I don’t know if man went to the moon in the sixties

[Echnaton]

I may have his pdf rant in my download folder.  I'll post it later if someone else doesn't

Apparently even the computer rejected DAKDAK's incomprehensible rant.

[VincentMcConnell]

3.   The trajectory of the Apollo missions is nothing like spacecraft go to the moon today. Today spacecraft going to the moon make several increasingly large earth orbits not a crazy “8” trajectory.

I would cover everything you posted, but I think everyone else already did this. Since Orbital Mechanics has lately been my really big interest in spaceflight, I can handle this one. haha.
Actually, the most efficient Lunar Orbit Rendezvous pattern would be this "figure 8" which you speak of. Basically, the spacecraft is in what is called a "parking orbit" around Earth. It is basically sitting there to await what's called a Hohmann Transfer, or, in this case, "Trans Lunar Injection". The burn is a prograde burn that usually is fairly long. Someone here might be able to give you the exact TLI burn time. What it means is to burn in the direction of travel, adding velocity. For Apollo, it was 25,000fps to 35,000 fps (feet per second). So, about 1,000 feet per second of Delta-V. Pretty big burn, actually.
Anyway, when you add velocity to an orbit, you boost into a higher Apogee. To entertain hoaxers, yes, Apollo was actually in Earth Orbit (technically) the entire time!
Once you've done this, the further you get from Earth, you slow down. With the trajectory sent out beyond the Moon's orbital altitude, you basically just coast along until you get pulled in my the moon's gravity, or, enter it's SOI (sphere of influence).
Then, you'd make two more burns. LOI₁ and LOI₂ (Collins). They "drop" you into Lunar Orbit. Once there, after the desired orbits, you make another burn called T.E.I., or TRANS-EARTH injection.
The whole flight plan looks like a figure 8 on paper, although it is a little more complex than that.

I would say that this is the most efficient way to go to the moon (at least for lunar orbital missions.) So, I don't know where you got your information in the OP.

[VincentMcConnell]

8.   The  Lem was made of Tin foil, Mylar and tape the abort procedure was to bail out in space

It was actually the "LM". The word "excursion" was dropped before the LM every even flew. Anyway, onto your point. The Lunar Module was not made of tin-foil. In fact, you used the word in your post. It was made (the skin and thermal protection at least) of MYLAR. It's a much more heavy duty material that offers great thermal protection. The entire LM was not made of it, though, just the covering on the outside. Any tape you may have seen was actually "engineering" tape. The LM didn't have to be as stable as the Saturn V. It was designed ONLY for flight in space.

Oh, by the way, here's some heavy aluminum tape that was used to fix an airplane.


Is that faked, too?

If by "Abort Procedure", you meant the abort during landing, you're incorrect. The abort procedure for the Lunar Module was to do a "fire in the hole" abort. Basically, the ascent stage ignited the engine and blasts away from the descending DPS before it even gets close enough to touchdown. During a flight, however, there were only two methods of abort.

1.) Direct Abort - CSM fires the engine retrograde mid-course to take the spacecraft(s) back to Earth.
2.) Free Return Abort - The Spacecraft(s) fly all the way around the moon, using its gravity as a slingshot to get back to Earth. [This method was used on Apollo 13].

Apollo was real.

[Count Zero]

Good illustration, Vince!  <right-click aaand save>

As you've probably already figured-out by now, Dakdak has gone bye-bye.  As he was running for it, he tried to edit all of his posts to erase the copious evidence of his idiocy.  Fortunately, some bright sparks were able to reconstruct most of his post and LO restored them for posterity.

Don't be late for the party, next time! 

[VincentMcConnell]

As you've probably already figured-out by now, Dakdak has gone bye-bye.  As he was running for it, he tried to edit all of his posts to erase the copious evidence of his idiocy.  Fortunately, some bright sparks were able to reconstruct most of his post and LO restored them for posterity.
Don't be late for the party, next time! 

Darn! Yeah, I came to lurk today since I didn't know my account was actually active. I tried logging in and it just worked. I'm glad to be back and I've learned A LOT since my last visit. I guess I'll have to wait for the next hoaxer to come around.

[ka9q]

Actually, the most efficient Lunar Orbit Rendezvous pattern would be this "figure 8" which you speak of. Basically, the spacecraft is in what is called a "parking orbit" around Earth. It is basically sitting there to await what's called a Hohmann Transfer...

Actually, there are multiple meanings of "most efficient" here. Engineering is all about making tradeoffs. Everything depends on how you define "optimum".

Any lunar mission needs propellant to get there. Within limits you can get there faster by burning more propellant, or you can save propellant by taking a more leisurely trip. But a manned lunar mission has other constraints: it has to carry substantial amounts of food, LiOH, water, hydrogen and oxygen to keep the crew alive, and the longer the trip the more of these consumables you'll need. The increase can easily cut deep into your propellant mass savings from going more slowly.

Unmanned missions have considerably more flexibility because crew consumables (and boredom) aren't issues. So a Hohmann transfer isn't necessarily the cheapest possible way to get to the moon. If somebody could find a cheaper way that takes months instead of days, that would be a non-starter for a human flight but entirely practical for a robot.

Such a way has been found: the use of ion rockets.

Ion drives achieve extremely high Isps compared to chemical rockets, but they have an Achilles heel: very low thrust. You can't use them in conventional bang-bang (impulsive) maneuvers like a Hohmann transfer. You have to spiral your way out with lots of long (often continuous) burns that actually require more total delta-V than the Hohmann impulses, but the ion engine can easily provide that extra delta-V and more. But it'll still take you months to get there, and that just ain't acceptable for a human crew.

So "efficiency" is highly context-dependent.

[VincentMcConnell]

I was talking about a manned LOR profile. A Hohmann transfer is also a fairly basic approach, but like you said, mass and things matter.

[Bob B.]

Since Orbital Mechanics has lately been my really big interest in spaceflight, I can handle this one. haha.

That is one of my primary interests as well.

It is basically sitting there to await what's called a Hohmann Transfer, or, in this case, "Trans Lunar Injection".

Apollo actually used what is called a one-tangent burn, which is a faster trajectory than Hohmann transfer.  A Hohmann transfer to the Moon would take about ten days to get there.  Surprisingly, the extra delta-V needed to cut the journey down from 10 days to 3 days is only about 20-25 m/s.

[VincentMcConnell]

Ah yes, I see the difference there. Nice website, Bob.

[ka9q]

Yes, that's an excellent page, Bob.

I think you're off by a factor of two on your transfer time. 10 days would be the time for a full orbit in the transfer ellipse, but you only take half an orbit to get there.

If we approximate the moon as having no mass and a circular 384,400 km orbit (its semi-major axis), a transfer orbit with a perigee altitude of 150 km (about as low as you could possibly go) and an apogee radius of 384,400 km would have a semi-major axis of (384,400 + 6378 + 150)/2 = 195,464 km. That has a mean motion of

n = 2*pi*sqrt(GMe/a³)
   = 2*pi*sqrt(398,600.4418 / 195,464³) rev/sec
   = ...
   = 860,025 seconds/orbit (9.95 days). Half that is 4.98 days.

That fits with Kepler's 3rd law; the transfer orbit has roughly half the semi-major axis of the moon, so its period would be (1/2)^3/2 that of the moon (27.8 days), or about 9.83 days, close to my 9.95. (Besides the perigee altitude, another difference is that the relevant gravitational parameter for the moon's period is the sum of the gravitational parameters for the earth and moon, since they orbit their common barycenter.)

BTW, you should probably clarify on your page that your formula for mean motion, n = sqrt(mu/a³), is in radians/unit time, not revolutions/unit time as usually given. So you have to multiply by 2 pi to get revolutions.

[Bob B.]

I think you're off by a factor of two on your transfer time. 10 days would be the time for a full orbit in the transfer ellipse, but you only take half an orbit to get there.

You are correct.  I calculated the period and then forgot to divide by two.

[ka9q]

You are correct.  I calculated the period and then forgot to divide by two.

Ah ha! I knew that a small increase in delta-V beyond a minimum-energy Hohmann transfer could shave off quite a bit of transfer time, but I didn't think the effect was as great as reducing 10 days to 3!

Apollo lunar trajectories are easy to understand compared to some that have more recently become routine with unmanned probes. One of my favorite examples is the STEREO mission. Two spacecraft, launched on the same launcher, are now on opposite sides of the sun in very different orbits (one moving ahead of the earth, one falling behind) because they followed slightly different trajectories on their first lunar flybys. One passed close enough to be immediately slingshotted into an earth/moon escape trajectory and heliocentric orbit; the other remained in earth orbit for some time until a subsequent lunar flyby slingshotted it to escape in the opposite direction.

An even better example was the repurposing of the Themis B and C satellites as Artemis P1 and P2 by using the earth/moon L2 Lagrange point.

It's quite literally "applied chaos", as in chaos theory. This is arguably the only real fundamental innovation in space navigation since the Apollo days. Because they don't have analytical solutions they had to wait for better computing facilities. I believe the first actual use of a gravity slingshot maneuver by a spacecraft was Mariner 10's shuttling between Mercury and Venus in 1973-75, followed soon after by the Pioneer 10/11 and Voyager 1/2 tours of the gas giants. Now these interplanetary billiards games are absolutely routine.

[chrisbobson]

I don't know if man went to the moon in the sixties or not, but the record of the Apollo missions seems to be completely false

Here are some of the reasons I believe this
1.   The Command Module being only 210 cubic feet would not fit (3) men all the food, water, air, spacesuits, boots, helmets, cameras film and equipment needed for up to 10-11 days in space. The usual reply is that these items were in the Lem or the service module, but that would be very unsafe (not to mention bringing back hundreds of pounds of moon rocks)
2.   Back in the Apollo days we (the public) were told that the Moon was an Extremely Hot, Dry, and geologically dead place with no atmosphere. Now according to the NASA Lunar Science Institute the moon is an extremely Cold, Wet geologically active place with an atmosphere that extends all the way to earth. Just the opposite of what we were told.
3.   The trajectory of the Apollo missions is nothing like spacecraft go to the moon today. Today spacecraft going to the moon make several increasingly large earth orbits not a crazy “8” trajectory.
4.   Regardless of popular belief computer and communication technology were not sufficient in the sixties (slide rules were  the norm in the sixties)
5.   Several of the Apollo mission especially AP17 supposedly went to the moon when the moon was nearly full. If the moon puts out enough light that I can easily see the settings on my telescope and camera in Florida, over 200 thousand miles away don't you think that the light would blind the astronauts if they were actually on the moon
6.   Several people note that the lighting wasn't right in the lunar pictures and that they did not bring any lights with them Why not? It would take at least 3 additional cameramen to take all the lunar footage not Ed Fendell from Houston with a remote control
7.   Since the spacesuits were supposedly cooled by water the astronaut's would have instantly frozen on Eva's and on the surface of the moon in the shade
8.   The  Lem was made of Tin foil, Mylar and tape the abort procedure was to bail out in space
9.   Any glass in the command module would melt upon reentry killing anyone inside
10.   There is no way the record of the Apollo missions is accurate.

[Post restored by LunarOrbit]

REst assured DAKDAK they didn't go, and so you are not crazy.  The record is not accurate.  The record doesn't even exist.  Not a good one anyway.

[Jason Thompson]

Aaaaand there it is. Wondered when you'd get round to being obvious.

[chrisbobson]

Actually, the most efficient Lunar Orbit Rendezvous pattern would be this "figure 8" which you speak of. Basically, the spacecraft is in what is called a "parking orbit" around Earth. It is basically sitting there to await what's called a Hohmann Transfer...

Actually, there are multiple meanings of "most efficient" here. Engineering is all about making tradeoffs. Everything depends on how you define "optimum".

Any lunar mission needs propellant to get there. Within limits you can get there faster by burning more propellant, or you can save propellant by taking a more leisurely trip. But a manned lunar mission has other constraints: it has to carry substantial amounts of food, LiOH, water, hydrogen and oxygen to keep the crew alive, and the longer the trip the more of these consumables you'll need. The increase can easily cut deep into your propellant mass savings from going more slowly.

Unmanned missions have considerably more flexibility because crew consumables (and boredom) aren't issues. So a Hohmann transfer isn't necessarily the cheapest possible way to get to the moon. If somebody could find a cheaper way that takes months instead of days, that would be a non-starter for a human flight but entirely practical for a robot.

Such a way has been found: the use of ion rockets.

Ion drives achieve extremely high Isps compared to chemical rockets, but they have an Achilles heel: very low thrust. You can't use them in conventional bang-bang (impulsive) maneuvers like a Hohmann transfer. You have to spiral your way out with lots of long (often continuous) burns that actually require more total delta-V than the Hohmann impulses, but the ion engine can easily provide that extra delta-V and more. But it'll still take you months to get there, and that just ain't acceptable for a human crew.

So "efficiency" is highly context-dependent.

It seems when it comes to a lunar mission it is all about safety though.  Who cares how you do it as long as you get there and back.