I read Dr. Parker’s article in Scientific American when it first came out. And I find nothing wrong with his analysis.

Prolonged periods of exposure to cosmic radiation is probably deleterious to human health– especially heavy nuclei which can damage the brain.

But there’s nothing in Parker’s article that says heavy nuclei are anywhere close to being as deeply penetrating through materials as protons are– because it simply isn’t true! They’re more dangerous. Yes! But they are not deeply penetrating.

While Parker argues that 5 meters of water (allowing less than 5 Rem of exposure during the solar minimum) should adequately protect humans from dangerous levels of cosmic radiation, those levels are only necessary if astronauts intend to— stay permanently in space. But that’s not the intent for radiation shielding interplanetary vehicles since such journeys will only require enough shielding for several months or a few years of exposure.

On the ISS, Astronauts experience much higher levels radiation than Parker would advocate (20 to 40 Rem annually). Of course, they’re usually only at the ISS for a few months at a time. Mars missions could last up to three years. So you’re definitely going to need more shielding for interplanetary voyages than what the ISS provides.

Less than 20 cm of water would be needed to stop heavy nuclei, and 50 cm should mitigate overall cosmic radiation and spallation to levels of exposure less than 25 Rem per year during the solar minimum (the worse case scenario). Of course, during the solar maximum, radiation exposure will be substantially less.

NASA’s annual astronaut exposure limit is 50 Rem. And lifetime limit for young woman 25 years of age is about 100 Rem.

50 cm of water should also be more than enough to prevent excessive radiation exposure during major solar events.

Marcel

You are never going to convince “billgamesh” to consider anything different on the subject in question.

His “the authority on space radiation” (as if there is only one) is Dr. Eugene Parker and while he did not list the link his source is this article in Scientific American:

https://engineering.dartmouth.edu/~d76205x/research/Shielding/docs/Parker_06.pdf

You will note in this popular science article Dr. Parker continuously uses such prejudicial language as:

– It (meaning space travel) is not quite as bad as venturing inside a nuclear reactor …
– MARS’S PITIFUL ATMOSPHERE (an atmosphere can apparently be pitiful) is scant protection

Then near the end of the last page of the article he leaves himself this bolt hole:

“Natural healing processes in the cell may be able to handle radiation doses that accumulate over an extended period, and some people’s bodies may be better at it than others’. If so, the present estimates of the cancer incidence, all based on short, intense bursts of radiation, may overestimate the danger.”

Then closes with this:

“Capable people might be willing to go to the moon or Mars just for the adventure, come what may. Even so, the radiation hazard would take the luster off the idea of human space travel, let alone full-scale colonization.”

Dr. Parker is indeed a well-respected scientist, but I will leave it to you (and other readers) to decide whether or not he may have an anti-human space flight agenda that may motivate his “analysis”.

“billgamesh”,

Please do not respond to me on this. You seem a well-meaning sort and (while I disagree with you on some – not all – issues) I actually like you. However repeating the same points on radiation over and over again regardless of the subject being discussed serves no purpose.

The only really accurate and informative work I have found on Shielding Space Travelers is the article of the same name by the authority on space radiation. I don’t think you can argue with him about it.

Like I said, bombs work. A vast fortune has been poured into SDI on directed energy devices; pulse propulsion devices are directed energy devices. Thank you Ronald Reagan. Bombs have no moving parts. If one is a dud there are plenty more. As for Isp a pulse propulsion system would have numbers in the tens of thousands. A Bomb system would go into service far sooner than years of trying to make that VASIMR monstrosity operational. KISS.
And Mr. Brown was “strong backer” of whatever would work. He was also notoriously conservative concerning risky propulsion options like Solid Rocket Boosters and hydrogen. But unlike some people, he could change his mind when his arguments were answered. He changed his mind about hydrogen and attributed that propellent with making the Moon landing a success. He also was enthusiastic about about bomb propulsion after a meeting with Freeman Dyson. History.

“Stan Ulam was a mathematician, not an engineer and that was many years ago. Meanwhile science and engineering has gone forward.”

Not a good argument considering the world class scientists and engineers that worked on Project Orion.

It could be objected that the clause that prohibits “national appropriation by claims of sovereignty or use” would also prohibit any property claims. However, there is the long-standing distinction between imperium and dominium that goes back at least to Roman times and is enshrined in US law in places like the Guano Islands Act and the Insular Cases (a series of Supreme Court decisions at the turn of the 20th century).

Basically, at the end of the Spanish-American War, the US had several new territories dumped in its lap: the question was whether such land should be considered part of the sovereign territory (imperium) of the US. The answer was that it was NOT (the problem being that millions of Filipinos, Cubans, and Puerto Ricans would have had to have been given full US citizenship with all the rights that entails). IOW, PI, etc. were considered to be mere property (dominium).

So an analogous process could work on the Moon: Bigelow (or NASA or China) could declare reasonable exclusion zones around their installations that would be their private property for all practical purposes; whereas the sovereign in this case would remain humanity as a whole as per the OST. No contradiction is involved.

As for selling stuff produced on the Moon, I believe that is fully consistent with the OST: IIRC Article 8 states that the ownership of items “constructed” on the Moon is not affected by the mere fact that that they are on the Moon. Thus, even a mere rock where nothing more is done than grabbing and bagging it becomes an artifact due to the fact that it is “taken” out of its natural setting, rather like commercial fisheries on Earth: the wild fish belong to the public as a whole, but once the fish is taken, it belongs to whoever caught it and may be sold. There is already precedent for this: the Russians have sold some of their lunar samples–no one has complained so far….

“The heavy nuclei in the galactic cosmic rays are usually stopped by ionization energy losses within ~10 cm of the lunar surface. Most of the radiation damage induced by these heavy GCR nuclei occurs within the top few centimeters. This radiation damage is so intense that it can be seen as high densities of tracks in lunar samples (Walker, 1975; Reedy et al., 1983) and can cause problems in sensitive electronic components (Adams and Shapiro, 1985). Shielding of a few g/cm2 is usually adequate to remove most of these highly- ionizing heavy GCR nuclei.”

David Vaniman, Robert Reedy, Grant Heiken, Gary Olhoeft, and Wendell Mendell

Chapter 3. The Lunar Environment in:

Lunar Source Book: A Users Guide to the Moon

edited by

GRANT H. HEIKEN
Los Alamos National Laboratory
DAVID T. VANIMAN
Los Alamos National Laboratory
BEVAN M. FRENCH
National Aeronautics and Space Administration

with an intro by Harrison Schmitt (the only scientist ever to visit the Moon).

Read the book. Its full of useful information!

Since TRITON is rooted on NERVA, that alone puts it WAY ahead of any NPP in terms of development.

VASIMR (and other ion propulsion) hav also had hardware built and tested … again, that puts it WAY ahead of any NPP.

Stan Ulam was a mathematician, not an engineer and that was many years ago. Meanwhile science and engineering has gone forward.

Von Braum was a strong backer of nuclear thermal drives:

“In 1969, NERVA’s successes prompted NASA-Marshall Space Flight Center director Wernher von Braun to propose sending 12 men to Mars aboard two rockets, each propelled by three NERVA engines. The mission would launch in November 1981 and land on Mars in August 1982.”

Better is the foe of good enuff. NPP might … MIGHT … work and MIGHT be the best drive but it is all paper right now. It would take years of work to even get to the physical testing phase. In the meantime, the alreddy tested NERVA could put us on Mars … von Braun saw this and that is why he put forth a mission to Mars with NERVA engines. Don’t put off what we can do now for what we MIGHT can do later.