Planetary Engines

I have been contemplating the use of engines on planets. We know that engines will be able to be built on asteroids, in fact, this is one of the driving premises of the game. I would like to see what the rest of the Planetary Annihilation community thinks about using engines on planets themselves. I believe that if engines can be built on asteroids, why not on planets? Sure, the engines will have a much diminished effect, but the ability to move planets would be awesome.

-Engines could be used to move your planet out of the way of an asteroid
-Engines could be built on an opponent's planet to send them into the sun/asteroid field/moon
-You could move the fight closer to your enemy's planet, bringing your planet alongside his and assaulting from closer range.
-You could partially impact a heavily industrialized area on an opponent's planet with a relatively undeveloped side of your planet.
-Move your planet into a better strategic location, ie out of artillery range or next to potential KEWs.

Feel free to post additional ideas or disagreements, and to answer the poll. thanks

Well, a large asteroid is 1 km in diameter, that's a volume of ~523 598 775.60. The smallest dwarf planet on the wikipedia "Planets" page is 0.08*6371 km in radius, that's a volume of ~554 601 941 425 025 894.68.
That's a factor ~1 059 211 686.32. I think you'll need a lot of engines to move a planet.

I feel like having the ability to smash asteroids into planets is already devastating, in a good way. I mean having your whole base at risk of complete annihilation is a worry, the asteroid is a game changer.

If planets had engines I don't think anywhere would feel safe, it wouldn't really have the element of interplanetary battle anymore it would just be a game were big entities smash into each other.

I'm not trying to be realistic. I realize that in real life this would be nearly impossible. That's what a game is for, isn't it?

I would worry more about asteroids than planets, as planets would be more expensive to move and also move slower.

I'm thinking, unless there's a super fuel that can kick out billions upon billions of force without breaking the engine or the planet's surface... that "moving" planets is VERY unlikely, scientifically speaking.

I'm not sure that anything would be gained, gameplay/depth wise by being able to move planets.

Moons maybe... but planets?
Can we add moons to the Poll?

i changed the poll

Well, if it had a significant gameplay effect, you could secretly stick a few engines on a planet to destabilize it's orbit and force it to crash into the sun. If the other player is on this planet, this strategy would be beneficial

Of course, this also might be a good reason not to be able to move planets with engines...

Moons are not separate entities in this game. They are simply smaller planets. To allow engines to modify one would allow it to modify another.

This idea is not something I anticipate being implemented in the base game. Modding on the other hand... that would be kind of a silly fun mod I think.

True, but it really comes down to how you scale it. You could certainly build an engine on a planet, but if the mass of the planet means it's going to be 24 hours before it even changes orbit significantly, then it would be the equivalent of not doing anything at all. Thus, you can limit just how powerful engines are based on their 'thrust,' and the 'mass' of a planet (I have absolutely no idea what that means in the magical land of code).

A variable, if the system is modelled how you might expect. If I was doing it I'd be tempted to make asteroids the only thing that could change path by the user doing something. Planets and moons would have a deterministic orbital path (repeating, following an equation or defined by simple gravity between other planets and moons [if that reliably leads to stable orbits], whatever ).

Um, says who? There's many ways you can have moons act identically to planets except that they can have engines when a planet can't.

But the costs for so many engines would be totaly crazy, dont expect more than 2 planets with engines in 1 game.

You can never feel safe in PA

To be honest, I don't see any reason why there should be a restriction on where you can build engines. It feels like a much more natural and emergent feature to be able to build them anywhere, rather than arbitrary limitations.

I would simply expect that the effect of them would be much lower on larger bodies. Firing engines on an asteroid? No problem, off it goes, whizzing around the system. On a moon? Fine, but you will need a lot of them to produce any useful change. You can build your engines on a planet, but don't expect them to be alter it's orbit by any appreciable amount. I would suggest that the amount of engines required to hurl a planet out of it's orbit in any reasonable time frame would be far beyond what a player could normally hope to build. Not impossible perhaps, but very, very unlikly.

Although I think it would be an interesting mechanic if plenty of foresight, and a lot of engines allowed a player to alter a planet's orbit just enough to dodge out of the way of an incoming asteroid.

I won't oppose planet moving if it's the equivalent of the Mavor arty. Basically useless in a real game.

You also have to consider the rotational period of a planet/moon when thinking about this. We are already fairly certain that there will be a day/night cycle, so the planet must be rotating around an axis. If you built engines in one spot on the equator for instance, then they would only be able to generate delta-v during half of a day or less.

For a moon, it could be tidally locked (like the earth's moon) which means the delta-v produced by engines placed along the tangent of its orbit with its parent planet could potentially break the moon out of its orbit and send it into orbit of the system's star.

With asteroids, it seems much more reasonable to be able to arrest the rotation and direct your delta-v where you want. It does not seem as reasonable with a planet or moon. In order for you to succeed in stopping the rotational period of a planet or moon you would need to be able to build engines facing sideways. Can you imagine a giant wall of burning flame in an attempt to stop the rotation of a planet?! Anything in the way would be vaporized!

I'm totally game for this idea if someone can find a way to make it work, and keep it balanced. One could probably think of the mobile planet as maybe some kind of super game ender (very late game). If this is "Planetary Annihilation" the least we could do is let the planets fight back .Plus this is the closest I'll ever get to making a Death Star, so there's no way I could say no to this idea.
Maybe have some way to upgrade the engines, or even make a tech 2 engine or something? As long as the "Death Star" planets weren't so effective that some player could place their commander on one of these planets and zip around the galaxy destroying things with impunity (maybe a job for a huge planetary defense cannon?) or for it to travel too fast for something to destroy the commander. The last thing I want is for some jerk to build engines on a planet and spend an entire match running, thereby just being a pain. All constructive criticism welcome.

Just asteroids. Moving planets is near impossible, same for moons. I think Scott Manley did a video about it. You need more engines than planet.

I don't see any reason to artifically restrict anything. While physically it's just not possible, from gameplay perspective it will be so expensive to move a planet, that nobody will ever use it in a serious game. But as a non-serious dumb fun - why not? Only restriction i can think about is engine and hardware limitations, but even then - if you can afford destroying planet with an asteroid, you can probably afford destroying planet with a planet.

realistically though if your engines are pushing the orbit of something with an atmosphere you're not going to get anywhere - that force is just going to return as wind.

if the engines were somehow mounted outside the atmosphere maybe

Not quite. Rocket engines don't work because they are pushing off of something, they work because of the "equal and opposite" reaction of shooting high energy gasses and vapor out one side.

Yes wind would be generated, but I doubt the same amount of energy would then be transferred back into the planetary surface by drag. There would likely just be a gradual heating of the atmosphere from the gasses expelled and the friction between air molecules.