Engineers are developing the crucial hardware needed for a series of daring
space missions that will be carried out in the coming decade.
Testing has already begun on what would be the most sophisticated endeavor
ever attempted at the Red Planet: Bringing rock and sediment samples from
Mars to Earth for closer study.
The multi-mission Mars Sample Return campaign began when NASA's Perseverance
rover landed on Mars this past February to collect Martian rock samples in
search of ancient microscopic life. Out of Perseverance's 43 sample tubes,
four have been filled with rock cores and one with Martian atmosphere. Mars
Sample Return seeks to bring select tubes back to Earth, where generations
of scientists will be able to study them with powerful lab equipment far too
large to send to Mars.
Getting those samples into terrestrial labs would take a decade and involve
European partners and multiple NASA centers. ESA (the European Space Agency)
is developing a rover for the effort, with engineers at NASA's Glenn
Research Center in Cleveland, Ohio, designing its wheels. The rover would
transfer samples to a lander, being developed at NASA's Jet Propulsion
Laboratory in Southern California, that would use a robotic arm (developed
by ESA) to pack the samples into a small rocket, called a Mars Ascent
Vehicle, being designed by NASA's Marshall Space Flight Center in
Huntsville, Alabama.
The rocket would launch from the lander to deliver the sample capsule to an
ESA spacecraft orbiting Mars. Inside the orbiter, the capsule would be
prepared for delivery to Earth by hardware that a team led by NASA's Goddard
Space Flight Center in Greenbelt, Maryland, is developing. This preparation
would include sealing the sample capsule within a clean container to trap
any Martian material inside, sterilizing the seal, and placing the sealed
container into an Earth-entry capsule before the return trip to Earth.
The lander
To develop the lander, as well as the system that would help launch the
sample-laden rocket from it, engineers at NASA's JPL are drawing from a long
history of Mars exploration: JPL has led nine successful Mars landings,
including rovers and stationary landers. But the Sample Retrieval Lander
would be the largest, heaviest spacecraft of its type to ever go to Mars,
and the Mars Ascent Vehicle launching from it would be the first rocket ever
fired off another planet.
This is where the testing comes in.
To carry and launch the Mars Ascent Vehicle, the lander needs to be a sturdy
platform, weighing about 5,291 pounds (2,400 kilograms)—almost twice as
heavy as Perseverance, which was lowered to the Martian surface with cables
from a rocket-powered jet pack. The Sample Retriever Lander wouldn't have a
jet pack; its legs would have to absorb the impact of touchdown, relying on
retrorockets to slow its descent, similar to recent Mars lander missions
like InSight and Phoenix.
That's why Pavlina Karafillis has been dropping a prototype
lander—repeatedly—in a warehouse-like space at JPL. As test engineer for the
Sample Retrieval Lander's legs, she and her colleagues have been using
high-speed cameras to observe this prototype's legs slam onto a base.
QR-code-like marks on each of the prototype's "feet" help the cameras track
the legs' motion. The team uses slow-motion video to continually update
their computer models, which help them understand how energy would be
dispersed throughout the lander.
"The last step of the journey is really important," Karafillis said.
"There's all kinds of landing conditions you have to take into account, like
rocks, or really soft sand, or coming in at an angle. This is why we have to
do all this testing."
Karafillis and her colleagues have started with a prototype roughly
one-third the size of what the actual spacecraft would be; a lighter
prototype is one way to learn how the final lander design would move in
Mars' low gravity. Later in the program, they will drop a full-scale lander
as well.
The rocket
Surviving landing is just part of the challenge: Safely launching the
nine-foot-long (2.8-meter-long) two-stage rocket that will sit atop the
lander's deck adds another level of difficulty. Mars' gravity is one-third
that of Earth's, and the rocket's weight, combined with its exhaust, could
cause the lander to slip or tilt.
So engineers have conceived of a system to toss the rocket into the air just
before it ignites. The whole process happens in a finger-snap, tossing the
rocket at a rate of 16 feet (5 meters) per second.
During testing, a cradle equipped with gas-powered pistons flung an
881-pound (400-kilogram) mock rocket 11 feet (3.3 meters) in the air; cables
suspended from a tower 44 feet (13 meters) high offloaded more than half of
the test article's weight to simulate Martian gravity.
"It's kind of like being on a really fast roller coaster when someone hits
the brakes," said Chris Chatellier, the system's lead engineer at JPL.
"There are a lot of safety aspects to consider. Testing happens in a very
controlled sequence of events with everyone outside of the building."
This system, known as Vertically Ejected Controlled Tip-off Release (VECTOR)
system, also adds a slight rotation during launch, which pitches the rocket
up and away from the Martian surface.
"Launching with VECTOR means the lander could be oriented the wrong way on a
slope, and we could still pull this off," Chatellier said.
Chatellier and his team have conducted 23 tests this year, changing the
rocket's mass and center of gravity along the way. They also added springs
to the bottom of their lander stand-in, watching how much "bounce" the
launch system created. Next year, they'll toss a heavier rocket even higher.
"We're on the right path," Chatellier said. "Our analysis and predicted
models were very close to what we saw in the tests."
More about Mars sample return
NASA's Mars Sample Return (MSR) will revolutionize our understanding of Mars
by returning scientifically-selected samples for study using the most
sophisticated instruments around the world. The mission will fulfill a solar
system exploration goal, a high priority since 1980 and the last two
National Academy of Sciences Planetary Decadal Surveys.
This strategic partnership of NASA and ESA (European Space Agency) will be
the first mission to return samples from another planet, including the first
launch and return from the surface of another planet. These samples
collected by Perseverance during its exploration of an ancient river-delta
are thought to be the best opportunity to reveal the early evolution of
Mars, including the potential for life.
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