Why we abandoned space exploration in favor of dwelling in dark ages?

Discussion in 'Science & Society' started by Plazma Inferno!, Dec 4, 2015.

  1. billvon Valued Senior Member

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    Nor do the laws of physics prevent interstellar travel. It just takes a long time.
    It was well known that people would never be able to travel faster than sound because of the control reversal that occurred at transonic speeds. You can't change that. (At least according to them.)
     
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  3. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    For robots, yes, but not for humans until suspended animation is perfected with decades of duration, not to dwell on the energy problems (space temperature is lower than -250 C) and radiation shielding / limits.
     
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  5. billvon Valued Senior Member

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    If we have the energy to accelerate to even reasonable interstellar speeds (~.1C) the additional energy required for maintaining temperatures will be insignificant.

    We've been through the radiation issue before.
     
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  7. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Are suggesting that we reach ~0.1C at the half way point then turn ship 180 degree to slow down for second half of trip, which has average speed of 0.05C; or that we have reached that speed much earlier so transit time in not measured in centuries, and use energy for heating mainly most of the trip, while "coasting" at constant speed?

    Is there a nuclear reactor on the ship? If so, how is it cooled? (Typically 2/3 of the fission energy is heat dumped into a river, lake, or evaporative cooling tower, 1/3 is in electric power, via the steam engine/ turbin unit.)

    If not in suspended animation, what does the crew eat?
    Yes we have and NASA is still considering how to solve that problem, with no solution in sight for even only 780 days (the synodic period between Earth and Mars alignments) but the total time from earth, exposed to solar flares & cosmic radiation is much longer (>1000 days):
    "According to NASA, a vessel with humans on it would take roughly six months to travel to Mars and another six months to travel back from Mars. In addition, astronauts would have to stay 18-20 months on Mars before the planets re-align for a return trip."
    Quote from: https://www.google.com/?gws_rd=cr&ei=nNoOV6jvF4G7wASky4aADQ&fg=1#q=transit time earth to mars
     
    Last edited: Apr 14, 2016
  8. billvon Valued Senior Member

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    Talking an average speed of about .1C, so max of about .2C.
    You're assuming a Carnot cycle. To reach the power levels we are talking about you are going to need either direct utilization of fusion/annihilation products as reaction material or a direct conversion cycle (like D-HE3 fusion). Or power from an outside source.
    Food from an almost-closed-cycle ecology. Such trips will take decades, and as such will need almost 100% efficient recycling. Again, energy will not be a problem.
    You keep saying that and it is simply not true. I won't try to argue with you again about it; you clearly have a need to believe in it.
     
    Last edited: Apr 14, 2016
  9. Sarkus Hippomonstrosesquippedalo phobe Valued Senior Member

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    The problem is fairly artificial, to be honest.
    NASA has a guideline lifetime limit for radiation exposure of 1000 milliSieverts for its astronauts, which is thought to raise risk of developing a fatal cancer by 5%. They actually try to limit it to 3% if they can.
    The current risk on earth of developing a cancer is 26%, and improvements are being made all the time with regard survivability. But a 5% increase would currently push up your risk from 26% to c.27.3% (being a 5% increase in risk). Even if the journos meant that it would increase from 26% to 31%, this is not all that significant in the grand scheme of things.

    So how does a trip to Mars compare with the 1,000 mSv limit...
    A trip to Mars that takes 6 months each way would, during the travel phases, result in a dose of c.700 mSv - so within NASA's current guideline. This was established by monitoring the radiation on the trip by Curiosity.
    This doesn't include time spent on Mars, but based on latest readings it is currently thought that a 500-day stay on the planet would push the overall total to 1,000 mSv.

    So this is not, as you suggest, an insurmountable problem, it is simply an acceptance that travelling in space has risks. And it is an artificial problem for NASA in as much as it is only a problem keeping within their current guidelines. All they have to do, and will likely do, is relax these guidelines for such interplanetary missions.

    If you have any evidence to the contrary that the radiation is more of an issue than this, let's hear it please.
    Otherwise I think we can drop the whole "radiation is a problem we can't solve" line.

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    Sources:
    www.space.com/23875-mars-radiation-life-manned-mission.html
    www.mars-one.com/faq/health-and-ethics/how-much-radiation-will-the-settlers-be-exposed-to
     
  10. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    I was speaking of traveling to another star's habital planet, noted suspended animation would be required, etc. and only used the trip to Mars to get some data. I'll quote part of your first link:
    Fact is the that we don't know how much stronger the Galactic Cosmic Rays, GCRs are once the ship has left the region of intense solar wind, which is resisting the penetration of GCR into the solar system. There could well be 10 milisievers per day or more of GCRs in deep space, but for calculations I'll assume 10 milisievers per day. That means almost all of the trip, which would be more than a century or or at least 36,500 days, the unshielded crew would get 365 sievers, which is a lethal dose, EACH DAY! The current limit of NASA for human exposure is only 1 siever!

    As these GCR are extremely energetic particles, making them pass thru a foot of lead, would only make the crew's exposure to ionizing radiation much worse. Each GCR will produce at least 100 high energy, ionizing, particles emerging from the "back side" of a foot of lead.* Or each primary GCR hitting the lead would give more than 3 times the current NASA limit EACH DAY! Also note that in deep space the GCR come from all possible directions so the ship would need to be completely surrounded by a shield every where thicker than a foot of lead.

    Once the energy of the typical "daughter" the primary ray has produced, falls to about a 10KeV level, then water, which would be needed anyway, is better shielding than lead, as on average its two protons will recoil when struck with half the energy energy of the incident particle and certainly will not increase, via daughters, the total number of ionizing particle by more than a factor of two. The still high energy particles emerging from the "back side" of the outer lead layer, will also hit the Oxygen nucleus occasionally and prehaps sometimes shatter it into more than two lower energy particles, perhaps some alpha particles (2P + 2N), but they will barely penetrate thru the skin.

    I probably will not comment on your other link: www.mars-one.com/faq/health-and-ethics/how-much-radiation-will-the-settlers-be-exposed-to
    As we have no idea how strong the solar wind from that other star will be or the strength of the planet's magnetic field, if any.

    * Admitedly that is only my quick guess. I am sure the flux of dauthers for an assumed energy of the incident primary ray can be found somewhere in the internet. Please correct my guess if willing to search, and then consider the not well known (as measured inside the solar system) energy distribution of GCR expected in deep space.
     
    Last edited: Apr 14, 2016
  11. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    On (1) Thanks. So the energy source opperates all the time / duration of the trip. So there will be no problem with keeping warm in a < -250C eneviroment; but there will be a problem with the crew not being cooked by its waste heat. As there will be no lakes, rivers, or evaporative cooling towers, do you have any idea how to avoid cooking the crew?

    How far is the nearest star with a habital planet, would you guess? I think the duration of the trip at 0.1C average speed, is measured in centuries, not decades. I agree a max speed limit of 0.2C is wise (or perhaps optimistic) as we want the Glactic Cosmic Rays to be the main source of radiation exposure, not the collisions with the protons (ionized hydrogen atoms) that drift in space to be larger.

    (2) Actually I googled for the typical efficiency of a nuclear power plant, but agree that 2/3 of the generated energy being waste heat that must be dumped into space is what known technology would produce.
    I have several posts describing a Carnot limited system for use on the moon that can get better than 80% efficiency. I think any "life boat" for humans will be on the moon, not Mars which will be periodicly (ever 780 days) on the other side of the sun, 2+ AU from earth as meeting its energy requirments is much easier on the moon.
    At either site, the life boat's occupants will be only women until they raise some males using the cryo-jug of sperm, and more than 95% of their lives will be under ground in volumes that robot digging and construction machines made before they first of the set foot on their new home.

    (3) The not yet achievable pair of energy sources you mention, both release their energy traveling in all directions, so there is no thrust directly available from them. Most of that released energy would just slam into the ship, heating it, but if in charged particles, not very intense EM radiation, those not going out the back of the ship could be turned around via a magnetic field, which need not take much power if made by super conducting coils. (They could radiate into the <-250C space to maintain their operating temperature.)

    I think mutual annihilation of particles with its anti-particle makes only EM radiation and the "bottle" for the anti-matter is not easy to make and would require energy, so the D-He3 fusion is surely the way to go; but there is no He3 on earth.

    Some postulate it is in the solar wind and some now mine-able from the surface layers of the moon; but I have some post explaining that He is used in vacuum leak detectors as it escapes thru smaller holes than anything else. There is thus, zero reason to think it remains for more than a few seconds "trapped" in the surface layer of "moon dust" instead of leaking out into the surrounding vacuum. He3 is mentioned by people desperate to find something on the moon, that is not already available on earth at a tiny fraction of the cost importing from the moon would have. (Very ignorant or dishonest people, IMO, trying to support moon exploitation for material useful on earth.)

    (4) There is no "outside" source once out side the solar wind.

    (5) No I don't "need to believe it." I just quote the facts, given by NASA mainly. See posts 124 & 127 for a few of them. (Quotes from NASA)

    Time for correction of post 127 has expired:
    365 sievers, which is a lethal dose, EACH DAY!
    Should be in 100 YEARs.
    (On a trip more than a 100 years long)
    If the planet is already inhabited with advanced life forms, they may destroy earth for sending biological trash to their planet.
     
    Last edited: Apr 14, 2016
  12. Sarkus Hippomonstrosesquippedalo phobe Valued Senior Member

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    I was specifically responding to your claim, and I quote:
    I.e. You were specifically saying that there was no solution in sight for even the 780 day mission to Mars.
    As I have detailed, this is patently wrong.
    This may not have been what you had meant to imply, but nonetheless you did. So feel free to retract it, or if you still believe it to be true, stand by your claim and support it.
    You may want to check your calcs... As the 365 sieverts would be the dosage accumulated over 100 years, not "EACH DAY!"

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  13. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Yes I retract it. I was and am focused on the thread's topic - trip to star, but we can not be sure that unintended statement is "patently wrong." Going to Mars may be possible only in periods of high solar winds (with luck, as that is when solar flares are most probable too, I think.) Must leave house soon, ironically to get my daily dose of radiation cancer treatment.
     
  14. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Yes NASA could increase their limit from 1 to say 3.65 sievert, but that would still be 100 times less than one can reasonably expected that a 100 or more year long trip to a suitable star, would acumulate in deep space and subject the crew to. (See post 127, as corrected in post 128 for detail support for these estimates.)

    As I noted in another post, the "inhabitable planet" of another star, which would be as old as Earth, and thus probably will have intelligent life forms already occupying it. Lets hope they are not more advanced technically than humans. If they are, they may destroy Earth in response to Earth sending a ship load of rotting, biological garbage* to their planet.

    * Remains of the crew.
     
    Last edited: Apr 16, 2016
  15. joepistole Deacon Blues Valued Senior Member

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    I think the decision to abandon colonization was based on a number of factors. But chief among them, and perhaps the decisive factor, were some of the near disasters which vexed the Apollo program. Imagine pilots marooned in space and dying a slow death. I think that vision was in large part responsible for the decision. NASA became overly risk adverse. The technology was being stretched. That said, I was deeply disappointed with the decision to abandon colonization in favor of the shuttle and the space station. I thought, and still do, it is worth the risk. I think we should begin colonizing the Moon in preparation for Mars. I thought then, and do now, the shuttle was an overpriced shinny bauble.
     
  16. paddoboy Valued Senior Member

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    There will always be risk in space exploration, just as there is risk climbing Mnt Everest. That will not stop the inevitable progress of humans in time exploring exploring Mars and even beyond to the stars, if we are able to survive our man made follies here on Earth, and of course the astronomical catastrophes that could head our way.
    I believe what we are experiencing now with manned exploration is more of a hiatus and the two horrible variables of economics and politics.
    But those two as I say are variables and in time things will be favourable again.
    Time of course will allow us to eventually overcome all the obvious dangers including radiation, but one thing is certain in my books, we will certainly not stagnate on this fart arse little blue orb, and just as for the reasons we climb Everest, [despite the dangers] we will continue upwards, outwards and beyond to the stars.
     
  17. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Why go on to Mars? Solar energy on the moon can be converted with three times higher conversion efficiency (about 80% or more) and much more cheaply per KWH.

    A trip to the moon is only days but under optimum conditions, that reoccur every 780 days, a round trip to/from Mars* with any useful duration on the moon is at least three years long. Furthermore, most of the time (2/3, I guess). Mars is further from Earth than the sun is (>1AU). For a month or two every 780 days, Mars is at least 2AU from earth (mainly on other side of the sun)

    If an astronaut or settler on the moon breaks a leg with compound fracture and protruding bone, you can bring him / her back to Earth where X-ray machines and experienced medical teams are common. That is probably a death sentence if it happens on Mars. Lots of things can go wrong in the first century of the colony's existence, before it is really "self- sufficient" that will require prompt assistance from Earth. You can't have redundant copies of ever thing that can break.

    * And may not be possible around the time of low solar wind in that 11 year cycle. (Less deflection of the Galactic Cosmic Rays, incident on the solar system then).

    PS to Paddoby:I don't doubt that man has the desire and courage to try to go to a habital planet of some distant star; but does not have for the foreseeable future, and probably never, the technology. For example, suspended animations for several years. Also as it would be as old as Earth is, why would we expect it not to be already inhabited with intelligent life? (God made humans only for Earth? Why would he put them only on " this fart arse little blue orb"?)
     
    Last edited: Apr 16, 2016
  18. joepistole Deacon Blues Valued Senior Member

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    There will always be risks in space exploration. And while we science aficionados, including the astronauts are willing to pay those costs, many Americans are not. Many don't support space exploration period. I can't imagine a lunar base would be much more expensive than the shuttle program. So I don't think it's a matter of economics. I think it is a matter of politics. We need a leader like Kennedy to lead a space effort, and unfortunately I don't see one on the horizon.
     
  19. joepistole Deacon Blues Valued Senior Member

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    Why go to Mars? Because it's there, and humans are explorers. It's in our DNA. But because of the distances you pointed out and the inaccessibility, we really need to iron out the kinks before we attempt to colonize Mars. The Moon would be a good proving ground. A Martian colony would need to be self sufficient.

    Given the low gravity on the Moon and Mars, I don't think residents will have much trouble with compound fractures or fractures period. But they could face other and more immediate crises. Compound fractures are rarely, if ever, life threatening. However, they can be disabling.
     
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  20. paddoboy Valued Senior Member

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    "

    Of course they [astronauts] face risk and as you say that will not stop humans exploring their environment.
    The other point to consider is that the space industry now is far more widely spread than just the USA and NASA: Plus of course the spread to private industry.
    I don't knock the ISS or the space shuttle, both achieved many goals and the ISS is still achieving them.
    I still see us having a permanent out post on the Moon first and then finally Mars in time.
     
  21. billvon Valued Senior Member

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    Are you making stuff up again, Billy? It makes people take your other posts less seriously when you do that.
    So in your opinion, if someone gets a compound fracture in (say) Antarctica, that would be a "death sentence" unless they could get them back to the mainland?
     

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