I enjoyed reading the commentaries by Alan Ladwig and Clifford R. McMurray [Space News, Jan. 16, page 19] and Ronald D. Dittemore [Jan. 30, page 17] on space exploration. Mr. Ladwig says we need to sustain the Vision for Space Exploration apparently by continually promoting space exploration, while Mr. McMurray makes a point about stretching to the Moon before the technology was ready. Mr. Dittemore is enthusiastic, but I think he may be premature in advocating commercialization of space. Clearly, there is an outspoken group of advocates for space exploration, which may be why the Bush administration gave NASA Administrator Mike Griffin and the agency a mandate to return to the Moon and journey to Mars. However, I think we are again stretching before the technology is ready — the current schedule does not allow for development of advanced-performance rocket engines.

At the California Space Authority “Transforming Space” Conference Dec. 1-2, 2005, I had an opportunity to talk with Mr. Griffin. He stated NASA is not going to develop advanced-performance rocket engines for use in returning to the Moon and going to Mars.

Instead, we are going to use 35-year-old technology in our future space endeavors. Extant rocket engines, hydrogen- or kerosene-fueled, operate at inefficient mixture ratios. Besides being inefficient, they are environmentally damaging because unburned fuel contaminates the atmosphere.

For example, the space shuttle main engines, operating at a mixture ratio of six to one, carry 25 percent excess hydrogen. The purpose of burning hydrogen is to release energy. The space shuttle could off-load 59,000 pounds of hydrogen and still release the same amount of energy they do now — at a mixture ratio of six to one, they only get energy from the 75 percent of fuel that is burned. The unused hydrogen dumped into the atmosphere combines with the oxygen and nitrogen in the atmosphere to produce nitric acid, which falls to Earth as acid rain.

Advanced-performance liquid-propellant rocket engines, operating at a more efficient mixture ratio of eight to one, would allow a vehicle such as the space shuttle to carry 29,000 pounds additional payload. This would be a great improvement in the cost of space operations and be of benefit to the environment, because all the hydrogen would be combined with oxygen forming only steam, which when cooled becomes pure water. It seems to me that NASA should be developing more efficient rocket propulsion before we embark on returning to the Moon and going to Mars.

This development could be enabled by adding five years to the schedule that has been given Mr. Griffin. This would allow NASA time to develop the advanced-performance rocket engines for use in returning to the Moon and venturing to Mars. Our space enterprises would benefit from increased payloads at lower cost, and from being environmentally benign. The space shuttle is the perfect vehicle to demonstrate an advanced-performance rocket engine.

In addition , the international space station can be utilized to demonstrate that men can be sustained in space for the time necessary to journey to, and return from, Mars; and that we have life-support systems that will operate satisfactorily during that time.

Dale Lawrence Jensen

Lawndale, Calif.