Tag Archives: interplanetary travel

Cosmic rays a threat to Mars travel

The uncertainty of science: New research using rats has found that cosmic rays might damage human brains during a long mission to and from Mars.

Radiation oncologist Charles Limoli and his colleagues at the University of California Irvine bombarded mice and rats with low-doses of ionized oxygen or titanium. These charged particles have similar energies to those of cosmic rays that can pass right through the shielding on spacecraft. The dosage levels that the researchers used were similar to what astronauts would be exposed to during a three-year round-trip mission to Mars, Limoli says.

The researchers looked at the prefrontal cortex, the brain region linked to decision-making, executive function, and long-term memory. They saw significant damage and inflammation in the brains of exposed animals as long as six months after the exposure. The radiation damaged the tiny branches on neurons that help transmit electric signals to the nerve cell body. This led to a loss in learning and memory. The exposed animals performed poorly on behavioral tests that measure intelligence, and they showed higher, constant anxiety levels.

Though the uncertainties here are enormous, the research here has essentially discovered the obvious. The radiation experienced during a long interplanetary voyage is unhealthy, and any interplanetary vessel for carrying humans on such a voyage must be designed with sufficient shielding to protect its passengers. That this research has proven that cosmic rays are a threat also means that providing a ship with a safe room where passengers can take refuge during solar storms is not sufficient. Cosmic rays are random and come at all times in an unpredictable manner. The research suggests that the shielding will have to protect the ship’s entire living quarters.

The payload weight requirements for any rocket that will launch the first interplanetary ships just went up significantly. This means that space stations we have been building (Mir, ISS, and Tiangong) are not even close to sufficient for interplanetary travel, and need significant redesign to make them work. This also means that human interplanetary travel will require cost-efficient heavy lift rockets such as the Falcon Heavy.

First 3D part manufactured in space

Astronauts on ISS have used a 3D printer, shipped to the station on the last Dragon flight, to print the first item ever manufactured in space.

“Everything worked exactly as planned, maybe a little better than planned,” Kemmer told NBC News. He said only two calibration passes were needed in advance of the first honest-to-goodness print job, which finished up at 4:28 p.m. ET Monday and was pulled out of the box early Tuesday. “It’s not only the first part printed in space, it’s really the first object truly manufactured off planet Earth,” Kemmer said. “Where there was not an object before, we essentially ‘teleported’ an object by sending the bits and having it made on the printer. It’s a big milestone, not only for NASA and Made In Space, but for humanity as a whole.”

The part made was a faceplate for the printer itself. This printer is a demonstration project, launched to test the engineering and to see how 3D printing operates in weightlessness. Eventually the goal is to have most of the spare parts on a interplanetary vehicle manufactured in space in this manner, using a supply of standard material, called feedstock, that would be much cheaper to ship from Earth.

ISS data lowers radiation risk for humans in space

Good news: Data collected on ISS for the past decade now suggests that the human body does a better job of shielding its internal organs from space radiation than previously believed.

For an astronaut working inside the space station, the overestimate was about 15 percent — a fairly close correlation given that the station’s exterior shell provides much of the protection needed.

But for astronauts working outside the station, the radiation absorption measured was substantially less than what had been registered by the personal dosimeters worn by astronauts. “Measurements of a personal dosimeter dramatically overstate the exposure of an astronaut, in the worst case by a factor of three,” according to a summary of the results by a Euro-Russian team. “[I]n an outside exposure the self-shielding of the human body is very effective. … [T]he effective dose equivalent is less than 30 percent higher than in an inside exposure.”

In other words, humans could fly 30 percent longer in space with the present shielding and suffer far less exposure than expected. Though this data is for operations in low Earth orbit, it still provides a strong counter to the bad news recently released about the high amounts of dangerous radiation expected in interplanetary space due to the Sun’s recent low sunspot activity. Even if radiation levels are higher, the human body is more resilient than expected. Interplanetary space travel is still possible.

Solar minimum to limit interplanetary manned flights?

A new study suggests that the increased cosmic radiation reaching the inner solar system because of the Sun’s weak sunspot activity will increase the exposure to dangerous radiation levels for interplanetary astronauts, thus limiting mission lengths to about one year.

The new research finds that, during periods of low solar activity, a 30-year-old astronaut can spend roughly one year in space—just enough time to get to Mars and back—before the constant bombardment by cosmic rays pushes the risk of radiation-induced cancer above current exposure limits.

If the sun’s activity continues to weaken as many scientists predict, the number of days humans could spend in deep space before reaching their exposure limit could decrease by about 20 percent, making future crewed space flight more dangerous, according to the new study accepted for publication in Space Weather, a journal of the American Geophysical Union.

The numbers were worse for women, whose exposure would become dangerous in only 300 days, according to the study.

Data from an experiment on Lunar Reconnaissance Orbiter has confirmed that light plastics can provide sufficient protection for humans against radiation.

Data from an experiment on Lunar Reconnaissance Orbiter has confirmed that light plastics can provide sufficient protection for humans against radiation.

This is very good news indeed. Combined with the data from Curiosity, which indicated that the radiation levels in interplanetary space were less intense that expected, it appears that radiation will not be a serious obstacle to interplanetary travel.

Now we just have to get the bone loss and vision problems solved.

The dangerous environment of space

A just released report from the National Academies, Preparing for the High Frontier: the role and training of NASA astronauts in the post-space shuttle era, describes the challenges that NASA faces in staffing its astronaut corps in the coming years. More important, however, is some new information buried in the report about the hazards of long term exposure to weightlessness.

For example, it seems a significant number of astronauts have come back from spending months at ISS with serious vision problems, caused by a newly discovered condition dubbed papilledema, the swelling of the optic disk.
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