Solar storms captured the imagination of much of the American public earlier this year when auroras became visible well south of their usual northern ranges. As the Sun enters a new solar cycle, these storms will become more frequent, and the dangers they pose to Earth's infrastructure will continue to grow. Currently, most of our early warning systems warn us just minutes before a potentially destructive impending geomagnetic storm event. So a team of researchers from Sapienza University in Rome and the Italian Space Agency proposed a plan to send a series of detectors to a point in space from which they could give us early warning. And they want those detectors to stay in place without rockets.
The mission, officially named Helianthus, the sunflower, was first unveiled at the 6th International Space Sailing Symposium in June 2023. In a presentation, the Italian scientists explained that the mission goal is to provide different levels of alert for geomagnetic storms. But more importantly, the mission design would give humanity 100 minutes of advance warning for fast-moving solar storms, and a large solar sail would fully control the mission.
Currently, warning times for solar storms are a few minutes at best because the detectors that monitor them are in low Earth orbit. To enable much earlier warning times, Helianthus would place a series of specially designed detectors at a point called Sub-L1 in the Sun-Earth system. Although it is unclear what “Sub-L1” means in this context, a typical Sun-Earth Lagrange point is about 1.5 million kilometers toward the Sun – about four times as far as the Moon is from Earth.
Fraser has a weakness for awnings, as he describes here.
The hardest part of the Helianthus mission is getting there with a solar sail. Most solar sails use photons to move outward in the solar system, because the source of those photons is the Sun, which by definition forms the inner part of the solar system. So it seems counterintuitive to get to a point closer to the Sun than Earth and then stay there.
How they plan to achieve this is the subject of one of several papers from the research team behind the project. Others describe the instruments, such as a lightweight coronagraph and an X-ray spectrometer, and even structural components, such as the booms used to deploy the solar sails and the membranes that will make up those sails.
Some of the most interesting research described in these papers shows how Helianthus would maintain its position at a point below L1 while its solar sail was still fully deployed. Rather than using rockets for station-keeping, the mission plans to use a series of electrochromic or liquid crystal actuators to perform about four station-keeping maneuvers per year.
Shade sails have been around for some time – Fraser explains what they do.
The development of most of these systems and methods is being driven by the Italian Space Agency, which is committed to improving the development of its staff in these areas. As stated in one of the documents, they intend to achieve a “sophisticated national development” in the field of solar sail propulsion. And the geomagnetic storm tracker is not their only use case – the same researchers have also planned an Earth-Mars transfer orbit using the same solar propulsion technology.
It is currently unclear whether Helianthus has the financial means to make it to actual operation. Although some prototypes of the lightweight instruments have already been built, a lot of engineering work still needs to be done before such a solar sail mission sees the light of day. If this is to succeed, the Italian space agency must show how committed it is to the idea.
Learn more:
Boni et al. – Structural response of the Helianthus solar sail during attitude maneuvers
Vupetti et al. – ASI Project Helianthus: Solar photon sailcraft for early warning of geostorms
UT – Solar sails could reach Mars in just 26 days
UT – NASA’s new solar sail has been launched and will soon be deployed
Cover image:
An image of the Light Sail 2 spacecraft with its solar sails extended.
Photo credit: Josh Spradling / The Planetary Society
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