Travel times question
Travel times question
Page 153 of the beta has a 1G ship taking 333 minutes to travel 1,000,000km
Page 152 has travel calculations as "Time = 2 x Square Root of (distance/ acceleration)"
Time measured in minutes, distance is km.
Lets go with a 1G ship...
Square root of (1,000,000/1) is 1,000
2 times 1,000 is 2,000
But the table says 333 minutes
Is the table wrong or am I doing something wrong?
Page 152 has travel calculations as "Time = 2 x Square Root of (distance/ acceleration)"
Time measured in minutes, distance is km.
Lets go with a 1G ship...
Square root of (1,000,000/1) is 1,000
2 times 1,000 is 2,000
But the table says 333 minutes
Is the table wrong or am I doing something wrong?
 MongooseMatt
 Site Admin
 Posts: 14898
 Joined: Mon Aug 18, 2003 4:25 pm
Re: Travel times question
Yeah, the table is skewy.
It would be _really_ cool if someone could go through the table and send me corrections so I can stay focussed on High Guard
It would be _really_ cool if someone could go through the table and send me corrections so I can stay focussed on High Guard
Re: Travel times question
I noticed that as well, some time back, and figured out the math.
The table uses different units than the ubiquitous kilometer, 'G', and minute. The travel formulas are straight out of physics, so units matter.
Distance is best converted to meters, to match acceleration.
Acceleration is rounded to 10 meters per second squared per G of thrust (real gravity is about 9.8 meters per second squared) (Note: this is stated in the paragraph below the table, for reference.)
Using those values and units gives Time in seconds, which will need to converted to minutes or hours to make it more useful.
So, to use your example of 1,000,000 km at 1G
d = 1,000,000,000 m
a = 10 m/s/s
t = 2*sqrt(d/a) = 2*sqrt(1,000,000,000 m / 10 m/s^2)
= 2*sqrt(100,000,000 s^2)
= 2* 10,000 s = 20,000 seconds
= 20,000 s / 60 s/min = 333.333 minutes
I don't know if explaining that in the rules, or adding equations with that already done, would be easier.
Also, on that note, as I read the explanation again. It states that the travel time formulas use kilometers for distance. If kilometers are used the answer will be off, since acceleration is stated to be in meters (in the case of the above calculation turning 20,000 seconds into 632.5 seconds (10.5 minutes).
The table uses different units than the ubiquitous kilometer, 'G', and minute. The travel formulas are straight out of physics, so units matter.
Distance is best converted to meters, to match acceleration.
Acceleration is rounded to 10 meters per second squared per G of thrust (real gravity is about 9.8 meters per second squared) (Note: this is stated in the paragraph below the table, for reference.)
Using those values and units gives Time in seconds, which will need to converted to minutes or hours to make it more useful.
So, to use your example of 1,000,000 km at 1G
d = 1,000,000,000 m
a = 10 m/s/s
t = 2*sqrt(d/a) = 2*sqrt(1,000,000,000 m / 10 m/s^2)
= 2*sqrt(100,000,000 s^2)
= 2* 10,000 s = 20,000 seconds
= 20,000 s / 60 s/min = 333.333 minutes
I don't know if explaining that in the rules, or adding equations with that already done, would be easier.
Also, on that note, as I read the explanation again. It states that the travel time formulas use kilometers for distance. If kilometers are used the answer will be off, since acceleration is stated to be in meters (in the case of the above calculation turning 20,000 seconds into 632.5 seconds (10.5 minutes).
Re: Travel times question
Lee
Thanks for pointing out my math error and the inconsistency in the rules.
I'll stick the numbers in the table into Excel and post it, I have a feeling the table is fine now it's clear we're using metres, seconds and a rounded 1G.
Tim
Thanks for pointing out my math error and the inconsistency in the rules.
I'll stick the numbers in the table into Excel and post it, I have a feeling the table is fine now it's clear we're using metres, seconds and a rounded 1G.
Tim
Re: Travel times question
OK, so I knocked the table up in Excel extending to 10g for fun. The distances seem a little random to me, I would re do it out to 40 au, approximately the Kuiper Belt and as far as I'd want to go without jumping.
The table in the print friendly beta is basically right but there are typos.
For example, 1,000,000,000km at 4g and 5g is the same 3.3 days
1,000,000,000km at 3g I calculate at 4.2 days, the table has 3.7 days which is the time I get for that distance at 4g. Looks like someone copy/pasted the wrong columns.
I've stopped there at working out what's right and wrong.
Matt, I'll try sticking it into a Word table and mail you that and the Excel sheet.
The table in the print friendly beta is basically right but there are typos.
For example, 1,000,000,000km at 4g and 5g is the same 3.3 days
1,000,000,000km at 3g I calculate at 4.2 days, the table has 3.7 days which is the time I get for that distance at 4g. Looks like someone copy/pasted the wrong columns.
I've stopped there at working out what's right and wrong.
Matt, I'll try sticking it into a Word table and mail you that and the Excel sheet.

 Lesser Spotted Mongoose
 Posts: 746
 Joined: Tue Sep 08, 2015 12:54 am
Re: Travel times question
The 100 diameter limit of the largest star would be an appropriate limit on this chart.
Re: Travel times question
Depends on how comfortable people are with math, those that are can work out what they need from the formula won't need a table, some prefer a table. Some will use an estimate that fits their game's needs and ignore the math and table.
There's more to explore in most systems than just the main world, having an idea of the time it takes to get there is a good thing.
There's more to explore in most systems than just the main world, having an idea of the time it takes to get there is a good thing.

 Lesser Spotted Mongoose
 Posts: 746
 Joined: Tue Sep 08, 2015 12:54 am
Re: Travel times question
Agreed, but the problem is that things like Oort Clouds scale with the parent star. There's no convenient "fixed distance" for them. What you need for that is a separate table that scales "system features" like this by star size and mass.hiro wrote:There's more to explore in most systems than just the main world, having an idea of the time it takes to get there is a good thing.
Re: Travel times question
There's no need for a generic rules set to "scale system features", what on earth are you talking about?TenaciousTechhunter wrote:Agreed, but the problem is that things like Oort Clouds scale with the parent star. There's no convenient "fixed distance" for them. What you need for that is a separate table that scales "system features" like this by star size and mass.
There's no fixed distance for anything if you really want to get into the details, it's all moving. To model that is way too complex and gets away from the fun of playing the game.
If a GM wants to put something in the far outer system and the players want to go there, they'll have a departure point and a destination so a distance is easily figured/hand waved.
That's all they need and then if they want, a table or formula to work out the time to get there, if not, fine, hand wave that too!

 Lesser Spotted Mongoose
 Posts: 746
 Joined: Tue Sep 08, 2015 12:54 am
Re: Travel times question
Things like the "Oort Cloud", and "Kuiper Belt" are dependent on star mass and intensity; they won't be at a fixed distance for every star. So rather than using our "Kuiper Belt" as a benchmark, it would be better to have a chart that scales star system features of this sort, that are likely to be fairly universal across star systems. The regular travel times can then be limited to diameter limits.hiro wrote:There's no need for a generic rules set to "scale system features", what on earth are you talking about?TenaciousTechhunter wrote:Agreed, but the problem is that things like Oort Clouds scale with the parent star. There's no convenient "fixed distance" for them. What you need for that is a separate table that scales "system features" like this by star size and mass.
Re: Travel times question
hiro wrote:Lee
Thanks for pointing out my math error and the inconsistency in the rules.
I'll stick the numbers in the table into Excel and post it, I have a feeling the table is fine now it's clear we're using metres, seconds and a rounded 1G.
Tim
Glad it was helpful, Tim.
I was just as confused when I started looking at it.

 Weasel
 Posts: 32
 Joined: Sat Jan 02, 2010 10:50 am
 Location: Knoxville, TN
Re: Travel times question
Sorry to necro this, but I have stumbled upon this myself. Hiro, I was wondering if you could repost the spread sheet you did. I would be very grateful  especially if you did go all the way up to 10G (I like playing with High Technology from High Guard. ) If Hiro isn't active anymore, does anyone else have that information? Fully correct charts to 10G would be frikkin awesome! I have made 1520 ships using the rules in High Guard, almost all of them with higher than TL15 tech, though I tend to discard the costs, because heck with that jazz, and I can go back if I really need to. One of these is an advanced heavy fighter capable of 10G thrust, basically as fast as missiles. (Yeeha!) So, having that chart go up to 10G would be great.
I tried to follow the math in the earlier posts, but my math skills are not what they used to be, so I flubbed it.
I tried to follow the math in the earlier posts, but my math skills are not what they used to be, so I flubbed it.

 Cosmic Mongoose
 Posts: 4192
 Joined: Wed Dec 23, 2015 2:49 pm
 Location: Sweden
Re: Travel times question
The table in the Core book looks correct?
The formula is given on p152 and is in standard SIunits: metres, seconds and acceleration in m/s².
Spreadsheet: https://www.dropbox.com/s/6yujq1yliwmbb ... .xlsx?dl=1
Re: Travel times question
The table in my copy is only mostly correct. The last few entries in the 4g column are copied from the 3g column. IF I remember right, 1e had the same problem. They just copied and pasted an incorrect table.

 Weasel
 Posts: 32
 Joined: Sat Jan 02, 2010 10:50 am
 Location: Knoxville, TN
Re: Travel times question
Thank you sir.AnotherDilbert wrote: ↑Wed Mar 18, 2020 6:35 pmSpreadsheet: https://www.dropbox.com/s/6yujq1yliwmbb ... .xlsx?dl=1

 Greater Spotted Mongoose
 Posts: 1266
 Joined: Mon Dec 15, 2008 3:17 am
 Location: Roy, WA USA
Re: Travel times question
Hi all,
My PDF CRB 2e copy has 4G and 5G the 600,000,000, 900,000,000, and 1,000,000,000 taking the same timed of 60.9h, 74.5h, and 3.3 days.
Thank you AnotherDilbert for your spreadsheet.
My PDF CRB 2e copy has 4G and 5G the 600,000,000, 900,000,000, and 1,000,000,000 taking the same timed of 60.9h, 74.5h, and 3.3 days.
Thank you AnotherDilbert for your spreadsheet.
snrdg121408 (aka Tom R)
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