Everything I know about Jump I learned from MWM

[Antony]

There is nothing in canon as far as I know but when Antares does supernova, inevitable given the stars mass, do people think there would be an effect on local jump space?

Looking up further information online on Antares it is classed as an irregular or semi-regular variable and is egg-shaped. It apparently has a very strong stellar wind which has also given the system a nebula which the -b companion illuminates.

What would be left of Antares after this could be anything from a neutron star to a black hole. Systems within about 7-8 parsecs may also suffer a few problems.

 

[atpollard]

I can only assume this is due to lack of attention to my post in your hurry to ignore its content, or simply an attempt to make your point in a more dramatic and contentious manner.

I have to say that either reflects poorly on your reliability, dedication to scientific accuracy, or ability to contribute helpfully.

Could we try to maintain a little more personal civility, please?

 

[rancke]

How would this work?

The world orbits Antares C, a star too dim to be seen from Earth, say a K5 V (Or in an orbit that never allows it to be seen from Earth??). It was captured by the other two stars a few million years ago, but it is billions of years old itself and the biosphere evolved quite naturally.

That way the only singular feature is the capture of one old star by a young binary system, and I don't think that's so extraordinary, is it?

EDIT: Note that I've no idea how dim a star would have to be to be invisible on Earth today from a distance of 600 ly; the K5 V is just a wild guess.


Hans

 

[Andrew Boulton]

<sigh>

Enough.

I know this thread covers some controversial topics, but that's all the more reason to think before you post. Disagreeing is fine, abuse and trolling aren't.

Settle down.

 

[E.D.Quibell]

[As for me and my Traveller, we Shadow but do not Mask ... what business does an alternate universe have being yolked to the normal universe except at the points where they converge - the start and end of a jump!]

I do the same. Basically because it's easy to jump shadow but hard to jump mask.

I really don't want to have to work out the relative positions of the stars and planets, not only between them in system, but also in every other system in relation to them and then keep a running log of where they all are!

The effort to do so outways the enjoyment I would get from refing it, and MTU is only a jump 1 one.

Best regards,

Ewan

 

[McPerth]

Obviously it's possible to ignore it. It's been ignored for over 30 years by writers and referees alike, myself included (Though I did include it as a minor plot point in one adventure I wrote for JTAS Online).

But what does a referee do if he doesn't want to ignore it? He is completely on his own. So is this something that comes up sufficiently often to warrant inclusion in the rules? What if it comes up every other jump? What about 19 jumps in 20?

Personally, I've never played it, and not even know much about jump making/shadow. I guess it is better described in GT, and I've never readed anything of it (though perhaps this would change, as I've readed very good comments about it in this board).

I think most of its effect depends on how do you understand jumpspace, as (AFAIK) is not described in any detail level in canon (the only things I readed about it are on the style of not fully understood).

As I've played it, I imagine it more or less as folding the paper, so joining the points. If so, the 100 radii of any body are only important in the jump initial point and its exit point, as all the rest are on the 'paper folded', and so out of the way.

If you see it as a parallel space where speed works differently, of course there can be gravitational effects of large bodies on it, but I guess the most important are the ones in the jump starting and ending systems. My thought is if we can see a star from the starting system, nothing is masking/shadowing it, so the way between systems is 'clear'.

Of course (and as always), I may well be wrong, as (as I said before) I hav no clear concept of this jump masking or shadowing, not havieng readed about them away of this board (surely it's in the versions I've never played/readed).

According to FT, 1 in 20 jumps is a free jump, i.e. affected by neither jump shadowing nor jump masking. Ignoring jump masking, a good guesstimate would be that more than 50% of mainworlds are inside a jump shadow. (See for yourself; grab a subsector listing with star types and count the number of KV and MV stars).

It also seems quite low for me the possibility of a free jump, but what's the probability in our own system that neither the 100 radii of the sun nor any of the outer (and larger) bodies block the way trom the jump point to the earth? I won't dare to calculate it, but perhaps samller that I assumed in the begining.

 

[McPerth]

I have wasted enough of my time on this thread and on this board.

I miss you then, as your points (even if sometimes too heated) were interesting, as were those of you opponents. I personally think your time was not wasted, at least for those who readed (not being heated by them) your posts.

 

[captainjack]

How would this work?

The world orbits Antares C, a star too dim to be seen from Earth, say a K5 V (Or in an orbit that never allows it to be seen from Earth??). It was captured by the other two stars a few million years ago, but it is billions of years old itself and the biosphere evolved quite naturally.

That way the only singular feature is the capture of one old star by a young binary system, and I don't think that's so extraordinary, is it?

EDIT: Note that I've no idea how dim a star would have to be to be invisible on Earth today from a distance of 600 ly; the K5 V is just a wild guess.


Hans

The third star is a good idea, but given that we've been resolving planets that orbit stars, my guess is that even 600ly isn't enough to miss it. I could well be wrong.

I do think the wanderer is the way to go, though. It seems an inordinately low probability event, but just what Traveller and its literature thrives on -Niven's worlds were a collection of oddballs, and Anderson based many stories on low probability / big universe to occur ideas.

Is there a nearby star ? keep in mind, too, that once it freezes, it could wander for a long time. The only issue would be its internal heat dissipating.

 

[Antony]

I've got it, based on my previous post that the world is actually a giant sub-light starship;

Why is it where it is. It is in the Antares system at that distance refuelling from the very strong stellar wind that Antares generates. It is at that distance because it's on board "fuel scoops" cannot cope with the wind any closer to the star.

Then one day the on-board AI determines that the ship is fully charged and begins to accelerate out of the system on the next leg of its journey. Accelerating up to a respectable STL speed using a drive system no one has a concept of. The AI not paying any attention to the huge numbers of life forms on its outer hull as the "atmospere" starts to freeze out. etc.

 

[MarianLH]

If you're using gravity to define a pseudo-100D limit, then it's better to set the gravity to be constant (e.g. 0.001 m/s²). The jump shadow will vary in size depending on the planet's mass, but at least it'll feel like it makes some kind of physical sense.

How does one find the jump limit of a given planet in this case? That is, at what distance does a planet's gravitational effect drop to 0.001 m/s²?

 

[BytePro]

The 100D is not directly related to gravity as a rule mechanic (i.e. the 'equation' does no involve gravity).

To give it some kind of 'physical sense' use gravitational gradient instead... represents rate of change in gravity rather than an actual measure - gravity falls off at a given rate.

For jump, the gravitational gradient is safe at 100D... where the gravity could be anything...

 

[MarianLH]

The 100D is not directly related to gravity as a rule mechanic (i.e. the 'equation' does no involve gravity).

Yes, I know, but the post I quoted is proposing an ATU where is does. I rather like the idea and would like to know how it would work.

 

[Rover]

Yes, I know, but the post I quoted is proposing an ATU where is does. I rather like the idea and would like to know how it would work.

Gravity is a function of mass and the distence from the center of that mass. There is an inverse square relationship between distance and gravitational effect. That is to say if your are twice the distance from the center of the earth, gravity will be one quarter. 10 times the distance and it will be 1/100th the gravity. 100D (200X the distance) you would have 1/4000th the gravity.

to calculate gravity you need to know the mass of both objects and the distance between thier centers. Here is an online calculator you can use.

http://easycalculation.com/physics/classical-physics/newtons-law.php

Typically the mass of something insignificant compared to a planet can be ignored. that is the gravity you excert on the earth is insignificant compared to what the earth excerts on you. Something larger, say the moon, can have an effect, That is where the tides come from.

the 100D rule is simpler for game play, but if you really want to do all that math, more power to you.

R

 

[MarianLH]

Thanks!

 

[McPerth]

Gravity is a function of mass and the distence from the center of that mass. There is an inverse square relationship between distance and gravitational effect. That is to say if your are twice the distance from the center of the earth, gravity will be one quarter. 10 times the distance and it will be 1/100th the gravity. 100D (200X the distance) you would have 1/4000th the gravity.

to calculate gravity you need to know the mass of both objects and the distance between thier centers. Here is an online calculator you can use.

http://easycalculation.com/physics/classical-physics/newtons-law.php

Typically the mass of something insignificant compared to a planet can be ignored. that is the gravity you excert on the earth is insignificant compared to what the earth excerts on you. Something larger, say the moon, can have an effect, That is where the tides come from.

the 100D rule is simpler for game play, but if you really want to do all that math, more power to you.

R

Sure it would be quite more exact (or at least scientifically sound), but also quite more complicated for the referee to calculate if this is really important for the adventure they're playing (and pointless if not ).

In 2300 AD something like what you're saying is used to calculate the gravitational limits for the 0.1 G and 0.001 G thresholds, but in 2300 AD world, the playable universe uses to be quite smaller than in Traveller, so it's easier to keep the things bearable.

I'm affraid we sometimes forget people plays Traveller (or any other game, for what is worth) for amusement, so we should always think about the realism (understood as scientifically sound)/simplicity/game effect/fun ratios before changing rules or assumptions (at least officially, of course anyone is free to discuss the scientifically soundness of any rule).

 

[Hemdian]

I did some analysis and calculations about the 100D rule way back in 1995. Check out this article which calculates drop off, takes density into account, looks at the effect of multiple bodies and Lagrange points, and what happens if you enage jump drive while still on the landing pad of the starport! (Task difficulties are from MT.) Basically, if you want to use simple gravity then you end up with the 100D limit of the primary star engulfing many mainworlds, for example Sol's 100D limit is 4.49AUs which is almost out to Jupiter.

Also in that article was a reworking using the alternative 'tidal force' idea ... which fits closer but the math is a bit messy.

 

[Rover]

I did some analysis and calculations about the 100D rule way back in 1995. Check out this article which calculates drop off, takes density into account, looks at the effect of multiple bodies and Lagrange points, and what happens if you enage jump drive while still on the landing pad of the starport! (Task difficulties are from MT.) Basically, if you want to use simple gravity then you end up with the 100D limit of the primary star engulfing many mainworlds, for example Sol's 100D limit is 4.49AUs which is almost out to Jupiter.

Also in that article was a reworking using the alternative 'tidal force' idea ... which fits closer but the math is a bit messy.

There is a problem with your math.

The Sun's Diameter is 1.392 Million kilometers.
http://en.wikipedia.org/wiki/Sun

Making the 100D limit about 140 million kilometers.

An AU is 149.6 million KM, larger than the 100D Limit. by about 10 million KM.
http://en.wikipedia.org/wiki/Astronomical_unit

R

 

[far-trader]

There is a problem with your math.

I think his math is on, but the explanation is muddy. Let's see if I can make it clearer, or just worse

I think he is talking the equivalent of the 100D mark for the Sun IF using a gravity rating equal to the 100D mark for a standard density world. Which ends up being huge.

I've seen the tidal force workups as well, and they seemed to come out close enough to 100D for worlds as to not be worth the effort. Presuming of course, which Traveller does, that the density of the worlds are standard.

Where it does make a difference is with large but low density objects. Like GG and Stars. And small but high density objects of course. In the first case allowing safe jumps at less than 100D and in the second requiring more than 100D. Significantly so in some cases.

 

[Rover]

OK, I see.When he said the 100D limit he was talking about a calculated minimum safe distance limit based on gravity and not the actual distance of 100 solar diameters. Awkward wording.

But given that the sun's density is just under 1/4 of the earth's I would think the MSD limit would be much less than the 400 diameters posted above.

I'll have to go over the article again.

 

[captainjack]

Gravity is also a function of mass - and while the sun has a lower average density, it has way more mass. I suspect that if one is calculating the point where the suns gravitational effect drops off to (I think) [FONT=arial,helvetica]0.001 m/s² as asked in the earlierpost[/FONT] you will get a huge area in which jump is problematic.

If anyone cares, I approach it from the perspective that the 100D limit is an artifact of jumpspace and its relationship to normal space, not a characteristic of normal space. I could elaborate, but that isn't answering the earlier question.....and I'm trying to be good and not derail....