Quote from: KingofElfland on February 01, 2022, 03:50:20 PM
As to Orbital, it uses a trimmed down version. I think they release a free pdf for classic 2d6 Sci-Fi to make Cepheus Engine play more like original LBB classic Traveller. I know their Hostile line is very easy to grasp and go

Is this it?
[/quote]
Yes

Quote from: hedgehobbit on February 01, 2022, 06:48:25 PM
If you're going to play in any sort of semi-realistic game set in our solar system, I'd recommend downloading the map from a boardgame called High Frontier. It is an energy map of the solar system where distances are measure in number of burns (i.e. velocity) rather than meters. The map includes just about every solar object we currently know about as well as including information about other navigation hazards like erratic spins, debris fields, and radiation zones. It does almost all the math work for you. It even includes slingshot info.



[The sizes of objects is on a logarithmic scale. A size 3 asteroid is twice as big as a size 2]

That's really cool. Any idea what one burn is?

Quote from: estar on February 02, 2022, 08:26:27 AM
You can check it out for free with Cepheus
The original SRD
https://www.drivethrurpg.com/product/186894/Cepheus-Engine-System-Reference-Document

Lite-rules variations
https://www.drivethrurpg.com/product/371207/Cepheus-Light-Upgraded

I am focusing more on Cepheus because it more focused on settings other than the Third Imperium. Including a bunch of products that focus on the science fiction subgenre that the Expanse is part of. Like Hostile.

https://www.drivethrurpg.com/product/377186/Hostile-Rules

And Green Ronin's Expanse RPG is worthy of a look as well. It uses a 3d6 roll high system.

Thanks for those.

Quote from: Kiero on February 09, 2022, 09:11:04 AM
That's really cool. Any idea what one burn is?

2.5 km/sec of delta-vee.

From the rule book.

QuoteBURN SPACES show the velocity increment required to travel between orbits, often called delta-v. Each game Burn is 2.5 km/sec of delta-v. The delta-v of a rocket is defined by the rocket equation: Delta-v = Ve ln (Wet Mass/Dry Mass), where Ve is the exit velocity of the propellant in km/sec. Assuming a minimum energy (Hohmann) transfer, the delta-v to fly from LEO to some nearby destinations is: Nereus = 4.5 km/sec, Venus capture = 5.5 km/sec (neglecting aerobrake), Phobos/Deimos = 5.6 km/sec, lunar base = 5.7 km/sec, Earth's surface = 9.5 km/sec, and Mars base = 10.2 km/sec (again assuming no aerobraking). Notice that the martian moons are closer to us than our own moon, in terms of fuel and energy.

Quote from: estar on February 09, 2022, 09:21:06 AM2.5 km/sec of delta-vee.

Just for reference, the Saturn V could generate about 16,900 delta V (and that is with lots of complicated staging). Which is about 6 burns. In game terms, that's three burns from the surface of the Earth to orbit. Two burns from orbit to the Moon. And one burn from the Moon back to Earth. The rest was done with atmospheric braking.

Now in The Expanse, ships are capable of performing a 1g burn for hours at a time. The Saturn V could do it for less than 30 minutes then it's dead in space. Even the most advanced rocket ever built, the nuclear powered NERVA, could only produce a 1g burn for about twice as long. I hope that puts into perspective just how reality-defyingly good those Epstein drives actually are. An hour at 1g would give you a delta V of 35,280 m/s and in The Expanse, that doesn't seem to go through a significant portion of the ship's fuel reserves.

The introduction of something like an Epstein drive would completely shatter the economics of space travel and exploitation.

Quote from: hedgehobbit on February 10, 2022, 11:10:55 AM

Quote from: estar on February 09, 2022, 09:21:06 AM2.5 km/sec of delta-vee.

The introduction of something like an Epstein drive would completely shatter the economics of space travel and exploitation.

That was the point of having the Epstein drive in the novels.

Last night I sat down with the latest iteration of the High Frontier map and worked with it and figured out the following.


.3 G = 2 days per burn
1 G = 1 day per burn
7 G = 1/3 day per burn
12 G = 1/4 day per burn


It correlates highly with travel times using the average separation distance.

You have to keep in mind that the High Frontiers map is a ENERGY map not one based on strict distances. So the procedure is.

Starting at the destination, count up all your burns including any hohman pivots which count as two burns each. But SUBTRACTing any burns you get from a flyby. The total number of burns is the total travel time.

If something was to happen mid journey then you need to figure out when it happen proportionally.  For example if it take 5 burns to get to Mars thus 5 days at 1G. And something was to happen 2 day in. Then you need trace the path until your are 20% of the way there and that where it happens.

The map is more of a slide rule to help calculate how much energy and time it takes to travel somewhere. In the normal HF rules. A turn is a year and your engine's thrust ratings is how many burns you can do in that time. The movement is basically you can move as far as you want as long as you have the burns (and fuel to make the burns). If you run out of burns (and still have fuel remaining) you have to stop in the space prior to the next burn in the sequence and deal it with it in the movement phase of the next turn (and adding a year of travel).

With the Epstein Drive the Energy paths still matter as it still take time for the drive to build up speed, flip and decelerate. But since the drives are so efficient it can be handled quicker. Hence the travel time is measured not in turns of a year but how many burns must be made. And most inner system destination can be reached in days. And the outer system within weeks.

There are still issue with the HF Map in that there is a lot of stuff on it tailored for the game itself. That gets in the way of using it as an aide for the Expanse RPG (or any other solar system setting). I am going to redraw the maps to remove the unneeded clutter and see how that works.

Quote from: RebelSky on February 02, 2022, 03:09:10 PM
Fun fact about The Expanse universe...

The Expanse universe was created by a homebrew sci-fi rpg campaign the writers played using d20 Modern with all the D20 Modern sci-fi books.

A friend of mine knows the authors. He mentioned they used Traveller. Maybe he was wrong. Other fun fact. The rpg Expanse campaign was run my GRRM.

Quote from: estar on February 10, 2022, 11:44:08 AMThat was the point of having the Epstein drive in the novels.

I haven't read the books as I've only watched the Amazon show but I don't think the ramifications of the Epstein drive are fully realized in the setting. IOW, some of the things that are present in the setting, such as belters having a distinct language or water being rare, aren't particularly realistic considering the low cost and speed of travel that the Epstein drive provides. To me it is sort of like having huge areas of "Unexplored Regions" in Star Wars even though ships can easily fly across such areas in a matter of hours.

Quote from: soundchaser on February 10, 2022, 12:20:29 PMA friend of mine knows the authors. He mentioned they used Traveller.

That's totally believable. Maintaining a constant 1g burn and doing the "flip and burn" maneuver at your halfway point are two things that are in Traveller (even if they don't really make sense).

Quote from: hedgehobbit on February 10, 2022, 02:02:33 PM

Quote from: estar on February 10, 2022, 11:44:08 AMThat was the point of having the Epstein drive in the novels.

I haven't read the books as I've only watched the Amazon show but I don't think the ramifications of the Epstein drive are fully realized in the setting. IOW, some of the things that are present in the setting, such as belters having a distinct language or water being rare, aren't particularly realistic considering the low cost and speed of travel that the Epstein drive provides. To me it is sort of like having huge areas of "Unexplored Regions" in Star Wars even though ships can easily fly across such areas in a matter of hours.

Quote from: soundchaser on February 10, 2022, 12:20:29 PMA friend of mine knows the authors. He mentioned they used Traveller.

That's totally believable. Maintaining a constant 1g burn and doing the "flip and burn" maneuver at your halfway point are two things that are in Traveller (even if they don't really make sense).

I always questioned that The Expanse was originally based on a d20 Modern/Future game and not Traveller. The way that the ships of The Expanse maneuver is definitely not what is in the d20 rules, but more like Traveller.

I also disagree with water is rare bit as well. From everything I've read, water is pretty common in easy to reach spots and forms once you get beyond the snow line. Not to mention indications of water ice in craters on the Moon and Mercury.

Quote from: hedgehobbit on February 10, 2022, 02:02:33 PM
I haven't read the books as I've only watched the Amazon show but I don't think the ramifications of the Epstein drive are fully realized in the setting. IOW, some of the things that are present in the setting, such as belters having a distinct language or water being rare, aren't particularly realistic considering the low cost and speed of travel that the Epstein drive provides. To me it is sort of like having huge areas of "Unexplored Regions" in Star Wars even though ships can easily fly across such areas in a matter of hours.

The Expanse comes across to me as an old and developed civilization. Both in the novel and the show. They have dozens of ships like the Canterbury working the ice rings of Saturn to supply water for millions.

As for the speed of the Epstein drive. The situation at the start of Leviathan Wakes is that it takes days to travel between major settlement. You can think of the Expanse Solar System as the Pacific Ocean with the different settled planets, moons, stations, and asteroids islands dotting the ocean. Sure it wasn't hard for the Polynesians to travel but it wasn't easy either. Leading to different sections of the Pacific to develop in its own way. And beyond Saturn it still takes weeks to get anywhere.

Quote from: jeff37923 on February 10, 2022, 02:14:36 PM
I always questioned that The Expanse was originally based on a d20 Modern/Future game and not Traveller. The way that the ships of The Expanse maneuver is definitely not what is in the d20 rules, but more like Traveller.

Why can't you run d20 Modern with Traveller Starship rules?

Quote from: jeff37923 on February 10, 2022, 02:14:36 PM
I also disagree with water is rare bit as well. From everything I've read, water is pretty common in easy to reach spots and forms once you get beyond the snow line. Not to mention indications of water ice in craters on the Moon and Mercury.

1) Ceres is right on the inner edge of the frost line in the Solar system.
2) It was stated that all the water was mined from Ceres and it requires imported water to keep things going.

Quote from: estar on February 10, 2022, 02:18:00 PM

Quote from: jeff37923 on February 10, 2022, 02:14:36 PM
I always questioned that The Expanse was originally based on a d20 Modern/Future game and not Traveller. The way that the ships of The Expanse maneuver is definitely not what is in the d20 rules, but more like Traveller.

Why can't you run d20 Modern with Traveller Starship rules?

Well, you can do it that way. I just consider it to be heresy. 

Quote from: estar on February 10, 2022, 02:18:00 PM

Quote from: jeff37923 on February 10, 2022, 02:14:36 PM
I also disagree with water is rare bit as well. From everything I've read, water is pretty common in easy to reach spots and forms once you get beyond the snow line. Not to mention indications of water ice in craters on the Moon and Mercury.

1) Ceres is right on the inner edge of the frost line in the Solar system.
2) It was stated that all the water was mined from Ceres and it requires imported water to keep things going.

What about the Jovian Trojans? The delta vee to get from there to Ceres can't be greater than going from Saturn to Ceres.
(I know, I'm quibbling.)

Quote from: jeff37923 on February 10, 2022, 02:35:13 PM
Well, you can do it that way. I just consider it to be heresy. 

Sorry man, hybrids are the norm not the exception.

Quote from: jeff37923 on February 10, 2022, 02:35:13 PM
What about the Jovian Trojans? The delta vee to get from there to Ceres can't be greater than going from Saturn to Ceres.
(I know, I'm quibbling.)

Well it does take as much delta-vee to reach Deimos or Phobos as it does to land on the moon. So it all depends on how the energy plot looks.

According to HF map and my rules it would take 9 burns and 9 days at 1 G to reach Low Callisto Orbit.
To reach Ceres or more accurately the Gefion family of asteroids it would take 8 burns.
To reach the Trojan Jupiter group it would take 10 burns.
To reach the Greek Jupiter group it would take 9 burns.

There is an alternative path to the Greek to the L3 Mars-Sol point that only takes 8 burns.

Quote from: estar on February 10, 2022, 03:19:44 PM

Quote from: jeff37923 on February 10, 2022, 02:35:13 PM
What about the Jovian Trojans? The delta vee to get from there to Ceres can't be greater than going from Saturn to Ceres.
(I know, I'm quibbling.)

Well it does take as much delta-vee to reach Deimos or Phobos as it does to land on the moon. So it all depends on how the energy plot looks.

According to HF map and my rules it would take 9 burns and 9 days at 1 G to reach Low Callisto Orbit.
To reach Ceres or more accurately the Gefion family of asteroids it would take 8 burns.
To reach the Trojan Jupiter group it would take 10 burns.
To reach the Greek Jupiter group it would take 9 burns.

There is an alternative path to the Greek to the L3 Mars-Sol point that only takes 8 burns.

Is there a larger HF map that I can access online? I can't really read the numbers for the image on Imgur and I'm left with mathing it out which will take me a bit of time I don't have right now.

What about taking a leaf from GURPS Terradyne? I bought it at the end of my GURPS cycle so I never played it it, but IIRC it had a strong "let's colonise the Solar System - realistically!" vibe.

Quote from: jeff37923 on February 10, 2022, 04:08:40 PM

Quote from: estar on February 10, 2022, 03:19:44 PM

Quote from: jeff37923 on February 10, 2022, 02:35:13 PM
What about the Jovian Trojans? The delta vee to get from there to Ceres can't be greater than going from Saturn to Ceres.
(I know, I'm quibbling.)

Well it does take as much delta-vee to reach Deimos or Phobos as it does to land on the moon. So it all depends on how the energy plot looks.

According to HF map and my rules it would take 9 burns and 9 days at 1 G to reach Low Callisto Orbit.
To reach Ceres or more accurately the Gefion family of asteroids it would take 8 burns.
To reach the Trojan Jupiter group it would take 10 burns.
To reach the Greek Jupiter group it would take 9 burns.

There is an alternative path to the Greek to the L3 Mars-Sol point that only takes 8 burns.

Is there a larger HF map that I can access online? I can't really read the numbers for the image on Imgur and I'm left with mathing it out which will take me a bit of time I don't have right now.

This is the highest resolution you can download. However you will need an account (free) in order to get access to it.
https://boardgamegeek.com/image/5605558/high-frontier-4-all