Testing the first electrostatic radiation shield in deep space

Can we have Star Trek-style radiation shields on future space missions?

TeamIndus is soft-landing on the Moon in 2018, carrying with it six student-built experiments under the umbrella of Lab2Moon. One of them is the EARS (Electrostatic Active Radiation Shield) experiment, aiming to change the future of radiation shields for spacecrafts and future space colonies. Seeing the potential of such an experiment, the Shiv Nadar Foundation decided to fund the aspirational idea proposed and led by Saumil, Aniket and Aishwarya.

Earth-inspired solution to a space problem

Traditionally, protection from space radiation for astronauts and electronics of spacecrafts has been material-based (usually lead) a.k.a. passive shielding. Team EARS wants to use something that isn’t material-based, drawing inspiration from the natural shielding that our Earth has had for billions of years.

An artist’s depiction of the Earth’s magnetic field protecting itself from solar charged particles. White lines — solar radiation, purple line — bow shock, blue lines — Earth’s magnetic field. Image not to scale. Source: Wikipedia

The magnetic field generated by the core of the Earth actively protects us from incoming charged particles. What if we could employ just one such active shield for every spacecraft? That is the thought that led Team EARS to experiment with a Van de Graaff generator to create a high electric potential difference that can deflect charged particles. A Van de Graaff generator uses the same principle which attracts paper pieces to a comb rubbed against your hair — static electricity.

Styrofoam peanuts clinging to a cat’s fur due to static electricity. Source: Wikipedia

The setup

The soda-can sized EARS experiment consists of a Van de Graaff generator capable of generating a 450 kV voltage. Here is what the setup looks like:

A miniature Van de Graaff generator storing positive charge on the sphere-shaped conductor at the top. Electric motor (bottom right) and gears run the rubber belt.

The charges accumulated on the sphere-shaped conductor at the top produces a strong electrostatic field around it. A transparent insulating polycarbonate material around the generator and at the top complete the structure. Two radiation sensors are placed at the top deck to monitor incoming charged particles.

The two sensors on the top deck to monitor incoming charged particles.

How it works

When the conducting sphere is fully charged, the electrostatic field created will engulf the sensors. The positively-charged sphere will attract negative particles (like electrons) in space radiation and the sensors will detect them. Positively-charged particles (like protons) will get deflected due to electrostatic repulsion.

A charged particle is deflected by an electrostatic field. Source: Quora

Prior to turning on the Van de Graaff generator, both the positive and negative charges will be picked up by the sensors. When the generator is on and fully charged, only negative charges will be detected, thereby decreasing the radiation count. The working of the shield will be tested for varying levels of electrostatic potential to understand its effectiveness.

The entire EARS experiment is powered by electricity and a microcontroller interfaces with the computer onboard the spacecraft. The Van de Graaff generator will be turned on after the 14th (Earth) day of lunar landing to avoid any possible damage to the other instruments onboard the TeamIndus lander. The EARS sensors though will begin taking charged radiation counts well before that day. This allows to get radiation data starting from when the spacecraft is in Low Earth Orbit (LEO) to when the spacecraft is on the lunar surface.

The data will tell us about the nature of radiation on the lunar surface and how efficient the electrostatic shielding is. If successful, this will be the first time active radiation shielding has been demonstrated in deep space.

The bionic Soviet mission Kosmos 605, launched in 1973, demonstrated a working electrostatic radiation shielding in LEO. Team EARS wants to test the feasibility of this concept on the Moon onboard the TeamIndus spacecraft, gearing for launch in 2018.

A Bion satellite, part of the Soviet space program focused primarily on biological experiments. Source: Wikipedia

Advantages of an active radiation shield

There are numerous advantages of an active shield over a static one.

  1. Active shielding is cheaper than material-based shielding for the same amount of efficiency due to reduced material cost.
  2. The ability of a material-based shield to protect from radiation deteriorates with time. For long space missions, a self-sustainable active shield is thus more effective and reliable.
  3. An active shield reduces launch cost as the significant mass of a passive shield is reduced.

One disadvantage of an electrostatic shield is that it can’t block X-rays or gamma rays as the shield is charge-based. There is another Lab2Moon experiment onboard the lander which is innovating on that front. The team Space4Life aims to replace the lead shield with a cyanobacterial one, while handling intense gamma-rays too.

Applications

The potential applications of an active radiation shield are numerous. The habitable modules of future lunar colonies can be protected using such a shield. Even manned rovers being driven on the lunar surface could make use of it. The EARS experiment, while small, will lay the groundwork to determine the full-scale requirement of employing a radiation shield capable of protecting future lunar colonies.

Concept of an electrostatic shield for a lunar base using charged spheres. Source: SlideShare

The next steps

Simulations of the EARS experiment using Strontium-90 as radiation source has yielded positive results (pun intended). The next step is to test the experiment on the particle accelerator “Microtron” available at the University of Pune. The conditions in the vacuum of the accelerator closely mimic the lunar environment. After that, Team EARS will be ready to fly to the Moon in 2018 and take their moonshot.

Conclusion

Van de Graaff generators saw their first application as particle accelerators. From being the first particle accelerators to potentially accelerating the future of space exploration and settlement, the Van de Graaff generator has been one neat invention. Who wouldn’t like to have Star Trek-style radiation shields? I know I would.

Illustration of an electrostatic field surrounding the Star Trek spaceship U.S.S Enterprise. Source: HowStuffWorks

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