5 ms·

Not a rocket scientist, but I really wonder about the cost-effectiveness of this approach. Is it really more effective to do testing in prod (on another freakin

Not a rocket scientist, but I really wonder about the cost-effectiveness of this approach. Is it really more effective to do testing in prod (on another freaking planet) than to more thoroughly emulate the Martian atmosphere here first?

wongarsu 8y ago
Emulating the martian atmosphere is easy enough, but the helicopter can't fly with martian atmosphere and earth gravity. And we don't really have good, cost effective ways to simulate lower gravity (at least none that work for flying drones). That really limits how much testing you can do on earth outside testing the subassemblies in isolation.
- gpm 8y ago
  For anyone else wondering: Earth gravity is 9.81 m/s^2, mars gravity is 3.72 m/s^2. To emulate this on earth you would have to be on a aircraft accelerating downwards at 6.09 m/s^2. Doing so starting at 0 vertical velocity for 90 seconds would mean loosing 24664.5 meters of altitude, ending at 548.1 m/s. The speed of sound is 340 m/s - so the only reasonable flight profiles (i.e. subsonic) probably involves starting out with ~274m/s vertical velocity, and doing a parabola where you get back to your starting point. I'm not sure if you could actually maintain the necessary acceleration, and I imagine it would be difficult to maintain an atmosphere simultaneously, but it might be doable.
  - jandrese 8y ago
    Maybe you have a partial vacuum chamber and the drone suspended by a winch that is tuned to reduce its effective weight to what it would weigh on Mars. A fairly complicated test setup, but cheaper than flying out to the red planet.
    - CodeWriter23 8y ago
      Unless you have a mission scheduled that can take a few more kilos of payload as is the case here.
CodeWriter23 8y ago
It's more a risk assessment problem than a cost effectiveness problem. They're not going to get funded for a 50-100kg fully-instrumented UAV (and the boosters and spacecraft to get it to Mars) until they prove the concept first. The brass is willing to spend a half million on a mission that piggybacks on and minimally impacts a currently-funded mission to find out if UAVs are feasible. The reality is Opportunity has covered ~45 linear kilometers in its 14 year lifespan. They hope to cover hundreds of square kilometers with the UAV approach.

wongarsu 8y ago

Emulating the martian atmosphere is easy enough, but the helicopter can't fly with martian atmosphere and earth gravity. And we don't really have good, cost effective ways to simulate lower gravity (at least none that work for flying drones). That really limits how much testing you can do on earth outside testing the subassemblies in isolation.

gpm 8y ago
For anyone else wondering: Earth gravity is 9.81 m/s^2, mars gravity is 3.72 m/s^2. To emulate this on earth you would have to be on a aircraft accelerating downwards at 6.09 m/s^2. Doing so starting at 0 vertical velocity for 90 seconds would mean loosing 24664.5 meters of altitude, ending at 548.1 m/s. The speed of sound is 340 m/s - so the only reasonable flight profiles (i.e. subsonic) probably involves starting out with ~274m/s vertical velocity, and doing a parabola where you get back to your starting point. I'm not sure if you could actually maintain the necessary acceleration, and I imagine it would be difficult to maintain an atmosphere simultaneously, but it might be doable.
- jandrese 8y ago
  Maybe you have a partial vacuum chamber and the drone suspended by a winch that is tuned to reduce its effective weight to what it would weigh on Mars. A fairly complicated test setup, but cheaper than flying out to the red planet.
  - CodeWriter23 8y ago
    Unless you have a mission scheduled that can take a few more kilos of payload as is the case here.

CodeWriter23 8y ago

It's more a risk assessment problem than a cost effectiveness problem. They're not going to get funded for a 50-100kg fully-instrumented UAV (and the boosters and spacecraft to get it to Mars) until they prove the concept first. The brass is willing to spend a half million on a mission that piggybacks on and minimally impacts a currently-funded mission to find out if UAVs are feasible. The reality is Opportunity has covered ~45 linear kilometers in its 14 year lifespan. They hope to cover hundreds of square kilometers with the UAV approach.