Wednesday, May 24, 2006

Why Slam?

Dan Schrimpsher asked a perfectly reasonable question after I recently slammed a blogger for pooh-poohing the radiation hazards of manned space flight to Mars, although I believe he over-reacted. Dan wonders why I would slam a blogger for his opinion if he isn't asking for money.

There are 2 reasons:

First, anyone is entitled to his or her opinions whether supported by fact, fantasy, or floating in Kool-Aid. Unfortunately, many of the opinions floating in the blogosphere are not supported by fact, but by speculation or ignorance. When such speculation or ignorant opining is repeated sufficiently, it starts assuming the aura of fact with other people who do not have the time to examine primary sources in detail or the knowledge base to discriminate. That eventually leads to Lysenkoism, people who believe that the Earth is the center of the universe, and (my personal favorite) people who believe that the USA never put men on the Moon. Therefore, errors of fact and of interpretation need to be identified and exposed. That is one goal of The Space Cynic. Unfortunately, taking down the blog in question about space-flight radiation biohazards in detail, with references to well-documented sources, would take far more time and space than I am willing to consume with a point by point rebuttal that would be understood by an average, but interested, reader. Instead, the interested person should reread the critical blog, then reread the Scientific American article carefully, and then do whatever research he or she needs to conduct within the primary literature in order for form a conclusion what would stand up to careful review. I do believe that the blogger in question, while sincere, grossly oversimplifies the ability of our current technology and knowledge base to deal with the radiation hazards of transporting people to Mars. That seems to be a common occurrence with space flight enthusiasts coming from the physical sciences when considering biomedical risks. It is easy to postulate surrounding a crew cabin with fuel for shielding. What happens when the fuel is consumed for the return trip? In the abstract, you may be willing to take on an additional risk of 50% of dying from a radiation-induced cancer in exchange for a trip to Mars, but would the NRC permit you to assume that risk? Are you willing to damage your future children for the ride? Quit dismissing the problem out of hand and consider the ramifications of high dose radiation exposure -- especially since dose levels have not been precisely defined.

Second, with one exception, I do not care what people do with their own money. They are perfectly free to earn it and spend it as they wish. (I do -- I am currently invested in three start-ups and had been but no longer am invested in another.) They can even burn it in their front yards for all I care. Elon Musk is a case in point. He is spending his own money to pursue his goals. Good luck to him. I do care when people start asking for other people's money to do great things rather than using their own. That comes about when apparently sincere people say they can give the human race cheap access to space for (insert your number here) dollars, but their proposals do not stand up to careful examination. We are not likely to be taking tourists to Mars or Venus within a decade or two with Apollo-era technology. That is especially true with a company that has yet to get anything into even suborbital space. That some people are ignorant enough to "buy a ticket" is a sad commentary on them, but the people accepting the money for that purpose are, in my opinion, skirting fraud at worst and exploiting ignorance and dreams at best. They are dispensing Kool-Aid. What is the exception I mentioned above? Using one's own money to deliberately misinform the public.


Blogger Dan Schrimpsher said...

My response is at Response

BTW lots of good posts lately. Keep it up guys.

Wednesday, May 24, 2006 8:25:00 PM  
Blogger Clark said...

Doggone it. I knew I should have removed this blog from my RSS aggregator. There is nothing I enjoy less than getting into pointless Internet flame wars (especially with people with whom I probably agree with on 95% of space issues). A blog titled Space Cynic was obviously intended to light and fan as many flames as possible.

I was told about your initial comment on my space rad item but decided to refrain from getting into all that. However, I now feel compelled to defend my honor from the slings and arrows of an outrageous posting.

Gee whiz John, I remember being scolded a couple of times by health physicists for not properly securing a radiation source for the evening but you are really hitting me over the head here. Irrational? fantasist, Lysenkoist? ignorant opiner? Kool-aid drinker? Wife beater? Oh wait. No, you didn't actually include the last one but I still hope my wife doesn't read your posting else she decide to leave such an awful person.

I'll admit I can be irrational about things. I keep working, for example, on a silly website about space (which so far my wife has forgiven me for). On the other hand, you are posting on a blog named Space Cynic and using an alias and making all sorts of accusations and insults against an unnamed blogger, whose name everyone here knows, in regard to a posting everyone here knows about but which you refuse to link to. I'll trust your judgment that such behavior is rational but to me it doesn't seem very civil and certainly seems out of line with normal scientific discourse. But that's just me and I'm irrational after all.

Forgiving my failings for the moment, please suffer the following meager defense of my posting about space radiation.

You say that repeating untruths enough times will eventually convince many people that such fallacies are true. I couldn't agree more. A prime example is when gullible journalists are repeatedly told by some in the health physics and space science fields that there is a real chance that humans will forever be confined to earth because of GCR. That was the extreme claim I was primarily addressing in my posting. That extreme claim is in the titles of both the SciAm and Discover articles.

Perhaps you think it is irrational, but I think it is quite logical to use a valid conceptual counter example to disprove an extreme claim like that.

In the posting I gave a couple of such examples showing that one can, with current or near term technology, provide enough shielding in space to reduce backgrounds from GCR to earth surface levels. If that is the case, then I don't need to be an expert on the effects of radiation on the body to know whether people can survive in space since we seem to do OK on earth with that level of exposure.

Space tourists visiting a Bigelow habitat, for example, probably don't want to become de facto radiation workers. I posit that there is no fundamental physics or technological reason in principle that a space habitat could not be surrounded by water tanks large enough to provide such shielding. The Shuttle ETs, for example, which don't reach orbit but could, are just one example of space qualified tanks of sufficient size to provide such shielding.

We also know that the launching of bulk cargo like water to orbiting depots is a perfectly reasonable concept that has been endorsed even by Mike Griffin.

That doesn't mean that Bigelow will or should actually surround his habitats with big water tanks. I was just providing a valid counter example that disproves the above extreme claim about space radiation. I hold that in a rational world, that sort of example would be the end of that extreme claim and it would no longer be repeated. But, of course, it will be anyway. I have my opinion on why it will be repeated but I won't go into that. You would no doubt find my opinion irrational.

For Mars trips I discussed two cases. The first dealt with using some reasonable counter measures to reduce radiation exposures for the early pioneers to levels significantly below those given in the SciAm article. You mention fuel tanks but I actually refer to water tanks. However, both fuel and water will be needed in both directions so I disagree with your point anyway. (If water needs to be delivered to Mars rather than obtained from in situ sources then I think the whole trip is pointless. Similarly, I take it for granted also that Zubrin's Mars Direct type ideas will be used to extract fuel from the atmosphere for the return trip.)

I'm fully aware that even if the SciAm estimated exposures will be reduced by half, there are many who would still consider that level too large. The effects of such an amount of radiation are obviously something to be studied by experts in that field. I would nevertheless ultimately leave it up to those volunteers willing to go to Mars to decide what risks they are willing to take. But, as you indicate, the decision may not be in their hands.

I said in my posting that NASA should provide plenty of resources to study these problems and to find out how to optimize shielding.

The other Mars spacecraft concept that I mentioned is the cycler, which has been studied by various people and is a favorite of Buzz Aldrin. There is no fundamental reason such a cycler could not have its shielding built up to a thickness sufficient to achieve earth exposure levels. (If you know of such a reason, then please write a paper on it.) So someday transporting large numbers of people to Mars and subjecting them to only minimal radiation dosages along the way is clearly feasible. Again, this example does not violate any physical laws or require extreme unobtainium. The cycler may never actually be used for Mars transport but it is a valid counter example that disproves the extreme claim.

Finally, I'm well aware that my doctorate in physics doesn't qualify me to speak authoritatively on the biological effects of radiation.(With my hoary old brain cells I wouldn't try to speak authoritatively on physics or anything else either.) If I wanted to know, say, what terrible things X number of rads can do to a given organ, you are definitely the sort of person to whom I would refer. However, I still think I'm perfectly able to make a rational and scientifically sound argument in support of the proposition that it is feasible in principle to provide sufficient shielding to allow humans to live, work, and one day settle safely in space. Nothing I've said requires validation from someone with a degree in health physics and neither does it require one to spend the day in the library reading papers on health physics and space radiation. You obviously disagree but to refute my argument it will take more than appeals to authority or implying that I'm being ignorant and irrational for not deferring to such authority.

But whatever! This is, after all, just another pointless Internet flame and they never change anyone's mind on anything.

- Clark S. Lindsey

Thursday, May 25, 2006 10:29:00 AM  
Blogger TomsRants said...

I dunno what all the fuss is about. I'm not an em-dee or a pee-aitch-dee, but I did study physics in college. I don't know if there are long term show-stoppers or not, in terms of GCR, etc, exposure for explorers or colonists. But as long as we keep the dialog going on this topic, I remain confident that human ingenuity will create the necessary workarounds to any perceived impediments.

I mean, if you want to take exception to something, within a kool-aid framework, have a look at this excerpt from a comment to Clark's own post:

"Sure, for a free space facility with large protected volume you need a lot of dirt. So you set up dirt-cheap mass-driver launch from the Moon, or bring in some asteroidal material similarly."

Who's going to pay for the dirt-cheap mass driver? Or bring home the asteroidal material? Oh, I know - $100 a pound access to space - which is right around the corner.

Thursday, May 25, 2006 11:22:00 AM  
Blogger oldspacecadet said...

Consider a 3 meter diameter by 10 meter long habitat -- roughly 71 cubic meters of volume. A cylindrical shell of water 5 meters thick would be more than 1,250 cubic meters, or more than 1.25 million kg of water. If you prefer, that is more than 2.75 million pounds of water. At even $200 per pound to LEO, that is a large freight cost. Is that a show-stopper? Perhaps not, but it is a very real problem unworthy of dismissal by a snap of the fingers.

Instead, consider magnetic shielding. A reasonable field density for such a shield would be roughly an order of magnitude larger than the field in an MRI machine. Do I want to live in such an intense field? No.

This is why the discussion is essentially pointless. The interested reader can go to the primary literature and make up his or her own mind. Also, it wouldn't hurt for the interested reader to look at the current NRC regulations regarding radiation exposure limits for different population groups and consider the NRC's policy of ALARA.

Thursday, May 25, 2006 7:17:00 PM  
Blogger badger said...

The link to Clark's post is here: Poppycock!

Note to all Old Space Cadets: one conclusion in M.G. Lord's Discover cover story "Are We Trapped on Earth?" is that the best candidates for early Moon and Mars expeditions are people who have already done their reproductive duties and have little to lose by playing fast and loose with radiation and cosmic rays. (Old people.)

Thursday, May 25, 2006 9:55:00 PM  
Blogger oldspacecadet said...

Badger, that is correct. One problem is still the NRC. They have stringent rules on allowed exposure rates based on age, sex, and population segment. Even if an old person was willing, the NRC might not let him/her do it. Also, all of us dol goats might want to keep in mind that some of the damage mechanisms from radiation exposure and from smoking use similar pathways -- just in case any of us are volunteering to fly to Mars.

Thursday, May 25, 2006 10:16:00 PM  
Blogger Clark said...

When we get to the point that large numbers of people want to live in space, we will also be at the point where mass delivery of bulk cargo will become supportable. This could initially be done with "dumb boosters" like George Herbert has long championed or with something like the Loral Aquarius system. (The guy who is leading that program was telling me how it would be an excellent way to support a Mars cycler.) Eventually, perhaps laser launch or some type of catapult system could be used.

If there is in fact substantial water on the Moon then it can be used there for shielding in addition to regolith. Water has the nice feature that it is transparent. With a bit of design imagination, a 2nd or 3rd generation lunar facility could take advantage of that to use a water tank with windows for part of a wall or ceiling and let in external light directly and still provide excellent rad protection.

Again, the point is not that you can or need to provide earth surface level radiation levels for today's or tomorrow's habitats and space transport. The point is to refute the idea that there is something inherently unstoppable about space radiation and so we can never live there. I suggest if you look around you will find that meme becoming more and more common in the popular press.

With regard to magnetic and electrostatic shielding, such techniques will almost certainly be in combination with material shielding. The fields won't have to be sufficient to stop all of the charged rad on their own. And the fields will obviously be kept external to the living areas. As in the SciAM paper, you are presenting all or nothing extremes as though they are killer objections when in fact realistic designs don't require extreme solutions.

This paper
discusses electrostatic shielding concepts for a lunar base and includes a nice discussion of GCR and solar radiation. This paper describes some ideas for magnetic shielding:
- Clark

Friday, May 26, 2006 11:35:00 AM  
Blogger Clark said...

Whoops, looks like this system doesn't automatically link URLs. Let me try doing it manually:
magnetic shielding pdf
electrostatic shielding pdf
- C.

Friday, May 26, 2006 11:38:00 AM  
Blogger TomsRants said...

Ya gotta love it - in the midst of all this serious talk, Google Ads chimes in with an ad for Geiger counters...

Friday, May 26, 2006 5:55:00 PM  

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