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Colt
2003-Feb-24, 07:23 AM
I have wondered about this since I saw the movie Apollo 13 and a thread in the LC forum reminded me of it. I have always thought that solar cells were used on some of the first satellites to provide power for their systems. Why couldn't they have wrapped the LCM and LEM in small solar cells? This would have solved or helped solve the power problem with Apollo 13 and would have allowed the astronauts to stay on the Moon for longer (just guessing here). Any comments on this? If solar cells were invented before Apollo went to the moon why didn't they put them on? -Colt

kucharek
2003-Feb-24, 07:47 AM
It was simply the solution of an optimization problem. The longer a flight is, the more solar cells would be good to use. But for the short Apollo flights, fuel cells and batteries best fitted the weight constraints. For the CSM, fuel cells also have the advantage of producing potable water - otherwise dehydrating the food woudn't have been that smart if you would have had to carry all the water for rehydrating with you as water from the beginning. The first LM designs also made use of fuel cells, but later it was switched to batteries ( http://www.astronautix.com/details/all16943.htm http://www.hq.nasa.gov/office/pao/History/SP-4205/ch6-6.html ) due to problems with fuel cell development.
Solar cells don't produce very much power per weight unit, but can produce much energy per weight unit if you leave them enough time.

Chariots for Apollo: A History of Manned Lunar Spacecraft (http://www.hq.nasa.gov/office/pao/History/SP-4205/contents.html) is a pretty nice account of the LM development.

Harald

<font size=-1>[ This Message was edited by: kucharek on 2003-02-24 02:48 ]</font>

Eric McLoughlin
2003-Feb-24, 08:20 AM
It's interesting that the Soviets tried both batteries and solar panels on their Soyuz spacecraft.

<font size=-1>[ This Message was edited by: Eric McLoughlin on 2003-02-24 03:21 ]</font>

kucharek
2003-Feb-24, 08:55 AM
I don't know the rationale for this, but I guess it was because Soyuz was planned for long-term missions and the russians couldn't get fuel cells to work.

Harald

Colt
2003-Feb-25, 06:45 AM
How do fuel cells work in creating water exactly? Is this a certain type of fuel cell? -Colt

Lexx_Luthor
2003-Feb-25, 07:24 AM
I recall a nuclear source on board the LEM. I remember it because they were worried about the Apollo13 LEM coming back to Earth.

Was this a radioactive decay source or a real controlled fission reactor thing (pretty small).

kucharek
2003-Feb-25, 08:45 AM
Radioactive decay source, an RTG, using thermoelements to turn heat into electricit. Was used to power the ALSEP, the scientif experiment package deployed on the Moon.

Harald

Lexx_Luthor
2003-Feb-25, 08:47 AM
Yes! I remember now. Thanks for the kick.

Eric McLoughlin
2003-Feb-25, 12:32 PM
The Russians never devloped fuel cell technology so relied on batteries for short duration missions and solar panels for longer term missions. Soyuz was capable of flying in either configuration, depending on the length of the flight.

traztx
2003-Feb-25, 04:53 PM
On 2003-02-25 01:45, Colt wrote:
How do fuel cells work in creating water exactly? Is this a certain type of fuel cell?


This explaines it pretty well:
(from How Stuff Works) (http://science.howstuffworks.com/fuel-cell2.htm)