In Portal, using the portal gun to get to the moon is the obvious space travel usage, but I think people are overlooking how it’d let you trivially break the rocket equation.
Hell, you could build a >1g torchship using nothing but the ocean.
In Portal, using the portal gun to get to the moon is the obvious space travel usage, but I think people are overlooking how it’d let you trivially break the rocket equation.
Hell, you could build a >1g torchship using nothing but the ocean.
I’d do the math on how much thrust you’d get out of sticking one portal at the bottom of the Mariana Trench and the other in a ship, but I think it’d maybe be slightly tricky because you’ve got yourself an inertialess thruster right there, which is slightly illegal according to physics.
The Einstein cops are gonna show up and impound your spaceship
@foone@digipres.club @nyrath@spacey.space Portal also added more fun ways to break physics by giving Chell the magic inertia-canceling boots.
Not addressed in the game: What happens when the relative velocity between the ends of a portal is very high and something bigger than a molecule gets dropped through it.
And that’s just thinking about a static arrangement of portals. You could also use a dynamic arrangement where you use gravity to accelerate mass to arbitrarily high speeds and then fling it out the back
@foone@digipres.club This is (spoilers!) one of the weaponizations of space magic in The Paranoid Mage indeed.
@foone@digipres.club
I think - I am a physicist but not a rocket engineer - that a portal wouldn’t propel anything.
Putting a portal on the underside of the spaceship and another in the deep ocean just makes the two of those places adjacent. The water would spray into space (and probably immediately freeze) but the reaction force wouldn’t be on the ship: there’s no water pushing back against it, after all. If there’s any reaction force it would be against the ocean.
If you could make portals bigger you could also have a fun setup where you build your spaceship and then just let gravity accelerate it though a portal-loop.
You get going as fast as you want, then just swap the portals so you’re now aimed at Mars.
@foone@digipres.club I get the feeling it would be amazing for some fraction of a second before either:
Relativity smacked you in the face
Friction did it’s thing
Physics gets angry and stops the earths rotation around the sun
Or
The people running this simulated universe turn it off and patch that bug before starting over.
Anyway the lazy, boring way to use a portal and pretend you aren’t violating a bunch of physical laws is to just use it for fuel transport.
You have a bunch of fuel on the ground, a tiny tank on your rocket, and you keep topping off the rocket’s tank by piping in the fuel.
BTW, as a variant on the kzinti lesson, the portals are extremely dangerous as a weapon, because of how good they are as a weapon.
Ignoring the obvious ways to fight with them like opening a portal on the enemy’s hull, shoving out a nuke and then closing the portal…
You could also just have a rock that you’re letting accelerate to arbitrary speeds in a vacuum. That’s free unbounded kinetic energy, the only limitation being the “charge” time.
This isn’t a ship-destroying weapon, this is a civilization-ender if not planet-killer.
You’ve got a projectile moving at a significant fraction of the speed of light. This is a relativistic weapon: it’s going to hit harder than if it was a nuke.
@foone@digipres.club honestly, a baseball at a significant fraction of c is sufficient - you don’t need a tungsten crowbar
You can also make it bigger by not using a roughly round rock and instead using a long rod of the densest material you can get your hand on.
But mass you pay for, speed you don’t.
Like, the worked example from Atomic Rockets has 7 kilograms of cat litter moving at 90% of lightspeed hitting a stationary target with 195 megatons of kinetic energy.
https://www.projectrho.com/public_html/rocket/spacegunexotic.php
But yeah this is the ultimate doomsday weapon. You can accelerate indefinitely for free, you just have to wait.
(and if you can put your portals in orbit of a more massive object, you get faster acceleration than 1g)
So you don’t need more than a portal gun, a tungsten rod, and some time to blow the atmosphere off a planet.
@foone@digipres.club So with something 4 times bigger than the Tsar Bomba we could get a bag of cat litter to 90% the speed of light?
@foone@digipres.club That passage out of The Killing Star when the Relativistic projectiles hit Earth…
@foone@digipres.club yup. Doc Smith level planet busters are near trivial with portals
@foone@digipres.club I love this, just for the “Variant of the Kzinti lesson” reference.
@foone@digipres.club there are no unarmed spaceships
@foone@digipres.club k’chee u’riit maraai, indeed.
@foone@digipres.club I recall Peter F. Hamilton doing just that in one of his books. The nuke part at least. Not sure about the space rock yeeting.
@foone@digipres.club The Pierson’s Puppeteers did this to fuel probes in Ringworld. The only difference was their technology required a physical teleportation device to be placed at the destination instead of just opening a portal anywhere, & transmission was limited to the speed of light.
@foone@digipres.club The hard part will be aligning the (“outgoing”) portal so perfectly, that you do not end up anywhere but your far away target.
@foone@digipres.club I seem to recall Larry Niven played with this stuff in his teleportation short stories in the 70s (notably “All the bridges rusting”). And I had fun with it in “Glasshouse”.
@cstross@wandering.shop @foone@digipres.club Peter F. Hamilton also uses the idea in a lot of various ways in his Salvation books. E.g. why deal with complicated propulsion systems when you can chuck the ingress end of a portal into a star and stick the egress end on the back of your ship.
@abursey@me.dm @foone@digipres.club A portal gun (with the other end of the portal inside the photosphere of a blue-white supergiant) makes a really neat blaster!
@cstross@wandering.shop @foone@digipres.club @abursey@me.dm Backblast might make it a weapon of last resort, though.
@lispi314@udongein.xyz @abursey@me.dm @cstross@wandering.shop true, but the fun part of a portal-ship is that there’s really no difference between a crewed lander and a remote-controlled doomsday missile.
if you land somewhere uninhabited and/or friendly, you can drop a portal and then send people through. if it’s unfriendly, you open the supergiant portal, and have the portal gun throw itself through a return-home portal that instantly closes. you build another ship
@foone@digipres.club thread a rope with a weight through two vertical portals so the rope is pulled through infinitely as the weight drops.
Now you have infinite rotational energy to run a generator and the thermodynamics police are definitely going to break down your door
@foone@digipres.club That raises a question: Are portals subject to reaction forces? If not, a deflector would still be required and solid ‘fuel’ may be less usable.
@foone@digipres.club Portals can’t move, so it wouldn’t be able to function as a propellant. What you’d have there is a high volume water cutter.
@foone@digipres.club I don’t think mass exiting through a portal imparts any thrust to the surface the portal is on, so not sure this works. but the remote fuel tank and the “infinitely falling object continuously pulls on gravitational partner” both seem legit to me. as well as the time travel implications.
@foone@digipres.club every time I see inertialess thrusters discussed I always end up thinking it would be great to have a Skylark show made. I always enjoyed those books when I was a kid.
@foone@digipres.club Einstein cops are no joke. They’ll put you in a cell with no external references and you won’t be able to tell if it’s even on Earth vs constantly accelerating in deep space.
@foone@digipres.club I believe it’s also illegal according to the game, in that a portal can only be placed on a stationary surface.
I believe the portal would break as soon as the ship moved.
@foone@digipres.club you could already make perpetual motion machines with the mechanics you have available in-game so i think that’s probably fine in this scenario
@foone@digipres.club xkcd did most of that math already, just need to multiply by density of water I believe: https://xkcd.com/969/
@foone@digipres.club
I think Niven once wrote an essay on this, in the context of teleportation booths. He posited that conservation of energy would be satisfied by temperature changes. In this example, the water would come out of the portal at cryogenic temperatures.