"The recent Fox TV show, which I saw, is an ingenious and
entertaining assemblage of nonsense. The claim that radiation
exposure during the Apollo missions would have been fatal to the
astronauts is only one example of such nonsense." -- Dr. James Van
If you have not yet read the radiation
primer, you are invited to do so.
There is too much
radiation in outer space for manned space travel.
This general charge is usually made by people who don't understand
very much at all about radiation. After witnessing the horrors of
Hiroshima and Nagasaki and the tragedy of Chernobyl it is not
surprising that the idea of radiation should elicit an intuitively
fearful reaction. But when you understand the different types of
radiation and what can be done about them, it becomes a manageable
problem to avoid radiation exposure.
It doesn't matter how
difficult or expensive it might have been to falsify the lunar
landings. Since it was absolutely impossible to solve the radiation
problem, the landings had to have been faked.
This is a common method of argument that attempts to prove
something that can't be proven, by disproving something else.
In this case the reader is compelled to accept the conspiracy theory
and all its attendant problems and improbabilities, simply on the
basis that no matter how difficult, absurd, or far-fetched a
particular proposition may be, if it's the only alternative to
something clearly impossible then it must -- somehow -- have come to
pass. This false dilemma is aimed at pushing the reader past healthy
skepticism and into a frame of mind where the absurd seems plausible.
The false dilemma is only convincing if the supposedly impossible
alternative is made to seem truly impossible. And so conspiracists
argue very strenuously that the radiation from various sources spelled
absolute doom for the Apollo missions. They quote frightening
statistics and cite various highly technical sources to try to
establish to the reader that the radiation poses a deadly threat.
But in fact most conspiracists know only slightly more about
radiation than the average reader. This means only a very few people
in the world can dispute their allegations, and the conspiracists can
simply dismiss them as part of the conspiracy.
The Van Allen belts are
full of deadly radiation, and anyone passing through them would be
Needless to say this is a very simplistic statement. Yes, there
is deadly radiation in the Van Allen belts, but the nature of that
radiation was known to the Apollo engineers and they were able to make
suitable preparations. The principle danger of the Van Allen belts is
high-energy protons, which are not that difficult to shield against.
And the Apollo navigators plotted a course through the thinnest parts
of the belts and arranged for the spacecraft to pass through them
quickly, limiting the exposure.
The Van Allen belts span only about forty degrees of earth's
latitude -- twenty degrees above and below the magnetic equator. The
diagrams of Apollo's translunar trajectory printed in various press
releases are not entirely accurate. They tend to show only a
two-dimensional version of the actual trajectory. The actual
trajectory was three-dimensional. The highly technical reports of
Apollo, accessible to but not generally understood by the public, give
the three-dimensional details of the translunar trajectory.
Each mission flew a slightly different trajectory in order to
access its landing site, but the orbital inclination of the translunar
coast trajectory was always in the neighborhood of 30°. Stated
another way, the geometric plane containing the translunar trajectory
was inclined to the earth's equator by about 30°. A spacecraft
following that trajectory would bypass all but the edges of the Van
This is not to dispute that passage through the Van Allen belts
would be dangerous. But NASA conducted a series of experiments
designed to investigate the nature of the Van Allen belts, culminating
in the repeated traversal of the Southern Atlantic Magnetic Anomaly
(an intense, low-hanging patch of Van Allen belt) by the Gemini 10
NASA defenders make a
big deal about the Southern Atlantic Magnetic Anomaly, but the Apollo
spacecraft ventured into the more intense parts of the
True, but the point was to validate the scientific models using
hard data, and to ascertain that a spacecraft hull would indeed
attenuate the radiation as predicted.
We know the space
shuttle passes through the Southern Atlantic Magnetic Anomaly (SAMA),
but since the shuttle astronauts have time in each orbit to recover,
the effects are not felt as strongly. The Apollo astronauts spent
around four hours at a single stretch in the Van Allen belts. [Mary
This is exactly the opposite of the recovery principle. If the
shuttle astronauts spend 30 minutes of each 90-minute orbit passing
through the SAMA, that sums to an exposure of 8 hours per day. The
human body does not recover from radiation in a matter of minutes but
rather hours and days. The damaged tissue must be regenerated. If
radiation exposure is more or less continuous over several days, such
as in the shuttle scenario, the tissue never has time to regenerate
before being damaged by continuing radiation.
Even though the outlying parts of the Van Allen belts contain more
intense radiation than the SAMA, a four-hour passage followed by days
of relatively little exposure offers a better recovery scenario than
days of accumulated low-level exposure.
A short, intense exposure is safer than continuous or
periodic exposure at lower intensity.
The four-hour figure is reasonable, but somewhat arbitrary. Since
the Van Allen belts vary in flux and energy, it's not as if there's a
clearly demarcated boundary. It's a bit like walking over a hill. If
the slope gently increases from flat and level to 30° or so, where
do you say the hill starts?
It would require six
feet (two meters) of lead in order to shield from the Van Allen belts.
The Apollo spacecraft had nowhere near this amount of shielding and so
could not have provided the astronauts adequate
The "six feet of lead" statistic appears in many conspiracist
charges, but no one has yet owned up to being the definitive source of
that figure. In fact, six feet (2 m) of lead would probably shield
against a very large atomic explosion, far in excess of the normal
radiation encountered in space or in the Van Allen belts.
While such drastic measures are needed to shield against intense,
high-frequency electromagnetic radiation, that is not the nature of
the radiation in the Van Allen belts. In fact, because the Van Allen
belts are composed of high-energy protons and high-energy electrons,
metal shielding is actually counterproductive because of the
Bremsstrahlung that would be induced.
Metals can be used to shield against particle radiation,
but they are not the ideal substance. Polyethylene is the choice of
particle shielding today, and various substances were available to the
Apollo engineers to absorb Van Allen radiation. The fibrous
insulation between the inner and outer hulls of the command module was
likely the most effective form of radiation shielding. When metals
must be used in spacecraft (e.g., for structural strength) then a
lighter metal such as aluminum is better than heavier metals such as
steel or lead. The lower the atomic number, the less Bremsstrahlung.
The notion that only vast amounts of a very heavy metal could
shield against Van Allen belt radiation is a good indicator of how
poorly though out the conspiracist radiation case is. What the
conspiracists say is the only way of shielding against the Van
Allen belt radiation turns out to be the worst way to attempt
to do it!
Official NASA documents
describing the pre-Apollo studies of the Van Allen belts clearly state
that shielding was recommended for the Apollo spacecraft, yet no
shielding was provided. [Mary Bennett and David Percy]
Commensurate with the common perception of radiation as an
inescapably deadly force is the notion of radiation shielding as
universally heavy and dense. Percy and others seem to rely on the
notion that radiation shielding, if present, would have been very
conspicuous -- or prohibitively bulky.
"Shielding" does not always mean thick slabs of dense material.
As discussed in the previous question, shielding against particles
is not the same as shielding against rays. To say that the Apollo
spacecraft did not provide adequate shielding is to ignore both the
construction of the Apollo command module and the principles of
And it must be kept in mind that shielding was only one element of
a multi-pronged solution for safely traversing the Van Allen belts.
It was never intended that the shielding in the command module would
provide the only protection for the astronauts. The shielding was
adequate to protect the astronauts against the circumstances of the
trajectory and exposure duration worked out by the mission planners.
NASA apologists come up
with different numbers for estimates of the exposure in the Van Allen
belts. This suggests they really don't know what they're talking
about. [Mary Bennett and David Percy]
All the estimates we've seen lie within the same order of
magnitude and generally outline a plausible method of computation.
This stands in contrast to the conspiracist estimates which generally
have no quantitative support.
Computing the precise exposure for Apollo astronauts is very
difficult. That's why the astronauts wore dosimeters to measure the
actual exposure. The factors involved in computing expected exposure
Exact trajectory. The Van Allen belts are not uniformly
shaped. They have thick and thin spots. And the level of radiation
is not constant at all points. Toward the center of the belt cross
sections there is more radiation than at the edges. Most Apollo
enthusiasts do not know the exact trajectory or how it relates to the
location of the Van Allen belts. But they know that they don't know
this, and so they frequently do their computations assuming the
astronauts passed through the densest parts, and therefore err on the
side of overestimating the exposure.
Exact velocity. Exposure time is very important to a
correct computation of radiation dosage. Because the velocity of the
spacecraft is constantly changing, the same ambiguity which governs
the geometry of the trajectory also governs the rate at which it is
followed. And most enthusiasts (and all conspiracists) lack the
information and skill to precisely determine the velocity of the
spacecraft during the Van Allen belt traversal, and therefore the
Exact energy and flux. In any given cubic meter of the Van
Allen belts there will be a soup of particles at various energy levels
and fluences. Energy describes the velocity of the particle, how far
it will penetrate, and how much damage it will do if it hits
something. Flux is the density of particles, how many of them pass
through a given area in a second. Generally, the higher the energy
the lower the flux. Low-energy particles (i.e., protons 30 MeV and
below) can be ignored because they do not penetrate the spacecraft
outer hull. But at each point along the trajectory through the Van
Allen belts there is a different continuum of flux and energy. It
requires a lot of mathematics to fully solve this system. And since
some of the variables are hard to determine, they're typically
Probabilistic factors. Even should a high-energy particle
penetrate the spacecraft hull to the interior, it will only cause
problems in the human organism if it is absorbed in tissue. It is
possible for the particles to pass through the body without colliding,
in which case they are harmless. The human body varies in density.
Particles are more likely to collide with dense tissue like bone. The
amount of absorbed radiation is a statistical probability based on how
much radiation is detected by dosimeters.
To summarize then, a fully accurate analytical solution must first
determine the exact trajectory of the spacecraft through the Van Allen
belts. This will give a continuous function describing particle flux
and energy at each point along the trajectory.
At each point in the trajectory we will have a function giving
flux per given energy level. So a 100 MeV proton will have, say, a
flux of 20,000 particles per square centimeter per second at that
point in space. But for other energy levels the flux will be
different at the same point. The total irradiation inside a
spacecraft will be the sum of all the fluences at energies capable of
penetrating the hull and shielding.
And at each point along the trajectory the velocity of the
spacecraft must be determined so it can be known how much time the
spacecraft spends at that point. This is multiplied by the
conglomeration of fluences to arrive at a dose.
This dose is simply the amount of radiation present. It must be
converted to a meaningful value that describes its likely effect on
human tissue. Again, energy and fluence come into play, because
low-energy particles (but still high enough to penetrate the shield)
are likely to accumulated in the outer layers of the skin and cause
damage which is sloughed off harmlessly. High-energy particles are
absorbed in the bones and internal organs, causing much greater
The procedure for analytically computing a radiation dose is
simple enough in principle as outlined above, but of course is very
difficult to actually carry out. This is why engineers generally
don't try to compute the dosage to any great degree of accuracy ahead
of time. They are happy simply to arrive at an order of magnitude
which provides adequate design criteria. The actual radiation
exposure is always measured, not computed.
So then was it measured
Yes. Each astronaut wore a personal dosimeter. The accumulated
dose for each astronaut was regularly reported to Mission Control over
New evidence has shown
that the Van Allen belts are indeed stronger and more dangerous than
NASA says. [Bart Sibrel]
Sibrel misinterprets the source article published by CNN. It was
reported only that the Van Allen belts were slightly larger in places
and slightly denser than previously understood. This is not a new
reality, merely a refinement of existing figures. We are still
studying the Van Allen belts and must occasionally revise our
numerical models. The new findings have implications for the
astronauts in the Alpha space station. Since these astronauts will be
exposed to the fringes of the Van Allen belts for an extended period,
it is prudent now to provide a bit of extra polyethylene shielding to
the sleeping quarters. For transitory exposure such as in Apollo
missions, the new findings add only a negligible hazard.
Sibrel and others argue that NASA has under-reported the intensity
of the Van Allen belts for many years as part of a cover-up. They
argue that the real magnitude of the radiation is now being made
known, and that it's strong enough to have precluded a successful
Unfortunately that's a very naive argument. The United States has
never been the only spacefaring nation, nor the only nation ever to
study the Van Allen belts. Canada provide valuable data to the Apollo
project, and the USSR duplicated all the U.S. research, and may even
have conducted more. For thirty years the same body of engineering
data used to produce the Apollo spacecraft has been used by all
nations in designing communication satellites, probes, and other
devices intended to operate in and beyond the Van Allen belts. If
this data had seriously under-reported the actual radiation present,
the spacecraft engineered to those standards would all have failed
prematurely due to radiation damage.
This is a very important point since it involves the financial
interests (to the tune of billions of dollars!) of countries with no
special desire to protect the reputation of the United States. Had
this data been seriously wrong, someone surely would have complained
by now. Satellites are insured against premature loss, and the
insurers want to make sure the spacecraft are engineered to the best
possible standards. There is immense worldwide economic incentive to
having the best available data on the Van Allen belts, so it's highly
improbable the the U.S. has been intentionally providing erroneous
data to the entire world for thirty years.
An orbital nuclear
detonation in 1962 code-named Starfish Prime created a third Van Allen
belt composed of high-energy electrons. This belt was a hundred times
more intense than the existing Van Allen belts and was computed to
have a half-life of 20 years. [Bennett and Percy, Dark Moon,
The authors give no reference for the claim that this artificial
radiation belt was "a hundred times" more "intense" than the
naturally-occurring belts. Nor do they define what is meant by
"intense". The Starfish Prime test did in fact produce a temporary
artificial radiation belt, and it's true that this belt persisted
longer than anticipated. But it was not an impediment to the Apollo
missions because it had dissipated to a safe level by then, and was
very small (and easily avoided) to start with.
Fig. 1 - The aurora produced by the Starfish Prime
high-altitude nuclear detonation.
Radioactive half-life applies to radioisotopes only. It does not
apply to clouds of magnetically-retained charged particles. The
authors imply that their theory is confirmed by expert authors, but in
fact the author they cite discusses only the general concept of
radioactive half-life. Bennett and Percy are responsible for having
misapplied it to this problem. Radioactive half-life and particle
belts have nothing at all to do with each other. The dispersal of
this belt doesn't have anything to do with radioactive decay, and a
great deal to do with solar weather and shifting magnetic fields.
The authors argue that such a radiation belt would still be highly
intense to this day. However they have shown no evidence that any of
the radiation from Starfish Prime is still there. Instead they refer
to irrelevant scientific principles and claim it "must" still be there.
A secret study done by
the Soviet Union and obtained by the CIA determined that a meter of
lead would be required to shield against deep space
Many conspiracists allude to this alleged report, but none of them
can attest to actually having seen it. Since they can argue the
alleged report is closely held by the CIA and therefore still top
secret, the conspiracists are protected from refutation. No one can
prove the non-existence of any document, much less one that is
allegedly classified by an intelligence agency. Unfortunately it's
more straightforward to note that the conspiracists cannot expect the
world to accept an argument based on evidence which they cannot
produce. If it's so top secret, how do they know about it?
It's fairly easy to show that such a document likely does not
exist. We know that great thicknesses of lead are not required to
shield against particle radiation. We know that Soviet science and
engineering were excellent. We note with no small amusement and no
small suspicion that the conclusion of the alleged report contradicts
the commonly accepted principles of physics, and that it instead bears
a striking resemblance to the naive assertions of inexpert conspiracy
theorists who claim that only thick sheets of lead are suitable for
radiation shielding. The alleged report is plausible to the lay
reader but utterly unconvincing to the scientist.
History provides the final proof. Had the Soviets actually
believed that great thicknesses of material were required to shield
against radiation, they would have questioned the design of the Apollo
spacecraft. The spacecraft clearly did not provide a meter of lead
shielding, yet NASA claims it successfully traversed the Van Allen
belts. Yet the Soviets acknowledged then and continue to acknowledge
today that the Apollo program was a clear success.
The Soviet lunar spacecraft design demonstrates they did not
believe a meter or two of lead was required to shield against
In recent years the Western world has been able to examine the
Soviet spacecraft design which was to have carried cosmonauts to the
moon. They did not provide a meter of lead for their spacecraft
Soviet cosmonauts have
been quoted as saying radiation was a very grave concern.
And NASA officials have been quoted as saying essentially the same
thing. Radiation is a very great concern, but there's a vast
difference between a "concern" and an insurmountable obstacle. The
conspiracist argument relies on the radiation problem being
insurmountable, and nothing said by either NASA or cosmonauts conveys
the notion that these problems couldn't have been solved.