Engineers are developing critical hardware for the mission to collect and return Martian samples to Earth in the next decade.
The engineering teams from NASA and the European Space Agency (ESA) have begun testing systems for the most complex mission on the Red Planet: bringing back rock and soil samples from Mars for further study. The Mars Sample Return campaign consists of multiple missions starting with NASA’s Perseverance rover landing on Mars in February last year to collect rock and soil samples in search of ancient microbial life. Out of the 43 sample tubes collected by Perseverance, 4 tubes are filled with rock cores and one tube contains Martian air. The Mars Sample Return campaign aims to bring some of these tubes back to Earth, where scientists can analyze the samples using powerful laboratory equipment that is too bulky to send to Mars.
Simulation of the sample retrieval robot and the transport rocket landing on Mars. (Photo: NASA).
The process of bringing samples back to Earth will take a decade, involving collaboration with ESA and various NASA centers. ESA is developing a rover to collect samples while engineers at NASA’s Glenn Research Center in Cleveland, Ohio, design the wheels. The rover will transfer the samples to a lander currently being developed at NASA’s Jet Propulsion Laboratory (JPL) in Southern California. This lander will utilize a robotic arm developed by ESA to place the samples into a small rocket known as the Mars Ascent Vehicle, designed by NASA’s Marshall Space Flight Center in Huntsville, Alabama.
The rocket will launch from the lander to transport the sample container to the ESA spacecraft orbiting Mars. Inside the orbiting spacecraft, the sample container will be prepared for its journey back to Earth with hardware developed by a team led by NASA’s Goddard Space Flight Center in Greenbelt, Maryland. The preparation process will include locking the sample container inside a sterile container to protect the Martian material, sterilizing the lock, and placing the container into a reentry capsule before the flight back to Earth.
To develop the lander and the systems needed to launch the sample rocket, engineers at JPL are drawing on lessons learned from the history of Mars exploration. JPL has led 9 successful landing missions on Mars, including rovers and static landers. However, the Sample Retrieval Lander will be the largest and heaviest spacecraft to fly to Mars, and the Mars Ascent Vehicle will be the first rocket to launch from another planet.
To carry and launch the Mars Ascent Vehicle, the lander needs to be a sturdy launch platform, weighing 2,400 kg, nearly double that of the Perseverance rover. The lander will touch down on the Martian surface using cables from a rocket-powered landing system. The legs of the Sample Retrieval Lander will absorb the impact forces upon landing, relying on rocket thrust to slow down, similar to recent Mars missions like InSight and Phoenix.
This is why test engineer Pavlina Karafillis has repeatedly dropped a prototype of the lander in a space resembling a cargo hold at JPL. She and her team use high-speed cameras to observe the legs of the prototype impacting the ground. QR code-like markings on each leg of the prototype help the cameras track movement. The engineering team uses slow-motion video to continuously update computer models, helping them understand how impact forces are distributed throughout the lander. Karafillis and her colleagues started with a large prototype about 1/3 the size of the actual spacecraft. Using a lighter prototype is a way to understand how the final lander design will move under Mars’ weak gravity. By the end of the program, they will drop a full-sized lander prototype.
Successfully landing is just part of the challenge. Successfully launching a 2.8-meter tall, two-stage rocket from the lander adds a new level of difficulty. Mars’ gravity is only 1/3 that of Earth, so the weight of the rocket combined with the thrust can cause the lander to tip or topple. Therefore, engineers have developed a system to eject the rocket into the air before ignition. The entire process occurs in the blink of an eye, with the rocket being thrown at a speed of 5 m/s.
During testing, a rig equipped with a thrust valve launches a 3.3-meter-long dummy rocket into the air. Cables suspended from a 13-meter-high tower support over half the weight of the prototype to simulate Mars’ gravitational force. This system, known as Vertically Ejected Controlled Tip-off Release (VECTOR), also generates a slight rotational force during launch. Chatellier and her team have conducted 23 tests this year, varying the mass and center of gravity of the rocket throughout the process. Next year, they will test launching a heavier version of the rocket to greater heights.
This will be the first mission to bring samples from another planet back to Earth. The samples collected by the Perseverance rover while exploring the ancient river delta represent the best opportunity to understand the evolution of Mars in its early days, including the potential for life.
