Apollo 11 Question

[PetahSchwetah]

[deleted]

Edited January 14 by PetahSchwetah

[Richy teh space man]

N-body physics and the fact that the moons gravity isn't perfectly uniform caused its orbit to decay.

[Canopus]

No. In the real world there are all kinds of gravitational influences not only from the moon but also from earth and the sun all working there forces on objects in orbit. All orbits are unstable unlike in KSP where only one body's gravity influences your vehicle.

[PetahSchwetah]

[deleted]

Edited January 14 by PetahSchwetah

[Richy teh space man]

The atmosphere around Earth, unlike Kerbin, doesn't have a fixed end to it. Hence the ISS loses speed gradually due to drag (albeit slowly).

[Drunkrobot]

In the case of the ISS, the upper atmosphere has more to do with it. At the stations altitude (415km above sea level), there is still some air particles causing drag on the station. Not enough to be a day-to-day worry, of course, but enough that a boost is needed every once in a while.

[Saaur]

Also I'm willing to bet they could remotely trigger a little RCS nudge when they undocked to reduce the LEM's orbital velocity, bringing it even closer to the surface where gravitational differences would decay the orbit even faster.

[cypher_00]

From NASA's website about the Apollo 11 mission:

"The LM lifted off from the Moon at 17:54:01 UT on 21 July after 21 hours, 36 minutes on the lunar surface. After docking with the CSM, piloted by Michael Collins, at 21:34:00 UT, the LM was jettisoned into lunar orbit at 00:01:01 UT on 22 July. The fate of the LM is not known, but it is assumed that it crashed into the lunar surface sometime within the following 1 to 4 months."

[Moar Boosters]

http://history.nasa.gov/SP-4029/Apollo_18-29_LM_Lunar_Impact.htm

I found this.

It looks like Apollo 12, 13 and 14 were crashed into the moon using thrust because they crashed after only a few hours and the measurements were recorded by equipment left on the surface by apollo 12. No data from apollo 11 and 16 seems to suggest it was left to deorbit naturally which took about a year. (or 1-4 months depending which part of nasa's website is correct )

[MrPopcup]

As others said, there is more than one object influencing the LM module, of course it doesnt happen right away or after a week, it requires time, that way the LM WILL eventually crash into the moon, i also think they had some retro rockets or RCS thrusters to bring it down faster

[mellojoe]

The moons gravity is a weird thing. It is not uniform and has all sorts of odd fluctuations. The core of the moon is also a weird place. The Apollo 12 mission (I think) purposely crashed an empty lander into the moon, and it rang like a bell for something like 30 minutes or so. I'm doing this from memory, so please exuse any errors.

Any satellites placed around the moon would eventually decay simply because of the uneven gravity wells.

As for the ISS:

I think this image shows the slow decay and correction burns of the maximum height of the station.

Here is the chart for the MIR station:

[roosterr]

This is a very great question. Coincidentally I just finished my "Apollo Style" challenge and one of the tasks was to jettison the LM into the Mun on its departure from the CM. I had forgotten about that and left it out, but thinking back I would think they would have to rig something complex to do it, or would they even have enough fuel left?

All the explanations here make perfect sense, and I now see it would be more difficult to implement in KSP than real-life. Here is my mission and I at least ditched the TLI stage motor and tank into the Mun before Munar orbit, just like the real deal: http://imgur.com/a/Uuynv/embed#0

[Dweller_Benthos]

Interesting. I always figured they would eventually crash. Aren't there new lunar surveyors up now that are mapping the moon more closely? Thought I heard something about that, or is it still in the planning stage? I see they have the lat/lon for most of them, would be nice to see close up photos of the sites.

Edited September 26, 2013 by Dweller_Benthos

[lazarus1024]

LADEE satellite just headed toward the moon. As for any current orbiters, I don't believe there are any. Lunar surveyor was a few years back and it crashed/they crashed it end of mission. The recent gravity measurement mission (I forget the name of it) used twin satellites that they intentionally crashed in to a mountain at the end of the mission.

I think NASAs stance is, if we don't have a plan for it, better safe to crash the sucker than worry about any future orbital collisions.

Moons very uneven gravity and moon/earth influence on the orbit should generally cause most lower orbit stuff to decay within a matter of months to a year or two, but higher orbit stuff could be decades or longer.

[SkyRender]

Incidentally, if you want to imitate the Apollo standard of crashing the lander back into the surface, deorbiting doesn't take a lot of energy for most bodies. Generally speaking, you need around 1/10th to 1/20th of the total orbital velocity to deorbit something into the ground. That's around 32 to 64m/s at the Mun, not very much. Your Kerbals' RCS packs are powerful enough to let them return to the parent ship after a stunt like that, too.

[LameLefty]

LADEE satellite just headed toward the moon. As for any current orbiters, I don't believe there are any. .

LRO (Lunar Reconnaissance Orbiter) is still there and still in operation.

http://lro.gsfc.nasa.gov

[Dkmdlb]

Coincidentally I just finished my "Apollo Style" challenge and one of the tasks was to jettison the LM into the Mun on its departure from the CM. I had forgotten about that and left it out, but thinking back I would think they would have to rig something complex to do it, or would they even have enough fuel left?

After docking and crew transfer, keep the LM docked to the CM and burn retrograde just enough to lower the Pe to the surface. Undock the empty LM, turn the CM prograde, and burn to raise Pe again, leaving the LM behind to impact the surface. This maneuver won't take much fuel, especially if you are in a really low orbit.

[lincourtl]

There was a small deobit burn on the ascent stage after the pyrotechnics were fired severing the connection with the CM, and the CM performed a tiny separation burn just to move it away from the ascent stage.

Here are a couple of relevant sections from the Apollo 15 LSJ transcript:

179:27:13 Scott: Okay. We're proceeding through the pre-Jett checklist at this time, and we'll get right to you.

[Comm break.]

Public Affairs Officer - "This is Apollo Control. We're now about 2½ minutes away from the scheduled time for jettisoning the LM. At the time of jettison, the spacecraft will be in an attitude with the Service Module SPS engine pointed towards the Moon and the LM jettison will occur with the LM jettisoning away from the lunar surface. Following the jettison, the Command Module will perform a small retrograde separation maneuver to assure that there's no chance of recontacting the Lunar Module, and with separation coming at 179:30, the deorbit burn, the burn to impact the Lunar Module into the lunar surface, will occur at 181 hours, 4 minutes, 19 seconds; and we predict impact will be at 181 hours, 29 minutes, 23 seconds."

181:03:47 Parker: Apollo 15, Houston. Calling in the blind. Standing by. Over. [No answer.]

Public Affairs Officer - "We're coming up now on 20 seconds until the beginning of the LM deorbit burn. It will be a 201 foot per second [61.3 m/s] burn, using the four Reaction Control System thrusters on the LM ascent stage. LM Guidance and Control Officers both report telemetry data indicates the LM is burning. And we should have impact at 181 hours, 29 minutes, 23 seconds. We do have lock on with the Command Module, However, the signal strength is not strong enough at the present time for us to hear any response from the crew. Apparently they're not in the attitude with the High Gain Antenna yet to give us a good enough signal strength for voice communications."

Public Affairs Officer - "The Guidance Officer says that the burn is progressing normally with the LM ascent stage, and again those predicted impact coordinates are 26 degrees, 12 minutes north, 1 degree, 6 minutes east."

Public Affairs Officer - "The Guidance Officer says we've had shutdown now. And the LM guidance system appears to have shut the burn off right on time. Guidance says the residual was .08 [fps, 2.4 cm/s], which indicates that the burn was almost precisely as planned. And at the conclusion of that burn, the ascent stage has a weight of 5,315 pounds [2,411 kg]. Currently the altitude is 61.4 nautical miles [113.7 km] and we'll be able to watch that altitude as it drops off to nothing at impact."

[magnemoe]

The moons gravity is a weird thing. It is not uniform and has all sorts of odd fluctuations. The core of the moon is also a weird place. The Apollo 12 mission (I think) purposely crashed an empty lander into the moon, and it rang like a bell for something like 30 minutes or so. I'm doing this from memory, so please exuse any errors.

Any satellites placed around the moon would eventually decay simply because of the uneven gravity wells.

Yes saw read an link from the ksp forum about it, moon is poor of heavy materials and multiple huge asteroids with lots of metal has crashed into it. Effect is so large you could measure it with an

cord and a weight some places. The result is that low Moon orbit (not Mun) is unstable, high orbit is unstable beacuse of Earth.

They also hit the Moon with some 3rd stages, anyway the lander should have fuel left. so you could deorbit it either by remote or simply program the computer to do an burn at some later time.

[lazarus1024]

LRO (Lunar Reconnaissance Orbiter) is still there and still in operation.

http://lro.gsfc.nasa.gov

Well then, I sit corrected.

Thanks.

[roosterr]

After docking and crew transfer, keep the LM docked to the CM and burn retrograde just enough to lower the Pe to the surface. Undock the empty LM, turn the CM prograde, and burn to raise Pe again, leaving the LM behind to impact the surface. This maneuver won't take much fuel, especially if you are in a really low orbit.

Yep, I figured as much already, but fuel consumption is critical on the last leg of the mission. So the retro burn AND having to reburn prograde to get back into orbit, I am not sure I am willing to to that. At least not at the time anyway. Now that the mission is complete I would have no problem redoing it to see if I could pull that off. Probably, maybe

[Motokid600]

What documentary was it? Shadow of the Moon? I have a question too. Sorry if it strays a bit.

In that documentary after MECO ( or was it after TLI? Either way.. ) Were the windows of the CSM covered with fairings? because there was a scene that looked like they jettison and "They finally gave me a window to look out of."

How is this possible? Because if I remember it looked like the LM windows not the CSM. Lol Idk why that's been bugging me.

[Dunbaratu]

The moons gravity is a weird thing. It is not uniform and has all sorts of odd fluctuations. The core of the moon is also a weird place. The Apollo 12 mission (I think) purposely crashed an empty lander into the moon, and it rang like a bell for something like 30 minutes or so. I'm doing this from memory, so please exuse any errors.

There was an experiment they did on Apollo 13. It's the only part of Apollo 13's goals that was able to be carried out according to plan because all the work the spacecraft had to do for it had already occurred long before "Houston, we've got a problem" happened. With Apollo 12 having installed the corner reflectors and the ability to make seismology recordings from them, NASA realized that the best way to get an idea of what the inside of the moon might be like would be to give the reflectors a good "ping" to measure by just smashing something into the moon. And when they looked at how to get something with good mass to smash into the moon they realized the Apollo mission profiles tend to be set up just right to send the Saturn V's stage 3 at the moon if they're just altered slightly. So on Apollo 13 they did that. Instead of ditching stage 3 and then trying to aim to miss the moon slightly, they instead kept stage 3 attached, used it to aim themselves on a lunar impact path, detached stage 3 while they were heading for impact, and then had the command module push itself slightly to the side to miss the moon.

[Bunsen]

What documentary was it? Shadow of the Moon? I have a question too. Sorry if it strays a bit.

In that documentary after MECO ( or was it after TLI? Either way.. ) Were the windows of the CSM covered with fairings? because there was a scene that looked like they jettison and "They finally gave me a window to look out of."

How is this possible? Because if I remember it looked like the LM windows not the CSM. Lol Idk why that's been bugging me.

The Launch Escape System included a shroud that covered the entire CSM, for protection from the LES rocket blast and aerodynamic heating during ascent. The LES was jettisoned a little while after 2nd stage ignition, and it took the shroud with it.

[Mr Shifty]

There are several low altitude orbits of the moon that are relatively stable, mostly because they stay away from the "mascons" -- concentrations of mass that make the moon's gravitational field lumpy.

http://science.nasa.gov/science-news/science-at-nasa/2006/06nov_loworbit/

The Artemis P1 and P2 satellites are also now orbiting the moon, after orbiting L1 and L2 for a while.

http://www.nasa.gov/mission_pages/themis/news/artemis-orbit.html

And here are some fascinating images taken by the LRO of the SIV-B impact sites (mentioned by Steve Mading above) and robotic rover tracks, including Lunakhod I.

http://www.nasa.gov/content/lroc-coordinates-of-robotic-spacecraft-2013-update/

Edited September 27, 2013 by Mr Shifty