The Cassini probe will make use of four gravitational assists in its trip to Saturn. The major debate over the Cassini probe is an indirect result of the use of gravitational assists. Critics of the probe fear that while Cassini circles close to Earth in order to draw force from its gravity, it will become damaged due to a malfunction or due to a collision with some space debris. They worry that the 72 pounds of Plutonium dioxide that will supply electrical power to the probe will come dangerously close to Earth. Plutonium s radioactive nature leads these critics to ascertain that Cassini will pose serious biological threats to the inhabitants of Earth.
Critics also worry about the potential danger of a plutonium leak at the launch site .
If the Cassini mission were to experience some accident during its launch, similar to the Challenger accident of 1986, the risks would be obvious. Unlike the Challenger accident which posed little danger to the nearby residents of Florida, plutonium would be sprayed into the atmosphere further endangering the lives of nearby residents. NASA argues otherwise, claiming that the Cassini probe is virtually fail-safe. They say that the danger of an earth swingby accident or the danger from any plutonium leaks are both very low. There are some scientists who agree with NASA's conclusions .