Manual In-Flight Commands

[jwatts2020]

Hi All,

I am working in a college team for a rocketry competition. We have a payload that has to be released from the rocket manually via ground station while the vehicle is in flight. Our rocket will be in the correct orientation for the payload to deploy, however were having trouble finding ways to manually release this payload from the ground. Unfortunately we don't have members who are strong in coding or computer science so were trying to find a commercial off the shelf solution for our payload release. Any ideas for what we can use? We have thought about transmitters and receivers as well as altimeters.

 

[MarsLander]

What is the payload? When does it need to be deployed in the flight profile? What are the expectations for the recovery capabilities of the payload?

 

[jwatts2020]

What is the payload? When does it need to be deployed in the flight profile? What are the expectations for the recovery capabilities of the payload?

The payload is a descending EDF vehicle. It will using a duct fan to slow it down as no parachutes are allowed.

We can release it anywhere from 400-800ft and it must be released manually.

 

[user 30299]

Which competition are you participating in?

 

[Titan II]

A standard RC transmitter/receiver such as this will work. That, and whatever servo(s) you may need for the release mechanism. How is the actual altitude at release determined? In other words, how do you prove it? Do you need to prove it? That may impact the telemetry requirements.

https://www.towerhobbies.com/produc...ansmitter-with-r3106gf-receiver/FUTK5000.html

 

[Voyager1]

Define “released manually”?
Your typical choices are via wireless remote control, or any altimeter that can provide a servo output at a specific time or altitude.

 

[Titan II]

Define “released manually”?
Your typical choices are via wireless remote control, or any altimeter that can provide a servo output at a specific time or altitude.

I would think an altimeter as we know them is out of the question given the criteria he outlined.

"We have a payload that has to be released from the rocket manually via ground station while the vehicle is in flight. Our rocket will be in the correct orientation for the payload to deploy, however were having trouble finding ways to manually release this payload from the ground."

 

[Handeman]

I once used a RC controller (similar to what @Titan II linked to) and receiver with dual servos with 90° throw from a center position. The two arms were set up to create electrical contacts when moved to the full swing position. Both servos needed to be move to full opposite positions to make electrical contact and set off an ejection charge. I found this to be much safer and reliable than using receiver controlled electronic relays. It worked quite well for a manually controlled deployment.

 

[GalantVR41062]

If you can find a Missle Works WRC2+ or similar. This is a multi channel ground controlled device.

 

[user 30299]

The payload is a descending EDF vehicle. It will using a duct fan to slow it down as no parachutes are allowed.

We can release it anywhere from 400-800ft and it must be released manually.

Which competition is requiring this?

 

[Scott_650]

Which competition is requiring this?

Probably the NASA Student Launch Initiative.

 

[user 30299]

Probably the NASA Student Launch Initiative.

Section 4.2 and 4.3 of the SLI Competition Handbook

Looks to be tough requirements this year on the payloads.

 

[VernK]

Looks to be tough requirements this year on the payloads.

I don’t know if the Kate system is suitable for the SLI competition. If nothing else, it might be too expensive. However, it does allow manual uplink commands to fire pyro outputs during a flight. A manual uplink command can also be sent to open or close the general purpose solid state relay Kate has.

 

[PSLimo]

I'm building a bomb replica rocket that will use manual R/C for parachute deployment. Wish I still had my WRC2 remote but will give this one a try that might work for you if you're looking to release with a pyro charge:

https://www.apogeerockets.com/Electronics-Payloads/Dual-Deployment/TripleFire?cPath=52_191&

 

[Ulyu]

I think you might want to take a look at the Fluctus.
It's a very versatile flight computer that can do exactly what you want: remotely turn a servo while the rocket is in flight.
I'm the person behind it, so don't hesitate if you have any questions.

 

[cerving]

R/C systems are cheap (< $100 for this application), the biggest issue is getting visual confirmation that it's OK to deploy the payload. They'll need real-time telemetry to confirm the AGL altitude in order to get it right.

 

[jwatts2020]

Define “released manually”?
Your typical choices are via wireless remote control, or any altimeter that can provide a servo output at a specific time or altitude.

Must be released from the ground station and not "programmed" to an altitude or time in flight.

 

[jwatts2020]

R/C systems are cheap (< $100 for this application), the biggest issue is getting visual confirmation that it's OK to deploy the payload. They'll need real-time telemetry to confirm the AGL altitude in order to get it right.

We will have an RSO that is giving us approval for release of payload

 

[jwatts2020]

I think you might want to take a look at the Fluctus.
It's a very versatile flight computer that can do exactly what you want: remotely turn a servo while the rocket is in flight.
I'm the person behind it, so don't hesitate if you have any questions

I will take a look into this device! Does it require a HAM radio license?

 

[Ulyu]

I will take a look into this device! Does it require a HAM radio license?

No, its radio is in the 915 mhz free band and is exempt from authorization requirements, like eggtimer products for example.

 

[user 30299]

I think you might want to take a look at the Fluctus.
It's a very versatile flight computer that can do exactly what you want: remotely turn a servo while the rocket is in flight.
I'm the person behind it, so don't hesitate if you have any questions.

Your servo feature shows a 3.3-volt supply. Will this be able to adequately operate a standard R/C servo
which uses 4.8 to 6 volts? Mini and micro servos also have the same voltage requirement. Or would the
servo need to be a Nano, or Micro Nano, which use 2.8 to 4.8 volts?

 

[Ulyu]

Your servo feature shows a 3.3-volt supply. Will this be able to adequately operate a standard R/C servo
which uses 4.8 to 6 volts? Mini and micro servos also have the same voltage requirement. Or would the
servo need to be a Nano, or Micro Nano, which use 2.8 to 4.8 volts?

Most hooby R/C servos (or at least the ones I have used) work well with a 3 volt input signal.
In general, the signal voltage don't need be the same as the supply voltage, but it's worth checking their manual.

 

[user 30299]

Most hooby R/C servos (or at least the ones I have used) work well with a 3 volt input signal.
In general, the signal voltage don't need be the same as the supply voltage, but it's worth checking their manual.

It would be good if your manual pointed out the signal & supply voltage condition, and maybe
offer a wiring schematic example.

This is the next obvious question from the university student, and eventually from other people
looking to use the servo feature.

 

[Ulyu]

It would be good if your manual pointed out the signal & supply voltage condition, and maybe
offer a wiring schematic example.

This is the next obvious question from the university student, and eventually from other people
looking to use the servo feature.

Okay, I'll add a some more details about servo motors in the next version of the manual.
Also, there is already a reference wiring diagram page 11 and some information about the general purpose outputs page 12.

 

[user 30299]

Most hooby R/C servos (or at least the ones I have used) work well with a 3 volt input signal.
In general, the signal voltage don't need be the same as the supply voltage, but it's worth checking their manual.

If you have different signal and supply voltages (and source), would you require a common ground
so that the servo functions accordingly?

 

[cerving]

Yes, you need a common ground between the servo and your flight computer to reference the servo control signal to. You can (and probably should) use a separate battery for the servo, between the servo's power leads, and I'd recommend putting a power filtering capacitor across the servo's power leads too... maybe 100 uF or so.

 

[user 30299]

Yes, you need a common ground between the servo and your flight computer to reference the servo control signal to. You can (and probably should) use a separate battery for the servo, between the servo's power leads, and I'd recommend putting a power filtering capacitor across the servo's power leads too... maybe 100 uF or so.

Thanks for confirming the common ground condition.

Is the filter for reducing voltage "noise"?

 

[cerving]

Yes, you do not want any noise from the servo going back into your flight computer's ground. Honestly, if I was going to build a dedicated servo driver circuit I'd use optoisolators between the flight computer and the servo... no chance for any servo noise at all to get into the flight computer.

 

[user 30299]

Yes, you do not want any noise from the servo going back into your flight computer's ground. Honestly, if I was going to build a dedicated servo driver circuit I'd use optoisolators between the flight computer and the servo... no chance for any servo noise at all to get into the flight computer.

Here's an Arduino example. This is "roughly" what you are talking about? But resistors used vs. optoisolators.








An Arduino and standard servo work with with 5 volts. But the signal voltage on the Fluctus is 3.3 volts,
hence the "separate" power conditions.

 

[cerving]

You still have a common ground between your servo driver and the Arduino, so the possibility of noise coming back into the Arduino is still there. Optoisolators remove that completely because there is essentially no electrical connection between the Arduino and the servos. Look up the MCT6 optoisolator... they're very easy to use.