when we heal the earth, we heal ourselves. david orr

Alicia on The Mike Nowak Show

Chicago horticulture expert Mike Nowak invited me on his radio show to discuss Earth Hour. LISTEN HERE. I'm about 3/4 of the way into the recording.

Saturday, September 5, 2009

I Met an Astronaut

During my night out on the town, I happened to meet an astronaut. Our conversation eventually led to my eco-blogging hobby, at which point he assumed I'd disapprove of space venture on account of the resources expended to get one of those clunkers out of our atmosphere.

He was wrong. It's not that I'm against space exploration, it's that at some point, I'd like NASA to invest in some eco-engineering....maybe a solar-powered spacecraft? My new astronaut friend scoffed at the idea. After all, shuttles have to reach 200,000 mph to escape our atmosphere (Ug=m1m2/r). How can you achieve that speed with solar power? But before you abandon the idea of eco-technology entering space, check out THIS ARTICLE in which Louis Friedman, a former aerospace engineer at the Jet Propulsion Laboratory (JPL) in California, explains that the idea for a solar-powered space craft has been tossed around since the 1970's.

Regarding the power of solar photons, Friedman says, "Only in the vacuum of space can we harness that energy into a force, because there are no other competing molecules, like wind and atmosphere, and we're flying in an otherwise weightless condition. So we harness the energy of sunlight in the form of the photons that come out of the sun. They hit a giant reflective mirror, which is how we make our solar sail -- into a very thin, aluminized, highly reflective sheet of plastic. And as the photons bounce off the mirror, they transfer their momentum to the mirror, and that gives you a force."

According to the article, "Scientists see solar sailing as a feasible, efficient method that may someday be used to explore new worlds in our solar system, and beyond."

In fact, the Russians already have a head start. They concepted the first solar-sail spacecraft four years ago called Cosmos 1. Unfortunately, it didn't make it in to orbit, but THE PLANETARY SOCIETY is looking into launching another one soon.

What say you, Mr. Astronaut?

P.S. Is it just a coincidence that at this very moment, Google's top trending topic is "unexplained phenomena"?

09-05-09 11AM

As an addendum, a twitter buddy informed me that solar power has been used on the International Space Station for quite some time. In fact, I found out astronauts were sent to replace solar panels earlier this year and they were first installed back in 2000.

What we really need to know is: Can clean energy be harnessed to actually propel space craft from Earth?

1 comment:

Anonymous said...

As in, from the earth's surface into orbit?

The energy needed is very large. But, solar energy could be compressed over time to create enough power to lift a significant mass to an orbital altitude and speed.

That is what hydrocarbon fuels are. Solar energy collected by plant matter, then compressed and cooked for millions of years.

Unfortunately, rockets don't use hydrocarbon fuels. They use more exotic chemicals.

Solar sailing would be useful for long-distance propulsion only after the spacecraft is outside of Earth orbit. When the spacecraft is in orbit, it could be used to nudge the orbit a little, without expending any valuable cargo mass. However, the forces from the photons and the solar wind of particles are extremely tiny, even at the scales described in Friedman's article. I expect with those dimensions they are hoping merely to have a demonstration measurable force, not a practical one.

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