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Long-distance surface-trips by Transrapid instead of rovers

Posted by: Ekkehard Augustin - Sun Apr 03, 2005 3:34 pm
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Long-distance surface-trips by Transrapid instead of rovers 
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Post    Posted on: Fri Apr 08, 2005 7:41 am
It might be assisting to look at what is in discussion until now:

1. construction/building of beams, rails, roads
1a) construction of trains, rovers

2. speed of vehicles (rovers, trains, rockets)

3. capacity of vehicles (rovers, trains, rockets)

4. control of vehicles (human, robotical)

5. location of control (remote, non-remote)

6. purpose (building a radio telescope at the far side of the moon + required sender at the near side of the moon, building mines and fabriques for ISRU)

This I would have to put into a table with one column for the vehicle and one column at least for the radio telescope - my problem: I currently still don't know how to create a table here.

To me it seems that nothing can be done at the moon without vehicles - at least one vehicle will be required to do transportation from a space vehicle to a station and its site or location. For that purpose rovers will be sufficient I suppose. But the distance between a radio telescope at the far side of the moon and its sender at the near side will be hundreds of kilometers if not thousands - as far as I know the Apollo rovers had a speed like a normal bicycle. If that is right then these rovers would need 50 hours at least for 100 km and 500 hours at least for 1000 km. And they wouldn't carry much equipment.

There will be a mix of vehicles - rovers for short distances and others for long distances. I consider the long distances to be the challenge and to require much higher speeds as well as much higher capacity than the short distances. The table that I cannot manage to create will have to be complete by an additional table that would show that there will be compromises be required between investment costs at the one side and the capacity and speed requirements at the other side.

And there will be a mix of human with robotical as well as a mix of remote with non-remote control. This really seems to be very intersting for this thread.



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Post    Posted on: Fri Apr 08, 2005 12:17 pm
Astronomical instruments place on Farside will be very likely to rely on the far cheaper method of having a constellation of small relay satellites in lunar orbit, rather than some sort of "pony express" that physically carries the reports back to Nearside where they are radioed home.

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Post    Posted on: Fri Apr 08, 2005 1:02 pm
Agreed - that's nearly selfunderstanding to me.

I have one problem with the satellites - the proposal to build a radio telescope at the far side of the moon has been made to avoid the disturbing signals and emissions of the satellites orbiting Earth and all the other radio noise too. Satellites for receiving the data from the telescope may be a source of such noise and disturbances too. But okay that perhaps is not that problem and as far as I know there is a Lagrange point too where a satellite can receive data from the far side.

Another "problem" is that the data got by the telescope have to be sent to the satellite(s). If the sender doing that would be close or near to the telescope then this sender may be another source of noise and disturbations too - and this sender will send very often if not permanently.

For this reason it seems to me that has to be placed far away from the telescope - at a distance sufficient to make sure that the signals don't be in the reach of the telescope.

Third no communication from Earth to the far side is possible without a relay station. A relay communication satellite would have to send data to the far side - and could be a source of noise and disturbations again. To avoid that the relay station will have to be a station at the surface of the moon at the near side of the moon.

In this image there are three places at the moon to go to - by one rocket each? There should be a place to deliver equipment to and then the equipment should be carried by vehicle to the two other places.

The communication at the surface of the moon will be done by cable or by short-distance radio. The installation of the cable requires transportation and short-distance radio requires the installation of a lot relay antennas.

A relay satellite that sends the telescopes data to the Earth mustn't send to the moon never - it mustn't send to the telescope's location at least.

These reasons seem to require long diatnce transports etc.

But that telescope really is only one reason to think about transportation at the moon. ISRU is another. An the tendecy that there will be three lunar stations probably - american, chinese and japanese (perhaps) - is a third.



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Post    Posted on: Fri Apr 08, 2005 3:59 pm
Ekkehard Augustin wrote:
I have one problem with the satellites - the proposal to build a radio telescope at the far side of the moon has been made to avoid the disturbing signals and emissions of the satellites orbiting Earth and all the other radio noise too. Satellites for receiving the data from the telescope may be a source of such noise and disturbances too. But okay that perhaps is not that problem and as far as I know there is a Lagrange point too where a satellite can receive data from the far side.

Another "problem" is that the data got by the telescope have to be sent to the satellite(s). If the sender doing that would be close or near to the telescope then this sender may be another source of noise and disturbations too - and this sender will send very often if not permanently.

It is possible to use lasers to communicate, especially in vacuum. In this scenario there would be a number of satelites in orbit around the moon. They have radio but are programmed to stay silent for most of their orbit (over farside). They also have three or more laser communicators each for talking to ground targets and their orbital neighbors. Since the satelites' orbits and the location of the ground stations are known, calculating aiming points shouldn't be impossible. A low powered beacon may be needed to emit a tracking pulses on demand now and then, but nothing like the continual racket emitted by communications sats or cell phone towers. I don't know if you could use a communications laser to talk to a moving vehicle without it having to have a radio beacon.

If a circumlunar rover trail gets built from nearside to farside, and this mainly depends on whether a farside observatory is established directly from earth or from a nearside base, other methods are available. The most logical one would be to set up a chain of (laser) repeater towers alongside the track. This would have the additional bonus that you can add a radio receiver to the towers so you can teleoperate or telesupervise robotic land trains. That way you can keep their speed up without them behaving like lemmings and driving off a cliff. Near the farside observatory (within 100 km or so) robotic rovers would have to be autonomous or be shut down (they stop at a designated depot area) during designated observation periods when the towers' radio repeaters are shut down. Having a trencher bury a (fiberoptic) cable from nearside to farside shouldn't be impossible, except that the amount of cable needed would probably be far too heavy to even consider importing.

Ekkehard Augustin wrote:
For this reason it seems to me that has to be placed far away from the telescope - at a distance sufficient to make sure that the signals don't be in the reach of the telescope.

With laser communications this shouldn't be too big a problem. The communications array would be moved a kilometer away from the nearest optical telescope.

Cheers,
ErikM :twisted:


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Post    Posted on: Sat Apr 09, 2005 8:26 am
Laser communications is sounding convincing. What I know about lasers seems to mean that there are no radio enmissions at all. If that's right then the sender doesn't need to be far away from the radio telescope.

If there were towers be built along the track from the near side to the far side than again these towers will be places along a track of thousands or hundreds of kilometers. In this case again long distance transportation would be required - the initial thoughts and questions and the post trying to systemize the aspects and questions a little bit remain relevant then.

Long distance transportation may be required too if stations should be built based on ISRU - there may have to be several different mines for different ressources. And these mines may be far away from each other as well as from the place where the ressources are needed - the place of the lunar station, the location of the telescope or the location of the landing site of space vehicles.

Along the distances and tracks there may be hills and mountaines. Rovers would have to climb these hills and mountaines then - if there is no way to move around these obstacles. This could be much more difficult if the rovers carry equipment or mining products. At Earth there are tunnels going through the hills and mountains as well as bridges crossing valleys - at Moon no tunnels and no bridges are built yet. I could imagine that Transrapid/Maglev can climb up hills and mountains better that rovers.

Once the first beam is installed a train can move along it to the actual end. It can carry the next beam there and the beam can be installed. Once this is done the train can go further than before and continue to caary its own beams. The beams are installed above the ground at pylons. At Earth there allways is a significant distance between two pylons - at moon this distnace perhaps could be larger.

The beam dosn't need no asphalt layer like roads - and the trains wouldn't be faced to such problems like Opportunity has been faced to inside Endurance crater where the was the danger not being able to move no more because of deep soft soil.



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Post    Posted on: Mon Apr 11, 2005 12:08 pm
Thanks, erikm! I was just about to bring that up.

Basically, lasers used in communication work like the old Morse Code did with radio: the laser is turned on and off repeatedly and rapidly in a predetermined pattern. As there is practically no atmosphere to scatter the laser beam, once the beam is focused, it has a tendency to stay that way -- so there's essentially no "noise" created by the laser signal (the beam could be shot directly across the line of sight of the most powerful telescope in our current inventory, and the astronomers would probably not even be aware of it).

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Post    Posted on: Mon Apr 11, 2005 3:43 pm
Actually I think the radio noise from a relay satellite using RF communication would be no problem compared to the giant volume of noise on Earth, with TV, cell phones and radar. On Earth companies pay big $$ just to reserve a slot in the frequency spectrum. Compared to that, one or two relay satellites operating on one frequency chosen to be not interesting for astronomical observation and using directional antennas would be a very minor problem.


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Post    Posted on: Tue Apr 12, 2005 7:12 am
The german version of Scientific American - Spektrum der Wissenschaften - once in the last years published an article about SETI and their methods. The article included a graphic showing signals got by Arecibo and other telescopes.

That graphic showed one bright disturbation - it was the signal from Pioneer 10 which is by far weaker than the signals orbiting Earth.

So satellites orbiting the moon that use radio communication may be a severe disturbation no SETI-researcher as well as no present astronomer would like.



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Post    Posted on: Tue Apr 12, 2005 1:02 pm
Since the satellites would be used only for communication with the radio telescopes themselves, they could be commanded to remain silent when the telescopes were making any observation that could detect the satellite's transmissions.


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Post    Posted on: Tue Apr 12, 2005 1:08 pm
May be that the observation projects to be done by the telescope don't allow for that. Long-duration observations could gather an amount of data that exceeds the storage capacity. If so or not depends on the duration of the observation only - and there is no physical or technical upper limit for that duration.



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Post    Posted on: Tue Apr 12, 2005 1:29 pm
A relay satellite would listen to data from the telescope and relay it by directional antenna to another point without the telescope detecting that transmission. The only time the relay needs to send signals that could interfere with the telescope is when it is sending commands to the telescope itself. For example commands that tell the telescope to stop one observation and move to a different target for the next observation. Scientists would naturally wait until the current observation is complete before sending the command. If they need to send commands while a long observation is under way, they simply use a different frequency than that the observation. The relay would naturally be built to use only the least astronomically interesting frequencies to minimize any interference. Also, they control all transmissions from the relay and know when they are sending the commands. This is different than general radio noise that they don't control, such as TV and radar. And it would only be a probelm if the telescope was looking at the same part of the sky where the satellite is at the time. This would almost never happen by change and could be easily avoided.


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Post    Posted on: Tue Apr 12, 2005 1:41 pm
As far as I know the receiver is a source of outgoing radiation too - I am not sure of the reason why this is so. This problem doesn't exist in the case of laser communication according to my informations. The unpreventable radiations of the receiver would be a source of disturbations which researchers don't like.

The radiations of the receiver are a reason for governmental regulations - each receiver has to protect its environment against being disturbed. This works - but I suppose that the protection is too weak to prevent disturbations of observations made by a radio telescope.



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Post    Posted on: Tue Apr 12, 2005 1:58 pm
Even very badly designed receivers emit only a very small amount of noise. A well designed receiver on a satellite many kilometers away will not be detectable at all.


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Post    Posted on: Tue Apr 12, 2005 2:17 pm
The disturbing signal of Pioneer 10 had 1*10^-21 Watts - I seem to remember that the well designed receiver on a satellite far away sends an unpreventable noise of much more than that extremely weak signal.



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Post    Posted on: Tue Apr 12, 2005 2:26 pm
Pioneer sends about 5 watts. By the time it gets to Earth, it is down to the very low value you quoted. The pioneer signal was only detected because Pioneer used it's directional antenna to send maximum transmitted power to Earth and the telescope was looking right at Pioneer and tuned to the exact frequency Pioneer was sending. Our relay will have a low leakage receiver on a different frequency and the telescope will not look in it's direction anyway.


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