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posted by martyb on Thursday October 19 2017, @04:12PM   Printer-friendly
from the impeding-Doom(tm) dept.

Phobos has been considered as a possible initial base for human exploration of Mars because its weak gravity makes it easier to land spacecraft, astronauts and supplies. The idea would be to have the astronauts control robots on the Martian surface from the moons of Mars, without the considerable time delay faced by Earth-based operators. "We found that astronauts or rovers could accumulate significant electric charges when traversing the night side of Phobos – the side facing Mars during the Martian day," said William Farrell of NASA's Goddard Space Flight Center, Greenbelt, Maryland. "While we don't expect these charges to be large enough to injure an astronaut, they are potentially large enough to affect sensitive equipment, so we would need to design spacesuits and equipment that minimizes any charging hazard." Farrell is lead author of a paper on this research published online Oct. 3 in Advances in Space Research.

[...] The solar wind is responsible for these charging effects. When the solar wind strikes the day side of Phobos, the plasma is absorbed by the surface. This creates a void on the night side of Phobos that the plasma flow is obstructed from directly entering. However, the composition of the wind – made of two types of electrically charged particles, namely ions and electrons – affects the flow. The electrons are over a thousand times lighter than the ions. "The electrons act like fighter jets – they are able to turn quickly around an obstacle -- and the ions are like big, heavy bombers – they change direction slowly," said Farrell. "This means the light electrons push in ahead of the heavy ions and the resulting electric field forces the ions into the plasma void behind Phobos, according to our models."

The study shows that this plasma void behind Phobos may create a situation where astronauts and rovers build up significant electric charges. For example, if astronauts were to walk across the night-side surface, friction could transfer charge from the dust and rock on the surface to their spacesuits. This dust and rock is a very poor conductor of electricity, so the charge can't flow back easily into the surface -- and charge starts to build up on the spacesuits. On the day side, the electrically conducting solar wind and solar ultraviolet radiation can remove the excess charge on the suit. But, on the night side, the ion and electron densities in the trailing plasma void are so low they cannot compensate or 'dissipate' the charge build-up. The team's calculations revealed that this static charge can reach ten thousand volts in some materials, like the Teflon suits used in the Apollo lunar missions. If the astronaut then touches something conductive, like a piece of equipment, this could release the charge, possibly similar to the discharge you get when you shuffle across a carpet and touch a metal door handle.

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  • (Score: 1, Interesting) by Anonymous Coward on Thursday October 19 2017, @05:19PM (3 children)

    by Anonymous Coward on Thursday October 19 2017, @05:19PM (#584675)

    Can we use that effect for supplying more electric power to our orbital stations then by using photovoltaic panels? Perhaps by using permanent magnets we can make separation of charges in solar wind flux and collect electric charge on separate plates of the apparatus.

    • (Score: 0) by Anonymous Coward on Thursday October 19 2017, @05:45PM (2 children)

      by Anonymous Coward on Thursday October 19 2017, @05:45PM (#584688)


      • (Score: 2) by DannyB on Thursday October 19 2017, @06:45PM (1 child)

        by DannyB (5839) Subscriber Badge on Thursday October 19 2017, @06:45PM (#584727)

        What about charging capacitors from potential differences in charge? Maybe you need a very long wire?

        • (Score: 2) by rylyeh on Thursday October 19 2017, @10:41PM

          by rylyeh (6726) <> on Thursday October 19 2017, @10:41PM (#584956)

          Without a grounding mechanism seems like charging a capacitor or battery would be required.
          Tethers into the surface seem impractical.

          O friend and companion of night, thou who rejoicest in the baying of dogs {here a hideous howl burst forth}...
  • (Score: 2) by takyon on Thursday October 19 2017, @05:25PM (2 children)

    by takyon (881) Subscriber Badge <> on Thursday October 19 2017, @05:25PM (#584681) Journal []

    Phobos has also been proposed as an early target for a manned mission to Mars because a landing on Phobos would be considerably less difficult and expensive than a landing on the surface of Mars itself. A lander bound for Mars would need to be capable of atmospheric entry and subsequent return to orbit, without any support facilities (a capacity that has never been attempted in a manned spacecraft), or would require the creation of support facilities in-situ (a "colony or bust" mission); a lander intended for Phobos could be based on equipment designed for lunar and asteroid landings.[99] Additionally, the delta-v to land on Phobos and return is only 80% of that for a trip to and from the surface of the Moon, partly due to Phobos's very weak gravity.[100][full citation needed]

    At the least, we should send a robotic lander there. Preferably one that can handle this charged dust.

    [SIG] 10/28/2017: Soylent Upgrade v14 []
    • (Score: 0) by Anonymous Coward on Friday October 20 2017, @08:44AM (1 child)

      by Anonymous Coward on Friday October 20 2017, @08:44AM (#585147)

      What's the point? OK, landing humans on Phobos is easier, but then again, crossing the orbit gap from Phobos to Mars would still be a hard problem. The only thing justifying it would be to bring humans which remotely operate Mars ROVs closer to them, to shorten time lag in control loop.

      • (Score: 2) by takyon on Friday October 20 2017, @09:29AM

        by takyon (881) Subscriber Badge <> on Friday October 20 2017, @09:29AM (#585152) Journal

        What has NASA committed to doing at Mars in the 2030s? A manned landing? Nope, a manned orbit: []

        Finally, we become Earth Independent, building on what we've learned on the space station and in deep space to send humans to low-Mars orbit in the early 2030s.

        Seems to be based on this plan: []

        Instead of landing on the first go, NASA could lay out a series of missions that use existing programs, strategically build experience and capability, and spread out cost. The orbit-first concept would send astronauts near the Moon throughout the 2020s, to Mars orbit and Phobos in 2033, and finally to the surface of Mars by 2039 to begin an ongoing program of exploration. []

        The Deep Space Transport (DST) is a spacecraft meant to be launched on top of NASA's SLS launch vehicle in 2027. It was announced by NASA in March 2017. Plans at present predict it to dock with the Deep Space Gateway (DSG) station, which would be in cis-lunar space after its construction from 2021 to 2026 as a manned lunar space station, the first of its kind, in 2027. Current plans show it to be sent with a crew of 4 to Mars in 2033. It would not, however, land, but merely remain in Martian orbit until there is a launch window for a return. The mission is expected to take about 2 years if all missions in the DSG and DST from 2021-2030 are successful. This mission would use only the SLS rocket for launches, with the Orion MPCV to be used as a spacecraft to transport the crew to and from the Earth and the DSG and DST.

        Now, overseas or SpaceX developments might cause NASA to change their plans, but that's what's on the agenda right now. A manned orbit of Mars (no landing) around 2033. Landing possible later but no target date stated.

        A Phobos orbit or landing should be no worse than a Mars orbit. You could do some surface science there, hopefully without being zapped. Although it would make NASA the butt of many jokes if the U.S. became the first to land on Phobos while another country became the first to land on Mars.

        If SpaceX, ULA, Blue Origin, Lockheed Martin, or someone else can beat the Space Launch System to death, maybe we can get a landing by 2035 instead.

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