For the satellites spinning around Earth, using electricity to ionize
and push particles of xenon gets them to go where they need to go. While
xenon atoms ionize easily and are heavy enough to build thrust, the gas is
rare and expensive, not to mention difficult to store.
Thanks to new research, we could soon have an alternative. Enter
iodine.
Full in-orbit operation of a satellite powered by iodine gas has now been
carried out by space tech company ThrustMe, and the technology promises to
lead to satellite propulsion systems that are more efficient and affordable
than ever before.
"Iodine is significantly more abundant and cheaper than xenon, and has the
added advantage that it can be stored unpressurized as a solid," says Dmytro
Rafalskyi, the CTO and co-founder of ThrustMe.
While earlier ground-based tests of iodine propulsion engines had been
promising, getting it working in space is the clearest sign yet that this
can be the future of small-scale spacecraft engines – and that our
exploration of space can practically continue.
The team used iodine to fuel a 20 kg (44 pound) CubeSat satellite with an
engine named the NPT30-I2, which was launched on 6 November 2020. Maneuvers
were carried out successfully, and iodine was shown to achieve higher
ionization efficiency than xenon too.
Besides the benefits we've already talked about, iodine-based systems could
also be built in significantly smaller and simpler forms than current
satellites: unlike xenon and other propellants, iodine can be stored on
board in its solid form before it's converted into a gas, so there's no need
for bulky, high-pressure gas tanks.
"The successful demonstration of the NPT30-I2 means we can proceed to the
next step in the development of iodine propulsion," says Rafalskyi.
"In parallel with our in-space testing we have developed new solutions
allowing increased performance and have commenced an extensive ground-based
endurance testing campaign to further push the limits of this new
technology."
Tens of thousands of satellites are expected to be launched into orbit
across the next decade, so finding ways to make them as efficient and as
affordable as possible is key if we're to keep on exploring and analyzing
Earth and the Universe around us.
The use of iodine in making satellites more affordable, more efficient and
more compact has multiple potential benefits in how satellite constellations
can be deployed, trained to avoid each other, and disposed of when they've
reached the end of their useful lives.
Challenges remain: iodine is highly corrosive, which means ceramics are
required to protect the satellite parts, and at the moment iodine engines
aren't as responsive as their xenon counterparts. However, this is a major
step forward for the technology.
"Publication of these historic results is not only important for ThrustMe,
but also for the space industry in general," says ThrustMe CEO and
co-founder Ane Aanesland.
"Having our results peer-reviewed and publically accessible provides the
community with further confidence and helps to create a benchmark within the
industry."
Reference:
Dmytro Rafalskyi et al, In-orbit demonstration of an iodine electric
propulsion system, Nature (2021).
DOI: 10.1038/s41586-021-04015-y