@Ichinisan
@JSt0rm
@CZroe
@Hayabusa Rider
@pcgeek11
Whoa there fellas. There’s a lot to unpack here. But before we go off designing fleets of AI powered, non nuclear satellites to protect the Eastern seaboard maybe understanding exactly what the risks are, how they are currently dealt with and what could be done today.
First some fun facts about the asteroid in the article. The articles say the asteroid was moving at 54000mph relative to Earth with an impact energy potential 30 times that of the A bomb dropped on Hiroshima.
That gives an impact energy of 1.9x10^15joules or 450 KT of TNT.
Using the standard kinetic energy equation of KE = (1/2)(M)(Velocity ^2) gives us a mass of about 6400 metric tons.
So this is equivalent in destructive potential to a modern H bomb. During the 50’s and 60’s many larger bombs than 450KT were detonated above ground or underwater. 2019OK is only deadly if it hits populated areas.
For comparison the
Tunguska Event was around 10MT or 4.2X10^16 joules.
The Chicxulub Asteroid that killed the dinosaurs was over 10 miles in diameter and hit with an impact energy of 120,000,000 megatons of TNT or 5X10^23 joules. Equivalent to 260,000,000 2019OK asteroid impacts.
MITIGATION
Now did we detect it in time to do something? Doing something doesn’t have to mean deflecting it. With about two days knowledge of a populated impact you could evacuate most of the populace. (As an example 2-3 million people evacuated south east Houston and Galveston county in 48 hours before Hurricane Rita.)
With 2019OK we only had about a days notice so if it was to hit a populated area it was marginal if an evacuation would have been successful. (One should note that 70% of the Earth is uninhabited and hits on populated but rural areas probably could be evacuated in less than one day)
For deflection missions you must have years in advance. To avoid the Earth the asteroid must be deflected by between 0 and the radius of the Earth. For example if your asteroid is on a dead center collision and you’ve got 10 years to adjust its velocity you need to change its speed by about 20 mm/s to miss Earth radially. If it’s a tangential hit maybe only 1-2mm/s or less is required.
Each asteroid requires different delta V changes and vector calculations based on its trajectory and time to intercept. Because of the absolutely massive differences in delta V required to intercept asteroids from different point in the sky it’s a waste to try and have some sort of AI interceptors already in orbit. You will never be in the right orbit with the right amount of propellant to intercept the object appropriately.
Early detection is the key. 90% of large asteroids have been catalogued with emphasis on detection years or decades before impact so deflection efforts can be undertaken. Current efforts are underway to detect objects like 2019Ok that are 10m and larger days to weeks in advance so evacuations could occur. Anything smaller isn’t really a threat.
The number of objects detected steadily goes up each year.
For any asteroid detected years away the two simplest ways to change its trajectory is by impact or gravitational tug.
An impactor like the 2005 Deep impact mission where we slammed a 100KG copper mass into a comet at 10.2 kps equivalent to 4.8 tonnes of TNT would be enough to move an asteroid much larger than 2019OK over a 10 year period.
Gravitational tugs are another way. Simply put a large probe in orbit around the asteroid and they form a gravitationally bound system. Slowly change the probes orbit and the orbit of the asteroid changes as well. Over time it changes enough to miss earth. We already basically do this with probes like Hayabusa 2 and Osiris-rex.
Most of the easy objects have been found. The ones still out there are some combination of:
- Small
- Low Albedo (dark)
- Highly Elliptical Orbit
- Hyperbolic Orbit (think large fast comets with long periods from way outside the orbits of any planets)
- Approaches Earth from the direction of the Sun
What we really need to be safe is more and better ground and space telescopes to perform sky surveys and find the remaining dangerous objects. Even then the odds of something more dangerous than the Chelyabinsk meteor hitting in our lifetime is very very small.