Why do people use rocket fuel instead of nuclear power for spacecraft?
In: Technology
Most rockets are a lot more powerful then nuclear reactors. To put it into perspective the ill fated Fukushima Daiichi unit 1 nuclear reactor is just twice as powerful as the combined fuel pumps in the Saturn V first stage. And that is just to pump the fuel and oxidizer into the actual engine where most of the power comes from. The designs for nuclear powered launchers have not used nuclear reactors for power but rather nuclear bombs, and in plural. This was one of the first projects to be scraped with the growing concerns of health issues due to nuclear testing. Something about a rocket leaving a trail of nuclear explosions across half the country did not sit too well with the public relations managers.
However if you start talking about nuclear reactors in the spaceships themselves and not the launchers and landers it is a very realistic idea. In fact both the US and the USSR have launched fully functional nuclear reactors into orbit in order to power the electronics on satellites. This was in the days when nuclear test projects had more support. Power efficient electronics means that current satellites and spacecrafts are able to utilize solar panels or if the mission includes operation in areas with little sunlight they have been using the decay heat from an isotope of plutonium to generate electricity.
But there is currently a new project with the goal of designing nuclear reactors for space missions again. And there is two reasons for this. Firstly the plutonium needed can only be generated in breeder reactors which is used to make isotopes for nuclear weapons. Most of these reactors have shut down due to the nuclear weapons agreements meaning that the plutonium is in limited supply. Secondly there have been a lot of advancements in electrical thrusters. Modern satellite designs will often use ion thrusters all around in order to increase the lifetime of the satellite before it runs out of fuel. The fuel is still used for propulsion but much less. Satellites with only station keeping duties are able to use its solar panels to power its thrusters but we might design missions to the outer planets where there is far less sunlight so we need the power of a nuclear reactor to power these thrusters.
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