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imported_Ziggy
2004-May-12, 08:29 PM
Ok, it's the far future. Your average interstellar ship travels at near light volocities. By now we should have made contact with dozens of alien civilizations as advanced or more advanced then us. But now interstellar space is becomeing over crowed. And worse yet, a advanced, agreesive civilization (the sublight version of the Borg), is on a rampage to destoy less advanced interstellar civilizations like us and our neiborghers. Your the head of government for all human colonies. How would try to work out these two big problems with the help of alien governments?

SkyBoard
2004-May-23, 04:05 AM
Don't over-blow the scifi, Zig...

damienpaul
2004-May-23, 07:42 AM
I'd wake up from that terrible dream...:P

GOURDHEAD
2004-May-23, 12:35 PM
Usually the best defence is offense; however, for interplanetary war, defence has an overwhelming advantage--efficient use of energy and overwhelming resources. Propellant availability and usage makes waging war even within a solar system extremely difficult and between stellar systems almost impossible. The aggressor would we better off "terraforming" rather than conquering.

zrice03
2004-May-23, 06:54 PM
I'm with GH. There's enough space in the galaxy for even a trillion advanced civilizations.

If you had to do interstellar diplomacy, it would take an extremely long time. Probably long enough that nobody would actually care about it.

Jan
2004-Jun-25, 01:04 AM
the world needs a good lay that there has been a alien contact so we would see the progress of inventing a interstelar spaceship to travel long distances, happen in our time..... the earth is getting boring......




jan

eburacum45
2004-Jul-07, 07:45 AM
Attacking a well defended, entrenched solar system is a pointless exercise.

If the defenders can call upon the energy of an entire solar system it will almost always be able to destroy an approaching warship or missile, which can only hold a fraction of the energy of a main sequence star.
Additionally there is no reliable way to avoid detection by active or passive sensors, particularly gravity wave detectors; once a defending system has a LISA system it will be able to detect approaching warfleets far away.

So if all the planets in your loose federation turn their solar systems into fortresses, the aggressive aliens (who have to bring all their energy with them) will not be able to conquer territory successfully.


This assumes the aliens do not have some sort of magic star busting technology; in which case the only defence is to get that same technology or similar and attck them.

po-
2004-Jul-17, 05:07 AM
Originally posted by Jan@Jun 25 2004, 01:04 AM
the world needs a good lay that there has been a alien contact so we would see the progress of inventing a interstelar spaceship to travel long distances, happen in our time..... the earth is getting boring......




jan
im with you there... the problem is our generation will never see the energy requirements that we know are necessary for such travel. oh well theres always cryogenics :lol:

QJones
2004-Jul-29, 11:29 PM
Once solution is to extend your lifespan. This is actually quite do-able. In addition, increasing the energy harnessing capabilities will have to occur.

Finally, we are already broadcasting - for good or ill - at the speed of light. So far, over 1800 systems have received signals from us.

GOURDHEAD
2004-Aug-02, 03:57 PM
...the problem is our generation will never see the energy requirements that we know are necessary for such travel

They that are in great darkness shall see a great light. Some of us, namely me, have already seen such a light as have you. Recognition is the problem. Google on "interstellar transportation".

ASEI
2004-Aug-05, 04:43 PM
How would you stop a 200 ton rod of enriched uranium travelling at 99.999% the speed of light towards one of your planets? Sounds like a good attack plan to me, if you don't care about inhabiting the planet afterwards. It would cause one hell of a nuclear explosion when the two masses collide at relatavistic speeds and fission. It is basically a projectile, so it wouldn't emit anything, it wouldn't have any enourmous energy signature or anything, and it would be rather small compared to most space objects. Virtually undetectable at interstellar ranges I would think, and once it is within your system, you have about two or three hours to do something about it.

Yes, I have played Stars! too often. Packet attacks stink.

If the enemy has his homeworlds bombed, he won't have much of a population left to expand or grow with. Maybe enourmous interstellar lasers or particle beams can be used to fry enemy colonies all the way in other star systems if you have figured exactly how they orbit.

You're minding your own business, sipping coffee, and suddenly your asteroid colony gets dosed with neutrons, the surface of the Earth gets toasted with that plutonium rod impact, and no one is answering your calls, and best yet, you don't know which system any of this came from. 60% of mankind is dead. If you complain, it will take at least ten years for anyone to answer on interstellar scales. Wasn't us . . . :rolleyes:

GOURDHEAD
2004-Aug-06, 07:02 PM
How would you stop a 200 ton rod of enriched uranium travelling at 99.999% the speed of light towards one of your planets? Sounds like a good attack plan to me, if you don't care about inhabiting the planet afterwards.

Deflection may be a better defense. Use an asteroid.

The purpetrator would be better served using the energy it would take to launch such an attack by making other sites more habitable to her species. The intelligence required for such an attack effort would cause them to do otherwise.....I hope.

Bobunf
2004-Aug-07, 01:27 AM
Two hundreds tons of anything traveling at 99.999% of the velocity of light would have kinetic energy, considering the relativistic effects equivalent to

.99999c^2*.5*(m * 1/(1-.(99999c^2/c^2))^.5)
or
c^2*m *158

the energy contained in a very efficient 200 ton U235 fusion bomb would be c^2*m*.0004 since only 4/100ths% of the uranium is converted from matter into energy.

c^2*m *158 is about 395,000 times greater than c^2*m*.0004.

The composition of something with relativistic speeds is completely irrelevant to the energy it would deposit on anything it ran into.

eburacum45
2004-Aug-08, 02:58 PM
We have played this scenario out at Orion's arm as well; the kinetic missile attack is very powerful, but not infallible.

First of all, if you launch the kinetic missile from near the target system, the target can see the acceleration taking place; this liberates a lot of energy, which gives a lot of warning, and allows the target time to get a shield in place,. A kinetic missile can be intercepted and destroyed by a reasonably sized asteroid; if the solar system is properly defended it can gather all the energy from its parent star and concentrate that into shield asteroids, particle beam weapons and lasers, which are able to stop a single kinetic missile. If the attackers are launching the missile from the Oort cloud of the target system they are going to have a very limited amount of energy compared to the defenders; superior firepower and preparedness will win out.
Very few of the kinetic missiles will reach their target.

To avoid detection during the acceleration phase the attackers could launch their kinetic missiles from a nearby star; this increases the fire power available, so they can launch as many as they can, but the missiles will be detectable because of their friction with the interstellar medium. They will glow like little atom bombs as they encounter hydrogen atoms at high fractions of light speed. Additionally, the effects of relativity and light aberration makes it impossible to steer fast moving objects accurately; it is always easier to find your target world after decelerating from interstellar speeds, as spacecraft normally do. If you don't decelerate the effects of relativity crowds the forward view into a tiny portion of the field of view, and speeds up transit time to such an extent that the target would be practically invisible.

So attacking a well defended solar system is always going to be more energy consuming than defending it, and may well have little result apart from being a contant annoyance to the inhabitants.

ASEI
2004-Aug-08, 09:34 PM
Why near? If you could control the accuracy of the projectile, and predict where the planet will be, you can plan an interception and just let a cold, small projectile fly. Maybe millions of relatavistic pebbles.

Yeah, granted. I guess the composition wouldn't matter much. Still, there may be a possibility of liberated nuclear energy as well, if the nuclei collide at relatavistic speeds.

If it is travelling fast enough, and inert enough, then I don't see how lasers would stop it. They could heat it up and melt it, but then you just have a liquid flying at you at relatavistic speeds. If it evaporates, then you get hit with vapor and gas at relatavistic speeds, unless you can somehow apply so much energy that it evaporates in such a way that it can miss the planet.

You probably would know the orbits of all the planets and moons before you attack, in which case you wouldn't need such weapons and beams to be able to steer.

The purpose of attacking wouldn't be to invade or take anything over, since taking a system would be more energy consuming than building whatever you want. But it may have a purpose if you wanted to wipe out another civilization by destroying most of its population.

So they would glow from friction, huh? Hmm. If they aren't stealthy, then a large portion of the advantage to this attack is lost. Maybe there are ways to use magnetic shielding and ionization to cavitate the interstellar medium and reduce the signature.

eburacum45
2004-Aug-09, 08:08 AM
Yes, I thought that even destroying a kinetic missile would simply break it up into smaller pebbles, which would then be dangerous individually; but as the pebbles interact with the dust in the solarsystem they will vapourise, so then you have got a mass of relativistic dust or vapour-

when you calculate the energy in this mass of vapour it is on a similar magnitude to a coronal mass ejection, which occur all the time in our solar system. This fast moving mass of gas would be deadly if you could aim it, but all the control systems are dust.

Now we had trouble aiming the kinetic missile over interstellar distances, as the exact location of a planet could not be predicted accurately enough because of chaotic effects in the galactic gravitational system; you could get close, but not close enough to guarantee a hit. Because of the aberattion of light and relativity it would be necessary to have an aiming telescope on the front of the missile much more sensitive than Hubble, which would be destroyed anyway by erosion with the interstellar medium.

Keep sending the missiles over and one or two will get through; the defending civilisation has to burrow underground to avoid damage; this becomes a war of attrition in which both sides are using vast amounts of energy to achieve very little.

ASEI
2004-Aug-09, 12:56 PM
I thought that over the course of a relatavistic projectile's flight (at most 100 or 200 years), that a planet would have a nice, stable orbit that wouldn't alter much more than a few cm from it's usual course. Most of the time, the orbit of a planet or moon can be predicted almost exactly by taking into account only the nearer, or more massive objects in the solar system. That's how we aim our probes and sattelites.

eburacum45
2004-Aug-09, 02:38 PM
The location of the star actually changes on those kinds of timescales;stars move surprisingly fast and chaotically.
In general the number of variables makes it too difficult to aim a dumb missile and too difficult to see where you are going.

Actually the trick is not to go qite so fast; if you go slow enough to see where you are going, it makes it easier to hit you with a shield asteroid or particle beam; so there is an optimum velocity somewhere around 0.7c where the attackers get the best of both worlds.

Isuppose that is probably fast enough for most purposes...

Betelgeuse
2004-Aug-09, 06:51 PM
Backt to the very first post - if "aliens" came to earth, chances are, we wouldn't actually know if they were creatures from other planets due to apperance - we don't know exactly what and "alien" looks like, so the chances f having an alien relation is very low - but, who knows!