I’ve noticed that very few people seem to understand the concept of the Enhanced Gravity Tractor planetary defense technique that the ARM Option B approach plans on demonstrating. A friend recently forwarded me a great paper describing this concept that was presented last month in Italy at the IAA Planetary Defense Conference, that provides a good introduction to the concept:
The high level version is that by collecting mass from the target asteroid, you can enhance the diversion speed of an asteroid by 10-50x or more compared to using a normal gravity tractor without local mass augmentation. This means that even for an Asteroid Redirect Vehicle with a capture mechanism about the size Altius analyzed in its ARM BAA study, you could redirect an earth-crossing 100m class asteroid with <1yr notice, and a 150m diameter (Tunguska-class) asteroid with <2yrs.
There were a bunch of points made in the paper, but a few of the more interesting ones are:
- Because an enhanced gravity tractor works via gravity, you could use it to divert debris from an unsuccessful nuclear diversion attempt.
- You can speed up the process by putting multiple EGT spacecraft into a halo orbit around the asteroid simultaneously.
- The EGT doesn’t necessarily require boulders on the target asteroid. If the redirect spacecraft has the ability to scoop regolith for instance, you could use regolith or smaller rocks instead of a boulder extractor system.
There’s a lot more to it than that, but I wanted to put this article up there because I think most people following ARM, especially critics, could benefit from access to the article.