Scott Kelly and space radiation

[Greg Bernhardt]

Today on NPR "On Point" the program was discussing the Scott Kelly mission. One of the experts said one important thing to investigate is what radiation he received and how it will effect his body. My question is, isn't that fairly easy to measure? What kinds of radiation mitigation could there be that isn't already there?

 

[mfb]

High-energetic gamma radiation is easy to measure. The distribution and secondary radiation in the body is harder to quantify, a dosimeter doesn't capture that.
The hull of the ISS provides some shielding against radiation, with different levels at different modules. In addition, there are medical ways to reduce the effect of radiation doses - but the lack of statistics at low dose rates makes studies of those effects tricky.

 

[Andy Resnick]

Today on NPR "On Point" the program was discussing the Scott Kelly mission. One of the experts said one important thing to investigate is what radiation he received and how it will effect his body. My question is, isn't that fairly easy to measure? What kinds of radiation mitigation could there be that isn't already there?

Good question- an astronauts' flight status is ultimately limited by the cumulative radiation dose, set by NASA to 400 rem (the annual safe exposure limit is 50 rem/yr)

https://www.nde-ed.org/EducationResources/CommunityCollege/RadiationSafety/safe_use/exposure.htm

Early models of the ISS interior indicated that the radiation dose would be on the edge of those limits, a 180-day mission was estimated to expose a crew member to 30 rem, and the interior of MIR was measured to provide a total absorbed dose rate measured was 411.3±4.41 uGy/day with an average quality factor (QF) of 2.44, or about 0.1 rem/day:

https://www.google.com/url?sa=t&rct...yFTDhewGJWs6w87XQ&sig2=tqSG0xzDdYKYQEIH_m2_qQ

On the other hand, I found a reference that measured the 6-month ISS dose at 7.2 rem, which would seem to indicate Scott Kelly remains well within safety limits.

http://www.bioone.org/doi/10.1667/RR1330.1

 

[1oldman2]

Just noted Scotts retirement today, is this related to accumulative radiation exposure in anyway? I haven't heard a particular reason for retiring.

 

[mfb]

I haven't heard a particular reason for retiring.

So why do you ask particularly about radiation dose? Why not about dozens of other potential reasons?

 

[1oldman2]

So why do you ask particularly about radiation dose? Why not about dozens of other potential reasons?

In answering your question the truth is I mentioned radiation exposure as that is one of the more common threats I see highlighted regarding space flight (long term in particular), I'm somewhat akin to a moth and will generally gravitate towards the brightest flame, (I hope the analogy is appropriate in this case).
While I'm not to be confused with a technical person on these matters I do follow most space programs with a certain degree of fanaticism, particularly the ISS missions. I'm aware of many of the long term hazards, Radiation, fluid shifting, bone loss, etc. however only from the average layperson point of view.
At the risk of "showing my poker hand" in a site full of statisticians (sorry I love analogy/metaphor) my question was targeted with the specific reason that I really don't know the particulars on Mr. Kelly's retirement, Thus I'm hoping people on this site with information I don't have would add to my knowledge.
I "liked" your response as it was not only an excellent question to raise considering my narrowly phrased post, but hopefully will also bring out others whom have info on the subject. I'm not particularly concerned if the retirement reasons turn out to be some banal thing such as he just wanted to retire, however if it was related to Extended space flight time then I would be very interested in the reasons. Thanks for taking the time to consider my post and I will be following the thread very closely in hopes of gleaning anything I can about these matters.

 

[mfb]

Launches and landings are more dangerous (18 deaths so far, out of a few hundred people that went to space). Also, there are many places around the world where you get much more radiation from natural sources than an astronaut gets over the course over a human lifetime.

 

[1oldman2]

Still not finding much on retirement of S. Kelly, just the same news releases, all identical. (only exception would be an LA times piece mentioning his possible involvement with private space contractors).
Almost like a NASA embargo on reason for retirement.

 

[mfb]

Or it is just his private decision and not our business?

 

[1oldman2]

Or it is just his private decision?

As much a possibility as any other at this point, I'm just waiting to hear more from him than the news release everyone copies.
The LA times piece is the first new thing I have come across, It seems to hint he's not done with space. Like everything else time will tell.
The LA times quotes him as saying his odds of flight rotation are slim with all the time he has accumulated, so things are leaning toward your "personal decision" theory. As I was saying personal decisions would have little interest to me, it's the Space flight hazards aspect that I follow.

 

[mfb]

As I said above, spaceflight is dangerous, but (in low Earth orbit) not due to radiation. There are many jobs and even hobbies that involve much more dangerous activities.