Author Topic: Strange story on Mars missions  (Read 11950 times)

Offline Takalok

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Strange story on Mars missions
« on: 04/02/2008 01:41 pm »
Fox News (website):
http://www.foxnews.com/story/0,2933,344491,00.html

What's weird about this story, is that theses risks have been know FOREVER, and yet they're trumpeting them like it's something new, or might be a show stopper for the current efforts.  Also, they do not cite any sources.  

Hmmmmm.   Get's my "I'm suspicous" antennae twitching.

Anyone know if there's anything political up right now that might prompt some FUD regarding Mars??

Life is what happens while you're waiting for tomorrow.

Offline Jim

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Re: Strange story on Mars missions
« Reply #1 on: 04/02/2008 02:17 pm »
No conspiracy just a slow news day

Offline Blackstar

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Re: Strange story on Mars missions
« Reply #2 on: 04/02/2008 02:30 pm »
Quote
Jim - 2/4/2008  9:17 AM

No conspiracy just a slow news day

Not exactly.  There's a new NRC report just released addressing this subject.  See:

http://nationalacademies.org/morenews/20080331.html


Offline rsp1202

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Re: Strange story on Mars missions
« Reply #3 on: 04/02/2008 04:23 pm »
What's the rad count on Spirit and Opportunity?
Did ALSEP measure radiation levels?

Offline Blackstar

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Re: Strange story on Mars missions
« Reply #4 on: 04/02/2008 04:27 pm »
Quote
rsp1202 - 2/4/2008  11:23 AM

What's the rad count on Spirit and Opportunity?
Did ALSEP measure radiation levels?

I don't think that the rovers have radiation counters.  That's partly the problem--the science program has not collected the kind of data that is required for the human exploration of Mars.  There are several types of data that are needed, such as radiation and toxicology (key question: is the Mars dirt toxic to humans?).

Offline hyper_snyper

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Re: Strange story on Mars missions
« Reply #5 on: 04/02/2008 04:30 pm »
Quote
Blackstar - 2/4/2008  12:27 PM

Quote
rsp1202 - 2/4/2008  11:23 AM

What's the rad count on Spirit and Opportunity?
Did ALSEP measure radiation levels?

I don't think that the rovers have radiation counters.  That's partly the problem--the science program has not collected the kind of data that is required for the human exploration of Mars.  There are several types of data that are needed, such as radiation and toxicology (key question: is the Mars dirt toxic to humans?).

Interesting, does Phoenix have instruments that can do that?  What's planned for MSL?

Offline brihath

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Re: Strange story on Mars missions
« Reply #6 on: 04/02/2008 05:35 pm »
Quote
Blackstar - 2/4/2008  10:30 AM

Quote
Jim - 2/4/2008  9:17 AM

No conspiracy just a slow news day

Not exactly.  There's a new NRC report just released addressing this subject.  See:

http://nationalacademies.org/morenews/20080331.html


Planned missions will be of longer duration than back during Apollo and astronauts will be at greater risk of being exposed at times of higher solar activity.  Back then, I believe the missions were scheduled at times of lower activity.  Perhaps that is why the focus is being intensified now.  I don't think it is anything really new, though.

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Re: Strange story on Mars missions
« Reply #7 on: 04/02/2008 07:11 pm »

Quote
Blackstar - 2/4/2008  11:27 AM  
Quote
rsp1202 - 2/4/2008  11:23 AM  What's the rad count on Spirit and Opportunity? Did ALSEP measure radiation levels?
 I don't think that the rovers have radiation counters.  That's partly the problem--the science program has not collected the kind of data that is required for the human exploration of Mars.  There are several types of data that are needed, such as radiation and toxicology (key question: is the Mars dirt toxic to humans?).

For what its worth, you don't always need them - you can do a good estimate of dosimetry from  other sources of information. One trick was to track errors in RAM/flash memory, another was for embrittlement, yet another involves paint changing color. You then cross correlate to get a common exposure.


Offline TyMoore

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Re: Strange story on Mars missions
« Reply #8 on: 04/02/2008 07:49 pm »
I think this illustrates not only the need for more research--but also a different philosophy regarding mission architectures: either we need to think of sending larger vessels that are better shielded to protect crews, or we need to send the crew on a faster vessel so that the total radiation 'integration time' will be less.

Either way, a manned mission to Mars is likely to cost more than we think. But that is the way of things...

Offline Blackstar

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Re: Strange story on Mars missions
« Reply #9 on: 04/02/2008 07:50 pm »
Quote
nobodyofconsequence - 2/4/2008  2:11 PM
For what its worth, you don't always need them - you can do a good estimate of dosimetry from  other sources of information. One trick was to track errors in RAM/flash memory, another was for embrittlement, yet another involves paint changing color. You then cross correlate to get a common exposure.

To see what the experts have said about the requirement for accurate radiation measurements on Mars prior to a human mission, see this report titled "Safe on Mars":

http://www.nap.edu/openbook.php?isbn=0309084261

Offline simonbp

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Re: Strange story on Mars missions
« Reply #10 on: 04/02/2008 09:56 pm »
IIRC, the only radiation detector yet flown has been MARIE on Mars Odyssey, which got fried by a solar flare in 2003. MSL will make the first surface level measurements...

http://en.wikipedia.org/wiki/Mars_Radiation_Environment_Experiment

Simon ;)

Offline rsp1202

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Re: Strange story on Mars missions
« Reply #11 on: 04/02/2008 10:58 pm »
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simonbp - 2/4/2008  2:56 PM

. . . the only radiation detector yet flown . . . got fried by a solar flare . . .

Kinda answers all my questions.


Offline Blackstar

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Re: Strange story on Mars missions
« Reply #12 on: 04/03/2008 02:13 am »
Quote
TyMoore - 2/4/2008  2:49 PM

I think this illustrates not only the need for more research--but also a different philosophy regarding mission architectures: either we need to think of sending larger vessels that are better shielded to protect crews, or we need to send the crew on a faster vessel so that the total radiation 'integration time' will be less.

Yeah, those are some options.  But they're not the only things that you'd want to do.  There are essentially two threats from radiation--solar flares and galactic cosmic radiation.  The latter is there the whole time and all you can do is shield against it, or try to shorten the trip.  There are some things that you can do about solar flares.  One is to fly during a quiet solar period to reduce the danger.  Another is to increase forecasting.  

I listened to some solar scientists talk about this stuff once and it's rather interesting.  They compare it to weather forecasting 40 years ago.  They can predict some big things with greater accuracy, but one of the problems is that the prediction times are not very long.  There are also some unique methods, such as looking _through_ the sun to find out what is happening on the other side (because eruptions on the opposite side are reflected through the sun and show up on the side we see).  One problem with Mars, however, is that it is going to be on the other side of the sun for a good period of time during any astronaut trip, so we could detect solar eruptions that are coming toward Earth, but we might not see ones heading toward Mars--and the astronauts.

There are people thinking about things like forecasting solar flares, and they think that some of this stuff is solvable, if the right money and attention is paid towards it.

There are also other ways to mitigate the hazards.  One possibility is developing drugs to decrease the dangers of radiation exposure.  I know nothing about that area, but I'm not optimistic.  Radiation slices through DNA strands, and I don't know how a drug can stop that from happening.

Offline Avron

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Re: Strange story on Mars missions
« Reply #13 on: 04/03/2008 03:00 am »
Quote
rsp1202 - 2/4/2008  6:58 PM

Quote
simonbp - 2/4/2008  2:56 PM

. . . the only radiation detector yet flown . . . got fried by a solar flare . . .

Kinda answers all my questions.


And that flare was not predicted...  I would like to see them reading if the next detector makes it to mars, what I would like even more is to see what it reads on the journey to mars

Offline A_M_Swallow

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Re: Strange story on Mars missions
« Reply #14 on: 04/03/2008 09:54 am »
Quote
Blackstar - 3/4/2008  3:13 AM

I listened to some solar scientists talk about this stuff once and it's rather interesting.  They compare it to weather forecasting 40 years ago.  They can predict some big things with greater accuracy, but one of the problems is that the prediction times are not very long.  There are also some unique methods, such as looking _through_ the sun to find out what is happening on the other side (because eruptions on the opposite side are reflected through the sun and show up on the side we see).  One problem with Mars, however, is that it is going to be on the other side of the sun for a good period of time during any astronaut trip, so we could detect solar eruptions that are coming toward Earth, but we might not see ones heading toward Mars--and the astronauts.

There are people thinking about things like forecasting solar flares, and they think that some of this stuff is solvable, if the right money and attention is paid towards it.

There are also other ways to mitigate the hazards.  One possibility is developing drugs to decrease the dangers of radiation exposure.  I know nothing about that area, but I'm not optimistic.  Radiation slices through DNA strands, and I don't know how a drug can stop that from happening.

Sounds like a solar observing satellite is needed in a HELO orbit around Sun-Earth L2.

Offline Blackstar

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Re: Strange story on Mars missions
« Reply #15 on: 04/03/2008 06:53 pm »
Quote
A_M_Swallow - 3/4/2008  4:54 AM

Quote
Blackstar - 3/4/2008  3:13 AM

I listened to some solar scientists talk about this stuff once and it's rather interesting.  They compare it to weather forecasting 40 years ago.  They can predict some big things with greater accuracy, but one of the problems is that the prediction times are not very long.  There are also some unique methods, such as looking _through_ the sun to find out what is happening on the other side (because eruptions on the opposite side are reflected through the sun and show up on the side we see).  One problem with Mars, however, is that it is going to be on the other side of the sun for a good period of time during any astronaut trip, so we could detect solar eruptions that are coming toward Earth, but we might not see ones heading toward Mars--and the astronauts.

Sounds like a solar observing satellite is needed in a HELO orbit around Sun-Earth L2.

I'm not an expert on this, but I think that you need at least two spacecraft.  You need to get stereo data in order to figure out the dimensions of the flare.  It may be that the best approach would be several spacecraft in solar polar orbits, so you're able to look down on the flares and can see them heading towards Mars, but there are probably several ways of approaching the problem.  As I said, I'm not an expert.

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Re: Strange story on Mars missions
« Reply #16 on: 04/03/2008 07:19 pm »
Not to belabor the obvious, but the Sun has been in its inactive phase and yet had quite a number of unpredictable "events", all of which would have been fatal to a crew in a heavily shielded aluminum cylinder. Also, the average number of extrasolar radiation events per year isn't zero - these are harder because they can be non electrostically or electromagentically deflectable, and can be TEV energies.
You want to hide in a big block of carbon(better) or silicates - like an asteroid.

The radiation hazard has been ridiculously played down over the years, to the point where many think it isn't a problem. What it is, is a hard problem.

I read this article as linked to funding efforts to revive funding, as NASA Life Sciences budget has been routinely gutted for such work. Partly they want DOD/DOE funding as well for obvious reasons. Since this is a 40+ year project, its hard to secure funding and easy to lose it, because you're not going to produce breakthrough results in a year (or five).

If we have our first Mars astronaut heros, it would be kind of nice if they get to live long enough for a few years of speeches and ticker-tape parades, don't you think?

Offline Blackstar

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Re: Strange story on Mars missions
« Reply #17 on: 04/03/2008 11:49 pm »
Quote
nobodyofconsequence - 3/4/2008  2:19 PM
The radiation hazard has been ridiculously played down over the years, to the point where many think it isn't a problem. What it is, is a hard problem.

It's been played down by some people, like Bob Zubrin.  It's a problem, but one that can be managed.  What you do is you build in procedures and systems to reduce the risk as much as possible, and then you accept a higher level of risk.

Offline khallow

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Re: Strange story on Mars missions
« Reply #18 on: 04/04/2008 12:54 am »
Quote
nobodyofconsequence - 3/4/2008  12:19 PM

Not to belabor the obvious, but the Sun has been in its inactive phase and yet had quite a number of unpredictable "events", all of which would have been fatal to a crew in a heavily shielded aluminum cylinder.

If the shielding is inadequate against what sounds to be routine events, then it's not "heavily shielded". It can still be "heavy" though.
Karl Hallowell

Offline rsp1202

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Re: Strange story on Mars missions
« Reply #19 on: 04/04/2008 01:33 am »
Quote
nobodyofconsequence - 3/4/2008  12:19 PM
. . . the Sun has been in its inactive phase and yet had quite a number of unpredictable "events", all of which would have been fatal to a crew in a heavily shielded aluminum cylinder.

Not any more. Things have picked up.

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Re: Strange story on Mars missions
« Reply #20 on: 04/04/2008 01:57 am »

Quote
khallow - 3/4/2008  7:54 PM  If the shielding is inadequate against what sounds to be routine events, then it's not "heavily shielded". It can still be "heavy" though.

Its not mass that matters - its atomic scattering cross section actually. Best per unit mass is carbon. Best per volume is water. Again for uncharged particles.


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Re: Strange story on Mars missions
« Reply #21 on: 04/04/2008 02:07 am »

Quote
Blackstar - 3/4/2008  6:49 PM   It's been played down by some people, like Bob Zubrin.  It's a problem, but one that can be managed.  What you do is you build in procedures and systems to reduce the risk as much as possible, and then you accept a higher level of risk.
Zubrin's time scale is different than NASA's. He's worried that we'll all sit on our collective rears given any excuse like radiation. He's correct in that we need not be detoured by radiation.

What the "accept higher level of risk" side has been looking at is altering biological systems to cope with ionizing radiation damage in a radical way. The funding for it has been on and off and is what I've been referring to.

In a "Dr. Strangelove" kind of way, the current jerks in power like/hate it. The part they like is to be able to imagine its use with man generated radiation sources (euphamistically). They really want to"love the bomb" e.g. atomic power widespread. They think of it like a second oil empire. 


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Re: Strange story on Mars missions
« Reply #22 on: 04/04/2008 02:11 am »

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rsp1202 - 3/4/2008  8:33 PM   Not any more. Things have picked up.

Yes - both with the sun and extrasolar sources. We're also finding more interesting extremely high energy events that we didn't quite have the instrumentation to measure well (GRBs).

In no way has the situation gotten better for manned spaceflight. But we are getting more realistic. 


Offline Blackstar

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Re: Strange story on Mars missions
« Reply #23 on: 04/04/2008 02:24 am »
Quote
nobodyofconsequence - 3/4/2008  9:07 PM
What the "accept higher level of risk" side has been looking at is altering biological systems to cope with ionizing radiation damage in a radical way. The funding for it has been on and off and is what I've been referring to.

In a "Dr. Strangelove" kind of way, the current jerks in power like/hate it. The part they like is to be able to imagine its use with man generated radiation sources (euphamistically). They really want to"love the bomb" e.g. atomic power widespread. They think of it like a second oil empire.


Ooookaaaayyyy....

Meanwhile, those of us who live on planet Earth have lost you...

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Re: Strange story on Mars missions
« Reply #24 on: 04/04/2008 07:39 am »

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Blackstar - 3/4/2008  9:24 PM  Ooookaaaayyyy....  Meanwhile, those of us who live on planet Earth have lost you...

Yeah, me too. I listened and didn't quite believe it either. Just what I heard between one group trying to get funded, and who they were introduced to ...  


Offline Blackstar

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Re: Strange story on Mars missions
« Reply #25 on: 04/04/2008 12:01 pm »
Quote
nobodyofconsequence - 4/4/2008  2:39 AM

Quote
Blackstar - 3/4/2008  9:24 PM  Ooookaaaayyyy....  Meanwhile, those of us who live on planet Earth have lost you...

Yeah, me too. I listened and didn't quite believe it either. Just what I heard between one group trying to get funded, and who they were introduced to ...  


You misunderstand.  I consider what you wrote to make no sense at all.

Offline William Barton

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Re: Strange story on Mars missions
« Reply #26 on: 04/04/2008 12:22 pm »
Would kerosene or liquid methane make a good shielding medium? It's high carbon/hydrogen and fairly dense. Just trying to think of a shielding material you could get some other use out of (like water).

Offline TyMoore

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Re: Strange story on Mars missions
« Reply #27 on: 04/04/2008 01:04 pm »
Sure you could use those...the US NAVY uses a large diesel fuel tank as a partial radiation shield between the reactor and the rest of the sub--and the fuel is also important for run a diesel backup generator for emergency power if something bad happens...

High density polyethylene panels can act as thermal insulation, micrometeoroid bumper panels, and radiation shields. But you can't just use one method--defense in depth as far as radiation goes. Interspersed within the micrometeoroid shields, I would put a couple of layers of high-Z (high molecular weight material) like a tungsten-rhenium foil--dense, high-Z materials interact strongly with heavy and heavily charge nucleii (like cosmic iron nucleii)--this creates a shower of smaller but still very energetic particles. Use a thick tank of water (30-70 cm thick--more is better) to try to catch the rest...

Also, nestling the pressurized crew compartments in among the propellant tanks and mission payload would help..but this will screw up the direct views (I guess you could put a bunch of TV cameras on the outside though...)

Honestly though, unless we're willing to send a "Death Star" the passengers are going to get hit by cosmic rays--there's nothing we can do about it.

Go fast, go big, and carry lots of shielding...

...or accept that the crew will have increased risk of cancer in long run...

The Apollo astronauts were well briefed on the likely risks they would encounter during their missions--they went into space anyways with their eyes wide open.


Offline Garrett

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Re: Strange story on Mars missions
« Reply #28 on: 04/04/2008 01:52 pm »
Quote
TyMoore - 2/4/2008  7:49 PM

I think this illustrates not only the need for more research--but also a different philosophy regarding mission architectures: either we need to think of sending larger vessels that are better shielded to protect crews, or we need to send the crew on a faster vessel so that the total radiation 'integration time' will be less.

Hmmm, I'm not an expert but I don't think it's really possible to send a faster vessel if we want to use a Hohmann transfer orbit to Mars, which is the only transfer orbit that we seem capable of performing with today's technology.

I'd imagine a good idea would be to place the water tanks in such a way that they surround the sleeping quarters and/or are more on the Sun side of the sleeping quarters. That should give a bit more protection from the neutral particles. I presume magnetic/electric shielding is envisaged to protect against the charged particles? You could also attempt to ionize the neutrals and then divert them using magnetic/electric fields.
- "Nothing shocks me. I'm a scientist." - Indiana Jones

Offline grakenverb

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Re: Strange story on Mars missions
« Reply #29 on: 04/04/2008 02:08 pm »
Quote
TyMoore - 4/4/2008  9:04 AM

Also, nestling the pressurized crew compartments in among the propellant tanks and mission payload would help..but this will screw up the direct views (I guess you could put a bunch of TV cameras on the outside though...)



Why not just have a smaller  "area of refuge" amongst the tanks that the astros could go into when radiation is detected?  



Offline Jorge

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Re: Strange story on Mars missions
« Reply #30 on: 04/04/2008 02:20 pm »
Quote
grakenverb - 4/4/2008  9:08 AM

Quote
TyMoore - 4/4/2008  9:04 AM

Also, nestling the pressurized crew compartments in among the propellant tanks and mission payload would help..but this will screw up the direct views (I guess you could put a bunch of TV cameras on the outside though...)

Why not just have a smaller  "area of refuge" amongst the tanks that the astros could go into when radiation is detected?  

Nothing wrong with that concept; it's typically called a "storm shelter". Trouble is, it only protects the crew from solar flares, which are episodic and allow some warning time. It does nothing to protect the crew from cosmic rays, which are fairly constant and difficult to shield against.
JRF

Offline HarryM

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Re: Strange story on Mars missions
« Reply #31 on: 04/04/2008 04:43 pm »
Seems only "shield" against Cosmic Rays is to get to and from Mars as fast as possible, via nuke propulsion of some type. Once on the surface you have 1/2 the exposure via protection of planet's bulk. Even more protection if you find a nice deep crater to have your hab, and/or bury it.

At least Cosmic Rays are fairly constant though, no rude spikes like with Solar radiation. Unless a supernova goes off somewhere nearby, which is unlikely.

Ever watch one of those cloud tanks with the rays zipping through it? They have one at the Exploratorium in SF. Fascinating.

Offline Blackstar

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Re: Strange story on Mars missions
« Reply #32 on: 04/04/2008 06:04 pm »
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HarryM - 4/4/2008  11:43 AM

Seems only "shield" against Cosmic Rays is to get to and from Mars as fast as possible, via nuke propulsion of some type. Once on the surface you have 1/2 the exposure via protection of planet's bulk. Even more protection if you find a nice deep crater to have your hab, and/or bury it.

At least Cosmic Rays are fairly constant though, no rude spikes like with Solar radiation. Unless a supernova goes off somewhere nearby, which is unlikely.

Yeah, the GCR issue is a thorny one.  One of the problems is that if you apply a certain amount of shielding, you create a problem of secondary radiation (particles slam into the shielding and spall off other particles that can hurt you in different ways).  So there's a gap in protection--a certain amount of shielding is good, but then it stops being good until you increase it substantially.

So you're right--the best protection is to run fast to the planet, then hide.  Oh, one interesting factoid that I picked up about this is that it turns out that most of our radiation protection on Earth is the mass of the atmosphere, _not_ the Earth's magnetic field.  We have a big thick column of air above our heads keeping us safe.

As for the lack of spikes, there's one somewhat scary aspect to GCR: the geological record indicates that we may be in a period of low GCR intensity.  It is possible that the GCR could increase substantially in a relatively small amount of geological time (few 100K years).

Offline HarryM

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Re: Strange story on Mars missions
« Reply #33 on: 04/04/2008 06:24 pm »
Yes, I seem to recall reading something along those lines regarding CGR's being higher at different times. It stands to reason that as the Sun goes around the galactic core it is going to get into areas that have more activity. Space is generally pretty "lumpy" so that must apply to radiation as well.

One nice place to hide at Mars could actually be on Phobos. If you could find a large crater facing Mars you would get good protection from GCR's from Phobos bulk behind you and since you are tidally locked, then your front would be somewhat protected by Mars itself since Phobos is so close to Mars, assuming you want to do teleoperation stuff. On Mars, Hellas basin is theoretically nice from radiation standpoint as it is the lowest area, just a focal point for dust-storms unfortunately. Of course we still need to do a lot of work to understand the radiation environment on Mars.

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Re: Strange story on Mars missions
« Reply #34 on: 04/04/2008 06:30 pm »
Quote
Blackstar - 4/4/2008  7:01 AM  
Quote
nobodyofconsequence - 4/4/2008  2:39 AM  

Quote
Blackstar - 3/4/2008  9:24 PM  Ooookaaaayyyy....  Meanwhile, those of us who live on planet Earth have lost you...

Yeah, me too. I listened and didn't quite believe it either. Just what I heard between one group trying to get funded, and who they were introduced to ...  

 You misunderstand.  I consider what you wrote to make no sense at all.

OK. As an alternative to traditional shielding, the idea is to deal with the problem by an alernative means. In this case, the specific research alluded to was to repair the damage due to ionizing radiation, specifically the damage to proteins. This was the form of "high risk" mentioned.
 

If you're interested, there's also research on materials to similarly recover structural materials from radiation embrittlement using nanomaterials. Even work on semiconductors as well.

What was weird about it was that some in the admin looked at this through the lens of use on earth with radioactive materials.

Does that connect the dots for you yet? Should I use smaller words? 

 


Offline Takalok

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Re: Strange story on Mars missions
« Reply #35 on: 04/05/2008 11:33 am »
I remember reading discussions of Mars missions I think as long ago as the 1980's, where these same radiation problems were being grappled with.  It was my understanding then, as now, that there is a certain probability of crew injury or loss from micro-meteoroids and /or radiation.  I don't suppose anyone has ever seen a statistical estimate of these events, and how that might compare to current risk assessments for flight activities like the shuttle (which by the "coin-flip" method is about 1 in 60 for LOC).

Also, back in the sixties when it was assumed we would naturally progress from Moon to Mars, they were looking at Saturn configurations that could lift about 1 MILLION pounds per shot to LEO.  That indicates to me they were also considering some very substantial ships, but I am unaware of any realistic studies for a Mars mission from that era.  Is anyone aware of any proposed mission profiles from that era?

Also, just to be obstreperous, I wonder what the probability for LOC was on one of these?
Life is what happens while you're waiting for tomorrow.

Offline Blackstar

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Re: Strange story on Mars missions
« Reply #36 on: 04/05/2008 01:43 pm »
Quote
nobodyofconsequence - 4/4/2008  1:30 PM
Does that connect the dots for you yet? Should I use smaller words?

Please do.  I'm stupid and don't work in the field or anything.

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Re: Strange story on Mars missions
« Reply #37 on: 04/06/2008 12:31 am »

Quote
Blackstar - 5/4/2008  8:43 AM  
Quote
nobodyofconsequence - 4/4/2008  1:30 PM Does that connect the dots for you yet? Should I use smaller words?
 Please do.  I'm stupid and don't work in the field or anything.

Good for you :)  I am happy for your unique grasp.


Offline Mogster

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Re: Strange story on Mars missions
« Reply #38 on: 04/07/2008 11:30 am »
No one seems to know accurately how dangerous radiation exposure at different levels is to humans, I suppose its a difficult thing to quantify.

If sending crews to Mars has to involve 0% additional risk (whatever that really means) then we'll never go. What would be acceptable? a 1% increased cancer risk after the mission, 5%, 10% .......

Offline William Barton

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Re: Strange story on Mars missions
« Reply #39 on: 04/07/2008 11:53 am »
For things like increased cancer risk, the solution is to use crew who are old enough the increased risk falls inside the mortality rate for other causes. For example, for Mars sortie mission durations under 5yr, it would not be impossible to find crew members aged 60+ who were nonetheless sufficiently fit to handle the rigors of the mission. By the time they were statistically at risk for cancer, they would likely be dead from some other cause. The real danger that has to be looked at is protecting the crew from near term neurological damage from cosmic rays, which would place the mission at risk, and from rapid death due to a solar event, which would count as a LOC event.

Offline Mogster

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Re: Strange story on Mars missions
« Reply #40 on: 04/07/2008 01:00 pm »
I just see the low level radiation issue as another excuse not to go. Have any of the Apollo crews shown neurological damage from cosmic rays? I've not heard of health problems from the ISS or Mir crews? I know its less of a problem in LEO but if the effects were so bad surely they'd have shown up to a degree by now.

For high level solar flare protection a small safe haven in the spacecraft would seem the obvious solution. It'd be uncomfortable for a time but then how comfy are days at a time jammed in a Soyuz.

It amazes me the Pathfinder, and the MER's flew without dedicated radiation measurement instruments.


Offline Blackstar

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Re: Strange story on Mars missions
« Reply #41 on: 04/07/2008 01:47 pm »
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Mogster - 7/4/2008  6:30 AM

No one seems to know accurately how dangerous radiation exposure at different levels is to humans, I suppose its a difficult thing to quantify.

If sending crews to Mars has to involve 0% additional risk (whatever that really means) then we'll never go. What would be acceptable? a 1% increased cancer risk after the mission, 5%, 10% .......

You can read up on this stuff and get the answer.  Here's a good basic text: http://www.nap.edu/catalog.php?record_id=11760

(I served as study director on that report)

Quick answer is that the baseline is to compare the risk to that experienced by workers in commercial nuclear power plants.  So astronauts are allowed to have a greater cancer risk than the general population.

Now you can ask if the risk allowance should be greater, but right now, NASA has set a baseline that they don't want to exceed.

Offline Blackstar

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Re: Strange story on Mars missions
« Reply #42 on: 04/07/2008 01:51 pm »
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William Barton - 7/4/2008  6:53 AM

For things like increased cancer risk, the solution is to use crew who are old enough the increased risk falls inside the mortality rate for other causes. For example, for Mars sortie mission durations under 5yr, it would not be impossible to find crew members aged 60+ who were nonetheless sufficiently fit to handle the rigors of the mission. By the time they were statistically at risk for cancer, they would likely be dead from some other cause. The real danger that has to be looked at is protecting the crew from near term neurological damage from cosmic rays, which would place the mission at risk, and from rapid death due to a solar event, which would count as a LOC event.

That's not really a solution.

1-it's cheating; you have not decreased the risk, simply played with the statistics (and there are even more controversial ways to cheat: just ban all women and Asians from the missions, because they are at higher cancer risk)

2-your available pool of candidates is going to be much lower (how many 60-year old astronauts do we currently have available?)

3-there are other risks that are likely to be greater for the 60+ population, such as bone density loss.  Whereas you can accept a certain amount of bone density loss in a 40-year-old male, the same amount might be truly dangerous for a 61-year-old male.

And just to make something clear here--the issue is not simply _personal_ risk to individuals who are allowed to make their own decisions, the issue is also _mission_ risk.  If somebody dies during the mission, or becomes seriously incapacitated or sick, then it can jeopardize the entire mission and indeed the entire crew.  Put it this way: what if the crewmember who breaks his arm is your only doctor?

Offline Blackstar

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Re: Strange story on Mars missions
« Reply #43 on: 04/07/2008 02:01 pm »
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Mogster - 7/4/2008  8:00 AM
I just see the low level radiation issue as another excuse not to go.

You and Bob Zubrin.  Other people, like those with medical disagrees, don't see it that way.


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Mogster - 7/4/2008  8:00 AM
Have any of the Apollo crews shown neurological damage from cosmic rays? I've not heard of health problems from the ISS or Mir crews? I know its less of a problem in LEO but if the effects were so bad surely they'd have shown up to a degree by now.

Not a good comparison.  Astronauts who went to the Moon were only in space for about a week.  Astronauts in LEO have some protection from the Earth's magnetic field.  And some astronauts have been grounded because they reached the allowable radiation dosage.  Mars is a much longer mission.

As for anybody showing any damage?  Although the medical records are kept private, there is evidence of astronauts suffering long term health damage as a result of their flights.


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Mogster - 7/4/2008  8:00 AM
It amazes me the Pathfinder, and the MER's flew without dedicated radiation measurement instruments.

It's not a science objective.  A rover has only a limited mass budget for instruments, so the ones that go on the rovers are the ones that are highest priority.  Because the science objective has been to follow the water on Mars, the instruments reflect that.

Several years ago there was a proposed NASA program for sending some human precursor missions to Mars to gather key data that would be useful for future human spaceflight.  You can read about the recommended data to be collected here:

http://www.nap.edu/openbook.php?isbn=0309084261

It's interesting to note that there are a lot of things to be concerned with.  One that space advocates don't think about is pretty basic: is Mars dust toxic?  If you breathe it in your lungs, will it harm you?  If you think about it, walking around in a room filled with asbestos without respiratory protection is a bad idea, so it's worth asking if the Mars dust that astronauts will inevitably breathe in once they take off their dirty spacesuits will cause any harm.

Offline Norm Hartnett

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Re: Strange story on Mars missions
« Reply #44 on: 04/08/2008 07:07 pm »
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HarryM - 4/4/2008  9:43 AM
Ever watch one of those cloud tanks with the rays zipping through it? They have one at the Exploratorium in SF. Fascinating.

Astronauts in both LEO and the Apollo missions have reported seeing the same effect.

In their own eyeball fluid!

This is at least as serious as bone loss and less tractable to low mass solutions.

“You can’t take a traditional approach and expect anything but the traditional results, which has been broken budgets and not fielding any flight hardware.” Mike Gold - Apollo, STS, CxP; those that don't learn from history are condemned to repeat it: SLS.

Offline HarryM

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Re: Strange story on Mars missions
« Reply #45 on: 04/08/2008 08:35 pm »
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Blackstar - 7/4/2008  7:01 AM
It's interesting to note that there are a lot of things to be concerned with.  One that space advocates don't think about is pretty basic: is Mars dust toxic?  If you breathe it in your lungs, will it harm you?  If you think about it, walking around in a room filled with asbestos without respiratory protection is a bad idea, so it's worth asking if the Mars dust that astronauts will inevitably breathe in once they take off their dirty spacesuits will cause any harm.

I guess that's what happened to Viking's experiment when they added moisture/nutrient (assuming it was not biological reaction which seems unlikely anyways), some sort of peroxide in the soil, except the reaction would be happening in the astronauts lungs.  Maybe MSL can do more work on this, nature of dusts or oxidants in the soil?

I think for the length of time they are going to be there they are going to have to be extremely rigorous in controlling dust entry into the habitats and other structures where they will be breathing  the air. Not just to negate the bad health effects but for equipment. I think something akin to a cheap paper painter's suit might be good here, that they could dispose of before entering the airlock.

Offline Blackstar

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Re: Strange story on Mars missions
« Reply #46 on: 04/08/2008 09:34 pm »
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HarryM - 8/4/2008  3:35 PM
I guess that's what happened to Viking's experiment when they added moisture/nutrient (assuming it was not biological reaction which seems unlikely anyways), some sort of peroxide in the soil, except the reaction would be happening in the astronauts lungs.  Maybe MSL can do more work on this, nature of dusts or oxidants in the soil?

Dunno the specifics.  A few years ago Leonard David writing for Space.com had an interesting article with the subject "What does Mars smell like?"

There are actually some really tough contamination issues for the science side.  It's a difficult task to keep the dust from getting into the atmosphere of the spacecraft and into the lungs of the astronauts.  But here's the real kicker--how do you keep human contamination from getting out onto Mars and therefore into your samples?  If the goal is to look for signs of life, you want to keep humans from bringing bacteria out onto the surface, scooping it up, and then "finding" it on Mars.

Personally, I think that's impossible.  Once you put people there, you will inevitably contaminate the place and make it very difficult if not impossible to detect microbial life.

Offline HarryM

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Re: Strange story on Mars missions
« Reply #47 on: 04/08/2008 09:39 pm »
I agree, makes doing adequate science via robotic landers or sample return essential.

Offline TyMoore

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Re: Strange story on Mars missions
« Reply #48 on: 04/08/2008 09:45 pm »
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Garrett - 4/4/2008  6:52 AM

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TyMoore - 2/4/2008  7:49 PM

I think this illustrates not only the need for more research--but also a different philosophy regarding mission architectures: either we need to think of sending larger vessels that are better shielded to protect crews, or we need to send the crew on a faster vessel so that the total radiation 'integration time' will be less.

Hmmm, I'm not an expert but I don't think it's really possible to send a faster vessel if we want to use a Hohmann transfer orbit to Mars, which is the only transfer orbit that we seem capable of performing with today's technology.

If you accept a less 'energy efficient' trajectory and go with a non-Hohmann transfer, then you can use a much faster hyperbolic trajectory--you can in effect 'cut the corner' and go directly from Earth-Solar orbit to Mars-Solar orbit--with propulsive menuvers at both ends you could even do it in less than 30 days (that is really hustling though!) Of course, this entails a "lot" of delta-V--dozens of kilometers per second. This kind of menuver might not even be possible with nuclear thermal propulsion yet--the mission delta-V requirements would likely be that high...however, it could be a way of menuvering habitats and supplies into position first, and then following that up with a 'fast crew' transfer to reduce crew integrated radiation exposure.

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