Page 27 - EngineerIT October 2021

SPACE

The first mission to the Trojan Asteroids

ime capsules from the birth of our solar destinations on schedule, while the solar arrays –
system more than 4 billion years ago, the each the width of a school bus – will recharge the
Tswarms of Trojan asteroids associated batteries that will power space craft instruments.
with Jupiter are thought to be remnants of the The Lucy space craft will soon be packed into
primordial material that formed the outer planets. the two halves of the launch vehicle fairing, which
The Trojans orbit the Sun in two loose groups, will close around it like a clam shell. After the
with one group leading ahead of Jupiter in its space craft is encapsulated, the Lucy team will be
path, the other trailing behind. Clustered around able to communicate with it electrically through an
the two Lagrange points equidistant from the Sun “umbilical cord.”
and Jupiter, the Trojans are stabilised by the Sun “Launching a space craft is almost like sending
and its largest planet in a gravitational balancing a child off to college – you’ve done what you
act. These primitive bodies hold vital clues to can for them to get them ready for that next big
deciphering the history of the solar system. step on their own,” said Hal Levison, the principal
Lucy will be the first space mission to study investigator of the Lucy mission, based at the
the Trojans. The mission takes its name from the Southwest Research Institute in Boulder, Colorado.
fossilised human ancestor (called “Lucy” by her In early October, the encapsulated space craft
discoverers) whose skeleton provided unique will be transported to the Vehicle Integration Facility
insight into humanity’s evolution. Likewise, the Lucy ready to launch at the Cape Canaveral Space Force Station, where
Lucy mission will revolutionise our knowledge of it will be “mated” with the United Launch Alliance
planetary origins and the formation of the solar system. Atlas V 401 rocket. The Atlas V will lift off from Space Launch
Lucy will launch in October 2021 and, with boosts from Earth’s Complex 41. The rocket will carry Lucy outside Earth’s atmosphere to
gravity, will complete a 12-year journey to eight different asteroids — a begin the long journey to the Trojan asteroids.
Main Belt asteroid and seven Trojans, four of which are members of A few days prior to launch, engineers will power up the Lucy
“two-for-the-price-of-one” binary systems. Lucy’s complex path will space craft in preparation for the mission. This process will take
take it to both clusters of Trojans and give us our first close-up view about 20 minutes.
of all three major types of bodies in the swarms (so-called C-, P- and “The space craft will sit in launch configuration and the
D-types). engineering team will continuously monitor its health and status to
The dark red P- and D-type Trojans resemble those found in the make sure Lucy is ready to go,” said Jessica Lounsbury, the Lucy
Kuiper Belt of icy bodies that extends beyond the orbit of Neptune. project systems engineer at Goddard. “And then it’s launch day.” n
The C-types are found mostly in the outer parts of the Main Belt of
asteroids, between Mars and Jupiter. All of the Trojans are thought to
be abundant in dark carbon compounds. Below an insulating blanket of
dust, they are probably rich in water and other volatile substances.
No other space mission in history has been launched to as many
different destinations in independent orbits around our sun. Lucy will
show us, for the first time, the diversity of the primordial bodies that
built the planets.
“With Lucy, we’re going to eight never-before-seen asteroids in 12
years with a single space craft,” said Tom Statler, Lucy project scientist
at NASA headquarters in Washington. “This is a fantastic opportunity
for discovery as we probe into our solar system’s distant past.”
Following all pandemic protocols, Lucy team members have spent
the past eight weeks at NASA’s Kennedy Space Centre in Florida,
preparing the space craft for flight. Engineers have tested the space
craft’s mechanical, electrical and thermal systems and practiced This diagram illustrates Lucy’s orbital path. The space craft’s path (green) is
executing the launch sequence from the mission operations centres at shown in a frame of reference where Jupiter remains stationary, giving the
Kennedy and Lockheed Martin Space in Littleton, Colorado. trajectory its pretzel-like shape. After launch in October 2021, Lucy has two
close Earth fly-bys before encountering its Trojan targets. In the L4 cloud, Lucy
In early August, engineers installed the space craft’s high-gain will fly by (3548) Eurybates (white) and its satellite, (15094) Polymele (pink),
antenna, its second most prominent feature after the expansive solar (11351) Leucus (red), and (21900) Orus (red) from 2027-2028. After diving past
arrays, which will allow the space craft to communicate with Earth. Earth again Lucy will visit the L5 cloud and encounter the (617) Patroclus-
On 18 September, propulsion engineers finished filling Lucy’s fuel Menoetius binary (pink) in 2033. As a bonus, in 2025 on the way to the L4,
tanks with approximately 725 kilogram of liquid hydrazine and liquid Lucy flies by a small Main Belt asteroid, (52246) Donaldjohanson (white),
named for the discoverer of the Lucy fossil. After flying by the Patroclus-
oxygen, which make up 40% of the mass of the spacecraft. The fuel Menoetius binary in 2033, Lucy will continue cycling between the two Trojan
will be used for precise manoeuvres that will propel Lucy to its asteroid clouds every six years. Credits: Southwest Research Institute

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