After reading the material in RT, I'm a bit confused. It states that in order to jump safely into the Warp, a vessel needs to be a certain distance out of the core of the system. This would seem to indicate that any point outside of a set distance would be OK. It later notes that pirates lurk at the jump points, seeming to indicate that there are only certain points at the set distance that are acceptable for transitioning to the Warp. So which is it? Can a vessel safely jump from any point beyond a certain distance from the system's star, or only at certain points (like BattleTech's zenith and nadir points - even though other points were sometimes possible)?

A;so, the times for transit from a planet in-system to the jump point seems very long - a few weeks each way - compared to transit times shown in the novels. Should it be a few days instead?

I'd assume there are a few "points" where the warp currents are weakest, so jumping will be easiest there. Pirates will likely lurk near the points nearest to the most populous planet.

Technically you can make a warp jump from pretty much anywhere, it's just that some points are more hazardous than others. What the book is referring to are safer points where the Warp is more stable. Such areas will generally be marked on starcharts etc. and therefore be more likely to be hounded by pirates.

For in system travel, most of that is because of inertia. You frequently exit the Immaterium with a random facing at a variable velocity. You need to maneuvere (in three dimentions) into to the correct ecliptic and direction before accelerating (or decelerating) to your optimal velocity before firing your retro's (and venting excess plasma) as you head towards your destination. All of this can take considerable time, which is only partlially related (as you navigate gravity wells) to your vessel's performance in-theatre (combat). If your Navigator and Helsmen are very skilled and lucky and the warp passage was very smooth you might be able to cut this time considerably, provided your Enginarium (with all its vectoring thrusters) is in tip-top shape, if it's worth the effort.

For travel times, also bear in mind that sub-light travel is very slow indeed; real-life mission to Mars is on the order of three years with our technology and in some ways that's superior to the fantasy stuff in WH40K. A few weeks or even a couple of months is not actually long at all if you're steaming in from the edge of a star system.

The argument comes from the idea that planetary gravity has a detrimental effect on the warp and so you need to be far out from the system to safely jump. Jumping too close to a planet apparently causes massive warp storms and destroys a lot of infrastructure (let alone killing the people on the planet).

So when pirates lurk at jump points/zones I assume it means they lurk at the minimum safe distance from a system where ships jump. That does leave a rather large circumference to lurk around so either they have good scanners, lots of ships, or the stable warp tunnel (below) is used most often.

There is also precedent for stable warp passages, areas analogous to currents where the warp is generally permanently calm. i would assume pirates hang out around them as well. It reduces the area that they would have to scan to find a ship.

Of course this ignores the fact that a sensible captain would fly perpendicular to the solar disc as (as far as we know) planetary systems form in more or less the same plane, so gravitational affects would be proportionaly less 'above' or 'below' the plane than within it..

Hellebore

Hellebore said:

That depends on exactly what gravitational effect is the problem. If it is the local gravity gradient* then it wouldn't matter which direction they go as the stars gravity will overpower the gravity from any other stellar object, unless they are close to one.

Then there is the issue of sublight navigation. If you want to make use of the gravity of stellar objects, you would probably want to be on the same plane as the solar disc at all times so the planets will send you in the right direction. But if your ship is capable of keeping the thrusters firing constantly** then it probably won't matter either way.

*Basically the difference between the gravity experienced by one point to the gravity experienced by the point next to it. I may be using the wrong terms.

**In the core rulebook there are ships that have a max accecleration figure (transports and the Hazeroth raider) and ships that have a max sustainable acceleration (the rest). My interpretation is that the former can only safely manage short bursts from their drive, while the later can keep up that thrust until they run out of fuel.

Gaidheal , which items of modern technology are superior to parts of 40k starships ?

The gravity thing has always been murky. A ship in orbit around a planet is pulled on more by the planet than the star in the system (well, unless that planet is REALLY close to the star). If you were out near Pluto it would have a greater graviational affect than the star. Gravity is one of the weaker forces. According to Carl Sagan the gravity of a person in the room with you exerts more influence on you than Mars does. If you flew directly 'up' from a planet you would escape any noticeable gravity pretty fast.

So I'm not sure what it's really referring to. If the planets were all in alignment along the plane then the most gravity would be along that direct line. The gravity on the opposite side of the sun would be pretty minimal.

Hellebore

Hellebore said:

You will also note that, even in a planetary alignment, the planets still orbit the star. They do not start to orbit each other. So the gravity from the star is still stronger against those planets than the gravity from the other planets. Replace any one planet with a ship and not much will change, the gravity from the star will still be the main contributor to the gravity at that point. The difference between the gravity felt there, and the gravity felt on the opposite side of the star at the same distance will be very small. If your thinking it will be fractions of a percent, your probably overestimating it, but I'll have to do the math to be sure.

The only time there would be a significant difference is if you get close to one of the planets. As gravity diminishes with the inverse square law, the gravity effect from the planet diminishes a lot faster than the effect from the star.

I'm surprised that a physical force such as gravity has such a big impact on the psychic dimension of the immaterium. Perhaps a greater determining factor on where it's safe to enter the warp is distance from inhabited planets,after all a hiveworld of 50 billion souls (inluding thousands of latent psykers) would have quite a large local presence in the warp perhaps creating it's own "micro-climate" of winds,pools and eddies in the warp around it.

As far as I know it was a concept borrowed from other scifi around at the time, notably the Traveller universe and in that universe it's specifically to do with the interaction of the gravitational fields of the various bodies in a system. I don't think the details have ever been spelt out in 40K fluff, though I could easily be wrong if it's in one of the novels or something.

Bilateral - are you serious? A quick list of items that are definitely so, from the top of my head (and I'll temporarily set aside the fact that a lot of 40K tech is 'handwavium magic' stuff) - computers, 40K simple computers are pathetic by comparison, torpedoes, 1940 era torpedoes are about equivalent in terms of technical sophistication, "solid projectile" firearms, 40K versions of these are apparently about as reliable and accurate as 18th or 19th C firearms, though they do have 'modern' feed mechanisms. 40K is deliberately lacking in some areas of technology to play up the "grim, dark" and "mediaeval in space" themes and it has always been so, with the background explicitly saying that in the distant past things were much, much more sophisticated than both our technology and theirs.

I've seen a couple of ideas concerning the matter of jump points/zones in Black Library novels.

I've actually heard it suggested that the gravity issue is the other way around, actually - it's not gravity that has a detrimental effect on the Warp (after all, near to an inhabited world, the veil between reality and the Warp would be thinner by merit of the presence of sapient creatures, psykers, etc), but rather the Warp that has a detrimental effect upon Gravity.

The concept of 'probability wakes' was, IIRC, presented in Bill King's Farseer , as a consequence of (and means of tracking) vessels entering and leaving the Warp. Essentially, the idea is that the energy of the Warp leaks out past a vessel as it translates, creating a swiftly-dispersing 'wave' which distorts natural law. Far from a planet, it's inconsequential... the wave disperses before it can influence anything. Too close to a world, though, and the ripple starts causing havoc as time and space convulses in all sorts of unpredictable ways.

The other suggestion, I read quite recently. The novel Rynn's World , by Steve Parker, describes the invasion of the Crimson Fists homeworld by WAAAGH! Snagrod, and the space battle portion of the book alludes to the concept of jump points. The way it's presented, there's nothing physically impossible about translating into or out of the Warp near to a planetary body. The reason people don't do that, generally speaking, is that it's dangerous - leaving the Warp near to a planet can cause catastrophic damage to a ship. I'd imagine that it's a matter of sudden change - a ship goes from being free from any and all external sources of gravity, to suddenly being subject to the gravitational pull of a planet in an instant, and the resultant stress that causes the ship can be significant. Translating into the Warp would be similarly awkward - you're going from being subject to the pull of a world's gravity, to being free from it, and the sudden release is equivalent to letting go of an elastic band that's been stretched.

I think that such a physical and personal consequence would be more than enough to dissuade most people from entering or leaving the Warp too close to a planet... though Orks apparently don't care.

Another thing to consider on the idea of Jump Points or Zones is the idea of charted and mapped routs. We know from a verity of sources that the warp has currents and that traveling though the warp is heavily dependent on these currents. Therefor, when charting a rout, it's these currents that are being mapped, where to find them, and where they'll take you. Stable warp routs are those currents that don't change much where as unstable routs are those where the current changes course or vanishes. So, if there's a definite current that one would need to use to get from point A to point B as laid out in the maps and charters aboard the vessel, then there's probably a certain place the vessel must go to in order to catch the current as well as a place where vessels leave the current to into real space closest to the system in question. these on/off ramps to the warp current would be the jump points or jump zones.

By the sounds of it you use both Jump Points and Jump Zones, just in different ways.

The jump zone is when you're far away enough from a planet/system to safely make a warp jump. There's been several different reasons presented, gravity and space-dust being the two things commonly avoided. whatever the reason, you want to fly away from the star for at least two weeks before jumping.

A jump point would be somewhere a stable area of warp overlaps a jump zone, maybe a warp passage or just a calm region to get one's bearings in.

Why does this forum keep eating my posts ?

Bilateralrope said:

Sometimes, if the quote tags aren't set up properly, the forum will simply refuse to post the message. Going back in your browser and correcting the problem tends to help, in my experience.