Pulsars for Space GPS

[rgrove0172]

What are your thoughts on deep space craft using pulsars for determining their location? I know we theorize a set of 4 pulsars centered on our solar system for such a purpose is upcoming but Im certain that in time each region of space would have their own that could be utilized to calculate just where your ship currently was. Would this be the commonplace method of astral navigation in 2300ad?

 

[HG_B]

GURPS travel used this I think. I use it into.

 

[LemnOc]

It was a common enough notion in 1972 when Pioneer 10 was launched. The plaque it carried held pulsar data. Not only would this serve as cosmic GPS but cosmic chronometer as well.

http://www.setv.org/nasa_probes.html

 

[BytePro]

Funny timing (pun), given some recent news (selection for next 'Explorer Mission of Opportunity'):http://www.nasa.gov/topics/universe/features/zombie-stars-sidebar.html
(see also: http://gcd.larc.nasa.gov/projects/deep-space-x-ray-navigation-and-communication/)

Back in 2010 or so, (x-ray) pulsar navigation interest really picked up - but scientists recognized the potential since pretty much the discovery of pulsars. Do note that pulsar beams are 'directional' (i.e. not omni-directional beams - something to consider if a setting spans dozens+ ly) and also suffer 'glitches' in timing - but there are plenty of them to choose from...

 

[rgrove0172]

Funny timing (pun), given some recent news (selection for next 'Explorer Mission of Opportunity'):http://www.nasa.gov/topics/universe/features/zombie-stars-sidebar.html
(see also: http://gcd.larc.nasa.gov/projects/deep-space-x-ray-navigation-and-communication/)

Back in 2010 or so, (x-ray) pulsar navigation interest really picked up - but scientists recognized the potential since pretty much the discovery of pulsars. Do note that pulsar beams are 'directional' (i.e. not omni-directional beams - something to consider if a setting spans dozens+ ly) and also suffer 'glitches' in timing - but there are plenty of them to choose from...

Thanks for the links, good stuff. Ill assume that the navigational computers determine when to "switch beacons" sort of speak based on the region of space they are entering to get the best fix.

 

[LemnOc]

Ill assume that the navigational computers determine when to "switch beacons" sort of speak based on the region of space they are entering to get the best fix.

Given the distance of these objects versus the size of Known Space it's kind of silly to "get a fix." Why not just assume that, with minimally operating nav sensors, tuned to receive these signals, no ship is ever really lost in space and always has a fairly precise known position?

 

[rgrove0172]

Same effect sure, I realize how distant these things are but was taken by the fact that in several articles it seemed that a certain group of pulsars were used as they were positioned advantageously. My assumption was that 40 or 50 light years away, other pulsars might be more advantageous. But Im guessing here, my knowledge of astronomy is a joke.

 

[BytePro]

Yes - 40 or 50 ly away some pulses might not be observable - i.e. their pulse would not sweep the detecting system.

 

[Darkwing]

Given the distance of these objects versus the size of Known Space it's kind of silly to "get a fix." Why not just assume that, with minimally operating nav sensors, tuned to receive these signals, no ship is ever really lost in space and always has a fairly precise known position?

Bad practice. Why do you think the Guardian ran aground on that reef? Lack of visual fixes to check the malfunctioning GPS against. Pulsars would NOT be like GPS, but would be exactly performing visual navigation. The distance is NOT a consideration. Pulsars would be identifiable at a very long distance, and would stand out from other stars due to their pulses.

 

[shaunhilburn]

Same effect sure, I realize how distant these things are but was taken by the fact that in several articles it seemed that a certain group of pulsars were used as they were positioned advantageously. My assumption was that 40 or 50 light years away, other pulsars might be more advantageous. But Im guessing here, my knowledge of astronomy is a joke.

The nearest pulsar is PSR J0108-1431, 424 light-years distant. It could sweep the entire near-star map with a beam 12.9 degrees wide.

 

[Darkwing]

Google Sumner Lines for an idea how visual navigation works. Any star you can identify would work, pulsars would be easily identifiable for a greater distance than most stars. Well-discussed in Pub 9 / American Practical Navigator /Bowditch and in Dutton's. pdfs available free online for Bowditch.

 

[aramis]

the biggest issue for pulsars would be if were outside the pulse arc of your reference pulsars... if you can't see the pulse, you can't ID them as easily. Not much of an issu for jump or hop drives, but a potential issue for skip drives...

 

[whartung]

So the question essentially boils down to:

Is it a safe to say that given the limitations of pulsars, there are enough of them within the confines of "known space" that you can get a fix on several to identify your position? While different pulsars may be visible and readable at any point, there's enough overlap to make them a reasonable navigation tool?

This, to me, is more important in regular Traveller than in 2300, simply because Traveller has the Jump drive (and misjumps) where you can "suddenly" find yourself in the "middle of nowhere". So, are pulsars effective enough to be a reliable tool to find out where you popped out of jump space, especially given how far a misjump can take you.

 

[rgrove0172]

Pretty important for stutterwarping too as a problem in your navigation system could stir you just a degree or so off course and find you zipping off to nowhere after a few hours with, oh yeah, a full charge on your coils.

 

[LemnOc]

This, to me, is more important in regular Traveller than in 2300, simply because Traveller has the Jump drive (and misjumps) where you can "suddenly" find yourself in the "middle of nowhere". So, are pulsars effective enough to be a reliable tool to find out where you popped out of jump space, especially given how far a misjump can take you.

I agree. In 2300, you're averaging about 1 ly per day with a drive system that allows you to stop, look around, and resume travel without penalty or velocity loss. Plenty of time to do a nav check, if you're worried, and not much potential to get hopelessly lost. I would assume anyone with a charged drive at risk would do all of their critical nav before departing a gravity well, not just light out and adjust, dead reckoning, along the way.

Given the distance of most of these pulsar objects, my surmise is their parallaxes don't change much (a little) across the whole bubble of 2300 known space, which is less than 100 ly across. That was my original point about it being a little "silly" to "get a fix"... not that nav fixes aren't important. But the "constellation" of pulsars is not likely to be terribly different (a little different) across the width of known space than the constellations of stars are apt to be much different across the width of the solar system. A little parallax shift, for the nearest of them.