Jump travel time?

OnceFarOff's picture
OnceFarOff
July 25, 2012 - 7:48pm
Hey all,

Something that I have been trying to understand is how long it takes a ship to travel from A to B in the frontier. I get the whole "half the time accelerating, half decelerating" bit from the canon rules. In numerous places, I hear people refer to some ship, usually smaller/faster that can get from A to B faster than another. Maybe I'm dense, but don't all ships take 7 days on a 7 day jump route? Why does it matter if the ship has Ion engines or Atomic when it comes to jumping?
Comments:

Shadow Shack's picture
Shadow Shack
July 25, 2012 - 8:28pm
Accelerating to jump speed is the bulk of the journey, only because it takes an astrogator 10hrs per lt year to plot the course...and since he isn't working around the clock that time is typically a day per lt year. As that is done, the pilot is varying between acceleration and deceleration in the "general diretion" as the ship can get to jump speed much faster than the astrogator can crunch the numbers...but once the course is plotted the ship merely points in the right direction and nudges into the void...and then decelerates much more quickly on the other side.

So the big issue to faster jumping is either risk jumping or house ruling reduced plotting time via additional astrogators (or both).
I'm not overly fond of Zeb's Guide...nor do I have any qualms stating why. Tongue out

My SF website

TerlObar's picture
TerlObar
July 25, 2012 - 10:22pm
This is one of those areas where the rules are a little scitzophenic.  The AD rules say that it is one day per light year.  The KH rules say they accelerate at 1g until they reach 0.01c, jump, and then decelerate at 1g until they reach the station.  The KH skills say, as Shadow Shack pointed out, that it is 10hr/ly of plotting type.  Given 10 hrs of work per day that translates to 1 day per light year before the jump and then declerating afterwards.  Here's how I do it for standard Star Frontiers campaigns (I actually have a new house rule mechanic that is compatable and which I like better):

1) The AD rules were written before the KH system and they needed something and 1 day per ly makes the frontier big and it takes time to get places
2) I use the KH mechanics which in my opinion, superceeded the AD ones once the star ship rules were layed out.
3) Acclerating at 1g (assuming 1g is 10 m/s/s instead of 9.82 m/s/s), it takes 83.333 hours to reach jump speed and another 83.33 hours to decelerate on the other side. That's just over 4 days on each side of the jump so a typical jump takes about 8.5 days regardless of the distance.
4) Astrogation computations:  These have to be done before the jump. An astrogator can work 10hrs every day (20 hour period) so if he starts when the ship leaves station, he can only get a 4 ly jump plotted before jump time, anything longer extends the length of the jump time appropriately.  If you have more than 1 astrogator, they can work in shifts to get the job done faster.  In this case I just assume that between them they are working around the clock and the total time needed is divided by the number of astrogator, name 1 day per lightyear / # astrogaotors so if you are making an 8 light year jump (80 total hours of work) and you have two astrogator it only takes 4 days.  If you had 4 astrogators and they did nothing else you could get the computations done in 2 days.  The other option is for the astrogator to start before the ship leaves port.  If they know where the next destination is and when they are leaving they can get started and get most of the computations done before they leave the station so they are done before the 83.3 hours are up.  However if the departure time varies by more than a dayor two or they change destinations, they have to start over.

My alternate mechanic is this:  the computations take 10 hours, regardless of distance and can't (nor do they need to) start before you leave the station.  Then the ship has to travel for at least the 83.3 hours to get up to jump speed or a number of hours equal to the distance traveled in ly squared to properly get the ship lined up on the correct vector.  Use which ever is longer and the number of astrogators on board has no effect as long as you have at least one.  So if you are making a jump of 9 ly or less, the travel time is going to be the 8.5 days.  For a 10 ly jump the outbound time is 100 hours and then you need the 83.3 hours to decelerate at the other side so your total time is now about 9.5 days.  And it starts to increase from there.  The 14 ly jump from Pregnlar to Garna Garu takes 14x14=196 hours outbound and 83.3 inbound for a trip just over 14 days.  The shorter jumps take longer just to get up to jump speed but the longer ones are basically right on with the 1 day per light year travel time.  These times can be reduced by risk jumping which could be either using higher acclerations which wear out the crew or jumping early before the ship is completely lined up. 
Ad Astra Per Ardua!
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jedion357's picture
jedion357
July 25, 2012 - 10:42pm
Now here's the other shoe, 1ADF is faster than one g. And accel at or more ADF will take a ship to jump speed much faster. I know that the g forces involved would be tough on the human body but since the system by default assumes that the core four can handle such g forces i assume that really smart scientist within the setting have applied their brains to solve the problem. For example the inertia field and other ill explained technology in the setting suggests applications for solving the g force issue of a star ship accelerating at high ADF or the violence inherit to biological components of a warship maneuvering or accelerating at 4 to 5 ADF.
I might not be a dralasite, vrusk or yazirian but I do play one in Star Frontiers!

TerlObar's picture
TerlObar
July 26, 2012 - 7:03am
Yes there is that as well.  The factor is 2.78 and if you accelerate at 1 ADF on the board game for 180 turns you reach 0.01c.  180 turns = 30 hours = 1.5 days which is much faster than the 83.3 hours.  But you still have to get the computations done first so in practice it probably doesn't save you much.

Personally, I think that was probably an error of the playtesting and working it out in the first place as reading through the text, to me at least, seems to imply that 1 ADF was supposed to be 1g of acceleration.  Plus I suspect the boardgame was developed somewhat independently from the RPG rules.  If you change the hex size from 10,000 km to 3600 km then it all works out perfectly with no other changes Smile.  For my games, I choose to treat the rules for the board game as separate from the RPG side, kind of like an adaptation for fun playability in that format, and say jumps take the longer time, not those implied by the board game rules.
Ad Astra Per Ardua!
Webmaster - The Star Frontiers Network & this site
Founding Editor - The Frontier Explorer Magazine
Managing Editor - The Star Frontiersman Magazine

OnceFarOff's picture
OnceFarOff
July 26, 2012 - 7:03am
Thanks for the replies. I'm getting that the rules are schizophrenic to be sure. Cool

I'm trying to think of an instance in the canon material where I heard of an atomic powered freighter being able to 'get there faster'... I'm assuming that the instances where I have heard this said it's probably inferred that it's a matter of ADF differences as the lighter, faster ship has always been the one that is better than the big boys...

The fact that each of you points to your own house rules when it comes to describing how you handle this makes me feel better about doing the same...

gnytro's picture
gnytro
July 27, 2012 - 9:33pm
My house rules are little divergent from the way the game is written, but I find they work fairly well.

First off, I do not use the idea that (see the Hull Specification Chart, KH Expanded Rules, pg 11) larger ships need both more AND larger engines. In my games, all ships are designed to be fitted with Size A engines, and the travel time of one day per LY reflects that configuration. Bigger ships just need more engines.

For the record, I do realize that this creates a few quirks in the Hull Specs chart. For example, hull size 4 only needs one engine, while hull size 3 needs 2. I just ignore this, basically, explaining that advances in technology and design standards enable a few larger ships to operate more efficiently than older, smaller designs. This also gives the players a little more flexibility and choice when buying or designing a custom ship. It's a game, not (real at least) rocket science, I don't bother trying to fix every quirk in the written rules or my house rules.

Now, what about the Size B and C engines? They're bigger, they make your ship go faster. Size B gets two light years per day, Size C gets 3 per day. Certain megacorps on the frontier tease about type D (4ly/day) engines "coming soon", but noone has demonstrated a working prototype yet.

As with the rules as written, Chemical, Ion and Atomic drive types simply differ on the type and amount of fuel needed. Chemical drives are cheap, but the fuel is bulky and expensive. Atomic drives are expensive but require very little in the way of "fuel tanks".

I also house rule inner system movement rates for ships OUTSIDE OF COMBAT (for ship to ship combat, I defer to the KH rules as written). I use the 'orbit' (of the star) as the base unit of distance. With Size A engines, moving 1 orbit takes 1 hour. Size B engines get 2 orbits per hour, Size C get 3 orbits per hour. So in our own solar system, a ship with Size B engines travelling from mercury to earth would take 4 hours (mercury to venus is one orbit, venus to earth is another). I don't bother with relative orbital positions (meaning the chance that your target planet is on the "dark side" of the star from your starting point). I explain it away as calculated into the 'slingshot' effect navigators take advantage of in plotting in system courses, using the star's massive gravity field to their advantage. Besides, if I wanted 'hard science' recreations of starship travel, I'd probably be playing Traveler Wink

For short travel within an orbit, between a planet, moons, stations, points in an asteroid belt, etc. A quick and dirty roll of 3d10 minutes does the trick.
~ Rich
berentiu@gmail.com

gnytro's picture
gnytro
July 27, 2012 - 9:45pm
OnceFarOff wrote: "I'm trying to think of an instance in the canon material where I heard of an atomic powered freighter being able to 'get there faster'... I'm assuming that the instances where I have heard this said it's probably inferred that it's a matter of ADF differences as the lighter, faster ship has always been the one that is better than the big boys..."

Remember that all ships with Chemical Engines have an ADF of 1, regardless of size and number of engines. (KHe pg12)

Ion engines must calcuate ADF based on desired fuel consumption. (also KHe pg12)

Only Atomic Engines reference the ADF on the HUll Specs chart without modification, so in that sense, yes, they will generally accelerate and decelerate faster than the others, especially the small, agile hull sizes.
~ Rich
berentiu@gmail.com

jedion357's picture
jedion357
July 28, 2012 - 4:53am
@Gnytro: Mercury to Earth in a few hours, sounds like you're playing star trek. ;)
I might not be a dralasite, vrusk or yazirian but I do play one in Star Frontiers!

gnytro's picture
gnytro
July 28, 2012 - 10:31am
My games tend to be fairly fast and loose with the "science", and since unlike some other games, SF doesn't distinguish really between 'jump drives' and 'maneuver drives', I found it kind of silly that you could travel a light year in a day, but still take hours or days to wander around a system.

Also, my game campaign tends to focus away from actual space travel, whether its interplanetary or interstellar. Sometimes events happen on a ship during travel, but most of the action takes place on a station, moon, planet, asteroid belt, whatever.

On the rare occasion that ship to ship combat is called for, we just switch over to the KH rules as written, get out the counters and maps, and resolve things that way.
~ Rich
berentiu@gmail.com

Shadow Shack's picture
Shadow Shack
July 28, 2012 - 7:15pm
gnytro wrote:
, I found it kind of silly that you could travel a light year in a day,

Actually, it only takes a few seconds to travel the light-years worth of distance...it merly takes a few days to accelerate to that point where you can enter the void (where the FTL travel actually occurs). And truth be told, it only takes that long to accelerate to "FTL speed" from the course plotting time more than anything.
I'm not overly fond of Zeb's Guide...nor do I have any qualms stating why. Tongue out

My SF website