Navigation 210: Star Vectors

[Maccat]

OK, may be wrong here but as I recall, when you jump you keep the velocity and heading you have when you jump. Hence ships accelerating out and then deccelerating to be at low velocity when jumping. This is the infamous 10/100D limit, only-go-out-to-it and jump to the other worlds 100d limit.

But that "no velocity" at the 100D limit is actually still at (the planets) orbital velocity. You are goin round that sun pretty quick. And that Star, well it is goin at an even greater velocity. *Both* of which are different than the velocity and direction of the star you are travelling to, as well as whatever planet's 100D limit in it's orbit around the sun.

So if we keep our vector on jumping out when we re-enter normal space, wouldn't trying to match that other star and other orbit's combined vectors be the goal? And to reach that, you're gonna need a hard burn, especially at 1G, very likely being something far different from just putting out to the 100D of the world and blip you're fine.

Or is there some easy out I'm missing? This would apply to in-system jumps as well, we jump from 100D limit earth (29.8km/s) to 100D limit Pluto (4.7km/s). Heck of a velocity vector! say 25.1km/s though depending on the orbits it could be added, subtracted a real mess! LBB2 dimenions, turns, is a vector um 25100/s .251m/s 251cm/s 1000sec turns, 25100cm vector, 1G 1 turn burn being 10cm ! and that's just in-system.

So far from being a useless crew member who only has to work just that lil bit to get the jump drive working, maybe the navigator is trying to solve 13+ body time (and space!) dependant orbital calculations for two systems simultaneously all the while tryin to work in some vector that works for it, which likely *could* take a week!

Any thoughts/comment most appreciated!

 

[BlackBat242]

Yep... the navigator is a very vital post.

Speaking of posts, we did this "velocity/heading and jump drive" conversation for several pages not too long ago...

http://www.travellerrpg.com/CotI/Discuss/showthread.php?t=18400

http://www.travellerrpg.com/CotI/Discuss/showthread.php?t=17317

http://www.travellerrpg.com/CotI/Discuss/showthread.php?t=16014

 

[Icosahedron]

As you have noted, Maccat, the Preserved Vector Theory doesn't really hold water. It's just another 'seemed like a good idea at the time' canon proclamation.

The only way to make it work is to have vectors relative to the local gravitational centre at both the origin and destination of the jump, and with any reasonable margin of error applied, a zero vector probably makes more sense than any other.

IMHO, of course.

 

[mike wightman]

Unless you want to do a whole load of very complicated math then just assume the magic nature of the jump drive deals with stuff like this.

Or assume that the in-game navigator does indeed solve these problems.

 

[rancke]

Or assume that the in-game navigator does indeed solve these problems.

That's what I do. The canonical description is, IMO, a game artifact, a simplified procedure that approximates (very loosely) the calculations the astrogator[*] really performs. In "reality" he actually calculates the vector that best approaches the vector of the destination world, in an attempt to reduce the effects of the jump uncertainty. But what gamer wants to waste time doing that sort of calculations for real?



[*] Yes, I know. But really, he guides ships between stars, not across piddling planetary ponds. No doubt, while learning to astrogate, he learns how to solve those kindergarden problems navigators face, but learning to navigate in no way qualifies a man to perform astrogation. IMO, of course.


Hans

 

[Maccat]

Heh if the vectors hold, the anti-piracy 100d limit hopping with swap-out cargo/fuel pod thing gets um, put to sea as it were <s>. I don't neccessarily subscribe to it being that way, but *do* kinda like if you're travelling between stars, to maybe actually have to do more than just pop up above the atmnosphere and blip over 100d out at your destination. Having to do vector burns like this at least gives some sense of *you're going somewhere far away*, allows for dramatic chases, stuff like that. You don't do it, you'll have a longer burn at the arrival to synch it up (navigator did a bad calc, jump is fine but now a big burn needed to synch up with the destination) heh gives the pilots more to do as well!