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Dayton3

Member

Registered: 2002-06-03

Posts: 137

Re: An All Solar Mars Direct - Solar Power and Mars Direct

Should there be massive resistance to launching a nuclear reactor to power the chemical plants on the ERV for Mars Direct, how many solar arrays would be necessary to generate the same amount of power?

I'm a big supporter of nuclear power.  But would expect at least some opposition from environmental groups.  Any group that can oppose using RTGs aboard deep space probes would oppose anything.

The remote deployment of massive solar panel arrays on the surface would be difficult but not impossible.

I assume that the landing site preferred would be as flat and boulder free as possible.

Phobos

Member

Registered: 2002-01-02

Posts: 1,103

Re: An All Solar Mars Direct - Solar Power and Mars Direct

The Soviets designed a manned Mars mission using nothing but solar power.  I think they called the project Mars89 or something like that.  The solar panels for the ship were MASSIVE, I believe they stretched for almost a kilometer.  In the conceptual drawings the ship was just a dot between two very massive diamond shaped solar panels.  The Soviets seemed to have had played around a lot with the idea of sending people to Mars.  If we delved more closely into their projects we might learn a thing or two.  As for the specific numbers of arrays you'd need, I wish I had the numbers.
     And I agree that if your going to have any sizable colony that is capable of doing anything your going to probably need juice from a nuclear reactor.  Solar panels might be feasible for a small manned mission but they'd probably be impracticle for anything else.  Of course there's the possibility of using windmills to and maybe even geothermal vents or some combo thereof, but those things might be long shots.  It was thinking to that maybe you could have giant solar panels in geostationary orbit above the colony and have it beam down power.

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To achieve the impossible you must attempt the absurd

Tom Jolly

Banned

Registered: 2002-05-05

Posts: 40

Re: An All Solar Mars Direct - Solar Power and Mars Direct

Free space wattage is 1400Watts per square meter in Earth-orbit. The really nice solar photovoltaics they have can pull only about 20% efficiency, so you're looking at a collection of roughly 280 Watts per square meter as usuable electricity. Scale that up to whatever size you want.

Another option is to use an inflatable solar collector with reflective surfaces and heating a working fluid and running a turbine. The efficiency on this is much, much higher and ultimately weighs less overall, but involves using parts that break down. I think dependability is a factor, here. Don't have solid figures for this, though.

TJ

Tom Jolly

Banned

Registered: 2002-05-05

Posts: 40

Re: An All Solar Mars Direct - Solar Power and Mars Direct

Free space wattage is 1400Watts per square meter in Earth-orbit. The really nice solar photovoltaics they have can pull only about 20% efficiency, so you're looking at a collection of roughly 280 Watts per square meter as usuable electricity. Scale that up to whatever size you want.

Another option is to use an inflatable solar collector with reflective surfaces and heating a working fluid and running a turbine. The efficiency on this is much, much higher and ultimately weighs less overall, but involves using parts that break down. I think dependability is a factor, here. Don't have solid figures for this, though.

TJ

RobS

Banned

From: South Bend, IN

Registered: 2002-01-15

Posts: 1,701

Website

Re: An All Solar Mars Direct - Solar Power and Mars Direct

NASA is testing robotic construction and they've shown it's possible from Earth (though maybe not for Mars, where the time delays are much longer than on the moon). But assuming you can deploy one-meter-square panels on the surface using a rover and that each one makes 100 watts of power for 8 hours a day, and each panel weighs 4 kilograms, and you can wire them together remotely (which would be pretty tricky!), you'd need 1,000 such panels, weighing 4,000 kg, to generate 100 kw of electricity. That's the weight of the Mars Direct reactor, but it makes 100 kw of power 24 hours a day, not 8 hours a day. Also, 4 kg per panel may be too low; 8 kg may be more accurate. That might be enough power to refuel an Earth Return Vehicle over 18 months. That's all you need, because then the astronauts land and set up another 1,000 square meters of panels, and they makes sure all the wiring is done right. They then have almost as much power as a single reactor to draw off of. During a dust storm it would be reduced to maybe a quarter or a fifth as much for maybe as long as six months, so you'd have to design your human outpost to run on just a few kilowatts of power.

If I have the mass figures right, it might work. But no one yet knows how to deploy and assemble 1,000 square meters of solar panels by robotic rover dealing with a half-hour time delay. A reactor would definitely be simpler.

                  -- RobS

Shaun Barrett

Member

From: Cairns, Queensland, Australia

Registered: 2001-12-28

Posts: 2,843

Re: An All Solar Mars Direct - Solar Power and Mars Direct

There may be new hope for a big leap forward with photovoltaics.

    I found this interesting article about a new type of multi-junction cell based on layers of Indium Gallium Nitride with differing concentrations of Gallium.

    Apparently it has the potential (sorry !    ) to utilise photons from most of the visible spectrum, and a little beyond at each end. Thus possibly approaching theoretical limits for efficiency of 70%+ !!
    And it promises to be durable and not-too-expensive as well!

    The prospects for green energy production on Earth and for electricity generation in space could be vastly improved if this thing can be shown to work as advertised.

    Exciting stuff!!                 

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The word 'aerobics' came about when the gym instructors got together and said: If we're going to charge $10 an hour, we can't call it Jumping Up and Down.   - Rita Rudner

Phobos

Member

Registered: 2002-01-02

Posts: 1,103

Re: An All Solar Mars Direct - Solar Power and Mars Direct

I read about this discovery earlier but I didn't realize that it could have efficiencies up there in the 70% range.  That would definately revolutionize solar energy.   If this discovery pans out there's no need to have 80,000 square meter solar arrays to generate the power for ion engines as the Soviets had originally envisioned.  I wonder if we could reduce the mass of a solar powered spacecraft by using free-electron lasers to concentrate power on them from Earth/orbit in the same fashion that they are proposed for the space elevator.  The energy requirements for such a laser might make it unpracticle though not to mention keeping it perfectly aimed all the time.  Oh well, with 70% efficient solar cells lasers won't be needed anyway.

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To achieve the impossible you must attempt the absurd

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 28,832

Re: An All Solar Mars Direct - Solar Power and Mars Direct

A topic which is going solar and before my registering to become a member...