Solar Activity and Astronauts: The Effects of Space Weather on Manned Missions

Increased solar activity can pose a variety of threats to mankind, but astronauts are particularly susceptible to space weather dangers. Not only are satellite communications vulnerable to solar storms, but astronauts are presented with serious and cumulative health risks when exposed to these space weather events.¹ Astronauts aboard the International Space Station must take shelter in heavily shielded compartments in the event of a solar storm; but while the International Space Station orbits within Earth’s magnetosphere, keeping the astronauts relatively safe, the planned Artemis mission to the Moon does not have that additional layer of protection, and as mankind presses outward to Mars, additional troubles are likely to be encountered.² Furthermore, predicted increased solar activity between 2026 and 2030 could mean significant delays in space exploration.³

Dangers to Communications Systems

One of the primary dangers of space weather with regard to manned missions is its ability to affect communications and electronics systems, which can leave astronauts exceedingly vulnerable. Solar activity—from the solar wind to mild flares to extreme coronal mass ejections—sends energetic particles careening through the solar system, and these particles can have devastating effects on a spacecraft’s communications and electronics systems. There are three main ways solar activity can disrupt these systems: surface charging, deep dielectric charging, and single event upsets.⁴

Surface Charging

The low-energy electron environment of space can interact with a spacecraft to cause what is known as surface charging, wherein the net transfer of positive or negative charge to a spacecraft is not equal, resulting in the spacecraft accumulating excess electrons or ions.⁴ If different parts of the spacecraft are made of different materials, they could charge to different levels, potentially causing an electric discharge that could have serious consequences, such as electromagnetic interference, loss of data, damage to sensitive instruments, and power loss.⁵ Different types of discharges include: flashovers (a discharge from one surface to an adjacent surface), punch-throughs (a discharge from an outer surface to an underlying ground), and discharge to space (a discharge from an outer surface to ambient plasma).⁵ While surface charging is most concerning for high power solar arrays, the utmost care and attention must still be paid when designing electrical systems in order to combat this phenomenon, and even then, many satellites experience weather-induced failures due to surface charging.⁴

Deep Dielectric Charging

Perhaps the most common and catastrophic issue with regard to the interaction of radiation and a spacecraft’s electronics, deep dielectric charging occurs when high-energy electrons and ions penetrate shielding materials and deposit charge on internal components, resulting in electric fields within spacecraft structures that can be damaging.⁴ Spontaneous discharge can occur when the electric field reaches sufficiently high values, while a meteor impact may also trigger a discharge, and the solar cycle is an important factor in determining the likelihood of these anomalies occurring, with a higher risk of occurrence during the declining or minimum phase of a solar cycle, when outer radiation belts tend to intensify.⁶ Again, material properties—such as conductivity, geometry, aging of material, and history of partial discharges—must be seriously considered when designing spacecraft in order to combat this phenomenon.

Single Event Effects

Sometimes, a single energetic particle can cause some serious trouble. Single Event Effects (or SEEs) describe just such occurrences, and they can take many forms, though there are two main categories: Single Event Upsets (or SEUs, are non-destructive errors that normally appear as bitflips in memory cells), and Single Event Latchups (or SELs, are potentially destructive hard errors resulting in a high operating current above device specifications).⁷ SELs can include MOSFET power burnouts, gate ruptures, frozen bits, and CCD noise.⁷ Spacecraft designers are concerned with two main causes of SEEs—cosmic rays and high-energy protons—and all mission-critical devices need to be tested for Single Event Effects, since a lone Latchup in a critical system can single-handedly ruin a mission.⁷

Direct Dangers to Human Health

Interference with and damage to communications and electrical systems can indirectly affect astronauts by ruining their instruments or cutting them off from civilization, but there are also elements of a manned mission that can be more directly hazardous to an astronaut’s health. There are two main factors that can pose direct health risks to astronauts on manned space missions: solar radiation and galactic cosmic rays.

Solar Radiation

As has been previously discussed, solar radiation can cause damage to non-living objects such as communications systems and electronic components, but solar radiation can cause damage to living beings, as well. Cosmic rays, solar flare particles, and radiation trapped in the Van Allen Belts are all cause for concern for astronauts. On Earth, humans are well protected from charged particles originating from the Sun by the planet’s robust magnetic field. In space, however, astronauts do not have the luxury of a magnetic field to shield them from solar radiation. Geomagnetic storms can drastically increase an astronaut’s likelihood of getting hit by a particle, which can cause radiation sickness, damage DNA, and ultimately lead to cancer.¹ Spacecraft are designed with this in mind, with increased shielding around areas where the crew will reside, and NASA monitors each astronaut’s cumulative radiation exposure throughout the course of their careers.¹

Galactic Cosmic Radiation

Galactic Cosmic Rays (or GCRs) are charged particles originating from beyond the solar system that move at nearly the speed of light, and they can cause serious damage as they pass practically unimpeded through a typical spacecraft or the skin of an astronaut.⁸ Galactic Cosmic Radiation consists mostly of protons, some alpha particles, and lesser amounts of nuclei of carbon, nitrogen, oxygen, and heavier atoms, and they are believed to originate from the powerful and luminous stellar explosions known as supernovae.⁸ During solar maximum, Galactic Cosmic Radiation passing through the solar system is actually lessened due to changes in the Sun’s magnetic field, solar flares, and coronal mass ejections.⁸ Galactic Cosmic Radiation can still be very harmful to space explorers, as they are difficult to shield against, and are often more hazardous than solar radiation.⁸

Manned Missions in Jeopardy

The International Space Station has areas that are well-shielded from radiation, especially around crew quarters, and furthermore, being in low-Earth orbit, astronauts aboard the ISS are largely protected by the Earth’s magnetic field.¹ A deep space mission beyond the Earth’s protection, however, will see astronauts encountering radiation levels that could be potentially life-threatening.⁹ Increases and decreases in overall solar activity over its 11-year cycle can be fairly well-predicted, but unexpected short-term events—such as solar flares, solar particle events, and coronal mass ejections—cannot be so easily predicted, and can seriously endanger astronauts.⁸

Missions to the Moon

Hazardous space weather could seriously threaten astronauts in NASA’s Artemis mission to the Moon. A journey to the Moon will take astronauts about 240,000 miles away—well beyond the relative safety of the 30,000-mile radius of Earth’s magnetic field, and safe long-term operations will require a coordinated system of satellites to monitor space weather in order to give ample warning for astronauts to take shelter when necessary.⁸ Though there are talks of further delays, the Artemis program aims to put astronauts on the Moon by 2024, but fears regarding increased solar activity during cycle 25 in the interval between 2026 and 2030 have scientists reconsidering their timing, since further delays could mean greater risks for the astronauts.²

Missions to Mars

SpaceX has proposed crewed missions to Mars, which could also be seriously threatened by space weather, as a journey to the Red Planet at its closest approach will take astronauts about 35 million miles away from Earth’s protection, with the average flight to Mars taking around nine months depending upon the launch timing and the orientation of Earth and Mars, and the journey could take up to three years.¹⁰ Protecting astronauts from harmful radiation on their journey must be carefully considered, and then considered further upon their arrival, since Mars has no global magnetic field to offer any sort of natural shielding. Specially designed shelters will be necessary to protect astronauts from deadly doses of radiation during periods of intense solar activity.⁸ Furthermore, if something were to go wrong during the trip and personnel back on Earth needed to be contacted, it can take up to twenty minutes for a radio signal to make it back to Earth—obviously double that for a roundtrip—and remote communication of any sort will be challenging for this same reason, and could be exacerbated considerably by space weather events interfering with or damaging communications systems.¹⁰

Conclusion

In conclusion, space exploration is already dangerous, and made even more so by extreme space weather events. Hazards to communications and electronics systems caused by surface charging, deep dielectric discharging, and single event effects can at best cause potentially dangerous temporary setbacks and at worst endanger crewed missions by damaging their instruments and cutting them off from civilization. Direct health hazards posed by solar radiation and galactic cosmic rays can cause radiation poisoning, damage DNA, and ultimately lead to chronic consequences such as cancer. The utmost care and consideration must be taken in order to ensure astronauts are as safe as possible when journeying beyond the relative safety of Earth’s hospitable magnetic field.