Hey all!

Today’s topic will further explore the subjects of fleet movement, FTL-travel and the general wonders one might happen upon when ripping holes through subspace. As the writing of this is a bit sudden the dev diary came out late today, our apologies!
The galaxy is a pretty huge place and to get anywhere in a timely manner you’ll want to travel faster than the speed of light, or use FTL-travel for short. Stellaris will have three methods of FTL that players can use; Warp, Hyperlanes and Wormholes. They all have distinct advantages and disadvantages when it comes to the strategic movement of ships and fleets causing expansion paths, diplomacy and wars to be quite different depending on the method used.

Warp
Warp requires each ship in the fleet to be equipped with a Warp Drive. These are quite costly to build and cause a major drain on each ship’s available power, but allows unconstrained travel to any system within range. When travelling to a system outside the range of a single warp-jump, the fleet has to make a sequence of jumps through a number of systems. Any jump puts a considerable strain on a ship’s Warp Drive, causing the fleet to not be able to jump again for a short while after arrival. While this can be reduced by more advanced technology, it does remain a weak point throughout the game for any species using this method.
Fleets using Warp Drives to travel will need to do so at the edge of a system to lessen the gravitational pull of the local star. This in combination with the fact that warp-jumps have the slowest FTL-speed of the three methods means that the arrival point of an incoming warp-fleet can be identified, and possibly ambushed. The cost of freedom is potentially high!

Wormhole
Some species have decided to sidestep this whole business of blasting through the void at ludicrous speed. They prefer to open up a temporary wormhole that a fleet may use to instantly travel to a distant system. These wormholes can only be generated by a Wormhole Station, a type of space station that can only be constructed on the outer edge of a system. Any fleet wanting to travel will have to use the Wormhole Station as a connecting point, passing through it whenever they leave the system. The station may only generate a single wormhole at a time, forcing all ships and fleets to wait while one is being prepared. The larger the fleet, the longer it takes for the Wormhole Station to be ready. The wormhole generated does allow two-way travel, but will collapse almost instantly after sending a fleet through.
Constructing and maintaining an efficient network of Wormhole Stations is vital to any species using wormholes, as it will allow sending huge fleets from one part of the galaxy to another in very short time. It also allows striking deep inside enemy territory with little warning. This great strength can also be a great weakness, as fleets are left with no means of further offense or retreat should the network be disabled through covert attacks by enemy strike-fleets.

Hyperdrive
The galaxy in Stellaris has a hidden network of hyperlanes connecting the systems, only visible for those who know where to look. Ships that are equipped with a Hyperdrive can access these lanes and use them to traverse the galaxy at incredible speed. They are however bound by the preexisting network, and has to path through each system connecting their current location and target. Galactic voids lacking systems are in effect huge movement-blockers for any species using hyperlanes, having few systems allowing possible crossings. An enemy could potentially fortify these vital systems should they become aware of their existence, creating strategic choke-points. As the hyperlanes exist in subspace, fleets may access them from anywhere within a system and does not have to travel from the gravitational edge as Warp Drives and Wormhole Stations do. As such, catching a fleet using hyperlanes can be tricky. Correctly identifying the paths to intercept and interrupt their somewhat long charge-up is probably your best bet.

All methods of FTL-travel can be improved by researching more advanced technologies. While their exact effects differ some they all improve the speed, range, efficiency or cooldown of FTL-travel. However, being able to casually bend time and space with increased power does not necessarily mean using it with more responsibility. As additional species bend the laws of physics to send larger and larger fleets through the galaxy, there is always the risk of something, or someone, noticing...

Next week we’ll talk more about the different species in the galaxy. Look forward to it!

 

[Starfury]

This is a really old post, but I'm having fun reading back to old Dev Diaries and the reactions as sort of a historical overview of how Stellaris evolved.

Now, this question, just in general, is relevant not just to Stellaris. Hypothetically speaking, absolutely there could be a way to do it without FTL travel. The light sail. As long as you can get up to 10 - 20% the speed of light with a constant 1 - 2 Gs of acceleration, A ship could get to neighboring stars in a few decades. It wouldn't be completely "impractical" to a civilization like our current one in real life any more than the horse and buggy was to the American pioneers in 1820. Obviously, to a space-faring empire it would be.

Furthermore, to a spacefaring empire, they probably wouldn't have any real need to install a lightsail on their ships. And if they did being along such equipment as a very last resort "just in case" need to do so (kind of like bringing along a spare tire), the ships would probably be so massive that it would take significantly longer with a really low rate of acceleration if they didn't continue to improve upon the light sail technological idea.

There's also a huge difference between "getting somewhere" and "arriving somewhere". That difference being the ability to stop.

 

[CBR JGWRR]

Solar sails are best deployed deep in system; Mercury to Mars is a comfortable operating range for them. Much further out and the light pressure becomes rather less. To compensate for that you use things like microwave beaming or laser beaming, where you can apply gigawatt to terawatt energy levels to obtain useful accelerations for ships.

The transmitter has to be really freaking massive for interstellar launches to retain focus at extreme range - especially if the sail is detached to decelerate using the same beam via reflection against the ship. But on Stellaris tech none of this is particularly bad. Using such a big area will probably be good for deceleration against the destination star, but can be boosted by using deceleration rockets.

Light sail propulsion increases with surface area; therefore, if you increase mass by 3, solar sail area has to increase by 9 to retain the same acceleration.

Based on my research and development for Life2.0 - A Broken Shackles Narrative, I'd put an interstellar ship as a 400m pusher-plate capable of 1g transfer across a star system in a few weeks, which means at least a hundred kilotons of mass up to several megatons of mass based on ships designed using Children of a Dead Earth. You could go bigger still, but already at this point the pulse units mass 40 tons each and start to become a significant logistics and power management challenge (you end up needing multi-gigawatt onboard reactor outputs to accelerate pulse units to detonation distance quickly enough)

Using antimatter-matter devices instead of thermonuclear devices drops that mass to starting from 36 tons depending on how much mass you need to confine a few kilograms of antimatter; the vast majority of the mass goes on the X-ray absorbing material that allows turning more energy released into heat and therefore propellant expansion and therefore velocity impulse. You could skip the absorbant, but the efficiency drops massively and the radiation hazard is extreme. (We're using 30MT thermonuclear devices here)

I can't remember off-hand how much force per GW per square metre you get using laser beaming and thermal limits of the proposed materials, but I'd fully expect tens of square kilometres to get acceptable acceleration for the proposed emergency getting home light sail.

The upside of using the sail is it is cheap in terms of materials as you could make a get you home sail with a few carbonaceous asteroids of decent size, and bodging a replacement FTL drive is probably anything but cheap, and for narrative purposes easily justified as not an option, and hence why they have to take the long way home.

 

[RisKFactoR]

IIRC solar sails are supposed to be incredibly thin ( 1 or 2 atom thin) and very wide, so their weight is limited. The best way to the se them is to have a laser shooting at them to increase the efficiency of the radiation pressure

Oh, hell, they could just simply use some kind of 3D printer and have different sorts of compounds and molecules sitting in crates and barrels in storage that it could draw from for building various different tools, parts, components....a solar sail, even! Star Trek has replicators. I wouldn't want to copy-cat Star Trek too closely, and 3D printers are a real and proven technology. People are even making actual real guns from 3D printers now!

 

[RisKFactoR]

Solar sails are best deployed deep in system; Mercury to Mars is a comfortable operating range for them. Much further out and the light pressure becomes rather less. To compensate for that you use things like microwave beaming or laser beaming, where you can apply gigawatt to terawatt energy levels to obtain useful accelerations for ships.

The transmitter has to be really freaking massive for interstellar launches to retain focus at extreme range - especially if the sail is detached to decelerate using the same beam via reflection against the ship. But on Stellaris tech none of this is particularly bad. Using such a big area will probably be good for deceleration against the destination star, but can be boosted by using deceleration rockets.

Light sail propulsion increases with surface area; therefore, if you increase mass by 3, solar sail area has to increase by 9 to retain the same acceleration.

Based on my research and development for Life2.0 - A Broken Shackles Narrative, I'd put an interstellar ship as a 400m pusher-plate capable of 1g transfer across a star system in a few weeks, which means at least a hundred kilotons of mass up to several megatons of mass based on ships designed using Children of a Dead Earth. You could go bigger still, but already at this point the pulse units mass 40 tons each and start to become a significant logistics and power management challenge (you end up needing multi-gigawatt onboard reactor outputs to accelerate pulse units to detonation distance quickly enough)

Using antimatter-matter devices instead of thermonuclear devices drops that mass to starting from 36 tons depending on how much mass you need to confine a few kilograms of antimatter; the vast majority of the mass goes on the X-ray absorbing material that allows turning more energy released into heat and therefore propellant expansion and therefore velocity impulse. You could skip the absorbant, but the efficiency drops massively and the radiation hazard is extreme. (We're using 30MT thermonuclear devices here)

I can't remember off-hand how much force per GW per square metre you get using laser beaming and thermal limits of the proposed materials, but I'd fully expect tens of square kilometres to get acceptable acceleration for the proposed emergency getting home light sail.

The upside of using the sail is it is cheap in terms of materials as you could make a get you home sail with a few carbonaceous asteroids of decent size, and bodging a replacement FTL drive is probably anything but cheap, and for narrative purposes easily justified as not an option, and hence why they have to take the long way home.

Thanks for this reply! I was afraid that it would have to scale up the size of the sail quadratically, the larger the ship.

For narrative purposes, I would also add a ship class not in Stellaris, but I imagine would be:

Logistics vessels.

I imagine large military-grade logistics vessels just sitting around in random space docks around an empire, kind of like moveable warehouses and repair facilities. Such vessels would be extremely vulnerable to attack, so you don't want to expose them too much. And when you do bring them out, you would want to reduce the risks of exposure to hostile fleets or ships. Would be a particularly juicy target for space pirates.

So, if a military vessel has a broken drive, and they cannot easily repair it by themselves, they could send a message out to the admiralty. An SOS of sorts. And have a way to start making their way towards a relatively safe harbor in some out-of-the-way system nearby to meet up with the closest rescue logistics vessel that would need to leave its dock. Perhaps escorted with a few armed vessels itself, and maybe a scout ship to lead the way before they make each jump into each border system.

There's also a huge difference between "getting somewhere" and "arriving somewhere". That difference being the ability to stop.

Well, of course. It's just a matter of flipping the sail in the opposite direction for deceleration at about the midpoint of the journey. Or well past the midpoint, as CBR mentioned just above (after your response), the vessel in question would have retrorockets. That goes without saying, since such a thing would automatically be installed on all space vessels. They have to be. It would be damn near impossible to do space without them. In the case of failed retrorockets, then the solar sail would need to be turned in the opposing direction at the midpoint of the planned journey. (If the retro rockets are not busted, then would be able to sail much further along with the solar sail and gain a lot more ground before thinking about deceleration.)

ETA:

That's another excellent point I just thought of!

What if it's the retrorocket system that fails, and NOT the FTL drive? A solar sail could be used to assist in using gravitational drag to decelerrate a run-away vessel! That would be a really neat scenario!

 

[MrFreake_PDX]

This is a really old post, but I'm having fun reading back to old Dev Diaries and the reactions as sort of a historical overview of how Stellaris evolved.

Now, this question, just in general, is relevant not just to Stellaris. Hypothetically speaking, absolutely there could be a way to do it without FTL travel. The light sail. As long as you can get up to 10 - 20% the speed of light with a constant 1 - 2 Gs of acceleration, A ship could get to neighboring stars in a few decades. It wouldn't be completely "impractical" to a civilization like our current one in real life any more than the horse and buggy was to the American pioneers in 1820. Obviously, to a space-faring empire it would be.

Furthermore, to a spacefaring empire, they probably wouldn't have any real need to install a lightsail on their ships. And if they did being along such equipment as a very last resort "just in case" need to do so (kind of like bringing along a spare tire), the ships would probably be so massive that it would take significantly longer with a really low rate of acceleration if they didn't continue to improve upon the light sail technological idea.

Please do not necro old posts. If any post is >6 months old, you are encouraged to make a new thread.

Thank you.