## Question on the 100D jump limit

Discuss the Traveller RPG and its many settings
phavoc
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### Re: Question on the 100D jump limit

Well, under the combat rules you can be moving at .1C, jump, then re-enter realspace, and pop! Encounter and all speeds are set to zero.

I don't think these things are taken into account when writing rules/articles. If it sounds cool, write it! Who cares if it doesn't make sense or breaks the rules!!
Sigtrygg
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### Re: Question on the 100D jump limit

Nope.
If you are moving at 0.1c when you enter jump you exit jump with that velocity.
when a ship exits jump it retains the speed and direction that it had when it entered jump
If MgT combat rules say something different then they are wrong - or rather do not apply to the OTU as defined by MWM.
AnotherDilbert
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### Re: Question on the 100D jump limit

Sigtrygg wrote: If MgT combat rules say something different then they are wrong - or rather do not apply to the OTU as defined by MWM.
I wouldn't say wrong, just highly simplified. It doesn't do speed or acceleration at all just range, slightly more detailed than LBB5.

To be completely accurate it would have be a continuous 4-dimensional vector system without abstractions such as turns.
phavoc
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### Re: Question on the 100D jump limit

Sigtrygg wrote:
Fri Mar 22, 2019 9:04 pm
Nope.
If you are moving at 0.1c when you enter jump you exit jump with that velocity.
when a ship exits jump it retains the speed and direction that it had when it entered jump
If MgT combat rules say something different then they are wrong - or rather do not apply to the OTU as defined by MWM.
I agree with you. I was just stating what the rules said. And what Miller wrote back in the original JTAS (and is being re-printed).

On the one hand it's not a bad idea. However it makes gaming piracy nigh impossible. Ships could not be intercepted inbound and outbound would be just as hard. Requires lots of hand-waviums (much like dogfighting in space ala aircraft or star wars).

Which is why I've house ruled that jumping under velocity imparts a bigger margin of error in your jump. The faster you are going the bigger the error of margin. Which means most ships come to a halt (relative to their departure system) and then jump, which means they can pinpoint their arrival (barring a misjump or bad navigation) within about 25,000km. That also helps the arrival system, busy ones at least) to provide specific arrival zones for ships to minimize collisions and accidents. It also makes encounters more possible and less hand-wavium like the existing rules have.
Moppy

### Re: Question on the 100D jump limit

Another problem with preserving velocity after a jump is that I can accelerate a projectile for a year (using a tug with tankers) in a neighboring system and then jump in with the projectile at some huge fraction of light speed.

I don't recall seeing anything the the TL 15 arsenal that can stop that, at least, no-one builds a million-tonner loaded down with repulsors. There's no missile more powerful than a nuke - which probably doesn't work since we build nuclear bunkers inside mountains - and even if you had some kind of super mass driver, the fragments would probably still hit the planet.

edit: I think your best chance is to fly up to it and (mis?)jump on purpose, to try to take it with you. However I thought most ships have conformal jump grids and you need a "bubble" jump field like a tug might have.
Reynard
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### Re: Question on the 100D jump limit

Maybe it's an OTU thing but everyone from terrorists with a grudge to empires have not once caused extinction level attacks on any system even knowing it can't be stopped let alone traced. You figure at least the K'kree would do that to worlds of meat eaters. Grab a rock, strap a motor to it with just enough fuel to get it to final velocity and let those brave people sacrifice themselves for the cause by riding it on course to jump entry. Traveller should be littered with dead or dying planets over the millennia.
AnotherDilbert
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### Re: Question on the 100D jump limit

Moppy wrote: Another problem with preserving velocity after a jump is that I can accelerate a projectile for a year (using a tug with tankers) in a neighboring system and then jump in with the projectile at some huge fraction of light speed.
There is a problem with aim. According to JTAS#24 jump emergence has an inaccuracy of about 30000 km per Pc jumped, IIRC. You can easily miss a even a planet.
Moppy

### Re: Question on the 100D jump limit

I can still jump in and do a missile flyby with "can't catch me" speed. It's probably like the SR-71 flying over Soviet Russia. They had no plane or missile that could reliably catch it.

If you have to hit the planet with your hull, 30,000 km per parsec might not be that far out at 100D. You can jump further out than 100D if needed. Sadly, needs math to model it. edit: 3 diameters per parsec inaccuracy, up to 12 diameters out at 100 diameters for jump-4. Thinking about it more, a year's acceleration would be a waste, but several weeks may work and allow you to steer it.
Condottiere
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### Re: Question on the 100D jump limit

A kamikaze jump rock is where as one shot jump drive makes sense.

As for jumping while moving, it's where I rationalized one of the reasons starships come to dead stop being that you want to transition as close as possible to the point that you used in the astrogation calculations.
phavoc
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### Re: Question on the 100D jump limit

Aiming a c-fractional missile isn't a big deal. If you arrive far enough out you can make your adjustments and still be a long way from detection. Though this is where the introduction of new equipment, like the jump detector, makes for tricky, if nigh impossible, putting the equipment into the game without breaking things. In this case if you dropped your planet-busting rock 200 AU from the target, and are coming in above or below the plane of the system eliptic, there's no traffic or other interference. It's very easy to make course adjustments to hit your target.

Or you arrive 400 AU (or farther) out and prep your rock and let er rip from the target system. Same effect.

I agree with Reynard - this is simply not something that happens. C-fractional attacks on targets seems great on paper, but in reality everyone would be doing it to everyone and all that would be left would be orbital debris fields and lifeless worlds. Since there have been major wars between all the various entities and all the planets are still there and inhabited (mostly), it's not something that is practiced by any of the races for warfare. That would include Imperial - Zho wars. Otherwise Jewell would not remain as a hardened fleet base.

Of course, to be totally fair, game history <> what might happen in reality. The best we can do is postulate that effects of what it COULD be. But, to also be fair against the idea, we are also stating what could be the result of such an act by the major powers. So that brings us full circle to the MAD doctrine that has kept the world from having an all-out nuclear war. Yay for McNamara and his loonies in the Pentagon. They had some doozies, but codifying this one seems to be holding steady.
Moppy

### Re: Question on the 100D jump limit

Governments may indeed be under some kind of "MAD" treaty but what about "the lone nutter"?

Barringer crater (https://en.wikipedia.org/wiki/Meteor_Crater)

This crater is 1.2km meters (0.7 miles) diamater, estimated to be made by a 50 meter (150 foot) asteroid impacting at 13 km/sec - about 20 minutes acceleration at 1 g.

The approximation I used for this is: 1g = 10 m/s. 1000 m/s = 1 km/s = 100 sec. 13 km/s = 1300 seconds. 13x3=39. 1 hour is 3600 seconds.

edit: 50 meter rock is equivalent to a 4700 dton planetoid.

It doesn't happen in Traveller, but no-one knows why. It's probably for the best. Space engines or weapons would probably have to be very different otherwise if one had to deal with that.
phavoc
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### Re: Question on the 100D jump limit

Probably works the same way nukes do today - though there is a big difference in that suicide ships would be available to anyone to try such a tactic. At least with nukes ya gotta build them, which takes a bit of technical know-how and access to fissile materials.

More than likely it's probably the same thing that stops nutjobs today from being mass killers - at least on the scale we are talking about with plowing ships into planets. We've seen some big attacks over the decades. Remember the Tokyo sarin attack in 1995? Everyone remembers the Twin Towers in 2001. Don't forget the Guy Fawkes and his attempt to blow up parliament in 1605.

Who knows, there could be attacks but the government writes them off as accidents to stop people from being able to capitalize upon their notoriety.

As far as the rock into an atmosphere, there's more to it than just accelerating one and hitting the planet. As we've seen they can bounce off, disintegrate, or explode in the upper atmosphere. There was the recent one in Siberia that blew up. And don't forget about Tskunga (sp?) in the early 1900s.
paltrysum
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### Re: Question on the 100D jump limit

phavoc wrote:
Tue Mar 26, 2019 6:37 pm
As far as the rock into an atmosphere, there's more to it than just accelerating one and hitting the planet. As we've seen they can bounce off, disintegrate, or explode in the upper atmosphere. There was the recent one in Siberia that blew up. And don't forget about Tskunga (sp?) in the early 1900s.
Both of which were most certainly Ziru Sirkaa attempts to destroy us before we become the Solomani.
My published Traveller adventures on DriveThruRPG:
https://www.drivethrurpg.com/browse.php ... %20Griffen
AnotherDilbert
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### Re: Question on the 100D jump limit

Moppy wrote: The approximation I used for this is: 1g = 10 m/s. 1000 m/s = 1 km/s = 100 sec. 13 km/s = 1300 seconds.
Your calculation is correct, but started off problematically.

1 g ≈ 10 m/s².

Gravity is acceleration, hence m/s².
Anything measured in m/s is a velocity.

Otherwise you are correct: 13000 m/s / 10 m/s² = 1300 s ≈ 22 minutes. (Note that the units match on both sides of the equal sign, as they must.)
Condottiere
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### Re: Question on the 100D jump limit

There's probably a speed governor on most commercial ships; disabling it would take time and effort, so it wouldn't be a spur of the moment thing, but would reuire planning and commitment, since I would tie this to the ship's transponder and engineering, which would send out an alarm and disable the ship simultaneously.
BigDogsRunning
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### Re: Question on the 100D jump limit

The speed governor idea doesn't work.

Travel times in-system have always been given as acceleration/deceleration time, with no coasting assumed.

If you really wanted to do something like this, you would want a heavily armored freighter of some sort (for structure), loaded with metallic ores, refined metal, or something similar with high density to give you enough kinetic energy and structure to not simply vaporize when hitting the atmosphere. A warship might not even have enough structural integrity to keep from breaking up, although a heavily armored superdense hull might just be enough.
Condottiere
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### Re: Question on the 100D jump limit

Acceleration would cut once you hit a certain speed, and then you coast.
Moppy

### Re: Question on the 100D jump limit

Condottiere wrote:
Thu Apr 04, 2019 1:51 am
Acceleration would cut once you hit a certain speed, and then you coast.
That would invalidate existing material about travel times which assume hours under acceleration. It only needs 20 minutes at 1 gee to get to Barringer crater asteroid speed.
phavoc
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### Re: Question on the 100D jump limit

Condottiere wrote:
Thu Apr 04, 2019 1:51 am
Acceleration would cut once you hit a certain speed, and then you coast.
That goes against common sense and all the versions of Traveller. Nothing in the game suggests the various powers are wiping out each others planets during wars.

Only players seem fixated on making things go fast and running them into planets.
Reynard
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### Re: Question on the 100D jump limit

Until they hear their favorite world was the test for the first ever to go.

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