Proneutron
SOC-13
Nope, outside star 100D limit and w/o jump masking and shadowing there are no faster lanes. Work it out on paper and you'll find there is no such thing
CT Only: Big Far Trader (Type R2)
- Thread starter Grav_Moped
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Nope, outside star 100D limit and w/o jump masking and shadowing there are no faster lanes. Work it out on paper and you'll find there is no such thing
Planets do, however.
Fine. 3 turns in Mayday.
Funny thing, done right, there will be little a merchant can do when arriving. They very likely may be arriving with a velocity that requires much of their deceleration to arrive at the target world. They jump in, spin around, and burn to decel, at the end of which they arrive.
The nuance of this is simply that the pirate can ask all they want, but the ship probably doesn't have much margin to actually cooperate.
"Heave ho, or we'll fire!" "We are heaving ho as fast as we can! But we'll be in orbit by the time we stop."
100D on typical worlds is not that big of space given the drives that these ships have.
Proneutron
SOC-13
From what is says about jump travel jumps are usually entered at low velocity relative to the system they are leaving. Probably for exit accuracy as jumps are plotted point to point in space.
That's my take on it. There's a "best practice" exit point and resulting arrival area for each world pair. It's not compulsory, and in a universe with cheap delta-v it's certainly not going to provide a huge benefit, but it'll be preferred unless a ship operator has good reason to avoid that route. At the very least, it's the path that flight planning software will generate by default.
AnotherDilbert
SOC-14 1K
I agree that would be the fastest route, but canon tells us that that is not how civilian ships generally do it (without specifying a reason).
For safety reasons, I'd figure that standard procedures are to do a "running Jump" on the outbound leg, but arrive mostly stationary relative to the destination. "Mostly" stationary, because you'd want a slight vector toward the destination world. Tha's because if something went wrong with the power plant or maneuver drive, you'd eventually drift within range of rescue. Coming in hot leaves potential rescuers with less time to detect and intercept.
The other thing is that if there's enough relative velocity between origin and destination, it'd be necessary to do both a "running Jump" and accelerate toward the destination on jump exit to have enough time to match velocity.
If they're diverging, you jump from the "near side" of the 100D sphere to the "near side" at the destination. If they're converging, you jump from the far side to the far side.
The "perfect" jump arrives "in front" of the target planet, leveraging the 100D to coalesce you out of jump, with a vector targeted towards the destination world.
Specifically, done right, you arrive at 100D aiming straight at the world with just enough velocity to burn off safely and achieve orbit. All of this can be done (given enough running room) in the source system before jump (this is where the jump lanes come from, ships setting up destination vectors for arrival while transiting to 100D), then it's Jump Window lotto that gets you there at the right time. You have ~16 hr window that the planet is carving through space to leverage.
If you're early, then you arrive outside of the 100D, if you arrive late, you arrive basically smack in the 100D, but coalesce out of jump at the edge 100D boundary. The only question there is "which edge", arguably it would be the LOS edge if you drew a line from source to the destination. So, if your source system is trailing the destination planet, you would likely end up "behind" the planet and have to catch up (remember, it's only trailing for a quarter of its year, it has to come around sometime). Thus, it's probably better to overshoot initially so if late you still avoid the 100D, but arrive "in front" of the planet.
If you're playing with jump masking and shadowing and the like, then you may not be able to arrive at the leading edge if you're coming from behind the planet.
But this is all stuff the Navigator noodles out on his HP-99 RPN calculator with "Space Nav" module.
Specifically, done right, you arrive at 100D aiming straight at the world with just enough velocity to burn off safely and achieve orbit. All of this can be done (given enough running room) in the source system before jump (this is where the jump lanes come from, ships setting up destination vectors for arrival while transiting to 100D), then it's Jump Window lotto that gets you there at the right time. You have ~16 hr window that the planet is carving through space to leverage.
If you're early, then you arrive outside of the 100D, if you arrive late, you arrive basically smack in the 100D, but coalesce out of jump at the edge 100D boundary. The only question there is "which edge", arguably it would be the LOS edge if you drew a line from source to the destination. So, if your source system is trailing the destination planet, you would likely end up "behind" the planet and have to catch up (remember, it's only trailing for a quarter of its year, it has to come around sometime). Thus, it's probably better to overshoot initially so if late you still avoid the 100D, but arrive "in front" of the planet.
If you're playing with jump masking and shadowing and the like, then you may not be able to arrive at the leading edge if you're coming from behind the planet.
But this is all stuff the Navigator noodles out on his HP-99 RPN calculator with "Space Nav" module.
Proneutron
SOC-13
Probably not. The planetary authorities wouldn't want ships arriving with a vector that would result in a crash into the planet in event of power failure.
Most likely would require a vector that paces the planet (a parallel course to the planet's stellar orbit) at the 100D limit. That way you don't have to kill any speed but simply traverse the 100D limit with the usual accel/decel maneuver.
More specifically, as a general safety rule, once you start your approach -- either after breakout or as part of a planned post-breakout trajectory -- you ought to be heading in the direction of a hyperbolic flyby of the planet, not a direct collision course with it.
There are no routine direct planetary approaches, except by attacking hostiles intending to launch ordinance.
This is for the peace of mind of the folks on the ground: should your rickety old tramp trader of dubious provenance suffer drive failure during the approach you will glide past the world ballistically, attempting repairs while the planetary navy is perhaps organizing a rescue flight, rather than find yourself being pulled down the gravity well toward an uncontrolled impact, destined to crater on the surface and/or be pulverized by the planetary defenses on the way in as they attempt to minimize the damage you are about to cause.
But then again, you probably want your Jump exit vector aimed directly at the planet. Arrival time and location are variable enough that this will ensure that you miss the planet entirely. 
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But then again, you probably want your Jump exit vector aimed directly at the planet. Arrival time and location are variable enough that this will ensure that you miss the planet entirely.
Heh.
Just remember that if you breakout relatively stationary with respect to the target world, it will begin accelerating you toward itself immediately and relentlessly.
And it won't even charge you for the service.
Proneutron
SOC-13
Darwinism. For those astrogators that forget about gravity wells
At 100diam, the acceleration is rather slow. Sluggish, if not slower. I'd worry more about life support running out, or old age, as a WAG.
If you arrive "stationary" in "front of" Earth, you have at best 11 hours before the bowling ball comes for the pin.
The points about the vectors are noted, but the fundamental outcome is that there are better arrival vectors than others, based on the dynamics of the system, and pilots and navigators, as a general rule, will strive to leverage those more efficient routes.
Condottiere
SOC-14 5K
Suns do tend to throw large shadows, and if a bunch of them tend to line up inconveniently ...
VTOL is a non-starter if you don't have enough thrust against local gravity. However, if you have a streamlined space-plane or lifting body style hull capable of generating lift and flying under power, you could take off and land like a conventional aeroplane with less thrust than surface gravity. If you have enough power to get it to speed and altitude then an orbital insertion burn with less than 1G is quite possible, although you have to get your takeoff trajectory right.
Landing is also possible in the same way. Traveller ships have essentially unlimited delta-V, so you can de-orbit and slow down to a reasonable speed and avoid cooking your hull with an atmospheric braking manoeuvre (this is called powered/unpowered re-entry IMTU). With a streamlined hull capable of controlled atmospheric flight you can land on a conventional runway.
I may have learned this from playing Kerbal Space Program.
This was a major oversight in the original rules, as LKW once noted.
IMTU, I just flip the m-drive from thrust mode to antigrav mode and gently float down from orbital altitude at air/raft speed.
Con: It takes several hours to work your way down to a soft landing.
Pro: Technically, you do not need streamlining (air/rafts are decidedly unstreamlined), so the brave can land pretty much any hull.
Launches and Free Traders really ought to have been 2-G from the git, though.
Proneutron
SOC-13
What about a high G planet with no atmosphere?
Proneutron
SOC-13
No need to do it slow. If the anti-grav produces enough "thrust" to gently lower you down you just drop free fall and turn on the anti-grav high enough up to land ok.
High-G planets almost always have atmosphere, at least the way Traveller worldgen works. Average atmosphere for sizes 8-10 are going to be 8-10 respectively. Minimum possible for size 8 is "trace" (atm 1) and that's 1/36 odds.
