[neilep (OP)]

Dearest Iss-ologists,


As a sheepy I of course spend most my time creating experiments that need to be performed in Space. It's all I think about , from the moment I awake, to the time I fall asleep.


So, whajafink of this one ? Throw a ball from the ISS in a way that it will return from the other side ?


do-able ?









If I Throw A Ball  From The ISS, Will It Eventually Return From The Other Side ?

whajafink ?


hugs, shmishes, dirty dishes !


mwah mwah mwah !

Neil
xxxxx

Oh ISS
Ewe ain't no fool
Can we play
Catch the ball ?

[Janus]

If you throw a ball from the ISS, you will be putting it into a slightly different orbit than the ISS itself is in.  Depending on which direction you throw it, the average altitude of this orbit will be higher or lower than that of the ISS, which will give it a different orbital period. 
After one orbit, it will return to the point at which you tossed it.  The ISS will return after one orbit also.  But since their orbital periods will be different, it won't be at the same time.
So, let's say we toss it in the opposite direction as the ISS is moving.  You are, in effect, decreasing its orbital velocity.  This will cause it to start to lower its orbital altitude,  But doing this causes it to gain orbital velocity.  Eventually, this increase in velocity will be greater than the speed you threw it, it will stop "falling behind" the ISS, and begin to catch up.  it would eventually pass the ISS  (at a lower altitude), and rush ahead.  At some point it will reach perigee, and begin to climb back up, shedding speed as it does so. Some time after that, it will be once more moving slower than the ISS, and the ISS begins to catch up to it.  But the ISS can never fully catch it.  It will reach its apogee at a point ahead of the ISS, and begin to repeat the progress, pulling away from the ISS.  Each time this cycle repeats the object will reach apogee further and further ahead of the ISS. ( Now, if you very carefully chose the speed at which you threw the object, you could arrange it so that after X orbits of the ISS, and Y orbits of the object, they both arrive at the same point again.)
It takes a bit to get used to how orbital mechanics behave, as it is not intuitive. 

[Halc]

hrow a ball from the ISS in a way that it will return from the other side ?

Yes, it can be done.

If you throw a ball from the ISS at any time, it will return to the same spot (relative to Earth's inertial frame) each time. Trick is to get both the ISS and the ball to be at that spot at the same time.

Best way to do that is to have both come back after one orbit, which means the ball simply needs to move at the same speed relative to Earth as does the ISS, so just throw it (not hard) almost exactly perpendicular to its motion and it will come back in one orbit, and yes, from the other side.

Another way to to throw it forward really hard into a higher eccentric orbit and get it to orbit once when the ISS takes two trips around. Similarly, one could throw it to the front or rear but no so hard, in which case it will take many trips around before the two sync up, but it will come back always if you wait long enough.

Don't throw it to the rear too hard or it will drop into the atmosphere and konk a poor sheepy on the noggin.