An idea: hitting an asteroid...with an asteroid

[fredinno]

11 hours ago, Newt said:

Then the velocity of the final object will be different then either of the original ones, meaning that probably there will not be a collision with the Earth. Ideally, this is what would happen, not a messy break up.

Or it might just hit Earth anyways. This is overall, a bad idea.

[RuBisCO]

Was there not a futurama episode that basically did this, but with garbage hitting garbage?

Nukes are the best or at least most developed way we have for hypothetically moving large asteroids. Consider all the was developed fro project Orion, a nuclear warhead with a focused blast charge. Detonate those in front of an asteroid or comet would push it without necessarily blowing it apart. 

 

Edited February 1, 2016 by RuBisCO

[fredinno]

35 minutes ago, RuBisCO said:

Was there not a futurama episode that basically did this, but with garbage hitting garbage?

Nukes are the best or at least most developed way we have for hypothetically moving large asteroids. Consider all the was developed fro project Orion, a nuclear warhead with a focused blast charge. Detonate those in front of an asteroid or comet would push it without necessarily blowing it apart. 

 

You'd still have to be careful not to tear it apart. Also, you can still do this w/o Orion Drives, just stay sufficiently away during an explosion.

[AngelLestat]

22 hours ago, GeneralVeers said:

Actually, what I want is to divert its trajectory by "enough". Whether or not "a tiny bit" equates to "enough" depends entirely on how far in advance we spot the incoming bogey. That recent impact in Russia (which apparently went undetected until it went KABOOM) proves we're not very good at that last bit.

Ok. change a tiny bit by enough..

About the russian meteorite, was relative small, we have higher chances to find big ones.. but yeah.. nothing is certain. 

Quote

We won't know that until we fire some nukes (and other types of weapons) at test asteroids and actually see what happens. Until tested in the real world, every idea in this thread is a theoretical one. We really need to avoid making the mistake they keep making in the movies, where the Anti-Asteroid-Gizmo "hasn't been tested". Because this is not the movies, and when things aren't tested, they usually don't work.

In the case of nukes we might need some testing to find what method is the most effective (depth, depending asteroid class).

About hitting the asteroid with another asteroid.. you dont need much testing.. you just do it. Because you dont have to choice the moment or depth of detonation.
What it needs testing is install a nuclear reactor in an asteroid that will be able to produce water (splitted in hydrogen and oxygen) and in case it needs, it will use that water as propellant in a NTR configuration to move the asteroid. 

[55delta]

20 minutes ago, AngelLestat said:

What it needs testing is install a nuclear reactor in an asteroid that will be able to produce water (splitted in hydrogen and oxygen) and in case it needs, it will use that water as propellant in a NTR configuration to move the asteroid. 

I assume you mean mining on the asteroid you want to impact the killer asteroid. Now, I wouldn't design a mission to mine the asteroid, I'd want to bring lots (I mean LOTS) of propellant with me. But how efficient would you expect a NTR set-up to be, seeing as it would have to add velocity to compensate for the mass mined? There will be losses regardless, I understand, because conservation of energy is an eternal frustration. A trade-off of the practical (what we might have) vs the ideal, maybe?

[kerbiloid]

It's a brilliant idea and it was successfully implemented ~60 mln years ago.
Now we have a Mexican Gulf.

[AngelLestat]

9 hours ago, 55delta said:

I assume you mean mining on the asteroid you want to impact the killer asteroid. Now, I wouldn't design a mission to mine the asteroid, I'd want to bring lots (I mean LOTS) of propellant with me. But how efficient would you expect a NTR set-up to be, seeing as it would have to add velocity to compensate for the mass mined? There will be losses regardless, I understand, because conservation of energy is an eternal frustration. A trade-off of the practical (what we might have) vs the ideal, maybe?

We can have 1000 isp with NTR.
But why you want that?  it has a lot of drawbacks vs my alternative...

Imagine you want to move an asteroid of 22m of diameter (mostly water), that is around 10000 tons, now you can calculate how much fuel you need to bring with you to push that asteroid with a certain deltav (100t of fuel only is enough to achieve 100m/s)
But first you need to launch that from earth and reach the asteroid, which takes precious time and extra fuel, plus difficult maneuvers with high delay in communications in a very unstable asteroid due its size).

with my way: you have all the time in the world to choose the perfect asteroid to capture. Once you reach it (the same 22m asteroid) you paint it with a reflective layer, surface=2000m2 which is 45x45 (200 kg of paint as much).
You push it in the best moment to achieve an earth encounter (it might take 4 years, it does not matter), once there you use gravity assist from the moon and then earth to capture the asteroid in a very highly elliptic orbit (it takes less deltav to capture and less deltav to reach escape velocity using oberth effect) 
Once in orbit.. you can study it, then you drill it to the center, and use a nuclear reactor to melt its core filtering the water, the same heat can be used to split the water and produce lh2-lox.
A long retractable cable can be used to catapult probes to reach escape velocity even before achieve circularization, this reduce a little bit the apo from the asteroid.

The day that the asteroid menace arrive, you have hundreds of tones of propellant in orbit and you can use the same reactor as NTR engine.
Lets imagine that after minging and exploit the asteroid you have a mass of 6000t, you can use 2000t of the asteroid as proppelent to achieve 4000m/s and hit the menace with a mass of 4000t.
The time you save with the extra deltav increase by a lot the divert angle you can achieve.
 

[fredinno]

3 hours ago, AngelLestat said:

We can have 1000 isp with NTR.
But why you want that?  it has a lot of drawbacks vs my alternative...

Imagine you want to move an asteroid of 22m of diameter (mostly water), that is around 10000 tons, now you can calculate how much fuel you need to bring with you to push that asteroid with a certain deltav (100t of fuel only is enough to achieve 100m/s)
But first you need to launch that from earth and reach the asteroid, which takes precious time and extra fuel, plus difficult maneuvers with high delay in communications in a very unstable asteroid due its size).

with my way: you have all the time in the world to choose the perfect asteroid to capture. Once you reach it (the same 22m asteroid) you paint it with a reflective layer, surface=2000m2 which is 45x45 (200 kg of paint as much).
You push it in the best moment to achieve an earth encounter (it might take 4 years, it does not matter), once there you use gravity assist from the moon and then earth to capture the asteroid in a very highly elliptic orbit (it takes less deltav to capture and less deltav to reach escape velocity using oberth effect) 
Once in orbit.. you can study it, then you drill it to the center, and use a nuclear reactor to melt its core filtering the water, the same heat can be used to split the water and produce lh2-lox.
A long retractable cable can be used to catapult probes to reach escape velocity even before achieve circularization, this reduce a little bit the apo from the asteroid.

The day that the asteroid menace arrive, you have hundreds of tones of propellant in orbit and you can use the same reactor as NTR engine.
Lets imagine that after minging and exploit the asteroid you have a mass of 6000t, you can use 2000t of the asteroid as proppelent to achieve 4000m/s and hit the menace with a mass of 4000t.
The time you save with the extra deltav increase by a lot the divert angle you can achieve.
 

Umm.... That's not have gravity assists work. And I doubt Lunar Gravity assist would be enough, usually, that provides around 500m/s at best.