Travel times question

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hiro

Travel times question

Postby hiro » Mon Nov 30, 2015 7:40 am

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?
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MongooseMatt
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Re: Travel times question

Postby MongooseMatt » Fri Dec 04, 2015 10:45 am

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 :)
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Liodre
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Re: Travel times question

Postby Liodre » Fri Dec 04, 2015 2:00 pm

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).
hiro

Re: Travel times question

Postby hiro » Fri Dec 04, 2015 8:14 pm

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
hiro

Re: Travel times question

Postby hiro » Fri Dec 04, 2015 9:41 pm

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.

Image

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.
Tenacious-Techhunter
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Re: Travel times question

Postby Tenacious-Techhunter » Sat Dec 05, 2015 5:54 am

The 100 diameter limit of the largest star would be an appropriate limit on this chart.
hiro

Re: Travel times question

Postby hiro » Sat Dec 05, 2015 6:05 am

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.
Tenacious-Techhunter
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Re: Travel times question

Postby Tenacious-Techhunter » Sat Dec 05, 2015 7:19 am

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.
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

Re: Travel times question

Postby hiro » Sat Dec 05, 2015 10:47 pm

Tenacious-Techhunter 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 need for a generic rules set to "scale system features", what on earth are you talking about?

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!
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Re: Travel times question

Postby Tenacious-Techhunter » Sun Dec 06, 2015 1:13 am

hiro wrote:
Tenacious-Techhunter 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 need for a generic rules set to "scale system features", what on earth are you talking about?
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.
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Re: Travel times question

Postby Liodre » Sun Dec 06, 2015 4:10 pm

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.
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Re: Travel times question

Postby Randalthor66 » Wed Mar 18, 2020 4:22 pm

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. :D ) If Hiro isn't active anymore, does anyone else have that information? Fully correct charts to 10G would be frikkin awesome! I have made 15-20 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. (Yee-ha!) 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.
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Re: Travel times question

Postby AnotherDilbert » Wed Mar 18, 2020 6:35 pm

Image

The table in the Core book looks correct?

The formula is given on p152 and is in standard SI-units: metres, seconds and acceleration in m/s².

Spreadsheet: https://www.dropbox.com/s/6yujq1yliwmbb ... .xlsx?dl=1
Jeraa
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Re: Travel times question

Postby Jeraa » Wed Mar 18, 2020 6:47 pm

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.
Randalthor66
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Re: Travel times question

Postby Randalthor66 » Wed Mar 18, 2020 10:48 pm

Thank you sir.
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Re: Travel times question

Postby snrdg121408 » Wed Mar 18, 2020 11:15 pm

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.
snrdg121408 (aka Tom R)

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