Artist's rendering of the Multi-Purpose Crew Vehicle on a deep space mission.
Image: NASA
High radiation levels beyond Earth orbit pose the biggest challenge to human exploration of deep-space destinations, experts say.
With current spacecraft technology, astronauts can cruise through deep space for a maximum of one year or so before accumulating a dangerously high radiation dose, researchers say. As a result, many intriguing solar system targets remain off-limits to human exploration at the moment.
"There is an equivalent of a Mach 1 — a sound barrier — that exists, in terms of galactic cosmic radiation," Alvin Drew, manager of NASA's Deep Space Habitat Project, said Wednesday (Dec. 19) during a presentation with the agency's Future In-Space Operations working group.
"Until we solve that, we are still in the age of wooden ships and canvas sail for going out in space," added Drew, an astronaut who has flown on two space shuttle missions. "Until we get to a point where we are looking at steam engines and ships of iron, we may be very limited in how far we can go." [Future Visions of Human Spaceflight]
One-year limit
Earth is pummeled relentlessly by galactic cosmic rays — fast-moving charged particles blasted into space by distant star explosions and other dramatic events.
The planet's atmosphere and magnetic field deflect most of these subatomic wrecking balls, so those of us on Earth's surface don't worry too much about them.
But for astronauts cruising through space — especially deep space, beyond Earth's protective magnetosphere — it's a different story. They can endure this radiation for only a limited time before serious problems such as cancer begin cropping up.
"Until we get new technologies or new ways to mitigate against cancer-induced deaths," Drew said, "we're going to be limited to about one year in space."
The sun also routinely ejects particles that can damage human tissue, and researchers are currently working on ways to shield astronauts from such solar outbursts. But whatever measures they devise may not be terribly effective against cosmic rays, which have much higher energies, Drew said.
"Galactic cosmic radiation is like a low-rate gunfire that comes through — you don't get hit very often, but when you do, it does a lot of damage," Drew said. "And that's why we need to go out and figure out how to protect ourselves against these very high-energy, somewhat massive subatomic particles coming in from our galactic core."
Mars mission still possible
A one-year spaceflight cap would still allow manned missions to some intriguing destinations, such as Mars.
In fact, data gathered by NASA's Curiosity rover — which landed on the Red Planet this past August — suggest that astronauts could endure a six-month outbound flight, a 600-day stay on the Martian surface and the six-month journey home without accumulating a worryingly high radiation dose.
That's good news for NASA, which is working toward sending astronauts to a near-Earth asteroid by 2025, then on to the vicinity of the Red Planet by the mid-2030s. Part of this preparation involves studying the psychological and physiological effects of long-term spaceflight, which the agency will investigate on one-year missions to the International Space Station beginnning in 2015. (The standard stay for astronauts aboard the orbiting lab has been six months.)
But if humanity wants to venture much farther afield — say, to Jupiter's ocean-harboring moon Europa — advances in spacecraft shielding and/or propulsion systems will almost certainly be necessary.
- Photos: NASA's Space Launch System for Deep Space Flights
- Giant Leaps: Top Milestones of Human Spaceflight
- NASA's Huge Mars Rover Curiosity: 11 Amazing Facts
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9 Comments
Add Comment"That's good news for NASA, which is working toward sending astronauts to a near-Earth asteroid by 2025, then on to the vicinity of the Red Planet by the mid-2030s.'
Reply | Report Abuse | Link to thisWTF. Not according to Congress or NASA's own internal reports. There is a statement of mission but no 'plan'. there hasn't been funding for essential parts of the asteroid mission and those technologies should be underway by now. The plan essentially is 'we don't have a plan and we don't have funding'.
Please read this book: "Radiation and Reason, The impact of Science on a culture of fear" by Wade Allison.
Reply | Report Abuse | Link to thishttp://www.radiationandreason.com/
Professor Allison says we can take up to 10 rems per month, a little more than 1000 times the present "legal" limit. The old limit was 5 rems/lifetime. A single dose of 800 rems could kill you, but if you have time to recover between doses of 10 rems, no problem. It is like donating blood: You see "4 gallon donor" stickers on cars. You know they didn't give 4 gallons all at once. There is a threshold just over 10 rems. You are getting .35 rems/year NATURAL background radiation right where you are right now.
Divide 5 rems by your present Natural Background Radiation. For Americans, Natural Background Radiation is at least .35 rems/year. Our Natural Background Radiation uses up our 5 rems/lifetime when we are 14 years old.
Natural Background Radiation is radiation that was always there, 1000 years ago, a million years ago, etc. Natural Background Radiation comes from the rocks in the ground and from exploding stars thousands of light years away. All rocks contain uranium. Radon gas is a decay product of uranium.
Background radiation varies greatly. Even when it's natural, it's always dangerous.
Reply | Report Abuse | Link to this- Radon is a radioactive gas released from the normal decay of the elements uranium, thorium, and radium in rocks and soil.
- Radioactive particles from radon can damage cells that line the lungs and lead to lung cancer.
- Radon is the second leading cause of lung cancer in the United States and is associated with 15,000 to 22,000 lung cancer deaths each year.
- Testing is the only way to know if your home has elevated radon levels. Health authorities recommend radon testing and encourage corrective action when necessary.
http://www.cancer.gov/cancertopics/factsheet/Risk/radon
There is reason to be concerned about the accumulated effects of radiation over your lifetime - while the body attempts to repair DNA damage the process is not perfect. As you indicate it's also limited, which means that if the rate of damage exceeds the maximum rate of repair damaging effect accumulate rapidly.
Radiation exposure is, in almost all cases, not a good thing. Perhaps your interest in mining asteroids has biased your risk assessment...
"..Even when it's natural, it's always dangerous.."
Reply | Report Abuse | Link to thisUh, nope, there is NO as in ZERO evidence that background radiation causes harm, indeed there is evidence of the contrary.
"..radon can damage cells that line the lungs and lead to lung cancer.."
The amount of damage is MILLIONS of times lower than spontaneous rate of mutation, for any normal levels of radiation - even very high levels found in some areas such as Ramsar, Iran which has lower incidence of cancer.
"..Radon is the second leading cause of lung cancer.."
Bull. This is based on an EPA study using increased lung cancer risk of Uranium miners and extrapolating using the proven false LNT theory of Radiation Health effects. Unfortunately the study failed to take into account the high smoking rate amongst miners and the fact they breath diesel exhaust and lubricating oil while working.
Actual studies comparing Radon exposure and Lung Cancer show a NEGATIVE Correlation. i.e. Radon exposure induces increased cancer resistance, see the graphs on the last page of:
www.phyast.pitt.edu/~blc/LNT-1995.PDF
atomicinsights.com/wp-content/uploads/Cuttler-2012_ANS-President-Session_Jun23-copy.pdf
"...Radiation-induced: 10-100 DNA alterations per cell/cGy 1 mGy/year radiation 6 million times lower than spontaneous rate!!!
So radiation is not a significant cause of cancer. We've known this for more than 20 years!.."
"..Low radiation dose/dose-rate reduces cancer incidence because it stimulates:
-- prevention of DNA damage
-- repair of DNA damage
-- removal of damaged cells and removal of cancer cells
High radiation dose/level has opposite effects.."
Radiation therapy enables miracle cure for untreatable melanoma, actually stimulates the immune system to fight and destroy cancer throughout the body, even though only one tumor was irradiated:
maximumnewsinformer.com/?p=6202
"...Radiation's principal effect is on the defenses. Low radiation doses/levels stimulate all the defenses reducing the incidence of cancer...While radiation alters DNA, this effect is usually small compared to the spontaneous rate of DNA alterations ..Wade Allison points out that radiation treatments of tumors and post-surgical follow-up radiation treatments irradiate large amounts of healthy tissue (organs too) at 200 rad each day for 4 weeks. That amounts to 200 x 5 x 4 = 4000rad[40Sv] in a month. [23,000X Fukushima district maximum allowed]. There are many cells in this healthy tissue (10^9 per gram), and Allison says that these tissues recover. These irradiated areas do not become cancer ridden..."
As I said, cellular repair of DNA damage is imperfect.
Reply | Report Abuse | Link to thisMelanoma and other, less severe skin cancers are produced by repeated exposure to natural, low doses of UV radiation, especially in lighter skinned people. Tanning beds are another issue...
That focused radiation is used to kill cancer cells is indisputable evidence of it ability to kill cells. Healthy cells that 'recover' from incidental exposure as a result of intense, directed beam treatment of tumors may also suffer long term damage, but then many of those whose cancer is treated with radiation do not survive long term.
As for the subject of this article, space travel and continual exposure to cosmic radiation, it states:
"But for astronauts cruising through space — especially deep space, beyond Earth's protective magnetosphere — it's a different story. They can endure this radiation for only a limited time before serious problems such as cancer begin cropping up."
As I understand, high energy cosmic rays routinely pass completely through spacecraft and any occupants, damaging not just a few cells but all the cells in their path. BTW, cosmic radiation is natural...
UV radiation is non-ionizing radiation, so the mechanism that it causes cancer is quite different from ionizing radiation. And the amount of radiation we get from the sun is orders of magnitude greater than what we get from background radiation, radon or Fukushima district. And nobody said there was a distinction between "natural" and "artificial" radiation. So I don't know why you brought that up. The point was natural background ionizing radiation HAS NOT been shown to be harmful, that is in normal human environments here on Earth. You are being absurd if you extend that to the MUCH HIGHER "background" radiation in space.
Reply | Report Abuse | Link to thisAnd undoubtedly the much higher radiation levels in space can cause acute radiation sickness or cancer, as the articles I linked have demonstrated we can tolerate 3 mSv/day of ionizing radiation with no detectable increase in cancer or other adverse health effects. Much below that and favorable health benefits have been observed. Much above that and adverse health effects including cancer will occur. The articles clearly state that.
".. intense, directed beam treatment of tumors may also suffer long term damage.."
These are levels FAR, FAR above what cells receive from Radon in basements or in Fukushima district, and yet they don't become cancerous later in life. Once again, there is NO evidence that low dosage radiation such as found in nature or in Fukushima district is harmful, indeed the opposite is true.
"And nobody said there was a distinction between "natural" and "artificial" radiation."
Reply | Report Abuse | Link to thisOn the contrary, "Asteroid Miner" did state that "Natural Background Radiation is radiation that was always there, 1000 years ago, a million years ago, etc..." indicating that it is a 'normal' part of the environment...
You took specific exception to my remark to him about "Natural background radiation." and further argued that "Actual studies comparing Radon exposure and Lung Cancer show a NEGATIVE Correlation. i.e. Radon exposure induces increased cancer resistance."
"You are being absurd if you extend that to the MUCH HIGHER "background" radiation in space."
I'm merely referring back to the subject of this article, but I'm confident that it is you who are being absurd, arguing that radiation is good for peoples' health!
Yes, Asteroid Miner did correctly state "Natural Background Radiation is radiation that was always there" and is a normal part of the environment. So.
Reply | Report Abuse | Link to this"...arguing that radiation is good for peoples' health!.."
No it is you who is being absurd, arguing that removing all background radiation will improve health. That is false. And I showed you the evidence and statements from the World's foremost authorities on the subject. You have zero evidence to the contrary. Like many things in the natural environment in which terrestrial organisms have evolved there is an optimal level of exposure. My argument is the FACT that is also true for radiation. You are claiming it isn't. And you have NO evidence to back that up.
Perfect example is parasites & infectious disease exposure. It is well established that a too low level of exposure is harmful, and causes immune system dysfunction. According to your theory placing people in a bubble with no exposure to contagions would be optimal to health.
Cancer risk is lower in high radiation areas in Poland:
Reply | Report Abuse | Link to thisdose-response.metapress.com/app/home/contribution.asp?referrer=parent&backto=issue,9,15;journal,2,31;linkingpublicationresults,1:119866,1
"...The cancer mortality ratios (CMRs) in Poland in high and low level radiation areas were analyzed based on information from national cancer registry. Presented ecological study concerned six regions, extending from the largest administration areas (a group of voivodeships), to the smallest regions (single counties). The data show that the relative risk of cancer deaths is lower in the higher radiation level areas. The decrease by 1.17%/mSv/year (p = 0.02) of all cancer deaths and by 0.82%/mSv/year (p = 0.2) of lung cancers only are observed..."