Landing instruments such as the twin Mars rovers Spirit and Opportunity, and the Phoenix Mars Lander on the surface of the Red Planet is one thing, but setting down the one-tonne Curiosity (MSL) is another challenge altogether. Undoubtedly, future landings will aim at setting down even larger crafts, so the current approach on keeping them safe, which relies on massive, solid heat shields will have to go, NASA engineers believe. And experts at the Langley Research Center are already working on it.
In an average descent on Mars, featuring, say, a Spirit-sized robot, the craft plummets through the thin atmosphere at hypersonic speeds, and under scorching temperatures. Every fraction of a millimeter on the ensemble thus needs to be protected against these factors via a massive heat shield, which in itself adds a lot of weight to the entry vehicle. After the temperatures outside of the shell drop, it is jettisoned, and retroboosters / parachutes take over and begin slowing it down. But this is not really an option with probes and other spacecrafts that are heavier than 2 or 3 tonnes.
Neil Cheatwood, from the Langley Research Center, in Hampton, Virginia, believes that the answer lies within inflatable heat shields. “We're kind of at the limit for what we can do,” he says of the options engineers have in protecting heavy transports to Mars. His suggestion is that future payloads should be protected through the use of an inflatable shield made up of light-weight, high-performance, heat-resistant materials. He argues that this layout would allow for the shield to be inflated to such large dimensions, that it would also create drag and act like an atmospheric descent break for the payload.
According to Cheatwood, the first test flight of the new system will take place later this year. Though the idea has been around for a while, it's only know that the necessary materials have been developed, able to withstand the speed and temperatures of an atmospheric reentry. In the tests, a rocket will lift the system to 211 kilometers above the Earth, and then deploy it to a radius of about 3 meters. The resulting saucer is made almost entirely out of woven ceramic fibers and Kevlar fibers, Nature News reports.