This is a pretty general question.

Why do starships need to take off and fly straight past the incoming ships in order to be able to get away? (I know, film reason = because it's cool)

Eg The rebel transports in Ep V need the ion cannon to "clear a path". Why? Why couldn't they take off, fly around the planet, then break for space in a clear spot. Same for the Naboo cruiser in Ep 1, and blockades in several episodes of the Clone Wars. The planetary blockades only seem to be on one side of the world.

The hyperspace point they want might be along that line, but if they're being chased surely they could just jump to anywhere, then recalculate for their original vector.

I can just see players arguing about this in my near future...

Given the flying carpet aspect of hyperspace travel in general, it's pretty easy to whip up any number of pseudo-science-magical reasons for it. 'Because it's cool' rates as the best imo....

time and fuel could be factors as well, prohibiting an extra jump.

and maybe the blockading ships can fly around the planet quickly enough if they're spaced out well around the planet. after all, some satellites orbit the earth every hour or two, and that's not trying to catch something.

When the Falcon was running from the Star Destroyers in EpIV, this seemed to be more an effort to evade them before making the jump rather than flying past the blockade. In that way, it seemed liked the Falcon only barely escaped.

In Episode I, the Trade Federation Blockade was huge, handled by what seemed to be a large number of ships.

Another reason could be placing ships along the optimum or mapped jump point in and out of the system to enact a blockade.

The planetary blockades only seem to be on one side of the world.

I always assume that's just the ones you see, or that side of the planet is the only direction from which hyperspace travellers can arrive. The movies and TCW also play fast and loose with scale...check out the planetary ring in TCW Season 6:E1, in "reality" it would fade to a thin ribbon and completely disappear from sight before even rounding the planetary horizon. I find it simpler to just assume this scale is "flexible" wrt telling the story or setting up the encounter.

Assuming the Empire doesn't just blanket the planet is Star Destroyers, they must have some method of intercepting a ship moving off planet from any location. What I'm thinking is they must use the same method that Humanity's fleets use in Mass Effect. Essentialy, the Earth's navy came to the conclusion that it would be impossible to place enough ships at each new colony to adequetly defend them, the cost to run and upkeep that many ships wouldn't be pratical. Instead they have a few major fleets constantly on stand-by ready at key Mass Effect relays to respond to any incident quickly.

So what the empire does is assign a fleet to blockade the planet. Said fleet covers the planet in sensors using some kind of sensor ship/buoy system. When a ship is detected leaving the planet then a response force is sent from a centralized location, more than likely some kind of refueling station/docks. So the key to breaking a blockade would be to leave before the response force shows up. This should be difficult, as I imagine not much is quicker then a military grade hyperdrive. Also it opens up more options for blockade running. A competent slicer could find a way to disable one of the sensors, making a hole in the net for the player's ship to pass through. Players could even send up a bunch of decoys hoping to overwhelm the response fleet and slip by while the fleet is busy chasing decoys. Granted you might wanna up the difficulty on these as spoofing military grade sensors would probably be a difficult skill check.

Maybe when a ship is peppering you with shots from Turbolaser batteries you can't jump, it interferes with the Iludium Q-36 Explosive Space Modulator.....

Turbolasers are long range, so that's up to several thousand km, easy enough to pepper a ship in some kind of area effect to monkey with their hyperdrive, so fly straight at one, nail it with an ion cannon, and other SDs will be hesitant to fire for fear of hitting the disabled SD.

I assume when starships are trying to leave the atmosphere, they try to do so in the quickest way possible. This means flying in a straight line right up into the sky. As stated in an earlier post, it might take too much time and fuel to fly around within the atmosphere until you position yourself to exit the atmosphere. I like to think that, while in the vacuum of space, ships that are stationing an orbital blockade are able to move more efficiently around the planet. So if they were to track the flight path of any ship they are trying to prevent from leaving, they could easily relocate and block them.

Remember that Hyperspace doesn't exist at all points in the galaxy. And that gravity puts up interference in Hyperspace.

That means if you are blockading a planet, you don't need to cover all the angles. The planet's star and any other planets and/or nearby celestial bodies will create dead zones where you can't jump.

In addition, Hyperspace may simply not exist in a certain direction. There could literally be only a couple places to make a hyperspace jump in a particular system. So you only need to cover that area. Any ships attempting to make a sub-light break for it could be caught using your superior sub-light engines.

Well, how about the asteroid field that's all over the place (apparently). Perhaps it was the only asteroid-free vector of escape?

On the other hand, you could flee from the other side of the planet. . . where your big freaking gun isnt. You want covering fire, you gotta go thataway!

Pseudo-scientific explanation:

Consider also the drag and friction that atmosphere creates. Ships are limited to a certain speed due to aerodynamic drag. Starships even moreso, since they are not designed primarily for atmospheric flight.

In space, there's no atmosphere and, thus, no drag. Starships with ion drives can, in theory, move much faster in space than any craft could in atmosphere.

Well the blockade at Hoth had at least 12 destroyers according to the Essential guide to Warfare (Executor plus 6 others in Death Squadron and 5 from the local sector fleet) and we don't know how many ships the Tatooine Blockade had but I doubt they sent the entire blockade force after the Falcon,

2 SDs being able to engage targets while 10,000 km apart from one another, I would think 12 would be plenty to box Hoth in nicely.

Why couldn't they take off, fly around the planet, then break for space in a clear spot. Same for the Naboo cruiser in Ep 1, and blockades in several episodes of the Clone Wars. The planetary blockades only seem to be on one side of the world.

Any ship trying to just fly across the surface would be blasted to bits from orbit. Flying straight up reduced the amount of time a ship has while under fire (before it's shields fail) plus it lessens the chance the blockade ship can launch fighters to pursue it.

As to the blockades that don't have 100% coverage, you only need to cover the area over major spaceports. Huge ships will either have to fly under you or through you. There was one episode in TCW where Republic Blockade Runners had to drop supplies from the air because the Separatists were covering all the spaceports (or nearby landing spots). They might have been able to land but it would have been too far away to help.

Pseudo-scientific explanation:

Consider also the drag and friction that atmosphere creates. Ships are limited to a certain speed due to aerodynamic drag. Starships even moreso, since they are not designed primarily for atmospheric flight.

In space, there's no atmosphere and, thus, no drag. Starships with ion drives can, in theory, move much faster in space than any craft could in atmosphere.

Indeed. Actually there was a cool Youtube video on this subject where your speed is directly dependent on the size of your engine, and thus a bigger ship would actually end up being faster than a smaller one(also why space fightercraft aren't practical IRL)

So an ISD, because it can mount a much larger engine, would be faster than many smaller vessels.

The lower inertia of a smaller ship doesn't compensate for having a smaller engine, because the bigger the engine the more excess power it can generate.

Pseudo-scientific explanation:

Consider also the drag and friction that atmosphere creates. Ships are limited to a certain speed due to aerodynamic drag. Starships even moreso, since they are not designed primarily for atmospheric flight.

In space, there's no atmosphere and, thus, no drag. Starships with ion drives can, in theory, move much faster in space than any craft could in atmosphere.

Indeed. Actually there was a cool Youtube video on this subject where your speed is directly dependent on the size of your engine, and thus a bigger ship would actually end up being faster than a smaller one(also why space fightercraft aren't practical IRL)

So an ISD, because it can mount a much larger engine, would be faster than many smaller vessels.

The lower inertia of a smaller ship doesn't compensate for having a smaller engine, because the bigger the engine the more excess power it can generate.

Plus you can have a pub on the bigger one, which is an unparalleled advantage.......

An on-board pub, the only thing standing between the Falcon and being the best ship ever.

Pseudo-scientific explanation:

Consider also the drag and friction that atmosphere creates. Ships are limited to a certain speed due to aerodynamic drag. Starships even moreso, since they are not designed primarily for atmospheric flight.

In space, there's no atmosphere and, thus, no drag. Starships with ion drives can, in theory, move much faster in space than any craft could in atmosphere.

Indeed. Actually there was a cool Youtube video on this subject where your speed is directly dependent on the size of your engine, and thus a bigger ship would actually end up being faster than a smaller one(also why space fightercraft aren't practical IRL)

So an ISD, because it can mount a much larger engine, would be faster than many smaller vessels.

The lower inertia of a smaller ship doesn't compensate for having a smaller engine, because the bigger the engine the more excess power it can generate.

Plus you can have a pub on the bigger one, which is an unparalleled advantage.......

I only regret that I have but one Like to give to this post.

A man should not ask how many likes he can give a post, but how many posts he can give that are liked.

-some random dude on the internet.

I have always thought that most of the time the blockade is the nearest hyperspace jump point. It makes more sense to block near a point, then at an altitude. Also blockading above known space ports would aid in interception. Even the Millennium Falcon was intercepted by the Executor

For hoth, it was made a bit easier because the Ion Cannon could make a hole in the blockade for ships to slip through.

I have always thought that most of the time the blockade is the nearest hyperspace jump point. It makes more sense to block near a point, then at an altitude. Also blockading above known space ports would aid in interception. Even the Millennium Falcon was intercepted by the Executor

For hoth, it was made a bit easier because the Ion Cannon could make a hole in the blockade for ships to slip through.

Taking this and running with it, it's reasonable to assume that a lot of the hyperspace mathematics is pre-calculated. What else could hyperspace maps be? If a lot of it is pre-calculated and it's time-consuming to re-calculate from different points, you have your answer! They have to punch through to the planned point because whilst that's dangerous, the alternative is flying around under fire for even longer as they keep trying to calculate the new parameters on the fly as they move (and potentially are kept moving, producing an endless cycle).

That still leaves room for maneuvering and gamesmanship between the blockaders and the blockadees. If the Imperial Commander sees all the rebels making a break for some spot on the other side of the planet, she may guess that they've calculated a different route. An espionage droid or a traitor might reveal where they're planning to jump from... This way you have the best of both worlds - cunning maneuvering as well as it actually being feasible to blockade a planet.

I have always thought that most of the time the blockade is the nearest hyperspace jump point. It makes more sense to block near a point, then at an altitude. Also blockading above known space ports would aid in interception. Even the Millennium Falcon was intercepted by the Executor

For hoth, it was made a bit easier because the Ion Cannon could make a hole in the blockade for ships to slip through.

Yeah, but that's cos they fly right at it! That's the reason for the thread - why?

Lots of good thoughts here guys. I'm still going to get debated at, but I have some shields now

Because of budget restrains.

In the reworked Special Editions and such more Star Destroyers have been edited in to show that there was no 'open' space around to fly to.

The other listed points are valid too. Time, distance, range of the SDs (and their weapons) ... if the Rebels had wasted more time Echo Base would have fallen even quicker and several freighters would have been downed too. After the Derra IV debacle not an option.

Another thing to keep in mind, is that while the SDs are each set in a different area, the squadrons of TIEs they carry are going to be used to chase down anything that looks like it might break through.

Draw two plus signs mark one north 0 south 180 east 90 and west 270. Then draw another plus this time east west and simply 180,0 and 0, 180. This is to simulate the equator basically then simply state that the blockade was a cube of 6 ships with 3 additional ships in support to plug a hole if a vessel was disabled. The other three ships could of been pursuit vessels if necessary. Based on this geometry up to four vessels would have line of site on a fleeing vessel. Thus the bold move of charging one of the star destroyers. One this would put it potentially in the line of fire and two the vessel most likely to target you would have the smallest silhouette to aim for. This also allowed the fleeing transport a shield to use when it passed the disabled vessel. Now another error in that blockade is the rebels had time to plan evacuation. So basically when the destroyers got into position it would of been in their interest to deploy a fighter screen. However the rebels were able to throw that off by launching the transports. The commanders then had a choice to drop shields and be a sitting duck as it deployed fighters or simply take a battle posture and then deploy when the threat was dealt with. The executor being the flagship would of done the latter further out so it could deploy a fighter screen to protect the ship and be less of a target.

That just my observation though.