Once in Orbit, Components Would Be Connected Physically or Wirelessly
SUMMERLAND KEY, Fla. — The Pentagon’s Defense Advanced Research Projects Agency is about to start a new research effort that will test the feasibility of dividing large satellites into critical subsystems and launching those components separately into orbit. Once there, those components would be joined together whe ther physically or more likely wirelessly to act like one satellite.
If the concept works, it might someday be possible to launch a large satellite on a handful of small, 453.6-kilogram -payload rockets like those DARPA has helped private companies develop, said DARPA Director Anthony Tether, during an April 10 panel discussion at the National Space Symposium in Colorado Springs.
DARPA hopes to cut launch costs while reducing the pain of launch failures. “You lose a booster it doesn’t kill you because you’ve only lost one of the components,” Tether said.
DARPA plans to invite U.S. satellite designers to compete for the program, known as F6, through a Broad Agency Announcement scheduled for release in the “late spring or early summer,” of this year, said Owen Brown, the F6 program manager. A demonstration mission could be conducted in 2010 or 2011, said DARPA spokeswoman Jan Walker.
The program gets its name from six “F” words — future, fractionated, fast, flexible, free flying — and from the phrase “Spacecraft united by I-nformation e-X-change,” Brown said. But in typical DARPA fashion, the name also has marketing in mind. F6 is a play on the Fujita Tornado scale: “An F6 is a tornado of unimaginable strength, and no one has ever seen one before,” Brown said.
The goal is to demonstrate a new approach to space missions, rather than a specific new type of spacecraft, Brown said. In place of real sensors, companies would be free to launch “mass simulators” that would store and download up to an hour’s worth of Flash memory as though it were real data, he said.
DARPA is not the first U.S. agency to explore the idea of dividing spacecraft into separate components. NASA has studied the concept of launching astronomy sensors separately into space and merging their observations as elements of a single, giant “sparse aperture” telescope. The Air Force Research Laboratory’s (AFRL) space vehicles directorate in Albuquerque has looked at sparse aperture concepts for reconnaissance applications. In 2003, AFRL canceled a program called TechSat 21 that would have launched three small, free-flying radar satellites that would act as one radar system.
The F6 program is distinct from those efforts because it is not specifically geared toward launching large arrays, Brown said. Sparse-aperture proposals usually call for launching flocks of almost identical satellites, but the F6 concept calls for launching separate spacecraft, each with a specific function, that allows multiple small spacecraft to work as a single satellite.
“One node might be a computing element. One node might be a downlink element. The other element might be the payload element. We’re literally talking about taking a spacecraft apart and flying various parts of that spacecraft separately,” Brown said.
Brown declined to say how much money DARPA has allocated for the new program, or how much funding each contractor might receive in the initial concept phase.
“It’s obviously going to depend on how many performers are in the first phase,” he said.
Tether said the satellites could be joined together one of two ways: either “physically, like Orbital Express,” he said, referring to the robotic-servicing demonstration mission DARPA currently has in orbit, or “magnetically somehow.”
Brown left no doubt that his preference for F6 would be for wireless links. “F6 is sort of the next step: Now, to upgrade or replace an element doesn’t entail robotic servicing. It means that I simply fly a new element with that capability into a new cluster and it logs itself in,” he said.
Exactly what an orbital F6 demonstration would look like depends on the proposals that come in, Brown said. DARPA has chosen to issue a Broad Agency Announcement, rather than a more specific Request for Proposals, to give potential bidders maximum flexibility, Brown said.
“F6 will be mission non-specific. What we’re really trying to demonstrate here is an architecture, not a mission,” he said.
The contractors must assess the potential costs of the F6 approach compared to launching large, monolithic satellites on large launch vehicles, Brown said.
“Today’s paradigm says that the way to reduce life-cycle costs and provide the most utility is to cram as much payload into a large spacecraft and launch it on a large launch vehicle,” Brown said. “There’s an economy of scale there, but that really is bad because it creates inflexible systems, and it also creates risk-intensive systems.”
Once satellites are launched, they can’t easily be upgraded. “We all know about Moore’s Law,” Brown said, meaning the inevitable improvements in computer speeds predicted by Intel co-founder Gordon Moore. “We can’t take advantage of it” once satellites are in space, Brown said.