This is the third of three articles covering NASA’s “State of the Art of Small Spacecraft Technology” report.
NASA recently released an update to its “State of the Art of Small Spacecraft Technology” report, which aims to provide the most current information on the state of small spacecraft technology — mainly focused on the CubeSat market. The report is divided into multiple sections.
Below are a few key highlights from the report.
Integration, Launch, and Deployment
The commercial satellite launch market deserves its own article … or 50. As of 2017, nearly 62% of all satellite launches fell under the nanosat category, with forecasts predicting that number to increase. Thus far, CubeSats have benefitted from cheaply “hitching a ride” on larger launch payloads that fit most, but not all, of the capabilities of a launch platform, but NASA predicts that this will change in the future.
Launch platforms can be divided into Primary Payload Launchers (PPLs), which focus directly on nanosat delivery, and Secondary Payload Launchers (SPLs), which deliver nanosats after delivering the primary payload.
Of the PPLs, the platforms in operation include Electron by Rocket Lab, based in New Zealand, as well as Minotaur and Pegasus by Northrup Grumman, based in the United States.
The SPLs are too numerous to list, but a few popular ones include the Antares by Orbital Sciences, Ariane 5 by the European Space Agency, Delta IV by United Launch Alliance, Falcon 9 by Space Exploration Technologies, Long March by China Academy of Launch Vehicle, and Soyuz by OKB-1 (Russia).
Ground Data Systems and Mission Operations
The field of ground data systems and transmission needs the most improvement. Due to several factors, such as funding and RF licensing requirements, ground-based communication and control systems experience much resistance.
Many of the CubeSat operations are forced to use amateur or academic-based data transmission systems, which are often unable to communicate quickly with their satellites and unable to communicate with multiple satellites at a time. Furthermore, the inability to downlink data quickly to ground stations means that many satellites cannot communicate their relevant data in one pass and must wait for the next orbit.
No comprehensive, universally accepted ground-based or space-based communication system for CubeSats exists. Startup companies are now trying to fill this void with ongoing development of turnkey solutions for many CubeSat teams.
Passive Deorbit Systems
Leftover space debris following satellite deployment has become a growing problem and is now under intense scrutiny by NASA. Any object, no matter how small when put into orbit, will stay in orbit forever unless acted upon by an outside force. This means that every nut, bolt, and spec of paint that ever left Earth will not come back unless something cleans it up. It is estimated that there are 750,000 free-floating particles and pieces in orbit, of which 94% is considered to be space debris, totaling 7,500 metric tons.
In recent years, NASA has taken steps to limit the addition of new debris, mandating that all spacecraft now be placed on a decaying orbit back into the Earth’s atmosphere or into a graveyard orbit for long-term storage. This has become problematic for satellite manufacturers, because such orbits mean that extra fuel must be spent in order to deorbit the satellite.
NASA has developed the Exo-Brake as a low-cost solution to the deorbit problem. The Exo-Brake is a cross-parachute that is deployed from the spacecraft rear in order to increase drag and slow the craft.
In addition, two emerging low-cost technologies are also aiming to solve this problem: the solar sail and the electromagnetic tether. The solar sail relies upon light pressure from the sun to slow the CubeSat down in order to cause the satellite to burn up in a decaying orbit. The electromagnetic tether similarly causes the satellite to slow down, but instead interacts with the Earth’s magnetic field as the satellite orbits in order to generate the deceleration force. Both systems have launched on CubeSats and are being currently tested in space.
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