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How far could we detect a rocket in space?

  1. Jan 17, 2014 #1
    For exact example, the Apollo rocket, that carried Armstrong to the Moon?

    Yes i read atomic rockets, but that happened : http://en.wikipedia.org/wiki/Chelyabinsk_meteor

    It looks like to me, they were a bit over optimistic about how far can we detect a simple heat radiating object. Ok that meteor came from the direction of the Sun (isnt an impossible stealth option for a rocket neither), but still, if such faint objects can be detected only in the last few hours, that seems to me a scale below the ranges suggested by that site.
    Maybe they underestimated infrared background clutter, or i misunderstood something?
  2. jcsd
  3. Jan 17, 2014 #2


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    hi there

    Not sure what atomic rockets has to do with it ?

    dont forget it wasnt radiating any significant heat before atmospheric entry .... it seems that you think it was ?

    they can only really be detected by either radar or optically

  4. Jan 17, 2014 #3


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  5. Jan 17, 2014 #4
    "dont forget it wasnt radiating any significant heat"

    Does that mean it doesnt warmed up by sunlight, to a degree similar to lunar average?
    With 200K i still calculated millions km detection range, based on their equitation.
  6. Jan 17, 2014 #5


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    Asteroid J002E3, detected in high Earth orbit near the L1 point (~1.5 million km), turned out to be the Apollo 12 third stage. It was rediscovered in 2003 when it re-entered Earth orbit from heliocentric orbit.
  7. Jan 18, 2014 #6
    Remember that Atomic Rocket makes a very important(and reasonable) assumption. Any polity which can launch large spacecraft on a regular basis can afford to spread huge numbers of observation satellites throughout the solar system. We don't have very many of those right now.
  8. Jan 18, 2014 #7

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    There's a lot of nonsense and misinformation in that latter link.

    Those telescopes could spot Voyager because the operators already knew where to look. Suppose they had no clue where to look; which is what the situation would be if one were looking for invaders. Suppose they took two seconds to take an image and only took another couple of seconds to move the telescope to the next area of the sky. Let's ignore the fact that there will have to be some overlap in images to get a full scan of the sky. How long would this full sky scan take with the Green Banks Telescope? The answer is almost a year. Not four hours.

    Voyager is of course aiming it's antennas straight toward the Earth. Would intruders be broadcasting their presence and aiming their antennas straight at the place they are about to attack? No. They are not going to come in sending signals straight at us, or firing thrusters straight at us. Even if we were looking at exactly the right spot in the sky we might never see them.

    Think of it this way: An alien intruder did exactly that last February over Chelyabinsk. We never saw that meteor coming. After the fact, astronomers looked at previously gathered images to see if it had ever been seen. It hadn't.
  9. Apr 23, 2014 #8
    In Rise of Leviathan there were some stealth ships, described as strategical instead of tactical weapon.
    I know that due to the laws of thermodynamics you cant contain your waste heat forever, let alone hide the flames of the thrusters. (Magnetic sails would have pretty big radar cross-section on the other hand.)

    However, is that true, what is written on that not so reliable atomic rockets link?
    "Furthermore, directing your waste heat (and making some part of your ship colder, a related phenomena) requires more power for the heat pump - and every W of power generated generates 4 W of waste heat."

    What if they use liquid helium and magnetic cooling instead of the traditional method of compressing gases?
    Would that be more efficient for containing or beaming away waste heat?
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