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Published: 2015-06-02 09:04:45
Updated: 2015-06-02 09:04:45
Posted June 2, 2015
By Tony Rice
NASA will test the Low Density Supersonic Decelerator (LDSD) at the Navy’s Pacific Missile Range Facility in Hawaii early Wednesday. LDSD will do just what its name implies, decelerate from supersonic speeds but do so with a low density design.
LDSD borrows that design from the Hawaiian puffer fish to increase size, or more specifically, surface area. That surface area is needed to slow a space craft entering a planet’s atmosphere, or other planetary bodies with atmospheres, including Earth.
I last saw LDSD late last year inside the massive cleanroom of the Spacecraft Assembly Center at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif. A pair of test vehicles neared completion. JPL has a keen interest in the project; it will enable future exploration missions to Mars, even beyond the upcoming 2020 rover.
When the Curiosity rover arrived at Mars in 2012, it used the thin Martian atmosphere to slow from 13,200 mph to about 180 mph before the skycrane, a bit like a rocket-powered backpack for the rover, brought the craft to a soft landing. Most of that 13,000 mph difference was achieved with the atmospheric drag of a heat shield, largely designed by engineers at NASA’s Langley Research Center in Hampton, Virginia. Similar technology enabled a pair of Viking landers to land safely on Mars in the 70’s.
However, to bring heavier payloads and eventually people to the surface of Mars, new technology is needed to use the atmosphere to bring spacecraft below speed of sound. This is especially true in low density atmospheres like Mars.
Following up on previous tests using rocket sleds and wind tunnels, this week’s test will lift the LDSD vehicle to an altitude of 120,000 feet off the coast of Kauai. Four small rockets will then spin the vehicle, stabilizing it. A larger solid rocket motor will fire, launching the vehicle into the stratosphere, where it will reach a height of 180,000 feet and speeds of Mach 4. Atmospheric density at that altitude is very similar to Mars. Aerodynamic decelerators will then inflate around the vehicle, slowing it to Mach 2 or lower. A supersonic parachutes will take over and the LDSD test vehicle and it’s balloon will be recovered in the ocean by a U.S. Navy team.
NASA announced late Monday evening that a launch attempt planned for Tuesday was postponed due to unfavorable ocean conditions. The next window opens Wednesday at 1:30 p.m. EDT (7:30 a.m. Hawaii time). NASA TV will provide coverage including live streaming video from the vehicle.
Tony Rice is a volunteer in the NASA/JPL Solar System Ambassador program and software engineer at Cisco Systems. You can follow him on twitter @rtphokie.