<p>Orbits are all ellipses, so when you throw a baseball you change the orbit of the base ball from your circular ellipse to another ellipse.</p>
<p>If you throw it prograde (in the velocity direction), then you baseball will have an elliptical orbit. It will be closest to the Earth at the point at which you threw it, and furthest from the Earth (and higher than the circular orbit) at 180 degrees. So throwing prograde will never make the baseball deorbit.
The speed of the baseball will now not be constant.  It will be faster than the circular orbit speed at the lowest point in the orbit, but slower than the circular orbit speed at the highest point.</p>
<p>This is your misconception: Adding velocity doesn't make the ball to a lower orbit.  Instead, adding velocity makes the ball go to a higher orbit, which in turn reduces the speed of the ball.</p>
<p>Throwing retrograde (wake direction) has the opposite effect. The baseball will enter an elliptical orbit that is close to the Earth at 180 degree from the point at which you threw and is, on average at a higher speed.  If you throw retrograde hard enough you can reduce the height at 180 degrees to less than 0, ie the baseball hits the ground.  But you have to throw far far harder than is physically possible, because you and the baseball start out at orbital speeds, about 7km/s so throwing at 10m/s won't be enough to deorbit.</p>
<p>Throwing at the nadir would also just change the baseball's orbit into an elliptical orbit. The baseball would initially approach the Earth, but as it did it would gain speed and then move away from the Earth in an ellipse.  The closest point would be at about 90 degrees ahead of the throwing point. This is actually not a very effective way of deorbiting. It takes a lot harder throw to reduce the height by the same amount that throwing retrograde would. As with the other throws, the ball will pass through the throwing point after going all around the Earth.  But you won't be at the same point again because your orbital period will be different to that of the ball.</p>
<p>Throwing anti-nadir has a similar effect, except now the furthest point is at about 90 degrees, and the ball falls to the closest point at 270 degrees.  It is equally ineffective at de-orbiting or gaining height. This is why nearly all spacecraft manoeuvres happen either in the prograde direction (to add height) or retrograde (to reduce height)</p>
<p>&quot;Bouncing off the atmosphere&quot; is a practical problem not directly connected to orbits. If you enter the atmosphere at the wrong angle, you can actually start to fly and so gain altitude. That's not really connected to the orbital manoeuvres here</p>

CC BY-SA 4.0
2020-11-19T13:58:13.573Z
What speed would we need for the baseball to touch the earth surface when throwing retrograde (ignoring atmosphere)? Do have equations?
Ralf Kleberhoff
CC BY-SA 4.0
2020-11-19T17:48:07.973Z
Yes we have equations.  (It's not called rocket science for nothing) and no doubt the people at space.stackexchange would give you chapter and verse.   Of course, it depends on exactly which low earth orbit you are in. But a retrograde dv of about 100m/s is in the right ball park. More than any human could throw, but you can de-orbit a bullet by fireing a gun backwards.
James K
CC BY-SA 4.0
2020-11-20T05:21:09.230Z
The way I was reading that article, it made no sense whatsoever. But, if I understand you right, it's a two-step process, not just one. To make sure I get it, you speed up to get into a higher elevation, then when you get there, slow down to a proper orbital velocity for that orbit. Right? Thanks!
kmort
CC BY-SA 4.0
2020-11-20T05:25:09.513Z
Yes, adding velocity raises your orbit, which causes your speed to decrease.    A consequence of this is that atmospheric drag on a satellite will remove velocity, and cause the satellite's speed to increase.
James K
CC BY-SA 4.0
2020-11-22T12:03:32.293Z
always good to reference relevant existing answers [How hard do you have to throw something off the ISS to make it deorbit?](https://space.stackexchange.com/q/28002/12102) and [If you throw a baseball from the space station, will it return to you in 90 minutes?](https://space.stackexchange.com/q/26649/12102)
uhoh
CC BY-SA 4.0
2020-11-22T12:04:27.417Z
`-1` Is there scientific truth to the following; can it be supported with links, sources, or mathematics? "'Bouncing off the atmosphere' is a practical problem not directly connected to orbits. If you enter the atmosphere at the wrong angle, you can actually start to fly and so gain altitude. That's not really connected to the orbital manoeuvres here" I want to know how baseballs "start to fly!" Perhaps [put a spin](https://astronomy.stackexchange.com/q/39982/7982) on them?
uhoh
CC BY-SA 4.0
2020-11-22T12:10:00.243Z
Are you just downvoting all my answers now?
James K
CC BY-SA 4.0
2020-11-22T21:05:23.057Z
@JamesK absolutely not! You are quite a prolific answerer and I couldn't possibly keep up. When I do down vote I try to always provide *a specific reason as an actionable item* thereby providing a way to reverse my vote! I do take Stack Exchange answers seriously and when I see an answer that I feel is written in haste and has content that conflicts with what I think is true, I'll make a note of it, and the down vote is the tool that Stack Exchange provides us to draw attention to such things. If there's some science in this baseball bouncing off the atmosphere, let's hear it! If not... edit?
uhoh
CC BY-SA 4.0
2020-11-22T21:09:13.783Z
Also, I stopped by just now for another reason and just saw your comment by chance, I don't seem to have received a notification of your comment. [How @replies works](https://meta.stackexchange.com/q/43019/303080) is still a bit of a mystery to me, but if the `@` autocomplete works, then it's probably necessary if the sending of a notification to the addressed party is desired.
uhoh
CC BY-SA 4.0
2020-11-22T21:16:29.863Z
@JamesK for completeness' sake I'll mention the down vote on another answer here in Astronomy recently, the "throw a spinning satellite to Mars" question. I felt that that answer was opportunistic in that it did not address what the OP was getting at but was simply seen as an opportunity to post an answer anyway. That was born out by the OP's subsequent questions about spacecraft. As far as I can tell, the OPs questions spanning Physics SE, Astronomy SE and Space SE have all since been removed. They wouldn't take "perpetual motion machines don't work" for an answer.
uhoh
CC BY-SA 4.0
2020-11-19T08:40:12.840Z
2020-11-19T08:40:12.840Z
James K
<p>I just read a thought piece about <a href="https://aerospace.org/paper/physics-space-war-how-orbital-dynamics-constrain-space-space-engagements" rel="nofollow noreferrer">what a war in space may look like</a>, and it changed my thoughts on what orbit actually is. From what I read about orbits, it sounds like going faster in the velocity direction will cause you to get to a lower altitude, and going slower will cause you to get to a higher altitude orbit. This feels completely backwards to me, so I tried a thought experiment, but it led me to the questions below.</p>
<p>I'm standing on satellite in a circular low earth orbit, and I want to make my (indestructible) baseball go to the ground without waiting for months or years to de-orbit. If I threw the baseball in the velocity direction, I don't think I could cause enough delta V to make it go fast enough that it would go to a significantly lower orbit. Is that correct?</p>
<p>So instead of throwing it in the velocity direction, if I threw it straight at the earth (nadir), <strong>would it continue to go towards the earth</strong>, or would that just modify the baseball's orbit similar to throwing it in the velocity direction? I remember hearing about something &quot;bouncing off the atmosphere&quot;. That wouldn't come into play with my baseball would it?</p>
<p>If I threw the baseball in the wake direction to try to take a bit of my orbital speed off of it, would it truly get to a higher orbit? Why wouldn't it just fall to the ground?</p>
<p>Bonus question: if I threw it anti-nadir, what happens?</p>

CC BY-SA 4.0
2020-11-19T03:33:31.333Z
Related: https://space.stackexchange.com/questions/38557/whats-the-eccentricity-of-an-orbit-trajectory-falling-straight-down-towards-t/38567?r=SearchResults
Nilay Ghosh
CC BY-SA 4.0
2020-11-19T04:31:21.640Z
Youtube isn't ideal for answers, but about 40 seconds in, this video addresses your question with pictures.   https://www.youtube.com/watch?v=wUgh8Y2JozI&feature=emb_title   You can also, from a concept standpoint, think of what happens if you throw a ball from a high speed train (and ignore air resistance).
userLTK
CC BY-SA 4.0
2020-11-19T08:58:39.060Z
Your opening is the other way around. Going down makes faster, not the opposite, as surprising as it can be.
Alchimista
CC BY-SA 4.0
2020-11-19T23:56:30.367Z
play Kerbal Space Program and all will become clear :-)
Aaron F
CC BY-SA 4.0
2020-11-20T21:55:40.320Z
Or Orbiter.....
James K
<orbit><orbital-mechanics><satellite>
Throwing a baseball from orbit to the earth
kmort
# Throwing a baseball from orbit to the earth

(Asked by: username_0 on 2020-11-19)

I just read a thought piece about [what a war in space may look like](https://aerospace.org/paper/physics-space-war-how-orbital-dynamics-constrain-space-space-engagements), and it changed my thoughts on what orbit actually is. From what I read about orbits, it sounds like going faster in the velocity direction will cause you to get to a lower altitude, and going slower will cause you to get to a higher altitude orbit. This feels completely backwards to me, so I tried a thought experiment, but it led me to the questions below.

I'm standing on satellite in a circular low earth orbit, and I want to make my (indestructible) baseball go to the ground without waiting for months or years to de-orbit. If I threw the baseball in the velocity direction, I don't think I could cause enough delta V to make it go fast enough that it would go to a significantly lower orbit. Is that correct?

So instead of throwing it in the velocity direction, if I threw it straight at the earth (nadir), **would it continue to go towards the earth**, or would that just modify the baseball's orbit similar to throwing it in the velocity direction? I remember hearing about something "bouncing off the atmosphere". That wouldn't come into play with my baseball would it?

If I threw the baseball in the wake direction to try to take a bit of my orbital speed off of it, would it truly get to a higher orbit? Why wouldn't it just fall to the ground?

Bonus question: if I threw it anti-nadir, what happens?

**Tags:** orbit, orbital-mechanics, satellite
> **Comments:**
> **username_1**: Related: https://space.stackexchange.com/questions/38557/whats-the-eccentricity-of-an-orbit-trajectory-falling-straight-down-towards-t/38567?r=SearchResults  
> **username_2**: Youtube isn't ideal for answers, but about 40 seconds in, this video addresses your question with pictures.   https://www.youtube.com/watch?v=wUgh8Y2JozI&feature=emb_title   You can also, from a concept standpoint, think of what happens if you throw a ball from a high speed train (and ignore air resistance).  
> **username_3**: Your opening is the other way around. Going down makes faster, not the opposite, as surprising as it can be.  
> **username_4**: play Kerbal Space Program and all will become clear :-)  
> **username_5**: Or Orbiter.....  

---

## 1 answers

### Answer by username_5 on 2020-11-19. Score: 4 | Accepted answer

Orbits are all ellipses, so when you throw a baseball you change the orbit of the base ball from your circular ellipse to another ellipse.

If you throw it prograde (in the velocity direction), then you baseball will have an elliptical orbit. It will be closest to the Earth at the point at which you threw it, and furthest from the Earth (and higher than the circular orbit) at 180 degrees. So throwing prograde will never make the baseball deorbit.
The speed of the baseball will now not be constant. It will be faster than the circular orbit speed at the lowest point in the orbit, but slower than the circular orbit speed at the highest point.

This is your misconception: Adding velocity doesn't make the ball to a lower orbit. Instead, adding velocity makes the ball go to a higher orbit, which in turn reduces the speed of the ball.

Throwing retrograde (wake direction) has the opposite effect. The baseball will enter an elliptical orbit that is close to the Earth at 180 degree from the point at which you threw and is, on average at a higher speed. If you throw retrograde hard enough you can reduce the height at 180 degrees to less than 0, ie the baseball hits the ground. But you have to throw far far harder than is physically possible, because you and the baseball start out at orbital speeds, about 7km/s so throwing at 10m/s won't be enough to deorbit.

Throwing at the nadir would also just change the baseball's orbit into an elliptical orbit. The baseball would initially approach the Earth, but as it did it would gain speed and then move away from the Earth in an ellipse. The closest point would be at about 90 degrees ahead of the throwing point. This is actually not a very effective way of deorbiting. It takes a lot harder throw to reduce the height by the same amount that throwing retrograde would. As with the other throws, the ball will pass through the throwing point after going all around the Earth. But you won't be at the same point again because your orbital period will be different to that of the ball.

Throwing anti-nadir has a similar effect, except now the furthest point is at about 90 degrees, and the ball falls to the closest point at 270 degrees. It is equally ineffective at de-orbiting or gaining height. This is why nearly all spacecraft manoeuvres happen either in the prograde direction (to add height) or retrograde (to reduce height)

"Bouncing off the atmosphere" is a practical problem not directly connected to orbits. If you enter the atmosphere at the wrong angle, you can actually start to fly and so gain altitude. That's not really connected to the orbital manoeuvres here

> **Comments:**
> **username_6**: What speed would we need for the baseball to touch the earth surface when throwing retrograde (ignoring atmosphere)? Do have equations?  
> **username_5**: Yes we have equations.  (It's not called rocket science for nothing) and no doubt the people at space.stackexchange would give you chapter and verse.   Of course, it depends on exactly which low earth orbit you are in. But a retrograde dv of about 100m/s is in the right ball park. More than any human could throw, but you can de-orbit a bullet by fireing a gun backwards.  
> **username_0**: The way I was reading that article, it made no sense whatsoever. But, if I understand you right, it's a two-step process, not just one. To make sure I get it, you speed up to get into a higher elevation, then when you get there, slow down to a proper orbital velocity for that orbit. Right? Thanks!  
> **username_5**: Yes, adding velocity raises your orbit, which causes your speed to decrease.    A consequence of this is that atmospheric drag on a satellite will remove velocity, and cause the satellite's speed to increase.  
> **username_7**: always good to reference relevant existing answers [How hard do you have to throw something off the ISS to make it deorbit?](https://space.stackexchange.com/q/28002/12102) and [If you throw a baseball from the space station, will it return to you in 90 minutes?](https://space.stackexchange.com/q/26649/12102)  
> **username_7**: `-1` Is there scientific truth to the following; can it be supported with links, sources, or mathematics? "'Bouncing off the atmosphere' is a practical problem not directly connected to orbits. If you enter the atmosphere at the wrong angle, you can actually start to fly and so gain altitude. That's not really connected to the orbital manoeuvres here" I want to know how baseballs "start to fly!" Perhaps [put a spin](https://astronomy.stackexchange.com/q/39982/7982) on them?  
> **username_5**: Are you just downvoting all my answers now?  
> **username_7**: @JamesK absolutely not! You are quite a prolific answerer and I couldn't possibly keep up. When I do down vote I try to always provide *a specific reason as an actionable item* thereby providing a way to reverse my vote! I do take Stack Exchange answers seriously and when I see an answer that I feel is written in haste and has content that conflicts with what I think is true, I'll make a note of it, and the down vote is the tool that Stack Exchange provides us to draw attention to such things. If there's some science in this baseball bouncing off the atmosphere, let's hear it! If not... edit?  
> **username_7**: Also, I stopped by just now for another reason and just saw your comment by chance, I don't seem to have received a notification of your comment. [How @replies works](https://meta.stackexchange.com/q/43019/303080) is still a bit of a mystery to me, but if the `@` autocomplete works, then it's probably necessary if the sending of a notification to the addressed party is desired.  
> **username_7**: @JamesK for completeness' sake I'll mention the down vote on another answer here in Astronomy recently, the "throw a spinning satellite to Mars" question. I felt that that answer was opportunistic in that it did not address what the OP was getting at but was simply seen as an opportunity to post an answer anyway. That was born out by the OP's subsequent questions about spacecraft. As far as I can tell, the OPs questions spanning Physics SE, Astronomy SE and Space SE have all since been removed. They wouldn't take "perpetual motion machines don't work" for an answer.  

---

