So, I was sitting at the sixteenth conference on Solid State Dosimetry (SSD16) in Sydney, thinking about monkeys, radiation and space exploration. Dosimetry is the science of the absorbed dose of ionizing radiation in matter and tissue.
The main purpose of the conference involves neither monkeys nor space exploration. Most of the dosimeter work is focused on medical applications, to advance the state of the art for more precise radiation treatment of cancer patients. But the part I am involved with specifically deals with space exploration applications.
Radiation is the single biggest threat to astronaut health in long duration flight. This is especially true for flights that would occur away from the Van Allen Radiation Belts, which offer significant protection to all of us, safely cocooned in its warm embrace down here on the Earth's surface.
Even in Low Earth Orbit (LEO), astronauts are still protected to a large degree from charged particles. The heavy artillery still gets through (gamma rays, neutrons, some protons), but the electrons and other charged ions are caught in the Earth's geomagnetic field. Astronauts who ventured to the moon were outside of the belts, as would be astronauts who travel to Near Earth Objects (NEOs), Lagrange Points or any other far-off destination (Mars, anyone?). In this case, the radiation from a surprise solar flare could be fatal. NASA worried quite a bit about that possibility during the Apollo program in the 1960's and 70's.
It was announced in the morning's conference session that the previous night we had a solar event. I immediately thought of my friends aboard the International Space Station (ISS); they were a day late to return to Earth, and could be exposed to elevated radiation levels.
We had a solar event during my stint as the Commander of ISS Expedition 10. It was eerie. We got the call from Mission Control, and were advised during specific times when we were to retreat to the "more heavily shielded" portions of the station. More heavily shielded? Uh huh.
For me, that meant the sleep station in the US Segment, which had plastic shielding inserted into the fabric walls. They are supposed to catch a few heavy particles, but they still seemed awfully thin to me.
Flight Engineer Salizhan Sharipov was directed to the middle of the Russian Zvezda core module, where there was more machinery around the middle. After the event had passed, radiation detectors were still registering levels of about ten times above "normal." Great.
Well, what could we do? This was one of the prices we had to pay for the privilege of spaceflight. At least we had detectors, which allowed estimates of the cumulative doses that we received (we were told our health was "all good!" post-flight by the NASA folks).
There are three things we need to figure out radiation-wise in order to explore in a sustained fashion beyond LEO: (1) Detection; (2) Shielding; (3) Treatment.
The Solid State Dosimetry conference deals with the first: detection. There is ongoing work in the other two fields as well.
Shielding is a tricky deal. It would seem that one would simply need to find a pile of lead and hide inside of it. Not so simple. Gamma rays and protons punch into tough material like lead and cause energetic secondary emissions that can be much more harmful to biological entities like us. As for treatment, there are researchers working on drugs and nano-materials that would scoop up free radicals in our blood caused by radiation exposure. Good work in all three, but plenty more to do.
So, where do the monkeys come in? Monkeys and chimpanzees have played an important role in space exploration since the beginning of the Space Age. The first "American" in space was Ham the Chimp, who flew inside of a Mercury capsule before Alan Shepard.
You may have heard about planned monkey radiation experiments, and the recent protests against them. I understand the necessity of animal experiments in developing drugs and treatments, but I must admit that this one has me scratching my head a bit.
I have no doubt that some advances in scientific knowledge would be realized through these planned experiments, but I'm an operational guy (despite my Ph.D.). How would these experiments help us to survive in deep space? I don’t see it. The bottom line is that exposure to high levels of radiation is bad. We need to figure out how to detect, and protect against exposure as well as to treat if exposure occurs.
I'm a big fan of Curious George. Let's leave him alone this time.
Leroy Chiao served as a NASA astronaut from 1990-2005. During his 15-year career, he flew four missions into space, three times on space shuttles and once as the copilot of a Russian Soyuz spacecraft to the International Space Station. On that flight, he served as the commander of Expedition 10, a six-and-a-half-month mission. Dr. Chiao has performed six spacewalks, in both U.S. and Russian spacesuits, and has logged nearly 230 days in space. He was a member of the Review of U.S. Human Spaceflight Plans Committee, and is currently an Executive Vice President of Excaibur Almaz, a private commercial space venture.