James A. Van Allen - Dies at 91

Diamonddavej writes "The New York Times reports that the respected astrophysicist, James A. Van Allen, died yesterday at the age of 91. Apparently the fellow regularly worked at his office/laboratory up until a month ago. Prof. Van Allen team designed the Geiger counter that flew aboard Americas first orbiting satellite, Explorer 1. It detected unexpectedly intense levels of radiation caused by energetic particles trapped in the Earth magnetic field, the magnetosphere. The belts of radiation were mapped and characterised by later missions and were named the Van Allen belts in honour of their discoverer."

Comments

Man-Made Equivalent

[eldavojohn]

One of the most interesting things about the Van Allen belts is the man made equivalent that remained from nuclear tests in the atmosphere. As the Wikipedia article references, that's what was done in Starfish Prime:

While some of the energetic beta particles had followed of the earth's magnetic field and illuminated the sky, other high-energy electrons became trapped in man-made radiation belts around the earth. There was much uncertainty and debate about the composition, magnitude, and potential adverse effects from this trapped radiation after the detonation. The weaponeers became quite worried when three satellites in low earth orbit were disabled. These man-made radiation belts eventually crippled one-third of all satellites in low orbit. Seven satellites were destroyed as radiation knocked out their solar arrays or electronics, including the first commercial communication satellite ever, Telstar.

The full declassified documentation can be found here (PDF warning) and it's effects are listed here. If you want the summation of that report, we basically learned that "Strong electromagnetic signals were observed from the burst, as were significant magnetic field disturbances and earth currents."

Does setting off an atomic bomb in the atmosphere of your home planet sound like a bad idea to you? Sounds more like the threat of a Bond villain than an action of the United States government. I'm not sure what the motive was for these tests does anyone who knows Van Allen's research have an answer?

Re:Man-Made Equivalent

[stair69]

Though I'm not an expert on the high atmosphere testing that went on at that time from what I've read/heard there did seem to be some method to the madness of setting off nuclear bombs in near orbit.

I believe that the US military were experimenting with the idea of creating a (hopefully temporary) layer of trapped radiation in the upper atmosphere in order to destroy/disable ICBM missiles aimed at the USA. There were quite a number of tests leading up to Starfish Prime (particularly Operation Argus in the South Atlantic ). One of the key drivers from a military point of view for these tests was to observe the effect of the trapped radiation in the upper atmosphere on incoming dummy missles.

I don't think that the experiments led to any breakthroughs regarding ballistic missile defence, but there were some interesting discoveries in the science. The effects of EMP from high altitude nuclear detonations weren't fully expected in the first tests (EMP from low altitude tests had been observed before, but in mid altitude testing the EMP was negligable - so significant EMP effect was not expected from high level detonations). The scientists involved in the tests were surprised that Starfish and the other Johnston Island high atmosphere detonations disrupted communications and electronic equipment as much as they did. It turns out that there are two different mechanisms for generating EMP after a nuclear detonation - the one that takes effect at high altitude is the one that causes widespread damage, whereas the low altitude one causes local damage to electronics, but no widespread damage.

Additionally data regarding the Van Allen belts, trapped radiation from man-made detonations and SAMA (the South Atlantic Magnetic Anomaly ) came in large part from the Starfish Prime and Argus experiments.

Today the idea of setting off nuclear bombs in the atmosphere, let alone in the high atmosphere, seems crazy, but these experiments (along with the experiments done by the other countries involved) should be viewed in the context of the era. In the late 50s and early 60s when these tests were performed by the US the fear of nuclear attack was reaching a peak. Experiments of this sort were tolerated because of the potential benefit that could be had by the side carrying them out. If, for example, the US military had found a way to disable ICBMs with high level detonations of nuclear bombs they could have disabled most of the threat to the USA in one stroke. As it was the US military discovered that high altitude detonations caused a long range EMP effect, and that knowledge allowed them to adjust their strategy for nuclear attack/defence.

For anyone who's interesting in seeing more about these exeriments I would certainly recommend the film The Rainbow Bombs by Peter Kuran. His other films Trinity & Beyond and Atomic Journeys are excellent as well.

Good week for conspiracy theorists.

[Lord Kano]

NASA looses the tapes of the moon landing and Mr. Van Allen passes away. If I remember correctly the Van Allen belts figure prominently in several anti-moon landing conspiracy theories.

Gentlemen, let the speculation begin!

LK

Re:Will be remembered for two things

[susano_otter]

Actually, NASA tapped Van Allen to spearhead further research into the belts he had discovered. The result of his further research was the conclusion that organisms could in fact safely traverse the belts. His research was a critical source of information for determining the velocities and trajectories necessary for such safe traversal.

So while it's true that he initially believe the belts would be impassable, his opinion changed as a result of his own careful study of the belts.

Van Allen's Rockoons

[kthejoker]

The belt and NASA made him famous, but James was doing some crazy stuff with rockets way back when, including the Rockoons, which were rockets launched from high-altitude balloons to gather information, test flight and fuel capacities, etc.

The Coast Guard let him shoot the Rockoons off the coast towards Greenland. When he first tried them, the rockets refused to fire. So Van Allen took some cans of orange juice, heated them, put them in the gondola next to the rocket, and covered them in insulation.

Presto. The rockets fired.

The definition of a great and honorable scientist; inquisitive, intuitive, unpretentious, and brilliant.

The man

[ivarneli]

I worked on the same floor as Van Allen at the University of Iowa when I was an undergraduate. He was quite an amazing guy - even at 90 years old, he still came to his office nearly every day to work on data from Pioneer. I had a number of conversations with him, and he clearly still loved what he was doing.

My fondest memory of him is when he was presented with an award at Iowa a few years back. The actual award was a glass globe with some intricate internal designs composed of another material. However, the globe was much heavier than it appeared. So he spent the next few minutes explaining to those around him how we could figure out its density using size and mass, and then figure out the internal composition based on that. Then he actually went through the rough calculation and narrowed it down to two or three likely materials. He was well known around the Physics department for his skills as an educator, and I'm glad that I was able to witness a bit of that firsthand.

Up until a few years ago he was still using an ancient punchcard-based programmable calculator for most of his computations. Van obviously new it was out of date, but he had so much experience with it that he could still use it fairly quickly. He showed me the array of cards he had written over the years for doing things like converting RA/Dec to Az/Alt and performing Newton's method. Around this time, a professor of mine started to teach Van how to use modern programs like Mathcad for doing things like this, and he was very excited and receptive to working in a way that was fairly new to him.

I know a lot of people who really admired this man, and he's really going to be missed up on the 7th floor.

Re:Will be remembered for two things

[sharp-bang]

Much of his advocacy against manned space exploration stemmed from the political reality that the budget for unmanned scientific missions was repeatedly gutted to pay for manned missions of negligible scientific value. This was certainly the case in the Reagan eighties.

He also publicly argued, less than a year before the Challenger disaster, that a catastrophic failure of the shuttle was inevitable due to its complexity. As I recall, he was pretty much alone in this at the time. I also recall that the Challenger mission was, in terms of numeric order for all shuttle flights, fairly close to the mean failure rate he calculated.

Ironically, the parent post and much of this thread neglect the third thing he should be remembered for: he was the godfather of the US space program. The International Geophysical Year international research effort, which began in his living room in 1950, was the key catalyst for obtaining governmental support for space science and led to pretty much everything else that NASA has ever done. Without him, space science might well have been sidlined in favor of militarization instead.