Hot answers tagged

102

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 involve event-driven failures, such as failures induced by landing shocks, long engine burns, atmospheric entry stresses, etc. When someone (a government, usually) ...


86

Mars' temperature range is rather large, with temperatures down to -107 °C measured by the Viking landers. This is below rubber's glass transition temperature of -70 °C, below which rubber becomes brittle. So you can't use rubber. A rubber tire is heavy. The tread of a normal road tire is more than 1 cm thick, off-road tires are thicker and heavier. It also ...


67

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: 1.2 kg/m3, so Mars' atmosphere has 1% of the density of Earth's. Lift is proportional to air density, so a wing will have 1% of the lift on Mars. Gravity is 38%...


66

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 like to buy one, they sell them here. There's a description of the cutters used by MSL (Curiosity) here with some nice pictures of it in action on page 12.


54

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 sun. Eclipses are defined as only occurring if the entire sun is blocked, or at least the vast majority. Phobos blocks out only about 60% of the sun at most. ...


54

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 memory (you lose one bank), but as the rover was avoiding flash memory entirely, you have a net gain by being able to reenable it. https://www.jpl.nasa.gov/news/...


49

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 the rovers, so the systems were designed and tested to assure full capability through the entire 90 sols. The first thing expected to take a rover below full ...


48

To first answer the question ad litteram, NASA has so far successfully landed four stationary labs on Mars (Mars landing dates in parentheses): Viking Lander 1 (July 20, 1976), Viking Lander 2 (September 3, 1976), Mars Pathfinder (July 4, 1997) and Phoenix Mars Lander (May 25, 2008). Here are their landing sites on a map of Mars generated with Mars ...


47

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 completely crippled. Long answer: The Mars rovers all use the same design, called the Rocker-Bogie. This is a special design which allows the rover to ...


45

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 under constant acceleration is $$d = \frac{v^2}{2a}$$ from which we can quickly solve for the acceleration to be $$a = \frac{v^2}{2d}$$ Even with 10 meters of ...


43

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. Spirit and Opportunity were identical. Curiosity: much larger than MER. No reuse possible - but it does use technologies proven on MER, like the suspension design. ...


40

Yes, it is a mosaic made of 55 images from the MAHLI camera on the arm. The arm was deliberately removed from the images where bits of it showed up. See this description, including a video of how it was done. The arm motions were very carefully planned to cover the rover and surface around it by changing the angle of the camera, but not the absolute ...


38

I think you may be confused about the nature of the problem the skycrane is trying to solve (however I also may be confused!). The rover, being a rover, does not need to stay at the landing site. If the landing site has a lot of dust blown off it, well, they can go somewhere else where the dust has not been blown off the surface. As the other answer says ...


34

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 about 13,000 miles. I'd guess the distance is over 1000 miles, far further than any rover has gone before, or is likely to ever go. There's just much more ...


34

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 dirty surface on Earth (see JPL Mars Yard) are not done with the version built for the Mars surface. The flight-ready version is built in a clean room and only ...


33

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, so I wouldn't really say that lunar rovers don't last. It eventually scooped up some regolith dust with its open lid that was also its solar panel, and as it ...


33

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 left of the console here: According to Wikipedia: Navigation was based on continuously recording direction and distance through use of a directional gyro and ...


32

Tracks are heavy, high-friction, and primarily useful in soft/muddy/slippery terrain where the weight distribution is essential to prevent sinking and slipping. They take much more energy to move than wheels, and while on Earth-bound robots that's not so much of a problem, on a lander this is to be or not to be of the mission. They weigh quite a bit. I can'...


32

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;2) general research on the surface, shallow layer and deep layer of lunar far side;3) detection of low frequency radio on lunar far side using Low Frequency ...


32

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 hour), and then pyrotechnically fired blades sever the cables connecting it to the still-hovering descent stage. The descent stage then climbs and accelerates ...


30

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 maintain that speed. Between limited electrical power, needing to slow down to navigate, and being unable to drive at night, driving is much slower. Based on the ...


30

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 be calculated on board. See this section of the manual, section 1.3.7 "Drive Control Electronics" (page 5 onwards.) Also page 18 of the above link shows the ...


28

Temperature shifts Earth's temperature swings from extreme to extreme is quite moderate. That is, coldest is generally around -40C and warmest is around 40-45C. The Moon has two weeks in blazing hot sunlight, much hotter (depending on your reflectance) but well over 100C, and two weeks of much much colder. Not quite absolute zero (-273C), but pretty cold ...


28

Because of the nature of radioactive decay, Curiosity is going to get a whole lot more than 2 years out of its power source. Curiosity will be getting enough power to keep active for a bare minimum of 14 years (see Specifications> Power Source), though the amount of power it has will steadily decrease over time (from 125 Watts initially to 100 Watts after 14 ...


28

Resilience: There is no way that an inflatable tyre of any kind can be used for remote missions, because they are incredibly unreliable. Think about car or bike tyres here on Earth, where we have a fairly small range of temperatures. They puncture easily, they burst, they lose pressure, the rubber degrades etc. When they have a puncture, fixing them is ...


27

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 avoiding cross contamination of samples. A specialised dust cleaning device (a "wiper") did not end up going to Mars. I could find no evidence of the Dust ...


26

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 comparison, Curiosity landed on August 6th, and didn't start moving until August 15. Perseverance landed on Feb 18, it has only been 11 days, I wouldn't worry too ...


25

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 difficult to survive because you have 14 days of darkness. If you want to design a solar-powered rover that can store enough energy to stay warm for 14 days, ...


24

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 is piloted remotely, but the signal delay between Earth and Mars varies between 4 and 24 minutes (one way), depending on their relative orbital locations. At ...


23

Let's compare with 4G, for which I could find some numbers: Your cell phone is transmitting with speeds of up to 50MBps with a maximum of 1 Watt (can be as low as a few µW!), using a tiny antenna that is often obscured by water bags (human flesh and organs), rocks, buildings, trees, etc. Let's compare this with Mars Express, for example: its maximum ...


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