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106 votes
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Why do most space probes survive for far longer than they were designed for?

Very good question! The answer boils down to statistics of failure. Some aspects involve the statistics of "random" failures—for some reason some critical component just bites the dust—and some ...
70 votes

How were Perseverance's cables "cut" after touching down?

I believe the mechanism is this pyro-cutter, photographed by Emily Lakdawalla here. Specifically, I think they were manufactured by PacSci EMC, since they brag about it in this Facebook post. If you'd ...
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67 votes
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Why aren't we sending quadcopters to mars?

Mars has two disadvantages compared to Earth: it's farther form the Sun, so you get less sunlight. Atmospheric density on Mars is 0.011 kg/m3 (at the surface, at a temperature of 0 °C). On Earth: 1....
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57 votes
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What was NASA's "Hack" to improve Opportunity's memory in 2015? Did it help?

They reformatted the flash memory area and, after finding the defective memory bank, modified the software in the rover to avoid using that area. The hack in itself reduces the amount of available ...
55 votes
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Have any of the rovers ever recorded a solar eclipse on Mars?

No, because Mars can't have eclipses. Strictly speaking, Mars has only transits. The difference is that Mars's moons are smaller than the Sun as viewed from Mars, thus they don't block out the entire ...
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52 votes

Why do most space probes survive for far longer than they were designed for?

There are a lot of generic answers here about spacecraft. I will try to answer the question specifically for Spirit and Opportunity. 90 sols was deemed sufficient to conduct the primary mission of ...
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51 votes
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Why exactly do robots freeze? How could we engineer around it?

There are many things that change at low temperatures. You already mentioned batteries, which are problematic for two reasons: First, liquid electrolytes get frozen at some point. Second, chemical ...
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48 votes

Planetary rovers - six wheels vs four?

Short answer: More wheels results in greater stability, allowing the rover to traverse more varied types of terrain. It also provides redundancy, in case one of the wheels breaks, the rover is not ...
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46 votes
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What was the last message to Opportunity today (13 Feb '19)?

From ArsTechnica: Late Tuesday night, scientists at NASA's Jet Propulsion Laboratory sent their final data uplink to the Opportunity rover on Mars. Over this connection, via the Deep Space Network, ...
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46 votes
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Is there any way to land a rover on the Moon without using any thrusters?

It is not practical to use this approach from orbital (1.6km/s) or escape velocity (2.4km/s), for two major reasons. The first is the acceleration reason. The kinematic for bringing objects to a stop ...
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43 votes
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Why isn't there research to build a standard lunar, or Martian mobility platform?

NASA have deployed 4 rovers to Mars, and are working on the fifth. ESA is working on nr. 6. Sojourner: tiny, limited. Spirit and Opportunity (MER): much larger than Sojourner. No reuse possible. ...
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38 votes
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Why don't we send a rover to a pole of Mercury?

This question: Calculating the delta V budget from Earth to Mercury Gives the reason. Mercury is actually very difficult to reach directly due to its location deep inside the Sun's gravitational well. ...
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34 votes

Can either Opportunity or Curiosity explore the state of Spirit?

Not a chance. From NASA, here's the locations of everything that's landed on Mars (Well, NASA missions) Curiosity is kind of close to Spirit, but keep this in mind. The equatorial circumference is ...
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34 votes
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Could Mars Rovers be lighter or faster if they didn't have to be tested on Earth?

The video shows only tests within the clean room on smooth clean test floors. The vibration test at first should simulate the conditions during launch. Drive tests on a simulated Martian rough and ...
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34 votes

How were Perseverance's cables "cut" after touching down?

According to the official NASA press release, pyrotechnic guillotines were used: The footage ends with Perseverance’s aluminum wheels making contact with the surface at 1.61 mph (2.6 kilometers per ...
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33 votes
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Why are there so few lunar rovers?

That's many questions. Lunokhod 2 lasted for nearly 4 months and held the record for longest distance traversed by an off-Earth robot for over 41 years, until MER-B (Opportunity) beat that in mid 2014,...
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33 votes
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How did astronauts using rovers tell direction without compasses on the Moon?

The Lunar Roving Vehicle did have a (form of) compass. It was gyroscopic rather than magnetic, thus it needed calibration when first powered up using the sun angle as a reference. It's in the upper ...
32 votes
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Why did China land a rover on the moon?

The mission objectives are: The main scientific objective of CE-4 is to provide scientific data for lunar far side research, including: 1) general spatial environmental study of lunar far side;...
32 votes

How can electronics on board JWST survive the low operating temperature while it's difficult to survive lunar nights?

If surviving lunar nights are difficult to ensure the survival of the electronics, say on lunar rovers, in the low temperatures, The temperature itself is not the primary reason. Lunar nights are ...
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32 votes
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Could a Mars rover go to Phobos or Deimos instead?

No, for a lot of reasons. The Mars rovers slow down based on aerodynamics, heat shields, and parachutes. None of that is available on one of the Moons, meaning that the fuel requirements are much ...
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30 votes

Can either Opportunity or Curiosity explore the state of Spirit?

Opportunity is roughly 10,000 km away from Spirit in a straight line. At its top speed of 0.05 m/s (0.18 km/h), it would take approximately 2300 days to reach Spirit -- not that Opportunity can ...
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30 votes
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How did astronauts navigate the Lunar Roving Vehicle (LRV) over the surface of the Moon?

The navigation system used a combination of magnetic pickups in the wheels (to count how many turns each one has taken) and a directional gyro. This allowed both turn angles and distances travelled to ...
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29 votes
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How can electronics on board JWST survive the low operating temperature while it's difficult to survive lunar nights?

From Status of the JWST Sunshield and Spacecraft found in @Antzi 's answer: Most of the electronics is on the "hot side" but there needs to be some conventional electronics on the cold ...
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28 votes
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How are the Mars Rovers maintained?

There's very little opportunity to do maintenance on Mars. I could find an example of shaking the arm of Curiosity to get rid of dust. That's cleaning, and hence maintenance, for the purpose of ...
27 votes

Is Perseverance unable to move?

I'm quite sure it can move. The first roughly 9 days after landing it needs to get its bearings, look around, plan out a path, and most importantly, be reconfigured to operate on the ground. For ...
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26 votes

How can electronics on board JWST survive the low operating temperature while it's difficult to survive lunar nights?

Source: Me. I currently work as a systems engineer on JWST. JWST will operating from the 2nd Lagrange Point (aka L2), which is approximately 1.5 million km (or 930,000 miles) past the Earth in Sun-...
24 votes

Why aren't we sending quadcopters to mars?

An additional issue that needs to be addressed: such a drone would need to be completely autonomous, or at least have an autonomous controller (rover?) on the Mars surface. The drone in your example ...
24 votes

Why exactly do robots freeze? How could we engineer around it?

Purely based on an operational standpoint of semiconductive devices, equivalent resistances are considerably higher at low temperatures, and thus any calibrated circuit or component, including Rcomps, ...
23 votes
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How did the spirit rover land right way up after bouncing

Mars Pathfinder, Spirit, and Opportunity all could come to rest on any of four sides of the tetrahedral-shaped lander. Just by chance, Mars Pathfinder and Spirit landed with the base petal down. ...
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