Astronavigation
- Thread starter Spinward Flow
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Don’t have time to watch this at the moment, but do they get into inertial navigation systems and using reference pulsars?
Spinward Flow
SOC-14 1K
Here's a question about pulsars.
How long do they "pulse"? That is, how long are their "signature" pulses stable? We don't have any data more than, what, 50 years old? Does it last 1000s of year? 100,000 years?
I only ask because when you start jaunting around the galaxy and are 10,000 light years away from where you though you were due to a truly amazing misjump, would the pulsars that you relied on to help position yourself before still be the same? Because it's now 10,000 years earlier/later/etc. from when your measurements were placed.
How long do they "pulse"? That is, how long are their "signature" pulses stable? We don't have any data more than, what, 50 years old? Does it last 1000s of year? 100,000 years?
I only ask because when you start jaunting around the galaxy and are 10,000 light years away from where you though you were due to a truly amazing misjump, would the pulsars that you relied on to help position yourself before still be the same? Because it's now 10,000 years earlier/later/etc. from when your measurements were placed.
One source says 10^7 (ten million) years, but their periods do slow over time, hence the indicated lifetime. That could interfere with identification, but could also improve distance estimates once identified, until other reference points are located. (http://burro.astr.cwru.edu/Academics/Astr221/LifeCycle/pulsars.html)
Wikipedia says 10-100 million years. Some types (rotation-powered) stop sooner than others. Most that have ever existed have already expired.
Got a chuckle out of the Wikipedia article on Pulsar-based navigation:
Aircraft navigation
In 2014, a feasibility study was carried out by the National Aerospace Laboratory of Amsterdam, for use of pulsars in place of GPS in navigation. The advantage of pulsar navigation would be more available signals than from satnav constellations, being unjammable, with the broad range of frequencies available, and security of signal sources from destruction by anti-satellite weapons.[13]
(Emphasis added, of course.)
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Spinward Flow
SOC-14 1K
They're not "stable for eternity" in the sense of being unchanging for entire age of the universe. So if you "time travel" (so to speak) by moving FTL then questions of "wind back" on what pulsars were doing in the past can become relevant depending on how many light years you're jumping/hopping/skipping/etc. over. For one thing, it's possible to FTL beyond the point where light from the pulsar would have to have started before the star to pulsar collapse happened simply due to the light years of distance involved.
In terms of how accurate/precise are pulsars ... they are the most MASSIVE light emitting gyroscopes in the universe (black holes "don't count" because any light/wind emitted from them comes from the accretion disk orbiting around the black hole rather than from the black hole itself), so modifying the rotation of a pulsating neutron star takes a LOT of angular momentum +/- to speed them up or slow them down (because stellar mass!). Modern observations are finding that pulsar rotations are MORE ACCURATE AND PRECISE than atomic clocks.
The way that chronometric and navigation technology is moving (from a terrestrial frame to an astronomical one), it is extremely likely that "pulsar clocks" are going to become the new benchmark replacing atomic clock technology as the "way to do it" at the next tech level.
Here's another data point for you to consider.
The Golden Disk aboard Voyager 1 and 2 (launched in 1977).
See that "starburst" shape in the bottom left?
Do you know what that is?
It's a 2D rendering of a group of nearby pulsars and the timing of their pulses so that an alien could 3D find Sol in the Milky Way galaxy ... using just pulsars for navigation.
Commander Truestar
SOC-13
Pulsars can be valuable regardless of "when" you are seeing them.
But, only if you have a database of how long are each pulsar's "signature" pulse lasts "And" a proper understanding of how they will change over time.
If you are in FTL across a meaningful distance of space, you can expect the values of known pulsars to change.
Having that, a navigator can take a read on all visible pulsars at the destination, then compute the FTL dilation effect to get a corrected Date/Time
With that, the navigator can test to see if the pulses from all detectable pulsars correspond to Date/Time updated expectations?
Invariably, there will be new pulsars visible to the ship's instrumentation, just as there were new stars visible in the Hubble Deep Field Survey that had not been visible to pre-Hubble instruments
But those can be ignored where a Navigator can acquire four or more of the expected pulsars
Once they are located, this would allow the Astrogator to "Re-orient" their stars and work out a location, relative or specific.
But, only if you have a database of how long are each pulsar's "signature" pulse lasts "And" a proper understanding of how they will change over time.
If you are in FTL across a meaningful distance of space, you can expect the values of known pulsars to change.
Having that, a navigator can take a read on all visible pulsars at the destination, then compute the FTL dilation effect to get a corrected Date/Time
With that, the navigator can test to see if the pulses from all detectable pulsars correspond to Date/Time updated expectations?
Invariably, there will be new pulsars visible to the ship's instrumentation, just as there were new stars visible in the Hubble Deep Field Survey that had not been visible to pre-Hubble instruments
But those can be ignored where a Navigator can acquire four or more of the expected pulsars
Once they are located, this would allow the Astrogator to "Re-orient" their stars and work out a location, relative or specific.
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