On the journey to Mars, small steps can be as valuable as giant leaps forward. The recent Low-Density Supersonic Decelerator (LDSD) test is a prime example.
Advancing scientific discovery is a key goal of NASA’s journey to Mars. With a formation and evolution similar to that of Earth’s, Mars may provide information that sheds light on our own planet’s history—and could even offer an answer to the burning question: Are we alone in the universe?
But before we send humans to Mars, we have much to learn. One critical area of exploration is how to develop the technology needed to safely land crewed missions on the surface of the red planet. Landing on Mars, with its thin atmosphere, presents a unique challenge: it requires different technology than is used to land a spacecraft on Earth, which has a dense atmosphere, or the moon, which has no atmosphere. As larger spacecraft head for Mars, new deceleration technologies are crucial.
One approach under development is the LDSD: a 100 foot-wide parachute that combines relatively low mass with the potential to generate enormous drag.
“The advanced supersonic decelerator technologies are important because they allow us to land heavier science and cargo payloads on the surface of Mars,” said Steve Jurczyk, associate administrator for NASA’s Space Technology Mission Directorate. Technically, the technology isn’t new: NASA has employed parachutes to assist with landings since the 1960s. But the size of the LDSD, which is imperative for the thin Martian atmosphere, is unprecedented.
The first LDSD flight test was conducted a year ago in Earth’s stratosphere above Kauai, Hawaii, where the thin air mimics the thin atmosphere of Mars. During that test, three new technologies were examined. The first, a supersonic inflatable aerodynamic decelerator (SIAD), was a large, balloon-like vessel designed to inflate around the spacecraft at about Mach 3 to commence the deceleration process. The second was a ballute: a combination balloon/parachute that deployed shortly after the SIAD and pulled out the LDSD parachute. The third was the LDSD itself. While the SIAD and ballute performed well, the LDSD parachute was ripped to shreds upon deployment.
Following the experiment, the LDSD was extensively reworked. All three components were then put to the test a second time on June 8, 2015, in another stratospheric trial above Kauai. Again, two of the technologies performed perfectly.
“In less than a year, we’ve had two great tests of both our SIAD and our ballute decelerator,” said Ian Clark, LDSD principal investigator at the Jet Propulsion Laboratory (JPL). “Neither of those devices existed previously. We’ve now matured them both to the point where they can be used by future planetary missions.”
The LDSD fared less well. “[W]e conducted a difficult and complex supersonic experiment in Earth’s stratosphere, and it was a successful conduct of that experiment,” said Mark Adler, LDSD project manager at JPL. “But the most obvious result of that experiment was a parachute that did not survive much past inflation.”
The parachute performed better than the year before. It inflated uniformly after deployment and achieved near or full inflation, which enabled it to generate significant drag before the tear appeared. More will be known about how the parachute behaved and how the damage occurred in the coming months as the LDSD team examines the data from the test.
“Fortunately, we have a tremendous amount of data that was collected on this vehicle,” said Adler. “We’ll be able to remedy and strengthen and change the design of the parachute appropriately.”
From a scientific perspective, the test was a success. “On this project, we are pushing the limits of our technologies, our engineering, and our understanding of aerodynamic decelerators,” said Clark. “This year, the physics of supersonic parachutes pushed back on us. I think that as an engineer, this can be a very humbling experience. But as a curious human, this can be extremely exciting. We don’t conduct tests like this to show that we know all the answers ahead of time. We conduct them to learn about what we didn’t know.”
He added, “Last year we rewrote the book on our understanding of supersonic parachutes. This year we’ve got another great set of data to add many more chapters to that tome.”
The LDSD project is sponsored by NASA’s Space Technology Mission Directorate and managed by JPL.
Watch a video in which principal investigator Ian Clark narrates a play-by-play of the first LDSD test flight in 2014.