Planetary Masking

[MasterGwydion]

Sun's Diameter* = 1.39 million km
Sun's 100D = 139 million km
Distance of Sun to Earth* = 150 million km
ie, as @Terry Mixon says, Earth is outside Suns 100D limit by 11 million km
Earth's Diameter* = 6,371 km = 0.006371 million km

12,756.27km. You have the radius.

Earth's 100D = 0.637100 million km.
* Source: NASA

So 100D would be 1.275627 million kilometers.

150 million - 0.6ish million = 149.4ish million. You all are correct.

 

[Arkathan]

No, it is roughly 1.4 million km in diameter, 865,370 miles.
Recheck the source you are using, and then verify it with another one, please.

 

[MasterGwydion]

No, it is roughly 1.4 million km in diameter, 865,370 miles.
Recheck the source you are using, and then verify it with another one, please.

I got My numbers from Space.com. I failed My math the first time.

 

[Longboat]

"Sir, the nav-screen says we're outside the star's masking...no, wait, we're inside the masking. I don't know about that, though, let me do a check on the board. Now, it says we're masked again.'

"Flip a coin and jump. Let's just see what happens."

 

[Condottiere]

The Sun orbits the Galactic Center at a distance of 24,000 to 28,000 light-years. Its distance from Earth defines the astronomical unit, which is about 1.496×108 kilometres or about 8 light-minutes. Its diameter is about 1,391,400 km (864,600 mi), 109 times that of Earth.

 

[rinku]

For ease of play, I just go with 100D of the star's nominal diameter. Most of the time the world is going to be definitely quite close or definitely quite far from the star anyway. As a rule of thumb, dwarfs less massive than Sol will have the hab zone within the star's jump shadow, while those that are more massive will have it outside. Since the exact number of hours it takes to get to the jump point rarely matters, you can just narrate it anyway.

Type M - take a day or two to clear. Flares might be an issue.
Type K - most of a day to clear.
Type G or bigger, or an outer system location - use the planet's diameter.

Giant stars might yield different results, though off hand their hab zones are usually far out as well.

Some worlds are inside the hab zone regardless of star type, too.

(And... who is to say that with a massive, spinning active fusion reaction that is filling space with all kinds of particles throughout its system, that gravity is the main problem that needs you to be clear by 10D or 100D?)

 

[Limpin Legin]

12,756.27km. You have the radius.

Oops, thanks for pointing that out. Glad we got there in the end.

 

[Sigtrygg]

Earth is Jump Masked.

Diameter of the Sun is roughly 140 million kilometers. 100D = 14 billion kilometers.
Diameter of Earth's orbit is roughly 940 million kilometers. Plus Earth's diameter and 100D limit... Earth's 100D limit is roughly 942 million kilometers.
Giving you a difference of roughly 12.5 billion kilometers.

Did I screw My math up? That doesn't seem right... ???

12000x100 = 1,200,000
12,000 is earth D x 100 is jump requirement.

 

[Sigtrygg]

Sun's Diameter* = 1.39 million km
Sun's 100D = 139 million km
Distance of Sun to Earth* = 150 million km
ie, as @Terry Mixon says, Earth is outside Suns 100D limit by 11 million km
Earth's Diameter* = 6,371 km = 0.006371 million km
Earth's 100D = 0.637100 million km.
* Source: NASA

I hate to say it but in that case NASA is wrong.
Earth RADIUS = 6,371km
Earth DIAMETER = ... double the above (12,742km)

 

[Sigtrygg]

Sun's diameter 1.3914 ×10⁹ m
100D 1.3914 ×10¹¹ m or 139,140,000km

 

[WHULorigan]

Diameter stands in for actual gravitational force.

Yes. It is an astrogator's approximation or rule-of thumb for normal everyday situations and operations.

I'm sure black holes are somewhat disproportional, to their presumed diameter.

Well, since the diameter of the actual Singularity (which is the only physical structural element) is Zero, ==> the 100D limit = 0. Which is not helpful. So yes, there is probably a different calculation method.

Remember that the "Event Horizon" is simply the radial locus of all points at which the escape velocity = lightspeed; it is a purely "mathematical" surface, not a physical one. There is nothing "at" the event horizon.

And the problems of "Frame Dragging" for a likely rotating Black Hole and its Static Limit above the Event Horizon would make additional interesting challenges.

 

[Longboat]

Not to mention elliptical orbits, where a world can be masked, then not masked part of the local year.

 

[Condottiere]

Seasonal trade winds.

 

[Limpin Legin]

I hate to say it but in that case NASA is wrong.
Earth RADIUS = 6,371km
Earth DIAMETER = ... double the above (12,742km)

I've checked it against the original source. "NASA", "Earth" and "6,371 km" are correct. It was "Diameter" that was a typo.

 

[Sigtrygg]

No wonder they lose spacecraft aimed at Mars if they get radius and diameter mixed up...

 

[Condottiere]

Details.

Imperium measurements, versus metric.

 

[Geir]

Not to mention elliptical orbits, where a world can be masked, then not masked part of the local year.

Or if your destination star crosses the mask of the star you're in (or going to) - then the mask can be much more impactful than the actual 100D (especially if you're jumping to a system with a high mass star, where the star is between you and your destination. Need to jump short or make a... rim shot? and then pass through the masked area.)

I use mass as a stand-in*, so pretty much any star dimmer than Sol is likely to have some masking from a habitable world, but the real question, much as with vector space combat, is: does this add to your Traveller campaign or does it just add to recordkeeping? Different people want different things.

*If you strictly use mass, then you also get weird effects on denser or less dense worlds. For instance, Mars turns out to be about 71ish diameters instead of 100. Pretty much you'd need to multiply by the density (Earth = 1) to determine how far out a mask would be for a planet rather than the standard 100D, using just gravity as the governing factor. But, see above.

 

[rinku]

Yes. It is an astrogator's approximation or rule-of thumb for normal everyday situations and operations.



Well, since the diameter of the actual Singularity (which is the only physical structural element) is Zero, ==> the 100D limit = 0. Which is not helpful. So yes, there is probably a different calculation method.

Remember that the "Event Horizon" is simply the radial locus of all points at which the escape velocity = lightspeed; it is a purely "mathematical" surface, not a physical one. There is nothing "at" the event horizon.

And the problems of "Frame Dragging" for a likely rotating Black Hole and its Static Limit above the Event Horizon would make additional interesting challenges.

I think it's fair that when you're dealing with such objects, they probably need their own rule about how close you can jump to them, not one designed for regular planets or stars. Happy to have a different rule for Stars and for gas giants for that matter. But I'll stick to simple.

At the other end of spectrum, Asteroid zones. Theoretically you could jump right into them, but potentially it could be hazardous, especially if that rock is a busy hub (Glisten would be a great example). Just traffic control considerations would mean an artificially imposed minimum jump in point, although ships jumping out might be okay to to so closer. A few thousand km feels about right - might as well use Medium Range.

 

[WHULorigan]

I think it's fair that when you're dealing with such objects, they probably need their own rule about how close you can jump to them, not one designed for regular planets or stars. Happy to have a different rule for Stars and for gas giants for that matter. But I'll stick to simple.

At the other end of spectrum, Asteroid zones. Theoretically you could jump right into them, but potentially it could be hazardous, especially if that rock is a busy hub (Glisten would be a great example). Just traffic control considerations would mean an artificially imposed minimum jump in point, although ships jumping out might be okay to to so closer. A few thousand km feels about right - might as well use Medium Range.

Singularities and Neutron Stars, definitely. In fact, even if you were using 100D (from an Event Horizon or otherwise) as a standard, there would be many other reasons you would NOT want to jump in that close.

 

[WHULorigan]

Or if your destination star crosses the mask of the star you're in (or going to) - then the mask can be much more impactful than the actual 100D (especially if you're jumping to a system with a high mass star, where the star is between you and your destination. Need to jump short or make a... rim shot? and then pass through the masked area.)

I use mass as a stand-in*, so pretty much any star dimmer than Sol is likely to have some masking from a habitable world, but the real question, much as with vector space combat, is: does this add to your Traveller campaign or does it just add to recordkeeping? Different people want different things.

*If you strictly use mass, then you also get weird effects on denser or less dense worlds. For instance, Mars turns out to be about 71ish diameters instead of 100. Pretty much you'd need to multiply by the density (Earth = 1) to determine how far out a mask would be for a planet rather than the standard 100D, using just gravity as the governing factor. But, see above.

Using tidal force gives somewhat better results, IIRC.