#RPGaDay 2017 – Which RPG have you played the most since August 2016?

#RPGaDay August 4, 2017

pic3089588_tAlthough it is not reflected in in my RPGGeek play records, the RPG I have played the most since August 2016 is Cepheus Engine, and in particular the The Clement Sector setting, Orbital 2100 (as an exploration for The Expanse), and tried These Stars are Ours! I also had more than a little bit of time invested in Star Trek Adventures but gave up two-thirds of the way thru the playtest for lack of excitement.


#RPGThursday – My new Top 10 RPG (March 2017)

I was updating my RPGGeek collection and noticed that my Top 10 was way out of date. Made me start thinking again about which games I like and why.

#10 – Star Wars: Edge of the Empire

pic1545989_mdAt first I was confused by all those fancy dice with their crazy symbols. Now I see this system as one of the best matches of narrative gameplay and setting. I don’t see any other way to play a cinematic science fiction adventure. The nearly-identical Age of Rebellion and Force and Destiny round out the trilogy of adventure just like the original trilogy of movies did. Although low on my list, I am the GM in a campaign for the RockyMountainNavy Boys using this system.

#9 – Mindjammer: The Roleplaying Game (Second Edition)

pic1972069_tI always thought I would not enjoy transhumanism settings in my sci-fi RPG adventuring. At least, that was until I found the FATE Core-driven Mindjammer. Another exploration into narrative-driven RPG systems. (Avoid the Mongoose Traveller version.)

#8 – Traveller5

pic1550426_tMore a guilty pleasure than a game I play. Many people deride the rules but this is my go-to version of Traveller when I want to do some hardcore setting creation. Actually, as long as one avoids Melee Combat the rules hold up surprisingly well. It’s a shame this one gets so much bad press, the game is actually very good – its the bad reputation the first rulebook got that I think makes people stay away.

#7 – Firefly Roleplaying Game

pic1978226_tDriven by the Cortex Plus system, this is another game that shows my tilt towards more narrative-driven games. The setting is also in keeping with the Original Traveller Universe (and not all that far from Edge of the Empire either). The production quality of the books are so shiny!

#6 – FATE Accelerated

pic2026320_tStrictly rules, this slimmed down version of FATE Core is the best rules set I have found to introduce new players to narrative RPG gaming. Some people accuse this game of being too simple; I disagree and say it is the ultimate “rules-lite” system.

#5 – Atomic Robo

pic2005630_tAtomic Robo is a fine example of what happens when authors and game designers are of the same mind. The rulebook is one of the best I have ever seen, effortlessly taking source content and marrying it to game system and examples. The Brainstorming Rules are absolutely essential to ANY narrative-driven game played.

#4 – James Bond 007

pic532310_tGoing old-school here, but James Bond 007 has stood the test of time. The Chase rules, where one bids for initiative is very cinematic. I now recognize that this was the first RPG I played that had a Game Economy in the form of Hero Points. There is also the best-ever Example of Play which puts iconic scenes from the movie Goldfinger opposite game play.

#3 – Cepheus Engine System

pic3217788_tCepheus Engine is the modern 2d6 Sci-Fi RPG system that is the natural evolution of Classic Traveller. Except this one uses the Open Game License and not Mongoose Traveller’s much more restrictive legal obstacles to third-party publishing. Though a youngster, there are several great settings that take advantage of they rules including the awesome The Clement Sector, Orbital 2100, and the brand-new These Stars are Ours!

#2 – Diaspora

pic536195_tDiaspora uses the older FATE 3.0 engine, and could probably use an update to FATE Core. But the designer’s don’t have to be in a rush because Diaspora is a great game as-is. Occasionally called the Traveller version of FATE, I love it for many of the same reasons I love Traveller; it is a sci-fi adventure RPG with moderate rules overhead. The Space Combat rules are a unique take on vector-combat using range bands (and should be retrofitted to Classic Traveller).

#1 – Classic Traveller

45b96a0a8845ed78b2958bc87f1b6b58_largeIt was 1979 that I first discovered roleplaying games, and my gateway game was the three Little Black Books of Traveller. Who can ever forget the simple text on the box cover:

“This is Free Trader Beowulf, calling anyone…Mayday, Mayday…we are under attack…main drive is gone…turret number one not responding…Mayday…losing cabin pressure fast…calling anyone…please help…This is Free Trader Beowulf…Mayday….”

Now known as Classic Traveller, the rules are still a model of “complex simplicity.” Complex in that all the tools for making your own adventure are there (there is no default setting or Third Imperium in the original LBBs) and simple in terms of rules. Maybe a bit too simple, as shown by the modern rules version in Cepheus Engine. It really doesn’t matter to me what today’s version is called, Classic Traveller will always be the one dearest to my heart.

All images courtesy RPGGeek

#TSAO These Stars Are Ours! A setting for #CephesusEngine or #TravellerRPG



Courtesy spacecockroach.blogspot.com
These Stars Are Ours!  (TSAO) is a tabletop RPG Sci-Fi setting for the Cepheus Engine or 2D6 OGL SCIFI (nee Traveller SRD). TSAO is a complete Alternate Traveller Universe (ATU) small-ship setting that offers rich background, interesting aliens, and many adventure seeds for the Referee. Though not without a few warts, TSAO shows the great potential of Cepheus Engine used in a setting beyond the classic Third Imperium.  TSAO may be the first setting to take full advantage of the Cepheus Engine rules from the ground up and joins Gypsy Knight Games The Clement Sector and Zozer Games Orbital 2100 as yet another example of the vibrant Cepheus Engine community of rules and settings.



The setting of TSAO is a logical outgrowth of 20th century UFO conspiracies:

Set in 2260 AD – two years after the Terrans took Keid and forced the Reticulan Empire to capitulate the book introduces the player characters to the immediate aftermath of the Terran victory in the Terran Liberation War against the mighty Reticulan Empire and its many thralls. For their part, the upstart Terrans, bolstered by their victory against their old masters, now move to become a power to be reckoned with in interstellar affairs. Against this background of espionage, maneuvering, and saber-rattling, and on the new interstellar frontiers, the player characters can forge a destiny of heroes or villains of the new United Terran Republic. (DriveThruRPG)

TSAO is delivered in a 209 page pdf (also now available in a POD option). This meaty setting is explained over six chapters and two appendixes.


Courtesy spicapublishing.co.uk
Chapter 1 – The United Terran Republic provides much of the history and setting background. Included is not just a recap of events to date, but also many groups or factions or agencies that the player characters (PCs) could interact with. Psionics has a role in this setting. Given the assumed Tech Level (TL) of 11-12 (with some military at 13), TSAO (like Omer Golan-Joel’s earlier Outer Veil setting) is a high-tech but small-ship universe.


Chapter 2 – Aliens describes the humans neighbors, opponents, and allies(?). In the space of just a few pages many races are fully described and (again) are rich with adventure seeds and story hooks for development.

Chapter 3 – Characters and Careers is a great example of how to take the basic character generation system in Cepheus Engine and stretch it to showcase it’s full potential. PCs can be the default Humans or select from several alien races. Careers are taken from 13 civilian careers in Cephesus Engine or an from the 20 new ones in TSAO, including seven (7) alien “careers.”

Courtesy spacecockroach.blogspot.com
Chapter 4 – Starships showcases alien saucers and Terra’s ships along with a few other alien constructs. Art is provided by the ever-dependable Ian Stead and others. Make sure to look at the 300-ton Terran Shaka-class Light Military Transport (and especially the Decommissioned Shaka-class Transport) for a not-to-subtle nod to Serenity and the Firefly-class.

Chapter 5 – Terran Borderlands is combination gazetteer and Referee’s Information. The worlds of Known Space is detailed, along with many story hooks and adventure seeds. The usual World Generation process from Cephesus Engine is expanded upon here with an Expanded Universal World Profile that adds a bit more detail but also a whole many more ideas that PCs or Referees can grab onto.

Chapter 6 – Patrons describes 12 Patrons that might engage the PCs. The chapter is not only a grouping of ready-made adventures, but also provides insight into the setting as viewed by the authors.

Appendix A – Terran News Agency Dispatches, February 2260 is a call back to the Traveller News Service snippets that were a staple of Classic Traveller and its successors. Again, these short news items can be the start of yet more adventures!

Appendix B – Sources of Inspiration, Literary and Otherwise is TSAO‘s Appendix N. I always look over these lists to see what inspirations the authors took and to see what I may want to add to my reading/viewing.

The last part of TSAO is an index. This is one of the best indexes I have ever seen in a book. However…the pdf is not cross-linked. This highlights some of my pet peeves with so many pdf products; page numbering and no linking. TSAO is paginated like most books, with page 1 being the interior title page. Unfortunately, this is “page 3” of the pdf, meaning if using your pdf page search you will always be three pages off from your target! The publisher could of avoided (or lessened the impact) of this issue if the Table of Contents (or even that great Index?) was linked.

Production quality is very good. Compared to Stellagama’s previous The Space Patrol I can see definite improvement. Get the linking and page numbering issues nailed and I will likely have nothing to complain about….

The authors call TSAO the first in the Visions of Empire (VoE) space opera settings. If TSAO is any indication, the VoE series will be settings rich in background using (and stretching) the Cepheus Engine rules to their finest.


These Stars Are Ours!  By Omer Golan-Joel, Richard Hazelwood, and Josh Peters. Stellagama Publishing, 2017.

#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!




#RPGThursday -To the Far Horizon with Atlas

Two of my three favorite Traveller RPG, uhh…”2d6 Classic Sci-Fi RPG”, companies published new items recently that I acquired.

202309-thumb140The first is Far Horizon from Zozer Games. The cover calls it Far Horizon: A TL9 Exploration Ship for the Cepheus Engine whereas the front matter states Far Horizon: A Near Future Mission and Spacecraft for Cepheus Engine. Both titles are correct, although the second one is more accurate. This title is designed to go with the Zozer’s Alternate Traveller Universe (ATU) setting of Orbital: 2100 although everything is included here to play this adventure with just the basic Cepheus Engine rules if needed. pic3217789_mdInside one finds not only background into the mission but also a complete description of the DRV Far Horizon, a nuclear-thermal rocket for exploring deep space. Included also are rules for TL9 Vacc Suits. The adventure itself is a race-against-time investigation into the unknown.

109517-thumb140Parts of Far Horizon have been available previously. The ship itself is a free download at DriveThruRPG. The rules on vacuum suit construction were in a previous product, Vacc Suit, which is no longer available no-thanks to the Mongoose Publishing Community Content Agreement. So it is refreshing to see this packaging bringing back good near-future, hard-ish sci-fi adventure! Adding to the quality, the product is nicely illustrated by Ian Stead and others.

If one has looked at Orbital: 2100 but are not sure about making the jump into this ATU, Far Horizon is a great way to try out the setting.

202134-thumb140The second product I got was Ships of the Clement Sector 17: Atlas-class Freighter from Gypsy Knights Games. This is the second of what I call “expanded” ship books from GKG. The 50-page product includes excellent narratives to set the mood, awesome ship art by Ian Stead (again), and just enough adventure seeds to whet a GM’s appetite. Indeed, this larger format allows for more of each giving both players and GMs more to think about and more potential for adventure. If you are a fan of The Expanse, you may find a similar vibe to that universe and some of the stories and background presented here. Though many might look at an 800 dT freighter as “not sexy enough to be my ship,” the reality is it takes ships like the Atlas to ply the shipping lanes of the Clement Sector and ekk out a living. This book helps your players do just that. Another must-buy from GKG!

All images courtesy DriveThruRPG.

Far Horizon, ©2016 Zozer Games.

Ships of the Clement Sector 17: Atlas-class Freighter, ©2017 Gypsy Knights Games, LLC.


#RPGThursday – Rucker Patrol

Two RPG items I got over the holidays were Ships of the Clement Sector 16: Rucker Class Merchant (Gypsy Knights Games) and The Space Patrol (Stellagama Publishing). Long-time Traveller RPG fan Alegis Downport already posted his views of each so I direct your attention to his excellent comments (Rucker / Space Patrol) and will just add a few more thoughts of my own.

pic3293444_mdMake sure you read both parts of Alegis Downport’s comments on the Rucker since he had a very intimate hand in the creation of the ship. There is nothing more I can add except to heartily endorse all the kudos he gives to Gypsy Knights Games for bringing Ships of the Clement Sector 16: Rucker Class Merchant to market. SotCS 16 continues a great line of useful products from Gypsy Knights Games that are at home in any Traveller RPG setting. Thanks to Alegis Downport, users of the ship now have even more thought-seeds for adventure.

pic3238660_mdMy praise for The Space Patrol is a bit more reserved. The Zhodani Base named The Space Patrol their “Best ATU Setting” for 2016. As much as I like Zho, I must respectfully disagree. Although I find The Space Patrol a very interesting career and a welcome addition to any setting, I feel that pic3217789_mdOrbital: 2100 (Zozer Games) is a much better example of how to take the original Traveller 2d6 sci-fi system (as detailed in Cepheus Engine) and use it to make an exciting Alternate Traveller Universe. I also feel that The Space Patrol suffers from some poor formatting decisions (like more-that-a-few tables that cross pages) that make it feel a bit too DTP-like in an era where small publishers (like Gypsy Knights Games) push out very high quality products. But don’t get me wrong – The Space Patrol is a great addition to any Traveller/2d6 Sci-Fi/Cepheus Engine setting and should be in everyones collection. I just wouldn’t have given it the coveted ATU Setting of the Year. 

All images courtesy RPGGeek.

Ships of the Clement Sector 16: Rucker Class Merchant, ©2016 Gypsy Knights Games.

The Space Patrol, by Richard Hazelwood, ©2016 Stellagama Publishing.

Orbital: 2100 – A Solar System Setting for the Cepheus Engine, by Paul Elliot, ©2016 Zozer Games.

#TheExpanse #TheDrive in Orbital 2100 – #TravellerRPG & #CepheusEngine Mods

In a previous post, I discussed the role-playing game Orbital 2100 – A Solar System Setting Using the Cepheus Engine Game and how it could possibly be used for playing in The Expanse setting. In The Expanse, the Epstein Drive is the engine that powers spacecraft across the Solar System. But just how does the Epstein Drive perform, and how could it be portrayed in the Orbital: 2100 setting using Cepheus Engine?

When playing Traveller or today’s Cepheus Engine games like Orbital 2100, I tend to be (using Marc Miller’s definitions from T4) a “Detailed Role Player.” I stray into the “System Engineer” role at times, like for this post. Part of my intention here is to show RPG players and referees/GMs that “this isn’t rocket science” – between the setting, game rules, and the internet (and with the help of a spreadsheet/calculator) it is actually fairly easy to do this analysis.

Fortunately, we have a “canon” story that we can draw inspiration from. The novella The Drive (published in 2012 and available for free online) takes place 150 years before the events of the first novel in the series, Leviathan Wakes. The Drive tells the story of Solomon Epstein, the inventor of the Epstein Drive. It is a very short novella coming in at a mere seven pages. Those seven pages, however, give us plenty of information that can be used to derive the performance of the Epstein Drive.

“By the way, we’re accelerating at four gravities. Five. Six. Seven.”

“He wonders how much above seven he’s going. Since the sensors are pegged, he’ll have to figure it out when the run is over.” – p. 1

In the first pages of the novella, we find a common language between the novels and the Orbital 2100 setting. Like Cepheus Engine and the Traveller RPG it derives from, spacecraft performance is expressed in g’s of acceleration. One g (1g) of acceleration is 9.8 meters/second/second. [Cepheus Engine and Traveller round this to 10 m/s/s…but we will use the actual value for the purposes of this discussion] Seven g’s of acceleration works out to 68.6 m/s. Since Sol’s “sensors are pegged,” this passage also establishes an instrumentation limit of the time.

“The yacht is built for long burns, and he started with the ejection tanks at ninety percent. The readout now shows the burn at ten minutes. The fuel supply ticks down to eighty-nine point six. That can’t be right.

Two minutes later, it drops to point five. Two and a half minutes later, point four. That puts the burn at over thirty-seven hours and the final velocity at something just under five percent of c.” – p. 1

These passages help determine a fuel consumption rate.

  • Using the 90% full tank as a beginning, and given that after 10 minutes 89.6% remains, we see that .4% was consumed in that short time for an hourly consumption rate of 2.4%.
  • “Two minutes later,” or after 12 minutes of total burn, the tanks are 89.5% full; meaning that .5% has been consumed at a rate of 2.5% per hour.
  • Finally, after 2.5 minutes more – or 14.5 minutes total – the tanks are at 89.4% full, or .6% consumed for a rough consumption rate of 2.4% per hour.

Using the 2.4% rate, 90% divided by 2.4% gives us 37.5 hours of “burn” endurance – right in line with Solomon’s “over thirty-seven hours” statement.

The later passage helps compute the acceleration performance of the Epstein Drive.

  • The speed of light – c – is 299,792,458 m/s. Five percent (5%) of c is 14,989,623 m/s.
  • The formula for acceleration is a=v/t where a equals acceleration in m/s, v is velocity in m/s, and t is time in seconds.
  • Plugging in our numbers for velocity (5% of c) and time (37.5 hours or 135,000 seconds) we get an acceleration of 111.03424 m/s.
  • Dividing this by 9.8 m/s, we get 11.33g acceleration.

Eleven g’s of acceleration is quite a lot, even for Cepheus Engine/Traveller where a top-grade maneuver drive is no more than 6g performance!

“Only the acceleration isn’t the problem either. Ships have had the power to burn at fifteen or even twenty g since the early chemical rockets. The power is always there. It’s the efficiency necessary to maintain a burn that was missing. Thrust to weight when most of your weight is propellant to give you thrust. And bodies can accelerate at over twenty g for a fraction of a second. It’s the sustain that’s killing him. It’s going for hours.” – p.3

NASA and the military conducted many experiments in the 1950’s and 1960’s that established a 20g human limit to acceleration. Sol is obviously in pain, but in terms of Cepheus Engine and Orbital: 2100, just how much damage is he taking?

There are no specific rules in Orbital 2100 for acceleration effects on characters. Looking at “Falling and Gravity “in Cepheus Engine (p. 164), we see that on a 1g world, the character will get 1d6 damage per 2m of fall. The rules further specify that for higher g worlds, multiple the 1d6 by the planet’s gravity number. The Epstein Drive accelerates at 11g, which we can compute as 11d6 damage. The question is the time period in which this damage takes place. Falling is assumed to be instantaneous, but declaring 11d6 damage per combat round (6 seconds) does not seem to fit the events of The Drive. This seems excessive because an average character in Orbital 2100 (7 Strength/7 Dexterity/ 7 Endurance) only has 21 damage points until death. The “average” damage from 11d6 is 44, meaning the character is dead twice over!

Perhaps we should assume the 11d6 damage takes place every space combat round  (1,000 seconds/16.6 minutes) instead. This better reflects the painful, but non-instantaneous death like Solomon Epstein experiences. It still seems like an excessive amount of damage, guaranteeing character death.

Looking around for a solution, and not finding one in the rules, I suggest a “house rule” that acceleration couches absorb some of the damaging g forces. In This New Ocean: A History of Project Mercury, acceleration couches in the Mercury spacecraft were designed to absorb 9g (assumed to be the maximum g at reentry). If we use couches to absorb 9 of 11g, the character will have only 2g of damage (2d6) per space combat round. This means an average human may  last as long as three space combat rounds, or about 48 minutes, before sub-coming to the strangling g forces.

“Even as he struggles to make the terminal respond, he’s also thinking what the drive means practically. With efficiency like this, ships can be under thrust all through a voyage. Acceleration thrust to the halfway point, then cut the engines, flip, and decelerate the rest of the trip. Even a relatively gentle one third g will mean not only getting wherever they are headed much faster, but there won’t be any of the problems of long-term weightlessness. He tries to figure how long the transit to Earth will take, but he can’t.” – p.5

Ah, here we can use the classic formula for interplanetary travel time where a ship constantly accelerates to a midpoint, flips over, and then decelerates at a constant rate to the destination. The formula is t=2*SQRT(d/a) where like before = time in seconds, = distance in meters, and = acceleration in m/s/s. (see Cepheus Engine, p. 104)

Unlike Solomon, we do not have 11g’s of force crushing down upon us, so we can solve for the time it would take an Epstein Drive spacecraft to travel from Mars to Earth.

To figure distance, one must first realize that both Mars and Earth orbit the sun differently and the distance between the two planets is not constant. At opposition, the two can be as close as 56 million kilometers (Mkm); however, at conjunction the two can be as far as 401 Mkm apart!. On average, Mars and Earth are 225 Mkm apart.

[Interestingly, in Cepheus Engine, Chapter 6: Off World Travel, Interplanetary Travel, Table: Common Travel Times by Acceleration, there is a listing for “Far Neighbor” with a distance of 255 million km. This is close enough to the Earth-Mars average distance that I think it was the source for the entry. Orbital 2100, Chapter 6: Operating Spacecraft, Travel Times, Travel Between Inner Planets, uses a different process to determine distance (p. 71). In Orbital 2100 you start with the Basic Distance of 80 Mkm (Inner Planets: Basic Distance Table) PLUS seven squares of travel on the Travel Between Inner Planets chart (using the recommended starting setup). This works out to a total travel distance of 290 Mkm – within reason but a bit above the average.]

For the purposes of this example, lets use the 225 Mkm average. Using that average distance (225 Mkm), and Sol’s stated  1/3g (3.27 m/s acceleration), the formula gives us a travel time of Mars to Earth of just over 3 weeks. This may be a normal pre-Epstein Drive trip, given the 3.27g falls within the previously noted 7g instrument limit.

“The United Nations ordered that all shipyards on Mars shut down until an inspection team could be sent out there. Seven months to get the team together, and almost six months in transit because of the relative distances of the two planets in their orbits around the sun.” – p. 6

From this passage we can assume that Sol is telling us that the average transit time between Earth and Mars is about six months. The is an important figure to remember for later.

“And the war! If distance is measured in time, Mars just got very, very close to Earth while Earth is still very distant from Mars. That kind of asymmetry changes everything.” – p. 7

Once again, lets assume the Earth to Mars distance d to be 225 Mkm. Using the Epstein Drive with an acceleration of 11g ( a=111.03424 m/s) and solving for time t gets 12.5 hours. This is a major difference from the six months Sol was thinking about earlier. It is orders of magnitude better performance!

Think for a moment about Jupiter like Sol does. Assuming the Earth-to-Jupiter average distance is 588 Mkm, using the Epstein Drive the trip would take 1 day and 16 hours!

In Orbital 2100, the best TL 9 Nuclear Thermal Rocket (NTR, p. 41) can only travel a maximum of 330 Mkm per month, meaning it takes 1 month and 23 days to make the Earth to Jupiter transit. Even the best alternative TL 10 Fusion Drive, or Nuclear Pulse Fusion (NPF, p. 61), has an acceleration performance of 12 m/s for a travel time of 5 days and 21 hours. Even the best performing Maneuver Drive in Cepheus Engine (6g or 60 m/s acceleration – p. 122), takes 2 days and 7 hours to make the same trip.

Unfortunately, as much as we can learn from The Drive about Epstein Drive performance, the novella lacks other details like the size of the drive or the volume of fuel required. This means we will have to look elsewhere for that information, like maybe Leviathan Wakes.

In summary, the Epstein Drive is very efficient compared to the NPR and NTR in the Orbital 2100 setting. Even compared to maneuver drives available in Cepheus Engine the Epstein Drive is superior. The major drawback, as Sol discovered, is the crushing gravity of acceleration. In the default Traveller setting, the Original Traveller Universe, this is overcome by using handwavium acceleration compensators. In The Expanse, 150 years after Sol’s invention, you have “the juice.”

The juice was a cocktail of drugs the pilot’s chair would inject into him to keep him conscious, alert, and hopefully stroke-free when his body weighed five hundred kilos. Holden had used the juice on multiple occasions in the navy, and coming down afterward was unpleasant. –Leviathan Wakes

Leviathan Wakes, Copyright (c) 2011 by Daniel Abraham and Ty Franck.

The Drive (A Novella for The Expanse), Copyright (c) 2012 by Daniel Abraham and Ty Franck.

Cepheus Engine: A Classic Era Science Fiction 2D6-Based Open Game System. Copyright (c) 2016 Samardan Press.

Orbital 2100 Second Edition, Copyright (c) 2016 Zozer Games.

“The Traveller game in all forms is owned by Far Future Enterprises. Copyright 1977-2016 Far Future Enterprises.”