Orbit Physics Question

If a space shuttle astronaut took a softball outside and tossed it
towards earth, what would happen?

Would the softball start falling towards earth and then increase in
orbital velocity until it reached equilibrium at a lower altitude and
then stop falling? (I realize eventually it would slow down anyway from
drag and re-enter, but let's ignore that detail.)

Or would it just continue falling towards earth and reenter at its
original orbital velocity?

Now suppose the softball was tossed away from earth...what would happen
to its orbital velocity?

Finally, what if the softball was tossed more or less eastbound, in
exactly the same direction as the shuttle's orbit, straight ahead.
Would the increased velocity of the softball (relative to the shuttle)
cause the softball altitude to decrease? (or increase...)

Jessica wrote:
If a space shuttle astronaut took a softball outside and tossed it
towards earth, what would happen?

Would the softball start falling towards earth and then increase in
orbital velocity until it reached equilibrium at a lower altitude and
then stop falling? (I realize eventually it would slow down anyway from
drag and re-enter, but let's ignore that detail.)

Or would it just continue falling towards earth and reenter at its
original orbital velocity?

The result may seem a bit counterintuitive, but ignoring drag, the
softball will drop toward Earth, then speed up, then rise back to the
astronaut's altitude (but in front), then slow down, then drop back
toward the astronaut, arriving back at the original location exactly one
orbit later. As seen by the astronaut, the trajectory is an ellipse with
the long axis in the direction of the astronaut's velocity, and with the
long axis twice as long as the short axis.

The dimensions of the ellipse are determined by the velocity imparted by
the throw. For each m/s imparted by the throw, the long axis of the
ellipse will be 3.6 km and the short axis half that.


Now suppose the softball was tossed away from earth...what would happen
to its orbital velocity?

Mirror-image of the previous case. The softball's trajectory relative to
the astronaut will describe an ellipse, except that the softball will
initially travel above and behind the astronaut.

Finally, what if the softball was tossed more or less eastbound, in
exactly the same direction as the shuttle's orbit, straight ahead. Would
the increased velocity of the softball (relative to the shuttle) cause
the softball altitude to decrease? (or increase...)

The softball would end up in an elliptical orbit with the perigee at the
altitude of the astronaut. The apogee will be 180 degrees opposite the
point of the throw and will be 3.6 km higher for each m/s imparted by
the throw. Since the orbit is higher it will have a longer period, with
the softball falling behind the astronaut at about 17 km per orbit.

One other thing of course, it depends very much on the mass of the
person/craft doing the throwing as against the mass of the ball, as there
has to be an opposite effect on that mass as well.


Brian

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"Jorge R. Frank" wrote in message
...
Jessica wrote:
If a space shuttle astronaut took a softball outside and tossed it
towards earth, what would happen?

Would the softball start falling towards earth and then increase in
orbital velocity until it reached equilibrium at a lower altitude and
then stop falling? (I realize eventually it would slow down anyway from
drag and re-enter, but let's ignore that detail.)

Or would it just continue falling towards earth and reenter at its
original orbital velocity?

The result may seem a bit counterintuitive, but ignoring drag, the
softball will drop toward Earth, then speed up, then rise back to the
astronaut's altitude (but in front), then slow down, then drop back toward
the astronaut, arriving back at the original location exactly one orbit
later. As seen by the astronaut, the trajectory is an ellipse with the
long axis in the direction of the astronaut's velocity, and with the long
axis twice as long as the short axis.

The dimensions of the ellipse are determined by the velocity imparted by
the throw. For each m/s imparted by the throw, the long axis of the
ellipse will be 3.6 km and the short axis half that.


Now suppose the softball was tossed away from earth...what would happen
to its orbital velocity?

Mirror-image of the previous case. The softball's trajectory relative to
the astronaut will describe an ellipse, except that the softball will
initially travel above and behind the astronaut.

Finally, what if the softball was tossed more or less eastbound, in
exactly the same direction as the shuttle's orbit, straight ahead. Would
the increased velocity of the softball (relative to the shuttle) cause
the softball altitude to decrease? (or increase...)

The softball would end up in an elliptical orbit with the perigee at the
altitude of the astronaut. The apogee will be 180 degrees opposite the
point of the throw and will be 3.6 km higher for each m/s imparted by the
throw. Since the orbit is higher it will have a longer period, with the
softball falling behind the astronaut at about 17 km per orbit.

Jorge R. Frank wrote:

Jessica wrote:
If a space shuttle astronaut took a softball outside and tossed it
towards earth, what would happen?

The result may seem a bit counterintuitive, but ignoring drag, the
softball will drop toward Earth, then speed up, then rise back to the
astronaut's altitude (but in front), then slow down, then drop back
toward the astronaut, arriving back at the original location exactly one
orbit later. As seen by the astronaut, the trajectory is an ellipse with
the long axis in the direction of the astronaut's velocity, and with the
long axis twice as long as the short axis.

Orbital mechanics are certainly weird, I tried a docking sim with the ISS,
and could never get the Shuttle into a proper approach corridor. You don't
just thrust towards a target. The fact that you can't throw anything away
is why NASA was reluctant to jettison stuff. Luckily, drag enters in when
the object is fluffy, and drag reduces orbital speed and altitude. Once
the Russians showed us that, we've jettisoned some pretty big (but still
low mass/area) things.

Oddly enough, if you release something big and fluffy below ISS, it will
move further below and ahead of ISS, as the decreased altitude decreases
its orbital period.

In sci.space.shuttle message , Fri, 15
May 2009 22:12:31, Jessica posted:
If a space shuttle astronaut took a softball outside and tossed it
towards earth, what would happen?

Read Arthur C. Clarke's short story 'Jupiter Five' (1951).

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wrote:
Jorge R. Frank wrote:

Jessica wrote:
If a space shuttle astronaut took a softball outside and tossed it
towards earth, what would happen?

The result may seem a bit counterintuitive, but ignoring drag, the
softball will drop toward Earth, then speed up, then rise back to the
astronaut's altitude (but in front), then slow down, then drop back
toward the astronaut, arriving back at the original location exactly one
orbit later. As seen by the astronaut, the trajectory is an ellipse with
the long axis in the direction of the astronaut's velocity, and with the
long axis twice as long as the short axis.

Orbital mechanics are certainly weird, I tried a docking sim with the ISS,
and could never get the Shuttle into a proper approach corridor. You don't
just thrust towards a target.

Right. The trick is to recognize which direction you're approaching the
target from and to modify your approach techniques appropriately. The
shuttle performs +Vbar approaches to ISS, in which the orbiter is in
front of ISS in a tail-down, belly-to-velocity attitude, and approaching
along the direction of the ISS velocity vector. Thrusting toward the
target to start the approach is therefore a retrograde burn, which
causes the orbiter to drop into a lower elliptical orbit. So the CDR
periodically applies radial-up thrust to "hop" in along the Vbar. In the
tail-down attitude these hops use the +X RCS jets (aft end of the
vehicle, thrusting forward). As a bonus, the orbiter's +X jets are
canted upward a bit, so they provide a bit of "free" braking to keep the
rate under control as well.

On May 18, 2:49*am, "Jorge R. Frank" wrote:
wrote:
Jorge R. Frank wrote:

Jessica wrote:
If a space shuttle astronaut took a softball outside and tossed it
towards earth, what would happen?

The result may seem a bit counterintuitive, but ignoring drag, the
softball will drop toward Earth, then speed up, then rise back to the
astronaut's altitude (but in front), then slow down, then drop back
toward the astronaut, arriving back at the original location exactly one
orbit later. As seen by the astronaut, the trajectory is an ellipse with
the long axis in the direction of the astronaut's velocity, and with the
long axis twice as long as the short axis.

Orbital mechanics are certainly weird, I tried a docking sim with the ISS,
and could never get the Shuttle into a proper approach corridor. *You don't
just thrust towards a target.

Right. The trick is to recognize which direction you're approaching the
target from and to modify your approach techniques appropriately. The
shuttle performs +Vbar approaches to ISS, in which the orbiter is in
front of ISS in a tail-down, belly-to-velocity attitude, and approaching
along the direction of the ISS velocity vector. Thrusting toward the
target to start the approach is therefore a retrograde burn, which
causes the orbiter to drop into a lower elliptical orbit. So the CDR
periodically applies radial-up thrust to "hop" in along the Vbar. In the
tail-down attitude these hops use the +X RCS jets (aft end of the
vehicle, thrusting forward). As a bonus, the orbiter's +X jets are
canted upward a bit, so they provide a bit of "free" braking to keep the
rate under control as well.

Your answer on the sci.space.tech forum on a specific topic was
particularly stupid,as that forum is moderated and with no chance to
respond,I get to correct a few things here using this thread.


On May 16, 10:07 pm, "Jorge R. Frank" wrote:

Nice try. Astrodynamicists already account for the apparent motion of
the orbital plane due to Earth's rotation. The precession of the line of
nodes is *on top of* that, and the effect is quite real.


This is in reference to a Sun synchronous orbit -

http://www.aero.org/publications/gil...mages/Ch1g.gif

The observed 'precession' in a satellite in this type of orbit is not
intrinsic to the satellite itself in the same way the 'precession' in
a Foucault's pendulum in intrinsic to the pendulum itself but rather
an effect of planetary dynamics,in terms of the pendulum,the Earth
turns beneath it in its daily rotation whereas the orbital version is
the turning Earth as it moves along its orbital circumference in a
specific way.

Astrodynamicists indeed !,the Earth orbits the Sun in a specific way
and this additional orbital detail is what registers as satellite
'precession' as the Earth turns with respect to the central Sun ,along
its orbital circumference,and in a counter-clockwise direction to
daily rotation.

These astrodynamicists are not doing their jobs for without the
orbital specific,landing spacecraft of a planet such as Mars will
always be a hit and miss affair without the complete details of
orbital dynamics.The problem is nonsensical responses like your which
indicate just how poor understanding of planetary dynamics actually
is.

"Dr J R Stockton" wrote in message
nvalid...
In sci.space.shuttle message , Fri, 15
May 2009 22:12:31, Jessica posted:
If a space shuttle astronaut took a softball outside and tossed it
towards earth, what would happen?

Read Arthur C. Clarke's short story 'Jupiter Five' (1951).

I prefer Niven's description of orbital mechanics. ;-)

Jeff
--
"Take heart amid the deepening gloom
that your dog is finally getting enough cheese" - Deteriorata - National
Lampoon

So do I. I just wish I could recall it from memory, rather than have to
look it up all the time.

One of the more interesting "worlds" I've seen in sci-fi.

--
Greg Moore
Ask me about lily, an RPI based CMC.

"Jeff Findley" wrote in message
...

"Dr J R Stockton" wrote in message
nvalid...
In sci.space.shuttle message , Fri, 15
May 2009 22:12:31, Jessica posted:
If a space shuttle astronaut took a softball outside and tossed it
towards earth, what would happen?

Read Arthur C. Clarke's short story 'Jupiter Five' (1951).

I prefer Niven's description of orbital mechanics. ;-)

Jeff
--
"Take heart amid the deepening gloom
that your dog is finally getting enough cheese" - Deteriorata - National
Lampoon

"Greg D. Moore (Strider)" wrote in message
m...


So do I. I just wish I could recall it from memory, rather than have to
look it up all the time.

Just in case others havn't read Niven, from Larry Niven's The Integral
Trees, "Forward takes you out, out takes you back, back takes you in, and in
takes you forward."

One of the more interesting "worlds" I've seen in sci-fi.

Niven came up with a good one there. I'll have to re-read those sometime.
I recently re-read the Frank Herbert Dune books and read, for the first
time, the prequel done by his son and someone else.

Jeff
--
"Take heart amid the deepening gloom
that your dog is finally getting enough cheese" - Deteriorata - National
Lampoon