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Can someone actually explain me how is it possible to even rendezvous with an object that moves so fast and is so violent? I mean, this is not a Moon orbiting a

Can someone actually explain me how is it possible to even rendezvous with an object that moves so fast and is so violent? I mean, this is not a Moon orbiting a Planet, but rather a very violent object storming through the Universe.

soneca 12y ago
They made Rosetta also moves so fast. "Violent" here is an exageration, as at the vacuum (or near-vacuum), if both objects are moving in the same direction and speed, relatively to each other they are very close to still... and calm.
mml 12y ago
The lander is in the comet's frame of reference. To it, the comet is stationary, and the universe is whipping around them. The same way you perceive yourself to be stationary on the earth, despite earth orbiting the sun at 67 thousand miles an hour.
robin_reala 12y ago
Movement in space is relative. The probe effectively caught up to the back of the comet as it was coming back in towards the sun. This image from the Guardian is slightly outdated but presents the path Rosetta’s taken well: http://static.guim.co.uk/sys-images/Guardian/Pix/pictures/2014/1/20/1390240703787/rosettaLocatorWeb.png http://static.guim.co.uk/sys-images/Guardian/Pix/pictures/20... As for violence, I assume you’re talking about the comet’s tail? This happens when comets approach their perihelion and the sun heats them up. The heat starts a process of outgassing from the comet which the solar wind blows away (the tail of a comet always points away from the sun). Rosetta’s target isn’t close enough to the sun at the moment for this to be problematic.
Sharlin 12y ago
The 67P is a short-period comet. Its orbit is quite elliptical, yes, but nowhere near as elliptical as those of long-period comets, arriving from the Kuiper belt or even farther from the freezing outer reaches of the Solar System. Consequently, its velocity, even near perihelion, is not that high, and matching orbits with it is, while not trivial, not hopelessly hard either. That said, Rosetta did spend 10 years in space and needed multiple gravity assist maneuvers in order to finally rendezvous with the comet. Still, the circuitous route was more about fuel economy than any fundamental difficulty with reaching its destination.
- angdis 12y ago
  What I would like to know is how did ESA calculate the trajectory that Rosetta needed to take to meet up with the planets for the purpose of gravity-assist maneuvers? I mean this was a 10 year journey, is there any way to make corrections to the trajectory? How much room for error is there?
  - Sharlin 12y ago
    With smart minds, Newtonian mechanics, numerical methods, and some computer time. The path was complex, mut not much moreso than eg. MESSENGER's seven-year journey to Mercury. Space probes usually do a couple of course corrections burns en route, but the margin of error is pretty small. Fortunately, orbital mechanics is highly predictable at human time scales even though n-body systems are quite chaotic in the long term. If the launch vehicle puts you straight on the calculated trajectory you can be pretty damn sure you'll be on the right path even ten years from now.
lmm 12y ago
A comet is still in a solar orbit (admittedly an eccentric one); matching velocity with it is still possible, if you need to go faster that just means using a few more gravitational assists on the way there. Matching the rotation of the comet is harder, but again it's just a rotation - the comet is not in a position where it's outgassing, so it'll be rotating about some axis with some angular velocity. Once once you're orbiting the comet you can take your time, or even just schedule the descent for a time when things happen to line up. They planned this one a few days ago AIUI.
outworlder 12y ago
This is both a witty and serious comment(and also, late): go play Kerbal Space Program. You'll develop an intuitive grasp of this kind of thing.

soneca 12y ago

They made Rosetta also moves so fast. "Violent" here is an exageration, as at the vacuum (or near-vacuum), if both objects are moving in the same direction and speed, relatively to each other they are very close to still... and calm.

mml 12y ago

The lander is in the comet's frame of reference. To it, the comet is stationary, and the universe is whipping around them. The same way you perceive yourself to be stationary on the earth, despite earth orbiting the sun at 67 thousand miles an hour.

robin_reala 12y ago

Movement in space is relative. The probe effectively caught up to the back of the comet as it was coming back in towards the sun. This image from the Guardian is slightly outdated but presents the path Rosetta’s taken well: http://static.guim.co.uk/sys-images/Guardian/Pix/pictures/2014/1/20/1390240703787/rosettaLocatorWeb.png http://static.guim.co.uk/sys-images/Guardian/Pix/pictures/20... As for violence, I assume you’re talking about the comet’s tail? This happens when comets approach their perihelion and the sun heats them up. The heat starts a process of outgassing from the comet which the solar wind blows away (the tail of a comet always points away from the sun). Rosetta’s target isn’t close enough to the sun at the moment for this to be problematic.

Sharlin 12y ago

The 67P is a short-period comet. Its orbit is quite elliptical, yes, but nowhere near as elliptical as those of long-period comets, arriving from the Kuiper belt or even farther from the freezing outer reaches of the Solar System. Consequently, its velocity, even near perihelion, is not that high, and matching orbits with it is, while not trivial, not hopelessly hard either. That said, Rosetta did spend 10 years in space and needed multiple gravity assist maneuvers in order to finally rendezvous with the comet. Still, the circuitous route was more about fuel economy than any fundamental difficulty with reaching its destination.

angdis 12y ago
What I would like to know is how did ESA calculate the trajectory that Rosetta needed to take to meet up with the planets for the purpose of gravity-assist maneuvers? I mean this was a 10 year journey, is there any way to make corrections to the trajectory? How much room for error is there?
- Sharlin 12y ago
  With smart minds, Newtonian mechanics, numerical methods, and some computer time. The path was complex, mut not much moreso than eg. MESSENGER's seven-year journey to Mercury. Space probes usually do a couple of course corrections burns en route, but the margin of error is pretty small. Fortunately, orbital mechanics is highly predictable at human time scales even though n-body systems are quite chaotic in the long term. If the launch vehicle puts you straight on the calculated trajectory you can be pretty damn sure you'll be on the right path even ten years from now.

lmm 12y ago

A comet is still in a solar orbit (admittedly an eccentric one); matching velocity with it is still possible, if you need to go faster that just means using a few more gravitational assists on the way there. Matching the rotation of the comet is harder, but again it's just a rotation - the comet is not in a position where it's outgassing, so it'll be rotating about some axis with some angular velocity. Once once you're orbiting the comet you can take your time, or even just schedule the descent for a time when things happen to line up. They planned this one a few days ago AIUI.

outworlder 12y ago

This is both a witty and serious comment(and also, late): go play Kerbal Space Program. You'll develop an intuitive grasp of this kind of thing.