Dawn enters Vesta orbit

[bush_cheney2004]

Chalk one up for ion propulsion....NASA's Dawn dual flyby-orbiter mission has just parked itself around asteroid Vesta...stop #1. The spacecraft has the name of 360,000 public "enthusiasts" on a microchip near the high gain antenna. Did anybody here get on the list?

http://dawn.jpl.nasa.gov/mission/status.asp

http://en.wikipedia.org/wiki/Dawn_%28spacecraft%29

[Bonam]

Yeah NASA does still manage some cool stuff in terms of their robotic missions. Given that they have pretty much failed at HSF, they should abandon that and just focus on what they can still do that works well: robotic exploration, where they can also better push new technology development.

The spacecraft has the name of 360,000 public "enthusiasts" on a microchip near the high gain antenna. Did anybody here get on the list?

Yep. And the one on the Phoenix Mars lander too. I figured why not?

[Sir Bandelot]

Many of these missions are now international in scope, with technology components and scientists provided by other countries.

"The Max Planck Institute for Solar System Research (located in Lindau Germany) and the German Aerospace Center provided the framing cameras, the Italian Space Agency provided the mapping spectrometer."

Mission Leaders-

Chris Russell, Dawn Principal Investigator, UCLA

Carol Raymond, Deputy Prinicipal Investigator, JPL

Fabrizio Capaccioni, Technical Manager, Co-Investigator, Istituto Nazionale di Astrofisica

Maria Teresa Capria, VIR Team Member, Data Archive Manager, Co-Investigator, Istituto Nazionale di Astrofisica

Ulrich Christensen, Co-Investigator, Max Planck Institute Germany

Angioletta Coradini, VIR Team Leader, Co-Investigator, Istituto Nazionale di Astrofisica

Maria Cristina De Sanctis, VIR Deputy Leader, Co-Investigator, Istituto Nazionale di Astrofisica

Ralf Jaumann, Dawn Co-Investigator, German Aerospace Center

Steve Joy, Manager, Dawn Science Center, UCLA

H. Uwe Keller, Co-Investigator, Technische Universität Braunschweiger

[Oleg Bach]

Chalk one up for ion propulsion....NASA's Dawn dual flyby-orbiter mission has just parked itself around asteroid Vesta...stop #1. The spacecraft has the name of 360,000 public "enthusiasts" on a microchip near the high gain antenna. Did anybody here get on the list?

http://dawn.jpl.nasa.gov/mission/status.asp

http://en.wikipedia.org/wiki/Dawn_%28spacecraft%29

Mine is there by mistake.

[bush_cheney2004]

Mine is there by mistake.

By mistake? Are you a member of the Planetary Society...or just the Mile High Club?

http://www.planetary.org/programs/projects/international_mission_participation/messages/namesinspace.html

[Oleg Bach]

By mistake? Are you a member of the Planetary Society...or just the Mile High Club?

http://www.planetary.org/programs/projects/international_mission_participation/messages/namesinspace.html

The mile low club to be exact. Did I ever tell you about the time I hung out with Gene Rodenberries widow - Maja..We stood in the back lot and talked - it was interesting - she did mention that Gene was up there floating around the earth..She had one question of me...regarding "Earth The Final Conflict" - why are the ratings so low?....hell if I knew - I was picking up a cheque and Genes wife was making a guest appearance - I was highly entertained by the whole thing - my ratings were high....who cares about the rest of the world...apparently GENE did not see fit to be buried on earth - apparently his ratings were low as far as humanity.

[Oleg Bach]

Saw a pic - very strange that this small body has a gravitational pull that can orbit an object - How big does something have to be to do that?

[bush_cheney2004]

Saw a pic - very strange that this small body has a gravitational pull that can orbit an object - How big does something have to be to do that?

Interesting question, but any "small" body that has sufficient mass to accrete as a sphere certainly could capture a much smaller mass object like the Dawn orbiter with slowed relative velocity, as was done here. (Vesta has a mean diameter of 530 kilometers.) Gravitational forces are assumed to be directly proportional to the product of two object's masses divided by the square of their relative distance, i.e. farther away being a weaker force.

The entire system would have a center of gravity (center of mass) in the same way, favoring the much larger object. For instance, the Earth-Moon center of mass is at about 75% of the Earth's diameter.

There are several other factors to consider like the masses of other large bodies in the system (e.g. Sun, Jupiter), centrifugal force, etc.

[Wild Bill]

Saw a pic - very strange that this small body has a gravitational pull that can orbit an object - How big does something have to be to do that?

Any size at all! As long as the OTHER body is smaller!

Everything has some gravity. Weaker things can orbit stronger ones. An orbit is just a special case where the speed of the smaller object is just slow enough that it can't fly away from the larger one but it won't fall "down" and hit it either. It's actually perpetually falling into the larger object! It's a delicate balance and if something were to disturb its speed the orbit would be broken and it would either fly away or fall into the larger body.

Mother Nature doesn't wait until an object grows to a minimum size before issuing it some gravity!

Edited July 20, 2011 by Wild Bill

[Oleg Bach]

Any size at all! As long as the OTHER body is smaller!

Everything has some gravity. Weaker things can orbit stronger ones. An orbit is just a special case where the speed of the smaller object is just slow enough that it can't fly away from the larger one but it won't fall "down" and hit it either. It's actually perpetually falling into the larger object! It's a delicate balance and if something were to disturb its speed the orbit would be broken and it would either fly away or fall into the larger body.

Mother Nature doesn't wait until an object grows to a minimum size before issuing it some gravity!

So there is a perpetual motion machine - such as the orbit you describe or our solar system is also a good example. What is remarkable is that "delicate balance" - such percision..the perfect machine..totally efficent - but I put to you also - Does gravity in time decay and lesson? Is it a force that expends itself over a long period of time? In other words do object run out of gravity?

[Bonam]

So there is a perpetual motion machine - such as the orbit you describe or our solar system is also a good example. What is remarkable is that "delicate balance" - such percision..the perfect machine..totally efficent - but I put to you also - Does gravity in time decay and lesson? Is it a force that expends itself over a long period of time? In other words do object run out of gravity?

Gravity is perfectly lossless only for point masses. For real objects, like planets, there is a bit of a loss due to gravitational damping (tidal effects). The energy is expended on constantly deforming the bodies that are orbiting each other, since the side closer experiences a stronger pull than the side farther away. Very slowly, the system does lose energy. For example, the Moon is constantly expending its orbital energy by dragging around the tides of the Earth's oceans with its gravity.

In the solar system, energy losses are much greater from the aerodynamic drag of bodies passing through the medium of the solar wind than they are from gravitational damping. Even these losses, however, are negligible over time periods of billions of years, so, effectively, for the 10 billion year lifespan of the Sun, the orbits of the planets will not decay appreciably.

The only real point masses are black holes, but they lose energy orbiting each other as well, due to higher order gravitational interactions that are described by general relativity but are not relevant for objects besides black holes and neutron stars.

The universe does not create perpetual motion machines. However, the energy losses are so slow that for some system they may be hardly measurable over the entire lifetime of the universe.

As for how small an object you can orbit... the answer is arbitrarily small. The smaller it is, the slower you have to go to be captured by its gravity, but there is no hard limit.

Edited July 21, 2011 by Bonam

[bloodyminded]

Gravity is perfectly lossless only for point masses. For real objects, like planets, there is a bit of a loss due to gravitational damping (tidal effects). The energy is expended on constantly deforming the bodies that are orbiting each other, since the side closer experiences a stronger pull than the side farther away. Very slowly, the system does lose energy. For example, the Moon is constantly expending its orbital energy by dragging around the tides of the Earth's oceans with its gravity.

In the solar system, energy losses are much greater from the aerodynamic drag of bodies passing through the medium of the solar wind than they are from gravitational damping. Even these losses, however, are negligible over time periods of billions of years, so, effectively, for the 10 billion year lifespan of the Sun, the orbits of the planets will not decay appreciably.

The only real point masses are black holes, but they lose energy orbiting each other as well, due to higher order gravitational interactions that are described by general relativity but are not relevant for objects besides black holes and neutron stars.

The universe does not create perpetual motion machines. However, the energy losses are so slow that for some system they may be hardly measurable over the entire lifetime of the universe.

As for how small an object you can orbit... the answer is arbitrarily small. The smaller it is, the slower you have to go to be captured by its gravity, but there is no hard limit.

Very interesting, Bonam. Nicely explained.

[Oleg Bach]

Gravity is perfectly lossless only for point masses. For real objects, like planets, there is a bit of a loss due to gravitational damping (tidal effects). The energy is expended on constantly deforming the bodies that are orbiting each other, since the side closer experiences a stronger pull than the side farther away. Very slowly, the system does lose energy. For example, the Moon is constantly expending its orbital energy by dragging around the tides of the Earth's oceans with its gravity.

In the solar system, energy losses are much greater from the aerodynamic drag of bodies passing through the medium of the solar wind than they are from gravitational damping. Even these losses, however, are negligible over time periods of billions of years, so, effectively, for the 10 billion year lifespan of the Sun, the orbits of the planets will not decay appreciably.

The only real point masses are black holes, but they lose energy orbiting each other as well, due to higher order gravitational interactions that are described by general relativity but are not relevant for objects besides black holes and neutron stars.

The universe does not create perpetual motion machines. However, the energy losses are so slow that for some system they may be hardly measurable over the entire lifetime of the universe.

As for how small an object you can orbit... the answer is arbitrarily small. The smaller it is, the slower you have to go to be captured by its gravity, but there is no hard limit.

Thanks - you are a fine teacher - I grasp the point with ease...and what is good about your explanatory is that it seems more than theoretical. I can tell that the concept is based in solid fact and holds a lot of gravity...hope you never run out of mass or energy.

[Bonam]

Very interesting, Bonam. Nicely explained.

Thanks - you are a fine teacher - I grasp the point with ease...and what is good about your explanatory is that it seems more than theoretical.

Thanks guys I do enjoy explaining scientific concepts when people are interested.

[DogOnPorch]

Thanks guys I do enjoy explaining scientific concepts when people are interested.

Flew a Soyuz manually to the ISS a few nights back. Quite proud.

http://www.orbithangar.com/searchid.php?ID=4545

[DogOnPorch]

Here's one for you, Bonam.

http://www.orbithangar.com/searchid.php?ID=4898

[Topaz]

For all you that remember that song "Telstar" which was record to join in with the race to space in 1962, I wonder what the song would sound like to hear one the finishing of space?

[DogOnPorch]

What finishing of space?

[Bonam]

For all you that remember that song "Telstar" which was record to join in with the race to space in 1962, I wonder what the song would sound like to hear one the finishing of space?

I can't understand what this sentence is supposed to mean.

[Bonam]

Here's one for you, Bonam.

http://www.orbithangar.com/searchid.php?ID=4898

Looks cool.

[bush_cheney2004]

You guys are too young to remember "Telstar" by The Tornados. The song was also covered by The Ventures. Thanks Topaz!

Edited July 26, 2011 by bush_cheney2004

[DogOnPorch]

Looks cool.

I'll turn you into an Orbitnaut yet.

[DogOnPorch]

You guys are too young to remember "Telstar" by The Tornados. The song was also covered by The Ventures. Thanks Topaz!

Too young, eh? Why thanks!

[dre]

Gravity is perfectly lossless only for point masses. For real objects, like planets, there is a bit of a loss due to gravitational damping (tidal effects). The energy is expended on constantly deforming the bodies that are orbiting each other, since the side closer experiences a stronger pull than the side farther away. Very slowly, the system does lose energy. For example, the Moon is constantly expending its orbital energy by dragging around the tides of the Earth's oceans with its gravity.

In the solar system, energy losses are much greater from the aerodynamic drag of bodies passing through the medium of the solar wind than they are from gravitational damping. Even these losses, however, are negligible over time periods of billions of years, so, effectively, for the 10 billion year lifespan of the Sun, the orbits of the planets will not decay appreciably.

The only real point masses are black holes, but they lose energy orbiting each other as well, due to higher order gravitational interactions that are described by general relativity but are not relevant for objects besides black holes and neutron stars.

The universe does not create perpetual motion machines. However, the energy losses are so slow that for some system they may be hardly measurable over the entire lifetime of the universe.

As for how small an object you can orbit... the answer is arbitrarily small. The smaller it is, the slower you have to go to be captured by its gravity, but there is no hard limit.

That covers gravitational tidal effects, and gravitational radiation (third paragraph from the end), but what about atmospheric drag? Space isnt a vacuum theres a few hydrogen atoms per cubic centimeter that moving objects have to plough through, and the space around objects can be even more dense.

[Bonam]

That covers gravitational tidal effects, and gravitational radiation (third paragraph from the end), but what about atmospheric drag? Space isnt a vacuum theres a few hydrogen atoms per cubic centimeter that moving objects have to plough through, and the space around objects can be even more dense.

Mentioned that in the 2nd paragraph you quoted