back to article NASA reveals the new wavy Martian wheels it thinks can crush the red planet

NASA has revealed the wheels it’s just bolted onto the Perseverance Rover, the new Mars assault robot it plans to send to the red planet in July as part of the Mars 2020 mission. Wheels matter because NASA’s Curiosity rover has had trouble keeping a grip on Mars. As we reported in 2017, Curiosity has been popping unintentional …

  1. redpawn Silver badge

    Air traffic

    Until the pandemic we were plagued with copter noise here. No evidence of active pandemic on Mars at this time so extra care should be taken during flight operations.

    1. John Brown (no body) Silver badge

      Re: Air traffic

      I was just wondering of their might be space in the lander for a PARIS 2.0, Paper Aeroplane Released Into Syrtis [Major]

    2. JCitizen Bronze badge
      Black Helicopters

      Re: Air traffic

      Where's your black helicopter badge?

  2. Captain Scarlet Silver badge
    Alien

    Annoying Drones

    Its bad enough with Mysteron saucers let alone other drones!

  3. Blofeld's Cat Silver badge
    Coat

    Don't stand so close to me ...

    "... The ‘copter is equipped with cameras, too, so hopefully we’ll get some fabulous footage! ..."

    I expect the Space Police will also use it to check that the Martians are social-distancing correctly.

    My coat? It's the one with the Illudium Q-36 Explosive Space Modulator in a pocket.

  4. Chris G Silver badge

    Do NASA keep all of their tyre development inhouse or do they talk to others?

    Tyre manufacturers spend huge amounts of money developing tyre compounds and treads for different applications and must have huge amounts of data about terrain and tread/durability.

    1. Pascal Monett Silver badge

      I doubt that there are many tire manufacturers that make tires for surfaces other than roads. There may be some models that are special for all-terrain models, but all tires made on Earth have one thing in common : an atmosphere around them.

      Rubber tires in space would be a catastrophe. I saw a documentary on the lunar landing, where it was explained that the tires for the lunar rover were, in fact, a wire mesh that behaved basically like a normal tire.

      I wonder why they didn't use that concept ? It's not like NASA didn't know about it, so what reason did they have to reinvent another wheel type ?

      1. Wellyboot Silver badge

        @Chris G, I agree with your point on tread design, that should be reasonably reliable once the exact nature of the surface is known. (which we don't know until we go and look)

        Within the tyre industry there's no data about tyres working at the temperature & terrain combination found on Mars (our mid arctic winter lowest temp is about the annual average up there) and precious little where tyre/wheel all up weight is a critical issue regardless of the ambient temp.

        The big problem with rovers is that NASA want the wheels to work for years with as little performance degredation as possible, I think the moon rover wheels were built for absolute minimum weight and only good for a few dozen miles of life.

      2. Jon 37

        When building payloads, mass reduction is really important. You have to get the thing as light as possible. This means you can't over-engineer things - for example the ladder on the side of the lunar lander was only going to be used on the moon, which has less gravity than earth, so they made the ladder too weak to be used in Earth gravity, but strong enough to be used on the moon. Bearing that in mind, there are a lot of differences between the missions:

        * The lunar rover had to carry a couple of astronauts in EVA suits; that's a lot of weight. I believe the current mars rovers are lighter, so they can use weaker, lighter wheels.

        * The lunar rover only had to last for a week or so of use; the mars rovers have to last years of constant use.

        * The lunar rover drove on the moon; the mars rovers drive on Mars which has a different rock composition.

        * The lunar rover was built many years ago; more modern materials are available now, and design tools (especially computer simulation) have advanced a lot, so modern designs can have less mass.

        * The mars rovers are 6-wheel, and are designed to drive even if one wheel siezes up, to allow the mission to continue even if a motor fails. The lunar rover was 4-wheel.

      3. ColonelClaw

        I don't know if it's important, but as well as all the points mentioned here already, I notice that Mars is much larger than the Moon, and must therefore have considerably more gravity. Add to that the 899kg weight of the rover itself (nuclear-powered craft can't be lightweight) vs the lightweight 209kg moon rover, and we're dealing with quite a different proposition.

      4. Pascal Monett Silver badge

        You all made very good points. Thank you for bringing them to my attention.

      5. macjules Silver badge

        "It's not like NASA didn't know about it, so what reason did they have to reinvent another wheel type?"

        You just expressed government joined-up thinking in one line.

      6. Gustavo Fring

        no durability required

        The wheels on the moon rover only had to last a couple of days .. so liteness and usability were the main

      7. Brian O'Byrne

        There is also the question of the sand composition.

        Lunar regolith consists of sharp granules of various sizes. Martian sand is subject to weathering, so it is smaller, rounded granules. Martian sand is therefore more free-flowing so its interaction with wire mesh wheels would be very different than the lunar surface.

    2. phuzz Silver badge

      What they're referring to as a 'tyre' is a solid aluminium wheel (with titanium spokes). There's no rubber involved.

      JPL have built the last three rovers on Mars, so I'd say they're the leading experts on driving there.

      1. The Nazz Silver badge

        The spaces between the 48 fins look uniform across the width. I'm certainly no wheel designer but i would have thought some variability in the gaps would've helped. Sometimes a 10mm gap, other times a 20mm gap etc. At worst, it would make more abstract patterns in the dust.

  5. Neil Barnes Silver badge

    good luck finding someone to fit it!

    Sounds like a job for the AA!

    https://www.youtube.com/watch?v=fRCKxseKanA

  6. JDX Gold badge

    I wouldn't have guessed you COULD fly a 'copter in the thin atmosphere of MArs, even with reduced gravity. Is it as marginal as I imagine or not that big a deal?

    Maybe the newer rover can be built to perform a pit-stop on the old one.

    1. Wellyboot Silver badge
      Black Helicopters

      Very marginal, the 'copter is tiny. Aero physics are the same but some of the numbers change a lot. As a first attempt I'd expect NASA to be happy if it made one sucessful flight before blowing away in a light breeze.

      If anyone knows the design rotor size & RPM please do tell.

      Edit: found it. :)

      https://www.nasa.gov/press-release/mars-helicopter-to-fly-on-nasa-s-next-red-planet-rover-mission

    2. Anonymous Coward
      Anonymous Coward

      Mars's atmospheric pressure is 1% of Earth's: https://en.wikipedia.org/wiki/Atmosphere_of_Mars

      But it's gravity is a bit under 1/2 of Earth's: https://en.wikipedia.org/wiki/Gravity_of_Mars

      I'm no rocket scientist by a long way, but I suspect that enough lift can be created if the propellers spin faster. And this can be tested on Earth in a partial vacuum chamber, which is probably the first thing NASA tried before committing to the project.

      1. TeeCee Gold badge

        Hmm. Just remember that, in the thinner atmosphere, your rotor tips will go supersonic at lower speeds and that having your rotors go supersonic is a Very Bad Thing Indeed.

        Larger rotors is probably the way to go rather than faster ones.

        1. Phil O'Sophical Silver badge

          NASA claim the 'copter rotors will spin at 3000RPM, by my calculations that gives them up to 1.5m diameter rotor disk before the tips go supersonic.

        2. Olius

          What's so bad/special about rotors going supersonic?

          1. A K Stiles Silver badge
            Coat

            If the tips go faster than the speed of sound but the roots don't ('cos they do a shorter distance in the same time) then you essentially end up with a shock compression part way down the blade, which is 'a bad thing' structurally and stability speaking.

            Even if you could get the entire blade to be supersonic (instantly, no accelerating otherwise see point 1), you then run into issues if you add any velocity to the vehicle as the receding blade may drop below the speed of sound when you combine the velocity of the blade with the velocity of the vehicle, causing the repeated transition shocks from point 1.

            1. John Brown (no body) Silver badge

              I'm sure this is the sort thing the clever people at NASA have already tested for, but I wonder just how much stress a sonic boom part way down a rotor blade at 1% standard earth atmospheric pressure is?

              1. Alan Brown Silver badge

                "I wonder just how much stress a sonic boom part way down a rotor blade at 1% standard earth atmospheric pressure is?"

                You don't have to look far. X15 (sometimes unintentionally) tested this stuff 50+ years ago.

                Amongst other things the heating effects are harder to get rid of due to the less dense atmosphere not having many molecules to dump energy into.

  7. Mr Army

    I recognise that tread pattern,

    I had a Tamiya Sand Scorcher 1/10th scale RC car (their first foray into proper suspension) in the early 80s. Tamiya had remote controlled sand crossing vehicle tyres sorted 40 years ago.

    Link to pic of box art.

    https://ibb.co/MPPRKMQ

    1. KarMann Bronze badge
      Go

      If I recall correctly, I think they're called sand paddles in that context.

      Wikipedia basically backs up my dim memory.

    2. Paul 75

      I had that same Sand Scorcher, and it was brilliant! Wanted to get another for my own kids, but they are pretty expensive; there was a remake of it in 2010 apparently.

      We used to have to build practically the whole thing, and that was a big part of the fun, what I don't like nowadays is that it seems to be almost totally ready built - I'm sure somebody could correct me though?

      1. John Brown (no body) Silver badge

        It's marketing. Only certain people are prepared to actually build their RC models. Many, many more just want to open the box, take it out and play.

        Having said that, I know a guy makes model steam engines. He starts with sheets of metal and small billets and lots of tools and heat. Anything else isn't "proper" modelling :-)

        1. ICL1900-G3

          Steam engines

          My dad! Bless him.

  8. Marty McFly
    Alien

    Robot planet

    Just for clarity.... At this point in time, to the sum of humanity's knowledge about Mars, it is a planet entirely populated by robots.

    Dare I add.... As older robots cease to function, newer updated robots continue to be sent from a neighboring planet to replenish the population.

    1. phuzz Silver badge
      Alien

      Re: Robot planet

      There's also amanfrommars1, who may, or may not be a robot.

  9. RobThBay

    Mach?

    Hmm... mach 1.7.

    Is that mach 1.7 in the Martian or Earth atmosphere?

    1. Anonymous Coward
      Anonymous Coward

      Re: Mach?

      Mach number relates to the local speed of sound. It doesn't correspond to any particular speed even on Earth. So for a flight on Mars, the only atmosphere that's relevant is the Martian one.

  10. hairydog

    The wheels look very flimsy to me.

    OK, the weight of the rover is only a fraction of what it is on Earth, but its mass is just as high. If it strikes a lump in the ground as it drives along, it's the mass, not the weight, that punches against the wheels. I guess they're tougher than they look. Well, I hope so!

    1. zuckzuckgo Bronze badge

      I think inertia is the issue. So you can just drive slower on rough terrain to reduce stress on wheels. Surely speed limits are radar enforced on Mars.

      1. Alan Brown Silver badge

        "So you can just drive slower on rough terrain to reduce stress on wheels. "

        I doubt you can go much slower than the existing robots. A garden snail would give them a run for their money.

  11. Tom 7 Silver badge

    You dont want to go across a slope in those new wheels

    Ask any caterpillar driver. You can spot one who has side slipped in one several years later!

    1. erikscott

      Re: You dont want to go across a slope in those new wheels

      I was thinking just that. The Curiosity wheel reminds me of a "Bar Turf" tire - an "R14" in agricultural terms. Looks like they're going back to sand paddles. As far as unequal spacing, Curiosity's wheels have some lines milled into them that spell "JPL" in morse code. The wheel motors have position encoders, but the lines can be seen with the cameras to help calculate wheel slippage. https://www.nasa.gov/mission_pages/msl/news/msl20120829f.html

      There's a good article on the Spirit and Opportunity suspension, motor, steering, and wheel design. It's paywalled (IEEE), but if you can get to it look for "Mars exploration rover mobility development" in google scholar. The wheels are milled from a billet of 7075 aluminum.

POST COMMENT House rules

Not a member of The Register? Create a new account here.

  • Enter your comment

  • Add an icon

Anonymous cowards cannot choose their icon

Biting the hand that feeds IT © 1998–2020