Spaceships and Science fiction


by SHISHKABOB
Tags: fiction, science, spaceships
PrepperMike
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#37
Feb8-12, 01:36 PM
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read Ian Douglas.
GTOM
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#38
Feb8-12, 03:14 PM
P: 107
In other threads, we had a consensus, that fighters and corvettes are "brown water navy", operating on orbit, and big shafts of moons and asteroids.

Otherwise, I 've also thought about beam empowered fighters and small missile control ships.

I see that trilogy ruled out AIs.
PrepperMike
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#39
Feb8-12, 03:39 PM
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Ian uses AIs for high speed stuff that human reaction times can't handle, but other stuff he feels is best done by humans. His biggest argument against AI is do you want control of high powered weapons with an AI or a human?
Ryan_m_b
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#40
Feb8-12, 03:56 PM
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Quote Quote by PrepperMike View Post
Ian uses AIs for high speed stuff that human reaction times can't handle, but other stuff he feels is best done by humans. His biggest argument against AI is do you want control of high powered weapons with an AI or a human?
That's a meaningless question unless you provide a detailed description of the characteristics and capabilities of the proposed AI.
SHISHKABOB
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#41
Feb8-12, 04:19 PM
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a good way to force action sequences or whatever is to make up magical- er I mean fictional chemicals or elements that have some oddly specific behaviors. For example, in the anime series Legend of the Galactic Heroes, there was some funky gas stuff that exploded very violently if lasers or guns were shot through it. Sort of like the laser vs. shields thing in the Dune universe. This forced armies to duke it out in fancy armor, crossbows and giant battleaxes. The rest of the show was about giant space battles where the ships lined up like 18th century European line infantry and space politics.

But they got to add in some really cool face to face melee combat scenes because of some magical gas that they made up.
Ryan_m_b
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#42
Feb8-12, 04:28 PM
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Quote Quote by SHISHKABOB View Post
a good way to force action sequences or whatever is to make up magical- er I mean fictional chemicals or elements that have some oddly specific behaviors.
That's the cool thing about speculative fiction. You propose some sort of technobabble and explore the societal and practical ramifications. For instance, if this gas explodes violently then can it not also be harvested as a powerful fuel? Simply store it in gas canisters and spray little bits at a time into a laser lit engine. Or store it at very high concentration and then light a laser inside the canister as a bomb.
GTOM
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#43
Feb9-12, 02:25 AM
P: 107
Yes I watched Legend of Galactic Heroes, i dont know if they used the Zephyr (I think) for propulsion purposes as well.
(Otherwise I disliked that series, Yang always knew what the enemy is planning, they launch a small attack, Send there our whole navy! Yeah why not, next time, they launch a very big attack, and of course it is only a decoy...)

Basically, in deep space, where arent civilans and neutral parties, AIs cant do much wrong...
In case of orbital patrol, human decision is needed, and i doubt that remote control is always enough, there can be spys for example, that can hack the system to create an international scandal or something like that.
Also you have more options to rescue pilots.



I had the idea, that aliens can deploy self-replicating nanobots to Earth, to infect computers, turn our own robots and infrastructure against us...
They want everything to be ready, by the time they arrive.

However, if their plan A fails, they can launch a relativistic torpedo against Earth...
Is it possible to counter, without hyperspace senses or thing like that?
(It is so magical, one could even bring the Force to the image)

Although... if humans can learn the whereabouts of the alien homeworld, they can also threat them with R-torpedos.
Ryan_m_b
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#44
Feb9-12, 03:29 AM
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Quote Quote by GTOM View Post
However, if their plan A fails, they can launch a relativistic torpedo against Earth...Is it possible to counter, without hyperspace senses or thing like that?
(It is so magical, one could even bring the Force to the image)

Although... if humans can learn the whereabouts of the alien homeworld, they can also threat them with R-torpedos.
Without magic technobabble like a forcefield not really. The most you could do is fill your system with highly sophisticated gravity sensors to sense the RKV as it comes. You might not have much time at all because if it is travelling at 0.9c (which btw is roughly the velocity an object needs to reach for its kinetic energy to reach half its rest mass) and you detect it at one light day out this means it is only two light hours away. If you do have time you could try to divert its path with powerful lasers or try to through mass in the way to deflect it but I doubt you could really do any of that.

Charles Stross dealt with this issue in his novel Iron Sunrise. In it various factions have STL-deterrents hidden in their Oort cloud operating under a dead-man switch. If they don't receive a signal every X hours they launch towards a target planet (trying to find a tiny ship, possibly stealthed from across a system would be next to impossible). This largely stopped factions invading each other for fear of severe retaliation years later.
GTOM
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#45
Feb9-12, 04:17 AM
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If a RKV hits a one kilogram mass before the planet, what would happen to it?
The energy of the collision could turn it into a dissolving plasma cloud or dont?
Ryan_m_b
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#46
Feb9-12, 04:33 AM
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Quote Quote by GTOM View Post
If a RKV hits a one kilogram mass before the planet, what would happen to it?
The energy of the collision could turn it into a dissolving plasma cloud or dont?
At around 0.87c the kinetic energy of an object exceeds half it's rest mass. So a one kilogram RKV travelling at 0.87c relative to the planet will have the kinetic energy of e=0.5*c2 = 4.5 petajoules = ~10 megatonnes of TNT (~600 Hiroshima bombs). At that speed it would get through the atmosphere in less than a millisecond and cause massive devastation to the area it hit (akin to a nuclear explosion plus an earthquake). Some quick googling tells me that the meteorite that killed the dinosaurs released ~0.5 Yottajoules of energy which would be the equivalent of a 5 kilotonne RKV travelling at 0.87 which works out to be roughly the mass of 50m x 10m x 10m of ice.

This is something that a lot of SF authors forget in their haste to write about relativistic ships the size of super-carriers and cities. The very ships you have littered in your setting as though they were sprinkles on a cake could all be converted to weapons thousands of times more powerful than the meteorite that caused the K-T mass extinction! (this is also known as Jon's law or the Kzinti lesson)
GTOM
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#47
Feb9-12, 05:14 AM
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I can see, but if you try to put a brick in the way of the RKV well before it hits the planet?
Would that mean, that only the brick disintegrates in the collision, or the RKV also?
Ryan_m_b
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#48
Feb9-12, 05:43 AM
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Quote Quote by GTOM View Post
I can see, but if you try to put a brick in the way of the RKV well before it hits the planet?
Would that mean, that only the brick disintegrates in the collision, or the RKV also?
Whatever you put in front of an object travelling that fast would just be disintegrated, like a wet tissue paper thrown in front of an artillery shell. It may slow the RKV down a negligible amount but what you really hope or is to divert its course ever so slightly so that it misses its target. More likely though is that it may cause the RKV to break up but even if it did it wouldn't change the amount of energy that is about to hit: whether it hits the planet in 1 piece or 1 million pieces the same horrendous amount of energy is about to be released.
SHISHKABOB
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#49
Feb9-12, 11:48 AM
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my problem with relativistic weapons is how the heck do you aim them properly
Ryan_m_b
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#50
Feb9-12, 11:49 AM
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Quote Quote by SHISHKABOB View Post
my problem with relativistic weapons is how the heck do you aim them properly
What do you mean? Why would it be a problem to just aim, accelerate it up to a high fraction of C and watch the fire works? If long distance is a problem add some form of sensor and some thrusters to tweak the course. Even a small fraction of a degree course change could have big consequences after light hours-years
SHISHKABOB
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#51
Feb9-12, 12:20 PM
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Quote Quote by Ryan_m_b View Post
What do you mean? Why would it be a problem to just aim, accelerate it up to a high fraction of C and watch the fire works? If long distance is a problem add some form of sensor and some thrusters to tweak the course. Even a small fraction of a degree course change could have big consequences after light hours-years
this may be a misunderstanding on my part, but wouldn't it take a looot of energy to change the course of something moving extremely fast?
Ryan_m_b
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#52
Feb9-12, 12:34 PM
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Quote Quote by SHISHKABOB View Post
this may be a misunderstanding on my part, but wouldn't it take a looot of energy to change the course of something moving extremely fast?
Kind of, by engaging in any kind of thrust you change the velocity. Simplistically think of two objects on a grid: A and B with the top being North, bottom South etc.

A is travelling north at a speed of 1 square per second. B is travelling north at a speed of 10 squares per second. Both of them apply thrust so that they are moving west at 1 square per second. For A this means that for every square it travels north it travels 1 west (creating a 45 degree angle if this grid were a graph). For B it travels 1 square west for every 10 north.

However you only have to nudge a tiny bit to be very off course over long distances. Let's posit B (a RKV now) travelling at 150,000,000 mps (~0.5c) and at some point it thrusts to one side (let's say port) so that it is travelling 1 metre to port for every 150,000,000 metres it travels forward. Over the course of a light hour (two hours of travel) it is now 3.6 km off course to port. Over a light year it would be 62,000 km off course!

And that is only supposing it sticks to the measly thrust that generates 1mps to port!
SHISHKABOB
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#53
Feb9-12, 01:18 PM
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right, I see now. Usually I imagine relativistic weapons as big chunks of stuff that don't have thrusters on them, but I guess it isn't unreasonable to put things like that on something like that.
Ryan_m_b
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#54
Feb9-12, 01:21 PM
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Quote Quote by SHISHKABOB View Post
right, I see now. Usually I imagine relativistic weapons as big chunks of stuff that don't have thrusters on them, but I guess it isn't unreasonable to put things like that on something like that.
Without propulsion how do you get them up to relativistic speeds ? For me an RKV is just a spaceship on autopilot; the only difference between a relativistic space ship and a weapon is how it plans to end its journey.


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