Asteroid to destroy Earth...do we stand a chance

[spacefire]

since the nukes can only reach that far out of the Earth's atmosphere, the sequence of explosions will have to occur in a very short time.<br />Lots of nukes detonated one after another really fast.<br />You have to understand this is a last ditch solution...of course it might not work in all cases, like if the relative delta V component directed towards Earth is large.<br />We can ignore the fact that both bodies orbit the Sun for now, we might as well consider Earth stationary during the flyby, that is, assume that we are in an inertial reference frame. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[spacefire]

main problem is, I believe you got close to that, with the location of the nukes. They would have to be able to reach the asteroid.<br />I don't know what percentage of the ICBMs remainingh are mobile.<br /> <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[bpfeifer]

“Yes, and of course the further problem of International cooperation. Placing such capable Lasers into orbit will immediately raise a great deal of suspicion among a whole range of nations, inasmuch as they could equally be utilized against ground targets.”<br /><br />You are absolutely correct that as soon as we propose launching giant lasers or nuclear warheads (there are treaties that prohibit the latter), there will be screams of protest from many nations as well as concerned citizens. The current plans do not call for putting such devices into orbit. Rather they are launched only as needed. <br /><br />In the case of laser deflection, they expect to identify a hazardous rock years before our date with oblivion. They do the deflection work on an orbit prior to the one that will strike the earth. This requires even less dv than dealing with an imminent threat. Of course, if a rock comes at us with no prior warning…<br /> <div class="Discussion_UserSignature"> Brian J. Pfeifer http://sabletower.wordpress.com<br /> The Dogsoldier Codex http://www.lulu.com/sabletower<br /> </div>

 

[mrmorris]

<font color="yellow">"since the nukes can only reach that far out of the Earth's atmosphere, the sequence of explosions will have to occur in a very short time. "</font><br /><br />Ah -- so you're advocating that ICBMs be used essentially unchanged to deflect the asteroid in the final few seconds/minutes before impact. My assumption was that we were putting existing nuclear warheads on more capable boosters *designed* to intercept asteroids and alter their orbit before they approach *that* close to Earth.<br /><br />Given that change in paradigms -- I would have to say... no flipping way. I'm not going to get deep into it -- in fact, I'm not even going to bother looking up calculations on the dv involved. Just consider this -- the ICBMS only get to ~1200 km. At 1200 km -- the asteroid is already experiencing close to 1g of acceleration toward Earth. Therefore, at this tiny separation, the explosions of the ICBMs have to negate the dv caused by gravity before they can even <b>begin</b> to generate dv away from Earth.<br /><br />Let's consider a reasonably small asteroid of 200m across. Considering it a sphere of diameter 200m gives it a volume of 4,188,800 m3. I grabbed density values for asteroids from here of ~1.3 g/cm3. 4,188,800 m3 is 4,188,800,000,000 cm3. This would give the asteroid a mass of 5,445,440,000 kg. If the asteroid were simply sitting motionless in space -- with *no* velocity vector towards the Earth, we would need 5,445,440,000 kg of thrust simply to keep it from falling to Earth. The F-1 engines for Saturn produced 3,946,607 kilogram-force, so we'd only need the equivalent force of about 1,380 of them to do this.<br /><br />I say again -- no flipping way.

 

[oscar1]

But how would that 200m asteroid come to sit 'motionless'? What force would have been involved?

 

[spacefire]

<br />Due to the difference in speeds between the bodies, the main cause of a potential impact would be the coincidence in solar orbits rather than Earth 'capturing' the asteroid.<br />My approach assumes that the velocity component bringing the two together is relatively small.<br />Plus, gravitational attraction decreases with distance and during the transit it will not have time to make much of an impact, no pun intended. <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[mrmorris]

<font color="yellow">"But how would that 200m asteroid come to sit 'motionless'? "</font><br /><br />I didn't indicate it would sit motionless -- I said "if". Perhaps I should have said "Even if" to make the concept clearer. Essentially, I was indicating that even if we assume that there is <b>no existing velocity component</b> towards Earth to overcome -- gravitic attraction alone between the ateroid and Earth at that point constitutes an enormous dv to overcome.<br /><br /> Essentially, the problem is that by the time the asteroid is that close -- there's nothing to be done except put your head between your legs and kiss your posterior goodbye.

 

[oscar1]

Next question: What excersise does one have to do to lead up to eventually being able to kiss like that? <img src="/images/icons/wink.gif" />

 

[mrmorris]

<font color="yellow">"... the main cause of a potential impact would be the coincidence in solar orbits...</font><br /><br />I agree. I discussed that earlier -- you said to ignore the issue of solar orbits.<br /><br /><font color="yellow">"...velocity component bringing the two together is relatively small."</font><br /><br />OK -- this, taken with the above is indicating that the two are in reasonably similar heliocentric orbits which means their orbital velocities are within a few percent of each other. The asteroid can't be an a similar orbit to Earth's *and* whip right on past the planet in a couple of seconds. If it's moving that much faster than Earth -- it'd be in a much higher solar orbit.<br /><br />I also gave figures assuming *no* velocity towards Earth. If you prefer -- rather than sitting motionless -- at closest approach, we can theorize that the asteroid would simply be moving parallel with Earth at 1200km and if we could hit the big red switch that turned off Earth's gravity field -- the asteroid would simply pass right on by. Except there's no big red switch and that attraction exists.<br /><br /><font color="yellow">"Plus, gravitational attraction decreases with distance"</font><br /><br />The formula for gravitational attaction is: Fg = (G ma * mb) r2<br /><br />Written out, the gravitational force is equal to the gravitational constant times the mass of object 'a' times the mass of object 'b' -- the result of which is divided by the distance in meters between the centers of the two objects.<br /><br />Now -- for this example -- we can actually simplify the equation. The value of (G ma * mb) is going to remain unchanged. We know that the asteroid would be experiencing 1G of attraction if it were sitting at sea level. The question is what fraction of G will it be experiencing at 1200km. So at sea level the earth's radius is 6378 km, our simplified fun

 

[mrmorris]

<font color="yellow">"What excersise does one have to do ..."</font><br /><br />Take up yoga... but don't wait until the last minute.

 

[spacefire]

we can ignore the sun and just assume that the asteroid and Earth are the only objects in the universe, the asteroid zipping by Earth really fast. The tangential component of velocity is big, the radial (towards Earth), is small but if we don't do anything about it is bound to smash the asteroid into Earth, accounting for Earth's gravitational field.<br />I hope you agree with the above simplifications.<br />The relative velocity can be big or small, even if the asteroid is in the elliptical plane also, I thought TRojans have highly ellpitical orbits.<br />My defense of course is limited to objects witha high tangential velocity and small radial velocity, that is objects that would 'glance' rather than smack right into earth.<br /><br /><br /> <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[oscar1]

Thanks, I'll start first thing in the morning!

 

[barrykirk]

So, by the time the asteroid is 1200Km out, it will have been accelerated by the earth's gravitational field to close to escape velocity.<br /><br />If the direction of the velocity vector is tangential to the earth we have a near miss. Otherwise we get an impact.<br /><br />So, really we don't have to change the magnitude of the velocity vector just adjust it's direction.<br /><br />If the velocity vector is pointing directly at the center of the earth, we are kissing our posterior goodbye.<br /><br />If it is close to tangential then a nuke might be able to change a grazing hit into a miss.<br /><br />Of course the further out you hit the asteroid, the less of a change is required to the velocity vector to avoid impact.

 

[mrmorris]

<font color="yellow">"My defense of course is limited ..."</font><br /><br />And now we agree. Limit the ICBM defense only to those scenarios which require such an infitisimal last-minute nudge such that sending a few dozen ICBMs up to impact at ~1200 km. Then ignore entirely the fact that ICBM booster burnout is at ~200km such that by 1200 km they've been coasting ballistically for five times their powered envelope, making precision hits pretty much impossible.<br /><br />Once restricting the concept to .000037% of the possible impact scenarios -- this idea is perfect. No further arguments here. Wonderful. Ideal. Great. Fantabulous.

 

[MeteorWayne]

Folks, let's get real here.<br /><br />At 1200 km, with even a tiny asteroid, no amount of nukes is going to have any useful effect.<br /><br />The MINIMUM speed of an asteroid at that distance from gravity alone is 11 km/sec. That means you have less than 120 seconds to change the course of the asteroid. <br />Even if you do change it at all, will it miss the earth?<br />I don't think so.<br /><br />Most are travelling at least 30 km/sec.<br />That's 40 seconds to impact. Just how much of a change do you realistically think you are going to make to the path of an object weighing megatons?<br /><br />Time to take up yoga! <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[mrmorris]

<font color="yellow">"Folks, let's get real here. "</font><br /><br />Actually -- I sorta thought I was being real -- and providing the math to demonstrate it. However, it's a well-known fact that a picture is worth a thousand words. I'm not sure of the conversion factor between words and equations -- my standard conversion site doesn't appear to have that particular metric. However -- even conservatively speaking, 1000 words must be worth at <b>least</b> fifty math equations. I've only provided half a dozen or so, and we've seen two pictures now showing how ICBMs will redirect that nasty old asteroid. Therefore -- ~100 equation equivalents to my measly few. Spacefire wins. Unmodified ICBMs make great asteroid deflectors. I know when I'm beat.

 

[MeteorWayne]

Yes YOU were being real, but anyone who thinks that attempting to significantly change the orbit of an asteroid 1200 km from the earth's surface is dreaming.<br />Again, 120 seconds MAX! More likely less than 60 seconds to change path. Even with a huge delta V, the PATH is not going to change much at all.<br />Maybe if it's car sized, and is on track to skim the surface, but does it make sense to expend every nuclear device on the planet in such an attempt? What about the EMP from all those devices?<br />And what nation is going to shoot their entire nuclear arsenal on such a futile gesture?<br /><br />If it's gonna hit, it's gonna hit. If it's not, what would be the point of deflecting it?<br /><br />Any useful deflection of an asteroid must occur at least an orbit in advance of the impact so the change in velocity is a reasonable amount, and hopefully the method is one that imparts a slow steady acceleration.<br />Nukes are not such a method. Even better if it's several orbits in advance so the delta V is even more reasonable.<br /><br />I've been lurking on this thread for a while, but just reached my exasperation limit.<br /><br />Sorry <img src="/images/icons/smile.gif" /><br /><br />Wayne <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[docm]

No need to apologise <img src="/images/icons/smile.gif" /><br /><br />Asteroids are like enemies on the battlefield; get 'em while they're too far away to shoot at you. <br /><br />Rather than a large momentary impulse a weaker force applied over a long duration would work much better. This could be a solar mirror flying in a parallel path or any of the other such standoff schemes proposed, but the won't work without an early warning system.<br /><br />Enter lunar or orbiting "skywatch" type programs. The more complete our catalog of NEO's is the better.<br /><br />As for rogue comets; unless we want to deploy a ring of large ground penetrating nuclear interceptors (penetrate & fragment, hoping they disperse) inside of Neptunes orbit it's time to bend over & start kissing your posterior goodbye. <div class="Discussion_UserSignature"> </div>

 

[spacefire]

There's not much else we can do to at least 'attempt' to divert an asteroid with current technology<br /><br />here's a simulation:<br />http://astro.u-strasbg.fr/~koppen/body/NeoSim.html <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[rocketman5000]

send up a bunker busting nuke and hope to crack the asteroid into smaller peices? maybe peices that won't burrow deep into the ground and send up large quantities of dust causing a long "cold" spell?

 

[MeteorWayne]

That's not any better. A few large chunks, while maybe not as bad as an intact impactor, would still cause comparable effects. The amount of energy contained in the object (E=1/2*M*V^2) is the same<br /><br />In 120 seconds, how much of a difference would it really make? <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[rocketman5000]

admittantly not much, but by making smaller chunks you'll increase surface/mass making the % burnup of the asteroid higher

 

[MeteorWayne]

I agree, but the energy (which is the real cause of damage) does not change.<br />Same stuff, smaller pieces. Same energy. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[rocketman5000]

agreed that it is the same energy. but if you disipate the same energy over a larger area you'd create less damage. An asteroid's initial impact will creat a large amount of devastation, but the resulting climate change would be the big killer. smaller sized impacts would create a lost less dust in the atmosphere

 

[MeteorWayne]

You still have the same problem. In 1200 km, in 120 seconds, the pieces aren't going to spread out enough to count as seperate pieces <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>