ApolloHoax.net

Apollo Discussions => The Reality of Apollo => Topic started by: Allan F on March 18, 2013, 07:21:24 PM

Title: Video from the LRV - where to find?
Post by: Allan F on March 18, 2013, 07:21:24 PM
Hi, I'm currently in a debate elsewhere, where somebody claims the A17 video proves hoax. I need a piece of video, showing the astronauts parking, leaving the LRV, entering the LM. Does it exist?
Title: Re: Video from the LRV - where to find?
Post by: Allan F on March 18, 2013, 08:02:22 PM
I'm looking at the ALSJ, finding small clips, showing the LRV, Gene walking, Jack throwing his hammer. All nice stuff. Is there a place with longer clips?
Title: Re: Video from the LRV - where to find?
Post by: Echnaton on March 19, 2013, 03:27:50 PM
I know you are looking for web based video, but if you want to get the full downlinks, order the DVDs from spacecraft films.  DVD 6 of the Apollo 17 set includes this description

"Farewell - Final activities of the Apollo 17 crew on the lunar surface. Includes the unveiling of the commemorative plaque on the front landing gear of the LM and final statements from the lunar surface."
Title: Re: Video from the LRV - where to find?
Post by: ka9q on March 19, 2013, 05:36:17 PM
You probably won't find video of the astronauts parking because they usually had the LCRU (communications system) in voice-only mode on the medium gain antenna while driving.  After parking they had to manually re-point the high gain antenna at earth and switch the LCRU to video mode. That required turning a switch on the LCRU that could only be reached from the front of the LRV, not from the seats.

There is some video of Cernan driving the rover to the parking spot. He had left the LCRU in video mode and his driving was straight enough that the high gain antenna remained close enough to the  earth most of the time to produce a good picture. Youtube crank 'hunchbacked' cites this as evidence of a hoax, naturally...
Title: Re: Video from the LRV - where to find?
Post by: Trebor on March 20, 2013, 02:34:38 AM
There is some of the 16mm film taken from the rover during Apollo 15 here :

Title: Re: Video from the LRV - where to find?
Post by: Allan F on March 21, 2013, 12:16:52 AM
Thank you for that YT link. This user popped up - there's several 1 ½ hour long videos containing 16mm Apollo films. Haven't seen them all yet, but there's Lunar Orbit separation and descent, landing, EVA, takeoff, LOR, along with film from CM and LM. Maybe there's TV-footage as well.

eature=watch

Title: Re: Video from the LRV - where to find?
Post by: raven on March 21, 2013, 05:31:57 AM
The Internet Archive also carries quite a bit of 16mm DAC footage.
Title: Re: Video from the LRV - where to find?
Post by: Kiwi on March 21, 2013, 07:51:06 AM
Hi, I'm currently in a debate elsewhere, where somebody claims the A17 video proves hoax. I need a piece of video, showing the astronauts parking, leaving the LRV, entering the LM. Does it exist?

Can you give a few details of the claim?

It's over six years since I viewed the Spacecraft Films DVDs of all the Apollo 17 video and 16mm film, (I intend to buy them soon) and I don't recall any video of what you ask.  IIRC some of the video that Echnaton mentions includes the astronauts near the front of the LM, but their final statements were relayed on video from the final parking place of the LRV, which only shows the back view of the LM without astronauts.  We also get glimpses of parts of the rover.

After the LM ascends there are many minutes of vidoeo which are quite eerie when you think about them showing a "planet" without a single form of life on it.

They also hoped to video the abandoned LM crashing into South Massif, but missed it.

 
Title: Re: Video from the LRV - where to find?
Post by: ka9q on March 21, 2013, 08:12:08 AM
After the LM ascends there are many minutes of vidoeo which are quite eerie when you think about them showing a "planet" without a single form of life on it.
Well, we have a lot of photos from Mars that are also of a planet without a single life form on it.

Chris Kraft commented on that post-ascent LRV video as being like the letdown late on Christmas Day after all the guests have left.

Title: Re: Video from the LRV - where to find?
Post by: Allan F on March 21, 2013, 10:01:59 AM
Basically, this guy wants a video showing the astronauts parking the rover, walking back, climbing in, taking off.

I've told him, this is not possible, because there was a 17 hours interval between close-out of the last EVA, and lunar liftoff. Also, the LM had it's back to the rover, because it was landed with it's back to the sun, so the commander could pick a safe landing spot. He couldn't do that with the sun in his eyes, and the rover couldn't film anything usefull if the camera looked into the sun.

Edit: Also, I suspect the batteries on the LRV wasn't up to the job, videotaping 17 hours.
Title: Re: Video from the LRV - where to find?
Post by: Trebor on March 21, 2013, 12:37:18 PM
Basically, this guy wants a video showing the astronauts parking the rover, walking back, climbing in, taking off.

Why does he want this exactly?
Title: Re: Video from the LRV - where to find?
Post by: Allan F on March 21, 2013, 12:43:16 PM
Because if they didn't do it (t)his way, it was a hoax!
Title: Re: Video from the LRV - where to find?
Post by: Not Myself on March 21, 2013, 01:11:57 PM
Basically, this guy wants a video showing the astronauts parking the rover, walking back, climbing in, taking off.

Why does he want this exactly?

Probably because if both astronauts are in the video, then that proves there must have been a third person working the camera  ;D
Title: Re: Video from the LRV - where to find?
Post by: Donnie B. on March 21, 2013, 03:59:31 PM
After the LM ascends there are many minutes of vidoeo which are quite eerie when you think about them showing a "planet" without a single form of life on it.
Well, we have a lot of photos from Mars that are also of a planet without a single life form on it.

You don't know that!  :-\
Title: Re: Video from the LRV - where to find?
Post by: ka9q on March 21, 2013, 08:11:54 PM
I think it rather probable. Personally, I think NASA is greatly overselling the "life on Mars" bit, as though they're afraid the public won't understand any other reason to explore the solar system.

I think there are plenty of perfectly good reasons to land on and explore Mars (and every other planet and moon) even if they've never seen a single strand of RNA.
Title: Re: Video from the LRV - where to find?
Post by: raven on March 21, 2013, 08:18:22 PM
True, but I hope they do find life.
Title: Re: Video from the LRV - where to find?
Post by: Halcyon Dayz, FCD on March 21, 2013, 08:37:37 PM
Mars is the most Earth-like planet we have access to.
Studying it might give us some new insights on how our own planet works.
Title: Re: Video from the LRV - where to find?
Post by: Kiwi on March 22, 2013, 09:43:58 AM
Basically, this guy wants a video showing the astronauts parking the rover, walking back, climbing in, taking off.

In that case, he can't have it just as he can't have a video of Armstrong viewed from the lunar surface as he exits the hatch and climbs down the ladder, because it doesn't exist and never could have because of the way things were done back then.  There were plenty of activities that were only partially videoed or not videoed at all.

The one and only video camera on the moon was on the rover, so what is his proposed scenario?  That there should have been more than one camera?  Or the camera should have been removed and placed somewhere else, or Jack Schmitt should have neglected his close-out duties and operated the camera to satisfy some nutty requirement 40 years later?

Has he listened to all the audio and studied the transcripts and the lunar surface checklists and other documents and all the still photos that have been provided as evidence of the activities?

What logical fallacies has he committed here?  "If I ran the zoo..." must be one of them.  Is there a name for, "I can't understand it so it must have been faked"?

Feel free to use the quotes in my signature if they could be useful, but I doubt it.
Title: Re: Video from the LRV - where to find?
Post by: Noldi400 on March 22, 2013, 10:37:25 AM
Basically, this guy wants a video showing the astronauts parking the rover, walking back, climbing in, taking off.

I've told him, this is not possible, because there was a 17 hours interval between close-out of the last EVA, and lunar liftoff. Also, the LM had it's back to the rover, because it was landed with it's back to the sun, so the commander could pick a safe landing spot. He couldn't do that with the sun in his eyes, and the rover couldn't film anything usefull if the camera looked into the sun.

Edit: Also, I suspect the batteries on the LRV wasn't up to the job, videotaping 17 hours.

Well, more to the point, the TV camera being mounted on the LRV, it can't very well show it being parked and the astronauts dismounting.
Title: Re: Video from the LRV - where to find?
Post by: Halcyon Dayz, FCD on March 22, 2013, 10:50:40 AM
Is there a name for, "I can't understand it so it must have been faked"?
Looks a form of the argument from incredulity.
Title: Re: Video from the LRV - where to find?
Post by: ka9q on March 22, 2013, 05:56:28 PM
Mars is the most Earth-like planet we have access to.
Studying it might give us some new insights on how our own planet works.
Sure, but there's more to how our planet works than the life on it.
Title: Re: Video from the LRV - where to find?
Post by: Halcyon Dayz, FCD on March 22, 2013, 09:01:56 PM
Mars is the most Earth-like planet we have access to.
Studying it might give us some new insights on how our own planet works.
Sure, but there's more to how our planet works than the life on it.
Definitely.
I was thinking about climatology and geology and such.

I don't think there's life on Mars.
Once life establishes a foothold it will colonise every niche it can find, it's persistent and resourceful.
Once there's enough of it it changes the environment.
If there was life on Mars it would be all over the place, and it would be obvious.
Title: Re: Video from the LRV - where to find?
Post by: cjameshuff on March 22, 2013, 11:49:24 PM
I don't think there's life on Mars.
Once life establishes a foothold it will colonise every niche it can find, it's persistent and resourceful.
Once there's enough of it it changes the environment.
If there was life on Mars it would be all over the place, and it would be obvious.

There are places on Earth with no signs of life that would be obvious to the probes we've sent to Mars, apart from the high-oxygen atmosphere. And we may in fact have seen changes produced by microbial life. Purely geological processes can account for things like the "blueberries", but they quite often involve microbial activities as well. The surprisingly un-oxidized interior of the mudstone Curiosity drilled into might even be a sign that the mud contained biological materials that preserved it against oxidation. All we can be sure of is that it probably could have supported life, and was probably quite hospitable at one time (though perhaps not to us).
Title: Re: Video from the LRV - where to find?
Post by: Allan F on March 23, 2013, 12:59:16 AM
I've been reading a lot about the LRV lately. I wonder what changes would be made today, if one was to be constructed. Obviously a better (several?) TV-camera would be used, an active antenna system which could keep transmitting even on the go, navigation system, carbonfiber for the frame. What else?
Title: Re: Video from the LRV - where to find?
Post by: Allan F on March 23, 2013, 01:21:35 AM
Is there a name for, "I can't understand it so it must have been faked"?
Looks a form of the argument from incredulity.

At one time he was talking about Buzz Aldrin and his slide rule, used to compute the descent to the lunar surface. I asked him to provide some more info, like a link to a description how this was done. Didn't get it. Then he was on about his years as a factory worker, where he didn't know what he was producing. This he compared to the workers who manufactured parts for the various spacecrafts. It's been going on for a couple of weeks now. The dutch petrified piece of wood mistaken for a moon rock has been up, talked about, and forgotten.

Edit: A month and a day now, actually.
Title: Re: Video from the LRV - where to find?
Post by: ka9q on March 23, 2013, 03:38:37 AM
I've been reading a lot about the LRV lately. I wonder what changes would be made today, if one was to be constructed.
Being a communications engineer, naturally I would love the chance to design a new comm system for a lunar rover using today's technology.

The link to earth would operate on a higher frequency band and of course be entirely digital. This would provide considerably greater capacity. HDTV should be no problem.

The high gain antenna would track earth automatically while in motion. A phased array would be ideal so it wouldn't have to physically move; physically this would be a flat plate. A single antenna pointed straight up would suffice for landing sites near the center of the moon's disc, but sites closer to the limb might require the rover to carry several antennas, one pointed to each side of the rover and that might be too heavy. If a mechanically pointed high gain antenna had to be used, I'd include a medium gain backup to automatically maintain a lower speed link while the high gain antenna is acquiring.

Lunar surface communications should use an ad-hoc network, with nodes automatically discovering and relaying data between other nodes as well as sinking and sourcing their own data. WiFi hardware could be used almost off-the-shelf. One would go on the LM, one on each astronaut's PLSS, and one on the rover. Additional standalone relay units could be provided and deployed along the rover's path to provide communications beyond line of sight; depending on the terrain and the path to be covered, this might entirely eliminate the need for direct rover-to-earth communications.

The rover would be capable of full remote operation after the astronauts have left. This was proposed for the Apollo LRV but couldn't be accomplished before the end of the program.

Thermal control, especially of the batteries and electronics, was a serious headache in the Apollo LRV. It would be great to improve this, though I'm not sure how. It would be especially important if the rover is to continue its mission by remote control after the astronauts have left. The peak temperatures at solar noon and the long, cold lunar night are both difficult problems.

Title: Re: Video from the LRV - where to find?
Post by: cjameshuff on March 23, 2013, 10:25:45 AM
Thermal control, especially of the batteries and electronics, was a serious headache in the Apollo LRV. It would be great to improve this, though I'm not sure how. It would be especially important if the rover is to continue its mission by remote control after the astronauts have left. The peak temperatures at solar noon and the long, cold lunar night are both difficult problems.

You might just have the rover travel during twilight periods, and spend the rest of the time in deployable aluminized "hog shelters" that provide shade during the day and trap ground heat during the night, giving it a chance to do excavation, sample gathering and analysis, etc.
Title: Re: Video from the LRV - where to find?
Post by: Allan F on March 23, 2013, 10:55:19 AM
Solar panels for power - could be shaped to protect the electronics and batteries against direct sunlight? The frame and motors shouldn't be sunlight sensitive. Can't the motors be radiant cooled with cooling vanes in shadow?
Title: Re: Video from the LRV - where to find?
Post by: ka9q on March 23, 2013, 11:06:26 AM
At local noon, the problem isn't sunlight so much as thermal radiation from the lunar surface, which hits over 100C. I like cjameshuff's idea of taking a siesta under some reflective blankets, but it would still need some sort of radiator to avoid reaching equilibrium temperature with the surface.
Title: Re: Video from the LRV - where to find?
Post by: cjameshuff on March 23, 2013, 11:19:12 AM
At local noon, the problem isn't sunlight so much as thermal radiation from the lunar surface, which hits over 100C. I like cjameshuff's idea of taking a siesta under some reflective blankets, but it would still need some sort of radiator to avoid reaching equilibrium temperature with the surface.

The surface only reaches that temperature in the sun. Under the shelter, heating would be limited to what reflects into the shelter from outside and what conducts directly, which should be quite limited due to the low thermal conductivity of the surface. The shelter would maintain a relatively cool patch during the day, and a relatively warm patch during the night.
Title: Re: Video from the LRV - where to find?
Post by: Allan F on March 23, 2013, 11:28:26 AM
Wouldn't it just be a case of designing the floor pan of the rover so it could protect a patch of soil? If the electronics and battery were placed on the centerline, and the rover stopped shortly after sunrise, there would be shadow under it. And if reflective covers were on the electronics/batteries, it would have same effect as a shelter.
Title: Re: Video from the LRV - where to find?
Post by: cjameshuff on March 23, 2013, 01:25:19 PM
Wouldn't it just be a case of designing the floor pan of the rover so it could protect a patch of soil? If the electronics and battery were placed on the centerline, and the rover stopped shortly after sunrise, there would be shadow under it. And if reflective covers were on the electronics/batteries, it would have same effect as a shelter.

This might work for a large vehicle. The smaller the vehicle, the more light and heat is going to scatter in from the sides and conduct in from the edges and through the vehicle itself. I would be surprised if it worked for something people would call a rover.

Rather than a shelter, you might just carry a large sun-tracking solar array that keeps the rover and nearby ground in shade. Semi-permanent shelters just seem like decent places to stash equipment, samples, etc, and a simple half-cylinder "hog shelter" might be easy to supply multiples of in a light, compact package...little more than mylar and springy wire supports.
Title: Re: Video from the LRV - where to find?
Post by: Noldi400 on March 23, 2013, 02:15:09 PM
At local noon, the problem isn't sunlight so much as thermal radiation from the lunar surface, which hits over 100C. I like cjameshuff's idea of taking a siesta under some reflective blankets, but it would still need some sort of radiator to avoid reaching equilibrium temperature with the surface.

Don't forget that you're also going to need some means of dealing with dust; if the vehicle stirs up much dust at all, there's the camera lens(es), radiators, solar panels to think about. Not to mention anything that can't tolerate added insulation.
Title: Re: Video from the LRV - where to find?
Post by: Allan F on March 23, 2013, 03:12:24 PM
At local noon, the problem isn't sunlight so much as thermal radiation from the lunar surface, which hits over 100C. I like cjameshuff's idea of taking a siesta under some reflective blankets, but it would still need some sort of radiator to avoid reaching equilibrium temperature with the surface.

Don't forget that you're also going to need some means of dealing with dust; if the vehicle stirs up much dust at all, there's the camera lens(es), radiators, solar panels to think about. Not to mention anything that can't tolerate added insulation.


Cameras could be equipped with the same system that Formula One racecar cameras have - an extra pane of glass in front of the lens. When it gets dirty, it rotates past a brush, cleaning it. Probably limited lifespan if regular glass, but a piece of sapphire should be scratch-resistant enough to provide useful lifespan.

Amount of dust would be speed-dependent. Just go slow enough, and dust from the vehicle itself will be very limited. How about static charge? What's the charge on the dust? Could a solar array be made to carry a static charge which would repel dust?


Edit: With a couple of square meters of solar cells, there could be something like 2000 watts availabe. That should be enough to run cameras, mobility and datalinks and still have enough to put into batteries. At night, the batteries would freeze, which wouldn't be good for capacity. But if they're isolated, they could be heated by a small heating element. It wouldn't require much. Electronics - how temperature tolerant could they be made?
Title: Re: Video from the LRV - where to find?
Post by: Chew on March 23, 2013, 03:34:59 PM
Is solar power required for this hypothetical rover? Why not RTGs?
Title: Re: Video from the LRV - where to find?
Post by: cjameshuff on March 23, 2013, 03:38:48 PM
Don't forget that you're also going to need some means of dealing with dust; if the vehicle stirs up much dust at all, there's the camera lens(es), radiators, solar panels to think about. Not to mention anything that can't tolerate added insulation.

It is a significant problem. IIRC, the LRV had issues with the battery compartment overheating specifically due to dust buildup.

Legged robots might have some advantages, possibly kicking up less dust to begin with and having joints that can easily be sealed.
Title: Re: Video from the LRV - where to find?
Post by: Allan F on March 23, 2013, 03:45:39 PM
Is solar power required for this hypothetical rover? Why not RTGs?

Extended independent operation would be easier with solar power. Also, solar panels would be easier to lift from Earth than radioactive thermoelectrical generators. About one kilogram/square meter plus support structure. Voyager 1 has 3 plutonium-238 powered generators, and provide less than 500 watts of power with a weight of 120 kilograms. The rover would need additional chassis strength to carry enough RTG's to matter.

Unless you're talking about decades of independent operation. Then RTG's would be necessary, because of the degradation of the photovoltaic cells over time.

Edit: I don't know about the radiation from the RTG's and how it would affect electronics.
Title: Re: Video from the LRV - where to find?
Post by: Allan F on March 23, 2013, 04:17:18 PM
Also, thermal control could be achieved by using the terrain for cover. You know about House Rock, right? There's shaded areas which would remain cool the entire lunar morning. At lunar noon, shade is probably difficult to find. But it's only for a few days (earth). After noon, drive to the other side, where there's shade. And at lunar night, there's a nice corner with radiant heating on two sides.

That leaves morning and afternoon to explore, when the sun isn't at full strength.
Title: Re: Video from the LRV - where to find?
Post by: ka9q on March 23, 2013, 09:17:00 PM
Yes, that should work as long as the top surface of the blanket isn't exposed to much of the hot lunar terrain around it. Then it could use a high emissivity to radiate to the dark sky without also picking up much from the surface. (Sunlight can be rejected with low absorptivity.) I understand some of the ALSEP experiments at the Apollo 15 site had thermal problems because of longwave radiation from the surrounding mountains hitting their radiators.
Title: Re: Video from the LRV - where to find?
Post by: ka9q on March 23, 2013, 09:29:33 PM
Extended independent operation would be easier with solar power.
I think some form of nuclear power will be essential on the moon for the forseeable future, to keep warm at night if not to generate sufficient electricity to keep operating.

Just about every active American experiment placed on the surface of the moon or Mars had at least some Pu-238, to my knowledge. Even the EALSEP seismometer deployed by the Apollo 11 crew had some small radioisotope heaters to stay warm at night though electrical power came from solar arrays. So did the Mars rovers Spirit and Opportunity. The two Viking landers and Curiosity are fully nuclear powered, of course. I'm not sure about Pathfinder and Phoenix.

The lunar soil has extremely low heat conductivity, so in the future it should be possible to dig caves on the moon that will have a fairly uniform temperature all day long, and it would be possible to go there to stay warm at night and perhaps around noontime.
Title: Re: Video from the LRV - where to find?
Post by: ka9q on March 23, 2013, 09:40:41 PM
I don't know about the radiation from the RTG's and how it would affect electronics.
There's essentially no effect. That's why Pu-238 was chosen for RTGs. It's a pure alpha emitter, and nearly all of its decay products are also alpha emitters plus a few beta emitters; there are no hard gamma emitters that would be hard to shield. Radon is one of its daughters, so the material has to be enclosed if it's to be around humans, but that's about it.

RTGs are usually mounted on booms not so much to get the nuclear radiation away from the electronics and instruments, but to allow their waste heat to radiate to space.

Pu-238 also has a reasonable half-life, enough for a pretty long mission but not so long that its specific power (W/kg) would be unreasonably low.
Title: Re: Video from the LRV - where to find?
Post by: cjameshuff on March 23, 2013, 10:08:36 PM
The lunar soil has extremely low heat conductivity, so in the future it should be possible to dig caves on the moon that will have a fairly uniform temperature all day long, and it would be possible to go there to stay warm at night and perhaps around noontime.

This was essentially what was behind my hog shelter idea. Limit direct heating by sunlight and loss of heat at night, for a temperature range that stays closer to something a bit under the surface, except without having to actually dig a burrow.
Title: Re: Video from the LRV - where to find?
Post by: ka9q on March 23, 2013, 10:44:43 PM
You're probably right, though to be sure we'd have to do a full-blown analysis. You'd take all the surface properties and integrate the volume around them for the effects of dark sky, sun and lunar surface.

I guess I was thinking of underground shelters because they'd eventually be needed for a manned base to wait out solar particle events.
Title: Re: Video from the LRV - where to find?
Post by: Allan F on March 24, 2013, 01:58:04 AM
I hope I'm not considered off-topic with all this.

It is fascinating to speculate about the possibilities. I suppose the navigation and communication would be integrated into one system. Maybe a backup-system like the original LRV's gyroscopic pointer, but primary navigation using a digital computer and radio beacons like those used to guide aircraft to runways in bad weather.

How about lithium-based batteries? Would this be the best choice for a LRV?
Title: Re: Video from the LRV - where to find?
Post by: ka9q on March 24, 2013, 06:25:10 AM
The original navigation system on the LRV left a lot to be desired. Not that it could have been made much better at the time. The moon still lacks a magnetic field or a GPS.

The astronauts didn't really need it either, as they could just follow their own tracks back to the LM if they couldn't see it.

It's usually worth trying to piggyback navigation onto communications. High speed digital communications is often well suited to navigation, especially direct sequence spread-spectrum modulation. GPS and a lot of mobile phones have used it, though communications is now moving away from spread spectrum toward OFDM, which doesn't provide the highly accurate propagation delay measurements you need for navigation.

Optical ranging is another possibility between nodes within line of sight as the moon has no atmosphere to interfere.

Title: Re: Video from the LRV - where to find?
Post by: ka9q on March 24, 2013, 06:39:59 AM
Regarding batteries, a major design choice is between primary (non-rechargeable) and secondary (rechargeable).

Though primary batteries aren't rechargeable, they have the highest energy densities of all batteries and they tend to have longer shelf lives. One of the lithium metal chemistries would be the way to go today. They have better energy density than the Apollo workhorse, silver-zinc.

Silver-zinc's energy density is roughly comparable to lithium-ion, but while the latter has hundreds of charge cycles most Ag/Zn batteries, if they're rechargeable at all, have cycle lives in the single digits (e.g., those in the Apollo CM).

The workhorse rechargeable battery for aerospace in the past few decades has been nickel-hydrogen. They're similar to nickel metal hydride except that the hydrogen is stored as a gas instead of as a metal hydride, making them lighter but bulkier. I think they're now being displaced by li-ion, but li-ion has yet to prove itself in the lifetime category.

There are no obvious winners here just as there aren't any in terrestrial applications. Each has its plusses and minuses.

Fuel cells are another good option, assuming the water can be recycled and electrolyzed back into hydrogen and oxygen. The cycle energy efficiency isn't great, but the service lifetime could be very good.
Title: Re: Video from the LRV - where to find?
Post by: cjameshuff on March 24, 2013, 09:48:46 AM
OFDM is highly sensitive to doppler shift, which might make it a poor choice for general space communications. You can compensate easily enough if you know your relative motion, but...that brings you back to the localization problem.

Beacons limited to ground movement could be cheap micropower devices, so you could just use enough of them that there's always one or two in line of sight. Perhaps bury the sensitive electronics to reduce radiation and thermal issues, with only antenna and solar panel exposed.
Title: Re: Video from the LRV - where to find?
Post by: Allan F on March 24, 2013, 06:35:15 PM
I just checked with a friend who knows about fuelcells (PhD-student). I wondered if heat energy in stead of electricity could be used to break the water down. That would provide a heat sink, but that didn't fly. I think we should go with lithium-based batteries.

What about inertial navigation? That should be possible to build quite compact with the new chip-size accelerometers.
Title: Re: Video from the LRV - where to find?
Post by: cjameshuff on March 24, 2013, 07:14:55 PM
I just checked with a friend who knows about fuelcells (PhD-student). I wondered if heat energy in stead of electricity could be used to break the water down. That would provide a heat sink, but that didn't fly.

Thermal decomposition or high temperature electrolysis can certainly be used, but they don't provide a useful heat sink. They just make more efficient use of power sources than conversion to electrical power followed by plain electrolysis.


I think we should go with lithium-based batteries.

Lithium batteries are heat sensitive, short lived, prone to thermal runaway, and require lithium, which isn't readily available on the moon. Nickel hydrogen's got a good record. Nickel-iron is another good chemistry for robust industrial uses...heavy, but that's less of an issue on the moon, and they could eventually be made with easily accessible materials. They essentially don't wear out over multiple charge cycles, are reasonably efficient, and can last decades.


What about inertial navigation? That should be possible to build quite compact with the new chip-size accelerometers.

Even with very high quality accelerometers and gyros, it's only useful for short term position estimates, and tiny MEMS devices are far from the best available. A vehicle rolling, slipping, and bouncing across an irregular surface is about the worst possible use case for inertial navigation. It's useful for controlling the vehicle, but needs an external reference of some kind to compensate for drift, noise, limited frequency response, etc...
Title: Re: Video from the LRV - where to find?
Post by: ka9q on March 25, 2013, 04:23:58 AM
OFDM is highly sensitive to doppler shift, which might make it a poor choice for general space communications. You can compensate easily enough if you know your relative motion, but...that brings you back to the localization problem.
Exactly right, which is why I proposed it only for terrestrial (lunarial?) communications. Communications with earth would use a traditional satellite modulation scheme like QPSK or MSK on a higher frequency band, Ku or above.

OFDM is highly tolerant of multipath with a reasonably small delay spread like you find in terrestrial communications, and that's why it has all but taken over mobile phones and WiFi, plus TV broadcasting outside North America. But that also makes it difficult to piggyback navigation on it. So maybe an independent ranging system using direct sequence spread spectrum would be necessary for navigation. I.e., something like a ground-based GPS or your beacon idea, with transmitters placed in surveyed locations around the site. You'd need at least three in view to get 2D positioning, or 4 to get 3D positioning. If the beacons are placed on mountainsides so they can see each other, direct optical links could be used for time transfer and baseline determination to avoid the need for highly stable clocks.

DSSS can certainly be used for communications too (my company made its name doing that) but it tends to chew up bandwidth when you need a very high data rate, e.g. for HDTV.

Title: Re: Video from the LRV - where to find?
Post by: ka9q on March 25, 2013, 04:37:37 AM
Thermal decomposition or high temperature electrolysis can certainly be used, but they don't provide a useful heat sink. They just make more efficient use of power sources than conversion to electrical power followed by plain electrolysis.
There are several chemical cycles to produce hydrogen (and oxygen) from water with high grade heat: sulfur-iodine; zinc-zinc oxide; iron oxide; hybrid sulfur; copper-chlorine; and cerium (III/IV) oxide were the ones I could find easily on Wikipedia. Several include an electrolysis step that uses less electricity than straight room-temperature electrolysis.

These cycles might be a good use for concentrated sunlight, something that could be produced in great abundance on the moon, and provide a more practical way to store up electrical power for the long 2-week night than conventional batteries.

Electrolysis of exhaled water vapor and urine to produce breathing oxygen is already being done on the ISS, but they throw the H2 away. That would be exactly the wrong thing to do on the moon, which is poor in volatiles like H2 but rich in O2.

Like any heat engine these thermal converters would require heat sinks, which would have to be radiation to deep space. How big they would have to be depends strongly on how cold a temperature they have to produce.
Title: Re: Video from the LRV - where to find?
Post by: ka9q on March 25, 2013, 04:45:18 AM
Lithium batteries are heat sensitive, short lived, prone to thermal runaway, and require lithium, which isn't readily available on the moon.
I didn't say they were perfect, but if you're going to send them from earth they have the enormous advantage of one of the highest energy densities available.

There are a few other battery chemistries that look promising for bulk stationary storage, particularly sodium-sulfur if the corrosion problems can ever be worked out. (The problem isn't the sodium, it's the sodium sulfide compounds.) On earth they have the big attraction of using extremely cheap and plentiful materials, but I doubt they're as common on the moon.

I still think that in the near term the most practical power source for a lunar base will be nuclear, by far. Various solar thermal and chemical cycles look like they could be made to work, but seriously -- once you've got a working reactor, do you really need anything else? That leaves the portable power problem for rovers and PLSSes, though.
Title: Re: Video from the LRV - where to find?
Post by: raven on March 25, 2013, 09:00:29 AM
Solar-thermal has easier self expansion possibilities, that's one advantage in my opinion.
Title: Re: Video from the LRV - where to find?
Post by: cjameshuff on March 25, 2013, 09:00:56 AM
OFDM is highly tolerant of multipath with a reasonably small delay spread like you find in terrestrial communications, and that's why it has all but taken over mobile phones and WiFi, plus TV broadcasting outside North America.

A single communications and localization standard for spacecraft and ground vehicles seems desirable, but the multipath resistance is a good point.


You'd need at least three in view to get 2D positioning, or 4 to get 3D positioning. If the beacons are placed on mountainsides so they can see each other, direct optical links could be used for time transfer and baseline determination to avoid the need for highly stable clocks.

That's if you're doing full GPS-style localization. For path marking, single beacons with some amount of overlap could suffice. If you have directional antennas or prior rough location information to break the symmetry, you can also get full 2D localization with just two beacons, 3D with three (or two and a good elevation map). The same beacons could be used in higher numbers in locations where greater precision is required, but reducing the number of beacons you need to plant across the landscape seems worthwhile.

Another possibility is visual localization. There's no weather, no seasons, no plant life...the moon is ideal for a system that just recognizes the surroundings and infers its location from landmarks. This would be difficult to do on a portable device, but the needed cameras might be built into suits and vehicles, and would be useful when surveying large areas.