NASA Flew a Radiation Vest Around the Moon. It Could Cut Solar Storm Doses by 60%

In November 2022, two unusual passengers flew around the Moon. Their names were Helga and Zohar.

They had no arms and no legs. They were dummies made of tissue-like resin, packed with radiation sensors.

And one of them, Zohar, was wearing a very special vest.

Now we know how that vest performed. According to a new study in Science Advances, it could cut an astronaut's radiation dose from a major solar storm by up to about 60%.

That could make the difference between a Moon or Mars mission that's dangerous and one that's manageable.

The problem: space is a radiation bath

Here on Earth, our atmosphere and magnetic field shield us from most space radiation. Astronauts on the International Space Station still get some of that protection.

But once you head to the Moon or Mars, it's gone.

There are two main dangers. One is a steady drizzle of cosmic rays from deep space, which raises cancer risk over a career.

The other is sudden and violent: solar particle events, or solar storms.

Why solar storms are so scary

During a solar storm, the Sun hurls out a burst of high-energy protons. The number of these particles can rise by 10,000 to 100,000 times, over hours or days.

And they can't be predicted more than a few hours in advance.

The good news is that storm protons are easier to block than cosmic rays. With enough shielding, you can stop much of the dose.

The bad news is that shielding is heavy. Coating an entire spacecraft in thick protection is impractical, because every kilogram launched costs a fortune.

The idea: protect the organs that matter most

The AstroRad vest takes a different approach. Instead of shielding the whole ship, it shields the parts of your body most sensitive to radiation.

That includes bone marrow, lungs, stomach, colon, breasts and ovaries.

The vest is made of a plastic called high-density polyethylene. It's rich in hydrogen, which makes it one of the best materials for stopping space radiation per kilogram.

Because the plastic is stiff, it's built from thousands of small hexagonal pieces. They move like scales, so you can still bend and twist.

It's also thicker where your body offers less natural protection, and thinner where it offers more. The flight version weighed about 26 kg.

The vest was developed by StemRad, an Israeli company, with support from NASA, Lockheed Martin and the Israel Space Agency.

The experiment: two dummies around the Moon

Meet Helga and Zohar

Artemis I was NASA's uncrewed test flight around the Moon, from November 16 to December 11, 2022.

Instead of astronauts, two female-shaped "phantoms" sat in the crew seats. These are models made of materials that absorb radiation like human tissue.

The researchers chose female models because women face a higher estimated cancer risk from radiation under current risk models.

Zohar wore the vest. Helga didn't, and served as the comparison.

Both carried detectors inside and on their bodies, measuring radiation throughout the flight.

The twist: no solar storm happened

There was one snag. No major solar storm struck during the mission.

So the team used the next best thing. On the way out, Orion passed through the inner Van Allen belt, a zone of trapped protons around Earth.

Those protons behave much like a solar storm, though with more penetrating energy. The vest cut the modelled dose there by about 26%.

The researchers used these real measurements to check a detailed computer model of the dummies and the spacecraft. The model matched the detectors closely.

Then they fed that model the radiation from two famous historical solar storms, from August 1972 and October 1989.

The results: a big drop in dose

Here's what the simulations predicted for an astronaut model inside Orion's crew cabin.

These figures come from a whole-body model. A torso-only model gave slightly bigger reductions: about 61% and 39%.

For comparison, mSv (millisieverts) is the standard unit of radiation dose. A typical chest CT scan is about 6 mSv.

Why those numbers matter

NASA's mission-planning rule says an astronaut shouldn't get more than 250 mSv from a single solar storm like the 1989 event.

Without a vest, the model put astronauts at 204 to 219 mSv. That's uncomfortably close.

NASA also caps an astronaut's total career dose at 600 mSv. Without a vest, one big storm would use up about a third of that.

With the vest, that dropped to between 14% and 23% of the career limit.

More time in space

The researchers turned this into something astronauts care about: how long they could keep flying.

Depending on the storm and the Sun's cycle, the vest would preserve between 40 and 193 extra days of permissible time in deep space.

For astronauts who take years and huge sums to train, that's a lot of extra career.

A vest beats a suit

The team also tested a thought experiment. What if you spread the same 26 kg evenly over the whole body, as a full suit?

The vest did better. Its targeted design improved the overall dose reduction by about 30% compared with the uniform suit.

A full suit would also be harder to put on and move in.

What earlier research found

This study builds on earlier work measuring radiation beyond Earth, and on other ways to protect crews.

Orion is already well shielded

A 2024 study in Nature reported the main radiation measurements from Artemis I.

Dose rates varied fourfold between different spots inside Orion during the proton-belt passes. Where you sit really matters.

Cosmic-ray doses inside Orion were up to 60% lower than earlier measurements from a lightly shielded Mars probe. And simply turning the spacecraft cut dose rates in the belt by around 50%.

Models can predict it

A 2025 study in npj Microgravity compared radiation models with real measurements from Earth orbit to Mars during Artemis I.

The models were run blind, without seeing the measurements first. They accurately predicted the doses in very different shielding setups.

That matters here, because the vest's storm results depend on simulations.

The storm shelter alternative

NASA's current plan for a solar storm is a shelter. The crew pile cargo and supplies around themselves in the most shielded part of Orion.

According to the new paper, an internal NASA analysis found this cargo-bay shelter cut the dose from a 1989-like storm by 36%. That's close to the vest.

But it leaves the crew cramped and unable to work. A newer "whole cabin" design lets them move around, but is almost half as effective.

Astronauts have tried it on

The vest's comfort was tested earlier on the International Space Station, in an experiment that ran from 2019 to 2022. Astronauts wore it in microgravity to judge how it felt.

How it fits together

Put together, earlier research shows Orion is a well-protected ship, and that its radiation can be modelled reliably.

The vest adds something the shelter can't: protection while astronauts keep moving and working.

How much should you trust this?

Early. The flight data are real, but the solar-storm results are predictions.

What makes it convincing

• It's the first test of wearable radiation shielding in deep space.
• The computer model was checked against real measurements from dozens of detectors, and matched well.
• It was a large international collaboration with NASA, the German Aerospace Center and the Israel Space Agency.
• It's published in Science Advances, a peer-reviewed journal.

What makes me cautious

• No solar storm happened, so the headline numbers are simulations, not measurements.
• The "astronauts" were dummies, not people. We don't know how real people would wear it for hours.
• Helga and Zohar sat in slightly different seats, with slightly different shielding.
• Four authors work for StemRad, the company that makes the vest. Its CEO co-founded the firm, holds equity and is named on patents covering the vest.
• Only two historical storms were modelled. A bigger or differently shaped storm could behave differently.

What this means for you

Unless you're booked on a Moon flight, this won't change your day. But it does change what future space missions might look like.

• Moon and Mars trips are getting closer. Artemis II flew astronauts around the Moon in 2026, and landings are planned.
• Radiation is one of the biggest barriers. Solutions like this vest could decide how long crews can safely stay.
• Smart design beats brute force. Protecting the most sensitive organs gave more benefit than covering everything equally.

If you're curious about radiation on Earth, the World Health Organization explains radiation and its health effects in plain language.

This Nature video introduces Helga and Zohar and why their flight matters:

What we still don't know

1. How does it perform in a real solar storm? That needs a storm during a mission, with the vest on board.
2. Can astronauts work in it for hours? Wearing 26 kg during an emergency is a real challenge, even in low gravity.
3. Would the vest plus a shelter be best? The authors suggest astronauts could wear it when leaving the shelter for vital tasks.
4. Does it help against cosmic rays? It's designed for solar storms, not the steady background radiation.
5. Will independent teams confirm the results? Replication by researchers without ties to the maker would add confidence.
6. Will NASA adopt it? That depends on mass, cost and mission needs.

My take: clever protection, still on paper

What I like about this study is its elegance. Instead of armouring the whole spaceship, it protects the organs that matter most.

And the idea of two dummies flying around the Moon for science is wonderful.

I'm less convinced by how far the numbers can be pushed. They're simulations, and the vest's maker is closely involved.

Still, the model was carefully checked against real data. As humans head back to the Moon, a vest that lets astronauts keep working through a solar storm looks like a very good idea.