9 ms·

This seems dramatic, but there is a ton of life left in the wheels. Some of my colleagues performed life testing on the wheels after we first discovered the cra

This seems dramatic, but there is a ton of life left in the wheels. Some of my colleagues performed life testing on the wheels after we first discovered the cracks and found the rover is capable of driving around on the titanium support struts even after the aluminum wheels have completely disintegrated. We've got a long way to go yet!

kahnpro 10y ago
If Kerbal Space Program taught be anything about space, it's that most problems can be solved with struts.
- JetDogRush 10y ago
  If only Curiosity were as fast as the KSP rovers... top speed is somewhere around 100 meters/hour, and usually more like 40!
  - TeMPOraL 10y ago
    Should have strapped an SRB on the rover. Reminds me; I wonder just how much ion engines are overpowered in KSP compared to their real-life equivalents. Or, put differently, if one could replicate a hovering Minmus rover I made in KSP (which used ion engines to stay afloat for a long time).
    - jerf 10y ago
      Minmus surface gravity is 0.491 m/s^2; current ion drives thrust with a couple hundred millinewtons, so I don't think a drive could even support itself against that level of gravity let alone with power and a ship attached. However, we currently design our ion drives for power-to-thrust efficiency and long-term effectiveness. I'm not sure what we could get if we designed them for maximal thrust. Especially since in real life, right now the answer to "Do you want a 'maximal thrust' ion drive?" is pretty much "Well, have you considered using... not an ion drive?", so I'm not sure I've ever seen a treatment of that question based on current tech.
      - creshal 10y ago
        > I'm not sure what we could get if we designed them for maximal thrust. Probably something with a worse specific impulse than a chemical engine.
      - Symmetry 10y ago
        The problem is less our ability to make the drives themselves have a high TWR (thrust to weight ratio) so much as that the power generation necessarily required to run them is very heavy. See here: http://hopefullyintersting.blogspot.com/2015/03/rockets-electric-propulsion.html http://hopefullyintersting.blogspot.com/2015/03/rockets-elec...
      - skykooler 10y ago
        The VASIMR engine is sort of that - an ion engine designed to be able to increase thrust when needed.
    - creshal 10y ago
      KSP: 4200s Isp, 2000 N thrust Real life: 2000-20000s Isp, 0.01-2.5 N thrust KSP's ion engines are hilariously overpowered in terms of thrust (and thrust-to-weight ratio) and power efficiency. It's a necessary change, however, since KSP is ill-suited for transfer burns several months long.
  - pavel_lishin 10y ago
    The flip side is that Curiosity has never, to my knowledge, flipped over and tumbled at near-escape-velocity, shedding solar panels and scientific instruments as it goes.
  - Declanomous 10y ago
    That really is slow. My brain interpreted that as 100 m/s, and then 40 m/s, and I read the sentence a few times trying to figure out if you meant that rovers go that fast in KSP before I figured out it said 100 m/hour.
- marcosdumay 10y ago
  It's a completely non-realistic game. It's lacking of duct tape is inexcusable.
  - zurp 10y ago
    Darth Bubba: "I find your lack of duct tape disturbing."
  - andygates 10y ago
    There's not a duct tape mod?
- oconnor663 10y ago
  The KSP subthread makes every space article twice as much fun :)
- jschwartzi 10y ago
  That's funny. It's taught me that if you make a rocket long enough, no amount of struts will prevent it from wobbling itself completely apart within 60 seconds of blast off.
  - vkou 10y ago
    Struts won't, but turning off automatic stability 'assistance' will!
londons_explore 10y ago
When they break though, I could imagine them getting tangled around things immobilizing the robot.
- JetDogRush 10y ago
  You're right - you can see the cable harnesses to the drive actuators in the original article. A major concern would be if a big flake bends inward and manages to sever those wires.
- deleted 10y ago
  [deleted]
valuearb 10y ago
They don't build 'em like they used to! They used to break within days or hours.
cr0sh 10y ago
> found the rover is capable of driving around on the titanium support struts Anyone who has watched enough of the COPS television show could have told ya that you can go quite far on just the rims. Heck, check out what some normal people do on /r/justrolledintotheshop...
tropo 10y ago
So, I don't get it. There are obvious issues here: Angular ribs cause stress points. Good CAD software should tell you this. Some metals are able to flex a small amount repeatedly, forever, without cracks. For other metals, "small" is just zero. Any flexing will eventually create cracks. Aluminum is a bad metal. Titanium is a good metal. Steel varies; unfortunately the good types tend to corrode. You have aluminum over titanium. Putting dissimilar metals in contact encourages corrosion. Mars is known to contain perchlorate salts. This is horrible for corrosion. Note that corrosion encourages crack propagation. Oh, and Mars has other stuff to not mix with aluminum: iron oxide and chlorides.
- anotheryou 10y ago
  They didn't test against pointy embedded rocks, because there where few of those where the small rovers had been. The main problem was the angle of the front and legs: if you drag a rolling suitcase up a curb it's all good, but when you try to push it up, you can generate forces much higher than the weight of the suitecase. Same happened to the rover.
anotheryou 10y ago
I read the biggest danger is something pointing up and cutting the exposed cable running to the central motor controller, potentially shorting it. That would stop all motors on the rover (wheels and a few more).

kahnpro 10y ago

If Kerbal Space Program taught be anything about space, it's that most problems can be solved with struts.

JetDogRush 10y ago
If only Curiosity were as fast as the KSP rovers... top speed is somewhere around 100 meters/hour, and usually more like 40!
- TeMPOraL 10y ago
  Should have strapped an SRB on the rover. Reminds me; I wonder just how much ion engines are overpowered in KSP compared to their real-life equivalents. Or, put differently, if one could replicate a hovering Minmus rover I made in KSP (which used ion engines to stay afloat for a long time).
  - jerf 10y ago
    Minmus surface gravity is 0.491 m/s^2; current ion drives thrust with a couple hundred millinewtons, so I don't think a drive could even support itself against that level of gravity let alone with power and a ship attached. However, we currently design our ion drives for power-to-thrust efficiency and long-term effectiveness. I'm not sure what we could get if we designed them for maximal thrust. Especially since in real life, right now the answer to "Do you want a 'maximal thrust' ion drive?" is pretty much "Well, have you considered using... not an ion drive?", so I'm not sure I've ever seen a treatment of that question based on current tech.
    - creshal 10y ago
      > I'm not sure what we could get if we designed them for maximal thrust. Probably something with a worse specific impulse than a chemical engine.
    - Symmetry 10y ago
      The problem is less our ability to make the drives themselves have a high TWR (thrust to weight ratio) so much as that the power generation necessarily required to run them is very heavy. See here: http://hopefullyintersting.blogspot.com/2015/03/rockets-electric-propulsion.html http://hopefullyintersting.blogspot.com/2015/03/rockets-elec...
    - skykooler 10y ago
      The VASIMR engine is sort of that - an ion engine designed to be able to increase thrust when needed.
  - creshal 10y ago
    KSP: 4200s Isp, 2000 N thrust Real life: 2000-20000s Isp, 0.01-2.5 N thrust KSP's ion engines are hilariously overpowered in terms of thrust (and thrust-to-weight ratio) and power efficiency. It's a necessary change, however, since KSP is ill-suited for transfer burns several months long.
- pavel_lishin 10y ago
  The flip side is that Curiosity has never, to my knowledge, flipped over and tumbled at near-escape-velocity, shedding solar panels and scientific instruments as it goes.
- Declanomous 10y ago
  That really is slow. My brain interpreted that as 100 m/s, and then 40 m/s, and I read the sentence a few times trying to figure out if you meant that rovers go that fast in KSP before I figured out it said 100 m/hour.
marcosdumay 10y ago
It's a completely non-realistic game. It's lacking of duct tape is inexcusable.
- zurp 10y ago
  Darth Bubba: "I find your lack of duct tape disturbing."
- andygates 10y ago
  There's not a duct tape mod?
oconnor663 10y ago
The KSP subthread makes every space article twice as much fun :)
jschwartzi 10y ago
That's funny. It's taught me that if you make a rocket long enough, no amount of struts will prevent it from wobbling itself completely apart within 60 seconds of blast off.
- vkou 10y ago
  Struts won't, but turning off automatic stability 'assistance' will!

londons_explore 10y ago

When they break though, I could imagine them getting tangled around things immobilizing the robot.

JetDogRush 10y ago
You're right - you can see the cable harnesses to the drive actuators in the original article. A major concern would be if a big flake bends inward and manages to sever those wires.
deleted 10y ago
[deleted]

valuearb 10y ago

They don't build 'em like they used to! They used to break within days or hours.

cr0sh 10y ago

> found the rover is capable of driving around on the titanium support struts Anyone who has watched enough of the COPS television show could have told ya that you can go quite far on just the rims. Heck, check out what some normal people do on /r/justrolledintotheshop...

tropo 10y ago

So, I don't get it. There are obvious issues here: Angular ribs cause stress points. Good CAD software should tell you this. Some metals are able to flex a small amount repeatedly, forever, without cracks. For other metals, "small" is just zero. Any flexing will eventually create cracks. Aluminum is a bad metal. Titanium is a good metal. Steel varies; unfortunately the good types tend to corrode. You have aluminum over titanium. Putting dissimilar metals in contact encourages corrosion. Mars is known to contain perchlorate salts. This is horrible for corrosion. Note that corrosion encourages crack propagation. Oh, and Mars has other stuff to not mix with aluminum: iron oxide and chlorides.

anotheryou 10y ago
They didn't test against pointy embedded rocks, because there where few of those where the small rovers had been. The main problem was the angle of the front and legs: if you drag a rolling suitcase up a curb it's all good, but when you try to push it up, you can generate forces much higher than the weight of the suitecase. Same happened to the rover.

anotheryou 10y ago

I read the biggest danger is something pointing up and cutting the exposed cable running to the central motor controller, potentially shorting it. That would stop all motors on the rover (wheels and a few more).