A SpaceCraft Could Get to 430,000 Miles From the Sun Using Proposed Coating

In 2018 the Parker Solar Probe launched and plans to approach the Sun to within 8.5 solar radii (4 million miles) of its surface. This is seven times closer than any previous mission.

Researchers think a new coating could allow spacecraft to get close as one solar radii (430,000 miles) from the Sun’s surface. This would be eight times improvement over the Parker Solar Probe.

The goal of a Phase 1 NIAC study is to determine how near a spacecraft might come the Sun using a novel, very high-reflectivity coating. Using this material to cover a thin solar shield and including a secondary silvered reflective cone between the shield and the spacecraft (to reflect away infrared radiation from the shield).

The Parker Solar Probe utilizes a solar shield comprising a lightly-coated carbon composite layer on top of four inches of carbon foam. However, the temperature limits of the shield restrict the closest approach distance.

urrently have co-funding to demonstrate that our new coating can allow a coated tank to reach cryogenic temperatures at earth distance from the Sun. This funds allow for continued coating development for our proposed Phase 2 NIAC to consider only coating issues relevant to being near the Sun. Specifically the optical and mechanical issues related to high temperature long-wave reflectors will be an area of study in our Phase 2 effort.

In Phase 2, we would compare these two materials, both theoretically and experimentally, to determine which is preferable for close Sun approach. We have models developed under our prior, cryogenic selective surface NIACs to use as a theoretical baseline. Experimentally, we considered using a high intensity solar simulator to test samples, but have discovered that the infrared emission from these simulators is much higher than that of the sun. So instead, we propose to use the sun itself as a high irradiance source (taking into account the filtering of the Earth’s atmosphere). A tracking reflective telescope would focus sunlight, collected over a large area, onto a small sample of material. Measuring the resulting temperature would provide insight into the performance of these materials.

Another Phase 2 task would add fidelity to the conceptual spacecraft design, with the input of a thermal analyst from Glenn Research Center and a structural engineer from Kennedy Space Center. Optimization and comparison of design solutions will proceed in a cooperative fashion. The design of components such as support struts must consider radiative issues to allow heat emission, yet operate under a very large thermal gradient. In addition, the secondary shield, which reflects long wave infrared away from the payload, has both optical and mechanical issues in its design that must be jointly addressed.

JPL has stated that future interstellar missions may require a slingshot maneuver around the Sun. Analysis shows that this future vehicle would need to approach the Sun to within 3 solar radii, and JPL believes that using our new coating may be the only feasible method to achieve this.

Approaching a star to within 5 solar radii (2.2 million miles) would enable a laser-pushed solar sail that reached 4.6% of the speed of light to decelerate at a target star.

There have been various papers that looked at close fly-bys of the sun for gravity slingshots to gain speed.

The gravity slingshot around the sun to one solar radii could give speed of about 200 km/second but deploying a solar sail immediately as the sun is being passed would provide a lot more speed.

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