Thursday, December 18, 2008

The B612 Foundation Works With JPL To Answer The Question:

Can we stop an asteroid from causing irreparable damage to planet earth using a Gravity Tractor?

The folks at the B612 Foundation have hired the Jet Propulsion Laboratory to use their advanced computer simulations to determine if a gravity tractor can significantly alter the course of a medium size asteroid enough so that it misses the "keyhole" -the "small region slightly further from the Earth than the resonance line per se, which would, should the asteroid pass through it result in an impact at the time of the resonant return."

B612 Foundation
760 Fifth Street East
Sonoma, CA 95476
24 September, 2008
Summary Statement by B612 Foundation regarding its contract with JPL to conduct a detailed performance analysis of a transponder equipped Gravity Tractor spacecraft.
A successful NEO deflection campaign will involve several key functional elements, including the ability to, in situ, precisely determine the orbit of a threatening NEO prior to and post deflection, and to precisely adjust the NEO’s orbit to assure its successful passage between return keyholes at the time of its closest approach to Earth. B612’s contract with JPL called on it to quantify these two critical capabilities. The analysis verified the viability of the transponder-Gravity Tractor (t-GT) spacecraft to perform these critical deflection functions. A full report of this work is now available on the B612 website at, #18.

The full report from JPL is available here, and here are some highlights from their conclusions:

1.5 Study Conclusions

1. This study has shown that a relatively simple and robust thrust control law can keep a gravity tractor spacecraft in close proximity to the station-keeping location required to effectively tow an irregularly shaped, rotating near-Earth asteroid. For our test case, the spacecraft could be kept within a 20 x 50 x 50 meter box at a nominal distance of 155 meters from the asteroid’s center-of-mass for a total translational ΔV monthly cost of 40 - 45 m/s with a corresponding monthly fuel consumption of only ~ 1.4 kg.
16. A gravity tractor could be useful for the possible case in which a primary deflection technique such as a kinetic impactor happens to move the asteroid trajectory into a keyhole; the gravity tractor could shift the asteroid’s trajectory enough to miss a secondary impact keyhole. At the same time, tracking of the gravity tractor spacecraft could provide precision orbit information for the asteroid before and after the primary deflection attempt and after the gravity tractor trim maneuver.
17. While the gravity tractor in our simulation example was a viable method for towing the asteroid away from the 2049 keyhole, and hence avoiding a 2054 Earth collision, there might be other impacting scenarios for which it would not be viable. Each threat scenario would have to be analyzed individually to determine whether a gravity tractor could be used to move an asteroid trajectory away from a keyhole.

Additional general study conclusions include the following:

• The most threatening NEAs are those on Earth similar orbits.
• Simulations show that most actual Earth impactor discoveries surpass 99% impact probability very early in the second optical apparition – or after optical and radar data are obtained during the discovery apparition.
• The primary deflection techniques (e.g., kinetic energy impactor) provide relatively uncertain amounts of deflection (e.g., the momentum multiplier β is unknown)
• Secondary impact possibilities (keyholes) must be carefully examined for each specific case.
• Determining potential keyholes during Earth encounters and determining optimal times for tractoring to avoid a keyhole passage requires fully perturbed, non-linear numerical analysis (two-body analyses do not suffice).
• The combination of radiometric tracking of a nearby spacecraft with optical imaging of the asteroid from the spacecraft is sufficient to significantly improve knowledge of an asteroid’s orbit. It is not necessary to place a transponder on the surface of the asteroid to achieve precise asteroid tracking.
• The asteroid orbit accuracy improvements provided by the spacecraft range from factors of 2 to 5 over the knowledge which can be obtained using only Earth-based observations of the asteroid. The size of the improvement is dependent on the relative viewing geometry and hence the time period over which the spacecraft is tracked.
• The amount of time it takes to realize these improvements in the knowledge of the asteroid’s ephemeris is measured in days to weeks. A spacecraft need not be in place for months or years for the improvements to take place.
• A close flyby, such as the one that occurs in 2046 for this scenario can magnify the asteroid’s position uncertainty for subsequent flybys by a large factor.

In review, it appears that we have the technology available to prevent a catastrophic impact provided we have the time to track and analyze the threat years before potential impact. What this should emphasize more is the reality that the kinetic energy that will be necessary to prevent an immediate impact -say, a threat that will hit in a year or less- is not available or even being considered at the present time. And more disturbing is the fact that this is not a bigger part of the budget at NASA.

I'm afraid that when this does become an issue, the time we've lost engineering a solution to this problem will become insurmountable. JPL and the B612 Foundation make me a little less concerned, but we still need to be aware of our shortcomings.

Wednesday, December 10, 2008

"Stupidity Is Not Necessarily Unconstitutional"

So says Judge John E. Jones III, the George W. Bush appointee who presided over the 2005 Intelligent design trial, Kitzmiller v. Dover Area School District in Dover, Pennsylvania. This was the trial that essentially sunk any chance of allowing creationism to be taught as an alternative to evolution in public school science classes from a constitutional standpoint.

Via Charles Johnson at LGF, here's a neat video of a presentation and Q & A session with Judge Jones at Case Western University. His main point throughout is the sorry state of civics education in the public realm, and that he hopes trials like this will remind people about the elegant genius that is our US Constitution.

Also, be careful who you elect to your school board.

Monday, December 08, 2008

The Tennessee Titans Meet Their First Goal of the 2008 Season

Jeff Fisher, in his usual no nonsense manner, explained what that was at yesterdays postgame press conference after the Titans waxing of the Cleveland Browns to clinch the AFC South title:

"It's a rewarding feeling; our goal was to -when we left the playoff game in San Diego [last season] the day we came back was to have a home playoff game here, this year. That was our first goal, first and foremost. We have now guaranteed that. So now we move on to the next step."

One of the things I like about this Titans team this year is that they have the mentality of the underdog, the disrespected, the backwoods nobodies, the chip on the shoulder that many championship teams have taken all the way to the top. Take the NY Giants last year. They were given zero chance to beat the 18-0 (at the time) Patriots in the super bowl, but they pulled it out. The Red Sox and Patriot teams from the last few years have changed from that scrappy underdog in to the team people are tired of seeing win all the time.

I've watched the Titans since they arrived in Nashville, and I was recently reviewing an old preview post from the year they finally blew up the Super Bowl team cap space and the resulting damage was a 4-12 season.

Titans still look to make another run next year. McNair appears to be ready to rock- his annual off season surgery appears to have gone well. I can't imagine why he would appear in the NFL "Annie-Tomorrow" commercial if he didn't plan on returning. And we still have some young guns upcoming in Chris Brown, Tory Fleming and Ben Troupe. Add in the offensive genius of one Norm Chow, former offensive coordinator for the USC Trojans, as well as Ray Sherman as the new Wide Receivers coach, and all certainly does not appear lost. On the defensive side, check out this interview with Jim Schwartz, the defensive co-ordinator who after a 5-11 season last year seems pretty fired up about the upcoming one.

Yep. My enthusiasm that year was not exactly justified. The 4-12 year, that was rock bottom. Consider the price paid. Minus about three guys from that squad we give you your 2008 Titans. It's pretty much an entirely rebuilt team around franchise guys like Haynesworth and Bulluck.

Despite being second in scoring in the AFC, this Titans team won't exactly light up the highlight real. There are however, several very good reasons they have only lost ONE GAME ALL SEASON. And I believe that we will continue to see more reasons as they progress. But for now, I'll take 12-1 and the AFC South title for a guaranteed home playoff game.