Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Relativistic effects of a low orbit around supermassive objects

  1. Feb 27, 2014 #1
    Hi everyone, first post here. Lurking for a while but it was time to register..
    I'm trying to conceptualize an idea in which humans are sent to orbit a very massive object, like a neutron star, a magnetar or even possibly a black hole. I would like the ship to be relatively close to the surface that is spinning at maybe 50 hz, and also, the ship should be stationary above its surface.

    So my questions are 1) can I do this without killing the astronauts,
    2) What would be the major issues in entering and maintaining such an orbit?

    3) What would they see, looking out the window up to the sky? Considering the relativistic effects of them spinning around the object at speeds near C.

    I'd appreciate any thoughts on the subject!

    /D
     
  2. jcsd
  3. Feb 27, 2014 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    A black hole has nothing that could be described as "spinning surface".

    Orbiting an object with 1 solar mass with 50 Hz needs an orbital radius of ~100km and an orbital speed of ~35000km/s or .1c. For a rough approximation, we can still neglect relativistic effects.

    1) Tidal accelerations would be ~40000g/m. That means head and feet feel accelerations of 40000g relative to the center of the body. There is absolutely no way to survive this, the astronauts would get ripped apart in milliseconds. Even the strongest materials available today would struggle to maintain the integrity of a spacecraft with a "height" (as seen as radial distance) of more than a few meters, and I think the other directions are even worse (as compression is harder to manage compared to tension)

    2) The major issue in entering this orbit: assuming the environment of the massive object is empty enough to avoid collisions with gas/objects: braking. Coming from a point far away, the spacecraft would have to accelerate (backwards) by .05c on its own somehow. Nuclear propulsion methods might be able to deliver this, chemical rockets are completely pointless here.

    3) Towards the neutron star or similar: probably nothing, as the object is so hot it will make a human eye blind quickly.
    Towards the neutron star or similar, with appropriate shielding: a small white disk.
    Towards everything else, with even better shielding against the neutron star radiation: probably blurry lines from all the other objects (apparently) swirling around you with a rate of 50 Hz.
     
  4. Feb 28, 2014 #3
    Thanks mfb, great feedback... didnt take tidal forces into account. Guess I need to figure out some fictional technology that will help reduce these effects, but not eliminate them alltogether. The environment should be totally empty - it's a lone object approaching the solar system.

    If we assume the spaceship has appropriate light filtering system - kindof what they had on the movie Sunshine while approaching the sun. Would the neutron star have any kind of structure or heat differences on the surface that would translate into a more interesting view?

    Another thing is, for plot reasons I need the astronauts in orbit to have much more time available to them than earth time. If the neutron star will enter the solar system in 5 years time, could I use relativistic effects to make their stay in orbit last a lot longer than 5 years (for them).

    Again, thanks for your help!
     
  5. Feb 28, 2014 #4

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    I would guess so (especially for pulsars), but I don't know.

    I don't see how this would work in any even remotely realistic way. If you need more "thinking time", use more astronauts or a better computer. If you need more manual work, use more astronauts or more machines. What other reason is there for more time for astronauts?
     
  6. Mar 1, 2014 #5
    What Im trying to get is, once they enter the strong gravitational field do they locally still have (the on earth calculated) 5 years before the event happens, or will they have less time, because their clock is now ticking slower relative to earth?
     
  7. Mar 1, 2014 #6

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    There are two different effects: as seen from earth they are moving fast (special-relativistic time dilation gives them more time), but at the same time they are close to a massive object (gravitational time dilation gives them less time). In an orbit, as far as I remember the second effect wins, so they have a bit less than five years.
    I don't see the relevance of this, however.
     
  8. Mar 2, 2014 #7
    If it's a magnetar, then you would also have to watch out for the effects of an extremely powerful magnetic field-

    http://en.wikipedia.org/wiki/Magnetar#Magnetic_field
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Relativistic effects of a low orbit around supermassive objects
Loading...