a reservoir of subsurface ice in the "Northern lowlands":
http://science.nasa.gov/science-news/science-at-nasa/2014/19dec_marswater/

Dawn spacecraft distance from Ceres is now 787,000 km (i.e. 0.005261 AU)

As I recall it was 900,000 km from destination last Saturday, so in about 6 days it has closed in by more than 100,000 km. Seems to be on schedule to reach Ceres by 1 March. Will have to begin slowing down in order not to overshoot I suppose. Maybe gravity (orbital dynamics) will take care of that if it just turns off the solar-electric thrusters now and then.

 

[Kechel8]

Spectacular! Do we send matthew mcconaughey? ;)