Detection systems

[Daryk]

Orbits are elliptical, more generally.  And solar sails can at least reduce the fuel costs...

[RifleMech]

An orbit is circular around the star, anything placed at the zenith or nadir points without being in an orbit is going to fall due to the star's gravity.  It doesn't just hang there like a lamp.

Aren't jump points supposed to have little to no gravity? Otherwise, how would Jumpships remain in place while their jumpsails are deployed?

[Daryk]

Station keeping drives are for that exact purpose.

[ANS Kamas P81]

Aren't jump points supposed to have little to no gravity? Otherwise, how would Jumpships remain in place while their jumpsails are deployed?

Little gravity - but there's still some there.  Sol's jump zone starts around 10 AU out IIRC, and Saturn orbits the sun at 9.5 AU.  So you'd have roughly the sun's pull on Saturn to cancel out.  Like Daryk says, that's why ships have station-keeping drives, which are there to thrust away from the sun and stay in the jump zone.

[Daryk]

Also don't forget that even "Station Keeping" drives are MASSIVELY more useful than anything we have in the real world.  Being able to sustain a tenth of a G indefinitely is a HUGE thing.

[Lagrange]

Little gravity - but there's still some there.  Sol's jump zone starts around 10 AU out IIRC, and Saturn orbits the sun at 9.5 AU.  So you'd have roughly the sun's pull on Saturn to cancel out.  Like Daryk says, that's why ships have station-keeping drives, which are there to thrust away from the sun and stay in the jump zone.

It's not quite clear to me whether you understand that satellites have their own weak but very efficient drive.  TO page 246 says they have a thrust 0.1 (i.e. 1/20th g).  TO page 247 gives them a strategic fuel use.  TO page 248 specifically talks about how satellites burn fuel to stay on station at the Zenith.  In fact, since the sun's gravity is 6e-4 at 1AU satellites can hold station much closer to the sun.  They can even do a zenith<->earth transport in about 41 days---time dilation is about x4.5 compared to 1g.

[idea weenie]

Little gravity - but there's still some there.  Sol's jump zone starts around 10 AU out IIRC, and Saturn orbits the sun at 9.5 AU.  So you'd have roughly the sun's pull on Saturn to cancel out.  Like Daryk says, that's why ships have station-keeping drives, which are there to thrust away from the sun and stay in the jump zone.

At 10 AU from Sol, the Sun's gravity is only 6.5 * 10^-6 Gs.
The current value for station keeping thrust is 1*10^-1 Gs, or about fifteen thousand times higher than the sun's gravity at the Z/N points.

Let's run some numbers.  We have acceleration, I'm going to assume 180 hours, how far will a vessel at a Jump Point drift during that time if it wasn't using Station-Keeping Thrust.
D = .5 * A * t^2
A = 6.5 * 10^-6 Gs = 0.000063765 m/s^2
t = 180 hrs = 10,800 minutes = 648,000 seconds

D = .5 * 0.000063765 m/s^2 * (648,000 seconds)^2
D = 0.0000318825 m/s^2 * (648)^2 * (1,000)^2 * (seconds)^2
D = 0.0000318825 m * (648)^2 * (1,000)^2
D = 0.0318825 m * (648)^2 * (1,000)
D = 0.0318825 * (648)^2 * (1,000) meters
D = 13387.58928 * (1,000) meters
D = 13387.58928 kilometers

So a vessel will fall about 13,500 km if it leaves its station-keeping drive off.  That is 750 Space hexes, but how does it measure strategically?

1 light-second is about 300,000 kilometers, so over a week the vessel will 'fall' .045 light-seconds, or 4.5% of a light-second.  Even if I assume the gravity quadruples then that only changes the craft to falling 18% of a light-second.

Since 10 AU is 80 light-minutes, that fraction of a light-second is not a significant worry.

So Station-Keeping thrust is not needed for a Jumpship to remain near a Jump point, just thrust within the limit and back out again.

[ANS Kamas P81]

So Station-Keeping thrust is not needed for a Jumpship to remain near a Jump point, just thrust within the limit and back out again.

Just like the ISS using a bit of thrust for a few minutes a month off the station's ion engine to keep its orbit from decaying.  Don't need full thrust, just a spurt or two now and then.

[theagent]

So, question:  do the Small & Large Naval Comm-Scanner Suites (NCCS) increase the "15 AU" limit for detection the emergence wave of a JumpShip/Warship?  And if so, since they require crewmen (6 for the Small NCSS, 12 for the large NCSS) does that mean they're limited to manned vessels (including Space Stations), & if not are the Aerospace Smart Robotic Control System/ASRCS & Shielded Aerospace Smart Robotic Control System/S-ASRCS (Liberation of Terra, pp. 154-157) the only options, or can additional Comm Equipment tonnage be used to replace the needed crewmen?  ASRCS gives a Satellite a P6/G5 skill for 5% mass; S-ASRCS also gives that, but increasing to 6% lets it have P5/G4, 8% lets it have P4/G3, & it's considered to be have a Guardian ECM for the ECM rules in Strategic Ops p. 110, which prevents a Large Craft ECM field from disabling it (unlike the ASRCS).

The reason I ask is that ASRCS/S-ASRCS-equipped units still only have a crew of 0, but can still use any Weapon, Communication, or Sensor system that would otherwise require crew.  Granted, the Large NCSS is too big to fit on a satellite, but with a lower fuel supply you can squeeze the Small NCSS into a 200 to 300 ton satellite easily.

[Lagrange]

I believe it does---there's some errata wording about generalized increases in range.   It sounds like you need ASRCS/S-ASRCS though. 

I'd recommend against it generally though, because it's cheaper and generally more effective to just deploy extra satellites 15 AU away in almost all circumstances.  The only alternative I can think of is if you are hard-limited on mass for some reason.

[Daryk]

Yeah... NCSSs are EXPENSIVE!