SAN FRANCISCO – NASA has approved a demonstration flight for DiskSat, the thin round satellite developed by Aerospace Corp.
Aerospace Corp. engineers are building four DiskSats and a DiskSat dispenser that they plan to send into low Earth orbit in 2024 to validate the technology.
“People ask me, ‘Can you really fly that? Can you keep it under attitude control?’” said Richard Welle, DiskSat inventor and principal scientist in the aerospace Mission Systems Engineering Division SpaceNews. “Compared to other things that are traditionally flown, it’s a very clumsy vehicle. Can you do the thermal management so you don’t crush yourself collecting all that solar power?”
DiskSats with a diameter of one meter are 2.5 centimeters thick. With the extensive area for solar panels, DiskSats could provide around 60 to 80 watts for the on-board electronics. A DiskSat with a rigid, extendable solar panel delivers an average onboard power of 100 to 160 watts.
Much of the power is probably used for propulsion. During the demonstration mission, Aerospace plans to fly DiskSats in a very low Earth orbit.
A pair of DiskSats, launched from a rocket at an altitude of about 500 kilometers, will be maneuvered down to a 250-kilometer orbit. Using anti-drag propulsion, mission planners intend to keep the DiskSats at this altitude for more than a week before launching them into a higher orbit.
The second pair of DiskSats will fly in an eccentric orbit with a perigee below 200 kilometers.
“The propulsion system has enough thrust to balance the drag in a circular orbit of about 230 kilometers,” said Welle. “But in elliptical orbit, you can go lower provided you have time at higher altitude to do the drag makeup.”
At the end of April, Aerospace started the 18-month development campaign for the DiskSat demonstration mission. No launch vehicle has yet been identified.
Aerospace plans to show a DiskSat model at the Small Satellite Conference at Utah State University in August.
“We look forward to speaking to anyone interested in flying a DiskSat,” said Welle. “We plan to develop a DiskSat standard, analogous to the CubeSat standard. We will define the interface between the satellite and the launch vehicle with the idea that it can be used in ride-along mode.”
Aerospace engineers develop a dispenser to release the circular spacecraft.
“In the long run, you can have flights with 20 DiskSats in a single dispenser,” said Welle. “We are developing an ejection mechanism that releases them one at a time with a reasonable time in between to ensure separation between adjacent slices in the stack.”
Welle sees key advantages in circular DiskSats over CubeSats.
In terms of performance, an eight-kilogram DiskSat with an extendable panel can easily provide 100 watts of average onboard power. To provide the same performance, a CubeSat with retractable panels would weigh about 30 kilograms, Welle said.
With higher power and lower mass than CubeSats, DiskSats could use electric propulsion to dramatically alter their orbits. For example, a 10-kilogram DiskSat could move from near-Earth to geosynchronous or even lunar orbit.
In addition, the 2.5 cm rim of a DiskSat would experience little atmospheric drag, allowing the miniature satellites to operate at low altitudes. There is growing interest in very low orbits where sensors can collect high-resolution images of the Earth.
“Operating DiskSats under 300 kilometers is straightforward,” said Welle. “That gives you a whole new orbital regime that won’t be overpopulated by other satellites.”
DiskSats are lightweight composite structures with hollow interiors. Components can be distributed throughout the internal volume or grouped in a central avionics bay.
“There’s a lot of volume that’s spread out and easily accessible,” said Welle. “It greatly simplifies the manufacturing process.”
Additionally, DiskSats in low-Earth orbit are likely to quickly re-enter Earth’s atmosphere once their mission is complete. Without attitude control, a DiskSat in a 600 km orbit will re-enter the atmosphere in about two and a half years.
“If the attitude control system fails, the satellite crashes,” said Welle. “That will increase drag by an order of magnitude.”