Nuclear Free by 2045?: Curiosity about Plutonium in Spacecraft

"You may leave here for four days in space

But when you return, it's the same old place"

Barry McGuire, Eve of Destruction

The landing of the NASA Mars rover, Curiosity, was big news on August 6, 2012, but in the media fanfare there was scant discussion of the implications of it being powered by 4.8 kilograms of plutonium-238. When it was launched last November, NASA was not keen to inform the public about the risks involved, what the nation needs to do to maintain the supply, or the disturbing history of failed launches of and crash landings of other rockets and satellites loaded with nuclear materials.

In fact, NASA is in a public relations bind right now because the continued exploration of deep space requires nuclear-fueled probes, but supplies of plutonium-238 are soon to be depleted, as reported by NPR last year when the Mars rover was launched. The only way to get more is to lobby for a new program of plutonium production, but NASA knows the American public has little appetite for the expense, nor for revisiting the dark times of the Cold War when plutonium production left a legacy of damaged health of nuclear workers and environmental pollution at numerous sites. Furthermore, the public is conscious of the odds of launch failures and disasters, and so it is not a good thing to remind them that the rocket on the launch pad has a payload of plutonium that could melt and fall back to earth if the launch fails. Thus NASA’s strategy is to mention the plutonium shortage as little as possible, and not lobby for funding too loudly. Instead, NASA, and other space agencies, play up the romance of boldly going to new frontiers and the importance of new endeavors. It is unthinkable that the space program could be halted just because of the public’s reluctance to produce the required plutonium.

One can suggest at this point the unthinkable, that the space program is just not worth it if it involves the costs and dangers of making and handling plutonium. Space will always be there. What’s the hurry? Let’s wait until we figure out a safe way to do it, or not do it at all. The physicist Michio Kaku has said NASA's renewed interest in not only nuclear powered probes, but the more dangerous nuclear propulsion "… is not only dangerous but politically unwise. The only thing that can kill the U.S. space program is a nuclear disaster. The American people will not tolerate a Chernobyl in the sky."

The drawback to arguing against space exploration is that whoever makes it is immediately on the defensive, accused of being against progress, or the type who would shoot down a child’s dream to be an astronaut. Here in Japan, my children are exposed to a steady stream of news features and documentaries about JAXA (Japan Aerospace Exploration Agency) and Japanese astronauts on NASA missions. The JAXA headquarters in nearby Tsukuba holds tours and events for children every summer. There is a popular manga and anime series called Space Brothers (Uchuu Kyoudai) about two young men living their childhood dream of joining a NASA mission. My children are all hooked. This is how space agencies, and the associated military, chemical and nuclear industries behind them, cynically play the public relations game. It is all packaged as benevolent scientific progress for mankind, and it takes advantage of the child’s desire to transcend the ordinary and engage in imaginative play. Through these education programs and works of fiction, children all know the amusing factoids about food in tubes and what happens to farts on the space shuttle, but no one teaches them about the Radioisotope Heater Unit and what is required to make one.

One can stand up to this onslaught and suggest that progress might lie in learning how to clean up our planet and live on it within its ability to sustain us, but the brilliance of this propaganda system is that whoever does so will be seen as a cynic who just wants to deprive children of their dreams. It’s less cynical than building those dreams on concealed truths, but this point will also go unmentioned along with some facts about what is needed to produce a few kilograms of plutonium-238 for a single space mission.

Plutonium can exist in several isotopes, all of which vary in the length of their half-lives, the intensity of the life-damaging radiation they emit, and in their applications. The number of protons in an atom’s nucleus defines the atom, but the number of neutrons can vary to make different isotopes of the same atom. Plutonium-244 (the number being the total number of neutrons and protons in the nucleus of the isotope) is found in trace amounts in nature, but almost all plutonium now on earth was created by human activity over the last seventy years. In this sense, it is said to be something that no life form has evolved with. Since it damages chromosomes, there is a good argument to be made that it should never be created or used, no matter how well we imagine that its contact with living things can be managed safely.

Various isotopes of plutonium can be created by bombarding other radioisotopes with neutrons. For example, the fissile isotope plutonium-239 used in nuclear weapons is made by bombarding uranium-238. In this way, plutonium for weapons is inextricably linked to the “peaceful” uses of the atom because nuclear fuel in in light water reactors (enriched uranium) used for generating electricity is bombarded with neutrons, leaving behind nuclear waste containing plutonium that can be used to make bombs. The isotope required for space missions is plutonium-238, which emits higher radioactive energy and has a shorter half-life than plutonium-239. Nuclear waste contains only small amounts of plutonium-238, so it can’t be obtained directly from this source. However, spent nuclear fuel contains neptunium-237, and this can be separated from the spent fuel and irradiated to create plutonium-238. A 100-kg sample of spent fuel can yield 700 grams of neptunium-237.

Once you understand what is involved in obtaining a small quantity of plutonium-238, you understand why space agencies are so reluctant to talk about it, even though they need to play politics to get more funding. Production involves numerous problems such as cost, safety, security, and the ongoing problem of cleaning up contaminated environments and storing the plutonium waste already in existence. Space Daily reported in 2003, “Historically DoE has a bad track record when it comes to protecting workers and local water systems from radioactive contaminants… During the Cassini RTG fabrication process at Los Alamos 244 cases of worker contamination were reported to the DoE.”

A nation that wants to send a probe deep into space where the sun don’t shine on solar panels (i.e. Jupiter, Uranus and beyond) needs the entire infrastructure of a large nuclear industry. Spacecraft require a small amount of plutonium-238, which requires the production of enriched uranium, which requires a fleet of civilian nuclear reactors that will provide the nuclear waste from which to make the plutonium-238. The nuclear waste has to be moved around to various facilities, with tight security and all the associated risks. And of course, only a few self-anointed countries are allowed to engage in this production process. The Soviets used polonium 210 (the same isotope that was used to murder the Russian spy Alexander Litvinenko in 2006) on many satellites and the Lunokhod series of moon rovers, one of which exploded on the launch pad in 1969. A country needs to be a major nuclear power to be in the space exploration business, so if you’re a child in Iran, which the major nuclear powers won’t allow to produce enriched uranium, or just a country without the resources for (or the wisdom not to spend resources on) space exploration, the dream of being an astronaut has been denied to you.

So what are the risks?

There is a lot of controversy over the risks involved in sending payloads of plutonium into space. NASA says that the fuel is packed into ceramic and graphite-coated pellets that have been tested to resist impact and melting in the event of an explosion on launch or a fall from orbit. Critics point out that the risk is not easily understood because the small amount of plutonium-238 involved is very radioactive compared to other isotopes of plutonium.

Not all radioisotopes release, by mass, equal amounts of radiation. Plutonium-239 has a long half-life of 24,110 years, but 277 times less energy that plutonium-238, which has a half-life of 87.7 years. Wired Magazine, that consistent cheerleader of all technological progress, commented about this isotope being aboard rockets:

The plutonium (which is, not to worry, non-weapons-grade Pu-238) undergoes nuclear decay, providing heat to warm MSL’s electronics and keep it churning out data even at night.

It may not be weapons-grade, but the writer is gullible to NASA PR saying that it is safe, and he fails to notice the glaring omission in this quote:

They [NASA] point out that NASA has reliably used nuclear generators for 26 missions over the last 50 years.

Yes, reliably in 26, but unreliably in the two mishaps mentioned below that NASA neglected to point out to the Wired journalist. This would amount to 28 missions, with a record of 1 failure for every 14 successes. NASA’s recent estimates of failure probability give much more favorable odds than the actual record, especially if you include the Challenger and Columbia disasters which, fortunately, did not carry radioactive payloads (as far as we know).

If you think of a rocket exploding high in the atmosphere and scattering 4.8 kilograms of material throughout the vast expanse of the earth’s atmosphere, that may seem insignificant. But, in fact, it is a massive release of radioactive energy, and some experts say the impact has been significant.

Not all radioisotopes are created equal.

Plutonium-238 is 277 times as radioactive as plutonium-239, so…

plutonium-238 on the Mars rover Curiosity	4.8 kilograms
plutonium-239 used in the bombing of Nagasaki	6.4 kilograms
amount of plutonium-238 that has the same radioactive energy as the plutonium-239 used in the Nagasaki bomb	6.4 ÷ 277 = 0.0231 kilograms
energy equivalence of 4.8 kilograms of plutonium-238	4.8 x 277 = 1,329 kilograms of plutonium-239
Curiosity radioactivity payload equals how many Nagasaki bombs?	1,329 ÷ 6.4 = 208

In spite of the invention of ways to contain plutonium within ceramic pellets and graphite, NASA’s own Final Environmental Impact Statement for the Mars Science Laboratory Mission finds there is still a chance of environmental release of plutonium in various accident scenarios. It might be foolish to spend much time on a discussion of the probabilities of various scenarios because the methodologies and assumptions involved render the undertaking an absurd game. Nonetheless, NASA concludes “… there is an overall probability of 4 in 1,000 that the MSL mission would result in an accident with a release of PuO₂ [plutonium dioxide] into the environment.” About a less likely scenario it states, “The risk assessment also indicates that in at least one very unlikely ground impact configuration, FSII with a total probability of release of 9.2 x 10^-5 (or 1 in 11,000), a mean area of 86 km² could be contaminated above 0.2 microcuries/m²… Land areas contaminated at levels above 0.2 microcuries/m² (or 7,440 becquerels/m²) would potentially need further action, such as monitoring and cleanup.” For mixed use urban areas, this cost is estimated to be $562 million per km². These estimates include no guess about how far above 0.2 the levels could go. But note that when a radiological disaster does occur, this level of 0.2, or 7,440 becquerels/m²is suddenly deemed too low to require action. By the standards set for Chernobyl, places with less than 37,000 becquerels/m² were considered weakly contaminated. Recommended evacuation (that included permission to leave in the old system of Soviet restrictions on movement) began at 555,000 becquerels/m². Compulsory, compensated evacuation began at 1,480,000 becquerels/m². The Japanese authorities have been similarly complacent since the Fukushima disaster.

In addition, the NASA report mentions, but finds incalculable, the costs of relocation, loss of employment, damage to fishing and agriculture, and health care. Finally, the report concludes with an interesting rationalization for the risks imposed on the public. “The individual risk estimates are small compared to other risks… in [the year] 2000 the average individual risk of accidental death was about 1 in 3,000 per year, while the average individual risk of death due to any disease, including cancer, was about 1 in 130.”

Consider how this logic appears when a drug dealer in your neighborhood turns his house into a methamphetamine lab and contaminates the area. He is likely to rationalize the imposition of risk, which you were not able to have a say in, as only a negligible increase in the risks you already face in your life. It would be better if official agencies of government did not sink to this level of reasoning.

As mentioned above, earlier NASA missions loaded with plutonium failed. The worst one occurred in 1964 with the SNAP-9A Radioisotopic Thermo Generator (RTG). 950 grams of plutonium-238 was widely dispersed over the earth when the satellite containing the RTG fell back to earth. Comparative data on this event can be found in the FEIS of the Mars Science Laboratory Mission.

Table compiled from data provided by NASA’s FEIS for the Mars Science Laboratory Mission and Isotopic evidence of plutonium release into the environment from the Fukushima DNPP accident

	Global releases of plutonium (Curies)
	Pu 239	Pu -238
weapons tests	444,000	9,000
SNAP-9A accident*	*	17,000 (25% fell on Northern Hemisphere, 75% on Southern)
Chernobyl accident**	Plutonium-239, 241: 2,351	400
Chernobyl accident**	Plutonium-240: 194,594
plutonium reprocessing (1952-1992) discharged into oceans	100,000	3,400
TOTAL	740,945	29,800
Total fallout from all isotopes	740,945 + 29,800 = 770,745
Percentage of total fallout from SNAP-9A accident	770,745 ÷ 29,800 = 4%

NASA states the following equivalence:

Plutonium-238 is 17.12 Curies/gram, Plutonium-239 is 0.0620 Curies/gram

* NASA considered the inventory of plutonium-239 on SNAP-9A too small to include.

** NASA did not consider the releases of plutonium-239, 240 and 241 from Chernobyl to be worth mentioning or looking up, but the author calculated them from the data in becquerels given in Zhang et. al. According to this source, the plutonium releases from the Fukushima disaster are estimated to be five orders of magnitude less than the Chernobyl disaster, making them too small to include here. The conversion factor is 1 Curie = 3.7 x 10¹⁰ becquerels.

Plutonium released from Chernobyl (converted to Curies in the table above):

plutonium 239 and 240	8.7 x 10¹³becquerels
plutonium 241	7.2 x 10¹⁵ becquerels

This single mishap of the SNAP-9A unit, involving less than a kilogram of plutonium, accounts for 4% of the plutonium-derived radioactivity released into the environment since the start of the nuclear age. Another part of NASA’s website, not the FEIS, explains these failures with great understatement and typical omission of inconvenient facts. The failure of the satellite in 1964, involving the SNAP-9A Radioisotope Thermal Generator (RTG) is described this way:

Status: Mission was aborted because of launch vehicle failure. RTG burned up on re-entry as designed.

On the other hand, the loss of the Apollo 13 lunar module in 1970 was described differently. People familiar with the story of this failed mission know that the astronauts survived by staying in the lunar module as long as possible, but it was discarded from the main capsule just before re-entry. The lunar module crashed into the South Pacific along with its payload of plutonium-238 in the SNAP-27 RTG. In this case, NASA describes the loss this way:

Status: Mission aborted on the way to the moon. RTG re-entered earth's atmosphere and landed in South Pacific Ocean. No radiation was released.

In the latter case, NASA specifies that no radiation was released, but in the former case there is no mention of whether radiation was released. In fact, the failure of the SNAP-9A was one of many “lessons learned” in the history of nuclear technology. NASA admitted that a large volume of plutonium was released into the earth’s atmosphere, and they subsequently developed solar energy technology, as well as the ceramic and graphite casings for plutonium pellets which, presumably, meant that the plutonium aboard the Apollo 13 lunar module went to the bottom of the sea encased in its protective shells to safely decay through several half-lives of 87.7 years. The same presumption of safety holds for numerous other payloads of plutonium that have been launched into space since 1970. The Cassini space probe, for example, launched in 1997, carries 36.2 kilograms of plutonium-238.

The health effects of the 1964 accident, and the potential effects of future accidents, have become controversial. According to a study titled Emergency Preparedness for Nuclear-Powered Satellites, the 2.1 pounds [950 grams] of Plutonium-238 in the SNAP-9A dispersed widely over the Earth. “A worldwide soil sampling program carried out in 1970 showed SNAP-9A debris present at all continents and at all latitudes.” (cited in Grossman, K.)

Dr. John Gofman, a scientist on the Manhattan Project who later broke ranks with the nuclear establishment, claimed the 1964 accident, on its own and added to the effects of fallout from weapons testing, contributed to a rise in global lung cancer cases. Yet his findings were contested by Snipes et. al. Gofman claimed that most of the lung cancer cases would occur in smokers because they clear particles from their lungs much more slowly than non-smokers. These critics claimed that an assessment of the risk of plutonium would have to be based on healthy individuals. Nonetheless, Gofman still found there is a substantial risk for non-smokers, well-known because of American government studies of non-smoking dogs and rats sacrificed for research (Bair & Thompson). The risk is more acute for the “plutonium workers” who have to handle and transport the nuclear material produced for the civilian and military nuclear complex. When it comes to the general population, proponents on either side of the controversy could never agree on how much plutonium people have ingested and what the effects could be. Regardless, one can make a value judgment and question the wisdom of introducing into the world a known toxic primordial nuclide that has not been present during the evolution of life.

Other great moments in space exploration

The 1978 crash of the Soviet satellite Cosmos 954 spread uranium-235 debris over 77,000 square miles of Northern Canada. There was a media uproar at the time (like there never was about the American SNAP-9A accident), and debates in parliament about the assault on Canadian sovereignty, but the incident was quickly resolved and brushed out of public awareness. There was a joint Canadian and American cleanup, Operation Morning Light, that lasted one year, and the discovery of some highly radioactive debris, but also official assurances that the accident would have no health effects, that all the dangerous material had “harmlessly” disintegrated, melted, vaporized, neutralized or dispersed in such dilute amounts as to not be a concern. During the cleanup, only an estimated 0.1% of the radioactive fuel was recovered, and the fragments of the satellite that were found gave off a deadly 1.1 sieverts per hour. The rest of the radioactive fragments are still out there over the Great White North, at the bottom of Great Slave Lake, or the remainder of the uranium dispersed high in the atmosphere to have its controversial and unknown effects on human health. This is how it was described six years later in the journal Health Physics:

It was estimated that about one-quarter of the reactor core descended over Canada's Northwest Territories in the form of sub-millimeter particles. The other three-quarters apparently remained as fine dust in the upper atmosphere. Each particle contained megabecquerel quantities of the fission products 95Zr, 95Nb, 103Ru, 106Ru, 141Ce and 144Ce, as well as traces of other fission and activation products. Laboratory tests indicated that these radionuclides would not dissolve significantly in drinking water supplies or in dilute acids. Contamination of air, drinking water, soil and food supplies was not detected. The dose equivalent to the GI tract for an individual who might have inhaled or ingested a particle could have been as high as 140 mSv.

Gary Bennett, an American expert on nuclear power and propulsion, described how the Cosmos accident disrupted the consensus on nuclear power in space that existed in the UN Committee on the Peaceful Uses of Outer Space (COPUOS). In a paper tellingly entitled Reaching the Outer Planets – with or without the UN, he states that the agreement at the time “...represented not only a consensus of international technical experts but also a succinct statement of the US position.” But then for the Canadian delegation, and other concerned countries, the Cosmos accident had changed everything. If such a crash had occurred over a populated area, the effects could have been horrendous. By 1981, Bennett says, “…several delegations, led by the Canadian contingent, had introduced working papers proposing new or different technical principles.” Bennett laments, “To a number of people on the US side, it appeared almost as if the Canadian delegation had decided to punish the US rather than the Soviet Union for the accidental reentry of the Soviet Cosmos 954 reactor.”

Bennett notes that differences within different US departments and agencies led to the State department signing on to principles that banned nuclear power in space. They essentially prohibited the nuclear devices now in use on Curiosity and Cassini. He blames this sorry state on the lack of technical expertise on UN committees and the lack of resolve of US negotiators. The result occurred because “… beliefs and wishes and ideology seem to count for more than technical reality.” This is the blind spot of career scientists in institutions such as NASA. Whenever the outcome is unsatisfactory, it is the other side that has been emotional and ideological, while their own self-interests and emotions are not acknowledged - they are believed to be a neutral “technical reality.” There is no acknowledgement here that the UN principles were a value judgment that simply said no to the risks involved in putting nuclear materials in space.

However, we know that the US went ahead with its program and continued to launch nuclear devices into space. Bennett is disappointed that the US chose a passive aggressive approach by voting for the UN principles while intending to ignore them because they were deemed to be non-binding. “In short, the US may have voted for the principles, but it does not intend to abide by them.” He quotes from a Clinton administration memorandum (not cited):

… the proposed position does not confer US approval of any specific provisions of the Principles, but only declares that US policy and practice is consistent with their overall objective and intent, which is the safe use of NPS in outer space.

Nuclear Propulsion Rockets

It is risky enough that we launch small amounts of plutonium into space in order to give a little heat and electricity to long-lasting probes and Mars rovers, but a truly awesome risk is posed by the temptation of using nuclear reactors to launch the rocket itself, or propel a spacecraft to Mars at high speed. This was seriously attempted in the 1960s in Project Orion (for more detail see the BBC documentary To Mars by A-Bomb: The Secret History of Project Orion), but it was scrapped because of the hazards and the frightening radiological accidents that happened beyond public awareness, and the because it would accelerate the arms race with the Soviets. However, the fact that this dream was abandoned once is no guarantee that it won’t be taken up again. In fact, the renewal of nuclear propulsion was behind George Bush’s attempt to dream big, aping Kennedy’s initiative to put Americans on the moon, in announcing that he wanted a manned mission to Mars. Furthermore, nuclear devices in space have not only peaceful purposes. They would be an essential part of any space-based defense system, and this is further reason why other states are suspicious of American plans and why the United Nations, through COPUOS, has tried to downplay the dangers of a space-based arms race.

The history of nuclear propulsion research is still not fully known because many of the files are still classified. In the book Area 51, journalist Annie Jacobsen focuses less on the speculation about freaky aliens at the secret Nevada Test Site and more on what is known about the real events that happened there. These are frightening enough without having any UFOs in the picture. The Kiwi test, which actually occurred in Area 25, was a test to see how badly the environment would be affected by a failure of a nuclear propelled rocket. Engineers designed a small-scale deliberate failure, then watched what happened when they blew up the small reactor core in the rocket. Here is how it is described in Jacobsen’s book (pages 309-310):

On January 12, 1965, a nuclear rocket engine, code-named Kiwi, was allowed to overheat. High-speed cameras recorded the event. The temperature rose to "over 4,000 degrees C until it burst, sending fuel hurtling skyward, glowing every color of the rainbow," Dewar wrote. Deadly radioactive fuel chunks as large as 148 pounds shot up into the sky. One ninety-eight-pound piece of radioactive fuel landed more than a quarter mile away.
Once the explosion subsided, a radioactive cloud rose up from the desert floor and "stabilized at 2,600 feet" where it was met by an EG&G aircraft "equipped with samplers mounted on its wings." The cloud hung in the sky and began to drift east then west. "IT blew over Los Angeles and out to sea," Dewar explained. The full data on the EG&G radiation measurement remains classified.
The test, made public as a "safety-test," caused an international incident. The Soviet Union said it violated the Limited Test Ban Treaty of 1963, which of course it did.

The one other occasion when witnesses to a nuclear explosion described fuel going skyward in “every color of the rainbow” is the explosion of the Chernobyl reactor (see The True Battle of Chernobyl, 0:01:20-0:02:10). The Kiwi test, like the unplanned Rocketdyne meltdown near Los Angeles in 1959, suggests that Three Mile Island is on record as the most serious American nuclear accident only because it is the accident that the public has information about.

The controversy of nuclear power in space is not something that can be resolved by pursuing the correct data on risk assessment, or looking for a way to quantify the harm done by the global population’s inhalation of plutonium particles. These numbers are unknowable. What is clear is that further space exploration will not happen by known methods without the continued processing of plutonium and launching of it into space. For those whose careers are invested in space exploration, and the millions of dreamers and enthusiasts of space travel, it is unthinkable that space exploration could just stop because we are afraid to live with the risks of plutonium processing.

I suspect, however, that most of the 7 billion people on earth don’t even think about space exploration, and wouldn’t care much about it if they did. For others who are informed and primarily concerned about taking care of the planet we inhabit, space exploration has little to offer, especially if it worsens ecological problems. I haven't discussed here the additional harm done by CO2 emissions of rocket launches and rocket fuel chemicals. Certainly, we obtain valuable data from satellites about the minute details of what we are doing to the ecosystem, but they really only confirm simple truths that we already know.

Supporters of space exploration tell us constantly of the necessity of breaking new frontiers, of constantly going beyond, but most of the talk is vague and the logic is circular. We need to keep going farther to develop STEM (education in science, technology, engineering and mathematics), and we need STEM in order to keep going boldly to the next frontier.

People like Peter Diamandis typify the views of what has come to be called the techno-optimists – wealthy high-tech entrepreneurs who get juiced up annually on mutual self-adoration and wonderment at the TED conference. He effuses, with the redundant adjective in the title, Curiosity’s Successful, Glorious Triumph on Mars:

What the success of Curiosity highlights is the importance of our being bold and audacious. It takes big risks to drive breakthroughs. Financial risks, technical risks, and when it comes to funding billion dollar programs - political risks….

He fails to mention the risks taken by the low-level workers who actually handle the plutonium and get contaminated in the process. When you are at the lofty heights of the technological elite who get to stare off into the distance of humanity’s glorious future, the gritty details of how humanity gets there are of no import. The techno-optimists are the conquistadors of the modern age. They are optimists in the same way the Hernan Cortes had a positive view about the conquest of Mexico. It goes without mentioning that most of humanity will be used, abused or ignored in the great march of progress. Yet at least the Spanish conquistadors had the sense to covet places that could sustain life, something which we can’t say about people who want to go to lifeless planets.
Diamandis goes on to say:

I spend much of my time as Executive Chairman of Singularity University and as CEO of the X PRIZE Foundation. At SU we teach attending graduate students and executives about exponentially growing technology. More importantly, we speak about the importance of taking risk to truly create breakthroughs and the importance of failing early and failing often - the Silicon Valley formulation for innovation.

What is not mentioned here is that humanity actually has not been afraid to take risks, and we seem to be adept at failing spectacularly. In truth, we are quite reckless. While the ecosystem we depend on collapses, Diamandis and his kind have their heads in the clouds envisioning a melding of human minds with robots. Our energy problem is not that fossil fuel supplies will soon be depleted but that catastrophic climate change will occur first. There is nothing more urgent than facing the escalating disasters caused by climate change and the unresolved problem of nuclear waste storage. Outer space can wait. If it seems too sad to tell our children to put this dream on hold, that’s unfortunate, but the unavoidably mature thing for adults to do. Instead of asking our children if they want to be astronauts when they grow up, it is time for the human race to ask itself what it wants to be when it grows up.

References and Other Resources

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Bennett, Gary L. “Reaching the Outer Planets – with or without the UN.” Aerospace America. The American Institute of Aeronautics and Astronautics. July, 1996. http://www.fas.org/nuke/space/aeroamer.pdf

Collins, Michael, Trossman Bien, Joan. “50 Years After America’s Worst Nuclear Meltdown.” Pacific Standard. August 24, 2009. http://www.psmag.com/science-environment/50-years-after-nuclear-meltdown-3510/

Davidson, Keay. “NASA's nuclear-fueled oddsmaking: Assurances can't calm fears of a 'Chernobyl in the sky.'” San Francisco Chronicle. April 28, 2003. http://www.sfgate.com/default/article/NASA-s-nuclear-fueled-oddsmaking-Assurances-2619688.php

Diamandis, Peter. Curiosity’s Successful, Glorious Triumph on Mars. August 9, 2012. http://www.huffingtonpost.com/x-prize-foundation/curiositys-successful-glo_b_1748678.html

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Gagnon, Bruce. “Nuclear Power in Space and the Impact on Earth’s Ecosystem.” Space Daily. January 27, 2003. http://www.spacedaily.com/news/nuclearspace-03b.html

Global Network Against Weapons and Nuclear Power in Space. http://www.space4peace.org/

Gofman, John D., “The Plutonium Controversy.” The Journal of the American Medical Association (JAMA). July 19, 1976 vol. 236, No. 3 pp. 284-288. http://jama.jamanetwork.com/article.aspx?articleid=346814

Greenfield-Boyce, Nell. “The Plutonium Problem: Who Pays For Space Fuel?” National Public Radio (NPR). November 8, 2011. http://www.npr.org/2011/11/08/141931325/the-plutonium-problem-who-pays-for-space-fuel

Jacobsen, Annie. Area 51: An Uncensored History of America’s Top Secret Military Base. Back Bay Books, 2012. The passage cited here quotes Dewar, James, To the End of the Solar System: The Story of the Nuclear Rocket, University Press of Kentucky, 2004.

Johnson, Thomas (Dir.). The Battle of Chernobyl. Icarus Films. 2006.

Mann, Adam. “Nuclear Battery Will Warm Giant Rover on Frigid Mars Treks.” Wired Magazine. November 22, 2011. http://www.wired.com/wiredscience/2011/11/nuclear-mars-rover/

McKibben, Bill. “Global Warming’s Terrifying New Math.” Rolling Stone. July 19, 2012. http://www.rollingstone.com/politics/news/global-warmings-terrifying-new-math-20120719.

NASA. “Final Environmental Impact Statement on the Mars Science Laboratory Mission. Volume 1 Executive Summary and Chapters 1 through 8.” NASA. 2006. http://science.nasa.gov/media/medialibrary/2010/11/05/MSL-FEIS_Vol1.pdf

Newman, Lee S., Mroz, Margaret M., Ruttenber, James A. “Lung Fibrosis in Plutonium Workers.” Radiation Research 164, pp. 123-135. 2005. http://www.cdc.gov/niosh/oerp/pdfs/2001-133g25-1.pdf