With the recent 150m hop of Starship prototype SN5, Elon’s ambition (and our desire!) of colonizing Mars in the 2030s looks very real. If the development and testing were to continue at this pace, Starship should be ready for its maiden voyage before 2025. We’d be ready with the capability to launch humans, no doubt, but would we ready with the human systems?
A round trip to Mars would roughly take about 21 months: about 18 months in deep space and 3 on Mars. Starship would probably be able to take us to Mars a little faster, possibly, in 6 months. But even that span could cause serious damage to the health of an astronaut if not protected from.
So, what is this radiation that we’re talking about? We’re talking about ionizing or high-energy radiation. It includes X-rays, gamma rays, high energy protons, and cosmic radiation which on interaction with a surface would produce secondary radiation(alpha and beta particles) by knocking off electrons!
These could be very hazardous especially since the amount of cosmic rays entering our solar system has increased due to the period of shrinking heliosphere, the bubble around our solar system created by solar wind pressure. (more on that in a later article). Oh, and did I give an honorable mention to the good ol’ Coronal Mass Ejections (or CME’s) by our dear Sun? If one is to occur during a deep space mission, the hazards for astronauts would increase by a good factor. Though the Orion capsule would be equipped with the HERA sensor, or Hybrid Electronic Radiation Assessor, to provide a warning if crew members need to take shelter in the middle of the crew module with storage bags as a cover in the case of a radiation event, such as a solar flare. The fear of an instrument failure and/or a partial mission failure remains.
For a fact, a solar storm event occurred between Apollo 16 and 17 missions. Had it occurred during one of those, history would have been a little different.
Why worry about radiation though? Did we not go to the Moon with minimal protection? Well, yes we did, but the duration of the Apollo missions was roughly 8 days. On Earth, due to its magnetosphere, on average humans experience about 2.4 millisieverts a year(varies based on location). The problems due to radiation are assumed to start at about 2.5 rads or 500 milli SV. But that isn’t accurate enough since radiation measurement accounts for a lot of factors. The radiation the Apollo astronauts experienced averaged at about 1.14 rads or about 10millisieverts. To put this into perspective, an abdominal CT scan exposes you to about 7mSV. Eating a banana exposes you to about 0.1 microsieverts of radiation from radioactive potassium in it. In an airplane at 30,000 feet, the level of radiation is up to 3 microsieverts. Astronauts aboard the ISS receive about 80 millisieverts(or 80,000 micro SV).
The minimal protection on Apollo spacecrafts did come with a cost. Due to radiation, Apollo astronauts experienced bright flashes in their eyes due to cosmic rays hitting at the back of the retina creating Cherenkov radiation( a type of radiation caused due to charged particles moving faster than the speed of light in a particular medium) which could have played a part imparting 39 Apollo-era astronauts some form of cataract. Out of these 36 flew on high radiation moon landing missions.
According to a study in 2016 by Michael D. Delp and collaborators, the Cardiovascular Disease(CVD) mortality rate among Apollo lunar astronauts is 4-5 times higher than LEO astronauts. The number of deaths due to CVD was almost 5 times higher in Apollo astronauts. Note that several Apollo astronauts also had flown on Skylab, Gemini or Mercury missions.
Radiation, specifically high atomic number 56Fe, can also alter cellular physiology through DNA (deoxyribonucleic acid) mutations. Astronauts may experience increased thirst for water which would deplete this precious resource at a faster rate.
There are some positive effects of radiation(weird, right? oxymoron! hah) which include a little better adaptation of the immune system and increased telomers’ length, which is related to cell-repair and aging. The longer, the better!
The best way to protect the craft would be to build an artificial magnetic field around the craft, followed by some passive protection though layers of aluminium or metal hydrides.
Astronauts would also have to carry exercise machines since the zero-g environment would reduce their bone density. ISS has 3(a bicycle, a treadmill, and a weightlifting machine of them on which astronauts workout for at least 6 hours a day. Their vision would also decline but that isn’t a huge problem as it could be corrected by power glasses.
NASA revealed it’s newest space-suits for Artemis generation in 2019, so that’s a plus.
The Exploration Extra Vehicular Mobility unit: