My first questions; ...

[cautery]

...please be gentle!

1) Has anyone thought about or implemented a common "power bus" in their avbay? It seems logical (to me) to do so, but I have zero HPR experience. Seems like the benefits are many assuming your avionics are compatible.

It's one of those decisions that I need to make on the front end of the avbay design.

In my case, I am using Altus Metrum as the main vendor: TeleMega v5.0, and EasyMini v2.0.

Since both of these flight computers can function on 3.7vdc LiPo, a common power bus and ground plane seem reasonable.

a) Adds more redundancy: We use dual recovery hardware, but then power each with a single cell/battery. That doesn't seem like best practices for me, UNLESS risk is accepted to shave a few more grams by NOT having redundant power. In which case, you might as well go with a single system. To have redundant batteries with individual power buses requires 4 cells/batteries. With a common power/batt bus and ground plane, you can provide redundant power to both computers (and in my case all charges) with only the 2 cells/batteries you were going to use in the first place (caveat in 2)

b) Weight: You get redundant power at less weight (using two cells/batts that can power the entire load by themselves). Constructed properly, you could actually implement redundant power/ground buses/planes and still save a bunch of weight (IAW: you'd still have TWO switches, but each switch would turn on BOTH systems. Failure Case? Bad switch, failure of a conductor or connection somewhere.)

c) MANY ways to implement. Easy way is to simply use sufficiently sized bus wire in twisted pair with multiple connectors, but you could ALSO get creative and do it with double-sided (one or more copper-clad as required) PCBs (or custom etched boards). Use PCB strips with sufficient copper weight to provide equivalent wire size. I'm thinking a triangular or square tube as wide as the widest avionics board. Power on one side (likely inside) and ground (likely outside for several reasons on the other. Connectors soldered to the board for twisted pair harnesses to the avionics assemblies. Or build the tube from CF sheet and run the buses through the center bonded to the back of the CF strips.

d) The tube (I prefer the triangle in theory) forms the core of the avbay structure, mounting base for avionics & batteries, and I'm seeing a way to use composite rods with threaded metal tips bonded to them to carry power/ground to the pyro charges with as few as 3 rods and only three penetrations through the bulkheads (except perhaps an penetration for an antenna passthrough or an external antenna connection.

e) Designed properly, you could make it a module that could be moved from one diameter to another airframe.

f) If you can make the tube "hinged", you could size it to accommodate the entire power bus and batteries INSIDE, and the combination of a continuous ground plane (or CF), and/or twisted pair, can help significantly reduce/eliminate common mode and general RFI/EFI to the radio(s) and GPS. Hinged side is more weight, but cleaner, and moves more mass closer to the center-line of the air-frame.

g) ALL that metal that you use in the ground plane/bus adds to the ground planes on the individual PCBs, thus providing a much better return path for the antennas in the unit, thus generally improving their performance.

So many options... this is just a few off my brain-storming list.

2) Does anyone other than the min diameter folks and altitude chasers ever attempt to design to "specifications to accomplish mission, survive, and fly again" rather than "specifications to avoid all failure cases anticipated regardless of probability"?

I've been studying a lot of builds both here and elsewhere. It seems like there is a definite propensity to "over-build" resulting in a lot more mass than "necessary" and frankly a waste of thrust! (For example, using a harness rated 2 or 3 times higher than required for a drogue chute deployed at apogee, a main harness sized too large for the forces it will see, or any harness that is much longer than required)

3) Aerodynamics and physics...

a) How many actually think about aerodynamics beyond CP & CG. Examples: Penetrations IN air-frame, protrusions FROM air-frame, airfoil considerations in fins beyond minimal leading edge beveling, et al.

b) How many look deeper into the physics as they apply. Examples: RFI/EFI, mass locations relative to air-frame center-line and how this affects trajectory, et al.

Have a wonderful week(end)!

 

[rfjustin]

1. IMO altimeters should be truly independent/redundant systems for our use case.

2. Overbuilding is common because its an expensive hobby for one. I'd rather overbuild a little bit and succeed than cut back to the ragged edge and fail.

3. You can go as deep as you want on the aerodynamics and physics fronts, but getting some HPR hands on experience first will be key. Go to launches network with folks, see what works for them, and enjoy the ride.

Best,

 

[Rocketjunkie]

Each piece of electronics should have it's own battery. This prevents a battery or a single electronic failure from taking out ALL the electronics. No good to have a backup if a battery failure kills everything!

 

[cautery]

1. IMO altimeters should be truly independent/redundant systems for our use case.

I agree. I obviously expressed myself poorly. The "common" power system I envision would satisfy "full redundancy" as you define it. You could have one battery fail, and both systems would still function. You could have any part of one bus fail and the other would serve both systems. You could have one battery AND one bus fail and both systems still would get power. Just 2 batteries instead of 4.

2. Overbuilding is common because its an expensive hobby for one. I'd rather overbuild a little bit and succeed than cut back to the ragged edge and fail.

Believe me, I am just getting started, so I am becoming intimately aware of how expensive it is. Gotta say, it looks like a bargain compared to some of my other hobbies (present and past).

I am absolutely not talking about going anywhere near the ragged edge for the forseeable future. Was just curious.

3. You can go as deep as you want on the aerodynamics and physics fronts, but getting some HPR hands on experience first will be key. Go to launches network with folks, see what works for them, and enjoy the ride.

Absolutely, I plan to stay pretty conventional and conservative for the time being. No benefit to building beyond mission. And mission #1 is getting a cert flight ready.

Really appreciate your response. I've seen some of your videos on YT.

 

[cautery]

Each piece of electronics should have it's own battery. This prevents a battery or a single electronic failure from taking out ALL the electronics. No good to have a backup if a battery failure kills everything!

I agree. I expressed myself poorly.

As I said to Justin above, "The "common" power system I envision would satisfy "full redundancy" as you define it. You could have one battery fail, and both systems would still function. You could have any part of one bus fail and the other would serve both systems. You could have one battery AND one bus fail and both systems still would get power. Just 2 batteries instead of 4."

 

[OverTheTop]

I have thought about a power bus system for years but it usually ends up easier just to have relevant batteries for each piece of hardware. The different battery requirements for different altimeters and telemetry systems add to this problem. Inertia has won on this currently for me.

Yes, I do consider internal EMC/EMI when designing. EMC testing is also what I have to do once my products are designed before being released onto the market. Ground planes used where necessary and ground testing is done to confirm everyone plays well together. I do keep Tx antennas well away from sensitive GNSS receivers and have seen an increase in time to lock when this is not done, due to receiver desensitisation or timing jitter being introduced. This gets worse, of course, as the Tx power goes up. FYI my next flight will have three telemetry Tx systems on board.

I enjoy diving into aerodynamics and have a reasonable working knowledge, but given I don't chase maximum altitude optimisation my birds generally just have beveled edges where appropriate. Since the rockets are generally operating near zero AoA adding airfoils does not usually offer significant gains.

 

[cautery]

I have thought about a power bus system for years but it usually ends up easier just to have relevant batteries for each piece of hardware. The different battery requirements for different altimeters and telemetry systems add to this problem. Inertia has won on this currently for me.

Yes, I do consider internal EMC/EMI when designing. EMC testing is also what I have to do once my products are designed before being released onto the market. Ground planes used where necessary and ground testing is done to confirm everyone plays well together. I do keep Tx antennas well away from sensitive GNSS receivers and have seen an increase in time to lock when this is not done, due to receiver desensitisation or timing jitter being introduced. This gets worse, of course, as the Tx power goes up. FYI my next flight will have three telemetry Tx systems on board.

I enjoy diving into aerodynamics and have a reasonable working knowledge, but given I don't chase maximum altitude optimisation my birds generally just have beveled edges where appropriate. Since the rockets are generally operating near zero AoA adding airfoils does not usually offer significant gains.

I get that. I usually have to MAKE myself stop tweaking designs at some point, or no prototyping or building gets done.

My past lives and my years in networking and amateur radio keep EMI/RFI right at the top of the list.

Gotcha.... I have little to no appreciation for rocketry aerodynamics.... My experience is limited to rotary wing and fixed wing stuff.

Appreciate the response!! Thank you.

 

[OverTheTop]

My experience is limited to rotary wing and fixed wing stuff.

If you are into rotary wing aerodynamics I think this is the book I really liked on the subject:

AIAA Aerospace Research Central

It discusses the intricacies quite well. Things like there is actually a region of flow over the blades during flight where the flow goes from the rear of the blade to the front .

 

[cautery]

If you are into rotary wing aerodynamics I think this is the book I really liked on the subject:

AIAA Aerospace Research Central

It discusses the intricacies quite well. Things like there is actually a region of flow over the blades during flight where the flow goes from the rear of the blade to the front .

LOL! Yup.... retreating blade stall and the failure case where the retreating blade's outboard section twists OFF were head scratchers in flight school. I absolutely loved aerodynamics. Heck I loved instruments...

Thank you for the tip & the response! Added it to my pleasure reading list. Gonna focus on rocketry for the foreseeable future.

 

[manixFan]

Several observations:

Power Bus: I witnessed an incredibly complex rocket that had a common power bus fail when the mounts for the batteries failed on takeoff and every system on board died. At least that's what a best guess failure analysis concluded, as the rocket came in ballistic from about 100,000 feet and was not recovered. There were several trackers and telemetry systems and they all failed immediately at launch, which lead to the conclusion on the power loss. Ever since then I've been of the opinion every system should have it's own power source.

Overbuilding: One of the sequences that I see goes something like this: a flyer overbuilds the fin can and then needs a bigger chute because the rocket is too heavy for the original chute, and then, heck, he should beef up the quick links, and dang, that U-bolt on the bulkhead looks thin, and so on. And worse, all that weight in the fin can means it needs nose weight, and an even bigger chute. Pretty soon the rocket weighs far more than a nominal build, which puts additional stress everywhere, and it ends up needing larger motors for that magic 5:1 thrust ratio and enough speed off the rail. I think flyers way over estimate the stresses on a normal rocket and actually add more stress on it by over building and greatly increasing the weight and as a result, the stresses. I have a hard time understanding the extent of overbuilding sometimes. But it's just a hobby - so as long as it makes that builder happy, (and of course does not present a safety issue), then why should I care? But it can be like watching a slow car crash.

Aerodynamics: I've built a number of 38mm and 54mm MD rockets that are were designed to go fast and high. On the last several I've built, none of them have any kind of opening in the airframe other than vent holes. I use magnetic switches and A/V bays that are built into couplers that are glued into the upper airframe. None of my rockets have ever used a switch band - it just seems like bad aerodynamics. They are tower launched so no buttons in the airflow. My next batch will all be single tube with head-end deployment. The airframes are carbon fiber and use surface mounted fins with just proper bonding techniques to keep them on - no tip to tip. I'm of the opinion that properly designed and aligned fins do not undergo tremendous stresses in a nominal flight. I routinely fly over Mach 2 with my 54mm birds and have never lost a fin or had any issues, even on landing. I'm not trying to set any records, other than my own personal bests, but I also get a lot of bang out of even modest motors. However, with my normal 'sport flyers', its just so much easier and simpler to not worry about the aerodynamic impacts of rail buttons on a 38mm rocket, or screw heads that stick out of the body tube, or big fins that would flap like a flag in a stiff breeze at anywhere near Mach. Sometimes it's just for the fun of it, or the looks of it.

Somewhat off topic but related to flying complex flights, I've learned 'go fever' almost always leads to bad outcomes. Whenever I've flown with a feeling of being less than 100% confident, I've almost always regretted it. Learning to stand down when something is marginal or not as expected seems so simple, but yet is really hard to do. Just recently someone I know lost a very nice and expensive rocket. They were having trouble with the tracker but flew it anyway. The tracker never came back online and that was the end of it. In retrospect it was clearly not a good idea to launch, but when you've traveled hundreds of miles and have been working for months on that flight, it's hard to step on the brakes and take it off the rail. And it seems the more time and energy invested in a flight, the more likely go fever is to take over a reasoned approach.

Sorry for the missive, hopefully some food for thought.


Tony

 

[cautery]

Several observations:

Power Bus: I witnessed an incredibly complex rocket that had a common power bus fail when the mounts for the batteries failed on takeoff and every system on board died. At least that's what a best guess failure analysis concluded, as the rocket came in ballistic from about 100,000 feet and was not recovered. There were several trackers and telemetry systems and they all failed immediately at launch, which lead to the conclusion on the power loss. Ever since then I've been of the opinion every system should have it's own power source.

Overbuilding: One of the sequences that I see goes something like this: a flyer overbuilds the fin can and then needs a bigger chute because the rocket is too heavy for the original chute, and then, heck, he should beef up the quick links, and dang, that U-bolt on the bulkhead looks thin, and so on. And worse, all that weight in the fin can means it needs nose weight, and an even bigger chute. Pretty soon the rocket weighs far more than a nominal build, which puts additional stress everywhere, and it ends up needing larger motors for that magic 5:1 thrust ratio and enough speed off the rail. I think flyers way over estimate the stresses on a normal rocket and actually add more stress on it by over building and greatly increasing the weight and as a result, the stresses. I have a hard time understanding the extent of overbuilding sometimes. But it's just a hobby - so as long as it makes that builder happy, (and of course does not present a safety issue), then why should I care? But it can be like watching a slow car crash.

Aerodynamics: I've built a number of 38mm and 54mm MD rockets that are were designed to go fast and high. On the last several I've built, none of them have any kind of opening in the airframe other than vent holes. I use magnetic switches and A/V bays that are built into couplers that are glued into the upper airframe. None of my rockets have ever used a switch band - it just seems like bad aerodynamics. They are tower launched so no buttons in the airflow. My next batch will all be single tube with head-end deployment. The airframes are carbon fiber and use surface mounted fins with just proper bonding techniques to keep them on - no tip to tip. I'm of the opinion that properly designed and aligned fins do not undergo tremendous stresses in a nominal flight. I routinely fly over Mach 2 with my 54mm birds and have never lost a fin or had any issues, even on landing. I'm not trying to set any records, other than my own personal bests, but I also get a lot of bang out of even modest motors. However, with my normal 'sport flyers', its just so much easier and simpler to not worry about the aerodynamic impacts of rail buttons on a 38mm rocket, or screw heads that stick out of the body tube, or big fins that would flap like a flag in a stiff breeze at anywhere near Mach. Sometimes it's just for the fun of it, or the looks of it.

Somewhat off topic but related to flying complex flights, I've learned 'go fever' almost always leads to bad outcomes. Whenever I've flown with a feeling of being less than 100% confident, I've almost always regretted it. Learning to stand down when something is marginal or not as expected seems so simple, but yet is really hard to do. Just recently someone I know lost a very nice and expensive rocket. They were having trouble with the tracker but flew it anyway. The tracker never came back online and that was the end of it. In retrospect it was clearly not a good idea to launch, but when you've traveled hundreds of miles and have been working for months on that flight, it's hard to step on the brakes and take it off the rail. And it seems the more time and energy invested in a flight, the more likely go fever is to take over a reasoned approach.

Sorry for the missive, hopefully some food for thought.


Tony

Wise counsel in all respects.

Once upon a time, it was my job to corral some of the best men while they fixed broken birds that I subsequently had to fly and basically TRY to break them, so I could give it back to the line pilots.

I build and maintain everything like we did aircraft. It's just who I am.

Thank you very much for the considered reply!

 

[mtnmanak]

While I do see a lot of overbuilding of rockets here on TRF, I think the trick is to get comfortable with a balance. Figure out where the stress points on your rocket are going to be (your studies in aerodynamics will be well served here) and beef up those points appropriately without going overboard. Things like understanding that an external fillet should not be the main structural holding force on through-the-wall fins (so, if you build the internal part of the fin can right, you don't need 2 pounds of epoxy on your external fillets!).

Approaching Level 1 is the perfect time to perfect all these techniques while it is all still relatively small, cheap and light weight. When I first pursued HPR, I went and bought 2 x LOC IV kits and 2 x Apogee Zephyr kits and played around with them for quite a while. I built one "heavy", I built one "light" and then I built the other two somewhere in the middle and tried some of the techniques I read about on TRF. I built them with different recovery mechanisms, different motor retention techniques, etc. Over time, all four birds have flown many times (two of them are gone now - a CATO on a Zephyr a few years ago and a failed parachute on one of the LOCs a while back). And, the Zephyrs were both converted later to dual-deploy by adding a coupler and a payload bay, so those early birds also helped keep the learning curve to Level 2 shallower.

Biggest thing is, this is not a race. I love building rockets. I have built about 20 HPRs in the last year alone and have another 20 on the build pile (at least). So, take the time to dig deep into the hobby, get lots of parts and kits and learn more every day!

I am a proponent of keeping your AV bay as simple as you can. The more complex you make it, the more likely it is to fail. And, if you are going to overbuild anything, overbuild the structural parts of your AV bay. I can't count the number of times I have recovered a rocket to find the battery holder torn off, a 3D printed sled cracked in half, wires disconnected, etc. The AV bay has to endure a huge amount of acceleration at multiple points in the flight - build it simple and build it strong. You won't be able to avoid AV complexity when you get to airstarts, clusters, staging, etc, but, for now, two independent computers + two independent batteries = success!

 

[JoePfeiffer]

...please be gentle!

1) Has anyone thought about or implemented a common "power bus" in their avbay? It seems logical (to me) to do so, but I have zero HPR experience. Seems like the benefits are many assuming your avionics are compatible.
<snip>

a) Adds more redundancy: We use dual recovery hardware, but then power each with a single cell/battery. That doesn't seem like best practices for me, UNLESS risk is accepted to shave a few more grams by NOT having redundant power. In which case, you might as well go with a single system. To have redundant batteries with individual power buses requires 4 cells/batteries. With a common power/batt bus and ground plane, you can provide redundant power to both computers (and in my case all charges) with only the 2 cells/batteries you were going to use in the first place (caveat in 2)

True, but a battery and a connector is a really simple system that almost never fails. The real reason (IMHO) for redundant power on the two altimeters is so if one of the altimeters fails, it doesn't take the power supply for the other altimeter with it.

So you can't just have two batteries powering the bus, and two altimeters taking power off it. You also need isolation, which introduces its own failure modes. I'm thinking the total system is unlikely to be more reliable than simply having a battery on each altimeter.

b) Weight: You get redundant power at less weight (using two cells/batts that can power the entire load by themselves). Constructed properly, you could actually implement redundant power/ground buses/planes and still save a bunch of weight (IAW: you'd still have TWO switches, but each switch would turn on BOTH systems. Failure Case? Bad switch, failure of a conductor or connection somewhere.)

I don't see how it'll be lighter. You need the same total number of batteries.

e) Designed properly, you could make it a module that could be moved from one diameter to another airframe.

I think most of us are building our sleds to accommodate a variety of airframe sizes with our altimeter sleds already...

2) Does anyone other than the min diameter folks and altitude chasers ever attempt to design to "specifications to accomplish mission, survive, and fly again" rather than "specifications to avoid all failure cases anticipated regardless of probability"?

I've been studying a lot of builds both here and elsewhere. It seems like there is a definite propensity to "over-build" resulting in a lot more mass than "necessary" and frankly a waste of thrust! (For example, using a harness rated 2 or 3 times higher than required for a drogue chute deployed at apogee, a main harness sized too large for the forces it will see, or any harness that is much longer than required)

People keep saying that, but from the number of cracked fins on landing, and various structural failures on recovery system deployment I see, I doubt there's as much overbuilding as people say.

3) Aerodynamics and physics...

a) How many actually think about aerodynamics beyond CP & CG. Examples: Penetrations IN air-frame, protrusions FROM air-frame, airfoil considerations in fins beyond minimal leading edge beveling, et al.

b) How many look deeper into the physics as they apply. Examples: RFI/EFI, mass locations relative to air-frame center-line and how this affects trajectory, et al.

There are people who've looked into these things, and the result has pretty consistently been that it all matters much less than the variation in the thrust of a solid fuel motor.

 

[cautery]

While I do see a lot of overbuilding of rockets here on TRF, I think the trick is to get comfortable with a balance. Figure out where the stress points on your rocket are going to be (your studies in aerodynamics will be well served here) and beef up those points appropriately without going overboard. Things like understanding that an external fillet should not be the main structural holding force on through-the-wall fins (so, if you build the internal part of the fin can right, you don't need 2 pounds of epoxy on your external fillets!).

Approaching Level 1 is the perfect time to perfect all these techniques while it is all still relatively small, cheap and light weight. When I first pursued HPR, I went and bought 2 x LOC IV kits and 2 x Apogee Zephyr kits and played around with them for quite a while. I built one "heavy", I built one "light" and then I built the other two somewhere in the middle and tried some of the techniques I read about on TRF. I built them with different recovery mechanisms, different motor retention techniques, etc. Over time, all four birds have flown many times (two of them are gone now - a CATO on a Zephyr a few years ago and a failed parachute on one of the LOCs a while back). And, the Zephyrs were both converted later to dual-deploy by adding a coupler and a payload bay, so those early birds also helped keep the learning curve to Level 2 shallower.

Biggest thing is, this is not a race. I love building rockets. I have built about 20 HPRs in the last year alone and have another 20 on the build pile (at least). So, take the time to dig deep into the hobby, get lots of parts and kits and learn more every day!

I am a proponent of keeping your AV bay as simple as you can. The more complex you make it, the more likely it is to fail. And, if you are going to overbuild anything, overbuild the structural parts of your AV bay. I can't count the number of times I have recovered a rocket to find the battery holder torn off, a 3D printed sled cracked in half, wires disconnected, etc. The AV bay has to endure a huge amount of acceleration at multiple points in the flight - build it simple and build it strong. You won't be able to avoid AV complexity when you get to airstarts, clusters, staging, etc, but, for now, two independent computers + two independent batteries = success!

Thank you, sir! Really appreciate your insights and experience.

 

[cautery]

True, but a battery and a connector is a really simple system that almost never fails. The real reason (IMHO) for redundant power on the two altimeters is so if one of the altimeters fails, it doesn't take the power supply for the other altimeter with it.

So you can't just have two batteries powering the bus, and two altimeters taking power off it. You also need isolation, which introduces its own failure modes. I'm thinking the total system is unlikely to be more reliable than simply having a battery on each altimeter.


I don't see how it'll be lighter. You need the same total number of batteries.

I think most of us are building our sleds to accommodate a variety of airframe sizes with our altimeter sleds already...

People keep saying that, but from the number of cracked fins on landing, and various structural failures on recovery system deployment I see, I doubt there's as much overbuilding as people say.

There are people who've looked into these things, and the result has pretty consistently been that it all matters much less than the variation in the thrust of a solid fuel motor.

Thank you for taking the time to provide a considered reply! I appreciate it.

 

[OverTheTop]

So you can't just have two batteries powering the bus, and two altimeters taking power off it. You also need isolation, which introduces its own failure modes. I'm thinking the total system is unlikely to be more reliable than simply having a battery on each altimeter.

It can't be just connections. There needs to be diodes, switches, isolation and perhaps some form of management to keep everything well fed. Think about how they have more than one power bus in an aircraft, or spacecraft for that matter. It isn't just connecting everything to one bus and spreading it around.

These systems can be, and are, designed to be more reliable but there is a lot of analysis required (FMEA etc) to ensure you don't adversely impact reliability.

I don't see how it'll be lighter. You need the same total number of batteries.

Maybe. Depends on how many systems are being combined. The more electronics being fed the more opportunities to reduce the number of batteries, although their size may increase (load dependent). Remember the primary aim is reliability, not mass reduction.

 

[rocket_troy]

True, but a battery and a connector is a really simple system that almost never fails.

The caveat I'll include with that is: so long as you're not using cheap Chinese connectors ie. the varieties that use minimal strand wires with stiff PVC insulation.
That cost me on one flight big time.

TP

 

[Michael L]

1) Has anyone thought about or implemented a common "power bus" in their avbay? It seems logical (to me) to do so, but I have zero HPR experience. Seems like the benefits are many assuming your avionics are compatible.

I use redundant batteries, redundant dual deploy. and a tracker. I "designed" the board. Designed is in quotes because... drum roll please.. it's not rocket science to design a little board like these

On the left is the tracker in the nose cone bay - the purple board is the first prototype. There's a switch, two battery connections, and one output to the flight computer. On the right - Same configuration for the AV bay only there are two power boards and two EasyMini's. I used mag switches on all three. There's a 3D printed battery box on the back of the nose cone bay and two 3D printed battery boxes on back of the AV bay. Each box holds a pair of 350mAh batteries. The rocket it can lay out in the high Colorado Plateau desert all day and the tracker will still be talking. The problem with that is that I would still be looking for it if it was out there that long.

Here's one of the smaller battery boxes. It's pretty simple, a slot for the wires, a groove on both sides (top and bottom) that allows a tye-wrap to be used to hold the battery in. And two countersunk screw holes to attach it to the bay.

Screenshots of the design drawings

Board layout. The charge port is also a battery port. When I charge the batteries I unplug one, plug the charger into the board in that slot, swap, and charge battery #2. Nothing has to come out of the sled that way.

One of my goals is to come up with a power board that has the Hall Effect latch built in, I made another version of the board that has two outputs but that wasn't very well received at the club. The boards are small. It's easy enough to install two...

Here's the boards: https://oshpark.com/shared_projects/j3pX2dVk
I don't get anything if someone orders a board. Don't want anything either. If you want the Eagle design files I'll post them.

Here's the battery box(es): https://www.thingiverse.com/thing:4830421
It's parameterized so there are two f3d files (Fusion 360) as well as small and larger battery STL files. I've used PCTG+, PETG, and PLA to print these. They all work. PLA is fine. I used PETG in case it has to sit in the sun a long time.

 

[cautery]

I use redundant batteries, redundant dual deploy. and a tracker. I "designed" the board. Designed is in quotes because... drum roll please.. it's not rocket science to design a little board like these

On the left is the tracker in the nose cone bay - the purple board is the first prototype. There's a switch, two battery connections, and one output to the flight computer. On the right - Same configuration for the AV bay only there are two power boards and two EasyMini's. I used mag switches on all three. There's a 3D printed battery box on the back of the nose cone bay and two 3D printed battery boxes on back of the AV bay. Each box holds a pair of 350mAh batteries. The rocket it can lay out in the high Colorado Plateau desert all day and the tracker will still be talking. The problem with that is that I would still be looking for it if it was out there that long.

Here's one of the smaller battery boxes. It's pretty simple, a slot for the wires, a groove on both sides (top and bottom) that allows a tye-wrap to be used to hold the battery in. And two countersunk screw holes to attach it to the bay.

Screenshots of the design drawings

Board layout. The charge port is also a battery port. When I charge the batteries I unplug one, plug the charger into the board in that slot, swap, and charge battery #2. Nothing has to come out of the sled that way.

One of my goals is to come up with a power board that has the Hall Effect latch built in, I made another version of the board that has two outputs but that wasn't very well received at the club. The boards are small. It's easy enough to install two...

Here's the boards: https://oshpark.com/shared_projects/j3pX2dVk
I don't get anything if someone orders a board. Don't want anything either. If you want the Eagle design files I'll post them.

Here's the battery box(es): https://www.thingiverse.com/thing:4830421
It's parameterized so there are two f3d files (Fusion 360) as well as small and larger battery STL files. I've used PCTG+, PETG, and PLA to print these. They all work. PLA is fine. I used PETG in case it has to sit in the sun a long time.

Thank you for that! I appreciate your time and effort!

 

[manixFan]

...<snipped>...
There are people who've looked into these things, {effects of rail buttons, external switches, etc.} and the result has pretty consistently been that it all matters much less than the variation in the thrust of a solid fuel motor.

I would agree that's true on larger rockets, but lately I've been working in the realm of 38mm minimum diameter rockets that travel well above Mach, and the impact on adding rail buttons sims to about 2-5% of an impact on altitude (at least using my method). So maybe within the variability of motors and altimeter error, but still something I'd rather eliminate. Plus I don't like the asymmetric drag buttons induce.

And then there's this:



Tony

 

[cautery]

Plus I don't like the asymmetric drag buttons induce.

And then there's this:
View attachment 491670

Those are both things that will bug the ever-lovin' snot out of me... I may have to suck it up and deal with it.... But I don't want to.

 

[RocketRev]

I would agree that's true on larger rockets, but lately I've been working in the realm of 38mm minimum diameter rockets that travel well above Mach, and the impact on adding rail buttons sims to about 2-5% of an impact on altitude (at least using my method). So maybe within the variability of motors and altimeter error, but still something I'd rather eliminate. Plus I don't like the asymmetric drag buttons induce.

And then there's this:
View attachment 491670


Tony

Is that melting from air friction that I'm seeing? And is that paint that's pealed off as well?

Brad

 

[manixFan]

Is that melting from air friction that I'm seeing? And is that paint that's pealed off as well?

Brad

Yes, the melting was from air friction, and the paint delaminated as well. In the photo below I suspect the lower airframe wasn't prepped properly before painting because nearly all the paint was stripped off by the heat and friction at Mach+. I use brake caliper paint on my rockets and while it does suffer some damage, nothing like this.


Tony

DISCLOSURE: This is not my rocket, but I was involved in helping with the motor (P) and the flight and recovery: