The Axiom-1 mission carried out the -Fluidic Telescope Experiment (FLUTE) - that could revolutionize astronomy. FLUTE[1] looks to study the unique characteristics of microgravity to create a lens from liquid polymers.
Detecting more details and reaching further into the distant Universe require large apertures or mirrors. However, launching these into space is a challenge. Take as an example the James Webb Space Telescope (JWST). The initial proposal was for a 9-meter mirror with very sophisticated instruments that would allow us to achieve a large set of scientific goals. The design, however, changed over time due to two limitations for all space missions - weight and size. These limitations are due to the power of the available rockets and the maximum size of the rocket's fairing, which protects the telescope during launch. Although the project scientists quickly realized that a 9 meters telescope was out of the question, engineers at NASA, Northrop Grumman, and Ball Aerospace were able to design a 6.5 meters lightweight foldable telescope. The instruments on board JWST, built by different teams in Europe, the USA, and Canada, also had to change designs so the whole spacecraft could meet the weight and size requirements.
ESA/CNES/Arianespace
ESA/CNES/Arianespace
An alternative option to be able to build a space telescope larger than JWST would be to manufacture its mirror in space. That is why in 2022, the Israeli astronaut Eytan Stibbe on board the Axiom-1 mission, conducted the experiment FLUTE. This project is a collaboration between NASA[2] and the Technion – Israel Institute of Technology, looking to test the unique characteristics of microgravity to create a lens from liquid polymers[3].
Furthermore, conventional technology for making optical telescopes requires polishing solid materials such as glass or metal to create the precise curved surface or surfaces of the lenses and mirrors for the telescope; which takes considerable time and comes at a great cost.
Therefore, FLUTE is looking for a novel cost-effective technology approach to make optical telescopes by taking advantage of the way fluids naturally behave in microgravity.
All liquids have an elastic-like force that holds them together at their surface; this force is called surface tension and is what gives water droplets their shape. On Earth, when water droplets are small enough – 0.08 inches (2 millimeters) or smaller – they remain perfectly spherical due to surface tension. Larger droplets get heavier and therefore squashed by gravity. Because of the microgravity of space, these droplets of water and other fluids are free-floating, and even large amounts of liquids assume the most energy-efficient shape possible - a perfect sphere. On the other hand, liquids can cling to surfaces due to a physical property called adhesion - an intermolecular force that makes liquids, like water, to be attracted to other unlike materials, like glass[4].
Considering these properties, the FLUTE team concluded that by putting enough liquid in the interior surface of a circular ring-like frame, the adhesion will make the liquid stretch across the inside of the frame while the surface tension will make it naturally form a curved shape or spherical section. Also, by using the right volume of liquid, it is possible to make the surface of the liquid curve inward instead of bulging outward, like a drop of water. If, on top of that, the liquid is reflective, that inwardly curved surface can serve as a telescope mirror[5].
NASA
Using this technology, the Flute researchers envision building a telescope mirror of about 164 feet (50 meters) in diameter - half as long as a football field. Besides its size, there are other benefits to making a mirror of this kind. Because of its unique features, a liquid mirror would be able to self-heal within a short period of time; if damaged in space by events like micrometeorite impacts, which JWST has already experienced.
The FLUTE experiment conducted during the Axiom 1 mission is just one of several small-scale experiments to evaluate how to shape lenses from liquids and in different environments. Other experiments were done in a series of parabolic microgravity flights focused on creating liquid mirrors using ionic liquids and an alloy of gallium. Also, realized experiments in neutral buoyancy space analog conditions in a ground laboratory.
Axiom-1
The Axiom 1 mission was launched on April 8, 2022 by SpaceX. They spent 17 days in space working on 26 science payloads at the International Space Station.
References:
[1]https://www.nasa.gov/directorates/spacetech/niac/2023/fluidic_telescope_flute/
[2] https://www.nasa.gov/feature/ames/nasa-tries-new-ways-fluid-materials-to-build-giant-space-telescopes
[3] https://www.nasa.gov/ames/flute
[4] https://www.youtube.com/embed/whukr452ZvY
[5] https://arxiv.org/abs/2212.08139