NASA / Johns Hopkins APL
NASA’s Dragonfly Completes First Simulated Flight (News Release)
Separated from its protective backshell, NASA’s
Dragonfly rotorcraft autonomously speeds over the sand dunes of Titan. It scans the terrain below, searching for a safe place to land. When Dragonfly discovers a safe site, it turns, descends and lands at the selected location, touching down for the first time on the surface of Saturn’s largest moon.
A successful first flight – except, this wasn’t happening on Titan itself, but on a computer testbed at the Johns Hopkins Applied Physics Laboratory
(APL) in Laurel, Maryland, where the Dragonfly rotorcraft is undergoing integration and testing. It was the most comprehensive test to date of Dragonfly’s “first flight” in real time on flight-like avionics, incorporating most of the systems and maneuvers that the rotorcraft will employ when it arrives at Titan in 2034.
Dragonfly is scheduled to launch no earlier than 2028 for a six-year voyage to Saturn’s moon Titan, where it will spend three years flying from location to location to explore a range of sites to study the chemistry, geology and atmosphere of the Earthlike moon and ultimately advance our understanding of life’s chemical origins.
“The cool thing about first flight is that it’s our most challenging flight,” said Zach Putnam, Dragonfly mobility subsystem lead engineer at APL. “It uses every piece of flight sensor hardware on the lander.”
The recent test brought together flight software and avionics with simulated data input from the sensors that Dragonfly will use at Titan, including its newly-installed navigation cameras, inertial measurement units, and lidar system.
It was a milestone years in the making. The team has built Dragonfly’s flight capabilities incrementally, beginning with simulations of relatively simple activities such as the spinning of a single rotor. Later tests demonstrated a short “reposition” flight and a partial scouting flight, adding more sensors and capabilities at each step.
“Doing it incrementally is what enabled us to build these tests at all,” said Putnam. Adding lidar — the system that Dragonfly will use to measure terrain altitude and slope and identify potential hazards — provided the final piece needed to fully simulate what the rotorcraft will encounter on Titan.
The team generated simulated terrain for the lidar and created, in real time, the images that Dragonfly’s navigation cameras would see. A custom camera emulator used graphics processing units to render each simulated Titan scene in roughly the same 20 to 70 milliseconds exposure times that Dragonfly’s cameras will use during flight.
Running the complete sequence on flight-like hardware gave the team an important opportunity to see how all those pieces interact — including those details measured in milliseconds as information zips between different processes aboard the lander.
“These tests provide an important validation that everything works together,” said Putnam.
And there are many more tests to come. The team plans to run first flight on Dragonfly’s actual flight system, not a testbed, using the rotorcraft’s avionics. Engineers will also test other flight profiles and deliberately introduce faults to make sure that Dragonfly can respond autonomously if something goes wrong.
“That autonomy is essential at Titan, where Dragonfly will have to fly without real-time help from Earth,” Putnam said. “Everything we do on Titan has to happen autonomously.”
Striking a pose
Before Dragonfly can make that first flight on Titan, it has to shift into position to be able to fly. Testing is also underway to ensure that the mechanisms handling that critical step will lower the rotorcraft below the entry system’s backshell, where it can safely start its rotors prior to separation from the entry system and begin its final descent to Titan’s surface.
The test campaign evaluates Dragonfly’s “pose” mechanism, the system that will lower the rotorcraft from its stowed position inside the backshell into position for release during the descent at Titan. Engineers at Lockheed Martin in Colorado – where the elements of Dragonfly’s interplanetary cruise stage and atmospheric entry, descent and landing assembly are coming together – recently conducted static tests with representative mass, pushing and pulling on the mechanism to verify that it can withstand expected loads, as well as deployment tests to see how smoothly and quickly the system lowers, and whether it locks securely into place.
The tests also consider how Dragonfly’s backshell may swing beneath its parachute when the rotorcraft is deployed. Engineers tilt the test hardware to different angles and repeat the deployment to confirm that the mechanism performs properly across a range of conditions.
The pose structure connects the backshell to an aluminum interface structure that attaches to the Dragonfly lander. During the actual descent, the pose mechanism will lower that interface — and Dragonfly with it — before the rotorcraft separates and begins flying under its own power. The testing is designed to make sure that this critical transition works reliably before Dragonfly has to ever perform it nearly a billion miles from Earth.
Source: NASA.Gov
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NASA / Johns Hopkins APL / Ed Whitman
Lockheed Martin
