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Jumping in too close to the planet

This grows from a discussion with my players on Saturday night. What would happen if a 200 ton trader jumped and came out of jumpspace a few hundred or thousand feet above a city on an Earthlike planet?

Any ideas as to what the consequences would be for those in the city?
 
Most common interpretations of the rules say that you can't do that. Once you hit the 100D limit of the planet (or the star, if the planet's 100D limit is inside the star's 100D limit) you will immediately precipitate out of jump. (This also prevents you from precipitating inside any other object.)

The real question is what happens if you enter jump a few hundred feet above the city. Or directly from the landing pad. Or while inside the highport docking bay.
 
It can't, according to Traveller canon, because it is precipitated out of jumpspace as soon as it crosses the 100D limit.

Interesting question though ;)

If it could happen then I would have a huge sonic boom and shockwave like a small explosion, say equivalent to the ship's displacement in tons of TNT. Not to mention the pretty light show
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That depends on your adherence to the rules, and maybe which set even.

I'm pretty sure that the simplest answer is it can't happen. A ship will ALWAYS precipitate out of jump at 100 diameters, so that would be some 1.28 million kilometers at the closest for an Earth type (i.e. size 8) world.

Now if you want to ignore that then you have to decide if your traveller universe (ytu) jump drives are flash or not. By that I mean when a ship emerges from Jumpspace is there a big release of energy or not. If not then there is likely to be minimal real effect*, except the panic as the ship's collision alarms sound and the planetary defense grid jumps to high alert
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* hmm, just how big a thunderclap would 200 tons of displaced air create? would there be significant thermal effects too? maybe it would spawn a major storm system? is there a meteorologist in the house ;)

If on the other hand ytu says that jump precipitation is flashy then the city is likely to think a bomb has just exploded in the atmosphere, there will be no real damage beyond the pressure wave and huge emp knocking out the power grid and generally frying all the electronics not hardened against it. So most of the consumer electronics (though not military and iirc My Mac :D ) are going to be dead. That could be a great sales oppurtunity if the ship is loaded with the right cargo, or just a major pain for the characters if they are liable for the damages
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"The real question is what happens if you enter jump a few hundred feet above the city. Or directly from the landing pad. Or while inside the highport docking bay."

A soothing voice says, "I'm sorry, Dave, I can't let you do that."
 
I say give 'em a chance to do it. Make sure they know it's going to be all on the engineer to do it without getting them all killed, and no matter what the result, the jump drive will be slag and the power plant crippled. Upon success, allow them a controlled crash landing. Upon failure, give them a 50% chance of never leaving jumpspace, and 50% chance of blowing the ship to smithereens somewhere between the 100D limit and the planet's surface.

Ah, and of course a chance for a regular misjump.
 
Originally posted by DaveChase:
But I going to try, and you can't stop me.

Dave
:D

<edit> <see note after>

But seriously ;) this reminds me of a ponder I pondered once upon a ponder...

Why not allow and use the same formulae for exiting Jumpspace as entering? By which I mean you could plot your Jump to start at the safe 100 diameters, or less with some risks, and also plot your Jump to emerge at the safe 100 diameters, or again less with some risks. Plotting both ends at less than the safe would impose greater risks even. Maybe an extreme example would be clearer:

Our not-so-happy crew is on the run and in a panic they plot a hasty exit from the current system. They will be engaging the Jump drive as soon as they can, lets say 15 diameters (CT penalty of +5 on the misjump chance).

Not only that but the only system in range is Red Zoned and interdicted by the IN. So they need to get in nice and close to the Gas Giant and make a quick fuel skim and run again before they are caught there. So they plot the end run of the Jump for the same 15 diameters (CT penalty of +5, again, total penalty now +10).

Fortunately they are using refined fuel (CT no penalty) and the old Type S is built to take the abuse (CT bonus +2).

The course is plotted and engaged... (CT misjump chance is 13+ on 2d6 with total modifiers of +8)

The PC's are lucky (and roll a 4 + 8 = 12) and will manage to arrive very close to where they wanted to be.

Anyway, just a nutso idea I had once


Note in the example above if the roll had been 8 or more the ship would have been utterly destroyed, so it would be a very risky play, unless you allowed a bonus for the Navigator and/or Engineer, maybe +1 each if they make a skill check.
 
Or you could make a roll on jump entry (at a DM of +5) and then again for jump exit (again at +5). Fail the exit roll and they have to roll again, but closer to the planet and so at a greater penalty, until they make the roll and safely exit (but very close to the planet - effects as above), or they fail catastrophically and are destroyed (or are throw off into a really weird misjump - ref's choice ;) ).

I like the idea ;)
 
That might be a little more fair (the evil referee me says generous ;) ).

But yeah, a roll at each end, interesting idea, I likes it. I'd probably just go with one roll though, make it and you arrive where you aimed for, miss it and its off to the misjump table
 
Well, the subject came up as part of a " high-level " play by e-mail game I've been running. Essentially, a group of nobles are all in competition to be the next Duke (Thanks again to Jon Zeigler ). So we have competing Counts, Marquis, and Barons as well as some wild card players such as a terrorist group.

The game is nearly over and the terrorist player wanted to perform the action I asked about to destroy the " coronation " of the new Duke. I was wondering how this might affect things.

Certainly the subject has never come up in a "normal" level game before.

John
 
"Certainly the subject has never come up in a "normal" level game before."

Has in mine. I've allowed jumping from within an atmosphere (auto misjump, drive damaged), but on the ground or in a bay would be...spectacularly fatal. Which is why the computer won't let you.
 
In the OTU you can jump out from anywhere inside the 100D limit (with increasing chance of misjump/catastrophe as you approach the planet), but AFAIK there's no way to jump IN closer than the 100D limit - it's a universal cut-off, it automatically precipitates you out of jump at that distance if you cross it.
 
I'm pretty sure that the simplest answer is it can't happen. A ship will ALWAYS precipitate out of jump at 100 diameters, so that would be some 1.28 million kilometers at the closest for an Earth type (i.e. size 8) world.

Now if you want to ignore that....
you have to. if matter precipitates jump exit then crossing debris-littered interstellar distances could get very dicey.

I've always said you can jump from or to wherever you want, but inside a 100d limit of a significant matter concentration there can be consequences - jumping into a 100d limit usually results in damage to the drives. other possible consequences are easily thought of.
 
Originally posted by flykiller:
</font><blockquote>quote:</font><hr />I'm pretty sure that the simplest answer is it can't happen. A ship will ALWAYS precipitate out of jump at 100 diameters, so that would be some 1.28 million kilometers at the closest for an Earth type (i.e. size 8) world.

Now if you want to ignore that....
you have to. if matter precipitates jump exit then crossing debris-littered interstellar distances could get very dicey.</font>[/QUOTE]Well I suppose I could have qualified that. I always imagine it implied "A ship will ALWAYS precipitate out of jump at 100 diameters of anything bigger than the ship."

Interstellar debris is not going to be an issue for even the smallest Jump capable ship, and the odds of crossing paths with something bigger are, well, astronomical ;)

Space is big, I mean really, really BIG! And its mostly empty, even within the little concentrations around stars. I only hate Star Wars for one thing, perpetrating the myth that asteroid belts are high concentrations of lots of big rocks whizzing around with just enough room to fly a ship through IF you're a decent pilot. I even mostly forgive that because of Solo's response to C3PO
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Back to the topic at hand, if you are aiming for a gas giant you could come out dangerously close to one of its moons, and if your vector was wrong...
 
Hey Dad, I just did some major hacking into the computer jump program and tightened up the code. Now we can get our jump coordinates faster and get closer to our target destination.

Great son. Just think of the money we will save on fuel. By the way, how did you get the program to calculate faster?

I just change the distance to mass number of 100 to 1. Boy you should see how fast the program runs now. Here watch.


Nooooooooo, don't push that button

(of course our story ends with a bang. ;)


Dave
 
Well, its come up in my " normal level " games a million times over the 18 yrs I've been doing the game about jumping OUT of system within 100d....just never IN within 100d.

I didnt really want him to kill everyone, but I couldnt come up with what I thought was a decent enough answer as to why you couldnt.

I'm still not clear as to why you couldnt though. Do we mean to say that large objects will pull you from jumpspace? If so, this means I've totally misunderstood jumpspace. I thought you were entering a different " dimension " ( universe, reality, what have you ) and the drive put you in and it took you out. So I'm not really clear as to why you couldnt come out anywhere you wanted...horrible consequences or not.

Or have I totally misunderstood jumpspace lo this many years?

John
 
Originally posted by Sigg Oddra:
Back to the topic at hand, if you are aiming for a gas giant you could come out dangerously close to one of its moons, and if your vector was wrong...
Yep, splat BOOM! But then that's why I still insist on the legal requirement for commercial traffic to execute the standard zero vector maneuver before engaging the Jump drive. I also impose space lanes for traffic, insystem and jumpways, with widely seperated outgoing and incoming vectors so you don't risk running into someone going out. At least in theory and practice. Private ships usually abide by the same rules of space for safety and to avoid (aw what the heck, it is Star Wars Day) Imperial entanglements.

Naturally the Empire, er Imperium ;) can go where ever they please :D
 
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