Talk:The Lunar Transverse Maps
The new lunar data looks like a once-in-a-lifetime oppertunity to get large number of students directly involved in lunar exploration.
--Jriley 13:15, 29 March 2008 (UTC)
Thermo and other spacecraft
Spacecraft must get rid of internal heat to keep their electronics from overheating. This is done with a radiator that rejects the heat to deep space.
It is very easy to design a free flying spacecraft to point its solar panels at the sun and its radiator in the anti-sun direction. This works very well.
On the Moon you cannot do this. The surface of the Moon blocks more than 1/2 the view of the radiator and it is difficult to keep the effects of the sun completely off it. The result is like having your rover in a giant frying pan at the temperature of the local surface.
The Russian Lunapods did last about a month. They weighted about a ton, were the size of a Volkswagen Beetle, and had both solar and nuclear power. This is not a good comparison.
The Apollo rover is better. The radiator was at the back where a trunk lid would be. The astronauts arrived mid-morning when the weather was good and left three days later before it got too hot. They would have cooked to death a day or too later if they had stayed. Just as the rovers did.
The Apollo rover electronics had a tendency to over heat. The problem was mostly dust covering the radiator, but they also overheated if used near a sunlit mountain side.
The astronauts did leave some scientific instruments that ran for quite a while. Again this is a poor comparison. The instruments were simple and designed to be very heat resistant. They were also nuclear powered.
The electronics box will be covered with MLI (Multi-layered Insulation) except for the radiator. This is up to 12 layers of aluminized plastic with space between. It is great insulation but insulation will only do so much. If the radiator is not very effective the entire electronics box will simply reach the ambient temperature of the surrounding in a few tens of hours.
The two ideas suggested in my paper are 1) move away from the equator until the peak daytime temperature does not kill your electronics, or 2) bury in the regolith until the day/night temperature extremes are averaged out. Both approaches have serious problems.
I can provide a spreadsheet that I used to estimate the latitude of the northern and southern roads, but it does not have much text with it. I am not qualified to do a realistic thermodynamic study of the proposed rovers. It is not my field and I have not been able to get any volunteers to do it. This work would take about 100 hours and a fairly large desktop computer with the correct professional software.
Thanks for the discussion.
--Jriley 22:44, 31 March 2008 (UTC)
Student capabilities and Slope
Dear Lunarpedia people,
The Lunar Transverse Maps idea makes several assumptions that I feel are needed for a student rover to have any possibility of success, but that are not needed for a well funded project:
1. Lunar thermodynamics is a killer. It is much worst than Mars. Students do not have a good understanding of thermo in general and do not have the complex models needed to design reliable spacecraft.
2. The student rover electronics will only survive -10C to +40C. Outside that range it will die. The batteries and motors will die too. Student level projects like the X-Prize simply do not have the hundreds of millions of dollars to develop better than off-the-shelf devices and materials.
There are sweet spots on the Moon where the temperature is moderate and the students must go after them. Hence the two suggested approaches.
Slope is the second key. The surface is loose pulverized rock and the gravity is weak. It is very difficult to get the traction needed to go up a steep slope or even control the rover coming down one. The Apollo rover limit of 25 degrees (about 2.2 run to 1.0 raise) is going to be hard to beat. Even treaded vehicles do not work much better in the low gravity. Two area on the Moon that are not connected by a genital slope are simply not connected. The idea of circling the Moon at any latitude within this slope limit is a long shot at best.
The present slope data is simply not good enough to even understand the extend of this problem. I think the LRO altimeter will be the first data set up to this job. We need to get people to work on it right away.
Any ideas you have for promoting this idea are most appreciated. The only contacts I have at NASA and they are in a frugal mode at the moment. Ed Out is definitely in their mandate, it is just that it rarely gets independent funding and then only the most conservative idea. There is a lot of climate change going on of late, but I do not think that means that hell is going to freeze over any time soon.
Thanks again for your interest.
--Jriley 22:50, 31 March 2008 (UTC)