How Safe Is Travel To Mars

[halman]

gunsandrockets,<br /><br />Because all of our experience with protection against radiation and particle bombardment has been with heavy materials and/or substanitial thicknesses of materials, we have an inate bias when thinking about doing the same thing in space. But there is more than one way to skin a cat, as someone once said, and you can bet your bottom dollar that some wacky idea will turn out to be the solution.<br /><br />For instance, a thin outer skin containing a sandwich of conducting materials surrounded by an excitable gas, with a thin inner wall. The conducting materials are charged to produce a magnetic field in the gas, which is allowed to dissapate its charge into an array of radiators away from the vehicle. Instead of trying to create a magnetic field large enough to encompass the entire vehicle, a magnetic 'bottle' is created, with a means of dumping intercepted energy (particles derive their energy from velocitiy as well as charge, I believe,) into some kind of 'sink'. Perhaps two magnetic fields with opposing charges in seperate gas chambers.<br /><br />Heck, maybe we should be trying to figure out how to absorb and convert this energy into something that we can use, instead of building powerplants to protect us from energy.<br /><br />Until we can experiment in the actual environment we need to survive in, it is unlikely that we can develop a workable solution to this problem. Certainly, we know that using heavy sheilding, or large amounts of water will work, but these may impose severe penalties on our limited propulsion systems. It is too bad that we cannot delay going to Mars long enough to develop nuclear propulsion systems, but it obviously imperative that we get there as soon as possible. (At least, that is the impression that I get.) <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[cuddlyrocket]

"My understanding is that the effectiveness is generally proportional to the density of Hydrogen atoms in the material. It's weird & I would dearly like to have a deeper understanding, but apparently an inch thickness of water is a better shield than an inch of lead!"<br /><br />The reason is that heavier nucleii will be shattered by high energy cosmic rays etc, the fragments of which themselves comprise particulate radiation that you need to shield against. Most of the thickness of heavy element radiation shielding protects against these daughter particles.<br /><br />A hydrogen nucleus, being a single proton, cannot be shattered.

 

[spacester]

<img src="/images/icons/cool.gif" /><br /><br />Thank you; another excellent, easy to remember explanation, I love it! <div class="Discussion_UserSignature"> </div>

 

[bdewoody]

Hey, I'm not the one giving someone NASA research monies the study the possibility. I read about it on Space.com last week It mentioned that Artthur C. Clarke used the idea in one of his stories. I'm just wondering how many asteroids or comets would make viable hosts for this type of sheilding? <div class="Discussion_UserSignature"> <em><font size="2">Bob DeWoody</font></em> </div>

 

[JonClarke]

<i>I read about it on Space.com last week It mentioned that Arthur C. Clarke used the idea in one of his stories.</i><br /><br />I have read probably every story that ACC ever wrote and he did not say this. In fact, in his popular book on space flight - "The Promise of space" (a seminal book in my life) he heaped scorn on the idea.<br /><br />Clarke did, howver illustrate the possibility in the story "Summertime on Icarus" on using an asteroid as broad spectrum radiation shield for a manned solar flyby. But that is, as Kipling would have said, another story.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[scottb50]

It's weird & I would dearly like to have a deeper understanding, but apparently an inch thickness of water is a better shield than an inch of lead!">>><br /><br />That has been my thinking on the matter, if we are going to have people in Space we are going to need a lot of water just for their use. If we use the water to produce electrical power and recycle it we not only purify the waste generated by people we reuse the same water over and over again, reducing the mass of expendable fuel we would need for any other power generating system.<br /><br />If we also use the water to produce propellant we can reduce the mass we need to carry as well as simplify the storage and handling problems. As an example if we take a reactor to produce electrical power and chemically fueled rocket motors for propullsion we need a fairly mass intensive reactor plus the fuel for it over it's design life, storage for kerosene, or whatever fuel you want and large scale cryogenics to carry enough Oxygen for say a Mars round trip.<br /><br />Using water you produce Hydrogen and Oxygen as needed to provide electrical power using Solar Power and LH2 and LOX in limited quantities as needed, greatly reducing storage requirements. The other consideration is you would need water treatment anyway to provide for people, simply dumping waste would require a lot more water than recycling. Combine that with a separate electrical system and separate propulsion system and it doesn't make sense. <div class="Discussion_UserSignature"> </div>

 

[bdewoody]

That's where they got the idea to use one as a radiation shield to go to Mars. <div class="Discussion_UserSignature"> <em><font size="2">Bob DeWoody</font></em> </div>

 

[thalion]

I think the simplest solution to the radiation problem is to invest in better propulsion. If we're going to spend billions to get to Mars, why not spend extra to do it better and get it right? In for a penny, in for a pound.<br /><br />If say, nuclear thermal propulsion could halve the flight time to and from Mars, we could limit radiation exposure *and* musculoskeletal degeneration at a stroke.

 

[JonClarke]

What people seem to be forgetting is that the point value exposures for a 1000 days round trip are already inside the exposure limits. What takes them outside is the recent insistence that the 95% confidence intervals must fall inside the limits. More research will tighten those limits and bring them back in side. It is worth noting that quite a few people have already exceeded the levels that Rapp sets without ill effects.<br /><br />I find this whole hoo hah annoying to some extent as it is shifting the goal posts and also to some extent scare mongering as improved data will almost certainly bring the confidence limits inside the accepted range. It also annoying because seems to point to two desires prevalent in some: as desire to find new excuses for not go to Mars as old ones as shown to be invalid and to ensure continued research funding in a pet area in perpetuity, rather than to solve the specific problem of getting to Mars.<br /><br />Since the aim is to narrow the confidence limits then that is what should be done. Its going to cost far less in time and money to do this than to develop high risk new propulsion systems. This is what is being done already, a major focus of biomedical research on the ISS is radiation exposure effects.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[mithridates]

Since we're most definitely not ready to travel to Mars yet, why not keep things done by robot probes and spend the money to develop new propulsion systems? Not only does it decrease the risk of radiation but there's a definite psychological aspect to it as well. Six months in a ship while moving further away from Earth than anybody has ever done is certainly nothing to take lightly. Anybody going to Mars will become the first humans to only be able to see the Earth as a tiny blue star and nothing else. The more time it takes to travel to a location the more likely it is that something could go wrong a la the fire on Mir, for example. I don't want to see the whole program get shot down and lose public support because we weren't prepared.<br /><br />Since people are attracted not just to humans but things that look human as well, I think we should start sending robotic probes to Mars that actually look somewhat like us. <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[gunsandrockets]

"...and spend the money to develop new propulsion systems? Not only does it decrease the risk of radiation but there's a definite psychological aspect to it as well. Six months in a ship while moving further away from Earth than anybody has ever done is certainly nothing to take lightly. Anybody going to Mars will become the first humans to only be able to see the Earth as a tiny blue star and nothing else. The more time it takes to travel to a location the more likely it is that something could go wrong..."<br /><br />Unless you are talking about a relatively exotic propulsion system such as a particle-beam driven electromagnetic-sail or Orion Nuclear Pulse Drive, you can forget about quick trip times to Mars and back. The major benefit of a more realistic new propulsion system such as a Nuclear Thermal Rocket is reduced mission costs (or increased mission payloads).

 

[vulture2]

>>an inch thickness of water is a better shield than an inch of lead!<br /><br />Hydrogen is more effective, but not that much more. I think you mean that a ton of water is more effective than a ton of lead. However this is not necessarily true for shielding against heavy nucleii in cosmic rays.<br /><br />I still tend to feel a large superconducting magnet producing a field that extends one or more kilometers outward from the spacecaft is the most weight efficient solution, the only one that is equally effective against heavy nucleii, and perhaps most important, the only one that will permit an unobstructed view of the stars..

 

[qso1]

bdewoody:<br />It mentioned that Artthur C. Clarke used the idea in one of his stories. I'm just wondering how many asteroids or comets would make viable hosts for this type of sheilding?<br /><br />Me:<br />If I understood what you said in your original post...it appeared you were saying that the ship would travel alongside a comet or asteroid that would be between it and the sun. My answer was that this would be an extremely rare circumstance which at best, might work for a short while but because of trajectory differences of comets, asteroids, and typical Hohmann transfer orbits to and from mars. The likelihood of matching velocity and trajectory with a passing comet or asteroid as a way of shielding oneself on the way to mars is exceedingly small. For part of the outbound or inbound leg it may be possible, but one of those legs will result in unshielded travel as the comet or asteroid will not be coming back to earth or leaving and vice versa according to the spacecraft trajectory.<br /><br />bdewoody:<br />I'm just wondering how many asteroids or comets would make viable hosts for this type of sheilding?<br /><br />Me:<br />If you find a comet or asteroid of sufficient mass, any of the correct minimal mass would be viable. That mass would be determined by how far the comet or asteroid would be from the craft. This sounds more like an application for actually relocating an asteroid, fitting it with propulsion systems and letting it travel alongside the ship...but then, if you go through that trouble...may as well outfit the asteroid as the spacecraft. Propulsion and life support. I'd be willing to bet even a small (100 m diameter) asteroid hollowed out would be more than enough protection but very expensive to implement. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[ebort]

perhaps what we really need to do is find a definitive innoculation and cure for cancer??<br /><br />seems cancer is to space flight what "scurvy" was to the sail ship crews during early exploration of the world's oceans..perhaps if the British Empire hadn't collapsed (and i'm only having a laugh here..trust me)<br />we would have ports on the moon and mars by now most crew having being press ganged into the Royal "Navy" and flogged at the first sign of disgruntlement ..dangerous journeys of extreme length being the norm (not the exception) in those days<br /><br />pip pip what???<br /><br />only kidding but there is a comparison there with the dangers of early sailship navigation?

 

[cuddlyrocket]

"perhaps what we really need to do is find a definitive innoculation and cure for cancer??"<br /><br />Lateral thinking! Yes, if we could easily cure cancer, then the radiation becomes much less of a problem (the level of radiation would not have to be so severe that it would kill before any cure could be applied).<br /><br />Reminds me of a Larry Niven science-ficition short story in his 'Known Space' future history series. The protagonist smoked - because any cancer would be easily curable, so why not? (This ignores heart diseases etc caused by smoking, but the principle is valid. We object to smoking because of its adverse health effects. If those were easily rectified, what is the objection to smoking?)

 

[lampblack]

<font color="yellow">We object to smoking because of its adverse health effects. </font><br /><br />Well, yeah... that, and it stinks.<br /><br />But your main point is well taken! <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <font color="#0000ff"><strong>Just tell the truth and let the chips fall...</strong></font> </div>

 

[ebort]

if we can reduce the likelyhood of the crew getting cancer even slightly by drug treatments/innoculation.. (that do not incapcitate them at the same time)..<br />then using radiation sheilding on the crew sleeping compartment only would further reduce the risk ..(the crew will spend a significant amount of time asleep or resting) then things are getting a little more managable,<br />dunno about the trip to the surface and back being the major danger moment...(without a shielded lander??)<br /><br />perhaps we should take it stages...establish a space station around mars...(and the moon for that matter)<br />and get some serious practice in sending supplies by un-manned probes...maybe even setting up heavily shielded staging posts at the halfway distance to allow for crew rotation...emergency fall backs etc..<br />course the problem is getting all this gear into space in the first place...

 

[kdavis007]

I have a feeling that the anti human in space crowd are trying to grasp at straws with every excuse they can think of....

 

[MeteorWayne]

I don't think so. There are very real and serious risks involved in travel outside of the earth's magnetosphere.<br />Increased cancer risk, possible brain damage, etc.<br />those who choose to travel will be aware of the risk, and whatever can be done by then to decrease that risk.<br />But the damage from radiation is real. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[vulture2]

>>What people seem to be forgetting is that the point value exposures for a 1000 days round trip are already inside the exposure limits. What takes them outside is the recent insistence that the 95% confidence intervals must fall inside the limits.<br /><br />I completely agree that no developments in shielding are needed for the initial manned flights to and from Mars, and said so at the first Case for Mars conference in 1981. I also agree that the current NASA approach to radiation exposure limits seems confused. NASA defines an arbitrary risk, then defines a second risk that the 'actual' risk is above this limit, as though crossing the line would result in a crewman getting cancer.<br /><br />This misinterprets the concept of risk. There is no threshold dose of radiation that is safe; the first day in space carries about the same risk of inducing cancer as the last. You might just as well say that if the risk of a being struck by lightning is 1% per year, after ten years you will be fired because your risk has now reached the 10% limit. That's why NRC radiation exposure standards are based on exposure per year worked rather than imposing a lifetime dose limit for each employee; the purpose of the standard is to keep the workplace as safe as possible, not to limit the total risk an employee may decide to accept over his career. This also explains why NASA is the only employer in the world that counts medical exposures against an employee's occupational limit. Since the medical exposure is a voluntarily accepted risk that has no bearing on workplace safety, it is inappropriate to consider it. <br /><br />However for people to work productively in space, they will soon need to spend longer periods there, whether it is a few years on Phobos or a trip to the asteroids, or even a career on the Moon. HZE particles in GCR kill neurons in the brain, an effect that is slow but certain; you wouldn't want you pilot to be missing to many brain cells. As missions get longer,

 

[qso1]

Ebort:<br />perhaps what we really need to do is find a definitive innoculation and cure for cancer??<br /><br />Me:<br />Good analogy of cancer being to spaceflight what scurvy was to sailing ship crews. Sometimes its analogies like those that put a current problem into better perspective. For now however, a single shot cure for cancer seems further off than it was when America expected a cure by the year 2000. But it sometimes takes a problem like this to focus the research effort more. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[halman]

kdavis007,<br /><br />Well, I have the feeling that there are many people who want to go to Mars so badly that they are willing to forsake practically anything to get there. What this discussion is about regards travel in a realm that no human being has spent more than a few days in, on journeys that will take years. There is currently no projected test flights of long duration, which means that we are considering launching a mission without performing the gradual working up to a level of accepted safety. By this, I mean we are are not (at this time) talking about doing the equivalant of taxing an aircraft faster and faster until it is at take off speeds, to test control surfaces, buffeting, and such, or running a motor under progressively heavier loads.<br /><br />In the Apollo program, there were 4 flights before the actual Moon landing, as every part of the mission was rehearsed carefully. When it comes to going to Mars, folks just want to jump in a ship and take off. If the destination were somewhere different, I suspect that it would be very hard to find any volunteers to make a 3 year test flight. Over the last few years, I have noticed a tendancy on the part of Mars advocates to dismiss out of hand any objections to their goal of the immediate mounting of manned missions. They seem to have developed a 'faith' about going to Mars, which overcomes considerations that these same people would have for travel to a different destination than Mars. Many people also seem interested in space travel for no other purpose than of going to Mars.<br /><br />Oh, well, if people want to be guinea pigs for radiation exposure studies, that is fine by me. I just would rather not see our space program threatened because of a disaster involving people going to Mars. There are a lot of reasons for going into space, and to sacrifice them because of excessive haste in mounting a manned Mars mission would be idiotic. But a major failure of a Mars mission could do great harm to <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[qso1]

halman:<br />What this discussion is about regards travel in a realm that no human being has spent more than a few days in, on journeys that will take years.<br /><br />Me:<br />Development of a VASIMR based or similar propulsion system would cut enroute travel times to three or four months in theory. Radiation shielding on mars habs should be able to handle radiation problems for surface crews. Especially if habs can be covered with soil.<br /><br />halman:<br />Over the last few years, I have noticed a tendancy on the part of Mars advocates to dismiss out of hand any objections to their goal of the immediate mounting of manned missions.<br /><br />Me:<br />I wouldn't be one of them. I do advocate a human mars mission myself. But a reasonably safe one. This latest information may lead to safer ways to mount a well planned human mars mission. Or it could lead to the demise of the whole idea. In actuality it will probably do a little of both. Truth is, we need more research into this and a few other areas to determine the best approach to a human mars mission.<br /><br />halman:<br />Many people also seem interested in space travel for no other purpose than of going to Mars.<br /><br />Me:<br />This probably stems from the dismal record of human space exploration progress to or beyond the moon after Apollo. If we have this much trouble justifying a human mars mission, how would we be able to justify a mission anywhere else? And if the study is a reason to squelch plans for a mars mission. Forget going anywhere beyond LEO or the moon.<br /><br />halman:<br />I just would rather not see our space program threatened because of a disaster involving people going to Mars.<br /><br />Me:<br />Even the safest possible or practical missions are not immune to disaster. The problem with assuming a disaster will occur in connection with radiation is that we may see a disaster we are totally unprepared for and having nothing to do with radiation.<br /><br />halman:<br />But a major failure of a Mars miss <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[halman]

qso1,<br /><br />Because I have read numerous post by people who believe that it is waste of time and resources going to the Moon when we should be going to Mars, I have made statements regarding a mission to Mars occuring within the next 20-50 years. That seems like a long time to young people who weren't born when the shuttle first flew, but to someone who watched the first lunar landing, it is not really that long. At the rate that current propulsion technology is developing, I can not imagine a significant new engine being created in that time.<br /><br />Nearly all of the media pieces I have seen regarding manned space exploration for the last 20 years or so have been focused on a Mars mission, which indicates to me a lack of understanding of the space program. We are going into space not just to be able to travel to other worlds, but to learn to utilize off planet resources, to establish industries off planet, and to develop the ability to survive anywhere in the Solar System, whether on a planet's surface or not. Mars has historically been a planet believed to harbor life, and so many people assume that life there will be easier than on the Moon, or in orbit. Perhaps it may be, but only time will tell, and right now, it will take a lot of time to get to Mars.<br /><br />Because we lack experience in long-term life support technology that is totally self contained, radiation poisioning is only one catastrophe which could befall a manned mission to the Red Planet. Certainly, a Mars mission could take all the food and water and oxygen that they will need for the entire duration of the voyage, so completely recycling everything is not required, but a breathable atmosphere has to be maintained, and this involves processing the air to remove carbon dioxide, moisture, and dust. We have never run an airplant for years at a time, so we don't know what might crop up, just as Legionairre's Disease did in HVAC systems we thought that we thoroughly understood. This is m <div class="Discussion_UserSignature"> The secret to peace of mind is a short attention span. </div>

 

[qso1]

You raise valid points and although I advocate a safe mars mission. Don't be in too big a hurry. I think it could be done within the next 25 years but there historically always has to be some driving reason to actually get us there. So all the folks in America who want a mars mission cannot make it happen without majority public support.<br /><br />IMO, public support for a mars mission simply isn't there as long as large numbers of people continue to believe Apollo was a waste of money. Mars will remain beyond us. Apollo was as much or more the result of a cold war contest as it was science and a desire to extend humanities reach. Post Apollo is a kind of been there done that...man can fly, land on the moon frame of mind. The only way I can see mars actually occuring within 25-35 years is if we discover microbiological life or private industry/enterprise revolutionizes access to low orbit and then finds a profitable reason to go to mars.<br /><br />Therefore, there seems to be an almost naturally occuring course of events that virtually guarantees your scenario of developing near earth space and you are also right in that once we have an infrastructure in place. An accident on a mars mission would be far less likely to shut the mars program down. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>