Why Nuclear Power?
Costs and Efficiency
Mission costs are extensive. The following graph shows how the cost of a mission goes up as the mass of the spacecraft increases:
- http://www.atmosp.physics.utoronto.ca/people/ben/pages/mission_costs_and_reliability.htm
Although not directly cheaper than the alternatives, applying nuclear power to space travel can cut costs in several areas. The re-use potential for nuclear rockets is high, and they would be more efficient than chemically-propelled rockets, which are mostly only used once (the solid rocket boosters on the space shuttle are often re-used, but chemical rockets burned after certain spacecraft make it into orbit are not re-used with much frequency).
The higher efficiency of nuclear rockets relies on creating a higher specific impulse. The specific impulse (ISP) is the change in momentum per unit mass for rocket fuels. It is basically how much more push accumulates from the fuel source. It is measured in seconds (meters/second in Europe). The ISP for most chemical rockets is in the 100-700 range. The current space shuttle's engine has an ISP of around 450 s. Nuclear rockets could generate much higher ISP's of at least 1000 s. The thrust of the most advanced nuclear rockets would be 20 times that of the space shuttle. The comparison is illustrated by this graph:
The graph may be difficult to understand, but its purpose is simple: it shows that nuclear rockets get more miles per gallon than chemical rockets. For a short-range mission, the chemical rockets would be sufficient. However, the nuclear rockets would be much more efficient for longer missions.
What about Solar Power?
Solar-powered satellites actually work quite well. They collect light from the Sun and send it back to Earth through a laser or microwave beam. Additionally, current NASA spacecraft use the gravity of the Sun or a planet to gain speed, and then rely on solar power for electrical purposes. However, this obviously wouldn't work for deep space missions. The Sun's light would be too dim to even power the electrical instruments. A trip to Pluto, for example, will not be made with the exclusive help of the Sun.
NASA is also working on new fuel-cell technology. You can read more about it at this link:
- http://www.spacedaily.com/news/energy-tech-02i.html
Safety
Safety is always an issue when nuclear power is involved. However, the nuclear rockets would be very safe. The nuclear reactors would only be turned on when the spacecraft is 250 miles into Earth's orbit. The reactors themselves would not be dangerous at all during the actual launch.
Health
Nuclear power for space travel also has advantages for the astronauts themselves. The missions would be shorter. A crew could get to Mars in a few months, and shorter missions mean less psychological problems for the astronauts.
Additionally, the nuclear reactors could be used to create artificial gravity. This decreases the possibility of muscle atrophy, bone loss, and other harmful effects of microgravity.
- http://www.pma.caltech.edu/~chirata/deltav.html
- http://www.thewinnipegsun.com