Mothballing Rosalind: How to Put a Space Mission in Storage [Hackaday]

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In planetary exploration circles, Mars has quite a bad reputation. The Red Planet has a habit of eating spacecraft sent there to explore it, to the degree that nearly half of the missions we’ve thrown at it have failed in one way or another. The “Mars Curse” manifests itself most spectacularly when landers fail to negotiate the terminal descent and new billion-dollar craters appear on the Martian regolith, while some missions meet their doom en route to the planet, and an unlucky few have even blown up on the launchpad.

But the latest example of the Mars Curse, the recent cancellation of the second half of the ExoMars mission, represents a new and depressing failure mode: war — specifically the Russian invasion of Ukraine. The international outrage over the aggression resulted in economic sanctions and diplomatic isolation of Russia, which retaliated by ending its partnership with the European Space Agency (ESA), depriving the mission of its launch vehicle and dooming the mission that would have landed the rover Rosalind Franklin on Oxia Planum near the Martian Equator in 2023.

While there’s still a chance that administrators and diplomats will work things out, chances are slim that it will be in time for the narrow launch window that the mission was shooting for in September of 2022. That means the Rosalind Franklin, along with all the other flight hardware that was nearly ready to launch, will have to be put in storage at least until the next launch window opens in 2024. That begs the question: how does one put a complex spacecraft into storage? And could such mothballing have unintended consequences for the mission when it eventually does fly?

Electricity and Heaters

Before the confounding effects of human armed conflict even came into play, the ExoMars mission was very ambitious and quite complicated. Planning dates back to the early 2000s, when the ESA and NASA entered into a joint agreement for a mission that would include orbiters, rovers, and even a sample-return aspect. But in 2012, NASA, which was to provide the launch vehicle and descent platform for the ExoMars rover, backed out of the partnership, due to budget constraints caused at least in part by cost overruns on the James Webb Space Telescope. This resulted in ESA entering into a full partnership with Roscosomos for launches aboard their Proton launch vehicles, as well as provision of the descent vehicle needed to get the rover safely down to Mars.

Storage can hurt: Galileo with its lube-starved high-gain antenna. Source: NASA

The loss of performance by lubricants on spacecraft in storage is no joke, and nearly cost NASA the Galileo flyby mission of Jupiter in the 1990s. Galileo had been in storage for four and a half years before its launch, thanks in part to the Challenger disaster. By the time antenna deployment was attempted during the transit to Jupiter, the lubricants intended to provide a smooth release of the antenna ribs had been in place for over a decade, and were severely degraded. This left the antenna partially deployed and greatly impacted data throughput.

As a result of this mishap, the effects of pre-flight storage on critical lubricants have been extensively studied, with the conclusion being that molybdenum disulfide greases are best stored under “dry nitrogen” conditions, along with the occasional exercise of critical mechanisms to ensure that greases don’t stratify, or have their base oil separate from the soap used to thicken them. Engineers also need to be cautious of seals and other non-metallic components in contact with lubricants, which may soak up a significant amount of the base oil and thicken the reservoir of grease to the point of eventual joint failure.

While these are the high points, chances are good a mission as complex as ExoMars will have a thousand other details that will need to be seen to in order to ensure that Rosalind Franklin and Kazachok are kept in good order and ready to fly, hopefully when the next launch window comes around.