Fireworks

In honor of Canada Day (and for my neighbours to the south, the fourth of July) here's a video:

While this might look like a meteor, and in fact it is asteroidal material falling to Earth, it's actually some extremely expensive fireworks. It's the Hayabusa spacecraft returning to Earth after visiting asteroid 25143 Itokawa, and the material it brought back was safely encapsulated.

NuSTAR about to launch

NASA is getting ready to launch a new X-ray satellite, NuSTAR. This satellite will observe harder X-rays than we are currently able to. More specifically, this satellite is able to produce high-resolution images of the hard X-rays that come from the decay of isotopes produced in supernovae; the ability to observe hard X-rays with high spectral resolution should also let us probe neutron star formation. Plus it may help us pin down that hard X-ray emission from anomalous X-ray pulsars that nobody understands.

If all this sounds hopelessly technical, sorry. It's still impressive to me that they're going to take this hundred million dollar spaceship, fill it with what amounts to high explosives, strap it underneath a discontinued Lockheed airplane, fly it up into the air near Kwajalein, then drop it and light the fuse. The rocket will then burn for a few hundred seconds, dropping several stages and winding up in low Earth orbit. Once there, the mast holding the mirrors will extend from its one-meter storage canister to its full ten-meter length, the satellite will extend its solar arrays, and scientists will begin debugging and calibrating the instruments. That's if everything goes well; no Pegasus launcher (which this is) has ever actually exploded, though one pair of satellites failed to exit its fairing. So there are some people chewing fingernails, and there's some real drama here. You can watch it online.

Sorry for the hurried nature of the post; I'm planning to watch it live and report on the results as soon as we know.

Edited to add: Success! At least so far. The satellite is in orbit and the solar panels work. The last big worry-point is the extension of the boom; the ten-meter beam that holds the mirrors in position relative to the cameras is currently folded into a one-meter canister. Supposedly, the scientists were reassured that "we can't give you any details, but we know how" to build such a boom, but it won't extend for another week. That'll be followed by a few weeks worth of testing and calibration. But so far so good.

The Core

I've worked with data from X-ray satellites before, and among the many messy things one has to deal with in real data were blocks of time marked SAA. I knew this stood for "South Atlantic Anomaly", but I had only the vague idea that it was a part of the sky that was geomagnetically inconvenient, so that I had to trim it out of my data. The other day I came across a fascinating BBC documentary, titled "The Core":

This documentary talks about the Earth's core and how we're studying it, from seismology to diamond anvils to huge liquid-sodium dynamo experiments. It makes very interesting watching, but I particularly liked that they used the South Atlantic Anomaly as a hook: it caused problems with certain instruments on Hubble, and the documentary is framed as an investigation into why. (More below the jump if you're not worried about spoilers.)

Spuds

From the arxiv: The Potato Radius: a Lower Minimum Size for Dwarf Planets, by Lineweaver and Norman.

This article is kind of neat, not least for the charming way it uses "potato" (and its adjectival variant "potatoid") as a technical term. The point of it is to try to work out how big an object has to be for it to be round.

Ablation

From the arxiv: Momentum Transfer by Laser Ablation of Irregularly Shaped Space Debris, by Liedahl et al.

I don't have a whole lot to say about this one, but how could I ignore a paper about Giant Space Lasers? They're talking about using them to clean some of the junk out of low Earth orbit. While it would take a great deal of power to completely vaporize space junk, all you really need to do is give it enough of a shove (~100-200 m/s) that it starts to dip into the atmosphere (~200 km altitude), where it will slow down and burn up. Just how much of a shove you can get by zapping it with a laser so that some evaporates is not easy to predict, hence the paper.

The particular kind of Giant Space Laser they're talking about is left to some degree unspecified, but it's clear that you want short pulses, so that you get explosive vaporization (gas flow velocity of ~1000 m/s) rather than gentle heating, and they're talking about 10 J pulses (producing 0.1-1 m/s change in velocity for a 1 g target). So it's an awful lot of short powerful pulses. They also mention, in the usual understated scientific way, the possibility of "structural modification" of the debris — that is, the possibility that the bolt or paint flake or whatever will be blown to pieces or bent out of shape by the laser (in addition to the ~10% of the mass that will be outright vaporized). They suggest laboratory experimentation, to which I say, can I help zap random pieces of junk with a high-powered laser and see what happens? Please?

(Photo to the right is of a NASA laser ranging experiment, not actually zapping space debris. Unfortunately.)

Space Race

In honour of Yuri's Night, I'd like to point to this rather nice BBC documentary:

It casts the space race as a personal competition between Sergei Korolyov and Werner von Braun, and is mostly recreations and dramatizations (including the peculiar decision to have the Russians speak English with a Russian accent, except for commands like "Ignition" and "Launch", which the actors could presumably learn and are subtitled). But it's generally well made, and doesn't shy away from either von Braun's Nazi past or the military applications that drove the space race itself: a rocket that could put a man into orbit could also deliver a warhead to a major city, and vice versa. From a public relations point of view, announcing a new milestone in the space race generally went over better than announcing one's ability to more effectively kill millions of people.