Shipboard Chronometers & Jump Space

[rancke]

8 hours little?

Not counting Earth motion, just solar system motion, 8 hours is 6,624,000 kms worth of not being where you expected it, or put another way, 20+ light seconds off.

Game mechanics ignore solar system motion. Since I'm no jump physicist I can't explain how that works exactly.

Or another other way, that's approximately 520D from Earth.

That's PLENTY of pirate match vee and plunder time, just for starters.

That would be just as much time for a system defense vessel to get within firing range of the pirate. So let's not go down that road, it has deep grooves worn in it.

Interesting point there, does that mean a ship with a 168 hour jump plan being chased might face a pursuing ship jumping two hours later with a 160 hour jump plan getting there ahead of the first ship?

I've always assumed so. Just bear in mind that the plan is always a 168 hour plan; you can't deliberately plan a 160 hour jump.


Hans

 

[Enoki]

Funny - in my 360 days aboard CV-61 USS Ranger from 11/85-12/87 I never once stood a 4-hour watch - or a 6-hour.

It was 12 consecutive on, 12 consecutive off, 7 days a week. 0700-1900 or 1900-0700.

I was in AIMD, and we had only two shifts. The 4-section watch only activated once we were in port, and then only to determine liberty - actual work schedules remained the same.

And how do you think we ran flight ops around the clock for days at a time? Not on one flight deck crew... we had shifts there as well.

You were part of the air wing then. Ship's crew stands 4 and 6 hour watches. The air wing operated differently.

 

[whartung]

As I understand it, we originally kept track of time basically by the sun.

From these observations we settled on 86,400 seconds being the length of day, and then we changed our definition of day from "one rotation of the Earth" to "86,400 second" as measured by an atomic clock.

Now, we spend our time adjusting our "real" time, the one we humans use, to sync up with the atomic clock. This is where leap seconds come from.

We measure the earths rotation by measuring when the meridian passes certain celestial objects (like the sun, but also other stars and quasars). Apparently we can achieve and accuracy down to 4ms.

So, our concept of time is bound to an atomic clock(s) somewhere, and pretty much everything else is synced to that.

Now, you can not fly atomic clocks around. If you do, they get out of sync. Relativity, et al.

Internal to the solar system, I think a radio beacon would be suitable for keeping system time in sync. "At the sound of the tone, it will be 1:00:00 AM…*ping*", in this case the receiver will "know" how far they are from the transmitter, and be able to compute the lag with reasonable accuracy.

So, if a ship flies to 100D, and does a final sync, and then Jumps, we know, when they entered jump space, their internal clock matched the standard clock.

What we don't know, is whether jump space skews the clock at all or not.

If not, then when the ship arrives, a process of establishing location, velocity, etc. can take place, and a new ping can be sent to the system standard clock and ideally the system clock is now synced to the standard clock.

However if jump DOES skew the clock, how deterministic is it? If it's deterministic, ideally it can be compensated for, and syncing happens.

If not then…moving clocks around won't sync up the empire, something else will have to do. Not quite sure what, however.

 

[BlackBat242]

The people I played with always considered that "168 hours +- 8 hours jump time" was to cover the variations in distance and j-space topography between two discrete points, not to be a random roll each time a jump was made.

Therefore, a given jump was a specific time duration within that limit - a jump between those two points was the same fixed time interval every time.

You rolled the variation the first time someone made that exact jump* and that was the result applied every time that exact jump was made.


The alternative was to roll the variation when you did the ship design - that was how fast that specific ship made a jump, and different ships had a different jump time. You could apply this to a whole class "as-built", and then individual ships would diverge from others of the class over time, due to differences in wear, maintenance, modification, etc.


Or you could do both - being aware that the combined variations could mean trips of between 152 and 184 hours!


Either way, we never had you roll the variation when you made a jump you had made before - the same trip in the same ship took exactly the same time.




* Or when the pre-purchased jump program was generated - the brief that came up in the navigator's console when the program was installed in the ship's computer would give the standard jump time for that jump (in your class ship) before you even tried to make the jump.

 

[BlackBat242]

You were part of the air wing then. Ship's crew stands 4 and 6 hour watches. The air wing operated differently.

Yes - but I was still aboard that ship along with people like my friend from 3MMR who did work one of those multi-block watch schedule.

And that is the point... vessels often have several different watch schedules operating at the same time, some of which are unique to a specific class of vessel..

 

[SanDragon]

Oh, no! Sixteen hours...

http://utzig.com/cgi-bin/iai/system_info.pl?Sectors=Core&Hex=2118



Strike two! Twenty hours!

http://utzig.com/cgi-bin/iai/system_info.pl?Sectors=Core&Hex=0140

 

[kilemall]

Game mechanics ignore solar system motion. Since I'm no jump physicist I can't explain how that works exactly.

Ahh, but as a referee, you ARE the physicist.

Still maintain that if one insists upon random arrival times, that jump will have to have a BIIIIIG safe zone built into the destination.

That would be just as much time for a system defense vessel to get within firing range of the pirate. So let's not go down that road, it has deep grooves worn in it.

Eh, just saying that FT Beowulf is not liking the lack of reliable 100-D jump location given a random arrival time.

I've always assumed so. Just bear in mind that the plan is always a 168 hour plan; you can't deliberately plan a 160 hour jump.

Hmm, may not be something one could set (or maybe one can, with the appropriate misjump risks), but that Generate programs should yield a known arrival time.

Perhaps you try it every 1000-second turn to move to another jump area and see if you can generate a 'faster' plan? At a certain point it's better to just go, but you might be able to 'head them off at the pass'- or someone do it to you.

 

[kilemall]

If not then…moving clocks around won't sync up the empire, something else will have to do. Not quite sure what, however.

I was thinking well known pulsars and variable stars that have a fixed cycle that can be detected across the whole swath of systems in a economic or political area, reference objects with cycles in seconds, minutes, days, years, millennia, etc.

Part of the survey would be to shoot the reference stars and note what the cycles look like, determine precise sync, and presto! precise time without any support sats, clocks, etc.

The other solution would be ye olde atomic clock per system, and you just set it to be synced with 'standard' time, whatever that is.

 

[rancke]

Still maintain that if one insists upon random arrival times, that jump will have to have a BIIIIIG safe zone built into the destination.

Not if you only have to worry about the motion of the destination world in its orbit.

What sort of safety are you thinking of?

Hmm, may not be something one could set (or maybe one can, with the appropriate misjump risks), but that Generate programs should yield a known arrival time.

By taking more time for the calculations than you potentially save, you can reduce the jump variation to +/- 1%.


Hans

 

[kilemall]

Not if you only have to worry about the motion of the destination world in its orbit.

That is certainly a valid entertainment IMTU choice, but that's not the actual physics of what is going on with planetary movement. Your choice, static planet for play, in motion just in planetary orbit, or the whole actual motion.

I want players to think 'never thought of that' and deal with the very different space enviornment, in a sense a character a theme AND a motif in addition to a setting.

That extra bit may not be what you want, so party on.

What sort of safety are you thinking of?

My assumption is that you do not want to ARRIVE in the 100-D limit anymore then you do jump. That is not explicitly stated at least in CT, and theoretically you can go 100-D then jump right into orbit if you have the right angle and vee. But personally I don't want ships jumping 30,000 km away from my planets.

The safety part is so you don't create a misjump from jumping too close (my IMTU rule), or at the very least not jump INTO the planet, which I have to think is an extinction level event at miminum given the 'entire ship is acting as a fusion bomb since you just materialized point blank into the planet's crust' effect.

By taking more time for the calculations than you potentially save, you can reduce the jump variation to +/- 1%.

I'm not familiar with that rule, but I certainly would expect commercial ships to do that to avoid costly delay in closing with their destination planet.

 

[rancke]

That is certainly a valid entertainment IMTU choice...

Unless posted in the IMTU forum or explicitly noted as an ATU (or, more likely, an MTU) feature, I don't state a fact or express an opinion about anything but the OTU. (Well... I try not to; I do blunder once in a while).

...but that's not the actual physics of what is going on with planetary movement. Your choice, static planet for play, in motion just in planetary orbit, or the whole actual motion.

It's also how things work in the OTU. According to the rules, you always arrive 100D from the destination. And the jump takes 168 +/- 10% hours (barring a misjump). If anything, the bit about the world moving in it's orbit is a deviation from the straight rules, predicated on the assumption that most jumps arrive at the 100D limit and that the rules simplify the 'most' to 'all'.

My assumption is that you do not want to ARRIVE in the 100-D limit anymore then you do jump.

Why wouldn't you? The rules (or was it Marc's essay?) say that if you hit a jump limit, you get precipitated out there quite safely.

That is not explicitly stated at least in CT...

I include the 30 years' worth of material produced since CT ceased to be valid evidence. Throwing it away just because it isn't CT seems to me to be a most abominable waste.

... and theoretically you can go 100-D then jump right into orbit if you have the right angle and vee.

No you can't, because you get precipitated out at the jump limit.

The safety part is so you don't create a misjump from jumping too close (my IMTU rule), or at the very least not jump INTO the planet, which I have to think is an extinction level event at miminum given the 'entire ship is acting as a fusion bomb since you just materialized point blank into the planet's crust' effect.

It's also a non-issue (except IYTU) since a ship is automatically (and safely) precipitated out at the jump limit.

I'm not familiar with that rule, but I certainly would expect commercial ships to do that to avoid costly delay in closing with their destination planet.

But since they don't, obviously using the normal method does not cause costly delays in closing with destination planets. Which would be the case if most jumps ended up with the ship somewhere along the jump limit with a vector neutral towards the destination.


Hans

 

[Ishmael]

Why wouldn't you? The rules (or was it Marc's essay?) say that if you hit a jump limit, you get precipitated out there quite safely.

Where does it discuss that in particular? I always thought that you couldn't exit inside the 100 diameter limit and if you tried it led to a rough exit as if misjumped. That would make the variable jump time and planetary movement something to seriously consider.

Oddly enough, it seems that nature has provided certain safegaurds which prevent an object from exiting jumpspace while inside the 100 diameter limit. Any craft whose jump vector calls for it to break into normal space within the 100 diameter limit automatically precipitates violently out of jumpspace upon reaching that limit. In some cases, this can cause severe damage to the ship or its crew (see Flight Controls).

While that quote is POV, it does support the conditions I mentioned considering timing and planet movement.

 

[whartung]

I was thinking well known pulsars and variable stars that have a fixed cycle that can be detected across the whole swath of systems in a economic or political area, reference objects with cycles in seconds, minutes, days, years, millennia, etc.

These only ensure that your clock is accurate from tic to tic, it doesn't tell you what time it is.

 

[whartung]

According to: http://content.time.com/time/health/article/0,8599,2114544,00.html

The solar system is moving at 11,000 kph.

16.8hr * 11,000 kph is 184,800 km. So, at that rate, that's the radius of margin for landing a jump. About 10hrs to your schedule with a 1G drive. Obviously other systems will have other velocities.

Haven't seen a chart for generating one in any of the system generation books.

 

[Condottiere]

Any signal beacon would have three bits of information:

1. The time

2. It's exact location

3. Rate of movement, if any

 

[whartung]

Any signal beacon would have three bits of information:

1. The time

2. It's exact location

3. Rate of movement, if any

Nobody disputes that, the problem is setting the time in the first place to a coordinated, intersystem standard. Intrasystem is easy, intersystem not necessarily so much (depending on Jump effect).

 

[kilemall]

These only ensure that your clock is accurate from tic to tic, it doesn't tell you what time it is.

Individually no, collectively yes, especially the ones that are on a longer cycle then hours or days, which is why I specified that as a requirement for the reference set as a whole.

Between comparing cycles across enough stars/objects and the observed changes in reference stars at different distances which would yield change in a few that are known to occur only at specific times in the reference object's life relative to the location you are at, you should be able to derive a time.

https://en.wikipedia.org/wiki/Mira_variable

As for level setting a time, a particularly useful method would be a reference star that has just gone supernova or increased its magnitude.

For X years past that point you could use the observed phenomena at the closest known point as a reference for 'what time it is' further away, with years of comparative astronomy at different star systems receiving the changed picture so the sequence of events and timing are well known.

Another methodology might be simply sending a radio signal with a time element throughout your known space, say spaced between every 100 LY, with a time coordinate being sent. Get the signal, read what time it is, know when and where it was sent from, perhaps do a cluster equivalent of such transmitters that operate as sort of a GPS constellation, and you can get both time and position.

Ah, here's a bit about using pulsars for navigation and time, that is what was used to define the solar system's position on the Voyager plaque. Better then human atomic clocks in some cases.

https://en.wikipedia.org/?title=Pulsar#Applications

 

[kilemall]

According to: http://content.time.com/time/health/article/0,8599,2114544,00.html

The solar system is moving at 11,000 kph.

16.8hr * 11,000 kph is 184,800 km. So, at that rate, that's the radius of margin for landing a jump. About 10hrs to your schedule with a 1G drive. Obviously other systems will have other velocities.

Haven't seen a chart for generating one in any of the system generation books.

Ya I read the article, but you are missing the spiral arm component, that's where the higher speed derives from. That's 11,000 kmh more relative to the local arm's motion, so the total is still on the high end I quoted re: an absolute position between now and 8 hours later.

 

[kilemall]

Rancke, I'm not going to argue a set of rules I have absolutely no interest in purchasing much less reading up on for jump physics that have evolved since CT. For the purposes of this conversation I can accept that this mechanic is now in place for most canon rules and that it is written for entertainment value, not consistency within a logical framework.

I will have to rely on the rest of you as to whether his statements are accurate for the other versions.

Still doesn't deal with the other safety and cost factor, wanting to drop in at least distance to destination as opposed to possibly several light seconds out.

If you can spend extra time doing a calc and getting it exactly right, well I expect most ships will do exactly that to avoid wasting hours traveling on the other end. Doubly so for a fleet action with a maneuver plan relative to planetary defenses.

And if the rules say you just always end up at 100-D even if you arrive 8 hours later then the plan, well I say the rules are ignoring planetary motion at the very least, or that you have a lot more control then is suggested by the jump plan mechanic.

 

[rancke]

Where does it discuss that in particular? I always thought that you couldn't exit inside the 100 diameter limit and if you tried it led to a rough exit as if misjumped. That would make the variable jump time and planetary movement something to seriously consider.

Marc Miller's Jumpspace essay in JTAS24, following a paragraph describing the dangers of entering jumpspace while inside a gravity well:

"On the other hand, there seems to be a built-in safety feature for ships trying to leave jump space within 100 diameters of a world. Ships naturally precipitate out of jump as they near the 100 diameter limit."​

The safety of the process I deduce from the fact that there's no mention of any danger, here or in any of the rules.

Oddly enough, it seems that nature has provided certain safegaurds which prevent an object from exiting jumpspace while inside the 100 diameter limit. Any craft whose jump vector calls for it to break into normal space within the 100 diameter limit automatically precipitates violently out of jumpspace upon reaching that limit. In some cases, this can cause severe damage to the ship or its crew (see Flight Controls).

While that quote is POV, it does support the conditions I mentioned considering timing and planet movement.

DGP has added the word 'violent' to the phrase. I quite agree that if you accept this addendum, then the rest of your argument follows. And all the rules ought to be amended to include the effects of avoiding hitting jump limits and the consequent additional travel time in destination systems.

My first reaction is to reject this addition, though. But that's often my reaction to being made aware of evidence of which I was previously unaware, so I'll have to think it over.


Hans