A while ago, I started a thread ...

It struck me the other day that we might be ruining the solar system.
Let me explain. Our use of gravity assist to speed up and sling
probes such as Cassini doesn't come for free. It slows down the
planet we are using to sling the probe (conservation of momentum).
This, of course, brings the planet closer to the sun. If we do it
once or twice, that might be okay, but continued use would ruin our
solar system. Maybe we should have a moratorium on using gravity
assist in the future. Thoughts?

Most people said it no affect. For example....

BigKhat wrote:

Christopher James Huff wrote in message .. .
In article ,
(BigKhat) wrote:

Didn't Cassini also use Venus twice and the Earth too which are
*considerably* smaller than Jupiter. As for my math literacy, I'd be
the first one to admit that I'm not very good at math. But heck,
today, you don't need any math (or any technical ability) to become
successful. I was quite a successful technology directory without
really knowing anything about what the developers were actually doing.

Jupiter is about 318 times as massive as Earth and 390 times the mass of
Venus. Compared to the difference between the size of Jupiter and the
probe, that's not very much.

Venus, the lightest of the three, masses 2.26x10^21 times as much as
Cassini. That's 2260,000,000,000,000,000,000 times as much.

Okay, so how much does each gravity assist affect the orbit of Venus
then? How much does it get closer to the Sun after each pass?

(sigh) See that figure above? However much the velocity of a probe is
changed, that of Venus will be changed by 1/that much, if I'm
understanding it correctly.

Suffice it to say that it's so tiny as to be unmeasurable, unles your
space probes have the mass of small moons or greater, themselves. This
is not guessing about unintended consequences, like certain Earth
environmental effects, the numbers involve the ratio of the two massees
involved, how closely they pass each other, how fast they initially
approach each, ant the angles by which they do. Crunch those numbers,
and you get the results. Period. Fly another probe by, and you get
insignifigance times two.

I found it rather ironic and amusing that the January 2005 Sky and
Telescope page 24 has an article explaining that even mighty Jupiter
has moved significantly because of flinging out tiny objects. Maybe
gut feeling and intuition are better than math here!