Idea for orbital unit.

It's mainly a function of distance of the earth, cuz anything smaller than a moon is not gonna change much. g(cm/s^2)-0.3086*h(km) is an approximation (I make no quality claims) in my pocket ref book comes out too 8.3 m/s^2 which sounds a bit high to me, but then I looked at wiki and saw the plot.

You could use an integral to fix this, but eww... The energy method is nice for this because it only cares about the endpoints.

Ah yea i found this:

http://en.wikipedia.org/wiki/File:Earth-G-force.png
at 500km-ish g should be about 8.5 m/s^2.

using your assumptions etc i discovered that an 853 ton object would need to be dropped (i did use a g of 9,81, force of habit) from 500km height to get 1kt of energy release.

i think 853 tons is roughly what a small asteroid weighs, so it's not exactly "rod" from god


Obviously, the effects of a rod dropping and the effect of a nuke are VERY different. Nukes are usually airburst to get a lot of energy across a vast area. A rod would not have such luxuries so it would be more like a surface detonation, with effects similar to dropping a steel ball on dry sand. there wouldn't be a whole lot of deep penetration, and there would be quite some debris and stuff flung around. Most of all, however, it's a rather small impact site with certain destruction.


Interestingly, this makes RFG and Nukes not mutually exclusive: nukes would be much more AOE and RFG's are much more pinpoint (but certain destruction).

So breaking out orbital mechanics I get a maximum impact velocity of 8.06 km/s. This would involve the object coming down from 500km and scraping the surface about half an orbit later. If you need a faster impact or a higher angle of impact, you'll need to reduce your starting speed, resulting in a slower impact.

With the spec'd osmium rod, you will get ~103.3 Tons of TNT for energy That is almost 2.5x the largest conventional weapon in anyone's inventory today.

WOW, I did not expect the amount of science and maths people would put into this!
(Also kind-of cool/scary that the DoD is putting money into this)

Anyway the next thing to think of is, How would you defend against such an attack?
with nukes you can just shoot them down and destroy the detonator, turn them into dud's
but an osmium rod is already coming down at your base, what kind of defense system would stop that? I suppose as it would be a small area of damage you could just evacuate but could there be any way to send the rod off course or destroy it?

Shoot down the launcher before it fires.

How do you stop a sniper's bullet?

BULLET TIME!




(I apologize for this post)

On a completely unrelated topic; This reminds me of the RODS FROM THE GODS mod for kerbal psace program. If it was fun blowing things up in KSP, destroying bases in PA will be even better!

i dont see why you couldnt fire the object at a higer initial velocity . most metorites hit earth at anywhere from 8-20 miles/sec that would add a lot more energy to the impact wouldnt it?

well the idea behind the tungsten rods is that they have a very low surface area to weight ratio so they don't get slowed down as much from orbital re-entry. so these in theory should hit a planet alot faster than a meteorite with a much higher surface area to weight ratio.

Yeah, I don't quite see why everyone assumes these will just be 'dropped' instead of, well, fired.

And a laser for IMMA FIRIN MAH LAZOR purposes would be nice.

Here is a nice little Impact Calculator provided by Jay Melosh at Purdue University and Imperial College.

http://www.purdue.edu/impactearth

We're already talking about something more powerful than any non-nuclear weapon in current existence with just dropping it. We can stick a rocket on the back but it's not likely to make it into the equivalent of decent sized nuke. We're assuming you're starting in fairly low orbit, you don't have the distance needed to achieve really high speeds.

If you want to shoot something at really high speeds, something less massive than a osmium telephone pole would likely be better. You also are making a missile more than a rod from god.

Also assuming it's dropped you get an idea for minimum impact energy...

It can also increase or decrease depending on the electrical potential of a celestial body. Not just mass.

Rods from god would be fun and unique to this rts for sure.

That calls for a source... Because as far as I know, electric and gravitational potential energies don't interact with each other at all... A body can and usually does have both, but they operate independently given my understanding.

They operate independently, but if the planet is positively charged and the pole negatively the pole would get accelerated by the electric field, thus increasing impact power

I like this topic for all the off-topic coolness going on, but in terms of actual in-game balance, orbital artillery seems like a horrible idea.

As opposed to interplanetary artillery :?:

To get comparable effects you need to have rather huge charge differences, there will be discharges before you can get to that point (see lightning), hence why we normally just see gravity as a driving force at such large scales. You can get more mass in one place than displaced charge.

I think it would be awesome to launch missiles, or some form of projectile/explosive/whatever, at the planet surface, from orbit/a moon/an asteroid.

Or even better, lasers.
Wouldn't it be awesome that if you survive long enough, and gain enough resources, that you can construct your own space stations? I'm not sure if this is an already-thought-of thing, like the Biome concepts might be suggesting (That robot/metal looking planet?)

Cue "That's No Moon".

Also, It would be really awesome if, as we're rocketing our asteroid towards the planet, the asteroid is also firing off a series of missiles/lasers to directly target buildings that may be outside of the blast radius from the asteroid's collision.

That also brings up a question I've had on my mind for a while:
Will there be a way for players to intercept/slow down Asteroids/other objects? Such as firing off units to intercept, land on the asteroid, and take down the engines?