2020-08-04 21:17:48 UTC
in Titan's atmosphere. Much denser atmosphere
and higher pressure, little winds, lower gravity
all translate to flight power needed per unit mass
is...40 times lower than on Earth.
Dragonfly is a planned spacecraft and mission of NASA, that
will send a mobile robotic rotorcraft lander to Titan,
the largest moon of Saturn, in order to study prebiotic
chemistry and extraterrestrial habitability at various
locations where it will perform vertical-takeoffs
and landings (VTOL).
The CAESAR and Dragonfly missions received US$4 million funding each
through the end of 2018 to further develop and mature their
concepts. NASA announced the selection of Dragonfly on 27 June 2019,
to build and launch in April 2026
Dragonfly will be a rotorcraft lander, much like a large quadcopter with
double rotors, an octocopter. Redundant rotor configuration will
enable the mission to tolerate the loss of at least one rotor or
motor. Each of the craft's eight rotors will be about 1 m in
diameter. The aircraft will travel at about 10 m/s or 36 km/h and
climb to an altitude of up to 4 km.
Flight on Titan is aerodynamically benign as Titan has low gravity and
little wind, and its dense atmosphere allows for efficient rotor
propulsion. The RTG power source has been proven in multiple
spacecraft, and the extensive use of quad drones on Earth provides a
well-understood flight system that is being complemented with algorithms
to enable independent actions in real-time. The craft will be
designed to operate in a space radiation environment and in temperatures
averaging 94 K (−179.2 °C).
Titan's dense atmosphere and low gravity means that the flight power for
a given mass is a factor of about 40 times lower than on Earth. The
atmosphere has 1.45 times the pressure and about four times the density
of Earth's, and local gravity (13.8% of Earth's) will make it easier to
fly, although cold temperatures, lower light levels and higher
atmospheric drag on the airframe will be challenges. Dragonfly will
be able to travel significant distances, powered by a battery that will
be recharged by a Multi-Mission Radioisotope Thermoelectric Generator
(MMRTG) during the night. MMRTGs convert the heat from the natural
decay of a radioisotope into electricity, although increased mass and
surface area might sacrifice control. The rotorcraft will be able to
travel tens of kilometers on every battery charge and stay aloft for a
few hours each time. The vehicle will use sensors to scout new
science targets, returning to the original site until new landing
locations are verified as safe by mission controllers.
Preliminary studies and modeling contemplate a baseline 450 kg (990 lb)
mass for the rotorcraft packed in a 3.7 m diameter heatshield.
Samples will be obtained by two sample acquisition drills and hoses, one
on each landing skid, for delivery to the mass spectrometer instrument.
The craft will remain on the ground during the Titan nights, which last
about 8 Earth days or 192 hours. Activities during the night may
include sample collection and analysis, seismological studies like
diagnosing wave activity on the northern hydrocarbon seas,
meteorological monitoring, and local microscopic imaging using LED
illuminators as flown on Phoenix lander and Curiosity rover. The
craft will communicate directly to Earth with a high-gain antenna.