Citizens of the Imperium

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Supplement Four September 12th, 2017 09:10 PM

Jump Tunneling
This variant House Rule is inspired by the interesting things experts can do beyond what is normally thought is possible. In thinking about Han Solo making it through a planetary shield and coming out of hyperspace in the atmosphere of the world (from The Force Awakens), and the scene in Rogue One where the Rebel ship jumps to hyperspace from near the planet's surface. Both are considered impossible events that happened in spite of being impossible.

What is Jump Tunneling? It's a very dangerous attempt to use a jump drive to travel farther than the drive's designed rating.

If you have a vessel with a J-1 drive, and if you have a very qualified (or lucky) Engineer, you can push that drive to make a jump of 2 parsecs or farther through the magic of jump tunneling.

Let's say that you're on a standard Type A Free Trader and you are "land locked" in the Aramis Trace. You can only travel to the few worlds in that cluster of stars that average one parsec distance from each other. If you want to break out into the larger subsector, you can't, unless you get tanks of extra fuel or you replace the drive with a one that is capable of J-2 or more.

In a desperate situation, the Engineer can attempt to re-calibrate the drive for jump tunneling.

Mumbo-Jumbo: When an Engineer re-calibrates the ship's Jump Drive for jump tunneling, he disengages safety protocols and tunes the drive's operation so that it goes beyond safety margins.

It takes quite a bit of energy to rip a whole in normal space allowing the ship to pass into jump space. Different distances are accomplished by accessing different "tunnels". It takes a lot more energy to access the J-2 tunnel than it does the J-1 tunnel, thus, J-2 drives require more fuel.

But, it is easier to access the J-2 tunnel if you are already in the J-1 tunnel (and so on).

Jump tunneling works on the notion that the J-Drive is configured to delay the complete use of energy until after the ship enters the J-1 tunnel and then enters the J-2 tunnel (or beyond). If successful, the a ship with a J-1 Drive will move 2 parsecs while only using the fuel required of a J-1 drive.

Higher jump tunnels are possible with associated greater risk.


In order to pull this off, the required throw is 15+. Engineering skill provides a +3 DM per level of skill.

If the roll is not successful, then the Engineer is not capable of recalibrating the drive. That specific engineer cannot attempt recalibration on that particular drive until the Engineer earns a higher level. See the Experience rules.

If the roll is successful, then the Engineer has successfully recalibrated the drive, and the player playing the Engineer will tell the Ref which jump tunnel the Engineer has recalibrated the drive to access.


When the ship jumps to its new tunnel, the GM will secretly roll 1D. If the result is equal to the jump tunnel number or less, then there is a problem. If the roll is higher than the jump tunnel number, then the ship makes the new jump with no problems.

Failing a Jump Tunnel Throw

If an Engineer successful recalibrates a J-1 drive to make a two parsec trip, then the ship will access the J-2 tunnel during jump. The Ref throws 1D, and that roll will indicate a fail if the roll is 2 or less. A 3 or better indicates there is no problem.

The Problem.

If the Ref's throw indicates a problem, the roll on the Space Combat Hit Locations chart. Replace result 6 (Hull) with Drive Failure, as if the ship used unrefined fuel an a Malfunction was indicated. Replace result 10 (Turret) with Mis-Jump.


Teev is the Enginner aboard a Type K Safari Ship (capable of J-2), and since the crew is poaching endangered species from a Red Zone world, the captain has ordered Teev to recalibrate the J-Drive for a three parsec journey.

The roll needed for Teev to recalibrate the J-Drive is 15+. Teev has Engineering 3, so he is +9 on the throw: 2D +9 for 15+. Or, 2D for 6+.

Teev rolls and gets a 7. He has successfully recalibrated the drive. Access to the J-3 tunnel is possible...

But at what cost?

We won't know that until the ship actually jumps.

The jump is made, and the ship makes it into the J-3 tunnel. The Ref throws 1D. A 3 or less means that complications will ensue. A 4+ means that the trip will come off without a hitch.

The Ref rolls this in secrecy. He gets a 3, meaning that a complication arises.

The Ref then rolls 2D on the Starship Combat Hit Location Chart to determine the nature of the complication. A 6 is rolled, which means, when the ship re-enters normal space at the destination, all of the drives blow. The M-Drive, J-Drive, and PowerPlant are all completely dead. Batteries will provide life support and minimal power for 1D days. Throw 10+ per day, + Engineering Skill, to jury-rig repairs.

rhialto September 13th, 2017 08:33 AM

Interesting: I like it. Just curious if this was at all inspired by Stars Without Number's option to "drill faster"?

coliver988 September 13th, 2017 09:47 AM

I like it as well - have to remember this as an option for those tight situations.

It may be that various services gloss over this as a potential jump extender due to the high probability of severe damage. Engineers, being engineers, love to play with the back of the envelope scenarios, and there is a significant amount of informal information available.

It is also good to think about this in reverse: the players have to rescue the safari ship as it comes out of jump, its engines an expanding cloud of debris behind it. Why did the engines explode? What does the safari ship crew do? Are ship logs available to rescuers?

Garnfellow September 13th, 2017 12:01 PM

I love the idea.

Supplement Four September 13th, 2017 08:01 PM


Originally Posted by rhialto (Post 573460)
Interesting: I like it. Just curious if this was at all inspired by Stars Without Number's option to "drill faster"?

Can't say that it is as I've never cracked open Stars Without Number even in a game shop.

Supplement Four September 13th, 2017 08:18 PM

I was thinking that the failure on the GM's secret roll could result into even more damage if you rolled a "hit" for every point at which the D6 toss failed.

If you've got a recalibrated J-1, and you attempt J-3, then success happens on a 4-6 while failure happens on a 1-3.

If a 1, then roll three hits on the Space Combat Hit Location Chart.

If a 2, then roll two hits.

If a 3, roll only one hit.

On a 4-6, the J-1 ship successfully makes the J-3 journey.

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