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Brotoro

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    Imperial versus metric

    in Science & Spaceflight

    Posted

    8 hours ago, Bej Kerman said:

    I really hope you can see that measuring days, months and years using the orbits of the Earth and the Moon is not as absurd as using imperial for no other reason than "it was there, I guess".

    I didn't say anything against using days or months or years. I spoke about dividing days arbitrarily into 24 hours, and hours into 60 minutes, and blocking days into arbitrary 7-day weeks... which people manage to deal with even though those aren't powers of ten.

    [New] Space Launch System / Orion Discussion Thread

    in Science & Spaceflight

    Posted

    2 hours ago, magnemoe said:

    Was the capsule recovered by an helicopter too? They used an carrier for recovery so it makes some sense. 
    SpaceX has an dedicated ship for fishing it out of the water, an fishing boat. 

    As I recall, the carrier maneuvered alongside the capsule and then hauled it aboard with a crane. But I never actually saw that step happen on TV... I think it took quite a while to do, hence the desire to get the astronauts to the ship in a more timely manner.

    X-37B

    in Science & Spaceflight

    Posted

    It doesn't strike me as mysterious why the X-37B is on long missions.

    It was originally a reusable spaceplane tested at NASA. Then the design was given to the Air Force as a research tool. Once the Air Force has a toy with interesting capabilities, they aren't going want to give it up. What, it only has a small payload capacity compared to other options (such as Dragon) that were developed later? Ah, but look what the X-37B can do: Very long duration missions! I bet your Dragon was built for that. So, they send an X-37B up on longer and longer missions to justify keeping them, at the cost of a launch vehicle every couple years.

    Whatever research they are doing can't be vital, or they would have several of them running in parallel (you don't want to wait two years to get your vital data only to have it lost in a reentry accident...you'd have more doing the research as backup).

    X-37B

    in Science & Spaceflight

    Posted

    2 hours ago, kerbiloid said:

    ...a nuclear warhead (consists of a complicated sequence of thin isotope layers, being irradiated by various sorts of space radiation, radiating themselves, quickly changing their isotope and chemical composition say, Pu→Am, and thus requiring a long-term study to ensure that being put in LEO it won't rot or pop three years later).

    Quickly changing? I don't think the numbers support this idea. A kilogram of Pu 239 has hundreds of billions of radioactive decays occurring within in every second. Cosmic ray flux of GeV particles is only 10^4 per square METER per second (the flux of TeV cosmic rays is only 1 per m^2 per second, and the flux rate for even higher energy particles falls off precipitously). And a kilogram of Pu has a cross-section of much less than a square meter. The number of Pu atoms being converted by cosmic rays (even assuming a 100% efficiency of conversion) is going to be insignificant compared to the number of conversions going on naturally inside the Plutonium all the time...and the chunks of Plutonium metal take that vastly greater number of disruptions to its crystal structure in stride without affecting its ability to go boom when you squeeze it. At least not on the time scales of our civilizations. 

    The structures that make up a nuclear weapon are not nearly as susceptible to radiation damage as fragile biological and electronic components of spacecraft (and we already study those effects). Also, the outer layer of the physics package that makes up the radiation channel reflector outer layer will act to shield the internal components from external radiation. Your concern makes no sense to me.

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