Differences in the design of a commercial Moon rover and a commercial Mars rover?

Question

News in May, 2018:

• Spaceflight Now NASA cancels lunar rover, shifts focus to commercial moon landers
• Washington Post Stunning scientists, NASA’s only moon rover just got canceled
• Space.com NASA Kills Lunar-Resources Mission Despite Push to Return to the Moon
• The Verge NASA scraps a lunar surface mission — just as it’s supposed to focus on a Moon return

News in July, 2018:

• Airbus is designing a Mars rover to return soil samples

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The news items above are included as background information that got me thinking of the following question.

For a similar mission of covering significant distance carrying a given experimental/observational package together with a robotic arm to pick up samples, what would be the differences between a rover build for the Moon versus a similar one built for Mars?

Would it be fairly straightforward to make small changes to a rover built for one body to optimize it for operation on the other body, or are there issues that would end up making one very different from the other?

For the purposes of this question let's call the "rover" the equivalent of a satellite's bus, and the experimental package and robotics as the "payload", and assume the payloads are identical or at least similar. Let's also assume the terrain is similarly "rover-friendly" in that there are no large rocks or extreme slopes in either case. However, there may be differences in regolith that can't be ignored, as one body has always had much more of an atmosphere than the other.

Answer 1

Would it be fairly straightforward to make small changes to a rover built for one body to optimize it for operation on the other body?

Small? No. If you design with both bodies in mind, making it modular where needed, then possibly so, although the design would be suboptimal. If you design for one, you're straying from the other quite far.

First, matters of guidance. 3 seconds of ping are quite manageable after proper training, for fully interactive control. The minutes to hours in case of Mars will require either partial self-driving capacity, or long wait periods. Similarly, the lunar rover on near side of the Moon can communicate with ground stations directly. The Martian one will require either a freakishly strong radio or a relay satellite.

Next, energy. Martian winter still gets enough sunlight to sustain the heaters to keep the batteries from dying - although in general the amount of sunlight is much lower. Moon gets two weeks of total darkness with not even the thin atmosphere to keep the deep space from sucking heat out of everything. More violent temperature changes, way deeper, much longer night, much brighter, hotter day. Completely different energy and heat management systems. (...unless you go with RTG. On a commercial craft? U mad?)

Surprisingly, for landing it's not that different. Don't pack the parachute and heatshield for the Moon. Rocket-based skycrane will be of comparable requirements for both. Unless you go for airbag landing on Mars, which is just not viable for the Moon.

The lunar rover will operate in full vacuum, so all mechanics must be vacuum-proofed. The Martian rover will travel through vacuum for a long time though, so unless you choose to make the landing capsule (heatshield/skycrane) airtight and minimally pressurized (to Martian levels?) you'll need to vacuum-proof it, at least partially.

The lunar regolith is more abrasive... but in the large scale of things that's not as big a problem unless you want another rover with 5000%+ lifetime expectation exceeded. But without wind, don't count on dust devils cleaning the solar panels - OTOH dust will only fly and settle on the panels if you arouse it. So these considerations are pretty different.

It remains to be determined how much would be left unchanged - and if it would be worth it; e.g. if a system must be more robust to fulfill needs of one body, it will work just fine on the less demanding one - but it will be more expensive than necessary. Will it be more expensive than developing a dedicated cheaper version would? That would need an in-depth analysis.

In short, the idea is technically viable, but its economy is questionable - and that's developing a rover for both bodies since moment one. If you develop for one, then try to adapt for the other, you're not getting nearly any savings.

Answer 2

While you could set out to design a modular space probe, considering the costs of getting it to moon or Mars, I think it would be more wise to design the probe fully purposed for the mission. actually the only possible benefit to a modular probe would be any reduction in probability of losing a probe over all its missions due to similar design, if there is a reduction.

First, your roving sections mass and volume will have different envelopes for each mission due to distances and the aerodynamic requirements of Mars. For the cost of getting the rover to the surface mass and volume should be maximized thus proving unlikely the two optimal points coincide.

Additionally you would also have to consider how different chemistries and the presence of atmosphere or different pressures effect the scientific experiments size, mass.

Additionally communication and power requirement are probably going to be larger for Mars. Energy more difficult to obtain on Mars, higher gain and thus larger and less efficient antenna requiring more power.

They are literally two separate world. The better question may be what can be accomplished with a modular design to even persuade the consideration? To me it seems not much is gained outside of opportunity to prove designs that have commonality, possible reducing uncertainty in performance. I don't think there would be a cost benefit as a useful modular design may be more complex and perform poorer than a purpose built design.