Swarms of satellites each weighing less than 100 grams and not much bigger than a personal digital assistant or even a cell phone could soon be heading for space. These so-called femto satellites could quickly displace the behemoths of yesteryear that weigh in at up to a tonne and may revolutionize applications in telecommunications, military, entertainment, science, weather and climate forecasting, at much lower fabrication and launch costs.
We’ve all seen TV footage of those enormous rockets thrusting upwards from distant launchpads, seemingly hanging in the air and yet accelerating upwards at incredible speed in order to pierce the sky and enter orbit.
Onboard such a rocket, will usually be a payload, a satellite, destined for earthly orbit, a device that until recently may have weighed more than a tonne. These enormous satellites cost a fortune to build, even more to launch, and still more to cover the insurance premiums. Smaller satellites would be so much better for dozens of reasons and over the last decade, their size has dropped below the one tonne mark, and then to the few hundred kilograms, more recently to micro satellites that weigh a few tens of kilograms.
However, there was never any reason not to build something smaller that could be reduced in size, and so we have seen in recent years the launch of a flotilla of “nano” satellites that weigh between 1 and 10 kg, then pico satellites that are just a few hundred grams, and soon we could see femto satellites that weigh less than 100 grams. [NB the nano, pico and femto referred to here are arbitrary descriptors of the relative mass of the satellites. For more on the true meaning of nano, pico, and femto]
Warren Leary, writing in the New York Times ago, described the promise of microelectromechanical systems (MEMS) as applied to satellite technology and hinted at the possibility of a satellite-on-a-chip. He discussed the work of Siegfried Janson and colleagues at The Aerospace Corporation, in El Segundo, California, and quoted him as describing, ‘Fully integrated satellites that could be mass produced cheaply by the hundreds and sent into space in groups to perform a variety of tasks.”
We are not quite at the stage of sending out satellite swarms but the miniaturisation of satellites has continued apace with designs, such as the CubeSat system, allowing researchers and companies to design satellites based on a standard payload that
“Pico-satellites are viable development platforms for testing new technologies in the space environment, explain M.W.R. Alger and K.D. Kumar Department of Aerospace Engineering, at Ryerson University, Toronto, Canada. Writing in the International Journal of Manufacturing Research (2008, 3, 48-79), “The opportunities given to fly the earliest pico-satellites as secondary payloads have benefited all facets of the space community both by effectively training the next generation of spacecraft designers and by pushing the boundaries of space technology at largely reduced risk and cost.”
They point out that these pico satellites have a lot to contend with, “Space is a very unforgiving environment, with many different hazards then those found on the Earth. The major hazards to overcome are: radiation, temperature variations, space debris, and out-gassing.”
The first pico satellites, weighing less than a kilogram, flew on the OPAL and Sapphire missions and subsequently their success led to the CubeSat standard, with devices about 100x100x100mm. “The strategy for deploying these satellites in orbit involves launching a group of small pico-satellites in a deployment device known as a Poly Pico-satellite Orbital Deployer (PPOD),” the researchers explain, “The PPOD integrates with the launch vehicle and carries three normal sized CubeSats.” Several of the most successful CubeSats have been built by students at various universities. Now, many other teams around the globe have been building their own CubeSats.
“Femto-satellites [click the graphic for a better view] will be the next new class of satellites,” the researchers say, “There is a possibility of shrinking the capabilities of a typical pico-satellite bus (attitude control, imaging missions, communications etc.) on to a single chip.” It is possible that current consumer manufacturing processes for personal digital assistants and cell phones will drive the development of femto satellites. Scientists have already developed a prototype configuration – a Ryerson Femto Formation Flying Experiment (RyF3ex) spacecraft as a demonstrator technology. This femto satellite will simply report back its altitude to a ground station.
Femto satellites will have several limitations, however, and are more likely to be launched as a swarm by a larger spacecraft. “Femto-satellites derived from this technology maybe an interesting approach for deep space exploration where a larger satellite could launch a cluster of disposable femto-satellites to examine a planet or asteroid of interest and after completing this mission, the larger satellite could orbit another planet and deploy a new cluster to do a similar mission,” the researchers add.
Sharp-eyed readers will recall I mentioned this impending item in an article on the Earth’s escape velocity entitled 40320, Such a Significant Figure, just so you know I do occasionally pull the threads together.