/sci/ - Science & Math

[Anonymous No.4954552]

Hey /sci/

See pic. I know most weather balloons use a parachute to slow the free fall after it pops at 30 km, but the footage is very shaky and sometimes the payload starts spinning. Also it lands far from launch site. Would it be possible for this to produce better images and using GPS guide it to fall about in the area it has been launched from?

[Anonymous No.4954555]

I dont think there would be enough resistance.

[Anonymous No.4954561]

>>4954555
You can set up a parachute to open last 200 meters to slow it even further.

Also i got the idea from these seeds

[Anonymous No.4954573]

Is there any other known way to stop the payload from spinning and shaking so much?

[Anonymous No.4954587]

payload is usually a styrofoam box with a camera and gps inside so it is very light. Less then 2 kg.

[Anonymous No.4954597]

Also the images it can produce are just amazing.

Now imagine a HD stabilized camera on it that records the whole journey.

[Anonymous No.4954600]

Weather balloons are not sent up to get pictures.

Your 'GPS' notions only tell it where it is; it does not provide the propulsion to get it anyplace.
If winds move it, you have to counter that wind -- double the force -- to get back. It's a huge amount of additional effort to avoid driving a few miles.

[Anonymous No.4954611]

>>4954597
Those are indeed amazing; but they are a couple magnitudes beyond what you propose.
Those are from at least 90k ft.

And it's a good bet the toughest part was getting the camera back.

[Anonymous No.4954617]

>>4954600
Pictures are still amazing. And when it is at free fall, if you control the wings, you can control where it will fall to using the fall speed itself.

[Anonymous No.4954623]

>>4954597
>HD stabilized camera

Ok, stabilized in what direction?
to get that shot, you'd have to have it pointed horizontally.
To get your descent shot, you'd have to point it down.
If you want to control it, you'll have to put it on a fully-controlled turret and bump up your transmission power a lot.

[Anonymous No.4954625]

>>4954611
That's why you have GPS and 3G internet connection to track it in real time and drive to where it falls.

[Anonymous No.4954633]

>>4954623
If you look on youtube, most cameras on weather balloons are shaky and are spinning a lot. My question essentially is, how does one get a stable shot of lifting and falling to the ground.

[Anonymous No.4954634]

>>4954617
>Pictures are still amazing. And when it is at free fall, if you control the wings, you can control where it will fall to using the fall speed itself.

OK, so why make it free-fall?
If you want to control it, and you need propulsion and control, we already have science for that -- make it a glider.
Don't re-invent a falling box and try to make it do things it cannot (like return to the launch point).

[Anonymous No.4954641]

>>4954634
so basically you lift a RC glider with a mounted camera and use it to glide back to the launch site?

[Anonymous No.4954651]

>>4954641
>>4954634
but that would require you to drive it around in circles

[Anonymous No.4954656]

>>4954625
>That's why you have GPS and 3G internet connection to track it in real time and drive to where it falls.

yeah, I understand that.
Do you understand that from such a height, it might be quite far away?
How about the conditions of operation? Have you considered whether (heh) certain pieces can operate at very low pressure and temperature?


You're trying to solve the 'stabilization' issue (complex enough) and also make it land at it's launch point (probably silly) before you even understand the basics.

[Anonymous No.4954666]

>>4954656
you pick a day with minimal wind and maximum visibility (no clouds) so you can track it using binoculars, also i think raspberry pi or something similar would withstand the low pressure

[Anonymous No.4954669]

>>4954651
>but that would require you to drive it around in circles

The glider? no, you wouldn't put big wings on a glider that you send that far up; but yes, it would be flying in many directions most of the time.

If you are talking about the picture direction, that was going to do that whatever the solution for guiding the device back to the launch point.
It isn't going to go straight up and then straight back down the same way.

[Anonymous No.4954693]

>>4954669
it would still be shaky if you fly a glider back to the launch site. also it wouldn't always point to the same direction.

[Anonymous No.4954696]

How about lifting a quadcopter and using its propellers and gyro senzor to stabilize the camera?

[Anonymous No.4954699]

>>4954666
>you pick a day with minimal wind and maximum visibility (no clouds) so you can track it using binoculars,
Yes, minimal wind is necessary for stabilizing your camera, too -- but you may have no way to know about the winds at, say, 8k and 12k and 20k feet.
And why binoculars? You had GPS; that will work.

>also i think raspberry pi or something similar would withstand the low pressure

Why would raspberry pi handle that better than something else?

[Anonymous No.4954705]

>>4954693
yes, the glider isn't the stabilizing method.
The glider is the answer for getting back to launch point.

Stabilizing is a separate issue,
camera direction is a separate issue.

[Anonymous No.4954712]

>>4954696
>How about lifting a quadcopter and using its propellers and gyro senzor to stabilize the camera?

To do what?
You can't expect such tiny devices to keep anything stable coming down through a real atmosphere -- it couldn't even keep itself level, forget about stable!

[Anonymous No.4954719]

>>4954699
i don't think low pressure and temperature is an issue with electronics, and yes, you're right, wind is unpredictable so you would need a system to guide the payload back to the launch site (without spinning)

>>4954705
stabilization is a priority here.. i've looked it up and people have been sending gliders up and guiding them to the launch site before

[Anonymous No.4954725]

>>4954712
you can still have a big parachute to slow it down, and the rotors would keep it stabilized in theory

[Anonymous No.4954726]

>>4954696
Those things are barely 'stable' carrying 5 grams of mass and in carefully controlled rooms of entirely dead air.
I dare someone to fly one outdoors above 30 feet. It's gonna flop around like a tumbleweed.

[Anonymous No.4954735]

>>4954726
that's because they are so small. bigger rotors = more stability

[Anonymous No.4954743]

>>4954725
no, the extremely tiny rotors of those things are helpless in real atmosphere. Forget it.
Or, upgrade -- stabilize the descent with a set of larger passive rotors, and perhaps have friction tabs to slow separate rotors for guidance.

OP's initial concept for a rotor to slow descent was good, because it was passive and well above the weight center.
But it doesn't stabilize the camera, and it doesn't come back to home.

[Anonymous No.4954756]

>>4954743
wouldn't the wings on the payload provide resistance towards spinning? also by tilting the wings a bit you could control where it would land

[Anonymous No.4954770]

>>4954756
>wouldn't the wings on the payload provide resistance towards spinning? also by tilting the wings a bit you could control where it would land

Assuming the initial payload shape (which I didn't think we were assuming yet), of course.
But that isn't going to be stable, just less shaky.

And if you want directional control, they have to be very much larger and also radio-controlled.
(Small wings like that only matter to free-fall speeds.)

In general, the slower it goes, the larger your control surfaces are going to have to be.
(And remember, if you want to radio-control something, you're going to want to see it, so very high altitudes may be pointless.)

[Anonymous No.4954775]

>>4954770
i don't care if i have to drive 10 miles to pick it up, as long as the footage isn't shaky and somewhat stable. if bigger wings mean better stability, then i just use bigger wings

[Anonymous No.4954776]

Let's address the more important feature, to your project, because we've got too many problems in hand now.

Stabilization of the camera: how?
Let's assume pointing straight down, because it sounded like you wanted the descent to earth shots most.
does it keep rotational orientation? How accurately?
is it kept stable with a passive system or active electronic system?

[Anonymous No.4954795]

If it were mine, I'd want to go entirely passive.
I might entertain a dragging wing -- like the sycamore seed, a long wing on one side that just induces drag on one side.
It won't keep the camera in a specific direction (it will change) but it should keep it from changing very quickly.
Maybe just a long, stiff wire (with a bunch of rip-stop nylon strips at the far end) that springs out when the balloon tension lessens.

[Anonymous No.4954802]

>>4954776
the whole payload wont be shaking as much because it is not being slown down by a parachute (which behaves strange in horizontal winds)
to stop it from spinning you add wings (bigger then what i've drawn) when its falling, they cut the air and provide resistance against spinning.
as for electronics, the wings are supposed to be controlled by raspberry pi, based on gyro sensors and a compass, all programmed in, not from the ground.

[Anonymous No.4954817]

>>4954795
so basically using a rotor and a rope/wire to slow the descent would in theory produce more stable footage then using a parachute would?

[Anonymous No.4954821]

>>4954795
>that springs out when the balloon tension lessens.
Not sure what I was thinking; it would stabilize on the way up, too.

[Anonymous No.4954832]

>>4954817
well, probably.

You could probably also alter a parachute so that it keeps airflow stable in one direction, and that would stabilize the camera direction.

Similar to paragliders' wings, they just direct airflow so they get control. They add some descent speed to do it, but that's not your first concern.

[Anonymous No.4954853]

>>4954817
I'm thinking a medium rotor (several blades) and a big drag-inducing tail sticking way off one side would give you both slower descent and pretty stable directionality.

but, if you have the means, a classic parachute with one quadrant let out a bit (or a vent in the quadrant center) might do a similar job.

Either way, it would be nice if you could find someone modeling falling bodies with such things -- maybe emergency egress models for space shuttle, or jet pilots?

[Anonymous No.4954859]

>>4954832
yeah but keeping it from spinning is a problem here, because paragliders pull one side down to go into a spiral if they want to descent straight down

[Anonymous No.4954863]

Oh, Hell, what am I thinking?

I'll bet you can find kite builders that could answer this stuff in minutes! -- you might even find someone who will help out!

[Anonymous No.4954874]

kite builders are dealing with the right range of forces, some familiarity with the altitude issues, and are concerned with both good framing materials and lightness.

[Anonymous No.4954884]

http://www.grc.nasa.gov/WWW/k-12/airplane/kiteprog.html

[Anonymous No.4954888]

i'll probably just do it. a weather balloon and some hydrogen doesn't even cost that much. cant be sure if it works if you don't try it.

[Anonymous No.4954890]

http://www.grc.nasa.gov/WWW/k-12/airplane/short.html

bunch of pages on forces and dynamics that are relevant.