/is spaghettification the state of being touched by His Noodly Appendages?
//LOVE your book, Phil. I’m taking my time with this one.

On a side note – Obama might soon be announcing Gration as the head NASA chief. That decision is more epically painful than the thought exercise of having one’s iron ripped out from a Magnetar.

Fighter jock. No space experience at all. UGH UGH. Obama is basically sitting science on the kitchen bar stool and patting it on the head. And then promoting moon exploration boy to class prez.

Obama has stepped up and knocked homer after homer off the plate with science picks for his lead agencies. Then he goes with this dude? WTPH?

I learned that little factoid from one of my new favourite science based TV dramas, Breaking Bad.

Magnetar….hmmm… that might be cooler. But I do have one question about that (please remember, I’m deciding which celestial body to be chucked into so I do care about this answer).

Well, this might be the dumbest question EVA but, we have a small amount of iron in our blood right? Iron is magnetic (I think). A Magnetar has a mag field that is, well, utterly epic right? So I guess my question is, utterly suspending all disbelief of the associated problems with me flying into a Magnetar, do I also have to worry that the iron in my blood will be ripped out from the horrendous magnetic field lines of a star like that?

a question. How big has to be a black hole to kill you by blueshifted infalling starlight and background radiation just before you will be spaghettified

And I will buy your book, just got three and a half more on the bedside to get through, promised I wouldn’t buy a new one till they’re done. Well, maybe just one more…

You are exactly right, if you’re thinking like washing down your driveway with a garden hose. Remember, though, that you are resisting the thrust from the hose jet with your hand which is transferred through your body to your feet and they have enough friction against the ground to keep you from moving. For this to work in space, you’d have to somehow hold the spacecraft in place over the asteroid. You could do it with another thruster aimed the opposite direction, but that would increase your propellant requirements 100% with no increase in performance. It would be better to just land the thing with the nozzle facing up and blast away.

A thruster on a spacecraft sitting on the surface will almost certainly not be aimed through the CG of the asteroid and would cause it to rotate if it isn’t doing so already (which is also the case for the hovering thruster blasting onto the surface). A gravity tug is much more elegant. First off, it attaches, by definition, directly to the CG so it doesn’t matter if the asteroid is rotating. Secondly, chemical thrusters just aren’t efficient enough. They can produce huge amounts of thrust, but only for a short time. The total amount of impulse (thrust x time) you get for each Kg of propellants is too low to get a meaningful amount up there. A better choice is an ion thruster. Even though they produce only microscopic amounts of thrust, they are incredibly efficient, and the energy to operate them can come from solar panels or an RTG (nuclear generator), so you can carry much more reaction mass that isn’t chemically reactive.

Of course it’s still not that straightforward. If the gravity tug spacecraft had only one thruster and it was aimed directly at the asteroid (a requirement if there’s only one) and that 100% of the reaction mass impinges and sticks (plastic collision) with the asteroid then the effect cancels out.

What you need to do is put two or more thrusters at an angle like the Apollo escape tower system so that the combined thrust vector is directly away from the asteroid, but the individual jets/beams are aimed to completely miss the asteroid. With an asteroid the size that Tyson described you’d only need a few Newtons of thrust so this is a perfect job for an ion thruster that can operate continuously for a few years.

- Jack

I was interested in what he was saying about planetariums though, it’s too bad the video ended in the middle of it.

If the asteroid is rotating, oddly shaped, varying density, and/or frangible, an impact is *not* at all predictable.

As an Australian, I asked at all my local bookstores and the cost to order it in with the Australian dollar the way it is (kaput) is prohibitive.

Do you know if there are any plans for the book to be released on Australian shelves? Otherwise it’ll be a long wait for the AU dollar to recover before I can get my paws on it.