NASA Aircraft Videos Hayabusa Re-Entry

astroengine writes "Flying above the Australian Outback, NASA's converted DC-8 jet videoed the violent re-entry of the Japanese Hayabusa spacecraft. Flying in front of the disintegrating probe, the mission's sample return capsule can be seen speeding though the atmosphere. According to reports, the capsule landed safely and will be collected by helicopter in the morning." "Bad Astronomer" Phil Plait posts about the successful return as well.

Comments

So far so good

[JoshuaZ]

TFA says that it looks like the capsule is intact. However, we still don't know if there's even anything in the capsule. The original plan called for the probe to fire pellets at the surface to stir up dust for sampling, but the pellet firing failed. We don't know if there's any substantial quantity of dust in the capsule. The probe also had other problems, including difficult with maneuvering which required deviations from the original mission plan. Still, the entire project seems like a very impressive success, to send a probe to an asteroid and then return that to Earth even if the returning sample is very small.

Re:So far so good

[asylumx]

Well, having redundant systems is great but it comes at a cost, too. They would have needed additional power; everything would have weighed twice as much; cost more; changed the amount of thrust necessary not only in launch but in any maneuver. You could then say "Well you should double up at least on systems that are likely to fail!" but then I'd ask... well how do you expect to know before-hand what is likely to fail? Maybe they tested the "pellet gun" a hundred times here and it worked fine?

Re:Just curious

[confused one]

To go to an asteroid and bring back a sample. It has apparently succeeded despite apparently having problmes landing on the surface, having guidance issues, fuel leaks, and thrusters fail.

Re:Just curious

[FatdogHaiku]

Make scientific observations of the physics and geology of an asteroid and hopefully get a sample... that last part may have failed...
http://en.wikipedia.org/wiki/Hayabusa

Oh oh

[Tablizer]

The last time someone fired pellet guns at a small asteroid, 60 mil years ago, the mother struck back with a vengeance.

Good point by the Bad Astronomer

[phlegmofdiscontent]

Mr. Plait makes a good point. People tend to have this view of asteroids being solid rocks, probably because the Earth and other large rocky bodies are solid and the meteorites that make it to the Earth's surface are solid. However, that's not a valid assumption to make and recent science is showing this to be the case. Scientists are finding that some asteroids and various satellites of the outer planets are less dense than expected, suggesting that they're somewhat porous (i.e. masses of rubble instead of solid bodies). Science from the Cassini probe is showing that small bodies in orbit around Saturn are constantly being assembled and destroyed.

Personally, this view of asteroids being porous masses of loosely assembled rubble makes sense, especially from a planetary formation perspective. It's only when you get bodies more than a few hundreds of km in diameter that gravity starts to force the rubble to fuse into solid masses. The implication of all this that Mr. Plait points out is that nuking an asteroid will be akin to bombing a cloud. It's not going to move the asteroid at all, only disrupt it, causing not one impact but several. On the other hand, maybe it would make disrupting asteroids easier. Instead of one large impact, you have thousands of smaller bodies that have a greater chance of simply burning up on reentry.

One other thing that isn't touched on, but is of keen interest to the astronomical community is that the meteorites that we have here have spectra that are very different from the spectra of the asteroids we see in space. The current theory is that the surfaces of asteroids undergo some sort of weathering, which changes the spectra. By gaining physical samples of the surface of an asteroid, this theory can be tested by direct chemical analysis. Very exciting, if it was successful.

Re:Good point by the Bad Astronomer

[Samy Merchi]

I'm a little skeptical of this claim.

Can you elaborate on how the heat generated by the large asteroid (at ground level on impact) somehow ends up radiating off into space, yet the same heat generated higher up in the sky when the bits burn up in re-entry (closer to space) somehow doesn't end up radiating off into space?

As I see it, breaking up an asteroid allows us to convert the kinetic energy to heat higher up in the sky (and closer to space) than a ground level impact would be.

Do you have some links I could read up on?

Re:Good point by the Bad Astronomer

[AK Marc]

Well, one reason it doesn't make sense is that because it's wrong. When it hits the ground, a lot of the energy is "lost" in forms other than heating the atmosphere. It heats the rock, breaks the rock, imparts kinetic energy to the rock, and such.

What is true is that the energy in a single large meteor is sufficient to make the temperature of the air unbreathable over a large area. However, as you've noted, having the energy to do so and actually doing so are two separate ideas. I've not seen anything that went beyond "it could" into the mechanisms by which it would. Or, to say it another way, which would be more disruptive to the planet, a single piece of lead of 10,000 tons slamming into the earth, or 10,000 tons of feathers entering the atmosphere at the same point and with the same energy as the lead? Sure, they have the same energy, but you tell me which will cause more damage and why. No one knows, but he asserted the feathers would be more damaging, and you said something to the effect of "I don't believe you." I think I'd lean towards your side, but again, I don't think there's a genuine analysis of why and how that difference would happen.

Re:Good point by the Bad Astronomer

[AJWM]

What is going to couple the energy transfer from asteroid to atmosphere more effectively, one big rock or a bunch of little ones with the same net energy? The little ones, of course.

Now, the big rock will make a much bigger splash when it hits, creating quite the fireball -- which is a good thing, since heat radiates proportionally to the fourth power of the temperature difference, so a hot fireball will lose its energy to space a lot faster than a lot of smaller, cooler (but still hot!) ones. Yeah, the immediate vicinity is toast, but a lot of the energy is just, in effect, melting the ashes rather than heating up someplace else.

Or to put it another way (no, not a car analogy): would you rather have your whole body exposed to a temperature of say 400 degrees or one finger exposed to say 10,000? Hurts like hell either way, but the former kills you, the latter doesn't.

Background article

[jmichaelg]

This article is a great background article on the trials Hayabusa endured on it's way, while it was there and on its return to Earth. Read the article and be amazed that the probe made it home at all.

Reminded me of Apollo 13's problems and the hacks necessary to deal with them.

Re:Re-entry

[JoshuaZ]

What I've been wondering for many years now, is that the Space Shuttle is on a predicted flight path, so they know where it is and at what time. Why hasn't it's re-entry been filmed properly?

Well it has been. See for example http://www.youtube.com/watch?v=hK1RxQKCmCE http://www.youtube.com/watch?v=XxGeo0ec-F4 http://www.youtube.com/watch?v=S0mP4k--H5o

Re:It's "records" surely?

[JoshuaZ]

"Videos"? I'm sorry, when did "video" become a verb?

Well, "video" is actually a verb to star with. It is a Latin word that means "I see." I don't know where you are, but to use "video" as a verb meaning to record a visual image seems common here in New England. I suspect that it is a shortening of "videotape" as a verb. The transition to "video" makes sense both as a shortening and as a response to the fact that most modern video cameras don't have tapes.

Re:It's "records" surely?

[Belial6]

Probably soon after the introduction of the consumer level video camera. People would say things like, "Could you video tape that event?" Inevitably, someone would eventually shorten the statement shorten it to "Could you video that event?" Expect this to be more common now that far fewer people use tape as their recording medium. Since they are already used to using the adverb "video", and they will feel the need to drop the described verb "tape", the obvious result will be to use the adverb as the verb.

Re:Just curious

[mustafap]

I recon they just stuck a meteorite in it before launch, just in case.

Re:It's "records" surely?

[MichaelSmith]

I still hear "taping" for audio recordings, too.

Satelite reenters; town goes quiet...

[Grog6]

I just got a phone call to join a bunch of people at an underground virus lab; should I worry that I'm an extraterrestrial biologist?

And, of course, I'm the single one out of the group. (hey, we're on /. , right?)

The real problem is that I always wanted to go by way of thermonuclear explosion; am I the wrong guy to get the override key?

gtg...