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Old Aug 21, 2012, 01:12 AM
Drydock Captian
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Spanaway, WA
Joined Jul 2006
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Idea
DIY Space Craft

OK I am usually hanging out on the boat forum but after my son and I watched some kids send a Lego Shuttle into near space. This got us thinking about making our own near space craft and launching it.

Now you are all saying Ya ya this has been done and there are DIY articles all over the place on how to make your own craft. This is not in question as I have a good idea of the materials needed to launch a camera or a lego device into near space but I want to do a little more than that.

I have been working on a plan for the craft, launch, recovery and telemetry. I am in need of help for one system I would like to have onboard to make the recovery area smaller. Here is my idea:

The craft I am planning is going to be similar to the Mercury or Apollo space craft although not in scale to these craft just a basic blunt body conical shaped craft. Materials planned are pink extruded foam and balsa.

I am planning on installing a 1W 20MHZ CW transmitter for recovery sounding. I plan on building a digital controller to pulse the CW once per second or so to assist in finding the craft with a directional antenna. I have schematics for these units already I just need to experiment to find the one that will work best with low power consumption and good range. This will also have several LEDs that blink with the pulses to aid in visual locating.

I want to actually control the deployment of the parachute. This will be the key in making a close recovery range. This is also where I need your guys' help. Here is my ideas. The parachute itself will be contained in the nose of the capsule and attached to the lines of the baloon. This will allow the bursted baloon to act as a droge chute and also help keep the capsule pointed blunt end down. A simple release mech will activate at a given altitude to release the chute to slow the craft for a safe landing.

Now my problem is how to make an altimeter that will be able to trigger a soleniod or servo to release the recovery devices.

I thought about a timer mech but without knowing the total acent time and decent time I would hardly be able to calculate the proper time for deployment. My thoughts are drifting to using a microprocessor controller and digital altimeter. I am looking into the Raspberry Pi with the GERTboard as the interface. Any ideas?

I am thinking that if I could get the RB to record temps and altitude as data for the mission and also trigger the servo at say 3000' I may actually succeed in doing more than just sending a camera up into near space. Oh and yes I do plan on having a camera onboard as well. Also if this succeeds I am thinking about using it as a teaching tool for the local schools if they will have me.

Massey
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Old Aug 21, 2012, 01:39 AM
Stuart
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UK, Cardiff
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Originally Posted by Massey View Post
I am planning on installing a 1W 20MHZ CW transmitter for recovery sounding. I plan on building a digital controller to pulse the CW once per second or so to assist in finding the craft with a directional antenna.
A lot of balloon work is done with 144Mhz or 434Mhz. There is ready availability of high gain directional antennas that are also small for carrying. Lots of DIY plans of antennas for this frequency.

A directional antenna at 20Mhz ?? Wont be small.

Also consider how you are going to receive the signal, not a lot of people will have CW\SSB gear that can be carted around the countryside looking for a transmitter.

You also need to know what is legal for people to use without a amateur radio licence.
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Old Aug 21, 2012, 01:58 AM
Drydock Captian
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Spanaway, WA
Joined Jul 2006
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Radio license is not an issue, I have many HAM friends and will have my general license before the flight. One of the people helping me with the radio tracking has the ability to track my transmitter. The main reason for the 20MHz is the ability to transmit long distance with low power use. This is also still not a final configuration as I am still in the planning stages. Once I start experimenting with transmitters and tracking I may revise this part of the plan. Thank you for the input on the other feqs as I will look into them and building the equipment needed.

Massey
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Old Aug 21, 2012, 02:32 AM
Stuart
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Well you did say you were interested in using this as a teaching tool for schools. I doubt many schools have specialised 20Mhz CW\SSB gear or have the ability to operate it.

There is a satellite in orbit, ITUPSAT1. It has a Morse beacon that transmitts on 437.325Mhz, 100mW FM Morse. It can be picked up on most (cheap) scanners, or a cheap UHF transceiver, no specailist or difficult to use equipment required.

A close pass, 500km out, 730km altitude, can be heard with a handheld UHF transceiver and a rubber duck antenna. With an arrow antenna (a modest yagi) I have heard the Morse beacon when its 2000kM out.
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Old Aug 21, 2012, 03:18 AM
Drydock Captian
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Spanaway, WA
Joined Jul 2006
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Im going to try to use it for the schools, but I want to get a better grip on the technology and recovery before attempting schools. This could also be a scout project. Not sure how far I am going to take it but I do know that at least once my son and I are going to make the attempt.

Now while the radio locating is going to be developed with the assistance of my boss (who is an experienced HAM operator), the help I really need is for a way to trigger the deployment of the parachute at a given altidude. I have been searching the forums here and found a couple of threads on DIY altimeters. The altitudes I am going to be working with here are around 15-20 miles and I am thinking that if I can get a chute deployment at about 3000' my craft should be able to slow down enough for a safe landing. A delay in the release of the chute will minimize the drift from high altitude winds. My biggest fear with a system like this is the sensors I have found have a small hole in them to measure atmospheric pressure. This sensor needs to have access to outside air and when the craft is 10miles or higher the temps are going to be well below freezing. This may cause condensation around the sensor to freeze the hole up and prevent it from reading pressure, thus failing to deploy the chute.

Just more things to think about and problems to solve.

Massey
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Old Aug 21, 2012, 03:52 AM
Stuart
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Well a standard GPS module will give you an altitude up to 60,000ft, so its easy enough to work out when you are on the way down and reach 3000ft.

You could also transmit the GPS location too, makes the balloon easier to find. .
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Old Aug 21, 2012, 04:21 AM
Drydock Captian
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Spanaway, WA
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Are you talking about a DIY GPS? I am thinking about using a GPS tracker but I dont really want to pay a couple hundred for the unit and then a monthly fee to allow me to track it on google earth or other such application. I was thinking of cheap GPS enabled cell phone. Reliable DIY GPS would be alot more fun to do over just getting a $50 phone. I guess if I used the GPS as a backup to the altimeter and could get it to also send a trigger signal to the Raspberry I could make that work.

Massey
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Old Aug 21, 2012, 08:35 AM
Stuart
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Are you talking about a DIY GPS?
Yes indeed.

See my recent post for details.

I am currently working on a slightly smaller version of the ground station PCB, that will fit inside a 50mm x 50mm cube satellite. Its due for launch into real space in November.
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Old Aug 21, 2012, 07:16 PM
Drydock Captian
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OK I like your GPS stuff but I am not sure it will work for my tracking needs. From my research about these balloon space craft they can end up 30-70 miles from the launch site. This appears to be out of the range of your device. Your device on the other hand may be able to be used as a failsafe or primary for my planned recovery system. I am going to do more research into this.

A question for you if you dont mind. Can the device you posted about be set up to send data to the gertboard and then have that data be relayed back to the processor to control the release mech and possibly post the data to a log file to allow after recovery tracking?

Massey
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Old Aug 22, 2012, 12:39 AM
Stuart
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Originally Posted by Massey View Post
From my research about these balloon space craft they can end up 30-70 miles from the launch site. This appears to be out of the range of your device
If your wanting to radio locate the downed balloon from up to 70 miles away when its on the ground, thats not going to be easy.

For a lot of balloon work, 434Mhz 10mw transmitters seem to be fairly common, check out the Radiometrix NX2 being used here, its also a mere 10mW.

http://www.dcemu.co.uk/vbulletin/thr...o-130-000-feet.

If your tracking the balloon in flight, then when the balloon bursts, it will come down fast, so the search area should be fairly small.

The RFM22 device I have been using is 100mW, giving approx 3 times the range of a 10mW device.

Part of the reason for using also using Morse in my locator to transmit distance and direction information is that it can be heard, and decoded by ear, at distances that exceed what is possible with standard data radios.

This satellite is also a 100mW Morse transmitter, you will hear it during a pass with just a UHF handheld transceiver and rubber duck antenna.

http://www.satview.org/?sat_id=35935U&cat=amateur

Far enough ?
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Old Sep 04, 2012, 09:12 PM
Drydock Captian
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Spanaway, WA
Joined Jul 2006
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I dont have much of an update, but I have recruited a friend that lives in Norfolk VA who is studying electronic engineering and is going to assist me in developing a temp sensor that can read as low as -100F. The plan is to build a circuit that will feed an analog signal back to the IO board's A/D converter inputs.

More research of the comunications needed and I also found out that on top of the GPS system I (after I get my HAM license) can use the APRS system to assist in tracking and location. As for the frequency I am prolly going to use a freq. that is used in my area for data over air.

I will keep you all informed.

Massey
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Old Sep 06, 2012, 06:19 PM
Drydock Captian
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Spanaway, WA
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OK just found out that the Raspberry Pi now has a 40 day lead time. This is on top of the 21 day lead time from 3 weeks ago. I have the basic design drawn out but I want to have the 2 main boards in my posession before I finalize any designs. The IO board will be available in about a week and I am going to put my order in for it tonight.

Massey
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Old Sep 07, 2012, 12:13 PM
Stuart
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I have been thinking of trying the party balloon approach as a first step;

http://aprs.org/balloons.html

These dont go so high as the balloons dont expand, and I like the idea of being able to remotely command the release of the balloons for descent.

I reckon the payload, transmitter, GPS and battery ought to be less than 50g.
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Old Sep 07, 2012, 08:58 PM
Drydock Captian
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Spanaway, WA
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I was thinking about doing something like this as a preliminary test of the ship. I was planning on first doing a tethered test of the GPS and temp sensors after a drive around test.

I got a Pi on Evilbay it should be here in a few days and I will be able to start on learning the little machine and be able to get some dimensions for the craft's construction.

Massey
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Old Sep 08, 2012, 10:09 PM
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Blue Bell, PA
Joined Aug 2002
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DIY Spacecraft

Space starts at 62 miles (100 kilometers)
This appears to be a balloon ascent?

Why not use Arduino type system
Lots of arduino boards out there and piggy back boards to do
all kind of things.
Arduino runs many UAVs ,quadcopter craft and robots

Arduinos IN SPAAAAACEEE!
http://www.arduino.cc/cgi-bin/yabb2/...=1267953451/55


http://www.sparkfun.com/
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