After weeks of canceled launches, today NASA finally completed its first successful test of the Low-Density Supersonic Decelerator (LDSD)—a flying saucer-shaped device that could one day help humans safely land on another planet.
When a capsule or shuttle full of human re-enters the Earth’s atmosphere, it can use the atmosphere to help it slow down. Air molecules can’t get out of the way fast enough, and so they bunch up to provide a sort of cushion for the speeding humans. (This compression is what causes objects to burn up in our atmosphere, not friction.) But on Mars for example, the atmosphere is much, much thinner, and therefore any mission involving humans or large equipment wouldn’t be able to use the atmosphere in the same way.
To help solve this problem, NASA has been testing both supersonic parachutes and doughnut-shaped innertubes. How parachutes slow down an object is pretty straight forward, but how does the relatively small inner tube (the Supersonic Inflatable Aerodynamic Decelerator or SIAD) on the LDSD? Put simply, it increases the drag on the test saucer. Think of it this way: Have you ever looked at the wings of a plane right after it landed? Remember those little flaps that rose up? Those braking flaps increased the drag on the aircraft as a whole, and helped to slow everything down. The inflatable inner tube of the LDSD works the same way. (You can’t use metal flaps like we do for planes because they would break off at supersonic speeds.)
Initially delayed from its first planned launch weeks ago, NASA finally completed a test of the LDSD earlier today. During the test that streamed below, the whole apparatus—test vehicle equipped with inner tube and parachutes—was carried up to 120,000 feet by a balloon, then up to 180,000 feet by rocket. A powered flight put the vehicle on a ballistic trajectory, reaching supersonic speeds of Mach 3.8 before the SIAD was deployed to air brake with the extra drag. At around Mach 2.5, massive parachutes (the final one didn’t deploy fully, but it didn’t affect things too much) then landed the test vehicle “gently” in the oceans off Hawaii.
Currently, we don’t have the technology to land anything larger than something like the 1-ton Curiosity rover on another planet. The weight limit is a huge barrier to becoming more active in space. And because NASA estimates that we couldn’t land humans on the surface of Mars without 40 tons of cargo, for example, testing technology like the LDSD is crucial for a continued human presence beyond Earth. Without a better way to slow down, there’s no way the first humans could land carefully in the Martian dust.
Much more info on NASA’a LDSD project here.
Oh, and how do you test a supersonic parachute? Test it with rocket sleds and Metallica!