First material tests in
IRS Plasma Wind Tunnel


February 2022

Successful heat shield test

When you return from space, you are flying very fast, so you need to use the atmosphere for braking. However, at these speeds, air becomes very hot, forming a bow shock wave and partly turning into plasma.

In order to keep your return vehicle at safe temperatures, you need a heat shield. The classic approach – for example with the Apollo moon capsule, the Soyuz capsule or the SpaceX Dragon capsule – is to have a heat shield for the initial atmospheric re-entry, followed by small drogue chutes and finally larger parachutes for landing.

This approach is complex, expensive, and not sustainable: The so-called “ablative” heat shields are single-use items because they “burn away” in a controlled manner to keep the rest of the vehicle cool.

The Space Shuttle used a better, more advanced approach: It had a very large, blunt belly heat shield. Such a large heat shield reduces the ballistic coefficient, meaning that you have less mass to brake per area of heat shield. This reduced the peak heat flux into the heat shield and enabled the Space Shuttle to have a reusable ceramic heat shield.

With our Inflatable Atmospheric Decelerators (IADs), we want to take that approach to the next level: We reduce the ballistic coefficient even further by having more heat shield area and less mass to brake, which enables us to build a foldable heat shield: For launch, it is stowed; for reentry, it is inflated.

So, what do you need to make this happen? You need a foldable ceramic fabric that can withstand temperatures of more than 1000 °C, while being mechanically strong enough to brake the return vehicle. You also need a lot of gas to inflate the IAD. Instead of taking heavy gas tanks up to space, we intend to save mass by taking that gas from the atmosphere. This innovative, patent-pending approach has never been demonstrated – until now.

On February 8th 2022. ATMOS Space Cargo finished a plasma wind tunnel testing campaign at the Institute for Space Systems (IRS) in Stuttgart. We exposed our heat shield materials to the same conditions they would undergo in a return from space. We tested aluminosilicate ceramic fabric under tensile loads to destruction to figure out the material’s limits. We also demonstrated, for the first time ever, the plausibility of taking air from the hot boundary layer behind the bow shock wave for the inflation of an IAD. The air inlet and flap, made from ceramic matrix composites, endured glowing hot temperatures in remarkable conditions and proved their reusability.

We would like to thank our strong partners for their support in this campaign: Prof. Fasoulas, Dr. Herdrich and Dipl. Ing. Pagan and their team at the Institute for Space Systems, Dipl. lng. Walter Pritzkow, who manufactured the fiber-reinforced ceramic inlets, and all the others who helped make this happen.

As part of our current feasibility study, these tests are another critical step forward in making space transportation sustainable, scalable and eco-friendly. By returning rocket first and upper stages, space manufacturing payloads, experiments, and a plethora of other cargo varieties – we anticipate the optimistic future of a space industry with zero environmental impact.

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