[TML] Jump variation

[Jerry W Barrington]

On 8/28/07 2:17 PM, shadow at shadowgard.com wrote:

> On 27 Aug 2007 at 12:43, Jerry W Barrington wrote:
> 
>> I was reading http://www.freelancetraveller.com/features/rules/jumpimpl.html
>> today, and had a thought.  Over very long range, it is difficult to use
>> active sensors, so detecting jump signatures would likely use passive.
> 
> By *definition* jump flash is detected using passive sensors, since
> it is detecting a signal *emitted* by the ship that is entering or
> leaving jump.

Passive/active was a poor word choice.  The main thing I'm concerned with on
this issue is the momentary nature of the flash.

> Actually, contrary to what that page says, one rather major component
> will be *gravity* waves. You've suddenly dropped 100 or more toms of
> ship into an area that was empty a bit ago. That means the ship's
> mass will send quite a ripple thru spacetime.
> 
> Without knowin more about how jump works we can't say for sure, but
> I'd be willing to make a bet that even the crude crude gravity wave
> detectors we have on earth would pick something like that up clearly
> anywhere within several AU.

I had always assumed gravity would be the major "flash".  The Fiery class
close escort seemed to be unusual in having a bright visible flash, not
commonplace.  (MegaTraveller Journal #2, p31, and that's not even canon.  In
Classic Supplements 7 and 9, Fiery is mentioned, but not the flash.)  But
even the gravitic effect falls of like other radiation and has the same
problems as with detecting and measuring any flash... ->

> It's supposed to be unique. As in a very *distinctive* sort of
> signal. 
> 
> Think of it as shooting off a big flashbulb of an odd color. It's
> easily detectable both because it's an odd color and because it's a
> sudden signal spike.

True, and if you're walking down the street at night and a flashbulb goes
off 200 feet away, you're likely to notice it (if you're looking the right
direction).  But that notice won't be enough to give you targeting info,
which is just about what would be needed for the jump estimates in the
article.  Was it an X flashbulb at 200 ft, or a 4X at 400 ft, or any of an
infinite variety of combinations.  Noticing an instant flash doesn't really
tell you that.  The article assumes the target is right on the jump limit,
leading to... ->

>> For that matter, just how variable is the exit point?  The only reference I
>> can find is JTAS 24, pg 34-35: accurate to 1 in 10 billion, or about 3000 km
>> per parsec jumped (I calculate it to 3086km).  On a Jump 6, that could be a
>> few diameters!  Anything more canonical?
> 
> Don't forget that the exit point is variable around the point the
> astrogator aimed at. Which can be anywhere that's not inside the 100
> diameter limit of a body.

Yes, but my question is does canon have any actual rule/procedure for
determining exit point?  That one figure gives a variation up to 18516km at
jump six.  That much could matter (at least to me).



On 8/28/07 2:17 PM, Cougashika wrote:

> According to my Gravitics 101 (aka, Jumpspace for Dummies) text (no, I'm not
> telling where I got it, and no, you can't borrow it), the old "bowling ball on
> the fabric sheet" analogy works well in showing how gravity waves are used to
> detect ships coming out of jump.

Exactly the analogy I use, but remember that the ripples have intensity that
falls off as other radiation (inverse square law), and will only tell you
*direction* not location, and mass/distance^2 not simply mass!