Re: [Paparazzi-devel] StratoBlimp, a challenging UAV project

[Hector Garcia de Marina]

Hi Peter,

I was involved in a project similar to yours, but finally because budget issues we could not fly. However we addressed some of the problems that are not present in "conventional" UAV flights.

One of the most important problems is the detachment of the UAV from the balloon. The balloon spins and it could lead to a non recover situation for your glider from the start, pay special attention to this key element, or the whole missions would

be ruined. Orr system consisted in two rails attached below the bottom base of the balloon with the UAV's wings blocked on the rails. Do you have any concept about your vehicle?

Also remember that the air density is low at those altitudes, therefore the "free fall period" (or lets say the control over your vehicle is minimum) must be designed for do not let the UAV spins at high velocities. Also you will reach a really high speed, the fuselage must be really well made for preventing fluttering, probably staying only at 3Kg as maximum could be an issue to solve.

Also, high speed + high altitude is a bad combination for a common GPS, but I guess for this stage, the most important thing is to stabilize the vehicle instead of tracking a trajectory.

Another issue is the calibration of your sensors in temperature and pressure. You should consider to add a heater (power resistor + battery) for keeping the temperature of your sensors constant.

About communications, you should have a direct path between your ground station and your balloon or vehicle right? With a high gain antenna on ground you should be able of communicate with your UAV. I have seen many times live HD video

from weather balloons, so the bandwidth should not be a problem.

Héctor

On Tue, Nov 20, 2012 at 9:33 AM, P.J.S. Danneels <address@hidden> wrote:

Dear Mr. Baumann,

The main focus is on getting it to its designated landing site with a launch from the stratosphere.
Our craft will probably not generate a lot of lift at those high altitudes and will most probably be in some sort of free fall for the first 10-20km but we will do detailed simulations on this in the coming weeks. We must stay within weather balloon regulations to get it up their without much special permissions so the size and weight are very limited.

Kind regards,
Pieter

On 19/11/2012 17:38, Tilman Baumann wrote:

I don't think I can help with practical issues.
But I wonder, does the design call for the balloon to pop in the stratosphere?
The term Blimp confuses me.
Is it about coming home, or about zipping around in the stratosphere?

I'm very interested in high altitude glider projects. But I don't think very much has been done in practice yet. But it's such a cool idea.

On 19/11/12 16:26, P.J.S. Danneels wrote:

Dear Paparazzi community,

Allow me to introduce our project to you.

We are a group from the Delft University of Technology faculty of Aerospace Engineering.
Our goal is to design and later build a UAV which is launched from a weather balloon in the stratosphere (say about 35km altitude).
It should then return to the landing site without using direct propulsion.

What is interesting for this mailing list:
- we will use paparazzi as the autopilot
- we must have 2 way communication with the vehicle to retrieve weather data and manipulate it's flight.
- loads of other UAV-stuff

Some initial calculations, thoughts and requirements:
- Balloon might drift allot during ascent. A drift of up to 300km might well be possible according to some simulations.
- To stay within weather balloon regulations the weather balloon payload (return vehicle + release mechanism) may not exceed 3kg
- The configuration at launch cannot have a diameter exceeding 2m
- We cannot use propulsion to gain or keep altitude but we can accumulate energy on the descent and then use it in some way to decelerate the craft on it's final approach.
- We need to film the mission in HD
- We need to be able to take a scientific payload with us. Currently not yet defined but will most probably be meteorologic sensors.

An initial question:
- 2 way communication over a range of 300km is almost not possible using a direct link to a single ground station, so we are tempted to use satellite communication modules like the Iridium 9603 is there any experience in this community regarding these modules and interfacing them to paparazzi?

I believe lots of you might find this an interesting problem.
As none of us has much experience with UAV's and paparazzi any idea's or advice is welcome.
Our team consists of 10 highly motivated students, some with expertise in aero, some in embedded electronics, other in aircraft structures, ...etc.

If you guys like this we could post an update on our project from time to time. And share our finding with you.

We hope to hear from you guys with any thoughts, questions, idea's.

Kind regards,

Pieter Danneels
StratoBlimp project
(don't let the name fool you, it's not going to be a blimp... we think)

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--
Héctor