How close are orbital starports?

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phavoc
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Re: How close are orbital starports?

Postby phavoc » Fri Dec 15, 2017 2:48 pm

Larger stellar objects like gas giants, planets, moons and the larger planetoids should be relatively stable. But new stations, shifts of orbital debris, towed planetoids into new orbits, etc, etc, would be one of the reasons for regular updates to stellar charts. Nobody will know about the new station at moon Beta without an official survey getting it out into the navigation maps. The locals in a system would know, as might local star systems. That's one of the purposes of the regular survey, to maintain the official database and distribute the data across sectors. I would doubt that many, if any, merchants in say the capital sector are going to have an updated Spinward Marches sector map and database in their systems. They would only get one if they were going to head that way.

With the data capabilities of future computer systems they could get regular updates stored in their navigational systems, and might for reference purposes. Though I doubt anyone is going to spend any time updating all their navigational charts regularly unless they had need. that's just human nature.
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Re: How close are orbital starports?

Postby paltrysum » Fri Dec 15, 2017 4:52 pm

phavoc wrote:
Fri Dec 15, 2017 2:48 pm
I would doubt that many, if any, merchants in say the capital sector are going to have an updated Spinward Marches sector map and database in their systems. They would only get one if they were going to head that way.

With the data capabilities of future computer systems they could get regular updates stored in their navigational systems, and might for reference purposes. Though I doubt anyone is going to spend any time updating all their navigational charts regularly unless they had need. that's just human nature.
Maybe, but it seems to me that in a high-tech, interstellar society, it would just be automatic. You jump into a system on a major trade route, get pinged by the orbital starport which confirms the data your transponder is putting out, and you get a data dump that you don't even think about. In that data dump is relevant astrogational information, TNS reports, personal mail, your TAS high-passage coupons, etc.

I work at a tech company that produces data storage boxes that contain pedabytes of information. Both large enterprises and fairly small businesses use this gear to manage their data. The data is distributed and accessible to their network at incredible speeds and is completely automated. If this is available at TL-8 (is that where we are?) then I should think a starship plying the spacelanes would have access to a great deal more with full automation. In short, if one would want this type of information, it should be at his fingertips and wouldn't require a manual request for download.
"Spacers lead a sedentary life. They live at home, and their home is always with them—their starship, and so is their country—the depths of space."
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Re: How close are orbital starports?

Postby NOLATrav » Fri Dec 15, 2017 5:50 pm

BigDogsRunning wrote:
Thu Dec 14, 2017 4:26 pm
SNIP
Does anyone have thoughts regarding the Jump reference frame that resolves any of these issues? I'm assuming that someone has addressed these issues previously. Can anyone point me at a good explanation that will allow me to continue hand-waving the inconsistancies? :idea: :shock:
I don't know if this would count as a good explanation but T5 posits that jump travel is a distinct, direct straight line from departure to destination. Any body significant with significant gravitational force that intersects this line can cause a precipitation from jump space. This includes planetoids, stations, even other ships - as long as it masses more than the jumping ship. So that's how normal space bodies can interrupt jump space vessels - the gravitational energy reaches into multi-dimensional jump space and sucks you out like a vortex! :P

As far as the differences in proper motion, it is implied you plan to arrive on the leading edge of the destination's 100D sphere. If you arrive on time or early, the 100D limit automagically pulls you out of jump space right where wanted to be. If you're a little late, you wait for the destination to come to you; if you're really late you have to chase it.
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Re: How close are orbital starports?

Postby Condottiere » Sat Dec 16, 2017 12:28 am

A well maintained starship with a well trained and competent crew should be able to fall out of the rabbit hole more or less in one hundred and sixty eight hours, exactly where the astrogator had plotted.
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Re: How close are orbital starports?

Postby baithammer » Sat Dec 16, 2017 3:33 am

Condottiere wrote:
Sat Dec 16, 2017 12:28 am
A well maintained starship with a well trained and competent crew should be able to fall out of the rabbit hole more or less in one hundred and sixty eight hours, exactly where the astrogator had plotted.
The timing of arrival however has a deviation and with the target point also moving makes for a landing zone rather than a landing point. ( Hence, fleet coordination requires further steps to take this into account.)
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Re: How close are orbital starports?

Postby Condottiere » Sat Dec 16, 2017 11:45 am

Within whatever they consider the margin of error.

The farther you jump, the greater the allowance.

I don't think that's covered ... will have to look that up.
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Re: How close are orbital starports?

Postby baithammer » Sat Dec 16, 2017 12:51 pm

The deviation comes from the 148 + 6D6 hours roll, which with targets in motion leads to fairly big potential landing zone. ( That is without a misjump.)

MGT 2ed Main Book pg. 148.
Regardless of how far the ship
jumps, it always stays in jump space for roughly one
week (148 + 6D hours).
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Re: How close are orbital starports?

Postby Linwood » Sat Dec 16, 2017 3:42 pm

That implies the position error is not dependent on the length of the jump. Which might well be a consequence of the physics but feels a bit counterintuitive.
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Re: How close are orbital starports?

Postby AnotherDilbert » Sat Dec 16, 2017 6:33 pm

Temporal deviation is constant:
JTAS24, Jumpspace, p34 wrote: Jump takes 168 hours (±10%) to complete. This time is related to the nature of the alternate space being travelled in, and to the energy applied. Where time is a variable in travel in normal space, energy consumption is a variable in alternate space; time is a constant. Consequently, distance depends on the energy applied.

Spacial deviation is proportional to the length of the jump, but negligible:
JTAS24, Jumpspace, p34-35 wrote: Over a jump distance of one parsec, the arrival point of a ship can be predicted to within perhaps 3,000 kilometers (on larger jumps, the potential error is proportionally larger). Error in arrival location is also affected by the quality of drive tuning, and by the accuracy of the computer controlling the jump; these factors can increase jump error by a factor of ten.
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Re: How close are orbital starports?

Postby Condottiere » Sat Dec 16, 2017 8:10 pm

I'm going with that the lanthanum grid is more precise than the jump bubble.
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Re: How close are orbital starports?

Postby Linwood » Sun Dec 17, 2017 1:34 am

OK, this leads to a question that came up in my campaign last session. You are expecting the arrival of a freighter insystem. You know the mass of the freighter (a standard type R), what system it’s arriving from and when it’s due to arrive. How closely can you predict the point in your system where it will emerge in normal space?
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Re: How close are orbital starports?

Postby NOLATrav » Sun Dec 17, 2017 2:19 am

Interesting question.

If you use the T5 idea described above that Jump must be a straight line, and you know where the Type R is coming from, you should be able to fairly easily determine an area of space it is likely to arrive in. "Captain, the jump line indicates the vessel should precipitate near the 100D mark at 137 degrees relative to the galactic core/local sun axis."

That's still a pretty big area of space but narrowed down considerably. Without knowledge of the system it's coming from you'd have the whole 100 diameter sphere to watch. Even if you just used hex faces on a subsector map you can narrow down your target area to a specific 1/6 (~17%) of the sky at the 100D limit.

In MgT jump is 148+6D hours; 6D averages 21, or 169 hours for the average jump. I'd say actively scanning the target area for jump emergence distortions would be an Average Sensors task if you're in the area at the right time (say, 160 hours (6.7 days) after departure). YMMV

I suppose a smaller ship would be a Difficult task, while a larger one might be Routine. Hopefully the Type R makes its Jump roll!
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Re: How close are orbital starports?

Postby baithammer » Sun Dec 17, 2017 3:34 am

In MGT its noted under the stealth option for jump drives.
Normally, a ship that emerges into real space
will be automatically detected if it emerges within the
‘minimal’ detail range of the sensor.
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Re: How close are orbital starports?

Postby AnotherDilbert » Sun Dec 17, 2017 10:11 am

Linwood wrote: You are expecting the arrival of a freighter insystem. You know the mass of the freighter (a standard type R), what system it’s arriving from and when it’s due to arrive. How closely can you predict the point in your system where it will emerge in normal space?
Without any intruding jump shadow the freighter can aim for any point on the hemisphere of the 100D limit towards the origin system.

The problem is that the target planet probably moves at 20 - 1000 km/s, so a 15 h deviation in the jump duration will allow the planet to move 1 000 000 km or more (potentially much more). If the relative movement of the target planet perpendicular to the jump line is large, the jump exit will be rather unpredictable.

So, I would say a rough answer is: the freighter might arrive at any point on the hemisphere of the 100D limit towards the origin system, plus potentially up to a few million km further away.
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Re: How close are orbital starports?

Postby Linwood » Sun Dec 17, 2017 4:08 pm

NOLATrav wrote:
Sun Dec 17, 2017 2:19 am

I suppose a smaller ship would be a Difficult task, while a larger one might be Routine. Hopefully the Type R makes its Jump roll!
It did. But it emerged closer to the pirates than the Travellers.... :D
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Re: How close are orbital starports?

Postby phavoc » Sun Dec 17, 2017 6:35 pm

Predicting the exact arrival point should be more luck than anything else. You don't know how efficient the departure is going to be, so it's impossible to predict the arrival section. Maybe there was traffic or debris at the departure system that required an additional 30min of maneuvering before they could jump. The departure areas are going to vary as widely as the arrival ones.
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Re: How close are orbital starports?

Postby Condottiere » Tue Dec 19, 2017 5:32 am

Busy lanes are likely to be swept clear of debris.

Image
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Re: How close are orbital starports?

Postby Linwood » Tue Dec 19, 2017 8:02 pm

I’ve been pondering how to sweep for orbital debris. First a detailed sensor sweep (with a collection net) to map the debris. Then large debris chunks could be targeted with lasers or pushed onto a new vector by drones. Smaller debris would be more of a challenge - maybe an array of charged filaments to draw smaller debris into a different path? But you may only care about that in areas near habitats or orbital terminals where there’s likely to be people in vacc suits working outsides.
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Re: How close are orbital starports?

Postby NOLATrav » Tue Dec 19, 2017 9:48 pm

Linwood wrote:
Tue Dec 19, 2017 8:02 pm
I’ve been pondering how to sweep for orbital debris. SNIP
Back during MgT 1e, Spica Publishing released the excellent Career Books detailing additional careers, one of which was Cosmonaut (specializations of Boat Jockey, Vacc Monkey and Search & Rescue) which were centered on the space around orbital highports and other orbiting installations. I had a PC ex-S&R tech who in a down and out period focused on sweeping orbital debris for scavenge over a balkanized world. Her solution was modifying a scavenged jump net, magnetizing it and then doing a slow orbit with it trailing behind her ship's boat when nobody was really looking. She eventually got noticed by the Imperial SPA and she sold her idea for enough cash to get her, her comrades and her ship's boat out of that system and on to bigger and better things.

The best part was the player took a bit of fluff and color I provided and made a scenario out of it. Supercool little campaign digression and her team never paid for fuel, berthing or lodging in that system again :)

Of course now I understand I was too generous because ferrous metals are unlikely in satellites and such due to weight but it was such a fun idea we ran with it and I'm glad we did.

I still use those great Spica books with 2e. Just update a couple skill listings here and there and good to go!
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Re: How close are orbital starports?

Postby baithammer » Tue Dec 19, 2017 11:33 pm

MGT 2ed, jumping out tends to take care of debris smaller than the jumping ship, not to mention the 100 diameter limit tends not to have much debris anyways.

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