Science in Limbo - Rockets in Question

Science in Limbo

Rockets in Question

Space News Staff Writer

WASHINGTON-Many U.S. planetary scientists are finding it difficult to get a jump on the next competition for NASA's low-cost Discovery spacecraft because of persistent questions about the launch vehicles that will be avail-able to them.

The goal of the Discovery project is to produce inexpensive planetary spacecraft frequently. In the past, NASA has poured billions of dollars into a few large spacecraft launched years apart.

Before scientists spend too much time and money preparing for the next Discovery competition, which is slated to begin in late May, they want to know whether they should plan to launch on NASA's planned Med-Lite launch vehicle or some other rocket, one Discovery competitor said.

Med-Lite vehicles are supposed to fill a payload gap between small vehicles, such as the air-launched Pegasus rocket built by Orbital Sciences Corp., and the larger Delta 2 rocket built by McDonnell Douglas. But details of the Med-Lite contract are tied up in negotiations between McDonnell Douglas and NASA.

Nevertheless, NASA managers have assigned the Med-Lite as the vehicle of choice for all new Discovery missions, with the rocket's cost estimated at $34 million per launch. However, the real cost of the rocket and its range of launch capabilities have not yet been announced by NASA and McDonnell Douglas, which are concluding talks for the Med-Lite contract. For most of the competitors, the thrust of the rocket will determine the size of the spacecraft that will be proposed and the celestial bodies that will be explored.

Karen Poniatowski, manager of new programs and integration in NASA's launch vehicles office, said questions regarding the capability and cost of rockets available for future Discovery missions will be resolved before the next program competition gets started. These issues are under study as part of a comprehensive re-examination of NASA's expendable rocket buying practices that is expected to wrap up in six to eight weeks.

While the Med-Lite is the baseline vehicle, scientists proposing spectacular missions may be allowed to launch payloads on the larger and more expensive Delta 2, said Mark Saunders, NASA's Discovery program manager. If a mission needs a Delta 2-which can cost up to $55 million- Saunders will have the flexibility to shift money from his research and development account to cover the additional cost.

"If the right decision is to move money around to get the best mission and the best science for the dollar, then that's what I'm going to do," Saunders said.

Each Discovery spacecraft must cost no more than $150 million to build. The total mission, including the launch vehicle and ground operations, must not exceed $270 million.

Missions that approach the cost ceiling will be rare, Saunders said. ''It has to be something spectacular," he said.

NASA plans to spend $100 million to $120 million on the Discovery series annually through the next five years, which is essentially flat funding, Saunders said. That would fund one mission about every two years.

The size and cost of the spacecraft that will be accepted in the Discovery project has been a contentious issue for scientists. When NASA selected the $63 million Lunar Prospector mission during the last competition, the scientists worried that this low-cost mission had set a new, de facto cost-ceiling for each Discovery mission.

The losers also complained that NASA had emphasized cost over scientific value. "They had a certain weighting factor that was heavily influenced by cost and not necessarily the total science achievement," said Christopher Russell, a planetary scientist at the University of California at Los Angeles. During the first competition, Russell proposed a spacecraft called Diana that would have rendezvoused with a dormant comet. That project was not
selected by NASA.

Russell said the launch vehicle dilemma would not affect him because his spacecraft would need only a small rocket for a trip into deep space. After reaching orbit, his spacecraft will use solar electric propulsion to boost its speed.

This type of propulsion will be tested separately in NASA's New Millennium project and should be proven by the time NASA is ready to launch the next Discovery missions, Russell said. The engine will convert sunlight into electricity and use the electricity to excite molecules of xenon gas. The xenon gas will then be blown through a grid at the back of the spacecraft to generate forward thrust.

''I'm sympathetic to their struggling," Saunders said of scientists who have complained about the penchant for low cost programs. "In the past, NASA has said cost would be important but it wasn't. In this program we said cost was going to be a major factor and we actually did what we said we were going to do. I think they were surprised," he added.

At a June 1995 workshop in Washington, Discovery scientists also complained about the amount of time and money they were being asked to invest to develop their proposals. Saunders has come up with a compromise. The next competition will be divided into two phases. In the first phase, NASA will select a group of winners based primarily on their expected scientific return. Then in the second phase, NASA will require the balance of the cost details and select the winners. The new missions will be selected in March 1997.

Four Discovery missions have been selected so far: the Near Earth Asteroid Rendezvous spacecraft, scheduled to be launched Feb. 16 aboard a Delta 2 rocket; the Mars Pathfinder lander, which is scheduled for launch in December; the Lunar Prospector spacecraft, scheduled for launch in October 1997; and a spacecraft called Stardust, which will fly through the tail of a comet and carry a chemical sample back to Earth.

Staff writer Warren Ferster contributed to this article.

Reprinted with premission of Space News Volume 7 Number 6 February 12-18, 1996


Wednesday, 31-Dec-1969 18:00:00 CST