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    • CommentAuthorFan
    • CommentTimeJul 22nd 2009
     (5884.201)
    Maybe because Rover has been successful, it's done what it can and there's little new that it would be capable of.
    • CommentAuthorMechanist
    • CommentTimeJul 23rd 2009
     (5884.202)
    I'm having a time out until I can learn some manners.
    We need to stop with the robots really. One more unmanned mission entirely dedicated to finding a suitable landing site and surveying it followed by a manned mission thats what we need.

    I just hope China take the place of Russia in the whole competition thing so that the yanks will actually pull their finger out of their arse and get to work.
    • CommentAuthorKosmopolit
    • CommentTimeJul 23rd 2009
     (5884.203)
    The current rovers have covered maybe one square mile between them - on a planet with a ground surface as big as Earth's. (no oceans remember?)

    See I'm a greedy SOB I don;t want just robotic exploration or just huma exploration.

    For the cost of the MSL, NASA could probably land a dozen rovers the size and generation configuration of Sojourner.

    We could take a look at Mons Olympus, check out the areas which appear to be outgassing methane (a possible sign of life); visit the Allan Hills (the source of at least one meteorite that landed here on Earth); study the areas in the subarctic zones that seem to be rapidly losing ice coverage; we could check for water ice in the polar regions.

    And much of the same technology could be re-used on the moon; on the major asteroids; on Venus; on the Jovian satellites.

    I can understand the desire to get NASA out of the way of the market but we're still at the point where the returns are too remote and uncertain and the amounts required are too large.
    • CommentAuthorFan
    • CommentTimeJul 23rd 2009
     (5884.204)
    I don't know why but "engineering constraints" say they that can't land near the poles. My guess as to why is that in the Rover's case it's because it's solar-powered and already under-powered, and in MSL's case (which is nuclear-powered) it's that too near poles you'd lose line-of-site radio transmission back to Earth for half the year.
    • CommentAuthorlooneynerd
    • CommentTimeJul 23rd 2009
     (5884.205)
    As far as the human exploration goes, does anybody happen to know what escape velocity on Mars. As much as I'd love to see it, I can't think of a way to get a ship there with enough fuel to land and take off again on the surface. Even doing something like the balloon experiments in the 50's you'd need a massive amount of energy to both keep the crew alive to and from there and to get the vessel off of the ground twice, wouldn't you?
  1.  (5884.206)
    @looneynerd

    That's assuming that they're taking everything with them in one trip. Is there a reason that certain supplies and fuel couldn't be sent there before the mission and monitored remotely?
    • CommentAuthorFan
    • CommentTimeJul 23rd 2009
     (5884.207)
    > As far as the human exploration goes, does anybody happen to know what escape velocity on Mars

    http://en.wikipedia.org/wiki/Escape_velocity says,

    Moon: 2.4 km/s (but only 1.4 km/s to escape back to Earth)
    Mars: 5.0 km/s
    Earth: 11.2 km/s
    Solar system: 42.1 km/s

    I was wondering how the lunar lander could even escape the moon, given that it's *so* much smaller than the Saturn, and that its escape velocity is only 10 times smaller. I expect it's that the amount of fuel required isn't linear: that as the needed energy increases you need non-linearly more fuel, in order to lift the additional fuel.

    Saturn V: mass 3000 tons, payload 50 or 100 tons.

    The Saturn's payload was:

    * Command module (pressurised crew cabin, heat shield, controls): 5 tons
    * Service module (batteries, oxygen, water, and rockets to leave lunar orbit): 25 tons
    * Lunar module: descent 10 tons, plus ascent 5 tons
    • CommentAuthorStefanJ
    • CommentTimeJul 23rd 2009
     (5884.208)
    Escape velocities, from Answers.com:

    # Sun 617.5 km/s
    # Mercury 4.3 km/s
    # Venus 10.13 km/s
    # Earth 11.2 km/s
    # Moon 2.4 km/s
    # Mars 5 km/s
    # Jupiter 59.5 km/s
    # Saturn 35.6 km/s
    # Uranus 21.2 km/s
    # Neptune 23.6 km/s

    A lot of research / engineering tests have been done on an automated methane-generating station for refueling a Mars ascent stage.
    • CommentAuthorlooneynerd
    • CommentTimeJul 23rd 2009
     (5884.209)
    @Fan

    Getting off of the moon is a bit easier because of the lack of atmosphere as well, and the gravitational pull isn't as "wide" as Earth's, meaning the lander had less time to spend at escape velocity.
    • CommentAuthorFan
    • CommentTimeJul 23rd 2009
     (5884.210)
    These figures may be misleading: for example, low earth orbit is already 8 km/sec.

    See also http://en.wikipedia.org/wiki/Delta-v_budget#Interplanetary_budget lists and http://en.wikipedia.org/wiki/Delta-v_budget#Delta-vs_between_Earth_and_Mars
    • CommentAuthorFan
    • CommentTimeJul 23rd 2009
     (5884.211)
    > As much as I'd love to see it, I can't think of a way to get a ship there with enough fuel to land and take off again on the surface.

    The biggest cost is getting off Earth: people (SF writers) used to suggest launching Mars missions from Earth orbit, instead of from Earth's surface.
    • CommentAuthorMechanist
    • CommentTimeJul 23rd 2009
     (5884.212)
    I'm having a time out until I can learn some manners.
    Launching a mission that big from orbit is the only way to do it. Well do it well at least. Otherwise you're just going to mount up insane costs and waste.
    • CommentAuthorKosmopolit
    • CommentTimeJul 23rd 2009
     (5884.213)
    At a quick look, most of the serious Mars mission proposals involve assembling the ship in Earth orbit.

    I tend to think that rather than a single Mars expedition what's needed, from the start, is a plan to colonise Mars.

    So to start with you'd send human expeditions to Phobos or Deimos to establish a base there.

    Then you'd send down robots to identify and clear a landing area.

    Then you'd develop a system to fuel orbital craft locally - there might be volatile compounds on the moons you could use, otherwise you'd need to send down an automated plant to extract fuel - liquid hydrogen and liquid oxygen say - from the atmosphere or regolith.

    Then you ship a Mars-to-orbit vehicle out from Earth and send it down to refuel and use it to make a couple of automated round trips to the base in orbit.

    Then you send the people down.

    It'd take longer and cost more to do it like that but the pay-off would be much greater.
    •  
      CommentAuthorrickiep00h
    • CommentTimeJul 23rd 2009
     (5884.214)
    Kosmo - That's sort of what I was thinking for a manned mission. Rather than a bunch of tiny baby steps, make a few larger steps, but not an "all-in-one-go" step. Yeah, it's expensive, but it's probably doable. And why not? If we can fund it, why not?
    • CommentAuthorKosmopolit
    • CommentTimeJul 23rd 2009
     (5884.215)
    Let's look at something NASA is doing right: supporting commercial development of space travel.

    The VASIMR nuclear-ion drive would cut a trip to Mars to a bit over a month each way.

    The technology is being developed by a private company but NASA's putting up the seed money and will test a small-scale prototype on the ISS by 2013.

    There's also Space Portal, a NASA program to assist private enterprise space development.

    This includes the proposal to offer private companies contracts to deliver cargo to the ISS.

    Remember me saying space still wasn't an attractive commercial proposition?

    Well providing guaranteed business for the successful bidders is one way of changing that.

    Bob Heinlein wrote several times about how the development of long-distance air travel in the US owed a lot to the US Postal Service issuing large contracts for the transcontinental delivery of airmail. They didn't try to fly the planes,. much less build them, but the steady reliable cashflow they offered made the business commercially viable.
    • CommentAuthorlooneynerd
    • CommentTimeJul 23rd 2009
     (5884.216)
    Just to go with a potential argument that I (might) have, does anybody know what the washout rate of astronauts is? I.e., how many people going into the space program fail out because of health, poor test scores, etc?
    • CommentAuthorRenThing
    • CommentTimeJul 23rd 2009
     (5884.217)
    No numbers but I've heard it is, in a word, intense.
    • CommentAuthorMechanist
    • CommentTimeJul 24th 2009
     (5884.218)
    I'm having a time out until I can learn some manners.
    Oh oh Looney I know something relevant to this!

    A Royal Air Force pilot currently serving in 99 Squadron (C-17 cargo planes) applied to the ESA (European Space Agency) to try and become an astronaut. He passed initial tests and went for the medical. They turned him down because he had the most faint heart murmur. Nothing that would ever possibly affect him in his entire life and certainly didn't affect his aircraft flying status but was just not good enough to be an astronaut.

    If they turn down someone for that you can imagine what else they'll turn people down for.

    And Kosmo I love what NASA is doing on that front. They're getting back to their intended purpose of helping civilian industry do the majority of the legwork.
    However we do need to go to Mars with intent to colonise. Beforehand some more robotic missions to survey a landing site and get some initial mineral samples and such so we have an idea of what we'll have to work with. Then we assemble a ship in orbit and send a colony team on its way.

    Yeah it'll be "You'll make it or you'll die" scenario but I'll bet you could find a lot of people who would be up for that.
    • CommentAuthorKosmopolit
    • CommentTimeJul 24th 2009
     (5884.219)
    IIRC, the Apollo astronauts each had to beat out 500 other military pilots to get the nod.
    • CommentAuthorMechanist
    • CommentTimeJul 24th 2009
     (5884.220)
    I'm having a time out until I can learn some manners.
    Yep. Nothing short of perfection is demanded of the poor guys.

    However one day astronauts will be smple wage slaves like most of humanity