From Early Sounding Rockets to Operationally Responsive Space
WASHINGTON — For more than 60 years the U.S. Naval Research Laboratory has pioneered some of the nation’s most important space capabilities, including GPS and space situational awareness. Although the laboratory’s role in space development has diminished over the years with the emergence of other organizations dedicated to that purpose, it continues to push the envelope both in space technology and in applications.
The lab’s space-related work has its origins in the 1940s with the development of instruments for studying the atmosphere. Balloons were used to lift instruments to the lower atmosphere, but the lab recognized it would need a rocket to study the upper atmosphere. Germany developed the world’s first suborbital rocket, the V-2, during World War II, and several of those rockets were brought to the United States following the war. But because the V-2 could not be controlled once its engine shut down it was not suitable for the research the lab wanted to do.
A handful of Naval Research Lab scientists were tasked with developing a rocket that could stay very stable after main-engine shutoff for such purposes as pointing cameras. These scientists comprised the group that eventually became the Naval Center for Space Technology (NCST), one of the lab’s four research divisions. Along with the Glenn L. Martin Co., one of Lockheed Martin’s original corporate ancestors, NCST developed the Viking sounding rockets, 12 of which were launched from 1949 to 1954. Viking pioneered rocket technologies that are still used today, including gimbaled motors for steering and compressed gas jets for maintaining vehicle stability after engine shutoff.
Viking helped pave the way for the Navy’s Vanguard project, which would be the nation’s first attempt to launch a satellite. After the Soviet Union launched Sputnik in October 1957, the United States was desperate to catch up and two months later attempted to launch the Vanguard TV3 satellite aboard a Vanguard rocket. The launch failed, and two months later the Army successfully launched the first U.S. satellite, Explorer 1. The Navy’s second attempt in March 1958 successfully placed the Vanguard 1 satellite into orbit.
NCST is also the one of the architects of the capability known today as space situational awareness, which refers to the ability to detect and track objects in Earth orbit. After Sputnik, the United States realized the Soviet Union would be capable of using satellites for surveillance and had no way of knowing when a spy satellite might be overhead. The Navy conceived of a string of antennas that would emit radio waves into space and receive a return signal any time the waves bounced off a satellite that passed above. In the span of two years, nine sites were built across the country from Georgia to San Diego, forming the basis for the Space Fence that is still operated by the Air Force today.
In order to refine and calibrate the tracking capabilities of the ground-based network, the NCST came up with the idea of putting extremely precise atomic clocks aboard satellites. This innovation eventually led to the development of the GPS satellites, which use onboard atomic clocks to provide precise position, navigation and timing information.
Today, the NCST and several other small space technology groups within the Naval Research Lab are focused on developing one-of-a-kind spacecraft and sensors for a variety of civil, military and intelligence community customers. Most of the Naval Reseach Lab’s $1.17 billion budget this year does not come from a dedicated Navy funding line, but from sponsor-funded research projects, meaning the lab is constantly competing for new business.
The NCST recently built the TacSat-1 satellite in coordination with the Pentagon’s Operationally Responsive Space Office and the Air Force Space Test Program, for example. TacSat-1 was intended to be launched several years ago, but lost its slot on the manifest due to technical issues with its Falcon 1 launcher. A similar satellite, TacSat-2, was launched in the meantime, and TacSat-1 remains on the ground with no firm plans for launch.
Built by the Air Force Research Laboratory, TacSat-2 includes an NCST-supplied Automatic Identification System (AIS) coastal ship-tracking demonstration payload. Any ship coming into U.S. waters must transmit an AIS signal containing information including its location, speed, course and home port. AIS receivers on the shoreline can detect ships out to a range of only about 30 kilometers, so having a space-based constellation for tracking ships anywhere on the oceans would be beneficial, NCST Director Peter Wilhelm said in an interview. Wilhelm has worked at NRL for 50 years and has been in charge of NCST since 1986.
The AIS payload demonstration was a success, and now the NCST hopes to build a full constellation of 30 AIS satellites. The Office of Naval Research funded NCST to develop the system through critical design review, which will happen later this year. The NCST hopes to secure $50 million to $60 million in funding in the coming years to build the first six satellites for the constellation, which would launch on a single rocket. Wilhelm is hopeful that other countries would participate in developing the full constellation in exchange for access to its services.
The NCST also built the TacSat-4 satellite, one of a handful of satellites awaiting launch aboard the Air Force’s new Minotaur 4 rocket, which has been delayed with technical troubles. TacSat-4 features a standardized spacecraft platform, or bus, that the NCST developed along with the Johns Hopkins University Applied Physics Laboratory, and an Ultra-High Frequency payload for mobile communications.
The satellite will be placed into a highly elliptical orbit to provide roughly six hours of dwell time over a region of the world; four such craft, properly sequenced, can provide continuous coverage of any desired region, Wilhelm said. Typically such orbital schemes are used to cover extreme northern latitudes, which are beyond the reach of communications satellites operating in geostationary orbit, but Wilhelm said the principle applies to other areas as well.
“Right now we’d like to have more comms in Afghanistan and Iraq,” Wilhelm said, noting that the military’s current operational UHF satellite constellation is degrading and the next-generation system is behind schedule. “This satellite could help.”
In addition to these near-term technology demonstration programs, the NCST has a portfolio of advanced research projects. One such project in early development aims to demonstrate using the plasma, or ionized gas, that surrounds the Earth to propel spacecraft. To do this, two small satellites connected by a kilometer-long, electrically conducive tether would be deployed. One of the satellites would collect electrons and beam them wirelessly to the other, which would send the resulting charge back to the first satellite via the tether. The completed electric circuit should create force that can move the satellites up or down in orbit without using traditional propellant. The technology is now being studied in the NCST’s vacuum chambers, and the satellites could be ready for launch in three years to five years if the project gets funded.
“There’s a lot of work to be done, but this might be a technique for moving from orbit to orbit to collect debris,” Wilhelm said.