Let down by solar panels

[Bill Wright]

This sounds like my dad when he lets go of his zimmer.

Bill

[Tim Lamb]

Yes. I'm no physicist but surely such an object can be rotating in more than one plane?

Yes. I was trying to be succinct:-)

>

[Tim Streater]

You can't take away Earth's gravity, which acts out to infinity in all directions. Mind you, it may not be large enough to affect the issue here. The comet is of course subject to the gravity of the Sun and Jupiter, large bodies, amongst others. However that may not be enough to affect the rotation of the comet, even though it has a *very* odd shape.

But this can happen, see f'rinstance:

for a (rare) example of a tumbling moon. Asteroids, apparently, do it more frequently:

[Tim w]

[re Rosetta Lander]

Most stupid post of the year so far?

Tim W

[Cursitor Doom]

3.7 AU more like at present, IIRC. Still relatively close, though.

[Cursitor Doom]

It would be insignificant compared to the vast amount of radioactive crap Fukishima has released.

[tony sayer]

Not at all, one day we might need to do just that to try to shove it out of the way before it does us damage...

[Tim Streater]

New Horizons (launch 2006) going to Pluto uses Pu-238. Basically, anything going to Jupiter or beyond will be unable to use solar panels.

Dawn (on its way to Ceres, in the asteroid belt, just inside Jupiter's orbit) uses solar panels, and they are quite large.

[The Natural Philosopher]

No. Its actually spot on. Solar and nuclear are the two most popular choices for remote satellite power

[The Natural Philosopher]

I think the point is here Tim, that you have forgotten basic mechanics.

Any object will have angular momentum preserved about its centre of gravity.

So until it starts burning off stuff its mass and C of G will be preserved.

As will its rotational centre and period.

[The Natural Philosopher]

Actually it would be comparable. I.e. a tiny amount and no threat to anyone

[polygonum]

If that did happen, would we still be happy to rely on solar panels? Or would we bite the bullet and accept a nuclear powered device of some sort?

[Tim Streater]

Apparently not. See the links I posted before:

although it turns out I was wrong to relate tumbling with the odd shape of an object.

[The Natural Philosopher]

"Hyperion is unique among the large moons in that it is very irregularly shaped, has a fairly eccentric orbit, *and is near a much larger moon, Titan*. These factors combine to restrict the set of conditions under which a stable rotation is possible."

Which doesnt apply to this comet.

Largely irrelevant, since its not about the same thing

[Dave Liquorice]

objects

Jupiter plays with comet CG fairly often and radically alters it's orbit and obviously the sun is controling it as well as it's in orbit around the sun.

Yeah but that is in orbit around Saturn, so by definition very much influenced by Saturns gravity and probably the other moons.

That's interesting the tiny forces from distant planets the sun etc damping out any inital tumble given enough time. That's time on geological scales not the blink of eye of human time scales. Of course a collison could leave the bits tumbling but then they have had an hefty external force applied to them.

[Dave Liquorice]

hopefully

If we have what 10 or 20 years notice of the possible collision. The time taken getting there is a serious problem. Hasn't there been some talk of (space based?) lasers to nudge a threatening asteroid off course? It doesn't take much of nudge over a longish period of time to alter the asteroids orbit enough to miss.

Still need a fair bit of warning though and the count of "potentially hazardous asteriods"(*) is constantly creeping up. We are spotting smaller things all the time, frequently *after* closest approach or not spotting them at all, Chelyabinsk...

(*) > 100m across that come closer than 0.05 AU (around 4.6 million miles).

[whisky-dave]

I'd have thought using wind power would be the most stupid suggestion ;-)

[Mary Fisher]

It's John HUMPHRYS

- Just so that I'm not missed ...

[Phil]

You're not the only one, Pallab's ill-considered dialogue was heavily edited to remove that by lunchtime when I heard it next....

[RobertL]

yes I heard that as well. It was not clear to me if the interviewer realised what he had said. The interviewee clearly grasped the full double meaning and said something like "well, that's an interesting way of putting it".

Robert