JPL's Plan for the Next Mars Helicopter • Hacker News Board

Re: JPL's Plan for the Next Mars Helicopter

#71

Post by ncmncm » Wed, Aug 11, 2021, 2:29 AM UTC

Robotbeat wrote: post #63

dogma1138 wrote: post #58

Earlier quoted context omitted.

It’s not about the math it’s about the engineering, NASA did the maths and a 40m diameter evacuated airship can carry a substantial payload on Mars, we however have no real clue on how to build it from an engineering perspective. If you would’ve asked people 10 years ago about flying helicopters on Mars plenty of them would say it’s not possible not because the math doesn’t work out, but because of what requirements…

Fine, engineering it is. And 10 years ago, regardless of what random people on the Internet would've said, we still had the technology to do a Mars helicopter (although the optical navigation has improved and become more lightweight, that could've been offloaded to the rover). It has been studied for decades and we've had good enough solar, batteries, and motors 10 years ago. A zeppelin could in principle work on Mar…

Batteries are better now than 10 years ago. Motors are better than 10 years ago. Solar is better than 10 years ago. Computers are better than 10 years ago. Each is not a huge amount better, but the improvements multiply out.

Re: JPL's Plan for the Next Mars Helicopter

#72

Post by toiletaccount » Wed, Aug 11, 2021, 2:40 AM UTC

jbay808 wrote: post #49

dogma1138 wrote: post #32

Earlier quoted context omitted.

I was thinking about a rigid body vacuum airship, landing would be easy because all you need to do is lose the vacuum which can be done with a valve and cost no power. Taking off again can be done over days so you can power it with solar panels if you can’t fit an RTG. I honestly don’t think winds would be that much of an issue they won’t be strong enough to structurally damage the airship they’ll blow it off sure bu…

I'm not aware of any vacuum container that is strong enough to resist buckling while being light enough to be buoyant.

Steel would work on Earth.

Re: JPL's Plan for the Next Mars Helicopter

#73

Post by snowycat » Wed, Aug 11, 2021, 2:40 AM UTC

That solar panel on the top seems awfully small to me. If you look at the solar panel on the helicopter that's already on mars, its almost 3 times bigger than the body. This just looks tiny in comparison.

Re: JPL's Plan for the Next Mars Helicopter

#74

Post by rtkwe » Wed, Aug 11, 2021, 2:42 AM UTC

rtkwe wrote: post #45

dogma1138 wrote: post #30

Earlier quoted context omitted.

The weather isn’t that of an issue due to the thin atmosphere. You can land an airship by compressing the lifting gas into a liquid. If you can get enough power reserve at least to do that. The main issue would be the size of the balloon but honestly if we can make some origami rigid airframe a vacuum airship might actually work. At that point controlling buoyancy is also less of an issue from a power perspective sin…

In general trying to create a vacuum airship is a loosing game because you have to add so much support to prevent it from collapsing that you can't win the race between volume and weight to achieve buoyancy. The thinner atmosphere is a bonus to decreasing the force for a given volume but you simultaneously have to increase the size of the 'balloon' since it's displacing less air for every unit of volume so it has to…

I think I missed a couple things in my initial calculations, like the reduced gravity of Mars, so the number is ~5%. Idk if that brings it back into the realm of possibility though.

Even given the ability to make it you'd likely have issues with the process of getting it there if we're not assembling it in situ.

Re: JPL's Plan for the Next Mars Helicopter

#75

Post by ncmncm » Wed, Aug 11, 2021, 2:44 AM UTC

mhh__ wrote: post #5

srcmap wrote: post #3

Wonder if it is practical to design Helicopter with nuclear battery similar to the rover....

Plutonium is really heavy, if you were to do that it strikes me that you'd be better off having some kind of wireless charging device which the helicopter lands on (But at that point why not solar power). You'd probably already need some batteries anyway as I'm guessing that the transient spikes in power usage would probably exceed any RTG you could fit in a helicopter anyway.

Probably you would use strontium-90, instead, if weight was important. Strontium is 7.5 times less dense than plutonium.

Strontium-90 produces 0.95W/g, where Pu-238 produces only 0.57 W/g. So, it takes only 3/5 as much, by weight, to produce the same heat as a Pu-238 RTG, although it takes 4.5x as much room. Room is relatively cheap on spacecraft, vs. mass.

This makes me wonder why they use Pu-238 RTGs in spacecraft at all. Maybe because it lasts a bit longer?

Re: JPL's Plan for the Next Mars Helicopter

#76

Post by Robotbeat » Wed, Aug 11, 2021, 2:54 AM UTC

ncmncm wrote: post #71

Robotbeat wrote: post #63

Earlier quoted context omitted.

Fine, engineering it is. And 10 years ago, regardless of what random people on the Internet would've said, we still had the technology to do a Mars helicopter (although the optical navigation has improved and become more lightweight, that could've been offloaded to the rover). It has been studied for decades and we've had good enough solar, batteries, and motors 10 years ago. A zeppelin could in principle work on Mar…

Batteries are better now than 10 years ago. Motors are better than 10 years ago. Solar is better than 10 years ago. Computers are better than 10 years ago. Each is not a huge amount better, but the improvements multiply out.

Not more than about 5-10% (at least at state of the art). Computers are the biggest argument, but again that's off-loadable to the rover. Again, if anyone said 10 years ago that a helicopter on Mars was not realistic, then they didn't know what they were talking about (it's funny how people who style themselves skeptics will learn like 5 facts about some place and then crown themselves an expert). I explored a similar but more advanced concept professionally about ~5 years ago.

Re: JPL's Plan for the Next Mars Helicopter

#77

Post by jasonwatkinspdx » Wed, Aug 11, 2021, 3:26 AM UTC

wongarsu wrote: post #27

gambiting wrote: post #10

Earlier quoted context omitted.

Earth also doesn't have any nuclear powered rovers driving on the surface and yet Mars does. Might have something to do with the fact that the risk to humans on Mars is slightly lower than on Earth,no?

French EVs are over 70% nuclear powered. We just keep the nuclear generators stationary and use battery buffers in the car to save weight. You might argue it's about risk, but that didn't seem like such a huge deal when we tried to make nuclear cars and planes back in the 50s. RTGs are just incredibly inefficient, and properly shielded fission reactors are incredibly heavy.

Yeah, the 1950s involved serious consideration of some truly horrific nuclear flight concepts, so I wouldn't be so dismissive of risk as a factor. Not like airliner crashes are awesome, but they don't drop a reactor core on whatever they crash into. Not to mention proliferation concerns, operator staffing requirements, security staffing requirements. There's very straightforward reasons nuclear powered flight on earth never went past the earliest exploration of a couple prototypes. Russia is working on a nuclear powered cruise missile and has already had one serious mishap with it.

Re: JPL's Plan for the Next Mars Helicopter

#78

Post by hamburgerwah » Wed, Aug 11, 2021, 3:28 AM UTC

This is fan fiction. Nasa as nasa will never reach mars again. China yes, Spacex yes, but not nasa.

Re: JPL's Plan for the Next Mars Helicopter

#79

Post by akiselev » Wed, Aug 11, 2021, 3:37 AM UTC

BotJunkie wrote: post #53

JoeAltmaier wrote: post #42

Lots in here, taking me time to unpack. Kind of blue-sky - 30kG is heavy, so maybe its all moot - who's going to dedicate that much mass to this project. Any geology it does, will be contaminated by rotor wash scrubbing the surface material when it lands. Is that an issue? Maybe its a benefit. Can it really react to sample inaccessible places? What is the response time between capturing an image of a face, and gettin…

I interviewed Bob and wrote this article, so I can answer a few of these. I think JPL's idea is that MSH would be a dedicated helicopter mission, rather than piggybacking on some other mission, so it wouldn't be eating up the mass budget of another lander or rover. Similar to Ingenuity, the flights would be autonomous but the science wouldn't be. MSH would fly up to a cliff face (or whatever), take pictures, land, as…

> MSH would be able to communicate with orbit directly and would not need rover or lander support.

Does that mean it wouldn't be powered by an RTG like the last few missions? Or do you just mean that the MSH will have its own comms independent of a supporting rover/lander?

Re: JPL's Plan for the Next Mars Helicopter

#80

Post by DamnInteresting » Wed, Aug 11, 2021, 3:44 AM UTC

ekola wrote: post #62

Is there a reason they don't send Boston dynamics robots?

It was in the news yesterday that NASA is working with Boston Dynamics to potentially explore caves on Mars with walking robots: https://www.cbsnews.com/news/nasa-human-like-robots-boston-d...