Drop my dinosaur-killer asteroid on a city.

[David Evil Overlord]

Just what it says on the tin.

A super villain has set an asteroid on a collision course with a city. It's the fine details that concern me.

I Googled How Fast Do Asteroids Go?, and found a (Science fact, not fiction) story about a plan to land astronauts on an asteroid (asteroid-nauts?) travelling at 280,000 miles per hour.

Converting that to kilometres gave me 450,616.32 kilometres per hour.

Multiplying by 24 hrs = 10,814,791.68 kilometres

Multiplying that by 1 week = 168 hours = 1,816,885,002.24 kilometres

Googling what the hell was that far from earth got me the answer that Saturn can be as much as 1.7 billion kilometres.

So, if I want to give my heroes a week to save the world, the asteroid is coming in from beyond Saturn.

And takes a week to get here.

Our space probes that have gone that far have taken years (although Voyager 1 is travelling at only 35,000 mph, or 56,327 kph).

So, the question is: are my calculations completely messed up, or could an asteroid really cover that distance in a week. Assume the 280,000 mph/450,616.32 kph speed.

 

[psychotick]

Hi,

Asteroids travel at widely varying speeds. From memory the one that just passed between the Earth and the Moon late last year was travelling at around thirty thousand miles per hour.

I'd also remember that your asteroidnauts don't actually have to travel that fast to stop, divert, destroy the asteroid unless they're actually going to try and land on it a la Armageddon. Think rocket launchers and fighter jets. Only a very few rocket launchers are capable of firing rockets that can destroy a jet moving at supersonic speed by chasing it. All of them can destroy that same jet by aiming at it when it's coming straight at them.

Cheers, Greg.

 

[psychotick]

Hi,

Also your calculations are messed up. If you're right about the asteroid travelling at 10.8 million kms in a day, than in a week it would travel seven times that far, not 168 times that far - or 75.6 million kms, not 1.8 billion kms.

Cheers, Greg.

 

[Venusian Broon]

The article is actually a bit confused as to whether it is 280,000 mph or 28,000 mph - A bit more research on the object reveals in fact that it is a very close earth-like orbit: http://science.nasa.gov/science-news/science-at-nasa/2000/ast06nov_2/. Which makes me think that the 280,000 is a typo. Such a speed should make such an object spiral into the sun.

This article ( http://www.brighthub.com/science/space/articles/64710.aspx) states that asteroids have an average speed of 25 km/sec (or 90,000 km/hour) But that must be some sort of average of orbital speeds around the sun. For example Mercury scoots around the sun at close to 48km/sec (172,800 km/hour) keep it in its orbit. Here's the full set (unfortunately the graph is in miles/second so beware!):

28,000 mph or 7.7 miles per second seems slow for such an earth-like orbit, so again it must be some sort of relative speed with respect to the Earth. Just to complicate things. Sorry!


My understanding of the nomenclature of objects in the solar system is a bit ropey - but generally asteroids seem to be dwarf planets and most of the small fragments and bodies of material within the orbit of Jupiter. An object that comes in from Saturn and strikes the earth would probably be described as a comet - but then in your WiP it might indeed be an asteroid that someone evil has piloted into a crash course (a Trans-Neptunian object say?).

The difficulty now is that to get an object from that far out you will have to take a very elongated comet-like orbit to get something from outside in - so that actual 'straight-line' speed varies enormously. For example the fastest known objects in the solar system are reputedly Krentz family comets - see here:

http://physics.stackexchange.com/qu...f-the-fastest-moving-body-in-our-solar-system

Such comets apparently go at a whopping 536 m/s (1.9 million km/hr) at the point of perihelion. As the comet goes back into the wilds of the outer Solar system its velocity will drop off dramatically.

This would be the same for your asteroid piloted to hit the Earth - it will speed up as it approaches which means you can't really do a simple 'straight line velocity' calculation. I haven't done the calcs on a comet-like path but my guess, off the top of my head is that you'd probably have many weeks, maybe even a few months. (Depending on when you spot it of course and it's orbital mechanics!)

That still seems fast - but think of natural comets, such as Halleys, usually only visible in the sky for a couple of weeks as it whizzes past.

 

[Juliana]

My head hurts. Note to self: never write about colliding asteroids.

 

[Verse]

I don't know if this helps but it's an impact calculator.

For example, a 1Km diameter Ateroid impact at a 45 degree angle and velocity of 17km/s hitting rock (a city) will produce an explosion equivalent to 1.45 x 105 MegaTons of TNT.

At 100Km away from the impact anyone out in the open will get 3rd degree burns, their cloths (and anything flamable) will ignite and if that don't get you, the seismic shock equivalent of 8.1 on the richter scale will bring down anything not up to code.

http://impact.ese.ic.ac.uk/ImpactEffects/

 

[Ray McCarthy]

A super villain has set an asteroid on a collision course with a city

The largest Hydrogen bomb ever designed was downscaled for test. If it was dropped on London, London would be glass. Most of Birmingham and Manchester would be destroyed.

A Dinosaur "extincting" asteroid would result in maybe 90% of people WORLD WIDE dying from hunger and solve Global warming. Good chance of Ice age. There would pretty sunsets for years due to dust and earthquakes over an area maybe 500km wide. Depends on size.

So, you don't actually have to hit the city to kill everyone. There would be gamma ray bursts etc from the impact, so apart from blast damage and burns there would be radiation damage.

The last Galactic Conference banned deliberate "dropping" of asteroids on any planet with a biosphere.

 

[David Evil Overlord]

*Redoes calculations, using that Impact Calculator Verse supplied*

 

[Mirannan]

Maximum speed for a comet that is part of the Solar System in the neighbourhood of Earth is around 40 miles/sec or 64km/s. Asteroids are rather slower, if only because they aren't falling in as far as comets do.

There is a remote possibility of an interstellar comet coming in, and that could be coming in a lot faster; for reference, the orbital velocity of the Sun in its orbit around the galaxy is about 220 km/sec so interstellar objects could be coming in at anything up to about 500km/s. However, the likelihood of such an object coming in even as close as Neptune is tiny. Even the outer solar system is a tiny target on an interstellar scale.

 

[ralphkern]

How has your super-villain sourced the asteroid?

Has it already been placed in orbit somehow - maybe by one of the missions that has been proposed to 'capture' an asteroid and bring it to Earth or moon orbit?

http://www.nasa.gov/content/what-is-nasa-s-asteroid-redirect-mission/#.VMx48C7aKlc

If so you would have a lot more room to play with the figures. The super villain might have strapped a rocket/bomb/gizmo on the side of the asteroid and is going to activate it in one week. That will then deorbit the rock.

Also gives the brave adventurers the time to go up and disarm the device.

 

[Avid Scifi Fan]

Like Ralphkern said.

You could go with the point the villian has alread "captured" the asteroid and is in control of it with some sort of attachable rocket engines. Keep in mind as rediculous as that may sound at first, when put to scale it would be plausable. To destroy the city or just cause severe damage, the rock would only have to be about the size of a bus (bigger would do more damage, but harder to move and control). It could be nearby, maybe orbiting the moon in a holding pattern of sorts while he waits for his moment to come.

Depening on the realism of your story, you may not need to get into the details. Other details to consider would be how do the good guys remove the threat. Blowing it up only works for small rocks (this migt fit into this catagory). If it gets too large, blowing it up only causes more fragments and would make it more like a blast from a shotgun (not very helpful). In that case you would need to go with a diversionary technique.

Also, How do you stop the villian from simply getting another rock to try again?

 

[Ray McCarthy]

Cf. The Moon is a Harsh Mistress

 

[jastius]

couldn't they reorbit the asteroid? it would make an excellent secret hideout..

 

[David Evil Overlord]

maybe. hmmmmm.