— While NASA’s planned Ares 5 rocket could be used to launch large and ambitious space science missions a decade or so from now, such missions could prove too expensive to ever come to fruition, a National Research Council (NRC) committee said in a report released Nov. 24. NRC’s Committee on Science Opportunities Enabled by NASA’s Constellation System assessed 17 proposed future science missions and how they would benefit from NASA’s Constellation launch infrastructure, which includes the Ares 1 crew launch vehicle, Orion Crew Exploration Vehicle and Ares 5 heavy-lift cargo launcher. The committee concluded that for science missions, Ares 1 does not offer capabilities much different from those already offered by the family of Evolved Expendable Launch Vehicles (EELV) operated by Denver-based United Launch Alliance.
The publication of the report coincided with NASA’s release of a draft request for proposals (RFP) for the first phase of Ares 5 development. NASA is collecting input from industry to help formulate an Ares 5 study contract RFP due out in January. NASA’s plans call for bringing Ares 5 on line in time for human lunar missions starting in 2020. Development of Orion and Ares 1 already are well under way, with the first crewed launch targeted for early 2015.
Space Studies Board was asked by NASA’s Science Mission Directorate in November 2007 to assess potential science missions that could be enabled by Constellation in the post-2020 timeframe as a tool for assisting with the upcoming decadal surveys the NRC will conduct to prioritize future NASA science missions.
Of the 17 mission concepts evaluated, the NRC committee said 12 were worthy of further consideration, including a human mission to near-Earth objects such as asteroids, an interstellar probe, an 8-meter monolithic telescope and a solar polar imager. The report said the other five missions examined could be launched on EELVs or would be better served by ground-based alternatives.
The cost of most of the missions considered potentially viable likely would exceed $5 billion, not including the considerable projected cost of launching the heavy-lift vehicle, the report said.
“There’s some exciting science that can be done on Ares 5, however, there’s a price tag with that and it can be expensive,” said George Paulikas, a retired Aerospace Corp. executive who served as chairman of the NRC committee.
To help keep costs down, the NRC committee said NASA should investigate the possibility of relaxing weight and volume constraints for the proposed missions rather than strive to pack out Ares 5’s massive lift capacity and larger shroud with as much spacecraft capability as scientists and engineers can envision. NASA estimates that Ares 5 will be able to lift about 188 metric tons of payload to low Earth orbit, an amount seven times more than the space shuttle can carry and roughly 50 percent more than the Apollo-era Saturn 5 could carry. “There is so much mass available that you might want to rethink how you design science missions to cut down the costs,” Paulikas said. “With the Ares 5 mass lift capacity, maybe you don’t have to go through the cost of light-weighting optics, but nobody knows whether that would work so we recommended NASA study it.”
Ares 5’s capabilities could have the greatest impact on five science mission proposals reviewed by the committee and ranked as “most worthy” of further study, the report said.
The missions, however, all are considered expensive, flagship-class undertakings that historically launch at rate of around one per decade.
“Virtually all of the science mission concepts that could take advantage of Constellation’s unique capabilities are likely to be prohibitively expensive,” the report said. “The committee notes that expensive space science programs will place a great strain on the space science budget, which has been essentially flat for several years and already is under strain from an ambitious slate of 85 flight missions.”
The missions include a monolithic space telescope whose 8-meter mirror would only fit inside an Ares 5 payload fairing, an interstellar probe, a
orbiter with probes, a solar polar imager and a solar probe. All of those missions are estimated to cost at least $1 billion, and some may cost more than $5 billion, the report said.
Other Constellation-enabled mission concepts identified as deserving further review include a 16-meter folded telescope designed to take advantage of the Ares 5’s nearly 9-meter payload shroud, a network of large radio astronomy antennas positioned on the Moon’s far side with the help of� NASA’s proposed Altair human lunar lander, and the Stellar Imager, a pair of 2-meter telescopes that would launch on a single Ares 5. All of these missions are estimated to cost more than $5 billion, excluding launch costs.
The report said that sending astronauts to explore near-Earth objects, another $5 billion-plus undertaking, is a human spaceflight mission that should be evaluated by the NASA’s Exploration Systems Mission Directorate, not the agency’s Science Mission Directorate.
Meanwhile, the report said that while Ares 1 is needed to deliver the Orion Crew Exploration Vehicle to orbit, it offers no advantages over existing EELVs for launching science missions.
“Ares 1 does low Earth orbit with people very well,” Paulikas said. “But in terms of science missions one wants to do, it’s comparable to a Delta 4 but not better.”
Where Ares 1 can help, along with Ares 5 and Orion, is in opening opportunities for small science missions to be launched as secondary payloads to fill extra capacity provided by the Constellation systems, Paulikas said. The secondary payload option has become more widespread in recent years as small missions seek an affordable launch option. Civil and military space missions are including secondary payloads more frequently to ease access to space.
“Things like that need to be considered now,” Paulikas said. “It’s very hard to change it once it gets going.”
Another advantage provided by Constellation is the possibility of human- and robotic-servicing of in-orbit spacecraft, but missions must be built with such access in mind, the report said, noting that costs may initially be higher but will be lower in the long run.
“Components with long lifetime ratings are more expensive than those with shorter ones,” the report said. “Servicing can mitigate this issue (since components need not have such long life spans), and replacing components with new technology can increase capability and capacity.”