Henry W. Brandhorst Jr.

It is abundantly clear that energy is the key to utilization of space. In fact, bold programs are completely dependent upon and in effect hostage to the availability of energy. We believe that, for either the baseline scenario or the alternative scenario that makes use of lunar resources, there is sufficient time to develop the broad mix of power sources and associated technologies necessary for success.

A list of envisioned applicable technologies related to power and energy supply for space activities at various power demand levels is shown in table 6 [Applicable Power Technologies table].

In general, stepwise development of a variety of sources is envisioned; First, an expanding LEO space station with power levels up to 10 MW powered by solar or nuclear sources. Then, lightweight photovoltaic systems for GEO and lunar surface operation. It is likely that lunar camps staffed only during the day could derive all their power (25-100 kW) from solar arrays. Lightweight electrochemical storage systems such as hydrogen regenerative fuel cells would find use at GEO and, in concert with solar arrays, would power surface-roving vehicles and machines.

When full-time staffing becomes appropriate, we believe that nuclear systems are the most likely source of power. Power levels in the 100-1000 kW range would be derived from lunar modified SP-100-class designs, while powers in the 1-10 MW range would be derivatives of civil and military multimegawatt nuclear developments. These man-rated, safe nuclear systems would simply be used as power demands warranted.

Thus, for a lunar base, photovoltaic (or solar dynamic) systems would be used initially for daytime operation, SP-100class systems would be used for full time staffing at power levels to 1 MW (by replication or design), and these would be followed by multimegawatt systems for the 1-10 MW needs. Similar progress is envisioned for either scenario for GEO operations and asteroid and Mars exploration. Attention must also be paid to the impact of the lunar, asteroidal, or Martian environment on parameters of the power system.

We consider it unlikely that use of nonterrestrial resources will affect power system development before 2010. It is rather the opposite: power systems will enable the development and use of nonterrestrial resources.

Significant advances in the areas of nuclear power d6velopment and beamed power transmission will be made by both the military and the civilian space program. Full advantage must be taken of such corollary developments.

It should be noted that development of the 1 - to 10-MW class of nuclear (or even solar) power systems will have a profound influence on the state and direction of the electric propulsion programs. These power levels enable electrically propelled orbital transfer vehicles and interplanetary explorers to travel to the outermost fringes of the solar system with larger payloads and shorter trip times than chemical systems. In view of these potentialities, a strong emphasis on developing such propulsion systems is warranted.

Assuming that current programs in photovoltaics and in the SP-100 nuclear plant continue, the following are considered critical technological issues for further research and development. They are presented in order of priority. By piggybacking atop and augmenting existing programs, we can ensure timely development of the requisite systems.

  1. SP-100-derivative nuclear power system capable of providing power to 1 MW in an environment safe for humans.
  2. Large-scale photovoltaic arrays; solar dynamic power conversion suitable for space, using collectors that concentrate sunlight.
  3. Solar furnaces and process heat applications suitable for processing space resources at high temperatures.
  4. Multimegawatt (1-10 MW) nuclear power generating systems for electricity and heat.
  5. Thermal rejection systems to reject waste heat from the power conversion system, processing, and environmental conditioning (New concepts for efficient radiation are required; the use of lunar subsurface rejection should be investigated.)
  6. High-voltage electric transmission and distribution of multimegawatt power.
  7. Thermal energy control and distribution for both manned and unmanned systems
  8. Lightweight, rechargeable thermal and electrical storage.
  9. Machine design including human factors; robotics to substitute for humans in hostile environments.
  10. Laser technology for solar and infrared sources to beam power in space
  11. Environmental interactions in space associated with energy sources, processing, and work in space; i.e., the impact of foreign materials and pollutants.
A broadly based program aimed at developing solar and nuclear power systems to the multimegawatt level is of the highest priority. For brevity's sake, we have discussed only a few of the variety of long-range, innovative energy-related programs supported by NASA, DOD, DOE, and industry. To ensure a broadly based, innovative program, a portion (up to 5%) of the funds allocated for space power research should be devoted to areas that may permit radical advance and extremely high payoff, albeit at high risk.


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