'Economy' planet flights: NASA saves missions by saving money

Like a pauper who discovers he's a prince, the impoverished US planetary program is trying to claim its ''inheritance.'' That's the key concept in a new proposal to revive planetary exploration.

''Inheritance'' means a program in which successive projects and their spacecraft make maximum use of what has been done before. They share common support facilities, use much common or hand-me-down equipment, and develop new technology from what has gone before rather than starting from scratch to build custom hardware for each new project.

It also means adapting existing spacecraft designs, such as those of communications or weather satellites, for missions to the inner planets; or designing a general purpose, deep-space probe that is easily configured for many purposes.

By making the most of such inheritance and focusing each mission on only a few important objectives, the Solar System Exploration Committee (SSEC) of the National Aeronautics and Space Administration (NASA) says the US can have a productive solar-system program at an annual cost in 1984 of only $300 million. That's $50 million more than currently budgeted for planetary exploration - but it's a third of what the planetary program cost in its heyday.

Today, the US has only two authorized planetary missions. There is the Galileo project, which will place a spacecraft in orbit around Jupiter and send a probe into the planet's surface later this decade. And there is the Venus Radar Mapper, which is also at the top of the SSEC list.

The committee has just released the results of the two-and-a-half-year study which will become the basis for building a new solar-system program.

The proposed effort would be organized around four interrelated goals and implemented through the SSEC's ''Core'' program of what the committee calls a balanced mix of missions to the inner planets, to comets and asteroids, and to the giant outer planets. A new ''economy'' model spacecraft would be developed for outer-planet exploration. This is already being studied at the NASA Jet Propulsion Laboratory (JPL) in Pasadena, Calif.

The SSEC says its ''primary goal continues to be the determination of the origin, evolution, and present state of the solar system.'' It also wants a better ''understanding [of] the Earth through comparative planetary studies'' and a better ''understanding (of) the relationship between the chemical and physical evolution of the solar system and the appearance of life.'' This means studying comets and asteroids.

''These unexplored classes of chemically primitive objects promise to provide profound insights into the formation and early history of the solar system,'' the SSEC says.

Then there is an ambitious new goal for planet explorers - ''the survey of resources available in near-Earth space.'' This invokes visions of asteroid mining or prospecting on the moon. ''It is essential that the relevant research be done before actual use of such resources is contemplated,'' the report warns.

To meet these goals, the SSEC wants four high-priority Core missions:

* A Venus Radar Mapper to make a detailed survey of the planet. (Launch: 1988 . Data return: 1988-89.)

* A Mars Geoscience/Climatology Orbiter for atmospheric and surface studies. (Launch: 1990. Data Return: 1990-92.)

* A Comet Rendezvous/Asteroid Flyby. (Launch: 1990-92. Data Return: 1994-2000 .)

* A Titan Probe/Radar Mapper to study Saturn's largest moon (Launch: 1988-92. Data Return: 1995-97.)

The plan also lists a dozen other follow-up missions to planets, comets, and asteroids. But the big, costly spectaculars like the Viking-Mars project are missing. A central concept of this plan is to keep costs down by keeping missions lean and simple.

Another way to hold down costs is to use simple, reliable spacecraft that can be outfitted with various standard modules for specific missions. That's what Marcia Neugebauer, acting manager of the Mariner Mark II Development Flight Project at JPL, envisions for deep-space exploration.

Here, she notes, missions need spacecraft that can function reliably for 10 years or more. Such craft also must be able to carry out many of their tasks automatically. She says the spacecraft her group is designing can meet this need within the SSEC cost goal of a $300 million a year.

The SSEC study follows a National Academy of Sciences report deploring the eclipse of the US planetary program, and urging ''a critical level of flight activity, that is necessary for a healthy scientific program.''

This is what the SSEC plan provides. But the committee warns that this is also the minimum needed for healthy science.

''At this level of funding, planetary missions could be carried out with a frequency that will allow good use to be made of spacecraft inheritance and commonality of systems and personnel. With the present low rate of mission activity, such economies are not possible,'' the committee says.