| Materials

Adam Sidor, NASA Research Fellow, Georgia Institute of Technology, Atlanta, GA

Thermal Protection Systems (TPS) — heatshields — form the outer surface of spacecraft and provide protection as the vehicle plunges through planetary atmospheres. Conformal ablative materials are currently being developed to improve TPS performance. Adam Sidor is developing a fresh approach to designing and manufacturing these materials to produce larger tile sizes while reducing labor, cost, and waste.

Tech Briefs: What was the problem you set out to solve?

Adam Sidor: The problem was how to improve on the current state-of-the-art of heat shield manufacturing. I was able to observe the processing of conformal TPS material a couple of years ago, and saw that there was some waste and inefficiency in the process. It works fine for what it is right now, but unused resin is just discarded at the end of the process.

Tech Briefs: What are the advantages of conformal vs. traditional heat shields?

Sidor: A traditional Phenolic Impregnated Carbon Ablator (PICA) starts with a rigid fiber substrate that is impregnated with a resin to create a solid block. The material is then machined to form a curved tile — a cumbersome process. Since the tiles are so brittle, you have to limit their size because they’re prone to cracking and breaking. In contrast, conformal ablators are flexible and have some pretty nice properties such as higher strain to failure and consistent properties across the entire tile. They also have the manufacturing benefit that you can mold them to conform to the curve of the spacecraft.

Tech Briefs: What was your solution for improving the process?

Sidor: The current conformal process is to just immerse the substrate in the resin. You end up curing excess resin in addition to the actual part. The excess then has to be discarded. I did a lot of digging to see what existed in the composites industry. I was looking for a process that would be applicable to conformal TPS, eliminate the wasted resin, and produce a more uniform tile. I came up with the idea of using Vacuum Infusion Processing (VIP) in which the resin is injected directly into the substrate within a sealed mold so there is little to no waste. The VIP process I’m working on is a subset of a larger category of processes called nickel deposit molding. In that process, you have a sealed mold in which you can introduce resin through a port to infuse the substrate material under vacuum. I knew that was a good candidate because they were injecting the resin directly into the part.

Tech Briefs: Are conformal ablators now the rule for new heatshields?

Sidor: Not yet, but they’re certainly up and coming — they’re still in the development stage and have to be scaled up. I anticipate that the advantages will lead to their adoption in the near future. I hope my work will lead to scaling up the process so the tiles can be large enough to use for an actual heat shield.

Tech Briefs: What are your current goals for the process?

Sidor: I’m taking a two-pronged approach. First, I want to develop the VIP process itself, which involves scaling it up. So far, I’ve worked on small samples. In the next few months, I want to optimize the process at small-scale. Then beyond that, my goal is to scale it up to large-size tiles to discover what sort of challenges you run into when you do that.

To learn more, read a full transcript, or listen to a downloadable podcast, visit www.techbriefs.com/podcast.