Quote from: estar on February 10, 2022, 11:44:08 AM
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.

Would any pre-existing (if not so pretty) delta-v maps be of help? Like these?

https://drive.google.com/file/d/13Qhtxlnhd_vYRQoldieKDy1ePakHC1nj/view?usp=sharing

https://drive.google.com/file/d/1ma3XSSjm87K9EEP_fjIIsnAh1DB9qRcv/view?usp=sharing

I think pretty much any group familiar with the source material, playing in the setting, would likely want a Martian gunship for their "PC ship". After all, that's what the protagonists of the series do, which sets them apart from any other lot with a civvy ship mounting external torpedo racks and a jury-rigged PDC. And let's be honest, no one wants a UNN vessel.

It has to be a smaller one that can run with a relatively small crew, and that's another reason for an ex-military ship, which is designed with redundancies in mind. Something that can be crewed effectively by 6 or less. Which puts the cruisers needing dozens of personnel out of the reckoning.

So how might they get one?

If the game is set around the time of the first book, that makes it rather difficult. Various exceptional circumstances combined to allow Holden et al to escape on the Tachi and claim it as "legitimate salvage". And they suffered legal problems for a while afterwards until the Martian government gave up.

With the Earth Mars war that starts over Ganymede, you have a richer vein of possibility with wrecks that could be salvaged. You could come up with any number of ways a frigate or destroyer could have been abandoned after enemy action that would allow the PCs to seize it after the fact. That could easily be the seed of a major plot arc in it's own right.

If you're following the plotline of the books, there's the Inaros-OPA faction's attack on the Martian naval shipyard on Callisto for another way something could get "lost". The shipyard was destroyed, which may also mean records of what was there were compromised.

Then later, with the opening of the ring gates, we have the sudden appearance of MCRN tech, all the way up to ships, on the black market. Lots of the gunships that could be carried in the belly of the Donnager battleships "disappeared", many being diverted to the Free Navy. Which in itself could be a way the PCs get hold of one, as well as other nefarious means.

Quote from: Kiero on February 18, 2022, 09:08:20 AM
I think pretty much any group familiar with the source material, playing in the setting, would likely want a Martian gunship for their "PC ship".

In AD&D1e, I always wanted a +5 vorpal sword.

Players don't always get what they want. Sometimes they even have to make a plan to go and get it - and it might not even succeed. And that's where we get adventures from.

Quote from: Kyle Aaron on February 18, 2022, 10:06:54 PM
In AD&D1e, I always wanted a +5 vorpal sword.

Players don't always get what they want. Sometimes they even have to make a plan to go and get it - and it might not even succeed. And that's where we get adventures from.

Granted, my point was it's a tangible starting goal in which there are varying plausible openings that could make it possible. Before some of the events of the books, it's in the realms of impossible.

Go steal a warship from a vigilant and competent naval power who would forcefully seek it's return or destruction is not a good starting premise without any of those nuances.

So here is my work in progress. Remember this is a energy/delta-vee map. Not a physical map of the Solar System although there is a relationship between distance and energy.

The way it works is that you generally start out on the green dots. For example Low Earth Orbit. The each pink dots you pass through takes 1 burn which equal 1 day of travel at a 1G Burn. White dots are free to move through. A pivot can be made at any intersection and cost 2 burns (and 2 days of travel). Blue circle with a -number means you subtract that number of burns from your total thus reducing your travel time due to the free delta-vee you gain.  White circle with a skull indicate a hazard roll needs to be made.

For example if you start out in Low Earth Orbit and want to go to Eureka towards the bottom right edge of the map. It will take 4 burns or 4 days at 1 G. You pass through the Transfer Orbit burn point then through the radiation hazard of the Van Allen Belt. The make another burn near Geosynchronous Orbit which can take you to the L2 Earth_Luna Lagrange Point. You then continue through the L5 Sol Mars Lagrange point. You then make two burns, and have to make a hazard check to match Eureka spin and latch on with grapples. Now you are station keeping with Eureka.

https://en.wikipedia.org/wiki/5261_Eureka

Is it even worth accounting for the varying orbits of the planets? As in the distances between them are in flux.

Quote from: Kiero on February 20, 2022, 05:17:07 PM
Is it even worth accounting for the varying orbits of the planets? As in the distances between them are in flux.

What he said.

The map is awesome, but what if the planets are in opposition?

Quote from: Kiero on February 20, 2022, 05:17:07 PM
Is it even worth accounting for the varying orbits of the planets? As in the distances between them are in flux.

It does to a point because it is a energy map not a position map. Since we are talking torch ships capable  of continuous thrust with applies to Traveller or the Expanse it is about as realistic as it gets for something that playable. Each pink dot represent 2.5 km of delta fee.

The game I adapted this from is used turns of a year because the focus on real world drives. With Traveller or Expanse style drive we are talking days.

It's graphically very satisfying, but with 1G of constant boost it seems like 4 days to L2 is a bit weird. Maybe if you set it to something like .1g for a more realistic setting. With 1G and no realistic restrictions on delta-v budget, the whole inner solar system is your oyster regardless of opposition within a couple days tops. Earth/Mars on average would be 2 days with flip and stop, for instance.

There are limits on burn time in The Expanse. They're mentioned in the books and discussed in the article I posted.

http://toughsf.blogspot.com/2019/10/the-expanses-epstein-drive.html

The limits on burn time are less obvious in the TV show than books, because we naturally assume that whenever people are seen walking on decks they're under acceleration. However, usually they're just clamping down with their magnetic boots, and other microgravity effects aren't shown because nobody can be bothered with it and 99% of the audience won't notice. It's the same as how we only once saw a coriolis effect on Ceres, with Miller's drink being poured and it twisting to one side - this was never shown again.

Most of the time we see people moving around on the Rocinante they're under microgravity or relatively low acceleration. As the blog article notes, a full use of the fuel would get them 0.1g for 40 days. That's 3,456km/sec of delta-V, covering about 80AU if they didn't turn and flip and decelerate at the halfway point.

So it's not unlimited, it's just fucking huge compared to anything we've got now. But the calculations tell us it'd be a 100TW drive, vs 18TW for all of Earth today. Using five times the entire current energy output of the human race just to have half a dozen people zip around having adventures is pretty nuts, but that's scifi for you.

Quote from: Panzerkraken on February 20, 2022, 11:52:43 PM
It's graphically very satisfying, but with 1G of constant boost it seems like 4 days to L2 is a bit weird.

Which L2?

Quote from: Panzerkraken on February 20, 2022, 11:52:43 PM
Maybe if you set it to something like .1g for a more realistic setting. With 1G and no realistic restrictions on delta-v budget, the whole inner solar system is your oyster regardless of opposition within a couple days tops. Earth/Mars on average would be 2 days with flip and stop, for instance.

I go by the table here as being more accurate than what in the Expanse RPG book.  It pegs Earth to Mars as a 4 day trip as a 1G Brachistochrone trajectory.

Spaceship Handbook Mission Table
http://www.projectrho.com/public_html/rocket/appmissiontable.php


Here some posts explaining the High Frontier Map
https://boardgamegeek.com/thread/868735/why-are-planets-static-high-frontier

The explanation of the High Frontier Map is down aways
http://www.projectrho.com/public_html/rocket/spacemaps.php

Quote from: estar on February 21, 2022, 12:37:52 AM
I go by the table here as being more accurate than what in the Expanse RPG book.  It pegs Earth to Mars as a 4 day trip as a 1G Brachistochrone trajectory.

Spaceship Handbook Mission Table
http://www.projectrho.com/public_html/rocket/appmissiontable.php

That table is for a round trip, it even says so.

Quote from: http://www.projectrho.com/public_html/rocket/appmissiontable.php link=http://www.projectrho.com/public_html/rocket/appmissiontable.php

Delta-v and Travel Time for ROUND Trips To or From Terra's Surface
(i.e., the "Mars" row gives data for both the TERRA-MARS-TERRA and the MARS-TERRA-MARS missions

I'm guessing the parachute icons represent aerobraking opportunities. Maybe I'm reading this wrong, but it seems to me like you put in an aerobrake from Mars flyby to Mars orbit, but NOT one for actually landing? What's the reasoning behind that?

Quote from: Premier on February 21, 2022, 08:31:03 AM
I'm guessing the parachute icons represent aerobraking opportunities. Maybe I'm reading this wrong, but it seems to me like you put in an aerobrake from Mars flyby to Mars orbit, but NOT one for actually landing? What's the reasoning behind that?

I omitted landing sites and landing burns from the High Frontier in favor of just a low orbit notation. Figuring that folks can figure out which method works best for getting to the surface including aerobraking landing if there is an atmosphere. But this is just a first pass so I may change my mind on that.

Quote from: Panzerkraken on February 21, 2022, 07:10:52 AM

That table is for a round trip, it even says so.

You are right that I misread it so in that case I recommend the following


.3 G = 1 days per burn
1 G = 1/2 day per burn
7 G = 1/6 day per burn
12 G = 1/8 day per burn