So, judging by a discussion about this over at the MeWe SF group, there aren't any rules dictating how fast ships travel within a system. KH doesn't cover this, as it's only interested in interstallar travel, not intrasystem. So there's a gap there in our picture. It seems speed is only relevant really WRT combat and, although that's possibly within a system, it doesn't give a hint about how fast a ship can travel generally when not in combat or to and from a jump.

I do wonder if it's possible to generate some numbers and speeds based on a ships ADF, but I don't know how feasible that is...

Any ideas?

There's still a gap in the way things work though. If a ion drive is 'slow' (ADF 1) what exactly does that mean in terms of how long it takes to get from A to B in a system? It also suggests that atomic drives are faster, possibly also chemical drives, but we're not told by how much. There's mention of chemical drives being able to travel at 10,000 kph so that they can make a round trip on one fuel load, but that's extremely slow and the time/distance of a round trip is not given.

Anyway, it might be a fun exercise to design this system ship for a Frontier Explorer article. I think I'll just have to say that the ship takes 'a few days' to get to the asteroid belt. It's going there to find an NPC ship. I've also worked up a quick doodle of this:

Tell me how far you want to go and the acceleration you want to have the players endure and I can calculate it for you.  If I remember one ADF is more than 1G of acceleration and hard to endure for long durations.

I want to keep things simple, so possibly it's a straight run to the asteroid at 1G. I've invented an asteroid belt within the Madderley's Star system, as the adventure starts on Kdikit. I've no idea what the distance would be.

They probably didn't include system travel times because calculating those is really hairy. What are the orbital velocities of your start and destination? It's supposed to use one load of fuel to make one trip; how much delta-V can a chemical drive produce?

Fortunately, this sort of thing can be hand-waved by the referee. "The trip will take four months." "Four months! But last time it only took two weeks!" "That was three months ago. Inner Reach is on the other side of Dramune now."

I would tend to err on the side of shorter travel times, assuming Frontier chemical engines are much better than anything we have.

Going by the discussion over at MeWe, chem drives aren't very practical just becaue of the amount of fuel that has to be taken with them to get any distance. Ion drives seem like a better option, as they can carry a lot of fuel. So I may go with that option - possibly there's a chance for a slightly new ion engine design, that has a limiter so that it can't reach the speeds needed for a jump.

But maybe that's just too much detail. I think I'l just say that there's an asteroid belt in the system (Madderleys Star) and it takes 2 days to get via system to ship from Kdikit.

In the meantime, here's some more quick doodles - the second image is the NPC ship that the players will be looking for, a dralasite design:

Slap me upside the head! I believe the 2001 and 2010 Space Odyssey modules provide a few rudimentary rules for, shall we say, primative system ships.

The 2001 module provides the new Star Frontiers skill of Astronomy (hmm, sounds a bid Zebs like), and system navigation for plotting courses within a system.

On a star map, "the Leonov can move into any adjacent hex on map 8 every 6 hours. After the Discovery is repaired in chapter 3, it too, can move into any adjacent hex every 6 hours..."

The scale on map six is one hex = 100,000 kilometers... Isn't that 10 times the size of a Knight Hawks hex? 

The rules also provide info on aerobraking in Jupiter's atmosphere and using Jupiter's gravity to slingshot back toward Earth.

Again, one could view these as rules for very out of date system ships, but they provide a few ideas.

 

Understood, but, yess the modules have some interesting things that can be incorporated into the game such as a luner exploration vehicle and the like. I used to own the modules (along with all the rest of the pieces of the original game), though I never had a chance to use them... The 2001 module has a place where you can play ape men... I think I would have avoided that. 

Late to this discussion but here are some numbers you can work with.  As someone said, this is really tricky because it really depends on the positions of the objects and their orbits.  Also, this assumes you have ion drives on your ships.  Chem drives work around a planet and it's moons but if you really want to get anywhere on a timescale less than months or years inside a star system, you need ion or atomic drives to sustain constant thrust.  Anyway, here are some rough numbers.

Accelerating at 1g (which I set to 10m/s/s for SF), it takes just over 83 hours to get up to Void speed (3,000 km/s).  In that time you cover 3 AU and you are traveling at a speed of just over 1 AU every 13.8 hours.  So let's assume you stop just before jump speed and reach a maxium velocity of 1 AU every 14 hours.  And it would take another 3 AU and 83 hours to slow down at your destination.

For a trip over 6 AU, the travel time is just 166 hours plus the distance over 6 AU times 14 hours.  So getting from Earth to Neptune, a distance of 30 +/- 1 AU depending on the relative positions of the planets, would be 166 hours under acceleration at the start and end, and 24x14=336 hours coasting +/- 14 hours.  So going with the average, it would take 502 hours or just over 25 days to make the trip.

For trips under 6 AU the travel time will be under 166 hours (8.3 days) and will depend on the distance traveled.  You spend the first half of the trip speeding up, then flip over and spend the second half of the trip slowing down.  Here's a table you can extrapolate between:

1 AU - 68 hours

2 AU - 96 hours

3 AU - 118 hours

4 AU - 136 hours

5 AU - 152 hours

6 AU - 166 hours

It's not linear since you don't get up to as high a speed on the shorter trips.

You just have to decide how far it is from your starting point to the ending point and then you can estimate the travel time.  When traveling in the inner system, it's going to depend a lot on the relative positions of the planets.  For example, traveling from Earth to Venus could be as little as 0.3 AU if they are at their closest point (inferior conjunction), a travel time of only 37 hours, or as much as 1.7 AU if they are at their farthest distance (superior conjuction), a travel time of 89 hours (plus a little bit as you have to dodge the sun).  For going to the outer planets (beyond Jupiter) from the inner ones, it's just the time based on the orbital distance of the destination +/- 14 hours per AU for the orbital distance of the origin.

Hopefully that helps.

Very interesting - thanks!

For the plot, I think I'll just have to work on the assumption that there's an asteroid belt two days out by ion engine from Kdikit. Hopefully it's not really important to anyone exactly how far away that is in terms of outright distance.

Great stuff! You should put it in an article for the magazine. It's a clear help to the mathematically challenged here... like myself.

KH has very limited rules pertaining to chemical drives. ADF is always one and a load of fuel is 250Cr/doubled if taking off from a planet, and that load gets used over the course of the journey. That's pretty much it.

I did an expansion when I was drumming up my Historical Adventures pf:100 project, it can be found here: http://starfrontiers.us/node/3691

Side Note- Stars Without Number rules handles things this way, or at least as I remember.

within a zone like planet to moon- 1 dice something hours

leaving a zone inner system to mid system 1 dice days

multiple zones inner system to outer system 1 dice weeks.

Which begs the inevitable question: what if a chem-drive ship has sufficient fuel tankage and simply installs a jump-governor to prevent it from entering the void? An ion drive holds 10,000 units of fuel regardless of ship size, so why couldn't a system ship hold a slew of fuel too? Not so powerful anymore...

Seriously though, it's like comparing gas driven automobiles to electric vehicles. Both perform similarily on the road but the electric has a much more limited range due to charging time and battery "life" per charge. To say the gas engine is more powerful because it goes further is the same argument.

So one is not more powerful than the other, rather one simply has a greater range.

At one-tenth you're already halfway to an alternative. SF only requires you to accelerate to 1/100 light speed.  

There's my ruleset for the Void Drive...

thanks