A couple of questions regarding Grav Decks.

[R.Tempest]

Doing that would inhibit the use of the ship's drive. Spinning along the thrust axis presents a gyroscopic complication while under thrust, but isn't impossible.

This would be why the rotation has to be stopped before jumping I would think.

[BirdofPrey]

Doing that would inhibit the use of the ship's drive. Spinning along the thrust axis presents a gyroscopic complication while under thrust, but isn't impossible. On the other hand, spinning end over end means the drive is pointing the wrong way for half of the ship's rotation.

Yes, but if you're under thrust, you don't need the grav deck.

[cray]

Yes, but if you're under thrust, you don't need the grav deck.

Stationkeeping at standard jump points is a perfect time for applying both thrust and spin.

This would be why the rotation has to be stopped before jumping I would think.

Is rotation stopped before jumping? Ships can even be moving when they jump.

[Robroy]

Wouldn't you also be spinning the sail if your spinning the hole ship. Wouldn't that be problematic given how fragile they are?

[cray]

Wouldn't you also be spinning the sail if your spinning the hole ship. Wouldn't that be problematic given how fragile they are?

Oops, good point. De-spinning the sail would be quite a mechanical complication for the design.

[Daryk]

*snip*
Is rotation stopped before jumping? Ships can even be moving when they jump.

Ships are by definition moving when they jump, right?

I think it would be easy enough to mount the sail rigging to not spin with the rest of the ship.  Certainly no harder than installing a 50 ton grav deck...

[Robroy]

There are detachable sails.

Or is that just for war ships?

[Weirdo]

Oops, good point. De-spinning the sail would be quite a mechanical complication for the design.

I imagine complications like this are why even stations appear to have internal(or mostly internal) grav decks as opposed to simply rotating large parts(or even the majority) of the station. :)

[R.Tempest]

 Would the sail spinning make that much of a difference? I can see it might be tricky to deploy or fold, but once its out the spin shouldn't make a big difference in its ability to absorb energy. There would be stress at the connecting points for the shrouds, but it's not like there aren't other wonder materials in use.

[Daryk]

Sails have a huge diameter, so the stresses at the rim would be pretty high if you're spinning the ship fast enough for comfortable gravity at the comparably miniscule radius of the hull.

[Von Jankmon]

Oops, good point. De-spinning the sail would be quite a mechanical complication for the design.

Actually a very gentle spin would be a good way to unfurl a sail, then you only need to tension the draw wires to furl the sail not to deploy it to begin with.  As canon sails are depicted with tension cables but not booms this is a plausible explanation as to how sails are unfurled to begin with.

This spin would be very gentle to deploy the sail at the correct speed, so the sail itself might be deployed from a ring  which is spun slowly to fling weighted end sections and draw out the sail, the connecting booms we do see guide the sail with guide wires, they also help with furling the sail, but as the sail extends far beyond them they are not functional as a mast for the sail itself.

[idea weenie]

There are detachable sails.

Or is that just for war ships?

I'd see that being a method of 'cheating'.  You detach the sail and have a small engine and microwave transmitter on it (and maybe a small battery).  The ship itself has a microwave receiver and a larger battery.  The ship spins, and a microwave receiver array is always kept illuminated by the microwave transmitter from the sail.

Think of it as a strip of receiver array around one section of the ship, like a belt.  If the ship needs to repair part of the microwave receiver array, it transmits to the solar sail to charge its onboard battery instead of transmitting the power.  At the same time, the ship switches over to using the onboard battery to charge the KF core.  The maintenance team goes out to repair, and after they are all back inside, the detached sail is instructed to begin retransmitting power at a slightly higher rate so the sail's onboard battery is drained.  The KF core begins charging again from solar power, and the ship's battery is filled with any excess power.

After the ship jumps, it can start charging the KF core off the internal battery, while the detachable sail is deployed and extended.  The battery is large enough to last until the sail array is transmitting power.

[Daryk]

If the sail is detached, how does it keep station?  ???

[cray]

If the sail is detached, how does it keep station?  ???

Well, let's face it, it's not exactly a rapid, screaming plunge into the star. You only need micro-gravity thrust. If you've got, like, a sail attached to a lithium fusion battery adequate to promptly charge a WarShip's drive, then it won't be hard to strap a small fusion motor on to it so it stays put.

[Robroy]

And if it did drift how far would it go in a week. The jump points can be tens to hundreds of millions of kilometres from the star.

[Daryk]

Which then begs the question as to why JumpShips have station keeping drives at all...

[Weirdo]

I figure the sail just has a beacon, and you let it fall, and then pick it up on the way out. As long as you remember to get it before it falls too far, you've got no problems.

JumpShips need drives because they still need maneuvering ability, such as either staying near the jump limit, or climbing back out to the limit after spending a week falling.

[BirdofPrey]

Oops, good point. De-spinning the sail would be quite a mechanical complication for the design.

Certainly MUCH less complicated than trying to make a workable external grav deck, though.  The sail doesn't have to be sealed and power is easy to transmit through a rotary transformer where a grav deck has to handle holding an atmosphere of pressure in a rotating coupling where many lubricants don't work due to vacuum and extreme temperatures, and has to transfer water and life support gases along with power and data.

Well, let's face it, it's not exactly a rapid, screaming plunge into the star. You only need micro-gravity thrust. If you've got, like, a sail attached to a lithium fusion battery adequate to promptly charge a WarShip's drive, then it won't be hard to strap a small fusion motor on to it so it stays put.

Honestly, that's why I was wondering about just spinning th ship on a counterweight.  Station keeping thrust seems fairly pointless, for a ship that will be moving on after a week or two due to how low acceleration the star would be imparting.  It only makes sense to me for actual stations (and ships trying to keep near it) that will be there long enough for people to have noticed it's moved.

[cray]

And if it did drift how far would it go in a week. The jump points can be tens to hundreds of millions of kilometres from the star.

It depends on the stellar type. The actual gravity at the jump points vary. But for anything K-type or brighter the answer is, "not much."

Which then begs the question as to why JumpShips have station keeping drives at all...

SHH! BattleTech starships have station keeping drives! Don't look too closely at canon, dangit! ;)

[Daryk]

Heh... always a good answer, Cray!  ;D

[Robroy]

It depends on the stellar type. The actual gravity at the jump points vary. But for anything K-type or brighter the answer is, "not much."

SHH! BattleTech starships have station keeping drives! Don't look too closely at canon, dangit! ;)

I was under the impression that the reason the distance varied with the star was to insure the gravity from its mass did not interfere with the drive during jumps. So at the jump points there should be practically no gravity.

[Von Jankmon]

Which then begs the question as to why JumpShips have station keeping drives at all...

SHH! BattleTech starships have station keeping drives! Don't look too closely at canon, dangit! ;)

Actually cray you miss out on opportunities to explain canon. Many of the problems in Battletech, though not all, have a plausible explanation that you can add to canon that explains prior unexplained canon tech.

You need station keeping because you actually need to remain in one spot, or at least to fall at a known rate.  Jump drives are not random, they are very precise, and while most jumps are made at zenith and nadir zones (I cant really call them points) it is a good idea to know where you are so you can jump accurately.

Jumps need to be made towards set target coordinates, these themselves can be very precise and can allow for jumps into pirate points if your star charts are accurate.  But your jump is only as accurate as your fix on your current position. If you can moderate your position relative to absolute point of zenith of nadir, or your pirate legrange point, you can jump accurately.

We can take this further and answer yet unasked questions. 
Normally this doesn't matter too much but it still does.  We must assume that jump zones at even zenith and nadir points are coordinated to minimise chances of misjumps into another vessel.  While this can happen anyway, and is admittedly unlikely because of the vastness of space, its is a viable concern if jumps are as accurate as they are made out to be.  It would be a suicidal thing to do to jump directly onto the absolute zenith or nadir coordinates, in case another incautious jump navigator did the same.  So how do you make sure your jump is to a safe location.  You ship has a registration code right?  It probably has a code for the jump engine too, a unique serial number at at least unique to your factions registry.  Say your ships KF drive is Lyran registered and is given a number of #51023, that or a set factor of that is the number of km you dial in as jump-exit coordinates from absolute zenith/nadir for your jump.  You can randomise the direction for the ship or coordinate them for a convoy so that your jump arrival coordinates can't be intercepted, and remain together, but so long as that unique distance is kept you are guaranteed never to jump into another vessel.  This way you can plot jumps based on a set unique numerical variable that doesn't require prior knowledge of other traffic.

Station keeping then becomes important again to guarantee you never drift off into the path of another jumpship.  While the vastness of space makes KF navigation accidents unlikely they do happen and are horrific when they do, so it would pay for jumpship captains to keep station keeping and obey navigation safety protocols.

[Von Jankmon]

I'm finding an 82 meter diameter isn't all that small.  Even with a strip only 11 meters wide, there appears to be enough room for medical, exercise, messing and berthing with plenty to spare.  2,800 square meters is actually quite roomy, and that's just the highest G deck out at the rim (granted, it's only 0.4G at 3 rpm).  Three more decks remain squarely in the comfort zone, and they're all over 2,000 square meters each, though with slightly less "gravity".

The way I see it the 50 tons for the grav deck is specific allocation for deck components, notably spinning mechanism and the hub.  A lot of the mass is taken up by structure mass as its a not insignificant portion of the volume of the ship.  Also it can account for a portion of the mass allocated to crew quarters.

[cray]

Normally this doesn't matter too much but it still does.  We must assume that jump zones at even zenith and nadir points are coordinated to minimise chances of misjumps into another vessel.

No, you don't need to assume. It's stated in Strategic Operations.

Station keeping then becomes important again to guarantee you never drift off into the path of another jumpship.

Post-arrival maneuvers with stationkeeping drives performed to avoid collisions are also in StratOps.

[Von Jankmon]

No, you don't need to assume. It's stated in Strategic Operations.

Post-arrival maneuvers with stationkeeping drives performed to avoid collisions are also in StratOps.

True, but it is not explained how or why in Strat Ops.

A jumpship can come in from anywhere.  You can move your ship and find yourself in the path of a Capellan frieghter with a cargo of beans.  It doesn't know you are there and you dont know its coming.  A mechanic that keeps ships separate yet allows flexibility of movement would be needed.

[cray]

A jumpship can come in from anywhere.

Yes. And that's why StratOps (p. 131) indicates recharge stations and JumpShips park just inside the proximity limit so a JumpShip can't arrive on them.

  You can move your ship and find yourself in the path of a Capellan frieghter with a cargo of beans.  It doesn't know you are there and you dont know its coming.

Since JumpShips park inside the proximity limit to recharge, an arriving JumpShip can't land on them. Therefore, the only way for JumpShips to collide is for them to move by their stationkeeping engines on a collision course. Sensors like drive plume detectors would give days of warning for collision avoidance.

A mechanic that keeps ships separate yet allows flexibility of movement would be needed.

I'd recommend reading up on the "big sky theory." JumpShips are much less numerous than airplanes, operate in volumes billions of times bigger than the entirety of Earth's atmosphere, and have lines of sight that gives them days of advance warning before a collision.

[Kovax]

I'd recommend reading up on the "big sky theory." JumpShips are much less numerous than airplanes, operate in volumes billions of times bigger than the entirety of Earth's atmosphere, and have lines of sight that gives them days of advance warning before a collision.

...except while jumping into a system.  In that case, there is no line of sight in advance of a possible collision.  Then again, jump "points" are more like line segments with a certain amount of "slop" providing thickness, so you have a cylinder of "usable" space extending out from some distance above and below a star.  It could use a ship registration code or some pre-approved value unique to that vessel to determine the target distance from the axis of that line, as a way of reducing (not absolutely preventing) collisions, but ships moving toward or from stations would regularly cross any chosen point along or extremely close to that axis.

Given the massive areas involved, it wouldn't be a common thing to have one ship jump in too close to another, but a few relatively simple and cheap precautions could reduce the already tiny risk by an order of magnitude or more.

[cray]

...except while jumping into a system.  In that case, there is no line of sight in advance of a possible collision.

Which is why StratOps indicates ships usually move inside the proximity limit upon arrival.

[Von Jankmon]

Which is why StratOps indicates ships usually move inside the proximity limit upon arrival.

They are vulnerable during that transition period.
Yes a jump accident is uncommon, but catastrophic when it happens.

It also takes time for a jumpship to get anywhere adding to recharge times.  Coordinate coding fixes all those problems.