Condottiere
Emperor Mongoose
Fly too close to the sun.
Deep space tan.
Deep space tan.
Jumping while underway
- Thread starter phavoc
- Start date
Condottiere
Emperor Mongoose
A[n]goraphobia.
MasterGwydion
Emperor Mongoose
Take a photograph of the sky. How many stars can you see? Each one of those is a datapoint that requires no special equipment to detect. Mk I Eyeball. The hard part is doing the trillions of calculations. What is the difference in 30 or 40 local points of reference versus several million total points of reference. The ship doesn't need any better sensors than Basic Sensors. What is important is the computing power to make the calculations and the incredibly precise astrographic map that each ship would carry in it's database. What We see of the IISS map is just the Travellermap. What the ship's computer sees as the IISS map is all of the centuries of data that the IISS has collected on stars, planets and their movements. So, you already have literal centuries of data to draw from and compare to your current snapshot of space from your perspective.
Condottiere
Emperor Mongoose
You could shortcut that, with known constellations.
That tend to differ, depending on the position of the observer.
That tend to differ, depending on the position of the observer.
You're still missing the point that in order to locate the ship's position within that incredibly accurate map to the precision required for an accurate jump, you need to measure the angles between all the points of light. There's literally no other data you can use.
Identifying the stars? Easy. And if they don't match expectations, you know you've misjumped.
Doing the triangulation maths? Tedious but trivial.
Gathering the observational data, which is basically measuring the angular separation between a whole bunch of miniscule dots? That's the bottleneck. Without extremely precise measurements, all those data points are just compounding error and making the likely location plot fuzzier.
Mk1 eyeball can tell you that Regulus is over there, Vega is over there, Sirius is over there, so we have to be around here... but that's like triangulating mountain peaks to find your map position when you don't have a compass. And the map only shows mountain peaks.
But that's okay, because any ship has much better sensors. The functionally useless crew eyeballs aren't needed.
It's not a task that a merchant freighter would usually be doing. They would normally be updating the astro data as they went, from public sources. Maybe not every port, but at any of them with a decent starport. CAN they take astronomical measurements? Sure. But it's going to take them time to get a plot good enough for a high accuracy jump.
TLDR as I see it (YTU may vary):
(1) jump to deep space
(2) take basic sightings to assure yourself you didn't misjump
(3) jump to destination star
(4) fire up the M-Drive to travel from the star's 100D to the destination world.
Identifying the stars? Easy. And if they don't match expectations, you know you've misjumped.
Doing the triangulation maths? Tedious but trivial.
Gathering the observational data, which is basically measuring the angular separation between a whole bunch of miniscule dots? That's the bottleneck. Without extremely precise measurements, all those data points are just compounding error and making the likely location plot fuzzier.
Mk1 eyeball can tell you that Regulus is over there, Vega is over there, Sirius is over there, so we have to be around here... but that's like triangulating mountain peaks to find your map position when you don't have a compass. And the map only shows mountain peaks.
But that's okay, because any ship has much better sensors. The functionally useless crew eyeballs aren't needed.
It's not a task that a merchant freighter would usually be doing. They would normally be updating the astro data as they went, from public sources. Maybe not every port, but at any of them with a decent starport. CAN they take astronomical measurements? Sure. But it's going to take them time to get a plot good enough for a high accuracy jump.
TLDR as I see it (YTU may vary):
(1) jump to deep space
(2) take basic sightings to assure yourself you didn't misjump
(3) jump to destination star
(4) fire up the M-Drive to travel from the star's 100D to the destination world.
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MasterGwydion
Emperor Mongoose
Local references are only useful for local navigation, not for jump navigation. Local references from the departing system will only tell you where you are relative to the rest of the bodies in the system, not where you are in regard to the next star over. Your local points of reference are in constant motion both with other objects in the system and out of the system. I am willing to bet that the local points of reference won't even be used to calculate something like a jump, because how many grains of dust and their location, in My immediate vicinity, do not help Me plot of course from the motes of dust on My bedroom floor to My kitchen sink. The references that I would use to get from the dust motes to the kitchen sink would be; My bed, the bedroom door, the kitchen counter near the bedroom door, the refrigerator, and the kitchen sink. Each of those points gives Me 3-D coordinates and a vector that will help Me navigate to the sink. Having every mote of dust within a millimeter of My departure location mapped out, does not help with this except as to make Me aware of things that might precipitate Me out of jump.
MasterGwydion
Emperor Mongoose
I can literally measure angular separation with My $200 backyard telescope that I bought the kids. It even has a function that allows you to select 2 stars and it will give you the angular separation between them. I can align it to one star and then look up the coordinates of another star on the internet and type that into the telescope. The telescope goes right to those coordinates and there is the star. I got those coordinates from the internet. If My telescope can do that, you don't think sensors and computers from the 53rd century can do much, much better than that?
I can determine the angles of up to 1 degree of accuracy over a several mile range with a few sticks and some string to get the sight lines right. Then do a few calculations with circles and arcs using the sticks and strings to do the calculations. That is not bad for not using any technology.
Simple rule of navigation. Use the biggest, most obvious reference points first. This will also usually be some that are the farthest away. For every datapoint you compare to your map, your location becomes more accurate.
Remember, most ships just take a snapshot of the light sources 360 degrees around the ship and use these millions of datapoints to compare to the data that every ship carries which was put together by specialized survey vessels. The surveys have already been done. You do not need to redo them every jump.
CordwainerFish
Emperor Mongoose
Offhand I would expect the calculation to be O(n²) in the number of stars you shoot - not unmanageable, and trimdownable because you can treat far, bright stars as being at infinite distance. And far from errors compounding, you would do a least squares regression to reduce error.
MasterGwydion
Emperor Mongoose
Unless I am mistaken, Deneb is almost always used as a calibration point due to the fact that it is visible from pretty much everywhere, including Terra where it is the 19th brightest star in the night sky. Deneb is behind the claw, a long way from Terra, but still shining bright. Makes sense to use as a Calibration Point if it is easily visible from around 200 parsecs away.
