Comments on space debris sent to Wendy Wolfson, Information Week, by Russell Hoffman -- April 10th, 2001

To: Wendy Wolfson, Information Week
From: Russell Hoffman, Concerned Citizen, Carlsbad, California
Re: Your article on Space Debris in Information Week
Date: April 10th, 2001

Dear Ms Wolfson,

I have been worrying about space debris for several decades now, as a private, concerned citizen, and have posted a number of essays about the problem at my Space Debris web site (URL given below).

Your article on space debris (shown below) was one of the best I've read, because you're one of the few reporters to include the fact that despite their watching about 10,000 pieces of space junk, there are millions of pieces up there circling Earth which can catastrophically damage any spaceship. Most reporters only write about the 10,000 pieces they are actually able to watch.

Unfortunately, you left out one big thing: The radiological burden of a lot of space debris. Russia, for example, has left several dozen nuclear Cold War reactors up there, which are prone to being exploded apart by other debris, some are already leaking primary coolant, and which are all falling back to Earth, in 400 year to 1000 year time-frames.

America too has left nuclear reactors and countless plutonium payloads in orbit around Earth. Some of these payloads are civilian; they are listed in, for example, the 1995 Final EIS for the Cassini Mission (page 2-13), which is available in PDF format at NASA's Cassini web site (URL given below). But many others are military. We don't know how many, but we can be pretty certain that a lot of them are up there as well. In fact, the civilian use appears to be little more than a cover for the military use of plutonium in space.

The plutonium is used for two purposes, both replaceable with non-nuclear technologies for civilian purposes. One use is as a simple heat source -- these are called Radioactive Heater Units (RHUs). Cassini had about 127 of these on board, for example, and the next civilian launch with RHUs on board is expected (if we citizens can't stop it) to be Mars Exploration Rover -- 2003, with up to 11 RHUs. Each RHU contains about 2.7 million lethal doses of plutonium, using the rule of thumb of 1 million lethal doses per gram of plutonium (a conservative figure).

The other use of plutonium is for Radioactive Thermoelectric Generators (RTGs) which produce electricity by placing a thermocouple near the plutonium and using the heat to create an electrical current. It takes a lot of plutonium to create a modest amount of electricity this way -- 25 pounds of plutonium will produce about 250 watts of electricity. Cassini has three RTGs on board, with 72.3 pounds of plutonium dioxide. That is hundreds of billions of lethal doses of plutonium.

In both cases, both for RHUs and RTGs, accidents can happen. In both cases they contain a mix of Pu 238 and Pu 239. Pu 239 is weapons-grade plutonium, but most of the plutonium is Pu 238, which has a half-life about 280 times shorter than Pu 239 (88 years versus 24,100 years). The containment system NASA uses is utterly inadequate -- so inadequate that the RHUs on Cassini were expected (even by NASA, although it was buried in their documentation and never discussed) to completely incinerate in a flyby reentry accident. The RTGs were expected to partially incinerate, or even to completely incinerate in some reentry modes. That would have added a huge radiological burden to mankind's fragile ecosystem.

The shorter half-life of Pu 238 over Pu 239 means that the plutonium is giving off proportionately that many more alpha particles per unit of time -- 280 times more to start. So Pu 238 is far, far more virulent (cancer-causing) when vaporized and spread into the environment. Plutonium 239 is often called the most deadly substance on Earth, but that's ignoring Pu 238, which is, when spread into the environment, 280 times more deadly (for less time, but still for many generations).

And guess what? Reentry vaporization produces an aerosol of particles which are the "IDEAL" size for lodging permanently in the human lung. (see page D-9 of the 1995 FEIS where the particle size is mentioned). Vaporization does not render the plutonium harmless, it just spreads it around. The full spectrum of health effects -- cancer, leukemia, birth defects -- occurs at any dose level. Only the rate that those health effects occur within a population goes down as the dose size goes down. This protects NASA from culpability but doesn't save lives.

NASA has two orbiting RTGs right now which have NO containment system at all and all of their contents will be vaporized when, eventually, they reenter Earth's atmosphere. Another unprotected RTG, called SNAP-9A, reentered Earth's atmosphere in 1964. Public outcry caused NASA to build a containment system after that, a containment system which is surely inadequate, according to many scientists, and which in any case causes NASA to have to carry a lot more plutonium to get the same amount of electricity.

Of all the problems of space debris, nuclear waste in space is the worst horror and the most covered-up and ignored by NASA and its supporters. I hope you will want to do another article about this problem, or at least include some facts about it in future articles you might write.

Thank you for your time and I would be happy to answer any questions you might have, or refer you to others who can do so.


Russell Hoffman
Concerned Citizen
Carlsbad, California

Related URLs:

My Space Debris home page:

NASA's Cassini web site home page (very hard to find if you just go to

My STOP CASSINI web site home page (about 400 posted items, including 253 issues of my newsletter):

Article by Dr. Horst Poehler about NASA's flimsy Pu containment systems:

My own personal home page:

Your article in Information Week (shown below):


What Sticks:
The truth is up there
By Wendy Wolfson (
More "What Sticks" Columns:
Nerd Gladiators Face Off, Save America

All eyes turned to the sky when the Soviet-era MIR Space Station recently descended from orbit into an unpopulated part of the Pacific Ocean. According to AP reports, scientists predicted that about 27 tons of Mir parts could possibly survive atmospheric immolation to plummet to the earth's surface.

Only one person on earth has ever been reportedly hit by stuff falling from space. In January 1997, a woman in Tulsa, Okla., escaped injury despite being grazed by a bit of metal mesh falling from the sky, debris from an upper-stage U.S.-made Delta rocket used to put a Global Positioning System satellite in orbit almost a year earlier. That same day, in Georgetown, Texas, a farmer's wife told her husband that something that looked like an "upside-down rhinoceros" had just plunked into their yard. It was the rocket's 580-pound stainless-steel tank that missed their house by a scant 50 yards and a major highway by another 150 yards. According to NASA's computer modeling, Delta second-stage components, engineered for durability, are expected to survive reentry every single time their host disintegrates.

While alien spaceship sightings are popular in the public's imagination, they really are much less common than incidents of our own trash falling from the sky. As we increasingly become electronically interconnected in the information age, we depend on a plethora of communications satellites to do things like make phone calls from our plane seats and tune into our favorite TV programs.

More troubling than the infrequent rain of Volkswagen-sized chunks of hot metal is the junk still circulating round our global "hood."

Space garbage, or the scientific euphemism "orbital debris" includes satellites gone bad, sections of booster rockets, bolts, hatches blown off space modules, and bits of chipped paint. Pieces and parts of our satellites and rockets will stay in orbit for millennia or at least until they hit something else orbiting in space, and further fragment into smaller pieces of scrap to whiz around the earth ad infinitum.

Our space program is a marvel of sophisticated engineering and information technology. Perhaps the more complicated and elaborate our computing edifices get, the more vulnerable we are to choking on our own trash.

Call it the "oops" factor.

Our aspirations to the stars could very well be stymied not so much by the restrictions of distance and time, but by the dubious realization that we can't even launch a shuttle out of our front driveway without encountering a steady stream of dangerous orbiting junk 400 miles up. In 40 years of the space program, we've become more sophisticated at putting things up in the sky, but we still haven't quite figured out how to neatly get them back.

In the past year or so, flight controllers have had to rotate the International Space Station (ISS) at least twice to avoid possibly catastrophic collisions with known orbiting junk. Even the venerable Space Shuttle regularly changed its orientation so that threatening debris would hit on the rear, rocket side, instead of striking the crew compartments or an astronaut on a space walk. Each successive decade the ISS is in orbit, according to computer models, it has about a 20% chance of sustaining a "critical penetration."

A large enough piece of debris colliding with the space station at a typical speed of about six miles a second could conceivably implode a pressurized crew module. MIR was intermittently hit by debris large enough to dent the inner wall of the crew compartment. Unlike a pebble crashing toward a car windshield at 60 mph, by the time a fleck of junk appears on the horizon, it strikes too quickly for any evasive maneuvering.

NASA is also developing in-flight repair kits for plugging up larger holes. Duct tape played a critical role in bringing Apollo 13 back to port. Perhaps every shuttle astronaut in the future will be presented with a lunch bag, a roll of duct tape, a caulking gun for larger holes, and hearty well wishes from Mission Control.

One of the first known pieces of space junk was astronaut Ed White's glove floating off during a space walk back in the '70s. Using radar, Earth-bound site operations staff were able to track the glove until it burned up in the atmosphere.

NASA is currently using a variety of sophisticated telescopes and computer-modeling simulation programs to track over 9,500 objects of space debris, melon-size or greater; there may be up to 120,000 items 1 centimeter in size or greater orbiting Earth! The number of particles smaller than 1 centimeter, such as paint flecks, probably exceeds the tens of millions.

Repurposed Cold War technology tracks some objects visually, others by microwaves, and still others by radar stations such as Norway's Arctic Globus II, a few miles from Russian military bases on the Kola Peninsula. The latest Satellite Situation Reports compiled by the NORAD (North American Air Defense) facility at Cheyenne Mountain, Colo., lists an average of 20,000 observations of "uncorrelated targets," otherwise known as space junk, made each day.

Within the past four decades of space exploration, we've already left our mark on the environment and few of the objects display "Property of..." tags. Note the origins of the known junk: The United States almost wins! By the time they get here, would the alien explorers of the future find our planet only a buzzing junk heap? Even if we aren't alone in the universe, due to distance and time considerations, our entire civilization could come and go before extraterrestrial intelligent beings even know we exist.

(as of December 27, 2000)
Country / Organization - Payloads - Rocket Bodies And Debris - Total
China 32 - 338 - 370
CIS 1331 - 2553 - 3884
ESA 30 -238 - 268
India 20 - 5 - 25
Japan 66 - 45 - 111
United States 936 - 2871 - 3807
Other 305 - 26 - 331
TOTALS 2720 - 6076 - 8796

Cataloged by U.S. Space Command

From the Orbital Debris Quarterly News

But look on the bright side: Maybe new forms of life will evolve from the trash we leave behind.

This concept of evolution was promoted in "Allegro Non Troppo" the satiric Italian knockoff of the Disney classic "Fantasia," in which new life on earth evolves from the backwash left in an empty bottle of Coca-Cola tossed into some celestial gutter. This does lead one to hypothesize about the theory that humans are "fertilizing" space, or even about the origins of our own species. Some think that life on earth comes from space bacteria or its by-products.

Nobody has yet come up with a workable solution for cleaning up the garbage. Zapping it with giant, high-powered laser beams to nudge it back into the earth's atmosphere to burn up has been proposed as a sort of cosmic depilatory. Unfortunately, this scheme is impractical from Earth due to its tremendous distance and power requirements.

Probably the best course for larger objects is a process known as de-orbiting, leaving a satellite or rocket enough of a fuel reserve to get it back into Earth's atmosphere, where it can self-incinerate after its task is done. This of course, doesn't address the errant paint flecks orbiting at 17,500 mph.

Of course, not only might the circulating space junk impede our travel more than the restrictions of relativity, but also the parts that don't burn up might end up unexpectedly adorning your front yard. Complaints about errant junk, if it appears to have fallen from the heavens, should be addressed to Michael Golightly, NASA-Johnson Space Center, Space Science Branch, or

Don't forget to check the municipal calendar taped to your fridge--is space junk pickup on every other Tuesday with the recyclables?

On April 16th, 2001 Hoffman received the following reply from Ms Wolfson:

Dear Mr. Hoffman,
Thank you for making that point. I know that the plutonium issue has been very controversial and I should have mentioned it in this essay. But I appreciate your writing me about it.
Kind regards,
Wendy Wolfson



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First posted April, 2001.

Last modified April, 2001.

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