Like many people, I have an interest in the idea that the Earth has been the victim of a multitude of asteroid impacts, over the Eons, and might become targeted again. Unlike many people, I have looked up the orbital parameters and mass for some near-Earth asteroids and applied Kepler’s Laws to estimate what effort might be necessary to change the path of a potential Earth-impacting planetoid.
Figure 1: There was a movie about this
What I found was that it would be extremely expensive, but within the realm of possibility. Well, damn the expense! If it can be done, we would do it or suffer the consequences. I used the Cassini Saturn-orbiting probe as my example of “current technology”, which tells other Space Nerds how long ago that activity occurred.
The scenario was that we should launch a mass the size of Cassini with that probe’s velocity to collide with the asteroid – not to blast it into pieces, because that would not be nearly enough. Rather it would be to change the orbit – to delay (or advance, works either way) the arrival by one Earth radius. The idea being that when the threatening asteroid got to its intercepting point, the Earth would not yet (or no longer) be there.
Figure 2: Cassini: Now, I don’t mean to ram billion-dollar space probes into asteroids. I just used this as an example of what mass has been launched before – at what velocity.
The truth is that I don’t remember* how many “Cassini masses” would be required, but I seem to remember that it was at least 20, so we will go with that. After all (and as I pointed out at the time) Boeing would be happy to launch 20 measly rockets, just to have the “Boeing Saves the World” press coverage. That choice of Boeing* is another indicator of the age of this calculation. Today, I reckon SpaceX would be the contractor of choice. Tell me Elon Musk wouldn’t be happy to get that media coverage!
There are a lot of details that make this far more complicated than I might have led you to believe. For example, Cassini only got out to Saturn by making “slingshot” passes of Venus (twice), the Earth and Jupiter. It is actually the velocity that is the critical element and a very great deal of that was gained by those encounters. I have assumed that we learn of impending doom long before the pending event, since Cassini was launched in 1997 and arrived at Saturn in 2004.
It also took a long time to engineer the craft and develop the mission but, we imagine that development of a simple impactor would be vigorously expedited, given the circumstances. It might be better to just send a big bag of sand. And one might entertain the idea of releasing the sand from the bag just before impact to spread it out some. See, you don’t want to make a lot of fragments, since those will undoubtedly have a variety of orbits, some of which might still intersect the Earth.
One complicating problem about all this was pointed out by Carl Sagan. If I change the orbit of the asteroid and don’t do the job in “one fell swoop”, the effect is to move the location of impact, not into space, but to another location on Earth. Sagan compared this to “walking” a very large Nuclear bomb across whatever countries are between the initial impact zone and the “edge of the planet”. Carl had in mind some kind of rocket placed on the asteroid that would gradually move the impact zone. I checked that idea and it requires a lot of “rocketry” and so lots of logistics and assembly and fueling. My simple-minded “throwing rocks” (or sandbags) scenario was a lot less complicated but still not in the “one fell swoop” category.
Now, I told you all that so I could tell you this:
I am currently attending the Lunar and Planetary Science Conference. This is the 50th such conference and it is no coincidence that the moon landing was also 50 years ago. The Conference “proper” has yet to start. I have just finished the second of two sessions of what is called the Microsymposium 60 – a “preliminary” event, like the no-name band that opens for Pink Floyd*.
*Shall I just put an asterisk on these “tells” for how old I am? 
Figure 3: Lunar and Planetary Science Conference
Microsymposium 60 (Spellcheck fails miserably when they make up words like that, so I copy-and-paste these things) was all about how there is now a “Moon Rush” of private contractors and government effort to return to the moon. That sort of news is usually hyperbole*, but this time it might be different. Government will probably not come through anytime soon, but there is a moon lander by a private company that – if all goes well – will land on April 11…this year! I just learned that in Microsymposium 60.
Figure 4: Space IL Beresheet probe. This was a Lunar X-Prize entry, but the X-prize expired un-won. They went on anyway.
Other private companies have been making moon landers, too. They are ready to go and showing their wares (along with Instrument Makers) to eager planetary scientists today and throughout the Conference. In case you think these are lightweights, among the presenters were Lockheed Martin and SpaceX. Some of the lesser known companies have made equipment and whole probes before. A company called Masten has made over 600 flights, (many with landings) to date.
Figure 5: Masten
Microsymposium 60 will be the subject of yet another post (or magazine article). This post is to reveal where I am about to go listen to technical presentations for three hours this afternoon. Notice (below) that this is for “the media”. Yup, I am “credentialed” Working Press (it says so, right here on my plastic badge) for the entire Convention.
Workshop for the Media on Planetary Defense
at the 50th Lunar and Planetary Science Conference
Everything you’ve always wanted to know about near-Earth objects and planetary defense: a workshop for journalists and science writers. (that’s me! – Steve)
Sunday, March 17, 3:00 p.m. – 6:00 p.m. (4:00 p.m. EDT, GMT -5)
The Woodlands Waterway Marriott Hotel and Convention Center
Indian Springs
The workshop is free but places are limited, so registration is required.
In this three-hour workshop, experts will report on the methods and status of finding, tracking, and characterizing near-Earth objects (NEOs) and planning for planetary defense. Plenty of time will be provided for questions and discussion.
Agenda
Journalists and science writers will have an opportunity to learn about such developments as:
- Progress in ground-based optical and radar observations of near-Earth asteroids and comets.
- Advances in modeling and understanding atmospheric, land, and water impacts of NEOs.
- Current understanding of NEO characteristics.
- NASA’s Double Asteroid Redirect Test, the first mission that will demonstrate an asteroid deflection technique (the kinetic impactor).
- Functions of the Minor Planet Center, the International Asteroid Warning System, and the Space Missions Planning Advisory Group.
- The first test of the global asteroid-impact warning system and plans for a second test.
- Interagency and international cooperation on planning for planetary defense.
- The status of planning for a dedicated, space-based asteroid detection telescope.
Experts on hand will include:
- NASA Planetary Defense Officer Lindley Johnson
- NASA NEO Observations Program Manager Kelly Fast
- NASA Planetary Defense Coordination Office Program Executive Rob Landis
- NASA NEO Observations Program Scientist Michael Kelley
- University of Arizona Associate Professor, Small Bodies, Situational Awareness, Vishnu Reddy
- Near Earth Object Camera (NEOCAM) Principal Investigator Amy Mainzer, Jet Propulsion Laboratory
Hasta Luego,
Steve
GoingWalkabout.Blog 
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