For years NASA insisted it couldn’t be done. Beyond the orbit of Mars, NASA said, solar energy could not be used to generate electricity for onboard power on space devices.

So the agency used the extremely dangerous nuclear substance plutonium — and people on Earth were put at great risk in the event of an accident.

For instance, in 1997 NASA launched its Cassini plutonium-fueled space probe, and in 1999 it had Cassini hurtle back at Earth in a “slingshot maneuver” to increase its velocity so it could get to Saturn. If there was an “inadvertent reentry” of Cassini into the Earth’s atmosphere during this maneuver, it would disintegrate and “5 billion … of the world population … could receive 99 percent or more of the radiation exposure,” NASA admitted in its Final Environmental Impact Statement for the Cassini Mission.

The potential death toll from a Cassini accident was put by Ernest Sternglass, professor emeritus of radiological physics at the University of Pittsburgh School of Medicine, at 20-40 million.

This is not a sky-is-falling story. Of 28 U.S. space missions using plutonium, there have been three accidents, the worst in 1964 in which a plutonium-powered satellite fell back to Earth, breaking up and spreading the toxic radioactive substance widely.

That caused NASA to develop solar power for satellites — and today all satellites (and the International Space Station) are energized by solar panels. But, insisted NASA, in deep space sunlight is too weak, and solar energy could not work, only plutonium would.

Now the leading space industry trade magazine, Aviation Week & Space Technology, reveals that solar energy is to be used by NASA to substitute for nuclear power in deep space: “Budget and technical realities have led NASA to put its once-ambitious space nuclear power plans on a slow track, but development in solar power generation should allow new scientific probes beyond Mars to operate without nuclear energy. The U.S. space agency is already planning a solar-powered mission to study the atmosphere of Jupiter, and has looked at sending probes as deep into space as Neptune using only the Sun’s energy for spacecraft and instrument power … It is all but certain the next U.S. deep-space missions will be solar-powered.”

The piece described the new giant solar energy systems that will be used to harvest solar energy at record efficiencies vast distances from the Sun.

Bruce Gagnon, coordinator of the Global Network Against Weapons & Nuclear Power in Space, comments, “For years NASA said that we didn’t know what we were talking about. Now NASA is planning to do what we’ve been saying all along they could do. It just goes to show that if you are willing to stay on top of an issue for a long time, something good can come from your hard work.”

Jeremy Maxand, executive director of the Snake River Alliance, an Idaho group that’s been challenging the use of Idaho National Laboratory to produce plutonium for space power systems, says, “We’ve said since day one that plutonium is unnecessary and dangerous, and that we can do the same job a better way, and now we’re seeing what that better way is — solar.”

What’s to happen in space is what should also happen on Earth. The Bush administration and nuclear industry are pushing for a “revival” of nuclear power.

We don’t need to take the enormous risk of building new nuclear plants — or having nuclear poisons over our heads. Safe energy technologies are here.

Karl Grossman, professor of journalism at the State University of New York/College at Old Westbury, is the author of “The Wrong Stuff” and narrator of the documentary “Nukes In Space” (