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NEO News - Rusty Schweickart on Asteroid Deflection Technology

Status Report From: Ames Research Center
Posted: Thursday, September 2, 2004

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Open Letter to the NEO Community from Erice
Rusty Schweickart, Chairman, B612 Foundation
2 September 2004

I have just returned from Erice, Italy, which lies on a mountaintop at the northwest corner of Sicily. Erice is a major center for the World Federation of Scientists, the background of which you can explore at http://www.federationofscientists.org. (be aware that the website is not current) From 18-26 August, 2004 the attendees participated in the International Seminars on Planetary Emergencies and Associated Meetings. The "Associated Meetings" were primarily meetings of the so called "Permanent Monitoring Panels" (PMPs) for many of the subjects covered in the meetings. The range of issues covered in the plenary sessions of the seminars included migration, bio-safety/bio-security, brain diseases, energy, climatology, information security, and cosmic objects.

I am writing this letter in order to pass on to those professionally involved in the subject of near-Earth objects, information developed at the seminars which I believe to be of particular interest. I refer you to Clark Chapman's more general impressions of the event just posted on David Morrison's Impact Hazard website [http://impact.arc.nasa.gov/] as the second item of a news posting dated August 31 (Click on the 2004 News Archives if it's no longer on the homepage when you check). I will focus here on two particular items which arose in our Cosmic Objects PMP discussions which I believe are of note to the NEO community.

First, however, are listed the attendees for the Cosmic Objects plenary session and PMP discussions. While some arrived late and some left early, all took part in the bulk of the discussions.

  • Alberto Cellino and Mario Di Martino - Osservatorio Astronomico di Torino
  • Walter Huebner and Ray Goldstein - Southwest Research Institute San Antonio
  • Clark Chapman - Southwest Research Institute Boulder
  • Don Yeomans and Ali Safaeinili - NASA/JPL
  • Alan Harris - DLR Institute for Planetary Exploration
  • Hajime Yano - Department of Planetary Sciences ISAS/JAXA
  • Rusty Schweickart - B612 Foundation

1. The ICAIH The primary output from the PMP discussions, stimulated by a direct request for a specific initiative by the Chairman of the conference, Dr. Antonino Zichichi, was a proposal to create, under the World Federation of Scientists at Erice, an International Center for Asteroid Impact Hazards. This Center, envisioned as a permanent entity largely dedicated to the development and implementation of international policies related to NEO issues, is outlined in the attachment to this open letter. The attachment is an excerpt from the complete document comprising the general resolution and the detailed implementation statement for the issue of highest priority. The lower priority responsibilities were treated very lightly given our limited time and are not included here.

Everyone present felt very strongly that this proposal expressed a genuine need and could, if implemented make a substantial contribution to the development of coordinated international response in anticipation of a NEO impact. What was not at all clear, and remains so, is whether or not Prof. Zichichi and the World Federation of Scientists are willing or able to actually create such a Center. Nevertheless, as a result of the Erice meeting and the encouragement of Prof. Zichichi, the proposal for and the definition of an institutional entity to address critical international policy issues associated with future NEO impacts now exists. I felt that it was important to advise you of this development.

2. NEA characterization The second item which I felt justified wider dissemination was our fairly brief, but critical discussion on asteroid characterization. There was no recommendation on this matter, nor was there any agreement sought. The comments below primarily represent my personal concern that with respect to asteroid characterization there is, in the community of NEO researchers, a de facto assumption re asteroid deflection methodology which may limit the future availability of critical design information.

Toward the end of our PMP discussions each of the participants reported to the group on their current work. Much of the work reported dealt with very creative initiatives directed to the characterization of NEAs. From current missions underway to others awaiting critical funding, to future proposals, a wealth of knowledge will soon be produced regarding the structural characteristics of these bodies. Most of this work will characterize the seismic integrity and large scale structural character of NEAs. While we will certainly gain some knowledge of the fine scale structure I felt that attention to this aspect of asteroid characteristics was under addressed.

My concern reflects, of course, my own preference for the B612 "gentle push" methodology for asteroid deflection. (See The Asteroid Tugboat, Scientific American, November 2003, and/or www.B612Foundation.org) But this concern in fact applies to virtually all of the "soft" deflection techniques, e.g., mirror deflection, laser deflection, and the direct push recommended by B612. What I fear there is that, within the community of researchers, there exists a de facto, and perhaps sub-conscious acceptance that the "default" method for future asteroid deflection will be via the use of nuclear explosives. My sense is that, while the current asteroid characterization work is both valuable and unquestionably needed, it comes up short of the detailed surface information needed by the "soft" deflection concepts.

For example, the single most critical unknown currently facing the B612 design is how to anchor a spacecraft to the asteroid surface after landing. In particular, in order to properly deflect an asteroid we must be able to push on it, not only perpendicular to the surface, but at angles down to, and hopefully including, the local horizontal. The question then is what is the nature of the regolith? What is its cohesion? Can one anchor to it and expect that a force of several newtons parallel to the surface can be reliably applied? For the ablation techniques which count on vaporization of the surface materials the detailed thermal characteristics (and probably chemical composition) will have to be known.

While all of the current characterization work is truly commendable, I believe it is extremely important that future characterization research be broadened to include the detailed characteristics which will enable techniques other than the use of nuclear explosives or direct impact (which is of very limited effectiveness) to move ahead with valid designs. I strongly urge that those doing this critical research become familiar with current thinking in the deflection field so that we are not left in the future with the terrible situation where the only deflection technology for which adequate design information exists is nuclear explosions in space. (See, in particular, the proceedings of the Feb 04 AIAA Planetary Defense Conference, http://207.99.20.212/~planet/) We should never be placed, by a lack of accessible knowledge, into a position of having to accept the Faustian bargain of nuclear weapons standing by forever in order to assure that the world can avoid a NEO impact.

NEO News (now in its tenth year of distribution) is an informal compilation of news and opinion dealing with Near Earth Objects (NEOs) and their impacts. These opinions are the responsibility of the individual authors and do not represent the positions of NASA, the International Astronomical Union, or any other organization. To subscribe (or unsubscribe) contact dmorrison@arc.nasa.gov. For additional information, please see the website http://impact.arc.nasa.gov. If anyone wishes to copy or redistribute original material from these notes, fully or in part, please include this disclaimer.

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