Reynard said:
Actually that's exactly what I was referring to. Look at any Traveller star chart and there can be systems between you and your destination. The astrogator isn't just pointing the ship as the crow flies unless that is the shortest path, they are setting a series of twists and jinks all about any number of gravity bodies in their way. You're not always lucky enough to be above or below the ecliptic. So are the stars and planets at destination and you have tried to plot accordingly. A ship in jump space isn't just hanging in there, it is moving relative to our real space (which is why real space gravity still affect it) with the speed of the universe they are in. Yes, you are charting to go around the star.
Known star charts in your ship's computer are huge and complex. Once a system has been thoroughly surveyed, all significant objects movements plus the system's overall path are charted in real time and constantly updated in memory. The astrogation roll represents pinpointing the location of exit as precisely as possible even knowing every obstacle waiting for you. Yes, the computer knows what side of the star it's on.
If that's how it works in your scifi setting then great. But that's not how it works in the OTU, and that's not how jump drive works - in that case, I'm sorry but you're wrong on all counts.
First, you don't understand how jump travel in the OTU works - the astrogator IS pointing the ship as the crow flies. They aren't "jinking around" anything. The ship jumps out, travels in a direct straight line to the destination, and exits jumpspace at or beyond the 100D limit. The ship by definition cannot maneuver in any way while in jumpspace. All of this has been described and argued about many times in Traveller's history.
And arguably gravity isn't even what's affecting it, since the 100D limit is defined by the
radius of an object only - so only the
size of objects along that straight-line trajectory is what matters. A neutron star may have the mass of 5 suns, but it's only about 20 km across so its 100D limit is only 2000 km despite its enormous gravity.
Also, a star in a system between the departure and destination system is still very unlikely to get in the way of the straight-line path of the ship. A star's 100D limits is of the order of a few AU radius, a parsec-wide hex is about 3 million
million cubic AU in volume. Your piddly spaceship - with a cross-section of a few hundred metres at most - is astronomically unlikely to intersect that 100D limit (or anything else for that matter, which would be much smaller than that) in that volume. The obstructing star would have to be so EXACTLY aligned with the path (even the tiniest of fractions of a degree off and the path would miss the obstruction entirely) that it's essentially impossible.
I think the reason that people keep trotting out arguments like this on Traveller boards is largely because they have no idea how huge space is and how tiny stars, planets, and spaceships are. It's a myth that needs to go away. If you want an example that closer to home, take a look at that printed Traveller star map. The systems aren't really the size of those honking big black circles in the middle of 1-cm wide hexes. There are about 205,000 AU in a hex, so even just assuming it's flat, 1 AU is 5e-8 m on that scale. Most stars are about a hundred times smaller than that, so conveniently we can say that 1 AU is about the size of their 100D limit - so on this scale a star's 100D limit is about the same size as
a small virus. So, on your printed star map, you're drawing an infinitesimally thin line (smaller than the cross-sectional area of a
quark on this scale, if you must know) between something the size of a virus that could be located anywhere in one hex and another thing the size of a virus that could be located anywhere in another hex (up to 6 hexes away, at that). And you're saying that there's a significant chance that there's another virus-sized thing in the printed hexes between them that intersects that exact infinitesimally thin line? Really?
As for the ecliptic, you usually would be extremely lucky to arrive even close to the destination system's ecliptic plane. Think about it - it's a plane where the planets orbit in a system, one plane out of an infinite number that can potentially be oriented in any angle around the star relative to the incoming ship. Systems are above, below and alongside eachother in space and oriented randomly relative to eachother too. If you want to go to Polaris from Earth, you would be travelling at a high angle to our Solar System's ecliptic plane. When you arrive at Polaris, its ecliptic plane could be oriented at any given angle. Maybe the star's equator and system would be oriented edge-on to us, maybe it's face-on, most likely it's some other angle in between. Either way, your ship's path is still astronomically unlikely to hit anything on the way in.
Again, for all intents and purposes there are no obstacles within a system that are smaller than stars. Companion stars within the system (say 1-20 AU from the primary) could get in the way, yes - because they'd be big relative to the system. But generally the stars' 100D limit is the only thing that matters.
And I know it's tempting to start writing and arguing the point, but don't. Just think about it - draw it out if necessary - and you'll come to understand why I'm saying that you're wrong.
