NASA’s Low-Density Supersonic Decelerator (LDSD), a “flying saucer”-shaped disc with the purpose of testing inflatable drag devices and supersonic parachutes for future robotic- and human-helmed missions to Mars, made its second test flight on Monday, June 8. At 1:45 p.m. EDT that day, LDSD was launched aboard a scientific balloon from the U.S. Navy’s Pacific Missile Range Facility in Kauai, Hawaii. While the vehicle’s chute visibly tore near the conclusion of the test, NASA has stated it is pleased with the test’s initial results, and will continue study the data from this test flight to make improvements.
The vehicle was lofted to an altitude of nearly 120,000 feet; it was then separated from the balloon, and an on-board rocket motor propelled LDSD to an altitude of approximately 180,000 feet. This altitude is at the very top of what is considered Earth’s stratosphere. LDSD was traveling at a speed of approximately Mach 3 when the vehicle’s Supersonic Inflatable Aerodynamic Decelerator (SIAD, in this case, SIAD-R, which is inflated with hot gas) was deployed.
Fourteen seconds later, the vehicle’s chute – a 100-feet-wide Supersonic Ringsail design, as opposed to the previous Supersonic Disksail design used in last year’s test – deployed. This newer chute design, according to NASA, had its crown strength increased in a bid to prevent it from being shredded during high-speed, high-stress conditions. However, the chute experienced some issues similar to those observed in last year’s flight test. According to NASA, “[t]he chute began to generate large amounts of drag,” and a tear formed in its canopy. The vehicle landed hard in the Pacific.
Despite this occurrence, investigators were pleased with the preliminary results from the test. Mark Adler, LDSD’s project manager at JPL, stated in a teleconference held today, “Early indications are that we got what we came for, new and actionable data on our parachute design. At present, our data is in the form of low-resolution video and some other nuggets of data which were downlinked in real-time. But this will soon change when our test vehicle makes port, and we have the opportunity to inspect the ultra-high resolution, high-speed imagery and other comprehensive information carried in the memory cards on board our saucer.”
Ian Clark, principal investigator for LDSD at JPL, added, “Going into this year’s flight, I wanted to see that the parachute opened further than it did last year before it began to rupture. The limited data set we have at present indicates we may not only have gone well down the road to full inflation, but we may have achieved it. We also saw another successful inflation of our 20-foot SIAD and another successful deployment and inflation of our supersonic ballute [according to NASA, this is an inflatable drag device that extracts the parachute]. Both of those devices have now had two great flights, and we have matured them to the point where they can be used, with confidence, on future missions. We’re not just pushing the envelope. We flew a 7,000-pound test vehicle right through it.”
This test was carried out through the space agency’s Technology Demonstrations Missions program, which operates from Huntsville, Alabama’s Marshall Space Flight Center, in conjunction with the Jet Propulsion Laboratory (JPL) in Pasadena, California. NASA’s Wallops Flight Facility helped to coordinate the testing, and also provided the balloon responsible for carrying LDSD into high atmosphere.
Current Mars landing technology is based on the Viking Program’s parachute design, which was used beginning in 1976, and was most recently used during the landing of the Curiosity rover in August 2012. Landing on the Red Planet is considerably riskier than landing on other worlds. A National Geographic article from way back in January 1977 entitled “Sifting for Life in the Sands of Mars” discussed challenges faced by the two Viking landers: “Descending through the Martian atmosphere is much trickier than landing on the airless moon. The Soviets had tried to land on Mars four times, twice in 1971 and twice in 1974. In 1971 one lander crashed and the other stopped sending back data after only 20 seconds. One of the 1974 attempts just flew past Mars. Instruments on the second failed during descent, after transmitting usable data for a few seconds.”
While the “Viking method” has shown success for nearly 40 years, it is apparent that to carry much heavier payloads (including larger robotic vehicles, human crews, and their habitats) to Mars in the future, a different approach must be taken. According to NASA, larger drag devices – such as SIAD-R and SIAD-E, which is being developed – must be employed to make this happen. In addition, these systems must withstand high speeds in thin sections of atmosphere.
NASA has stated, “Together, these new drag devices can increase payload delivery to the surface of Mars from our current capability of 3,300 pounds (1.5 metric tons) to between 4,400 and 6,600 pounds (2 to 3 metric tons), depending on which inflatable decelerator is used in combination with the parachute. They will increase available landing altitudes by 1 to 2 miles (2 to 3 kilometers), increasing the accessible surface area we can explore. They also will improve landing accuracy from a margin of 6 miles (10 kilometers) to just 2 miles (3 kilometers). All these factors will increase the capabilities and robustness of robotic and human explorers on Mars.”
While current flight tests are taking place on Earth to duplicate the perilous landing conditions as much as possible, in the future – perhaps 20 or 30 years down the line – we will see devices such as SIAD and enormous parachutes successfully land the next generation of “beyond Earth” astronauts on the craggy face of the Red Planet.