Glad to see that you jumped in on this: good description.
Because the comet is so small, the gravity changes a lot with "altitude" from the surface. For a 2-km diameter sphere, say, then the difference in gravity between an altitude of 2-km and 6-km (i.e. between 4 and 8-km from the centre of the sphere) is a factor of 4. On the Earth, it barely changes at all between altitudes of 2 and 4-km, because this is a tiny change relative to the 6400-km radius of the Earth.
So, yes, at 100-km and 50-km, we'll be flying these hyperbolic arcs (slightly bent by the very weak gravity), using thrusters to "turn the corner" at the end of each leg. But at 30-km, we'll be on closed more-or-less circular orbits: I'm pretty sure that it is natural orbit though (and thus fairly long in duration), but not powered.
I do work on the project, albeit not on the flight dynamics side. One of our experts on this, Frank Budnik, did give a talk on this in the science session I moderated yesterday afternoon, starting at 11:28 into the recording of the live stream here:
http://www.esa.int/spaceinvideos/Videos/2014/08/Rosetta_at_comet_First_images_science_results
Ha
That said, there are some colleagues I tried to have volunteer to go
Our live webcast will be at www.esa.int starting at 10:00 CEST / 08:00 UT. Should be some cool new pictures of the comet to see.
(Disclaimer: I'll be one of the speakers
It sounds like this transformer had its center tap grounded and was the path to ground on one side of a ground loop as the geomagnetic field moved under pressure from a CME, inducing a common-mode current in the long-distance power line. A gas pipeline in an area of poor ground conductivity in Russia was also destroyed, it is said, resulting in 500 deaths.
One can protect against this phenomenon by use of common-mode breakers and perhaps even overheat breakers. The system will not stay up but nor will it be destroyed. This is a high-current rather than high-voltage phenomenon and thus the various methods used to dissipate lightning currents might not be effective.
In March 1989 much of Quebec lost power for the same thing.
They lost power because the common-mode breakers tripped, not because their system was actually damaged.
:-)
You make it sound like starving people are getting fat too.
If they are becoming obese, the particular individual has a surplus of caloric intake, if only for this year or month. This is not to say that they have proper nutrition. So I am not at all clear that the fact that there is obesity in the third world is confounding evidence.
Martin,
The last time I had a professional video produced, I paid $5000 for a one-minute commercial, and those were rock-bottom prices from hungry people who wanted it for their own portfolio. I doubt I could get that today. $8000 for the entire conference is really volunteer work on Gary's part.
Someone's got to pay for it. One alternative would be to get a corporate sponsor and give them a keynote, which is what so many conferences do, but that would be abandoning our editorial independence. Having Gary fund his own operation through Kickstarter without burdening the conference is what we're doing. We're really lucky we could get that.
"If I do not want others to quote me, I do not speak." -- Phil Wayne