Please Explain the Velocity Numbers

[pleasedebunkme]

With all due respect and humility, I have two questions: 

1.  Back in 1969, did NASA forget to include the Moon’s orbital velocity when it computed Apollo 11’s return velocity to the Earth?

2.  After the Trans Earth Injection burn, Apollo 11 was traveling at escape velocity with respect to the Moon, and it was also traveling at escape velocity with respect to the Earth, so when and how did Apollo 11 regain its alleged elliptical orbit around the Earth that allowed it to use the alleged re-entry corridor?   

According to the NASA logbook, Apollo 11 was orbiting the Moon at 1,624 meters per second just before the Trans Earth Injection burn that would increase the velocity by 1,000 meters per second, for a total velocity of approximately 2,624 meters per second, which velocity would be relative to the Moon.  The approximate escape velocity while in lunar orbit would be 2,400 meters per second.  The approximate escape velocity when you are orbiting the Earth at the distance of the Moon is approximately 1400 meters per second.   As such, after the Trans Earth Injection burn, Apollo 11’s new velocity of 2,624 meters per second while orbiting the Moon would exceed escape velocity, relative to the Moon and also the Earth.  This velocity of 2,624 meters per second relative to the Moon would translate to approximately 3,624 meters per second relative to the Earth, because the Moon orbits the Earth at an average velocity of approximately 1000 meters per second.  When Apollo 11 started its return voyage at the velocity of 3,634 meters per second relative to the Earth, it was going escape velocity, and it would never slow down to orbital velocity relative to the Earth, which means it was never in orbit, which means the re-entry corridor cannot work.  Why am I wrong?  Where is the flaw in my argument? 

Please note that my reading of various posts under the hoax theory this morning has revealed that this new website forum has become more harsh than the old forum, and much more ad hominem.  Please spare me the insults.  I would just like to focus on the numbers.  Science works better when you focus on the facts.  I am certain that all of you have already given due consideration to the Moon's orbital velocity issue, and you have researched all aspects of the Apollo voyages.  Obviously, I have to be wrong.  But, on the NASA logbooks that are posted online, there is no indication of the Moon's orbital velocity being included in Apollo 11's return velocity numbers.  Please help me figure it out.  Thank you!   

[Glom]

Two things you haven't considered:
1) The speed is at cutoff of the TEI burn, which is at pericynthion.  From that point, the Moon is pulling it back and slowing it down until it gets far enough away that the weight from Earth is greater and it starts increases its speed towards Earth.
2) It doesn't need orbital velocity with respect to Earth because it isn't entering Earth orbit.  It's going straight for re-entry.

Also, I think you've got your vectors wrong.  The TEI burn was retrograde with respect to the Moon's orbit of Earth I think so in fact the speed relative to Earth is more like 1600m/s, which is about escape speed at that distance.

[scooter]

...standing by for some 3 body problem lessons.

Unlike the trip to the Moon, the trip home is pretty much aiming at a stationary target, only the departure point is rotating around said target. They make their TEI burn pretty much opposite the Earth on the Moon's far side, and the Moon's gravity remains the dominant force for some time after that.
Then, don't forget the Sun's influence...they don't call this rockets science for nothing, and we are blessed with an unusual concentration of such experts right here.

[pleasedebunkme]

Thank you, Glom.  I greatly appreciate your bringing up topics of discussion on this point.  I believe “pericynthion” is an orbital term.  Therefore, “pericynthion” does not exist unless you are first in orbit, around something.  My questions would be:  When did this orbit occur? And how did this orbit occur?  And yes, I agree that the Moon’s gravity would have an effect on Apollo 11.  In fact, not only would the Moon slow the command module down, but the Moon would also pull the command module along its orbital path.  However, I do not believe it is possible for the Moon’s gravity to slow down Apollo 11 enough to allow Apollo 11 to regain orbital velocity relative to the Earth.  But, assuming I might be wrong, then there had to be a point at which Apollo 11 regained orbital velocity relative to the Earth.  That is the answer I am seeking.  And, I do not mean to argue, but I do believe that Apollo 11 needed to be in a flat elliptical orbit for the re-entry corridor to work.  If Apollo 11 were traveling escape velocity as it approached the Earth, then it would either collide at high velocity, or else it would fly right on by, but either way the command module would not have swung around to the antipode/perigee side of the Earth unless it were in elliptical orbit.  But, again, thank you for responding.  Your answer helps me put my own questions into perspective.

[Glom]

Thank you, Glom.  I greatly appreciate your bringing up topics of discussion on this point.  I believe “pericynthion” is an orbital term. 

Pericynthion is the lowest point of an orbit of the Moon (equivalent to perigee)

Therefore, “pericynthion” does not exist unless you are first in orbit, around something.

Well no. Even a flyby (eg Apollo 13) would have a pericynthion because it would have a lowest point in the Moon dominated portion of its trajectory.

However, I do not believe it is possible for the Moon’s gravity to slow down Apollo 11 enough to allow Apollo 11 to regain orbital velocity relative to the Earth. 

That's an assertion. Show your maths.

But even so, I refer you my previous response to you. The spacecraft does not require a reduction in speed to that of a closed orbit because it heads straight into the atmosphere where it loses all orbital energy.

And, I do not mean to argue, but I do believe that Apollo 11 needed to be in a flat elliptical orbit for the re-entry corridor to work. 

Any orbit is going to be flat. It is dictated by conservation of angular momentum.

If Apollo 11 were traveling escape velocity as it approached the Earth, then it would either collide at high velocity, or else it would fly right on by, but either way the command module would not have swung around to the antipode/perigee side of the Earth unless it were in elliptical orbit.  But, again, thank you for responding.  Your answer helps me put my own questions into perspective.

Nothing about speed prevents the spacecraft from intersecting the atmosphere.

[gillianren]

However, I do not believe . . . .

. . . But I do believe . . . .

With all due respect, so what?  Why do your beliefs matter?  What matters is what you can show, and you aren't doing that.  You are stating a bald supposition, and you haven't explained why anyone should agree with it.  Can you show the math?  If you can't, no one has any reason to believe you.  And let me assure you that this is not an ad hominem attack; it's true no matter who you are.  If you can't show the math, all we have is one person's opinion.

[pleasedebunkme]

Gillianren, I appreciate your response.  But, you are getting off topic here.  My first question was simply a point of information to discover where in the Apollo 11 logbook they included the Moon’s orbital velocity.  Your response does not help me figure that out, but I wish you would.  It is not about belief, it is about velocity, and in particular escape velocity.  If Apollo 11 were traveling at escape velocity when it came back to Earth, then the re-entry corridor would not work.  I gave my numbers in my first post.  As of this point in time, nobody has shown how my numbers are wrong.  I am asking for any information on how my numbers might be wrong.  Because, if my numbers might be correct, then the re-entry corridor did not happen for Apollo 11.  So, where am I wrong?

[Glom]

You provided some speeds, but you haven't demonstrated why they would make reentry impossible.

I also pointed out to you that you got some reference frame calculations wrong so you might need to revisit your maths before asserting you've demonstrated your point.

[pleasedebunkme]

Just for reference, I wanted to remind everyone of a prior post on the old blog: 

______ 


Re: Antipode and Lifting Characteristics
Post by bob on Jul 18, 2011, 11:39pm

Just to prove my point that the Apollo transearth trajectories were elliptical orbits…

Vesc = SQRT[2*GM/R]

At entry interface, R = 6378140+(400000*0.3048) = 6,500,060 m

Therefore,

Vesc = SQRT[2*3.986005E+14/6500060] = 11,074.5 m/s = 36,334 ft/s

If you look at the following table,

http://history.nasa.gov/SP-4029/Apollo_18-40_Entry_Splashdown_and_Recovery.htm

You’ll see that all the returning Apollo spacecraft had velocities below 36,334 ft/s at Earth entry.

________ 

So, what I am saying is that it would appear that the stated orbital velocities of the Apollo command modules upon Earth re-entry would be incorrect if the velocity of the Moon were to be included in the equations.  So, I am merely asking this:  Where in the logbook did NASA include the Moon's orbital velocity?   

[Glom]

The entry speeds were all close to that value. The spacecraft wasn't quite at escape energy, just very close, so I see nothing inconsistent in the table with Bob's rough calculations.

Converting velocities relative to the Moon to velocities relative to Earth is simple enough. It's basic vector arithmetic.

[scooter]

I'm not sure what the speed of the Moon in it's orbit has to do with how fast the CSM had to go in order to attain it's TEI trajectory.

Am I missing something?

[PUshift]

...If Apollo 11 were traveling escape velocity as it approached the Earth, then it would either collide at high velocity, or else it would fly right on by...

Aiming at earth perigee of e.g. 40km will presumably avoid both fatal scenarios you describe as only possible. I would call this argument by polarization. There is a middle way and it is the feasable one.


Hello to the Forum, lurking since many years, with thanks, cheers and respect to the authority of knowledge and personality of the majority of the forum members. The chances are low to improve value because every issue is always known better by somebody else. Always and anyway That´s why I appreciate it so much.

[gillianren]

But, you are getting off topic here.

On the contrary.  You are making an assertion, and you have shown no basis for it.  Maybe you should start by presenting your math instead of just saying, "Prove me wrong!"  Because the numbers are out there if you know where to look.

[pleasedebunkme]

I am asking two different questions.  Both questions stem from that point in time when the Trans Earth Injection burn ended, but the two points are different. 

First, at the end of the Trans Earth Injection Burn, Apollo 11 had three different relative velocities, which were approximately:  (1) 2,624 meters per second relative to the Moon; (2) 3,624 meters per second relative to the Earth; and (3) 33,044 meters per second relative to the Sun.  For purposes of my question at this time, the Apollo 11 velocity relative to the Sun is irrelevant.  But, what appears to have happened is that NASA completely forgot about the velocity relative to the Earth, and based all of its velocity calculations on the velocity relative to the Moon.  You can look at the logbook and see that all of the velocities that were reported on the Apollo 11 return voyage were stated relative to the Moon.  There is no adjustment of the Apollo 11 velocity to reflect the orbital velocity of the Moon.  I am asking whether any of you might know where this adjustment took place.  My point is that if the actual velocity of Apollo 11 relative to the Earth was 1,000 meters per second higher than NASA reported, then the re-entry corridor would not have worked.   

Second, at the end of the Trans Earth Injection burn, Apollo 11 was traveling at escape velocity relative to the Moon and relative to the Earth.  But, we know (thanks to Bob’s earlier post in the old forum) that Apollo 11 was in an elliptical orbit at the point of the Earth re-entry corridor.  So, there had to be some point in time, in the journey home, that Apollo 11 slowed down enough to re-enter orbit.  I am trying to find out when that point in time occurred.         

And, with respect to PUshift, I appreciate your input, but it appears that you agreed with me.  You expressed the need to aim at a “perigee” point.  You do not get a perigee point unless you are in orbit, so that is what I am trying to say.  Apollo 11 needed to be traveling less than escape velocity in order for the re-entry corridor to work, because Apollo 11 needed to be in orbit.  (i.e. the perigee point needs to be inside Earth’s atmosphere).  I am just trying to figure out when Apollo 11 acquired that orbit.  It was traveling at escape velocity when it was near the Moon, so when did Apollo 11 fall into orbit around the Earth?   

[Glom]

I got a few lines into your post and saw that you ignored my first point about your mistaken conversion to the geocentric frame. The velocity of the spacecraft at TEI is against the orbit of the Moon.

Correct that first then we'll move on to the next issue.