About asteroid deflection concepts, following up on my last post I’m providing the following quotes from a March 2007 NASA report to Congress, “Near-Earth Object Survey and Deflection: Analysis of Alternatives”:
“Section 321 of the NASA Authorization Act of 2005 (Public Law No. 109-155), also known as the George E. Brown, Jr. Near-Earth Object Survey Act, directs the NASA Administrator to transmit an initial report to Congress not later than one year after the date of enactment that provides: (1) an analysis of possible alternatives that NASA may employ to carry out the survey program of near-Earth Objects (NEO), including ground- based and space-based alternatives with technical descriptions; (2) a recommended option and proposed budget to carry out the survey program pursuant to the recommended option; and (3) an analysis of possible alternatives that NASA could employ to divert an object on a likely collision course with Earth….
A study team, led by NASA’s Office of Program Analysis and Evaluation (PA&E), conducted the analysis of alternatives with inputs from several other U.S. government agencies, international organizations, and representatives of private organizations. The team developed a range of possible options from public and private sources and then analyzed their capabilities and levels of performance including development schedules and technical risks.
Key Findings for Diverting a Potentially Hazardous Object (PHO):
The study team assessed a series of approaches that could be used to divert a NEO potentially on a collision course with Earth. Nuclear explosives, as well as non-nuclear options, were assessed.
- Nuclear standoff explosions are assessed to be 10-100 times more effective than the non-nuclear alternatives analyzed in this study. Other techniques involving the surface or subsurface use of nuclear explosives may be more efficient, but they run an increased risk of fracturing the target NEO. They also carry higher development and operations risks.
- Non-nuclear kinetic impactors are the most mature approach and could be used in some deflection/mitigation scenarios, especially for NEOs that consist of a single small, solid body.
- “Slow push” mitigation techniques are the most expensive, have the lowest level of technical readiness, and their ability to both travel to and divert a threatening NEO would be limited unless mission durations of many years to decades are possible.
- 30-80 percent of potentially hazardous NEOs are in orbits that are beyond the capability of current or planned launch systems. Therefore, planetary gravity assist swingby trajectories or on-orbit assembly of modular propulsion systems may be needed to augment launch vehicle performance, if these objects need to be deflected.”
That’s the official word, circa 2007.
In 2008, the Future Concepts and Transformation Division of the U.S. Air Force hosted a “natural impact interagency deliberate planning exercise” – a tabletop exercise designed to explore how the U.S. government might respond to an impending asteroid impact with Earth. A report on this exercise, “AF/A8Xc Impact Hazard (Asteroid Strike) Interagency Deliberate Planning Exercise After Action Report,” detailed many useful insights gained from it. For example, “The public may be aware of an impending NEO impact before senior decision-makers.” This finding is all too true, and even more so today than it was in 2008. “The preferred approach for short-notice NEO deflection was stand-off nuclear.” (Dear readers, you know I have problems with nukes….) And “Players [in the exercise] were not able to achieve consensus on which [federal] agency should lead the NEO deflection/mitigation effort.” This issue is still, as far as I know, unresolved, though people are working on it.
I’m not an aerospace engineer. Nonetheless, I ask you to take my word for it, there’s nothing simple about designing a deflection mission for a potentially hazardous asteroid, let alone funding and building it. And as I indicated in my earlier post, throwing nuclear weapons into the mix will only make it more complicated. I’m hoping that among all the great minds in the aerospace community, somebody might come up with a more palatable alternative.