Portal Combat

[PeZook]

The idea for planetary missions is neat: you'd elliminate all supply issues if you could just have a portal up there. This makes colonization of the solar system a total cakewalk, if it can be done with the tech: you just need to get somewhere once, and then expand the infrastructure using standard Earth stuff.

And public transit woes are finally elliminated. Simply replace railways/air connections with a network of portals, thus massively increasing efficiency. No more traffic jams!

[Samuel]

They use something like that in A Boy and his Tank. Who needs FTL when you can simply put portals in probes and instantly deliver fuel, so they go faster and faster until they get near c. Then deploy a portal in the new system. Easy colonization of the galaxy.

[erik_t]

Point of fact: Any two unique points on the surface of the Earth are accelerating with respect to one another (since they're at different radius and/or latitude). Since velocity can be frame-of-reference'd away in non-relativistic circumstances, the portal gun is unlikely to care about absolute velocity (I still don't recall if you can define such a thing. Let's not talk about relativity any more ok?). It definitely doesn't care about small relative acceleration, as long as this acceleration does not vary with time. It seems plausible to me that the portal gun only cares about changes in relative kinematics after portal generation. If this is the case, then launching from geostationary portalsats is A-OK.

I believe this is the preferred interpretation, since the portals cannot form on surfaces whose acceleration varies with time, regardless of the magnitude of this acceleration. There are no objects in the game that have non-time-varying acceleration that cannot have portals formed on them, as far as I remember. It would be interesting to know if, say, a portal could be formed on the wall of a constant-angular-velocity large-radius cylinder.

[Steel]

Point of fact: Any two unique points on the surface of the Earth are accelerating with respect to one another (since they're at different radius and/or latitude). Since velocity can be frame-of-reference'd away in non-relativistic circumstances, the portal gun is unlikely to care about absolute velocity (I still don't recall if you can define such a thing. Let's not talk about relativity any more ok?). It definitely doesn't care about small relative acceleration, as long as this acceleration does not vary with time. It seems plausible to me that the portal gun only cares about changes in relative kinematics after portal generation. If this is the case, then launching from geostationary portalsats is A-OK.

I believe this is the preferred interpretation, since the portals cannot form on surfaces whose acceleration varies with time, regardless of the magnitude of this acceleration. There are no objects in the game that have non-time-varying acceleration that cannot have portals formed on them, as far as I remember. It would be interesting to know if, say, a portal could be formed on the wall of a constant-angular-velocity large-radius cylinder.

The cylinder wall would be indistingishable from the ceiling of a building on the surface of earth, and we know the latter works, so the cylinder should work too.

If we go from in game observations, we see that portals always close if the object they are attached to moves, regardless of whether there is another end to the portal. The issue cant be relative motion between the ends, as one end can be disrupted without the presence of another, and nor can it be acceleration, as the portals do ok at all points within the lab located on the surface of the earth. I cant really think of an (outside of the HL2 engine just cant calculate portal opening fast enough to keep up with a moving aperture) reason why the portals cant cope with being moved.

Saying "the portals cannot form on surfaces whose acceleration varies with time" doesnt make any sense. How does the portal "know" that its acceleration is varying explicitly with time?

[Oskuro]

I haven't played the game yet (the box is on my desk, staring longingly at me), but the idea proposed earlier about using portals to enhance armor is intriguing.

Say, you have a Tank that creates a portal on its frontal armor (maybe an enhanced version that extends the portal to the actual shape of the plating), thus becoming invulnerable to attack.
Say you set both portals as part of the same frontal armor (say two adjacent squares), projectiles would be reflected back at the attacker.

I'm not sure about movement. Can the portals be placed on an objetc that moves as long as they are both on the same object? If the can't move at all, they would be useful for stationary defenses. If they can be affixed to the same moveable object, then even a riot shield could be made to "reflect" incoming fire.

[Ryan Thunder]

The movement issue seems to be relative to something besides the portals themselves, or the portal creator.

This would seem to lend credence to the idea that the portals are somehow being fed energy from elsewhere in the facility.

Here's my theory; portals require a constant input of energy to maintain. The portal gun beams power to them based on where it expects them to be, but if the portal is moved (within some margin of error) from that location, the portal gun has no way to detect that it has moved, and continues to beam power to where it expects the portal to be, rather than where it is. The requisite power is no longer supplied to the portal, and it subsequently collapses.

There are variations on this, but the short version of it is that the portal gun
1. Maintains the portals
2. Needs to know where they are to maintain them
3. Has no way of detecting unexpected portal movement
4. Is able to account for its own movement

Its a safe bet that the Portal gun can't detect its own portals, I think, because Glados' defense turrets don't seem to be able to detect them, either.

[Ryan Thunder]

Sorry for the double post, but I just thought of some implications;

What you can do with the portals would only be limited by how predictable you expect their motions to be relative to the portal gun, the relationship between the effectiveness of your Portal Maintenance Beams and distance to the portal to be maintained, and how the beams are affected by any materials that get in the way.

[erik_t]

Point of fact: Any two unique points on the surface of the Earth are accelerating with respect to one another (since they're at different radius and/or latitude). Since velocity can be frame-of-reference'd away in non-relativistic circumstances, the portal gun is unlikely to care about absolute velocity (I still don't recall if you can define such a thing. Let's not talk about relativity any more ok?). It definitely doesn't care about small relative acceleration, as long as this acceleration does not vary with time. It seems plausible to me that the portal gun only cares about changes in relative kinematics after portal generation. If this is the case, then launching from geostationary portalsats is A-OK.

I believe this is the preferred interpretation, since the portals cannot form on surfaces whose acceleration varies with time, regardless of the magnitude of this acceleration. There are no objects in the game that have non-time-varying acceleration that cannot have portals formed on them, as far as I remember. It would be interesting to know if, say, a portal could be formed on the wall of a constant-angular-velocity large-radius cylinder.

The cylinder wall would be indistingishable from the ceiling of a building on the surface of earth, and we know the latter works, so the cylinder should work too.

If we go from in game observations, we see that portals always close if the object they are attached to moves, regardless of whether there is another end to the portal. The issue cant be relative motion between the ends, as one end can be disrupted without the presence of another, and nor can it be acceleration, as the portals do ok at all points within the lab located on the surface of the earth. I cant really think of an (outside of the HL2 engine just cant calculate portal opening fast enough to keep up with a moving aperture) reason why the portals cant cope with being moved.

Saying "the portals cannot form on surfaces whose acceleration varies with time" doesnt make any sense. How does the portal "know" that its acceleration is varying explicitly with time?

Well depending on your reference frame, anything can be accelerating. It can't be relative velocity, because, as you say, one end can be disrupted without the other end even having been established yet. It has to be either velocity or acceleration, right? I can't think of anything else. The logical relaxation of these requirements is for the velocity or acceleration to be constant, since that is the situation we have in the Aperture Science labs. If a surface has changing acceleration (ie a door starting to open), the portal end will die. Presumably the portal gun couldn't have predicted this, and so when things started moving, it freaked out. It didn't know where the portal would end up going or what it would end up doing, so it closed it for safety.

So I hypothesize that acceleration changes are what stop portals. Of course here we get into the issue of looking at different reference frames and such. It's a complicated question that probably does not have an answer.

[Steel]

So I hypothesize that acceleration changes are what stop portals. Of course here we get into the issue of looking at different reference frames and such. It's a complicated question that probably does not have an answer.

Thats the point, the acceleration of the portal is constantly changing already, as we are on the surface of a rotating body. The direction is continually changed to be towards the centre of the earth.

The portals shutting off must be a local property, independant of the portal gun as well, as that can undergo extremely complicated unpredicatble movement without in any way affecting the portals.