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[Virex]

I'm thinking a dumb projectile type probe, intentionally designed to speed through the system. The antimatter would be something like a couple thousand atoms or something.

Using the following relativistic equation for the mass of antimater needed, I get:


1/2 m1 c^2 = m2 c^2/sqrt (1-(v/c)^2) - m2 c^2
m1 = 2 m2 /sqrt (1-(v/c)^2) - 2 m2
m1 = 2 m2 (1/sqrt (1-(v/c)^2) - 1)
m1 / m2 = 2 (1/sqrt (1-(v/c)^2) - 1)
Plotting that yields the following graph:
http://i.imgur.com/GygFI.png?1


As you can see, to accelerate a probe to 10% of the speed of light, an amount of antimatter equal to 1% of the mass of the probe needs to be expended. Since the change in mass of the probe is only 1%, we don't need to take the dwindling mass into account, so we can assume the probe needs to take 1% of it's mass in antimatter with it as fuel, assuming 100% propulsion efficiency. For a probe of 10 kg, that means 10 grams of antimatter is needed, which, if taken along in the form of protons, would cost 250 billion dollars (short scale) to make, according to this estimation

[PTTG??]

Virex, the antimatter isn't fuel; it's just a power storage medium for sending a signal; I figure it would produce some specific frequency with sufficient intensity to detect back on earth. That's my assumption. There may very well be a more efficient method of sending a signal. Since antimatter storage is an open question, that's not necessarily true.

Also, let's clarify something about "slingshots"- you can't gain more velocity from a slingshot maneuver than escape velocity for the body, and if you're already going faster than that, all you're going to do is make a very subtle deflection.

MetalSlimeHunt, I don't think you realize the level of physical impossibility we're talking about here. There's no way to use Daedalus as a weapon that's easier than building a real weapon from scratch. In that, it is like banning damp clay from being taken in an armory lest someone sharpen it, build a primitive kiln, and use it to stab somebody.

[10ebbor10]

The forum ate my previous post, which had all kinds of nice calculations

They can't do that. The design does not include enough fuel to move away and turn around to have a sufficient run up.

You could do a wide slingshot around one of the Gas Giants and have a decent space between you and Earth to accelerate in. Maybe not enough to hit max speed, but enough to accelerate to a speed that we do not want anything hitting Earth at.
The Orion drive has a 1 year arceleration cycle, at 100 g. It requires 1* 10¹⁵km runup. The farest Gas giant is 10⁹ km.

Besides, we're going to keep track of where these ships are(no stealth in space) and can easily intercept them. A flake of paint is enough to destroy a ship at those speeds, a shrapnel bomb would be impossible to evade and guarantee interception.

The question is whether or not we can mount such a defense against a surprise RKV attack in time. Blowing it up just outside Earth's atmosphere while all the parts are still moving at .1c would do us little good, for example. It would have to be intercepted quickly enough that Earth is missed entirely.
Remember the part where the ship travels at 0.1 c. There ain't going to be parts, just rapidly dissipating plasma. Which will be deflected by the solar wind and our magnetic field. Since we're going to fire the moment the ship starts to behave oddly(like braking)., we have more than enough time to lob a High yield nuclear warhead on top of it, or several heavy blocks of tungsten. The entire manoevers for a 0.1 c arceleartion will take at least 4 years, so you have plenty of time to intercept it some place before Earth.

Besides, if we wanted to destroy all surface live we can already do that.

Right, but it would take multiple devices. No one nuke is capable of totally destroying the human race. There is a possibility that a nuclear weapon could be used without proceeding to MAD, but an RKV will have by definition doomed all humanity barring any offworld colonies.The Orion project uses 800 nuclear bombs to enter LEO(Low Earth orbit).  With that amount of firepower you can doom humanity anyway. Besides, this make useage of this even more unlikely, because there's no way for this to be the best option.

Also, the kinetic energy of a 50 kg 0.1 c impact would be more or less comparable to the Tsar bomba. Destructive, but not the end of Earth.

Project Orion's design called for a 4000 ton ship, which would be 3,628,740 kg, or 72,574.8 Tsar Bombas impacting Earth's crust at a single point if traveling at .1c (going by your figures). As the original Tsar Bomba had it's yield halved over legitimate fears that it could blast a hole through to the mantle, I rescind my previous claim that it would just destroy the surface and am now predicting that such a force would risk compromising Earth's structural integrity. Regardless of whether it does or not however, the entire atmosphere has been blown off and humanity is extinct.

Project Orion called for 800 nuclear bombs to enter orbit. With the firepower needed to get to 0.1 c you can obliterate Earth anyway. I don't understand how a 4000 ton ship can weight 3,628,740 kg. Sure it will destroy Earth, but there's no way a ship that large is ever going to be build.

The second part is a myth. The TSar Bomba's yield was limited because of economical reasons, fear for radiation and to allow the pilots to escape the blast radius. Even at full yield it would be several orders of magnitude to small to disrupt the Earth's crust, and beside that, It was detonated in the wrong place.

[Silfurdreki]

Just going to chip in a bit about antimatter storage, since I have a bit of knowledge about vacuum systems.

Simply put, you're not going to be able to store any relevant amount of antimatter for long. Even if you device some type of magnetic suspension canister and avoid contact with the walls you need a very near perfect vacuum inside to not have the ambient molecules eat the antimatter away in a matter of minutes at most.

The best vacuum that we can achieve today on Earth is something like 10^-12 mbar. At that pressure you still have over ten thousand molecules/cm³, which will impact your antimatter clump and eat away at it. This pressure is with constant pumping, as well, so even if you lose ambient molecules to annihilation with the antimatter, you would still get more molecules from the outside to take their place.

So unless you plan to build a particle accelerator in deep space, or device some kind of way to gather it there, you're not going to get antimatter onto your spacecraft, I'm afraid.

[GlyphGryph]

Can't you isolate the non-antimatter the same way you isolate the antimatter?

Anywho, MSH, I'm not quite sure I understand your fear. A severaly fragmented ship moving at .1c being a threat to life on earth - do you have anything to back up that? I doubt this thing would be manned, so if someone DID hijack it we'd have a ton of time to prepare to do something about it - they'd have to fly it away, and then back, and to get it up to remotely earth-deadly speeds, that's going to take a while.

And actually doing it, actually managing to aim the thing, seems like it would be more difficulty than stealing all America's nukes at once without anybody noticing. :/

I'm struggling to come up with a plausible scenario here where what you're describing could possible happen.

[MetalSlimeHunt]

I gave you the force calculations. That much mass moving at that speed will destroy the surface and then some. Even with insufficient acceleration and fragmentation it could still cross the "destroy everything" threshold, or if not then still the "mass devastation" threshold.

This actually taking place is, I admit, unlikely. We are however talking about the destruction of all life on Earth, and thus any non-zero chance of such is something to be concerned about.

[GlyphGryph]

Of course, getting a ship that can move at such speeds is kind of step one to avoiding the inevitable, 100% change of destruction plus the myriad probably more likely chances of destruction up until then that we face every day.

And... uh, I just reread the thread and I'm not actually seeing where you gave force calculations. I'm probably just missing it.

[MetalSlimeHunt]

And... uh, I just reread the thread and I'm not actually seeing where you gave force calculations. I'm probably just missing it.

Also, the kinetic energy of a 50 kg 0.1 c impact would be more or less comparable to the Tsar bomba. Destructive, but not the end of Earth.

Project Orion's design called for a 4000 ton ship, which would be 3,628,740 kg, or 72,574.8 Tsar Bombas impacting Earth's crust at a single point if traveling at .1c (going by your figures).

[10ebbor10]

I gave you the force calculations. That much mass moving at that speed will destroy the surface and then some. Even with insufficient acceleration and fragmentation it could still cross the "destroy everything" threshold, or if not then still the "mass devastation" threshold.

This actually taking place is, I admit, unlikely. We are however talking about the destruction of all life on Earth, and thus any non-zero chance of such is something to be concerned about.

Any impact would just turn the thing into plasma, which dissipates. Also, since change adds up in space, a single detonation might be enough to nudge it out of the way. That is assuming for some reason somebody managed to wrestle crontrol the ship, and managed to keep it for more than 3 years. Besides, you didn't give any calculations, just some wrong numbers. How a 4000 ton ship can weight 3,628,740 kg escapes me, for one.

Besides, the notion of a 4000 ton spaceship flying at 0.1 lightspeed is just plain ridiculous. A 4000 ton spaceship requires enormous amounts of power, even so that it can destroy the Earth at much lower speeds. In fact, the kinetic energy of a spaceship that large at 0.1 c equals the pure conversion of 10 tonnes antimatter and accompagnying matter into energy. Any relativistic vessels will be much, much smaller. (Kinetic energy is about 3*10²¹. or about 6 times the annual energy consumption of Earth)

As for the change of this happen, better start wearing tinfoil hats against gamma ray bursts. The odds of this every happening are about as large as that ever working. Really, if you have acces to that amount of energy.

Note: Forum loves eating my calculations.
Note 2: I used  Newtonian calculations which means the energy needed is actually  higher.

[GlyphGryph]

Meteors usually hit us at about the third the speed we're discussing here. Meteors with a payload of 20-30 megatons or more are not all that uncommon (every couple thousand years). So half a tsar bomb there.

And those tend to never reach the ground, and thus do minimal damage - they explode upon impact with the atmosphere at those speeds and weights. Perhaps enough to destroy a city, but not much more than that.

I'm not sure what the vehicle you're describing would actually do - I imagine it certainly wouldn't strike the earth at a single point, though. 72k Tsar Bombs exploding in the earths upper atmosphere probably wouldn't be pretty, of course, but I'm not actually sure what the result would be.

[10ebbor10]

I gave you the force calculations. That much mass moving at that speed will destroy the surface and then some. Even with insufficient acceleration and fragmentation it could still cross the "destroy everything" threshold, or if not then still the "mass devastation" threshold.

This actually taking place is, I admit, unlikely. We are however talking about the destruction of all life on Earth, and thus any non-zero chance of such is something to be concerned about.

How a 4000 ton ship can weight 3,628,740 kg escapes me, for one.

IIRC, 1 ton=approx. 1000Kg
4000X1000=4,000,000

if anything, it may be an underestimation.

Pretty sure it isn't. Probably using the wrong unit, or something.
Besides, a ton is exactly 1000 kg.

[lemon10]

A ton is exactly 2000 pounds, which is ~900 kg.

[10ebbor10]

My bad. Confused american or imperial tons with the Metric Tonne, which is exactly 1000 kg.

Then again, I'm pretty sure wikipedia uses the metric system, and not the Imperial one.

@ above. I knew that, just got some unit confusion. Bloody people not being able to stick to one unit system.

Edit: Not my bad. I checked the article, and it does indeed use metric tonnes, which are equal to exactly 1000 kg. When In doubt, always use the metric system.

[lemon10]

The fact that there are like three types of ton(nes), (short, long, metric) kind of pisses me off, just come up with a different name for all of them already, it would be like having a imperial kilogram just to confuse people.

While the default is usually metric, the default unit for ton is imperial.

EDIT:
Something moving that fast and that large would be a really good weapon though (although increasing the speed and making it smaller would probably be better). It would be very hard to stop (with anything near our level of technology at least), probably fairly hard to detect (since it would be moving so fast), and deal an massive amount of damage, it wouldn't damage the physical planet that much, but it would easily cause a extinction event, and kill off the majority of humans without a real problem.

I don't think we could damage it with our current level of technology, by the time we notice it, it would probably hit us in less then two days (since I don't think we would notice it much before pluto).
Traveling from the moon would take it 10 seconds, and we couldn't conceivable get anything farther then that without years of planning (which we wouldn't have). That means that we would only ever get a single chance at it.
You also have a pretty slim chance of hitting it, its going very fast, and space is so huge that even a 4000 ton spaceship would be immensely hard to hit, especially when its going so fast.
Now, how much damage a missile could do depends on its configuration, but I think that if it was being used as a weapon (otherwise you wouldn't aim it directly at a planet and have it go .1 of light speed), it would be purposely hard to destroy, having it be long, with fairly thin walls (so a projectile would just punch through), and no atmosphere inside (so nothing would rip it up and destroy the ship with it).
Even if you hit it with a nuclear missile, you wouldn't do much damage, the missile would just punch a hole straight through, and it would already have escaped the explosion by the time it went off.
That said, if the missile did hit there is a reasonable chance that it would get nudged off course and miss the planet.

[lemon10]

If it was resting perfectly in its path (which is possible, although a bit iffy given that we would need to perfectly calculate its trajectory) it would, but even that might be a bit hard.
Intercepting it with a moving object would probably be impossible.

I don't think a missile would even do very much damage though, since it would run through the explosion before it could have any impact, a large rock would probably be a better obstacle.

That said, we might be able to stop it if we detected it a few years early, but we don't currently have the infrastructure necessary to even stop a regular meteorite, much less something that is moving so fast that we would only have a day (and possibly far less) to react.

Hell, they could probably have it slingshot around mars, changing the angle by a infinitesimal amount, but enough that it would throw off all the calculations.