Hacker News Reader

Comment by crispyambulance | Hacker News Reader

It's really cool. I am amazed they're able to fly a helicopter in what is effectively almost a vacuum to us.

But what about power? How long can a 4lb drone fly? a few minutes?

Presumably there's a way to recharge this thing, but that would require a base-station with solar or nuclear power source. I am not understanding how this drone would be effective in a mission!

View on HN

Tons of technical details on the helicopter here [0]

For power in particular, charged by solar panels (the things above the rotor), worst case end-of-life flight time is estimated at 90s, depending on season it might take more than 1 day to reach full charge.

Edit: And the two numbers for range I can find in that document suggest 300m flight range, and "outbound sorties" of length 100m (suggesting always flying back to the rover?).

[0] https://rotorcraft.arc.nasa.gov/Publications/files/Balaram_A...

Something I don't think people appreciate is how slowly things move on mars in general. Curiosity, a huge success, has moved a total of 20.38 kilometers as of two days ago. That's after 2359 martian days.

It's hard for me to imagine a drone not being effective!

https://mars.nasa.gov/msl/mission/whereistherovernow/?ImageI...

To be fair, though, a lot of that is by choice. What advantage is there in moving quickly and taking on all of the associated risks when there's lots to see and do while moving slowly and spending extended periods of time parked at specifically interesting sites?

By having alternate crafts that can move quickly, we might be able to better guesstimate if it's worth the time of the slow rover to change course and investigate a blip on the map. Alternatively, fast craft could fly around and drop beacons on areas of interest to be investigated at a later time. Beacons that could be sensor probes returning data of interest.

> but that would require a base-station with solar or nuclear power source. I am not understanding how this drone would be effective in a mission!

We have a very good track record of sending large rovers with solar and nuclear power sources to mars. A rover would make a good mobile base station, with a helicopter for collecting samples from various places to bring to the rover's onboard lab.

I spoke to one of the project engineers at JPL’s Open House last year. He said the only planned mission for this unit is proof of concept. If they can make it fly on Mars they will be sending a bigger one with larger batteries and more instrumentation on a later mission. He said their constraint is his team has received a small allocation of antenna time during the overall mission. The 2020 Rover ops get priority.

I imagine based on past missions, probably after all objectives are achieved and time on the array is available, they’ll get creative and push the chopper a little more.

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?

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.

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.

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.

Unless you have a mission scheduled that can take a few more kilos of payload as is the case here.

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.

Reply on news.ycombinator.com