High G-Force Capable Avionics Components

[jderimig]

That seems like a good suggestion. Is it common practice for people to essentially copy elements on a breakout board into their pcb design? For example, the BME280 barometric pressure sensor is sold both in breakout board and indivdual sensor forms. Would you recommend just copying/integrating the resistors and capacitors that might be on the commercial breakout board into my pcb design since my final pcb design won't utilize breakout boards? T

Absolutely!

In the mean time, what sensors would you recommend overall for the bigger pcb I had planned for my Mach 3 rocket project? I'm trying to get as wide of a spread of input as possible to see the pros and cons of different approaches.

There all good and probably all are using the same dies anyways. I am partial to ST chips and TDK/Invensense IMU chips.

 

[Spacedog49Krell]

Wow, that is extremely impressive for a university team. I recently watched the BPS Space video on roll controll with a fin tab. It was a neat summary of all the different roll control methods that can be used (including canards). Leading canards and moveable fins are especially difficult since just the slightest movement can have a massive impact on performance on the roll axis and they typically have a larger surface area interfering with the windstream compared to the smaller fin tab method.

Not a university team, this is a High School ARC team. The canards, in the zero position, produce little slip stream drag. They have flown their rocket with the canards locked in the zero position and without the canards on the rocket with no appreciable difference in max altitude. I was an advisor on the Cal State Long Beach Space Cup Team. They never got their altitude control system to work. This ARC project is on the level of USCRPL Traveler 4 and UCLA Ares liquid rocket. The last problem to resolve is keeping the rocket flying vertically.

 

[OverTheTop]

The only components I would worry about, if you are using surface mount parts, are crystals. They can be mechanically fragile under acceleration. The newer crop of mems-based oscillators exhibit far less frequency drift under acceleration and are more robust. This situation would likely apply to your microprocessor clocking.

I would consider using through-hole connectors as they are more robustly connected to the board.

If making a PCB use minimum two layers with plated-through holes. That gives you more reliable solder joints than single-sided.

Stay away from larger components if you can, especially skinny but tall ones.

For some added reassurance on things like connectors and electrolytic capacitors (if using them) you can glue them to the PCB using Loctite 401 or similar.

 

[Spacedog49Krell]

The only components I would worry about, if you are using surface mount parts, are crystals. They can be mechanically fragile under acceleration. The newer crop of mems-based oscillators exhibit far less frequency drift under acceleration and are more robust. This situation would likely apply to your microprocessor clocking.

I would consider using through-hole connectors as they are more robustly connected to the board.

If making a PCB use minimum two layers with plated-through holes. That gives you more reliable solder joints than single-sided.

Stay away from larger components if you can, especially skinny but tall ones.

For some added reassurance on things like connectors and electrolytic capacitors (if using them) you can glue them to the PCB using Loctite 401 or similar.

As a former semiconductor engineer, retired, I tested components to failure. Mass is the enemy in extreme high load applications. Through-hole components appear more robust, but they are higher mass components with malleable connection wires. Surface mount components are superior in high G load environments. Today's, clocking crystals and resonators remain within frequency specifications with a 1000 G load for milliseconds of time. I worked with engineers that tested component functionality to 12,000 G's. We have a long way to go before our rockets will have component issues.

 

[OverTheTop]

As a former semiconductor engineer, retired, I tested components to failure. Mass is the enemy in extreme high load applications. Through-hole components appear more robust, but they are higher mass components with malleable connection wires. Surface mount components are superior in high G load environments. Today's, clocking crystals and resonators remain within frequency specifications with a 1000 G load for milliseconds of time. I worked with engineers that tested component functionality to 12,000 G's. We have a long way to go before our rockets will have component issues.

I looked into this a while back and the MEMS devices certainly had the edge over the crystals I was looking at. I guess there may be other crystals that are more stable under acceleration than I was comparing.

Agreed on the SMT components, but we do find that connectors are more robust in a through-hole configuration, especially when the Service people are mating and removing. You do, of course, pay a penalty in board space as the connector takes up space on both sides of the PCB.

 

[Spacedog49Krell]

I looked into this a while back and the MEMS devices certainly had the edge over the crystals I was looking at. I guess there may be other crystals that are more stable under acceleration than I was comparing.

Agreed on the SMT components, but we do find that connectors are more robust in a through-hole configuration, especially when the Service people are mating and removing. You do, of course, pay a penalty in board space as the connector takes up space on both sides of the PCB.

Resonators have the typical semi standard of 10,000 G shock for 200 microseconds. Quartz crystals are a little lower at 5,000 G shock for 300 microseconds. There could be crystal orientations that have lower shock tolerance.

Connectors are a different issue. They do not tolerate high G loads unless they are thread mated to each other.

 

[jderimig]

I was involved in a feasibility project for electronics that are shot out of a cannon. 10,000G then scale up to 20,000G. There are crystal suppliers that can meet the 10,000G spec. Of course the time is very short for that event. The requirement was not to operate at 10,000G but to survive it then run.

 

[rocket_troy]

I looked into this a while back and the MEMS devices certainly had the edge over the crystals I was looking at. I guess there may be other crystals that are more stable under acceleration than I was comparing.

Agreed on the SMT components, but we do find that connectors are more robust in a through-hole configuration, especially when the Service people are mating and removing. You do, of course, pay a penalty in board space as the connector takes up space on both sides of the PCB.

Yes, the effects of acceleration on crystal resonators has been studied and documented thoroughly - particularly back in the 70s. Their sensitivity has no doubt been significantly reduced since then, however, back then there were techniques to provide 1st-order cancellation of the effects of acceleration (on a single exposed axis), such as, utilising 2 in series, mirroring each other.

TP

 

[Spacedog49Krell]

Yes, the effects of acceleration on crystal resonators has been studied and documented thoroughly - particularly back in the 70s. Their sensitivity has no doubt been significantly reduced since then, however, back then there were techniques to provide 1st-order cancellation of the effects of acceleration (on a single exposed axis), such as, utilising 2 in series, mirroring each other.

TP

I've used mirrored single channel MEMS gyros to cancel drift.

 

[Sooner Boomer]

Here's what happens to a circuit board under high Gs. This is an Eggtimer Apogee that came down in a rocket from about 4000 feet. Probably going 4-500 fps when it hit. It buried the nosecone about 8" deep, so that's the distance the acceleration took place over. You can calculate the force. Almost all of the through-hole components were sheered off. The top of the baro chip was popped off (lower right corner, between the resistors and the cap). I keep this as a reminder.

 

[Dominic Bleacher]

As a former semiconductor engineer, retired, I tested components to failure. Mass is the enemy in extreme high load applications. Through-hole components appear more robust, but they are higher mass components with malleable connection wires. Surface mount components are superior in high G load environments. Today's, clocking crystals and resonators remain within frequency specifications with a 1000 G load for milliseconds of time. I worked with engineers that tested component functionality to 12,000 G's. We have a long way to go before our rockets will have component issues.

That does make alot of sense. I never would have thought about it like that, but I can totally see how that would be true. I know I said I was going to hold off on the gps and the other computer components for now, but I've seen many folks that seem to have problems with good, consistent gps. This is certainly a concern because I don't want to have to worry about packet loss and flawed data packets. While I know that how the gps system is physically installed in the rocket is a major component to good reception (ie not in a solid carbon fiber frame unless there is an antenna patch, antenna cutout, etc.), what other things cause these gps related issues? Is it a ground antenna thing (what signals are commonly operated off of and is it because people need to triangulate) or is it the actual gps module itself that struggles with either high velocity, acceleration, or altitude (or all of these combined)?

Can something like the LORA gps modules transmit gps location and live telemetry to a ground station, or is it solely for gps and I would need another unit for live telemetry values?

Thanks.

 

[cerving]

Here's what happens to a circuit board under high Gs. This is an Eggtimer Apogee that came down in a rocket from about 4000 feet. Probably going 4-500 fps when it hit. It buried the nosecone about 8" deep, so that's the distance the acceleration took place over. You can calculate the force. Almost all of the through-hole components were sheered off. The top of the baro chip was popped off (lower right corner, between the resistors and the cap). I keep this as a reminder.

View attachment 663521

From that damage, I'm guessing that there was some intrusion into the nose cone AV bay. I've seen lawn darts in which there was no intrusion of the airframe into the AV bay cause little or no damage to the avionics.

 

[kjhambrick]

From that damage, I'm guessing that there was some intrusion into the nose cone AV bay. I've seen lawn darts in which there was no intrusion of the airframe into the AV bay cause little or no damage to the avionics.

Ooo, Ooo !

Do mine, Do mine !!

I suppose something intruded on the av-bay containing that AltAcc in the middle



-- kjh

(*) actually it was the av-bay forward bulkhead and the payload airframe and the nose cone and a bunch of hard, unforgiving Ocotillo soil

 

[Spacedog49Krell]

Here's what happens to a circuit board under high Gs. This is an Eggtimer Apogee that came down in a rocket from about 4000 feet. Probably going 4-500 fps when it hit. It buried the nosecone about 8" deep, so that's the distance the acceleration took place over. You can calculate the force. Almost all of the through-hole components were sheered off. The top of the baro chip was popped off (lower right corner, between the resistors and the cap). I keep this as a reminder.

View attachment 663521

Plugging in data recorded from my impact study, a terminal velocity of about 471 ft/sec from 4,000 ft, this is what 3,000 to 4,000 G's of deceleration looks like. There is bending, intrusion, and crushing actions along with the high G's. An approximate stopping time of 4 milliseconds, excluding all crush zone delays.

 

[Spacedog49Krell]

That does make alot of sense. I never would have thought about it like that, but I can totally see how that would be true. I know I said I was going to hold off on the gps and the other computer components for now, but I've seen many folks that seem to have problems with good, consistent gps. This is certainly a concern because I don't want to have to worry about packet loss and flawed data packets. While I know that how the gps system is physically installed in the rocket is a major component to good reception (ie not in a solid carbon fiber frame unless there is an antenna patch, antenna cutout, etc.), what other things cause these gps related issues? Is it a ground antenna thing (what signals are commonly operated off of and is it because people need to triangulate) or is it the actual gps module itself that struggles with either high velocity, acceleration, or altitude (or all of these combined)?

Can something like the LORA gps modules transmit gps location and live telemetry to a ground station, or is it solely for gps and I would need another unit for live telemetry values?

Thanks.

I have not flown a GPS. My ground testing is still in development. There are velocity and altitude limitations for most GPS systems. There are unlocked systems, but they are expensive. The altitude for my GPS is 18km with a velocity limit <Mach 1.45.

The location of the GPS antenna can be critical. Side view antennas can experience data stream loss during high spin rates. I'm testing a vertical view antenna position for flight, transitioning to a side view after parachute deployment.

 

[Dominic Bleacher]

I have not flown a GPS. My ground testing is still in development. There are velocity and altitude limitations for most GPS systems. There are unlocked systems, but they are expensive. The altitude for my GPS is 18km with a velocity limit <Mach 1.45.

The location of the GPS antenna can be critical. Side view antennas can experience data stream loss during high spin rates. I'm testing a vertical view antenna position for flight, transitioning to a side view after parachute deployment.

What are common methods and signals/frequencies used for GPS tracking? I know people often use several large antennas. I believe I have heard of triangulating antennas for better positioning of the rocket. Are there any other methods that are common and efficient that I should be aware of? Do people often rent equipment as I imagine it is quite expensive for all of that ground equipment?

 

[Spacedog49Krell]

What are common methods and signals/frequencies used for GPS tracking? I know people often use several large antennas. I believe I have heard of triangulating antennas for better positioning of the rocket. Are there any other methods that are common and efficient that I should be aware of? Do people often rent equipment as I imagine it is quite expensive for all of that ground equipment?

Downlink frequencies used are 70cm Amateur band (license required) and 915MHz (no license). I have experimented with 2.4GHz over line-of-sight km distances. I used a matched transmitter and receiver set. It worked in open ground tests, but tree branches, brush, and crops blocked signals and once on the ground the transmitting distance was very short.