How NASA Will Protect Astronauts From Space Radiation
Narration: Joy Ng
[00:00:00:000] It’s August 1972 and Ian Richardson
[00:00:04:180] — a future NASA scientist -- is watching TV when the BBC announces:
[00:00:08:250] “The interference is caused by solar activity.”
[00:00:12:150] He didn’t know then, but the Sun had just erupted
[00:00:15:180] in one of the most powerful solar events ever recorded.
[00:00:18:230] There was no threat to humans because Earth’s magnetic field
[00:00:22:050] deflects much of the Sun’s radiation.
[00:00:24:050] But the explosions were so powerful that intense radiation
[00:00:28:020] disrupted TV signals and caused radio blackouts.
[00:00:31:190] So what if you were outside Earth’s magnetic field?
[00:00:35:020] On the Moon and beyond, astronauts face the risk of extreme radiation exposure.
[00:00:40:150] Luckily, the intense radiation in 1972 occurred right between
[00:00:44:170] Apollo 16 and 17 missions when no astronauts were in their path.
[00:00:49:100] As NASA plans missions to go back to the Moon and then on to Mars,
[00:00:53:030] predicting the Sun’s activity to protect astronauts from space radiation
[00:00:56:270] is one of our biggest priorities.
[00:00:59:200] One of the biggest unknown factors about going to space
[00:01:02:140] is the radiation hazard from the Sun.
[00:01:04:040] This is Ian today — studying the effects of the Sun, also known as the field of heliophysics.
[00:01:10:030] The Sun is always emitting radiation like the light we see.
[00:01:13:130] But solar energetic particles, like from the August 1972 events, can be far more harmful.
[00:01:19:180] To be able to forecast solar energetic particles, we need to know how the Sun energizes them.
[00:01:25:090] The Sun is made up of electrically charged particles called plasma.
[00:01:28:120] As this plasma moves, it builds up energy inside its massive magnetic field.
[00:01:33:270] This energy is usually released in two types of explosions.
[00:01:37:240] Flares are intense flashes of light.
[00:01:40:140] Coronal mass ejections are giant eruptions of solar material.
[00:01:44:020] These solar eruptions send shock waves across the solar system accelerating particles as they go.
[00:01:49:250] These are solar energetic particles, or SEPs.
[00:01:53:240] They consist mainly of protons and possess a lot of energy
[00:01:57:040] that can affect satellite measurements
[00:01:59:210] and humans.
[00:02:00:260] SEPs can bombard you with a lot of radiation in a short period of time.
[00:02:04:140] They can penetrate your skin, damage your DNA, and increase your chances of getting cancer and radiation sickness.
[00:02:11:050] But they don’t occur with every solar eruption.
[00:02:14:140] Only a small number of flares and coronal mass ejections create SEPs.
[00:02:19:090] So we’re trying to predict when SEPs form and how they travel through space.
[00:02:23:120] At NASA’s Goddard Space Flight Center,
[00:02:26:020] the Community Coordinated Modeling Center, or CCMC, is dedicated to testing prediction models.
[00:02:32:150] Working with global partners, they use data from NASA satellites at different vantage points
[00:02:38:020] and models to figure out how solar explosions behave
[00:02:41:080] including how shock waves energize SEPs.
[00:02:44:160] And as we get better at predicting, we get more time to prepare.
[00:02:49:030] Preparation for an SEP event -- of which you may know that is already coming
[00:02:53:190] and perhaps the magnitude as well --
[00:02:55:150] the technique that you would want is to use
[00:02:58:150] is to put as much mass between you and the source.
[00:03:01:290] On the surface of the Moon or Mars, astronauts can go underground or build shelter with local materials.
[00:03:08:070] But in transit, astronauts can only be protected with what’s on the spacecraft.
[00:03:13:190] which means that you might have elements on a spacecraft that have multiple purposes.
[00:03:18:240] NASA’s space radiation specialists are testing different ways to do this.
[00:03:23:030] One strategy they tested on the Orion spacecraft involves crew members
[00:03:27:140] barricading themselves with as much mass as possible in the center of the spacecraft.
[00:03:31:220] Other possible techniques in development include vests that add mass
[00:03:36:100] and electrically-charged surfaces that deflect particles.
[00:03:40:190] In terms of radiation protection and radiation mitigation, the factor of time is extraordinarily important.
[00:03:48:060] The Sun has a natural 11-year cycle that transitions through low and high activity,
[00:03:53:060] which is indicated by the number of sunspots on the surface.
[00:03:56:240] More sunspots mean more eruptions resulting in a higher risk for SEPs.
[00:04:03:160] But during this increased solar activity,
[00:04:06:140] the Sun’s magnetic field strengthens,
[00:04:08:160] enhancing its shield against another important source of radiation --
[00:04:12:060] galactic cosmic rays.
[00:04:15:010] These are charged particles traveling at nearly the speed of light
[00:04:18:170] that are thought to come from supernova explosions from within our galaxy
[00:04:22:020] and possibly further out in the universe.
[00:04:24:250] If solar energetic particles are intense, sporadic storms, then galactic cosmic rays are a constant drizzle.
[00:04:31:150] Galactic cosmic rays are more sparse, but also much more energetic.
[00:04:36:030] They include heavier elements that can penetrate through vast amounts of materials.
[00:04:40:260] Understanding the rate of galactic cosmic rays
[00:04:44:120] helps us determine how much time astronauts can spend in space safely.
[00:04:48:230] To date, humans have only been on the lunar surface for a cumulative total of about 12 days.
[00:04:54:050] A trip to Mars will take 6-10 months each way.
[00:04:57:180] That means even more radiation exposure, and so NASA is doing the work to prepare for that.
[00:05:03:080] The Moon is going to be a testbed for us in order to be to prepare for Mars.
[00:05:07:140] The more that we understand the impact and the duration of radiation on the Moon,
[00:05:13:070] the more we can extrapolate that to the length of time that we will be spending in transit and on the surface of Mars.