The rover NASA hopes to drive across the moon’s south pole has already been assembled. It has been sitting here on Earth the entire time.
Full-scale ground replicas exist for both Curiosity and Perseverance, and scientists lean on them to trial features and software updates before those changes are uplinked to the actual vehicles on Mars. The copies were never meant to leave the ground. Now the agency wants to ship one of them — or some blend of the pair — to the moon.
A proposal for a rover named PROMISE, an acronym for Polar Rover for Observation, Mapping and In-Situ Exploration, was unveiled by the agency in late June. The plan calls for repurposing Perseverance’s engineering test model.
Exactly whose descendant it is remains fuzzy in NASA’s own announcement, which describes the new vehicle as a “hybrid” of the engineering versions of Perseverance and Curiosity — meaning it could inherit characteristics from each. In the video NASA put out about the project, footage of Perseverance touching down on Mars cuts to the stand-in still parked on Earth.
It already had a name — and a clunkier acronym
Prior to the rebrand, Perseverance’s test model answered to Operational Perseverance Twin for Integration of Mechanisms and Instruments Sent to Mars. Shortened, that’s OPTIMISM.
“We’ve had years now of experience operating the two rovers on the surface of Mars, and we’ve got this hardware that the taxpayers have invested a lot in,” NASA administrator Jared Isaacman said during an update about the agency’s moon base plans. “So the question was posed: ‘What if we send it to the moon?’ … It’s going to bring an immense capability to the lunar south pole in short order.”
Take that for what it is: a budget case wearing engineering clothes. The hardware has been bought and paid for. What nobody has priced yet is finishing it.
The plutonium is the piece that genuinely counts
The job for PROMISE would be surveying the lunar south pole — a leading candidate for future bases thanks to its plentiful water ice — and characterizing both the surface and what lies beneath it.
Power would come from a multi-mission radioisotope thermoelectric generator, or MMRTG, running on plutonium. Heat released as the plutonium naturally decays gets converted into electricity by the generator. Sunlight never enters the equation, anywhere, ever.
That gap between this design and a solar-powered rover is anything but marginal. At the poles, the lunar night finishes off any hardware that cannot keep itself warm.
“For moon-based objectives, having a nuclear RTG on it allows us to go anywhere we want, regardless of the illumination,” said Carlos García-Galán, the program manager for the Moon Base project. “Surviving the lunar night is going to be one of the bigger challenges with this capability; we wouldn’t have to worry about that.”
Most of the parts list is parts that don’t exist yet
For now PROMISE is only a concept. OPTIMISM is nowhere near flight-ready and faces a long list of modifications and upgrades before it could function as a lunar rover.
What that work entails hasn’t been spelled out by NASA. As things stand, though, the vehicle has no sensors for regulating onboard temperature, no flight-ready scientific instruments, no communications system and no generator. Nor are its components rated to withstand the abrasive, razor-sharp dust on the moon.
Boil it down and what’s being reused amounts to a chassis, a mobility system and years of hard-won operating experience. Instruments, power, thermal control and the radio all remain to be built.
How the savings pencil out
According to The Planetary Society, the NGO founded by Carl Sagan, PROMISE would run NASA somewhere between $700 million and $1.3 billion, with no launch before sometime in the early 2030s.
That is a broad range for a rover being sold chiefly on the fact that it’s already built. The metrics worth watching are whether the MMRTG gets allocated and whether the dust rating problem is solved — those are the two line items that convert a testbed into a spacecraft.