#TheExpanse Ships in #TravellerRPG

Watching “Home” (The Expanse, Season 2, Episode 5) with the Rocinante at high-g burns got me back to thinking about the ships of The Expanse and how they could be portrayed in tabletop RPGs. I previously looked at the Epstein Drive and how it might be translated into game terms for use in Traveller RPG or Cepheus Engine or Orbital 2100.

**WARNING – Minor Spoilers Ahead**

Courtesy SyFy

Going all the way back to the first book in the series, Leviathan Wakes, the small shuttle Knight gives us some insight into the technology of The Expanse:

It wasn’t long before Alex called down, “Okay, Boss. It’ll be about a four-hour trip flying’ teakettle. Total mass use at about thirty percent, but we’ve got a full tank. Total mission time: eleven hours.”

“Copy that. Thanks, Alex,” Holden said.

Flying teakettle was naval slang for flying on the maneuvering thrusters that used superheated steam for reaction mass. The Knight‘s fusion torch would be dangerous to use this close to the Canterbury and wasteful on such a short trip. Torches were pre-Epstein fusion drives and far less efficient. (Leviathan Wakes, Chapter 3)

From the book we know that the trip covers 50,000km. Working with classic space travel time equations, we can compute the Knight is traveling at about 1.0368 m/s or just over .1G acceleration.

Later in Chapter 5 we see the Knight running flat-out at 2G acceleration. At this speed the same 50,000 km trip should take only 53 minutes, which is a bit shorter than the approximately 70 minutes obliquily stated in the book. At this point it is unclear if the 2G speed is the upper limit of the teakettle or the fusion torch at low power.

The Knight does eventually clearly light it’s torch:

“Roger that, XO. Bleeding-g burn-and-flip laid in. Angled approach course so our torch won’t burn a hole in the Cant. Time to rock and roll?” Alex replied. (Leviathan Wakes, Chapter 5)

Courtesy NBC Universal

Here we have to interpolate the fusion torch acceleration based on Holden and his apparent weight. When lighting the torch Holden weighs 500 kilos. Assuming he is an average 75 kg to begin with, this works out to almost 7G. Interestingly, from the novella The Drive we know that 7G is the instrument limit on Solomon Epstein’s ship that he installed his new drive on, indicating that the fusion torch may have an upper limit of 7G.

In summary, we can say the shuttle Knight has maneuvering thrusters (teakettle) that operate efficiently at .1G. The shuttle also has a fusion drive (torch) that can accelerate it at up to 7G.

The Knight‘s torch drive could deliver a lot of thrust, but at the cost of a prodigious rule-burn rate. But if they could save the Cant, it wouldn’t matter. (Leviathan Wakes, Chapter 5)

The missiles that are fired at the Canterbury are also very impressive:

As if in answer, six new objects appeared on his radar, glowing yellow icons appearing and immediately shifting to orange as the system marked their acceleration. On the Canterbury, Becca yelled out, “Fast movers! We have six new high-speed contacts on a collision course!”

“Jesus H. Christ on a pogo stick, did that ship just fire a spread of torpedoes at us?” McDowell said. “They’re trying to slap us down?”

“Yes, sir,” Becca said.

“Time to contact.”

“Just under eight minutes, sir,” she replied. (Leviathan Wakes, Chapter 5)

For these six missiles to cover 200,000km in 8 minutes means their acceleration has to be around 150G!

In Leviathan Wakes, Chapter 51, Holden tries to remember how fast the Roci can go:

He tried to remember the Roci‘s maximum theoretical acceleration. Alex had already flown it at twelve g briefly when they’d left the Donnager. The actual limit was one of those trivial numbers, a way to brag about something your ship would never really do. Fifteen g, was it? Twenty? (Leviathan Wakes, Chapter 51)

Courtesy solotalkmedia.com

In the episode “Home” if I caught the screen correctly it looks like the Roci was accelerating just over 17g. This again is in line with the book; and way faster than the 6g of Classic Traveller or Cepheus Engine and far ahead of the technology in Orbital 2100 where the alternative Nuclear Pulse Fusion Drive tops out at 1.2g! Compared to the Traveller RPG or Cepheus Engine universe, the ships and weapons of The Expanse are way faster and likely far more deadly too.

As late to the game as I am, I look forward to reading more of The Expanse series and seeing what further ship secrets are hidden within.

PS: The math for figuring time and acceleration is actually easy, but to help there is an EXCELLENT site at http://www.transhuman.talktalk.net/iw/TravTime.htm that does the math for you!




Traveller RPG Tech – Clement Sector Zimm Drive

Many people forget that the Traveller RPG is actually a generic system. In the years since the Little Black Books came out in 1977 the Third Imperium (3I) setting has come to define the Traveller RPG to the point that many believe that the Third Imperium is Traveller. Fortunately, Gypsy Knights Games’ Clement Sector setting breaks the 3I paradigm through a few simple changes. For a taste of the Clement Sector I strongly encourage you to download the free Introduction to the Clement Sector from DriveThruRPG to see the setting differences in the Clement Sector setting.

In the Clement Sector, the FTL system is the Zimm Drive. Instead of the standard Traveller Jump Drive that moves a ship across 1-6 parsecs of space in a week, the “Z-Drive” covers 1 AU in about 1.44 seconds, one light year in 26 hours, or 1 parsec in 84 hours (3.5 days). The Zimm Drive is limited to a practical range of  2 parsecs (actually 2.44) in 168 hours or 7 standard days. Ships greater than 5000 DTons cannot be equipped with the Z-Drive, and ships between 2000-4999 DTons have a risk of the bubble collapsing. The Z-Drive uses the same space and fuel requirements as a standard Jump-2 Drive in Mongoose Traveller (MgT).

This simple technology change actually has a great impact on adventuring in the Clement Sector. In MgT, to travel in-system a distance of 1 AU using a 1G acceleration drive will take 68 hours; at 6G the best one can do is 27.6 hours (MgT Pocket Rulebook p. 145). In the Clement Sector, a ship can fire up its Z-Drive and get there in 1.44 seconds. If one is trying to get to the outer system, in MgT at 6G it will take between 55-68 hours, whereas in the Clement Sector setting it take a mere 1.85 minutes. This forces changes in how one thinks about fuel, trade, and combat.

In the Clement Sector one can use their Z-Drive instead of Maneuver Drive to travel far distances within systems, but doing so requires a change in how to think about fuel consumption. In MgT, ships can jump less than 1 parsec, but it counts as a Jump-1 event for time and fuel (Pocket Rulebook, p. 141). Z-Drive performance in the Clement Sector can literally be “dialed” to the needed range. In my games, I added a fuel tracker for the Z-Drive which gives the ship 200 hours of “Z-Time” that can be used as appropriate. Need to get to that Gas Giant to top off the tanks? That’s going to cost you 2 minutes of gas!

The Z-Drive also changes the speed of intersystem trade. The quickest way to get around in-system is no longer a Maneuver-6 Drive, but a Z-Drive. Taken together with the Z-Drive size limits, bulk freighters are uneconomical; thus the need for smaller merchant ships is greater (i.e more adventuring opportunities).

The Z-Drive changes the nature of in-system combat compared to the usual Traveller approach. In the Clement Sector, a fleet could enter the outer system, refuel at the far gas giant, organize itself, and then “micro-jump” to the 100-diameter limit. The final approach micro-jump takes less than 2 minutes compared to several days in a standard Traveller setting. In the Clement Sector there is no need for a “long approach” battle. This has an impact on planetary defense forces which must stay within 100 diameters of the target they are protecting. In effect, non-Z-Drive become “static defense” forces whereas Z-Drive defenders become the “mobile” force.

In summary, the Zimm Drive in the Clement Sector from Gypsy Knights Games is both familiar to Traveller players and just different enough to make it interesting. The changes the Zimm Drive brings to travel, trade, and combat will require players (and GMs) to think about the setting differently – one can’t automatically fall back on the “3I way.” This is yet another reason the Clement Sector is so interesting a setting to play in.

Free RPG Day 2015 – Kiviat Patrol Corvette for MgTrav

pic1959015_t As much as I want to, I usually end up missing  Free RPG Day. In the few times I have made it into a FLGS I am already too late for any of the more desirable stuff and, not being a D&D sorta guy, usually walk away empty handed. This year I was pleasantly surprised to see GypsyKnights Games offer a free Mongoose Traveller RPG download thru DriveThruRPG.

Ships of the Clement Sector 1: Kiviat-class Patrol Corvette is an 18-page product that is the first in the Ships of the Clement Sector line supporting GypsyKnights Clement Sector Alternate Traveller Universe (ATU). It features the outstanding artwork of Ian Stead who is my favorite Traveller ship artist. It also starts off with a bit of fiction to help set the mood. In addition to the background and ship form there is the Mongoose-obligatory deck plan that, though inspirational, is once again all-but-useless at the scale printed. There is also one character described.

Pros: ARTWORK! In addition to the cover one gets a color five-view page. The background is very useful for the referee; the fiction passable.

Cons: Deckplans. The character description is given but no references to which product was used to develop it.

Overall a very useful product; darn sight better than the usually poor Mongoose items.

A big THANK YOU to GypsyKnights Games for giving this away for  the 2015 Free RPG Day. You have sucked me in and I will be looking for opportunities to get the rest of the Ships of the Clement Sector series!

Attack Squadron: Roswell – Convair F2Y Sea Dart

Convair F2Y Sea Dart (Official US Navy Photo)

ATTACK SQUADRON: ROSWELL from Zozer Games uses the Mongoose Traveller RPG engine to power a campaign set in the early-mid 1950s where the characters are part of a top secret USAF project to investigate UFOs. As the game says, think X-Files meets X-COM! Being a former Navy guy, I cannot let the Chair Force steal the spotlight, so I worked on the Navy counterpart to “Project Pounce.” Of course, I had to find a very exotic plane to use; one that “officially” had a limited history but “secretly” makes for an interesting vehicle to fight against the alien invaders. What better Navy airplane than the Convair F2Y Sea Dart, the jet plane on hydro skis?

TOP SECRET- MAJESTIC 12 ONLY – While the USAF had “Project Pounce” the US Navy also had their own UFO defense plan. It called for stationing several submarines around the globe to always be in position to respond to an invading saucer. In 1952 the US Navy has started a crash-program which will use the 95% complete Japanese I-404 aircraft carrier submarine carrying the Convair F2Y Sea Dart. Later submarines will be secretly converted along with REGULUS guided missile boats. There are even plans to build a nuclear-powered boat in the far future under the codename “SkyDiver.”

Click here for the Mongoose Traveller, Attack Squadron: Roswell vehicle sheet. ASR_Convair_F2Y_Sea_Dart.

For good background on the Sea Dart see this article at defensemedianetwork.

Starship Construction in Mongoose Traveller

ONE aspect of the Classic Traveller RPG that I love is the ship construction rules. Not only can you build a ship for roleplaying adventure but one could even build fleets of ships. The Classic Traveller adventure Trillion Credit Squadron lets players design and build whole fleets.

In keeping with Traveller technology rules, different tech levels (TL) limit what one can build. I have been searching the Mongoose Traveller (MgT) rules for rules that limit the size of ships by TL. Thanks to a discussion over on the Mongoose Traveller Forum, I finally found it. Alas, the limits are not EXPLICITLY laid out and putting it all together is not easy and requires cross-referencing not only several rules but looking across several books too.

The MgT Core Rulebook (CRB) is useful for creation of Adventure-class ships (ACS); i.e. those used by a band of adventurers. ACS are ships from 100-2,999 tons. The CRB has examples of small craft (craft under 100 tons) but no design sequence. The Spacecraft Design chapter allows creation of starships and spacecraft ranging from TL7 to TL15. Within this system, there is no limit to ship size based on TL. However, since all ships need a computer and the Model 1 is not available until TL7 (CRB p. 108) it effectively means that a spacecraft cannot be built before that TL.

MgT Book 2: High Guard (HG) expands on the ship design sequences in the CRB and introduces Capital Ship (over 3,000 tons) and Small Craft design sequences. In typical form for Mongoose Publishing, one must also make sure they have the latest errata to correct the published book. The errata in this case is key because it clarifies the Computer Table on pg. 65 which gives us our ship size construction limits.

The Computer Table on p. 65 includes the columns “Ship Size Minimum” and “Jump Maximum.” The errata clarifies that the designer is to “select the core computer based on the size of the ship or jump requirements, whichever is higher.” Looking strictly at the ship size portion gives us our ship size limits by TL (Read TL; Computer Core Model; MAXIMUM ship size that can be built using this model):

  • TL 9; Core/3; 3,000-5,000 tons
  • TL10; Core/4; 5,001-10,000 tons
  • TL11; Core/5; 10,001-50,000 tons
  • TL12; Core/6; 50,001-100,000 tons
  • TL13; Core/7; 100,001 tons and up

Later computer models add jump capability and computing power but do not affect the size of a ship that can be built. So if one wants to build a 75,000 ton cruiser, one must use AT LEAST a Core/6 computer which is not available until TL12.

Note that ships of 100-2,999 tons can be built at any TL from 7-15; the primary limitation comes from what computer model can be installed. For ships larger than 3,000 tons, the computer Core model limits your size. Restated another way, TL limits the maximum size of ships greater than 3,000 tons that can be built:

  • TL7-8 up to 2,999 tons (use Computer Model 1)
  • TL9 up to 5,000 tons (use computer Core/3)
  • TL10 up to 10,000 tons (use computer Core/4)
  • TL11 up to 50,000 tons use computer Core/5)
  • TL12 up to 100,000 tons (use computer Core/6)
  • TL13-15 any hull over 100,001 tons (use computer Core/7 or greater)

For example, my perennial favorite developing planet, Arden (Arden/0201 Vilis/Spinward Marches) is a TL8 planet on the verge of TL9. What can Arden build indigenously without external assistance? Taking together all the technology limits one gets:

TL 8 Spacecraft Design Limitations

  • Hull Size: Up to 2,999 tons (cost 80%; 1 Hull/90 tons) (HG p. 65, 52, errata)
  • Armor: Titanium Steel (TL7) (HG p. 41)
  • Maneuver Drive max 5G (6G at TL-1) (HG p. 53)
  • No Jump Drive (Jump-1 at TL-1) (HG p. 53)
  • Powerplant – Fusion: 125% tonnage (HG p. 53, 63)
  • Computer – Model 1 (CRB p. 108)
  • Standard Sensors (CRB p. 108)
  • Weapons – Single or Double Turrets (CRB p. 111)
  • Turret Weapons – Pulse Laser, Particle Beam, Missile (HE/Nuclear/Smart/Shockwave/Ortillery), Sandcaster (CRB p. 111, HG p. 48, 50)
  • Weapons – Particle Barbettes (HG p. 50)
  • Weapons – 50-ton Bays (Missile Bank, Particle Beam, Torpedoes [Basic/Nuclear/Ortillery]) (CRB p. 112, HG p. 48)
  • Weapons – 100-ton Bays (Missile, Particle Beam) (HG p. 48)
  • Weapons – Spinal Particle A (HG p. 66) [Note that this spinal mount requires 5,000 tons whereas the TL limited ship size is 2,999 tons; obviously a planetary or station-mount only at TL8]
  • Options limited by TL – Compact Bridge, Aerofins, Docking Clamp, Grappling Arm, Solar Panels, Briefing Room, Standard Hanger, Library (HG p. 47)


Wargame Wednesday – Traveller High Guard: Bomb-Pumped Laser Missiles

Courtesy KKaju on Deviant Art

One piece of space combat kit that is referenced in latter Traveller products (like QuikLink Interactive’s Traveller’s Aide #9: Fighting Ships of the Solomani Confederation) is the Bomb-Pumped Laser (BPL) missile. The BPL is a missile that detonates near its target, but uses the resulting nuclear explosion to create laser beams to attack. For a bit of background see Atomic Rocketships.

In the most simple Traveller High Guard terms, a BPL missile will “hit” and “penetrate” as a missile but “damage” as a laser. To more accurately reflect the detonation of the BPL at some distance from the target a few modified rules are in order.

Bomb-Pumped Lasers: Using the Missile Attack Table, BPL missiles must achieve the to hit number (or greater) on two dice. However, to reflect the detonation of the BPL at a distance from the target, the USP of active defenses (Sand or Beam and Repulsors) is reduced by 1 (USP-1) for purposes of determining penetration. There is no passive defense (i.e. Nuclear Dampers) against a BPL. If a hit is achieved that penetrates the active defenses, resolve damage per Lasers using the Surface Explosion Damage Table with DM-2 to reflect the greater laser energy arriving at the target.

For example; a Striker-class Solomani Destroyer (TAS9-pg. 32) attacks an Azhanti High Lighting-class Fleet Intruder (Traveller’s Aide #7 – Fighting Ships of the Imperium – pg. 33) at long range. The Striker uses Battery 2, a USP 5 missile battery to attack and declares the use of BPL. The AHL defends with Battery 1 Beam Laser ( USP 9).

  • To Hit: Checking the Missile Attack Table in High Guard, the base To Hit for USP 5 missile attack is 5. DMs allowed are relative computer size (0), target agility (0), and target size (+2) for a final DM of +2. 2d6 are rolled for a 6, DM+2 for 8 which is a Hit .
  • To Penetrate: Cross-referencing the USP 5 missile with USP 9 Beam gives a To Penetrate of 9, but because the attack uses a BPL the USP of the Beam is reduced to 8 (USP-1) giving a To Penetrate of 8. DMs to penetrate are relative computer size (0). 2d6 are rolled for 9 resulting in penetration of defenses.
  • Damage Determination: Using the Surface Explosion Damage Table, 2d6 are rolled. DMs are armor (+5), weapon inflicting hit less than USP 9 (+6), and BPL (-2) for a final DM of +9. The roll of 2d6 is 6 is modified with the DM+9 for a 15 for a Weapon-1 damage. In this case, firing player reduces the Beam Laser Battery to USP 8.

Why Even Use a BPL? Deriving rules for use of BPLs in High Guard gives rise to the question as to why BPLs are even considered. The advantage of the BPL is in the penetration (weakened active defenses and no passive defenses) and a DM-2 on the Surface Explosion Damage Table. Using a regular nuclear missile, the missile must hit (neutral advantage compared to using BPLs), penetrate active defenses (with defenses at full strength – advantage to defender compared to BPLs) and passive defenses (advantage to defender compared to BPLs). Damage Determination also occurs on both the Surface Explosion Damage Table and the Radiation Damage Table (advantage to attacker if not using BPLs). So lets run through that example again but use a standard nuclear missile….

  • To Hit: Checking the Missile Attack Table in High Guard, the base To Hit for USP 5 missile attack is 5. DMs allowed are relative computer size (0), target agility (0), and target size (+2) for a final DM of +2. 2d6 are rolled for a 6, DM+2 for 8 which is a Hit .
  • To Penetrate Active Defenses: Cross-referencing the USP 5 missile with USP 9 Beam gives a To Penetrate of 9. DMs to penetrate are relative computer size (0). 2d6 are rolled for 9 resulting in penetration of active defenses.
  • To Penetrate Passive Defenses: The AHL has a USP 5 Nuclear Damper. DMs are the same (0). To Penetrate is 11. 2d6 is 8…no penetration. However, for the sake of the example, let’s assume the roll beat the low-probability 11+….
  • Damage Determination: Using the Surface Explosion Damage Table, 2d6 are rolled. DMs are armor (+5), weapon inflicting hit less than USP 9 (+6), and nuclear missile (-6) for a final DM of +5. The roll of 2d6 is 6 is modified with the DM+5 for a result of 11 or Weapon-2. The firing player reduces the Sandcaster battery to USP 8 and the Beam Laser battery to USP 8. A second damage roll is made on the Radiation Damage Table. DMs are armor (+5) and weapon inflicting hit less than USP 9 (+6) for DM+11. The roll of 2d6 is 7 for a final of 18 or Weapon-1. The firing player reduces the Fusion Gun battery to USP 8.

Doctrinally speaking, a nuclear missile is best used against an armored target with no nuclear damper where the DM-6 can be used to offset some (or all) of the armor. This is especially true if the attacking missile USP is less than 9. A BPL is best used against large unarmored or weakly armored, low agility, near or lower computing-power targets that carry nuclear dampers. This is admittedly a very narrow target set and makes the usefulness of BPLs questionable.