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What future space combat would really look like

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Re: What future space combat would really look like

#51

Post by quanticle »

zeteo wrote: post #44
quanticle wrote: post #7

This essay isn't all that realistic. I found this one [1] to have a far more realistic view of what space war would look like. Tl;dr: it's much cheaper and much more effective to lob comets at your enemy's homeworld than it is to fight with ships. [1] http://www.gwern.net/Colder%20Wars

The fighting methods in that essay still require ships (to sneak up into e.g. Kuiper's Belt). In any case, a big, dumb projectile can have its course changed with much less energy than required to fire it. The bigger it is, the earlier it will be detected; and the faster it goes, the smaller the angular deflection needed to miss its target.

He addresses that in the next paragraph:

If that’s not bad enough, one could envision flinging appropriate small moons or large asteroids from other solar systems. Why not? Boosting a large body to fractional c velocities and aiming it at a far away planet isn’t inherently any more absurd than building a ship and boosting it to fractional c. The motion of stellar bodies is famously predictable out for many centuries. The body could guide itself: add some small motors, and it could even correct for small errors in prediction. It would be the ultimate fire-and-forget weapon of mass destruction.

So you don't have to sneak up at all. You just need to have a solar system with a Kuiper Belt, and you've got all the arsenal you need. In fact, launch attacks from remote solar systems is preferable, since it gives your bullets more time accelerate before becoming visible to the enemy. They may have enough enough energy to stop an asteroid traveling at .5c. Do they have enough energy to stop one traveling at .9c?

Re: What future space combat would really look like

#52

Post by arethuza »

jasonkester wrote: post #28

I think Banks' The Algabraist got it about right. In fact, that whole book is crammed full of good "things we currently believe to be true about physics extrapolated as far as theoretically possible" ideas: "How do you navigate this thing?" "Point." "Point?" "Yes, point. It's all about having enough power. Fiddling around with calculations about DeltaV is really just a sign that you don't have enough power."

"It's all about having enough power."

That really does sound like the name of a Culture GSV.

[Correction - No Culture ship would be quite so lacking in gravitas, so I suspect a more likely name would be "Fiddling around with calculations about DeltaV"].

Re: What future space combat would really look like

#53

Post by rbanffy »

zeteo wrote: post #39
gerggerg wrote: post #32

Why would space war ships be manned when we're already flying unmanned vehicles on earth? I think we've touched on a reality of intelligent species coexisting in the universe. Space war would consist of staying hidden and probably nothing else. Plus, certainly people would be fighting over the planets or the technology (or maybe the amulet of Endor) so simply throwing comets and obliterating things wouldn't make much…

>Why would space war ships be manned when we're already flying unmanned vehicles on earth Because the longest distance on Earth is only about 0.07 light-seconds.

And why do you think they would be remote controlled?

If you put a smart enough brain inside it, you could just upload a copy of the crew (assuming you can digitize and run human minds, of course, something that seems easier than interstellar travel). This way, the ship would not be limited by its crew. The crews responses would also only be limited by available processing speed. And, instead of lifeboats, you could transmit the crew states. In fact, you could do that regularly across the fleet for synchronization and backup purposes.

And, from the inside, it could look exactly like a Constitution class federation starship. People younger than me would prefer a Galaxy class. I, myself, am in doubt between the Constitution and the Heart of Gold. Or a big bridge like the original Battlestar Galactica. The computer could easily generate a lot of red-shirts for added drama during battles.

Re: What future space combat would really look like

#54

Post by philwelch »

rbanffy wrote: post #48
philwelch wrote: post #42

I don't think space combat is even going to happen. Any combatant with the necessary wealth and technology to develop any space-combat capability is going to have significant terrestrial interests and nuclear weapons already, at which point they're already subject to MAD and won't engage in direct combat anyway. At the very minimum, you would need economically and politically independent Moon/Mars colonies, and even…

> Any combatant with the necessary wealth and technology to develop any space-combat capability is going to have significant terrestrial interests Imagine a colony that long ago severed its ties with Earth (or whatever other terrestrial body they started from). Living off comets and asteroids seems entirely feasible and it's a much harder to attack/easier to defend set up.

Complete economic isolation from the earth seems very unlikely, at the very least because it wouldn't actually benefit anyone.

Re: What future space combat would really look like

#56

Post by dalke »

Avshalom wrote: post #37
talmand wrote: post #26

Earlier quoted context omitted.

How can that be? Space is big, we cannot even properly comprehend how big it is. I'm talking just in our immediate vicinity. If I took, say, three of the world's largest ships, put them together to form one ship and then placed it in a random spot somewhere within the orbit of Pluto; how long would it take you to find it? Keep in mind I'm not talking within the orbital plane, I'm saying within the sphere of the solar…

It's two things basically: -You can do a full survey in about 5 hours with one telescope these days. -Ships are very bright, don't look anything like stars and CCDs are very sensitive. http://www.projectrho.com/rocket/spacewardetect.php has a good break down.

I've been trying to get a sense of how effective these scans are. Asteroid 2005 YU55 was discovered 28 December 2005. It's about 400m in width, which is the length of the biggest vessel we have. When it was discovered, it was 0.8AU from the Earth, and its orbit is inside that of Mars.

This tells me that 6 years ago we did not know all of the +300m asteroids within the orbit of Mars. How much better are we now? I read the page you linked to, but that didn't list actual numbers based on asteroid searches.

There's an estimated 4,000,000 asteroids in the solar system of size 300m or larger. I sincerely doubt that a telescope survey of 5 hours finds 1 million+ asteroids each night, otherwise that number would be pinned down a lot better. (It can't find all 4 million because at 5 hours there's still substantial portions of the sky unseen.)

Re: What future space combat would really look like

#57

Post by Splines »

As mentioned in the post, David Weber's Honor Harrington series operates very much like this. I've read a few of them and enjoyed it. Nuances in space combat in his stories tend to be important.

http://en.wikipedia.org/wiki/David_Weber#Honor_Harrington_se...

Also, it's worth watching this scene from Mass Effect 2. It's amusing :)

http://www.youtube.com/watch?v=7GqqDCe4Yrs

Re: What future space combat would really look like

#58

Post by ew »

It was definitely an interesting read, however, I feel that fundamentally, for humans to reach the point where space combat is even feasible we will have solved so many more important problems that there won't be a need for fighting in the cosmos. Earth, in general, is at peace. We are largely struggling against terrorism, radical groups, and internal genocide rather than full scale, nation-on-nation wars.

No two democracies have gone to war, ever, and that's an important indicator of our future. Don't get me wrong, we have A TON of human rights, poverty, and equality problems, but things are rapidly improving directly proportional to our technical capabilities.

By the time we can even construct two ships capable of having a realistic fight in space we're more likely to send them exploring rather than duke it out. All current governments even capable of dreaming of getting in to space work together on the problem, sharing resources and knowledge.

To recap, we'll never go to war in space. I also doubt any other intelligent life with the capabilities to do so will need to attack us because they've solved any problems requiring them to do so.

Re: What future space combat would really look like

#59

Post by andrewflnr »

sp332 wrote: post #31
yock wrote: post #19

Earlier quoted context omitted.

The linked article seems to mention re-entry friction as a problem yet-to-be-solved: The system would also have to cope with atmospheric heating from re-entry, which could melt the weapon. Then there's the question of whether or not heat is truly the most immediate issue. NASA and USAF had to actually fly an airplace near and past the speed of sound to see how the properties of the atmosphere changed when compressed.…

I don't think melting is that big a deal. It's still the same amount of mass, only now it's molten steel instead of steel rods.

It'll start breaking into little blobs, though, which will have less and less power.

Re: What future space combat would really look like

#60

Post by zeteo »

quanticle wrote: post #51
zeteo wrote: post #44

Earlier quoted context omitted.

The fighting methods in that essay still require ships (to sneak up into e.g. Kuiper's Belt). In any case, a big, dumb projectile can have its course changed with much less energy than required to fire it. The bigger it is, the earlier it will be detected; and the faster it goes, the smaller the angular deflection needed to miss its target.

He addresses that in the next paragraph: If that’s not bad enough, one could envision flinging appropriate small moons or large asteroids from other solar systems. Why not? Boosting a large body to fractional c velocities and aiming it at a far away planet isn’t inherently any more absurd than building a ship and boosting it to fractional c. The motion of stellar bodies is famously predictable out for many centuries.…

Reaching even a small proportion of the speed of light requires prohibitively high amounts of energy. Let's consider the energy required to accelerate Haley's Comet (relatively small at 2.2e14 kg) to half the speed of light (v = c/2):

E = mc^2 / sqrt(1 - v^2 / c^2) ~= 1.15 mc^2 = 1.15 * 2.2e14 kg * (3e8 m/s)^2 = 22.77e30 J

For comparison, the Earth absorbs each year about 3.85e24 J of solar energy, so we're talking about six million years of total incoming solar.

Assuming two societies with similar technology, it will cost vastly less energy for the defender to give the object a small nudge than it cost the attacker to propel it in the first place. The attacker would do much better to invest into a fleet of ships that can respond to contingencies and adapt to the defender's response.

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