Discussion
Utterly amazing. This is the sort of thing that should have happened not long after the Apollo era really, but I'm hugely thankful that it has happened at all - it is exactly the sort of thing that gets the next generation of scientists and engineers motivated, possibly even before they have started school let alone university.
Note that the comet's orbit will not come inside the orbit of the earth, so the probe isn't going to get that hot. The result is that the comet will probably (hopefully) not chuck out vast amount of dangerous debris, yet it will be enough to do science on. The triangular "orbit" is 3 sections of an elliptic orbit, with with small engine burns performed twice a week to keep the probe in station around the comet. Otherwise, the low mass would mean an orbit that was many km out into space, which doesn't make for good imaging.
Note that the comet's orbit will not come inside the orbit of the earth, so the probe isn't going to get that hot. The result is that the comet will probably (hopefully) not chuck out vast amount of dangerous debris, yet it will be enough to do science on. The triangular "orbit" is 3 sections of an elliptic orbit, with with small engine burns performed twice a week to keep the probe in station around the comet. Otherwise, the low mass would mean an orbit that was many km out into space, which doesn't make for good imaging.
el stovey said:
Why land then harpoon? Could they not get close, then harpoon it and reel themselves in to the surface?
Sorry in advance if that's stupid, I don't have much knowledge of this topic .
Is this comet rotating ? Would make tethering a rope a bit risky. I would guess low gravity would make it hard to maintain a geosynchronous orbit.Sorry in advance if that's stupid, I don't have much knowledge of this topic .
Simpo Two said:
Moonhawk said:
According to Wikipedia - it has an estimated escape velocity of 0.46 m/s. Compare that to the earth's escape velocity of 11.186 km/s
So around 25,000 less.
So about 0.00004G then... not much!So around 25,000 less.
Simpo Two said:
What gravity force would that have?
I just had to work it out. My maths isn't what it used to be, but I think the force due to gravity between the probe and the comet is about 30 micronewtons, which by happy coincidence is about the weight of a grain of sand on Earth.F=GMm/r^2 where G=6.67x10E-11, M=3x10E12, m=1.5x10E3, r=10E5
Another happy coincidence is that googling '30 micronewtons' led me to this NASA page on microthrusters:
http://nmp.jpl.nasa.gov/st7/TECHNOLOGY/thrusters.h...
</geek mode>
gottans said:
How far will dumping a lander on the comet alter its trajectory and will it come back to bite us and send us to the same fate as the dinosaurs?
It'll have very little effect - much less than the constant radiation pressure and Yarkovsky effect caused by solar radiation.http://en.wikipedia.org/wiki/Yarkovsky_effect
scorp said:
Oh that's cool. I'd read about the path but it's good to see it visualised. That's some seriously impressive rocketry right there.
Moonhawk said:
jmorgan said:
Ah, but, is it th same as everything else? That is from the lowly buts of dust to the massive stars, did they start with the same?
Not sure I understand the question. Gravity is a function of mass. What the object is made of is irrelevant.For one mad minute I thought all had the same gravitational pull (being a non educated oil) then realised I have missed a few important bits.
Edit. Going on to think that the pile of left over solar system stuff that coalesced into that duck had some similarity to the first bits of the solar system forming. Now see I have a few
s in that thought.Edited by jmorgan on Saturday 9th August 14:09
Simpo Two said:
Triangular 
If you're using rocket power to alter direction is it still an orbit?
A similar question was asked during the press conference.If you're using rocket power to alter direction is it still an orbit?
As I understood it the probe will enter a tight orbit at a later stage (which may still require some small corrections). At this point the probe was described to be in a hyperbolic quasi-orbit, this allows the mass of the comet to be more precisely calculated by measuring the affect of the comet's gravity on the probe during the probe's "free-falling" straight passes.
Laplace said:
Eric Mc said:
The animation posted above seems to show pictorially precisely that happening.
It does indeed and very nicely too, but it doesn't tell you why it takes this approach.Tying up the verbal explanation given above with the earlier movie demonstrates it all clearly.
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