Why don't they add a drone to the Mars rovers so that they

>>8011397
the difference in air density makes a much larger impact than you think. mars surface air density = earth density at 35km

gravity is 3.7 m/s^2 vs 9.81. the air density at 35km is 0.0016 kg/m^3. sea level is 1.225.

not even close.

>>8011476
For starters it's actually 0.016 kg/m^3 and secondly the weight a propeller can lift depends on the cube of gravity but is only linearly proprotional to air density so 1/3 the gravity will increase payload by a factor of 27 while the air density drops it by a factor of 75 therefore it will more or less halve.

>>8011476
So if a drone make it 15 minutes on Earth it will last 7 minutes on Mars, this is enough to take a quick peek over a small hill.

landing could be dangerous and damage the rover

http://www.nasa.gov/jpl/helicopter-could-be-scout-for-mars-rovers

What about using balloons?

>>8011552
seriously goyim? It's like you desperately searched for a reason to dismiss the idea just to avoid saying it's good and it is good because
>>8011560
which I didn't know about thanks for posting.
Seems they plan on using a monorotor, I was thinking a quad but yeah that will work great too.

The MRO can already get images with resolutions down to less than a meter. There's probably very little you would get from a drone that couldn't be gathered from the orbiter.

>>8011631
An aerial camera would get a lot better than meter resolution. Do you really think meter resolution is good enough? Funny how /sci/ continues to trash an idea even after it has transpired that NASA is working on it.

>>8011537
No, that's not at all correct. It wouldn't even be able to generate enough lift to get airborne, because the martian atmosphere is so thin it's nearly a vacuum by our standards.

>>8011668
I just explained mathematically why it will fly, you claim it's wrong with what maths exactly?

>>8012301
Your claim that the weight a propeller can lift is proportional to the cube of gravity is obviously rubbish.

>>8012463
No it's true, you need to learn basic mechanics

Rigid hot helium airship.

Give it a RTG. The waste heat is used to heat the ballon and make the craft neutrally buoyant.

RTG and Photovoltaic cells on the helium ballon power drive fans, sensors, comms.

>>8012563
"No it's true" is pretty far from compelling.

In order to stay airborne, a drone will need to produce as much thrust as it weighs. The propeller's thrust is proportional to the of the density of the medium it's in. Mars's atmosphere is a tiny fraction of that of Earth's, but it's gravity is still one third.

To stay airborne on Mars would be incredibly difficult.

>>8012565
>Rigid hot helium airship.
That's even worse than a propeller.

>>8012568
>The propeller's thrust is proportional to the of the density of the medium it's in.
At a constant speed, yes.

The situation is not that bad when you consider that there's less drag on the propeller as well, so you can spin it faster for the same input of work.

>>8012568
https://en.wikipedia.org/wiki/Thrust
See the T^3 hence g^3 term
Now kill yourself.

>>8013966
Did you notice that P is squared on the other side of the equation?

>>8013977
Please tell me you don't study Aerospace engineering. How can you not understand something as simple as propeller thrust?

>>8013993
I'm not the guy you were talking to, I just jumped in on that post. And no, I don't study aerospace engineering, but when people start talking like you are now, it usually means they're trying to bluff.

I looked at your link, and the only T^3 I saw was in P^2=T^3/4pA.

Do you have an explanation for why we should care about the proportion of T to P^2 rather than the proportion of T to P?

>>8011397
Are you seriously this retarded?

>>8014016
NASA is: >>8011560

Don't they use the MRO to scout future terrain for the rovers? Wouldn't a drone be kind of pointless?

>>8012565
>hot helium airship
>not hydrogen becoz oh teh humanity

>>8014024
There's a pretty big difference between looking at things with a telescope from space and looking at them from a few meters in the air.

>>8012569
I don't know about airships, but balloons should be possible, if not overly useful. The density of Mars surface air seems to be about equal to the typical density at ~45 km altitude on Earth, and the altitude record here is about 53 km.

Hydrogen balloons seem a generally better choice than helium on Mars. There is no oxygen atmosphere to make it flammable, and hydrogen can be generated from a variety of compact chemicals, eliminating the need for a pressure storage tank.

File: die in a fire.png (23KB, 1052x700px) Image search: [Google]

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>>8014015
>>8012568
>>8014016
Oy vey you're all retards
Let's do the calculation to shut you up once and for all

>>8014016
>>8014015
>>8012568
Come on fagmasters, where is your comeback now? Don't slink away like a pussy.

>>8014084
>>8014139
Look, I was >>8014015
...and I wasn't objecting to your position, but your argument. I have posted repeatedly in the thread supporting the idea that a Mars copter would be viable. For most of this thread, you've been expressing yourself incompetently and just getting mad when people question you.

Looking back at: >>8011535
>the weight a propeller can lift depends on the cube of gravity but is only linearly proprotional to air density so 1/3 the gravity will increase payload by a factor of 27 while the air density drops it by a factor of 75 therefore it will more or less halve.
You didn't even specify until this last post that you meant the power output, rather than the rotation speed, should be held constant. Now you finally express your actual case, and you act like this is somehow winning against people who tried to guess at what you meant or pointed out that you were being incoherent.

Anyway, this is not even close to being a watertight argument. It assumes ideal efficiency in accelerating air. That's not a model of a real propeller. If you want to make a claim about how much battery power is going to get used based on this equation, you also have to make a case that the propeller efficiency is going to be the same in the near-vacuum of Mars as it is at sea level on Earth.

>>8014271
>"b-but the model isn't perfect"

Grasping at straws, you accuse me of not explaining coherently, now I have you say the maths isn't accurate enough, Will you continue with your plausible deniability BS until I run it through CFD? Until I build a rocket and fly the fucking copter to Mars for live testing? If I am explaining aerodynamics in simple terms of course it's going to be in the ideal case what did you expect? Before you come out with this retarded argument that it still wont fly because of efficiency use your fucking brain, can propellers on Earth still work 30 km up? Yes they can. https://en.wikipedia.org/wiki/NASA_Helios
How about just admitting that I am right, a copter on Mars will fly? Or is that to much for your huge ego?

>and you act like this is somehow winning against people who tried to guess at what you meant

They were the ones shooting down the idea without posting one drop of maths to back up their claim. I am the only one who bothered to back up my claims with maths and you're criticizing me? They were clearly being contrarian dickheads, the argument should have ended from when that other anon posted that NASA was actually planning to do it. But they continued to insist that my idea was idiotic because fuck admitting someone else has a good idea right?

I am mad because everyone on this fucking board has to be a little spoiled egotistical brat, drag out the argument until the end of time by digging up every tiny possibility you can think of in order to avoid admitting that you were wrong. I patiently await whatever bullshit "hole" you can pick out in my idea next. Perhaps you can't find one so now decide to move straight to grammar criticisms or the good old ad hominem?

So you know what? I'll save you the fucking trouble. You are right, I am totally wrong and a fucking idiot who doesn't know what I am talking about. A propeller will never work on Mars. There, you won the argument, go enjoy your cheetos.

>>8014366
>>Look, I was >>8014015
>>...and I wasn't objecting to your position, but your argument. I have posted repeatedly in the thread supporting the idea that a Mars copter would be viable.
>Will you continue with your plausible deniability BS until I run it through CFD? Until I build a rocket and fly the fucking copter to Mars for live testing?
>How about just admitting that I am right, a copter on Mars will fly?
Are you really this illiterate?

Seriously, what is wrong with you? You express yourself incoherently, then when people challenge your gibberish, you hurl abuse instead of clarifying.

When you finally do clarify your fairly weak argument, you act like everyone was being totally unreasonable wanting you to actually express your case, and now they've been proven wrong and should feel humiliated.

This is some serious psychological abnormality going on here.

>can propellers on Earth still work 30 km up? Yes they can. https://en.wikipedia.org/wiki/NASA_Helios
- Atmospheric density at the Mars surface is much lower than it is at 30 km altitude on Earth.
- Helios is not a helicopter. It doesn't do VTVL or hovering at 30 km up.
- It's not a question of whether they work at all, it's a question of what their relative efficiency is.

You made quite a specific claim of relative energy efficiency. You haven't just been arguing that Mars copters are possible, you've been arguing that they'd be nearly as easy and useful as they are on Earth.

>>8014417
You won the argument. I'm an idiot. Drones on Mars are a dumb idea.

File: skycrane.jpg (34KB, 600x450px) Image search: [Google]

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>>8011397
You mean something like this?

>>8014731
Except that thing burns fuel at a crazy rate

>>8014757
So instead of using a tradition source of fuel, use something else like dank memes or human feces.

>>8014770
To be fair it ran on dank memes and sheer human awesomeness anyway

>>8011397
Working on a small helium blimp for just this look me up when I succeed

>>8011476
>the difference in air density makes a much larger impact than you think.
Let's actually quantify it, shall we?
https://en.wikipedia.org/wiki/Disk_loading#Power_required
We'll assume the drone itself remains the same (mass, rotor area) and that air density and gravity are the only things that change. Thus:
>Power req'd = (const) * T^1.5 * rho*-0.5
Due to gravity, thrust required falls by a factor of 2.65, which due to the ^1.5 relationship translates to a 4.3-fold reduction in power requirement.
Atmospheric is some 75(!) times less dense on Mars than on Earth, but this relates to power through an inverse-square-root relation so power requirement increases by "only" 8.6 times.

So you're looking at about twice the power consumption as you would achieve at low altitude on Earth. Not actually as bad as I would've expected, but still probably a lot more than you could support with the meagre power budget of a dimly-lit solar array on a Mars rover.

>>8014731
I'm still amazed that this crazy shit worked. I'm also baffled as to why they would choose it over a simpler short-duration, fixed-impulse approach like on Soyuz or the Viking lander or vid related: https://www.youtube.com/watch?v=4uGfOppQD_g
After all, the descent velocity under parachute should be pretty straightforward to predict (assuming the parachute opens properly), so you should know almost exactly how much impulse you need to arrest the descent just before touchdown. And terminal descent under parachute should be essentially vertical so you effectively eliminate all control issues associated with keeping your "skycrane" level by using a short-impulse system instead.

>>8014812
I doubt it'll work like that
Your prop can only spin so fast
Moving air faster starts hitting diminishing returns hard
There's a reason why choppers have giant rotor blades.

>>8014084
>completely ignoring the momentum flow rate of the propeller
Jesus christ. They might as well rename this place 4chan High.

>>8014879
>Your prop can only spin so fast
I suppose that's true, but IF they were to actually attempt this (which they won't) the propellers would most likely be specifically designed for this exact application.
We can also estimate how much faster an otherwise un-changed propeller would have to spin:
http://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node86.html#SECTION06374100000000000000
>T = (constant stuff)*rho*n^2
Solving for speed::
>n = sqrt(T/(rho*const))
So again, thrust required is 2.65 times less, and air density is 75 times less. Therefore the RPM will need to be sqrt(75/2.65) = 5.3 times faster.
So yeah, mach effects will probably present themselves (compromising propeller performance and somewhat invalidating the above equation/assumptions), and such a drastically high RPM would overstress most off-the-shelf propellers.
>>8014881
Look a few posts above you.

>>8014070
>There's a pretty big difference between looking at things with a telescope from space and looking at them from a few meters in the air.
By that reasoning, why not just put the camera on a tall mast instead? That could be even closer.

>>8014907
>mach effects

add more blades and sweep them back nigger

>>8014915
>By that reasoning, why not just put the camera on a tall mast instead?
That would only increase the vision range slightly. The drone can both fly higher than any mast and fly over the whole candidate track for the rover's day in a couple of minutes. Then they can look it over at NASA and program the rover to follow the whole track, instead of being limited to sending instructions based only on what they can see from the rover's position.

The NASA concept is for a 1 kg drone to scout half a kilometer of track each day, in just a couple of minutes.

This is a pretty decent little video on the NASA Mars drone project:
https://www.youtube.com/watch?v=vpBsFzjyRO8

You can see that they're actually testing it in a low pressure vessel, and it does fly there.

>>8014920
Well yes, but I was working under the assumption of an unchanged propeller so as to properly isolate the effects of the environment only since that was the topic of interest.

Increasing the size and number of blades would indeed increase the thrust coefficient, and in turn reduce RPM/speed requirements. Sweeping the tips (i.e. scimitar props) could help if the tips operate right on the cusp of mach, but if they operate significantly below or above it you probably won't see much benefit (look at the Tu-95 and XF-84H; neither employs propeller sweep despite both having supersonic propeller tips).

Here's something for you guys to look at. We are currently working on a mars flyer. Thinking about giving it a portable base. Not sure if we want it to just capture the flyer or actually attach and recharge it. Check out this kickstarter -

www.kickstarter.com/projects/1924455647

>>8015279
Dead link. 0 results for "mars flyer".

>>8015279
Wow, that got taken down pretty fast.

>>8015279
The fuck you doing a kickstarter for that. Get NASA monies.