The Gen1 Enterprise will have three nuclear reactors for creating all of the electricity needed for operation of the ship. They are:
- A 1.5GWe main reactor located in the main engine hull in front of the main engine
- A 500MWe auxiliary #1 reactor located in aux engine hull #1 in front of aux engine #1
- A 500MWe auxiliary #2 reactor located in aux engine hull #2 in front of aux engine #2
GWe stands for gigawatt electrical power; MWe stands for megawatt electrical power. And to convert between the two units, 1GWe = 1000MWe. Thus a 500MWe aux engine is .5GWe.
The reactor locations within the ship can be seen in the diagram above.
The total electrical power generation capacity for all three reactors combined is 2.5GWe. The three reactors are used mainly to power the three ion propulsion engines, but the electrical power generated is also routed to anywhere that it is needed in the ship. These three reactors provide triple redundancy to match the triple redundancy used with the engines.
A reason to keep the three reactors in three separate hulls – and separated from the saucer hull – is to protect the people who reside inside the saucer hull in the case of an emergency. For example, if a meteor strikes one of the reactors, the reactor can be jettisoned away. This is a case where the Enterprise ship basic configuration that has been lifted from science fiction fits nicely with the functional needs of the actual Gen1 ship design.
Another reason to have the three reactors in three hulls set away from the saucer hull is to reduce the exposure to any low level radiation from the reactors on the people and electronic equipment in the saucer hull. While the reactors will be heavily shielded to block the release of radiation, some gamma radiation and neutron radiation will still escape at a low level. So “distance attenuation” is a strategy used to further reduce this radiation. Distance attenuation takes advantage of the fact that radiation from the reactors falls off by the inverse-square law. While short term exposure will cause no ill effects on a person’s health, such as when workers or visitors are in the main engine hull or aux engines hulls, long term exposure might pose a health risk. Thus the reactors are located at least 250 feet away from the saucer hull at all points.
Key systems on board the Gen1 Enterprise that will need electrical power generated by the reactors are:
- The three ion propulsion engines
- Electronic equipment (communications, ship control hardware, computers, sensors)
- Oxygen generators
- Heating, cooling, and air conditioning
- Gravity wheel electromagnets
- Active radiation shield
- Water pumps
- Food preparation equipment including stoves
- Spaceport motorized doors
- 100MW laser
- Research labs
- Micro-manufacturing equipment
The three reactors will have the need to get rid of excess heat. The ships outer hulls are covered almost entirely in aluminum, and this aluminum is used to radiate this waste heat into space. In fact, this is one of the reasons to use aluminum as the material covering the outer hulls. Specialized and more efficient radiators will also be included locally on the main engine hull and the two aux engine hulls.
The heat from the reactors can also be used to provide direct heating where needed within the Enterprise. Pipes can carry heated water or other fluid throughout the ship for implementing a hydronic radiant heating system. Using radiate heating, rather than heating air and then recirculating this air around the ship, maximizes comfort for humans on board by eliminating cold spots and drafty areas inside the immense ship. Reactor heat can also be used to make hot water for washing clothes, washing dishes, use in sinks, use in showers, and so on.
In case of an emergency any one or all of the three reactors located with the three engines can be jettisoned away from the ship. For this reason at least two hydrogen fuel cells, that can generate 1MWe each, will be contained within the saucer hull for backup electrical power. These fuel cells can power the ship’s essential functions, although they are too small to power any of the three main ion propulsion engines. A 1MWe hydrogen fuel cell is now available on earth, made by Ballard Power Systems, as shown to the right. Of course a space version of this would be a new design, but the fact that such a thing exists on earth is a good indication that a fuel cell for the Enterprise on this scale is feasible.
One concern with hydrogen fuel cells is that hydrogen must be stored on board the Enterprise. This is not desirable for safety reasons. For example, the ion propulsion engines will not use hydrogen as their propellant due to the safety concern of having vast quantities of hydrogen stored in propellant tanks on the ship. (A gas leak, if ignited, will cause an explosion.) In the case of fuels cells, much less hydrogen must be stored. Also, NASA has a lot of experience with using hydrogen fuel cells in spacecrafts. But neither of these justifications is entirely satisfactory. A goal for the design team will be to look for a substitute for hydrogen fuel cells.
However, the risks from hydrogen gas may still be preferable to adding small nuclear reactors for backup power inside the saucer hull. A meteor strike on a reactor inside the saucer hull might spread radioactive contamination over sections of the saucer hull and create a great hazard for humans. Whatever the final answer, the design team should be very careful about using any explosive gas aboard the Enterprise.