Small satellites take flight

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(By Igor Lenchenko, Nanyang Technological University, and Kateryna Bazaka, Australian National University for 360info)

Processions of small satellites darkening the sky have provoked the ire of astronomers, but their potential for humanity is enormous.

When it comes to rockets, Starship, one of SpaceX’s most ambitious projects to date, certainly packs a punch. With more than 100 tonnes of payload and slated for orbital testing as early as 2022, this gigantic, fully reusable system is designed to one day help humans colonize Mars.

Much closer to home, this could help SpaceX quickly assemble constellations of small commercial satellites. SpaceX’s Starlink satellites already provide high-speed internet access to remote locations. Starship will deliver satellites into orbit at a significantly lower cost. Capable of carrying around 400 Starlink satellites at a time, it will cost around $2 million to $10 million per launch.

Read | SpaceX now has 1,469 active Starlink satellites: Musk

For comparison, a partially reusable Falcon 9 rocket launches around 50 Starlink satellites at a cost of around $50 million. Even with the possibility of setbacks, it is very likely that Starship or a similar system will soon deliver a large number of orbiting satellites.

What would that mean for us on Earth? For consumers, this will likely mean better access to satellite services, with better quality and lower cost.

Starlink’s internet coverage will improve and other smaller but still large constellations such as OneWeb will offer high-speed internet, geodesy, navigation, communication, as well as weather monitoring and forecasting.

Indeed, a distributed network of small satellites offers greater physical coverage, better network robustness, and much better data transmission speeds. It is also possible to collect much more high-quality data. And SpaceX and OneWeb aren’t the only industry players looking skyward.

In addition to big tech players, small businesses, universities and government agencies will be able to afford to pay to launch their own satellites. With SpaceX planning to have a large fleet of starships, it’s likely that Starship and its relatives will be available to others in much the same way the SmallSat Rideshare program uses Falcon 9.

Read | Satellite attack: the growing arms race in space

Various industries will seek to transfer their technologies into orbit to harness the benefits of weightlessness, from 3D printing biological tissues and organs to growing protein crystals for pharmaceuticals. Affordable science experiments made available to research institutions large and small will lead to new discoveries and technological advances.

For those developing and operating satellites, the fact that low Earth orbit is becoming an increasingly crowded place poses new challenges for collision avoidance and traffic control. Right now, there are around 7,000 satellites – some of which are operational and some of which are dead – orbiting the Earth.

The development of Starship has allowed SpaceX alone to revise its initial plans from 12,000 to 42,000 satellites – a venture that represents a 600% increase on the combined launch of each satellite to date. The constellation’s first collision avoidance maneuver was performed in 2019, when the Aeolus satellite operated by the European Space Agency used its thrusters to avoid a collision with one of the Starlink satellites.

In the near future, constellation collision avoidance maneuvers will likely become a daily reality.

In addition to the global control systems capable of coordinating such a population of satellites in the future, the propulsion systems of the satellites are essential to ensure the maneuvers and, above all, the deorbiting at the end of their lifetime in order to avoid they do not become space junk.

The drastic miniaturization of electronics has allowed developers to pack functions previously available only in much larger satellites into something the size and weight of a microwave oven. Rapid prototyping and advanced manufacturing have helped simplify and affordability of development and manufacturing processes, making them affordable for small teams.

The miniaturization of propulsion thrusters presents several challenges, however. Many small satellites use electric propulsion thrusters because of their superior efficiency. However, electric propulsion thrusters lose efficiency when they are miniaturized.

Then there are the challenges with propellants and their complex system of tanks, valves, tubes and gauges. Xenon is very expensive and in high demand. Krypton is less efficient, so you have to carry more propellant on board.

But iodine could be a game-changer for miniature satellites. As a solid fuel it offers a combination of simplicity, much lower cost and reasonable efficiency. Solid iodine was recently successfully tested in space.

The design cleverly used iodine’s ability to turn from solid to gas at relatively low temperatures, which meant that fuel could be stored without a tank and then turned into gas with only a small energy input. The rapid resolidification of the gas when the heater is turned off allowed designers to remove the inlet valves, further simplifying the system. However, this system and others like it will need to undergo further development before they can fully meet the needs of satellites in commercial constellations.

Despite the exciting potential of thousands of miniature satellites circling the world, providing services to humanity, and skilfully flying away from collision, not everyone is looking forward to this future. An overabundance of bright satellites in lower orbit can literally obstruct the view of stargazers, both professional and amateur.

Astronomers first raised these concerns shortly after the launch of the first Starlink satellites. To minimize disruption, SpaceX designed a DarkSat, a Starlink satellite designed to drastically reduce brightness. However, the design did not solve the problem and a new, more advanced design named VisorSat – a satellite with deployable visors, was proposed.

Another concern is radio astronomy. Reducing the harmful effect of mega-constellations on radio telescopes is a much more complex problem to solve, if not at all solvable. It remains to be seen what impact 42,000 satellites, even dimmed ones, will have on our ability to continue making discoveries about distant galaxies and the big bang.

It may well be that the very satellites interfering with our ability to study the universe from Earth are the ones that will provide the next round of advances in astronomy. In astrophysics, for example, interacting satellites can function as several eyes separated by thousands of miles, observing Earth and distant planets from different angles and gaining information that cannot be collected by a single satellite.

We have the technology and the will to expand our physical world into Earth orbits. Despite the bumps and challenges along the way, the exploration and exploitation of near-Earth space will be the next phase of humanity’s expansion of our world.

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