In my book series, the various planets of the galaxy, give or take, generally have access to late medieval to early renaissance era technology in terms of warfare. That means full plate armor, siege cannons, crossbows, and longswords for most peoples while the most advanced couple of civilizations have just figued out the arquebus. However, in this universe, every planet has, for millennia, been interacting, trading, and warring with other planets through the use of Startreaders (regular sea boats fitted with special magic crystals that allow for FTL travel, flight into and out of space, complex space navigation, and most importantly, project an energy field around the ship that protects against the vacuum of space and re-entry friction as well as allowing a field of breathable air to surround the boat while it is in space. Any boat can be made into a Startreader through the use of these "Navigation Crystals"). However, the two major limitations of Startreaders are that in order to fly, they need to do so from a moving start, meaning they can only take off from or land in large bodies of water; and they cannot sustain flight in atmospheres for very long, meaning once they take off, they need to go straight to space and cannot be used for air travel.

Since when invading, planets must use essentially space boats to get to enemy territory, how would this change the way wars would normally be fought in the late medieval and early renaissance eras?

  • $\begingroup$ "an energy field around the ship that protects against the vacuum of space" - vacuum of space is just the most obvious issue in space travel. It also needs to solve all life support issues, 0g-issues, and probably high-g-issues. $\endgroup$ – Alexander Mar 25 at 17:30
  • $\begingroup$ Also, do I understand it correctly that "space boats" do not teleport in and out of the sea surface, but rather acting as FTL hydroplanes? $\endgroup$ – Alexander Mar 25 at 17:36
  • $\begingroup$ @Alexander that is correct. $\endgroup$ – The Weasel Sagas Mar 25 at 18:28
  • $\begingroup$ Then (considering @Lupus590's answer) is it possible to launch fast unpiloted projectiles, or it would require a human pilot to set the boat on its course? $\endgroup$ – Alexander Mar 25 at 18:33
  • $\begingroup$ @Alexander it would be, but I imagine these would be extremely difficult (if not impossible) to aim accurately and would be limited in size by what available ship-mounted weapons could fire. $\endgroup$ – The Weasel Sagas Mar 25 at 18:38


If you have access to telescopes, reconnaissance platforms would be invaluable. That might be too much for your technology level, so instead scouts might dip briefly into the atmosphere, buzz your enemies, and yeet back into space without landing (If this is within the capabilities of your ship).

Dropping rocks from space would be a devastating attack, as would straight up crashing spare ships into enemies. If navigation crystals are not prohibitably expensive, someone has probably done this. If you've got parachutes, you've got paratroopers (this may again require the ability to dip briefly into atmosphere without landing).


The biggest effect is the ease of planetary transport. Once you're in orbit, landing anywhere on the planet takes about the same amount of time and energy. If you're a big naval empire, you might leave a pile of troopships in orbit to drop in and reinforce any of your colonies at a moment's notice. You'd also probably focus more on using ocean-faring vessels to defend or attack ports you care about, in order to protect your troopships as they land, or keep enemy reinforcements at bay. If two naval empires were to fight, they would probably focus on holding the important ports with your standard seafaring navy, and if possible holding the space around the planet itself. If a smaller country were to fight a spacefaring one, they might focus on inland targets, or use hit-and-run tactics to flee before reinforcements arrive.

The rest of how strategy and politics would change with spaceships depends a largely on how powerful you are willing to let ship impacts be.

If you go off the physics, hitting a planet you don't like with a chunky startreader at even a sizable fraction of the speed of light would be enough to render large portions of it uninhabitable for a couple dozen years (or maybe even crack the planet..). If you allow this, it gives every person with access to these crystals the equivalent of a nuclear bomb. Your nations would exist in a constant state of mutually assured destruction, and your crystals would be a very tightly controlled resource-- can't let any potential dissidents get a handful or they might nuke the capital from orbit.

If you don't find this state of affairs very interesting, perhaps ships phase out of reality when they're traveling faster than light, and so ship impacts are considerably less dramatic.

Either way, control of the space around your planet is critical for both strategic and mercantile reasons (can't do interstellar trade if your neighbors blockade you or charge ludicrous tariffs). If at all possible, people will be developing space combat systems, even if its just pulling up next to people and shooting them with crossbows.

One final note is that large lakes would become a lot more politically significant. Without startreaders you couldn't really go anywhere with them, but now they give you the same amount of trade access as the actual ocean, plus risk of invasion. Buy waterfront property now!

  • $\begingroup$ "Dropping rocks from space would be a devastating attack" - not really. Rock may produce a fiery meteor which, in one in a million chance, may kill someone down below. Specially engineered rods would have a better effect, but without precise targeting systems, chances may improve to one in a thousand. $\endgroup$ – Alexander Mar 26 at 17:16

There's no such thing as an unarmed spaceship.

Any spaceship with decent mass (about the kiloton mark) and going at a noticeable fraction of the speed of light can become a relativistic kill missile just by crashing at its high speed.

Now being a magically enhanced sea ship, your ships will be lighter than that and thus a little less devastating, but not much since velocity is a more significant factor of kinetic energy. (E = M V^2) Also, it's not too difficult for a person in your world to figure out that faster crashes cause more devastation.

As for new tactical options from having a spacecraft.

Single occupant orbital insertion. One could make a rowboat like craft and put your magic into it and drop specialised troops behind enemy lines.

There's also what is known as rods from god, this is the unarmed spaceship things again but the missile is instead cargo instead of the ship itself. A massive object resistive to reentry effects is dropped or fired from space to devastate a target. A ship could launch one of these by aiming for the planet, then dropping the rod from god, and then changing course so that the ship misses the planet.


There would be no change

By limiting the landing procedure to a large body of water and limiting aerial use there's no technical difference between this and any seaborne assault during the middle ages, with one possible (but minor) difference: the assault could come from a large inland body of water.

However, it would take no time at all for the Powers That Be to realize that their sea tactics must be used near those large inland bodies of water.

Note that you wouldn't have seaborne bombardment (cannonading) because the Startreaders can't stay airborne very long. I suppose they could have some on the way down, but it would be limited to local dive bombing, wouldn't it? If you did, that would be the Startreader version of cannonading.

Ergo... no change.

Which is good for you because you really don't want any differences, do you? Or do you? If you do, then we need to work on the rules governing use of the Startreaders (nice name, BTW).


Take off and Landing:

I think your desire is for these ships to be just transport, and not weapons. If you are fairly careful, you can be sure the ships aren't explicitly used as weapons. I think, however, there are some issues that will radically change warfare.

  • Even a relatively short length of rock-free straight river moving fast will allow launches. Even a moat-like water runway oriented with the wind would allow a sailing ship to catch the wind and at least briefly reach launch speed.
  • Dedicated ships would be built quickly to meet the needs of inland sites. If a ship needs to be moving before launching into space, it will take no time at all for inland sites to build launch facilities. This might consist of a water run with the water channeled from a stream to a specially designed bed where a small dam can be opened up and flush a ship up to launch speed, or even a dry run downhill on wheels or rollers like a ski slope where a vessel is directed upwards at the last second to launch. These ships wouldn't require sails or oars because they wouldn't need their own power to launch. Actual ships would be at a DIS-advantage because it would be harder for them to get up to speeds, whereas dedicated ships launched from specialized facilities will get up to speed faster and don't need to be seaworthy or shaped like boats.
  • Landing doesn't require anything particular to do. Your boats might have wheels on them to be used as carts in the event of a land landing, allowing them to be hauled to the nearest river or launch facility. This same landing ability means that relatively cheap landing ships may be developed, and troops dropped ANYWHERE at will, with the crystals recovered separately and ridden back to a launch facility. Castles would be very different affairs as troops could be literally rained down on their roofs. Castles would be small, with no flat surfaces and designed to take impacts on the roof. Since it would be hard to stop ships designed to smash into buildings, they would be expensive, complicated, and much less effective. You would have no walled cities, and borders would dissolve as launches from everywhere break down barriers.

Very similar to what Lupus said, an attacking force could go to the asteroid belt and grab a couple then drop them on the planet. Smaller asteroids could take out castles, cities, or armies. Larger ones could render entire planets uninhabitable. So you might want a solution or reasoning as to why they don't do this all the time. Like some sort of Geneva convention.


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