The Martian atmosphere is around 100 times thinner than Earth’s and therefore not able to produce enough drag to decelerate a manned spacecraft laden with cargo.
NASA’s Curiosity Rover is the largest platform to have touched down on the Red Planet, but at 2,000lb (907kg) it was close to the weight limit for existing deceleration technology. Delivering humans and their cargo to Mars will require much bigger payloads than Curiosity’s, which landed on Mars in 2012.
“To take humans to Mars, we have to deliver a small house,” said Neil Cheatwood, senior engineer for planetary entry, descent and landing at NASA’s Langley Research Center. “You need an aeroshell much larger than you can fit inside a rocket.”
To deliver that payload, engineers are working on a decelerator that can withstand the heat and speed of approaching the Red Planet. To this end, NASA’s Space Technology Mission Directorate and United Launch Alliance are working on LOFTID (Low-Earth Orbit Flight Test of an Inflatable Decelerator), which is part of the HIAD (Hypersonic Inflatable Aerodynamic Decelerator) programme.
LOFTID is set to fly on the same Atlas V rocket as the JPSS-2 polar-orbiting satellite in March 2022. According to NASA, the flight will not carry a payload, but will test the vehicle’s ability to survive re-entry to Earth from space, produce the desired atmospheric drag and, Cheatwood said, “exhibit adequate aerodynamic stability to keep us pointed forward and not just come in tumbling.”
LOFTID’s inflatable structure is made of synthetic fibres, braided into tubes that NASA said are 15 times stronger than steel. The tubes are coiled so that when they’re inflated, they form the shape of a blunt cone. The thermal protection system that covers the inflatable structure (and described in the video) is designed to survive entry temperatures and able to withstand 2,900oF (1593oC). The aeroshell built for the flight demonstration will reach 20 feet in diameter when deployed, nearly five times its size when stowed. Engineers believe it can be scaled up to accommodate large payloads.
After the JPSS-2 satellite is delivered to its orbit, the Centaur, the rocket’s second stage, will deorbit to a lower orbit. The Centaur will point the LOFTID vehicle toward its desired atmospheric entry point and allow the aeroshell to inflate. The Centaur then will spin the vehicle up to give it gyroscopic stability, eject it, and then perform a divert manoeuvre. As LOFTID re-enters the Earth's atmosphere, it will slow from hypersonic to subsonic speeds, deploy a parachute and then land. It is expected to reach speeds as fast as five miles per second.
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