There is a perception that NASA’s Mars Sample Return (MSR) mission is being delayed by indecision, but the real delay has been multiple decades of seeking a heritage propulsion solution instead of a technology advance to develop and test a Mars Ascent Vehicle (MAV) for launching the samples to Mars orbit. Imagine needing a sophisticated Mars rover in the absence of JPL’s core team of engineers with their decades of specialized design and testing. Now a MAV is needed, absent any comparable cadre of expertise for miniature launch vehicles. The MAV remains a wildcard for MSR, possibly even a hot potato, because there is no experience base for making such a rocket small enough to deliver to Mars within a science mission budget. There are no other customers to stimulate investment for something like a MAV, and there is no established peer review system for technical guidance.
It seems worthy of concern that rocket engineering has not been represented among MSR advisory committees and decision makers including the MSR Standing Review Board, Planetary Decadal Survey committees, the second MSR Independent Review Board (IRB-2 in 2023), and the MSR hierarchy within the NASA Science Mission Directorate. It is not surprising that MAV expertise is underrepresented, because the available talent pool at the top of the org chart comes from planetary and other space science missions, and Earth satellite programs. These highly experienced spacecraft systems engineers and managers have always enjoyed the availability of proven propulsion technology for maneuvers that are far easier than Mars departure. Therefore, MAV development has been consistently underestimated.
Given that MAV success is mission-critical, NASA planning documents circa 2010 called for successful flight testing of a MAV over Earth, prior to preliminary design review for MSR. By 2020, that requirement had vanished from mission planning, as though launching from Mars is just another propulsive maneuver for a spacecraft. Spacecraft propulsion has built-in redundancy, while launch vehicles are far less fault tolerant. Unlike launching from Earth, the MAV will not enjoy the luxury of a team on the ground for pre-launch repairs and adjustments, which raises the bar for reliability. That bar is raised even higher by NASA’s expectation of placing all 30 sample tubes on the one-and-only MAV departure from Mars.
In October 2020, the report to NASA from the first MSR Independent Review Board (IRB-1) explained the underlying MAV challenge, noting that “the smaller a launch vehicle, the more sensitive its dry mass to design uncertainty.” Variations in the dry mass are amplified at least five times for the total MAV mass, considering that propellant mass approaches 80% of the whole MAV. Some originality in engineering is needed to make all the parts unusually lightweight relative to the propellant mass and thrust, so a sufficiently small MAV might be considered new technology.
The membership of MSR IRB-1 included Antonio Elias, a seasoned rocket engineer who presided over development of the Pegasus small launch vehicle in the 1980s. In December 2020, he explained in a public meeting of the National Academies’ Planetary Decadal Survey that it is generally not possible to dictate both the mass of a launch vehicle and the mass of its payload in advance of completing design and testing, with some iteration and refinement. Hence the goal to accommodate all 30 sample tubes leaves the total MAV mass uncertain.
In 2022, the Planetary Decadal final report set the highest priority for MSR, but made no mention of the wisdom from Elias. The publication, “Origins, Worlds, and Life,” refers to the MAV in only one place, and moreover says that it would be accompanied by a European sample-fetch rover, later abandoned due to payload mass limits. Appendix B of the Decadal report lists my own submissions from 2020 about the MAV, which noted the need for a sustained effort beyond design-build engineering, explained 25 misconceptions, and described options for implementing launch vehicle design principles on a miniature scale.
On April 15, 2024, NASA announced a competition for “Rapid Mission Design Studies” in search of cost and schedule improvements for completing MSR. That news emphasized hopes for a smaller MAV derived from heritage technology, subsequently a key consideration for a dozen studies done over the summer. In a Jan. 7, 2025 news conference, little was said about fresh ideas for a smaller MAV, despite the many proposals submitted. Instead, NASA officials explained that two options will now be considered for the sample retrieval lander needed to deliver the MAV. As reported in SpaceNews, the delivery alternatives are the heritage “sky crane” from JPL, or a commercially provided “heavy lander.” The implicit message is that options will now be considered for delivering a heavier MAV if it cannot be made small.
Ideally, the MAV can be 350 kilograms or less for delivery by JPL, while a heavy lander would be needed for a large MAV. Support equipment for the MAV and other essentials will ride along, respectively raising the total landed mass to roughly a ton or potentially well over one ton.
Reaching Mars orbit from the surface requires a propulsive capability way beyond all previous experience for spacecraft maneuvers, approximately 4,000 meters per second in a few minutes. Some spacecraft can produce this velocity change, but way too gradually. As I told the Mars science community in a July 2024 presentation, the planned solid-propellant MAV could reach a thousand miles if flight tested over Earth, starting at a high altitude where the air is as thin as the Mars atmosphere. Such a flight path has never been done by any missile smaller than a ton.
The January 2025 news conference briefly referred to the two-stage solid propellant MAV that NASA has been planning. Technical details were most recently published by the Marshall Space Flight Center (MSFC) in early 2022, before Lockheed-Martin was brought on board to help. The MSFC authors described remaining challenges with the design, including aerodynamic complexities during first stage flight, the location of steering thrusters close to the center of mass, and the possibility of tip-off rotation at stage separation. They wrote that it would be ideal to flight test a complete prototype MAV over Earth, but that the cost would be high.
The combination of first stage aerodynamic complexities and low leverage for steering thrusters suggests a risk of prematurely running out of steering propellant in the absence of flight testing to fully understand vehicle dynamics and verify margins. To reduce mass, the upper stage is to be spin-stabilized instead of actively guided, a design change made public early in 2021. Additionally for mass reduction and contrary to the 2010-era documents, the upper stage might not have telemetry, hence “no data” if imperfect spinning slips past stability margins to become a mission-ending tumble.
Now that Lockheed is working on the MAV, it is notable that in 2001 the company told NASA that a flight demonstration over Earth would be needed, while only testing MAV parts separately as done for spacecraft propulsion would mean a high risk of mission failure. In a 2012 publication, Lockheed wrote that “a systematic systems engineering process” would lead to a high-heritage low-risk MAV under 300 kg. Contractors sometimes need to say what customers want to hear.
China plans to do MSR using Long March 5 launches from Earth, which can send more mass toward Mars than the Atlas 5 that launched Perseverance. The difference is consistent with a heavier Mars lander than the JPL sky crane, hence a relatively heavy MAV. Larger objects slow down less readily in the thin Mars atmosphere, necessitating some degree of new technology for Mars arrival. Ten years ago, NASA studied options for deployable or inflatable aerodynamic decelerators followed by supersonic retropropulsion, using capabilities from Blue Origin and SpaceX. Implementing MSR with a heavy lander and a larger MAV would be a worthy step toward scaling up to human missions, deserving of some Artemis funds for MSR.
Rock core samples are now waiting on Mars, but the status of MAV development has changed little over more than two decades. It might help to begin open engineering discussions akin to public science discussions, and for rocket engineering expertise to be elevated to a higher position on the MSR org chart. Perhaps the MAV needs a glamorous name, to be publicized as “the most amazing little rocket ever built.”
John Whitehead, PhD is a former rocket technology researcher. His 2008 paper, “Defining the Mars Ascent Problem for Sample Return” explained that developing a MAV is both a daunting technical problem and a cultural challenge for the planetary science community
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