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Europe plans comet landing
El Jefe writes "The European space agency has plans to land on (a shoot a harpoon into) a comet. The spacecraft is called Rosetta, and is supposed to rendezvous with the comet Wirtanen in 2012. "
And all this time I thought cheesy Hollywood blockbusters where astronauts landed on asteroids had no scientific basis.
I find it interesting, however, that the spacecraft will secure itself to the comet through the use of a harpoon.
I hope it will not be hit by something as Giotto was. (The ESA probe that encountered comet Halley nearest.)
Yep, there's two - one on the lander and one on the orbiter. They're run by the UK's Open University ( http://psri.open.ac.uk )
Don't spear the comet! Comet's are living things too, just like people and Toyotas and Martha Stewart, "Living" magazines! What if we killed it!?!? Or worse, what if we just got it real mad and it came over and gave us a knuckle sandwitch?!?! Then we'd be sorry!!!
Let's not forget W2k in all of this excitement!
And the fact that it hasn't crashed in 3 weeks!
And why none of us are rushing out to buy it!
Forgive me if I am wrong, but a comet travels quite quickly around it's orbit. Also, the mass of a comet is relitivly small. There is no way of getting the space probe up to the speed of the comet until it is on the comet. Do you think that the yank on the comet by the probe will be enough to slow the comet down enough to keep it from escaping the sun's gravity - thus pulling it into the sun and destroying the comet?
how bout using thermonukes on the outer edge to push it ? a couple of megatons ought to alter its trajectory..3 miles in diameter or not.
How come this is news now?
Because of this.
Galileo is currently in Orbit around Jupiter,
see http://www.jpl.nasa.gov/galileo
was the scrapping of the best launch vehicle ever made, the Saturn V, in favor of the Space Shuttle program. The Space Shuttle just skims the atmosphere; the Saturn series of rockets could have taken us to Mars. And deep space probes could get to their destinations faster.
And you're right. A reduction in the PUBLIC money that goes to sports stadiums (to benefit team owners) could give us a better space program.
...and they could set the transmitter to broadcast "Drink Coke" on all hailing frequencies. That could offset the cost of the mission.
> Look at all the craters in the moon. It's evidence that nasty stuff happens. We don't see those craters here on earth, not because they never have hit, but because the
> rain, weather, wind, etc.. have washed them away. The earth is a bigger target.
BTW: The craters on the moon (and the now gone craters on the earth) are victims of an era of heavy bombardements in the past. They don't tell us that comets or asteroids impact the moon (or earth) regularly (say, every 100000 years a 100m asteroid).
Didn't the harpoon just bounce off the Klignon Wessel in Star Trek IV?
What if the surface of the comet is non-conducive to begin penetrated?
I wrote that you can't tell from moon craters what might happen to earth, because moon craters are a leftover from a very past time period.
And (I hate to repeat myself)
"They don't tell us that comets or asteroids impact the moon (or earth) regularly (say, every 100000 years a 100m asteroid)." (you see the "don't"?)
"regularly" is probably the wrong word, english is not my mothertounge.
I try it the other way round:
If the moon had 10 times as many craters this would not make the risk for the earth to be hit by an asteroid now 10 times bigger.
Why not? Since they just are a bunch of tree-hugging, rabbit-mutilators, why not this?
Just as good as any of GreenPeace's other projects.
Instead of saying its unfortunate that the United States couldn't also fund a comet landing mission, Bonnet says "The U.S. always misses the oppurtunity".
:)
Why do we bother to save them every World War? I say next World War we just let them blow each other up, no one would notice the difference anway
If the comet is largely ice anyway, would it be possible to send up a facility to break that ice into hydrogen and oxygen (perhaps using solar power, perhaps using an on-board nuclear source, or maybe something else), then burn said elements as fuel? Sure, we'd lose a bunch of the comet itself, but we'd still have some left by the time it reached Earth...
'nuff said
That would be one really odd comet if it were coming directly at us from the direction of the sun. In any case, have you ever heard of tacking?
I mean, if you're going to collect solar energy to try and move a comet, you're better off not converting the energy to chemical energy and then back again. Just use it right away (solar sail or steam propellant or some such system).
The comet landing in the book was manned. This landing is just going to be a probe. That reminds me, anyone know how they plan to accelerate this probe to the neccessary speed? Comets are travelling _very_ fast when they get near the inner planets.
Besides the fact that it would be very hard to pull that trick (as I've outlined in one of the threads below, even a good solid H-bomb will not provide enough energy by far), would we want to?
The problem here is that a comet has a big tail pointing away from the sun. Actually there are two tails: one composed of gas, and one composed of plasma. These tails can have lengths in the order of tens of millions of kilometers (in some comets, tails of even 100+ million kilometers have been recorded).
That raises the question: Where do we keep that comet? Obviously, we would want it to be close, so that we could travel to it easily. And from that viewpoint, an orbit around the earth within the moon's orbit would be good. But that's only some hundreds of thousands of kilometers away, so the tail WILL sweep the earth.
The plasma-tail is composed of many charged particles, and although they will not cause a direct environmental hazard (they are pulled to the poles by the earth's magnetic field), they will cause a LOT of polar light, even at lower latitudes. Sure, this is beautiful, but it will disrupt satellite communications due to electromagnetic interference. But even that problem is small compared to the one caused by the gas-tail.
The gas-tail is composed mainly of gas, but also of small solid comet fragments (the size of grains of sand). These too won't cause any direct hazard because they are burned up in the upper atmosphere, giving rise to LOTS of "shooting stars". Again, that's pretty, but consider that even in a modest "shooting star rain" (like the ones that repeat every year), sensitive satellite have to be pointed parallel to the "storms" direction to minimize their collision cross-section and to prevent them from being damaged.
A shooting-star rain like the one caused by a close-by comet will be more like a shooting-star typhoon. That is: all the satellites will have to be put in their "save position" every time the comet and the sun line up with the earth. And because the comet is closer than the moon, this will be more often than once a month. And that in turn means that we won't be able to make much use of our advanced satellite system anymore.
An orbit around the moon would be better, but even that is only half a million of km's away. And putting it further away will make it very hard to get there.
Suggestions anyone? One of the ideas that crossed my mind was to put it into a polar orbit (either around the earth or around the moon), any thoughts on that?
Yeah, David Brin did something similar in _Heart of the Comet._ Not a bad book, but not one of Brin's best, either.
I read somewhere that the best way to get on a comet is to hire some oil drillers and put ski's on the Shuttle instead of wheels.
Doesn't this brilliant idea have the possibility of altering the course of the comet? The lander may extremely light, but isn't it possible that it can slightly alter its course because of it? What aftermath effects could this have?
Flower Power!
Okay, what happens if the comet is mostly made of dust -- not ice?
"Whoops!" says Ground Control, and the harpoon pulls out a plug of dust bunny and the Rosetta tumbles out into the void.
That's not enough, because the energy released by a megaton-class bomb is near zero compared to the comet's kinetic energy:
The comet is 3 miles (4800 meters) in diameter, so its radius is about 2400 meters. Assuming its density is equal to that of water (which definately is a best-case scenario), or about 1000 kg/cubic meter, its mass is:
m = 4/3 * pi * radius^3 * density = 5.8*10^13 kg
(about 60 billion metric tonnes).
In order to calculate its kinetic energy we need its velocity. As we are interested in an order-of-magnitude calculation here, we'll just put in something in the same order as the earth's orbital velocity: about 30 km/s (3*10^4 m/s).
That means the comet's kinetic energy is:
T = 1/2 * mass * velocity^2 = 2.6*10^22 J (Joule)
And now for the nukes: a tonne of TNT is equivalent to 4.18*10^9 J of energy. So a megaton-class device will only yield something in the order of 4*10^15 J.
Bottom line: the bomb will yield an ammount of energy that is only 1.5*10^-7 times the kinetic energy of the comet (that is: only about 1 ten-millionth part of the comet's kinetic energy), so changing its trajectory will require something more than just a nuke.
----
Every year during my review, I just pray the words "slashdot.org" aren't mentioned.
Posted by Lord Kano-The Gangster Of Love:
We're not talking about something that only weighs a couple of tons.
Even though I don't know the specifics of this comet, comets can be several miles in diameter. For the sake of arguement let's use 3 miles as the diameter. Three miles thick made up of water, rock, and metal, three VERY heavy materials. Moving VERY quickly as well.
Imagine what a piece of steel the size of a minivan could do if it were moving at the same velocity as a bullet. Now imagine a 3 mile wide piece of water and ferric rock moving as fast as a bullet, now twice as fast, and so on. We don't have the technology to even alter it's path. We're a LONG way away from being able to stop it. We can't throw parachutes on it and wait for it to stop.
LK
This was actually proposed by Dr. Robert Forward as a means of propulsion. He wrote sci-fi novels (see Saturn Rukh) but had a hard scientific basis for it. Look it up at his site and look up HoyTethers.
If the harpooning is not done automatically but is controlled by folks on the ground, will the controllers saying "Thar she blows!" and calling their chief Captain Ahab?
Call me Ishmael.
Ooh, a sarcasm detector. Oh, that's a real useful invention.
One problem is, the US government spending is influenced by the people, and the people all went to see "Star Wars" and think NASA should focus on space travel. It's somewhat short sighted. Trying to figure out a way to populate other planets with people from earth is a very very long and very very expensive process. A true danger that NASA could be working on is to develop a defence against asteroids.
Look at all the craters in the moon. It's evidence that nasty stuff happens. We don't see those craters here on earth, not because they never have hit, but because the rain, weather, wind, etc.. have washed them away. The earth is a bigger target.
Some scientists, even those -outside- the study of space, have started to deticate some of thier time to inform people of these dangers... Kary Mullis comes to mind (he is a Nobel winning chemist, so he is invited to speak at a lot of events. He is asked what he thinks of "global warming" and he acknoledges it, but makes it clear that he does not view it as our biggest threat, because we see it comming, and people can generally adapt pretty well. But, he has started to make a point to talk about dangers of asteroids in every talk he gives, just to spread awareness. And he isn't even an athority on it, just an example, the first person that came into my mind).
Star Trek and Star Wars are good entertainment, but so is Beavis and Buthead, and South Park. Just because thier cool to watch doesn't mean we should try to do what the people in the shows do. Hollywood isn't known for it's accuracy or scientific achievement.
send up a ship with some powerful engines to drop a bunch of harpoons into the thing & tow it back to Earth? They could haul it to the space station & cut it up before bringing it down in pieces on the shuttle. ;-P
Probably freak out aliens in a distant system though. "Hey, that comet was supposed to be back this year...."
-Rev. Randy
- Kate
"DNA is life. The rest is just translation."
This reminds me of the book by Brin and Benford, "Heart of the Comet". Very good book, I liked it more than any of Brin's others.
Benford? I've tried to read one of his (Timescape). Eww. I like hard sci-fi, but I hate the total lack of character and character development.
-Billy
i'm glad all these centuries of whaling technology hasn't gone to waste.
-l
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DS4 was one of my favorite mission.
:-(
Get my e-mail after a captcha test in: http://tinymailt
to keep it from bouncing off. The comet just doesn't have enough gravity for a traditional soft landing.
Christopher A. Bohn
cb
Oooh! What does this button do!?
You're right. I mixed aphelion & perihelion.
Christopher A. Bohn
cb
Oooh! What does this button do!?
A comet's orbit is defined by the same laws as any other. Some comets (primarily "long period" comets) do travel remarkably fast as the progress through the inner solar system (but at the same time progress quite slowly through the outer solar system). Others don't (Comet Eike comes to mind). And, no the "yank" won't affect the comet measurably at all -- consider the mass of the comet and the mass of Rosetta, and you'll realize it'd be analogous to a fly pushing off against your arm.
Christopher A. Bohn
cb
Oooh! What does this button do!?
The problem is "nongravitational accelerations" -- a comet's orbit, unlike most other bodies in the solar system, changes from orbit to orbit. The outgassing provides accelerations that subtly change its orbit. While accelerations so close to aphelion have less effect than if they were near perihelion, they still make it difficult to precisely predict its next orbit. This should only raise a concern if it was already going to be passing close to the Earth in one of its future orbits -- the change is too subtle to cause drastic shifts.
Christopher A. Bohn
cb
Oooh! What does this button do!?
When Halley's last visited, they launched a probe called Galileo. Did that land on the comet or just come really close to it?
ian
Yes, it was Giotto. Don't know what I was thinking. Still, that was a while back and I was much younger and care-free.
ian
And here's a reference:
http://nssdc.gsfc.nasa.gov/planeta ry/giotto.html
ian
But the US is attempting it in 2005.
The problem is that the NASA just cancelled Champollion. 8(
It seems that the combination of Clinton's budget cuts and the money-sucking pit known as ISS are having some severe impacts on NASA. On top of that, Dan Goldin keeps sucking up and saying how happy he is to "do more with less". The problem is that the real science at NASA has started to suffer to an ever-increasing degree.
Of course, Goldin hasn't cut Al Gore's pet satellite, Triana.So, in exchange for bailing on new, potentially exciting planetary science, we are going to get a screensaver of the Earth and a few rich Russian cosmonauts.
gigantino.tv - Heavy but weighs nothing.
I'm dissapointed that the United States recently shelved their plans to do a very similar thing, citing that there are better things to spend our money on.
When the comet comes (and we all know that, eventually, it will) we're all going to regret that we had paid a little less to build sports stadiums and provide corporate welfare and a little more on space research.
And if anyone questions the odds of a comet hitting? They're better than the odds of winning the lottery. And almost every lottery has a winner...
---
seumas.com
I mean Rosetta has only been worked on for the last decade....
;-)
People started work on Rosetta before Linus started work on Linux.
Anyway - this is an amazingly cool mission, but I'm not sure of their chances of orbiting a small outgassing body, especially since the measurements of the comet make it look smaller and smaller every time we look at it
Stardust is the US response - they want to fly through the tail of a comet and pick up dust in an aerogel capture system for return to earth.
Rosetta looks much more interesting.
It has to work!@# I mean, they did it in Armageddon, right?!
an anchor than a harpoon. This is a harpoon like screw anchors are harpoons. Usually you harpoon something from far away, unless you are playing Ahab riding the whale.
NASA cancelled the comet-landing probe earlier this week:
Hmm... the URL doesn't work, even though I cut and pasted it exactly. Damn Yahoo. Anyhow, it's http://dailynews.yahoo.com/headlines/ap/science/st ory.html?s=v/ap/19990628/sc/comet_lander _1.html
Of course, Goldin hasn't cut Al Gore's pet satellite, Triana.So, in exchange for bailing on new, potentially exciting planetary science, we are going to get a screensaver of the Earth and a few rich Russian cosmonauts.
Amen. I couldn't have said it better myself. I'm involved with several experiments scheduled for ISS, so I personally see the effects of CHEAPER part of Goldin's mantra.
Fortunately, NSF is finding some real science to add to Triana (GoreSat). I still personally don't see the justification.
~afniv
"Man könnte froh sein, wenn die Luft so rein wäre wie das Bier"
~afniv
"Man könnte froh sein, wenn die Luft so rein wäre wie das Bier"
Richard von Weizs
Well, I don't think it was a "guess", exactly. The orbit of Halley's comet is pretty darned well-known. (Though it is pretty darned cool that we're beating him to the punch by over fifty years by landing on a different comet.)
The 2003 NASA mission the article talks about was scrapped June 29th. The link to the story can be found at the bottom of the page from the article above.
Or just go
here
The article seems to state that Europe is trying to land a probe on a comet first in 2011. But the US is attempting it in 2005. Then they bring up the issue about the US always missing out on stuff. Last I checked, we landed a probe on Mars and if the 2005 comet landing works out, the US will have beat the 2011 landing. Maybe I just missed the point.
Bad Mojo
"If you can't win by reason, go for volume." -- Calvin
"I want to use software that doesn't suck." - ESR
"All software that isn't free sucks." - RMS
The trouble with asteroids is that while the risk may be great (we are reasonably certain it's led to mass extinctions before), the risk in any given time period -- say, a human life of 75 years -- is rather small. This leads to an underappreciation of the overall risk.
...
Nobody needs to lose sleep over this; the largest impact we've seen this century is Tunguska, and the odds are still rather small that a Tunguska event will strike a populated area. On the other hand, the odds are higher that an impact tsunami will cause widespread coastal destruction and loss of life. Our only chance is to have sufficient warning time. By definition, an undiscovered object could strike with warning time == zero. It's estimated that we know of maybe 10% of the large-enough-to-hurt-sized rocks that cross the earth's orbit, so the job of finding them isn't trivial.
The good news is that there is modest funding for a hazardous objects search.
The NASA Impact Hazards site has lots more info, including the search project called "Spaceguard".
My take on this is not so much worry that something might happen, as sardonic awareness that it would be Really, Really Stupid to finally figure out this is a problem (last 20 years) and then have our civilization wiped out. Especially if we really are the only intelligent one around
lake effect weblog
{Network engineer in Chicago--looking for work!}
Three words: Conservation of Momentum.
.... well, if you could do that, you might be able to achieve placing its orbit into a slightly lazier circle that wouldn't get as much acceleration from the sun. Repeat this ten times (in ten 20-year cometary orbits) and you might get a comet that you can aim roughly at the earth.
Even if it's small, it's going very fast -- generally 10 or more times the maximum speed that any human-built spacecraft have ever achieved (including via gravity assist).
Now assume we have a spacecraft with ten times the capability of anything built today. You would need to have it rendezvous with the comet at the edge of the solar system, then expend all its fuel slowing down an object that's at least a factor of 100 larger in mass than itself, and
Which you would want to do, why?
lake effect weblog
{Network engineer in Chicago--looking for work!}
Are you suggesting there should be one news article when a project is started, and no more news articles on that project until ... when?
/., I've known about it for three hours and fourteen minutes already, why is Hemos wasting my time with old news like this?!"
Sheesh.
Slashdotters are very spoiled. Instant news! Worldwide distribution! Five minute lead times!
"Hey, I've known that since at least yesterday!"
"This was posted in a response to slashdot item on Linux clustering that drifted into a discussion of planetary orbits. Since I read everything on
lake effect weblog
{Network engineer in Chicago--looking for work!}
I wonder.. Will VW sue Apple for ripping off the TV commercial style.
_______
2B1ASK1
Let's hope we can get some real samples (or at least spectroscoped/gas chrom'd images) back to Earth. If complex carbon compounds are found onboard the comet, it could confirm several theories about how life developed.
- Read fiction at www.espressostories.com
NASA hopes to do something similar in 2005 -- check out the ST4/Chompollion mission site. (The ST4 project used to be called DS4, one of the New Millenium missions)
Ok, ok, so I jumped the gun. NASA sucks for cancelling ST4. (But they don't suck in other areas, so I'm not heartbroken :)
-g.
The CNN report is inaccurate, the NASA cometry
mission called ST-4 or Champollion has been
cancelled because of budget pressure. It seem
they had to choose between that and the Mars 2001
lander. They kept the Mars misson as more of
the money has already been spent.
Details in http://www.spaceviews.com/
PS How come this is news now? There have been
details of the mission on the ESA web site for
at least 2 years. Work started on it
in the early 90's.
When something is as massive as a comet, you need some really big horkin engines (technical term) to move said comet. We (humanity) don't have those engines. Even a little orbital adjustment of a small comet would be extremely challenging. If this comet is large enough to navigate a spacecraft to it and lang on it, we can assume it's too large to move.
have a look at :t s.html
http://www.mpae.gwdg.de/mpae_projects/mpae_projec
How would they power it? Solar power?
Hasn't this already been discovered? I seem to recall something about spectrographic analysis showing this (and/or amino acids) on some comets.
I'm sure "SlashdotMedia" will improve on all the wonders that Dice Holdings blessed us all with
So when is Greenpeace going to launch it's protest spacecraft?
I'm sure "SlashdotMedia" will improve on all the wonders that Dice Holdings blessed us all with
The second "sequel" to 2001: A Space Odyssy features landing on the Halley comet. Guessed right, the next visit is on 2061. Actually, it's one of the best in the series, so go get it if you still haven't read.
You know, according to the "hacker" hype, we have to deal with sci-fi extensively. No problem with me though, I just love sci-fi.
--exa--
A joint mission between NASA and a Japanese counterpart is planing a mission called MUSES-C. It is supposed to drop a tiny rover on an asteroid.
:-)
It does not seem to use a harpoon, though
"The United States launched its first comet mission in February -- the Stardust spacecraft, which is to pass within 140 km (90 miles) of the Comet Wild-2 in January 2004. The mission hopes to be the first to capture dust from a comet and return it to Earth in 2006. "
Ok this is off topic, but, can anyone confirm or deny that the Stardust Casino and Hotel is actually named after abomb fallout, because it was constructed during the period of time when atomic testing occured in Nevada? I have a long standing bet with a friend, and we can't nail this down. I read this a long time ago, but can't find it now. If you look at the stardust sign with all the lights, it looks like an abomb..
-- Virtual Windows Project
And you know how we Europeans come up with such great ideas as this 24cylinder coupes and other such useless gimmicks? Our Engineers have their daily ration of CRACK...
It speeds up the development of stupid ideas by a factor of 10
"Nimis exaltatus rex sedet in vertice - caveat ruinam!"
already have samples ....
a probe that fluing itslef through the tail of some comet recently had a little bit of aerogel in it ( 2% the density of air ) . It captured particles that contained carbon compounds .
Check this article in Scientific American. Great overview.
is about the only practical way to do anything significant to the orbit of a comet.
If the comet has a lot of high-vapor-pressure stuff (methane, water, frozen hydrogen, very small rocks...) a big black tarp set up just right might have interesting effects...
Fear my wrath, please, fear my wrath?
Homer
We apologize for the inconvenience.
The part of the mission I am familiar with is CIVA. This is an instrument on the lander (ROLAND I think) that has an infrared imager and a visible imager (the orbiter also has imagers). The imagers will be used to do spectroscopy on core samples of the comet: the lander will drill a sample from the comet, then illuminate it with light of different wavelength, and image it. This should give spatial information and chemical composition.
Of course, this assumes the spacecraft launches safely, rendezvous with the comet safely, lands safely, the instruments work, the radios work...
And yes, on the outward bound leg it could be coming at us from the general direction of the sun.
Ignorance killed the cat. Curiosity was framed.
Heh heh I think you meant this response to the previousstory.
To invent, you need a good imagination and a pile of junk. --Thomas Edison