So, maybe I'll try a three-stager

JimJarvis50 said:

Next will be the fins, but it will be a while before that happens.

Jim

Click to expand...

Yep, it looks like it took a couple of months since I last posted on this thread. But, I've made some progress on what will be the second stage of this year's three stager. Recall that the upper portion of this stage is the recycled upper portion of my stabilization system test rocket with a couple wraps of carbon added over the fiberglass tube. Similarly, the lower part of the stage is a simple fin can that's designed just to do the job at hand. Nothing fancy. A few pics from the build are attached. All I need to do to complete this is to glue in the zipperless coupler and perhaps add a little cotronics to the leading edges of the fins. On the upper part of this stage, I remodeled the altimeter bay to use an EasyMega altimeter, since I will need tilt inhibition for the motor, and I added a couple additional switches for the staging electronics.

With this, the second and third stages are mostly complete, and I next need to work on the spinning fin can for the booster and then start assembling information for the Class 3 application. I feel like I'm pretty much on schedule.

Jim

JimJarvis50 said:

... simple fin can ... Nothing fancy ...

Click to expand...

That's quite an understatement. I hope to someday reach a level of building carbon fiber rockets like that. Keep up the good work

You're beating me . I have 3 "nothing new" fin cans to make!

Kip_Daugirdas said:

You're beating me . I have 3 "nothing new" fin cans to make!

Click to expand...

For another three-stager no doubt?

I'm down to one more.

Jim

JimJarvis50 said:

For another three-stager no doubt?

I'm down to one more.

Jim

Click to expand...

I'm going to leave 3 stagers to you! Two new sustainers and a stretched booster (6GXL). I hope to be at Black Rock twice this year!

JimJarvis50 said:

with a couple wraps of carbon added over the fiberglass tube.

Click to expand...

Jim I'm doing something similar with my longer 4" first stage booster. I'm planning on wrapping the top 30" of the FWFG tube with 2 wraps of 7oz unidirectional fiberglass cloth. I'm not so worried about it's strength as it's bending stiffness. I have to stick with fiberglass for radio transparency.

What weight/weave carbon did you use? Was it a standard 0/90 orientation at layup?

Thanks!

Kip_Daugirdas said:

Jim I'm doing something similar with my longer 4" first stage booster. I'm planning on wrapping the top 30" of the FWFG tube with 2 wraps of 7oz unidirectional fiberglass cloth. I'm not so worried about it's strength as it's bending stiffness. I have to stick with fiberglass for radio transparency.

What weight/weave carbon did you use? Was it a standard 0/90 orientation at layup?

Thanks!

Click to expand...

I suspect that what I used from 5.7 oz 2x2 twill. I seem to have a lot of nominal 6 oz carbon, which can vary a little in weight, but I think this batch was 5.7 oz. Just standard 0/90. This particular rocket (the second stage) needs to fly to around Mach 2 with the 3rd stage attached. It's possible that this is the only flight this rocket will ever see, so I based the upgrades on what I think are the needs for this flight.

Jim

Cool thank you for the info! Yeah I don't see my booster exceeding Mach 2 on an O3400. But it should see quite a bit more stress than the original 6 grain booster that uses an unaltered FWFG tube.

I had the three stager out today to get the stage weights and CG values and then start some preliminary simulations. Thought it might be nice to take a shot of the entire rocket. The first stage is on the left. It has a free-spinning fin can. I will need to reduce the fin span from 9 inches to 7 inches. The stabilization spool is next, followed by the new second stage. The 3" sustainer (sitting on its transition interstage coupler) has flown on my two previous three-stage attempts and many other flights.

The motors will be N5800 / N1560 / M745 and the simulation suggests 160K should be possible. The entire rocket is 23' tall, weighs 51# (no motors) and 131# with motors.

There are a few things yet to complete, but one big accomplishment has been to get all of the sections lined up, and then "keys" installed so that none of the sections can rotate relative to each other. This required keys in 7 locations along the air frame.

Jim

JimJarvis50 said:

Yep, it looks like it took a couple of months since I last posted on this thread. But, I've made some progress on what will be the second stage of this year's three stager. Recall that the upper portion of this stage is the recycled upper portion of my stabilization system test rocket with a couple wraps of carbon added over the fiberglass tube. Similarly, the lower part of the stage is a simple fin can that's designed just to do the job at hand. Nothing fancy. A few pics from the build are attached. All I need to do to complete this is to glue in the zipperless coupler and perhaps add a little cotronics to the leading edges of the fins. On the upper part of this stage, I remodeled the altimeter bay to use an EasyMega altimeter, since I will need tilt inhibition for the motor, and I added a couple additional switches for the staging electronics.

With this, the second and third stages are mostly complete, and I next need to work on the spinning fin can for the booster and then start assembling information for the Class 3 application. I feel like I'm pretty much on schedule.

Jim

Click to expand...

Picture3 looks like you have peel ply laid down over CF...then picture 4 has the texture I associate with peel ply after it has been removed.
How did you get that smooth finish on picture 5?
Is there an overcoat of epoxy on the peel ply texture, or a clear urethane or something?

MaxQ said:

Picture3 looks like you have peel ply laid down over CF...then picture 4 has the texture I associate with peel ply after it has been removed.
How did you get that smooth finish on picture 5?
Is there an overcoat of epoxy on the peel ply texture, or a clear urethane or something?

Click to expand...

It's a bit of a process. Basically, I paint on six thin layers of epoxy, sanding lightly between each. Then, I try to sand each fin and fillet area flat. If there are a few low areas I can't get to with sandpaper on a board or a dowel, I use some flexible(?) sand paper on a sponge until the entire surface is sanded. I used to go down to 600 wet sand in the process, but now I usually go 120 and 240 wet and call it good. Last step is to wipe on a thin layer of epoxy and then wipe most all of it off (until it literally feels dry to the touch). It leaves a reasonable shine and doesn't require any finish sanding.

Jim

Edit - The finish in the picture you mentioned is a fairly abbreviated process relative to what I used to do (but it gives OK results). If you want to take the time, it's possible to get a pretty nice bare epoxy finish. The pics are a couple of rockets I did some years back. One of them is the current third stage (although it doesn't look quite so good anymore).

I've made some progress on the flight profile for this year and on the programming of the various flight computers. I usually post it here for review, although I don't often get many comments. I'd again like some help looking this over, and for encouragement, let me just say that I make a mistake about half the time that I do this, so the opportunity to actually find something wrong is real.

So, a picture of the flight profile is attached along with the programming specifics for each of the four sections containing flight computers. Again, the rocket will have active roll and vertical stabilization located between the 1st and 2nd stages. Roll control will be active at launch. Vertical stabilization will begin after 1st stage separation up to the time of the ignition of the motor in the second stage. Things go from there to a predicted apogee of 167K feet, with apogee deployment (for a nominal flight) by timers.

This year, there are a couple of new issues related to the EasyMega's in the upper stages. One issue was identified by Kip. If I understand the issue correctly, "after motor burnout #1" means after burnout 1 but before burnout 2. Therefore, if there is an event that may potentially occur after either the first or second burnouts, then you can't set an "after motor burnout" value. There are some programming steps I've taken related to this, but I don't really know if they are necessary.

The second thing is the handing of tilt detection. For various reasons, I believe the accuracy of the tilt measurement will be better for the EasyMega in the 2nd stage relative to that in the 3rd stage. So, I'm going to try and rely more heavily on the 2nd stage tilt value and relax the tilt criteria in the 3rd stage. To compensate, I will plan to light the 3rd stage motor sooner than I otherwise would, while the rocket is still above Mach.

If you spot anything that looks fishy, or have any suggestions, please reply.

Jim

I'm wondering about your pyro fire times at .1 & .05, why so short? I use 1 second, perhaps I have been setting mine to long?
Greg

rms said:

I'm wondering about your pyro fire times at .1 & .05, why so short? I use 1 second, perhaps I have been setting mine to long?
Greg

Click to expand...

I believe the 0.05 value is the default setting (at least it's the value shown in examples in the instruction manual). For ematches, I think it's plenty long, although I'd be curious what others think about that. With LiPo's, which are required for this altimeter, I think it is good to minimize the firing duration just in case the igniter doesn't go open.

Jim

Looks good to me!

PS I used .05 for all of my stuff too. Haven't had an issue.

My only concern with the 'after motor' is if the motor chuffs mid burn and the Easy registers that as burnout and ignition of the next motor. It's an unlikely scenario with commercial loads but it could happen.

Kip_Daugirdas said:

My only concern with the 'after motor' is if the motor chuffs mid burn and the Easy registers that as burnout and ignition of the next motor. It's an unlikely scenario with commercial loads but it could happen.

Click to expand...

That's a very good point. Chuffs are difficult to deal with in staging, but I think I need some changes even using commercial motors. Just documenting for myself ....

- For the Raven apogee channel in the spool, I could just use time for separation (same as activation of yaw/pitch). As long as the N5800 burns inside of 6 seconds, it would be fine, although it would do the stage separation and the yaw/pitch activation at the same time. Would be nice to avoid that. I wonder if you can add a delay to a timer value on the Raven? You would think I would have avoided this error since it was the failure mechanism for the flight last year.

- For the EasyMega in the 2nd stage, Channel A, I can omit the "after motor 1" because a chuff would be 2 burnouts and (I guess) would cause the second stage motor not to light. I could just use time without the burnout number and tighten up the altitude check a little in case the motor doesn't re-light.

- For the EasyMega in the 3rd stage, a chuff could cause the 3rd stage motor to light early. I can add T>23 (the expected 2nd stage burnout time) so that the motor wouldn't be able to light any earlier than in the intended flight plan.

Keep looking! There are more errors to find.

Jim

JimJarvis50 said:

I wonder if you can add a delay to a timer value on the Raven?

Click to expand...

To the best of my knowledge, delays are implemented as extra time once all other conditions become true. (It doesn't matter if the conditions become false again while the delay is happening as far as I know.) So you could set flight time > Tval and add a delay to that, and it should be the same as just setting time > Tval+delay in the first place, and effectively lets you use two different Tvals. You can confirm that by using test mode.

By the way, another Raven trick I discovered when working on our 100K flight was attaching one igniter to two channels, basically wire-oring the conditions. I used that for barometric apogee for apogee below 32K (second stage failed to ignite) and accelerometer apogee plus delay for altitudes above the barometric sensor limit (because I couldn't use a pure timer with the stock firmware, needed more than 51.2 seconds.)

mikec said:

By the way, another Raven trick I discovered when working on our 100K flight was attaching one igniter to two channels, basically wire-oring the conditions. I used that for barometric apogee for apogee below 32K (second stage failed to ignite) and accelerometer apogee plus delay for altitudes above the barometric sensor limit (because I couldn't use a pure timer with the stock firmware, needed more than 51.2 seconds.)

Click to expand...

I have the single ematch approach incorporated into the plan in two places where using multiple ematches is difficult. One is the third stage EasyMega, which uses a common ematch for a separation charge with Channels B and C. In this case, it is only possible to run one set of wires to the separation charge. The second is also the third stage EasyMega where a common ematch is connected to Channel D (baro apogee if a motor doesn't light) and one of the apogee timers. In this case, it's difficult to use two matches within my high altitude deployment charge tubes. This one isn't listed in the plan, but I'll add it so that the plan is as complete as possible. The common ematch between the EasyMega and timer outputs works as long as the polarity is correct, even though they operate on different voltages.

I think you're right about the Raven delay adding to the timer value. The only issue is that with the high altitude firmware, the timer operates on whole-number seconds. So, setting Tval > 5, for example, will actually trigger the channel at 6 seconds. So, the question would be, are you adding the delay to 5 seconds or 6? Easy enough to test.

Jim

I noticed that the delay between the "light motor" event on the flight profile graph and the motor coming up to pressure and providing thrust is a lot longer for the third stage than the second stage. Is that based on experience with the two motors and/or experience lighting at altitude?

boatgeek said:

I noticed that the delay between the "light motor" event on the flight profile graph and the motor coming up to pressure and providing thrust is a lot longer for the third stage than the second stage. Is that based on experience with the two motors and/or experience lighting at altitude?

Click to expand...

I've lit quite a few N1100's and M745's at altitude. The N1100 doesn't seem to take very long after the ignition signal. The N1560 should be similar - just another grain - so I've allowed a couple of seconds. It won't be all that high up. The M745 is pretty hard to light even on the ground. Two years ago, it took 6 seconds at altitude, although it was higher in that flight than in the current (I'm lighting it earlier and at a faster speed to minimize weathercocking). I had another flight that was a bit lower than took 4 seconds. So, I allowed 4 seconds to come up to pressure in the flight plan, but if it takes a little longer, that would be OK. I do wonder what the implications are for trying to light the motor just over Mach 1 versus at perhaps 500 ft/s in previous flights.

Jim

JimJarvis50 said:

I've lit quite a few N1100's and M745's at altitude. The N1100 doesn't seem to take very long after the ignition signal. The N1560 should be similar - just another grain - so I've allowed a couple of seconds. It won't be all that high up. The M745 is pretty hard to light even on the ground. Two years ago, it took 6 seconds at altitude, although it was higher in that flight than in the current (I'm lighting it earlier and at a faster speed to minimize weathercocking). I had another flight that was a bit lower than took 4 seconds. So, I allowed 4 seconds to come up to pressure in the flight plan, but if it takes a little longer, that would be OK. I do wonder what the implications are for trying to light the motor just over Mach 1 versus at perhaps 500 ft/s in previous flights.

Jim

Click to expand...

Jim,

Do you use anything to seal up the nozzle on your staged motors? Like maybe using aluminum foil tape (or Kapton tape) as a burst membrane? I am just thinking about the low pressure area created immediately behind a rocket traveling at speed. I was wondering if that will tend to suck out some of the ignitor material and make it more difficult to light a motor. Not to mention also being at high altitude with lower atmospheric pressure.

Vern

VernK said:

Jim,

Do you use anything to seal up the nozzle on your staged motors? Like maybe using aluminum foil tape (or Kapton tape) as a burst membrane? I am just thinking about the low pressure area created immediately behind a rocket traveling at speed. I was wondering if that will tend to suck out some of the ignitor material and make it more difficult to light a motor. Not to mention also being at high altitude with lower atmospheric pressure.

Vern

Click to expand...

I have caps over the ends of the motors but they aren't gas tight. This year's versions in the pics. I also typically have significantly more igniter material than you might use on the ground - maybe 4x more - a combination of magnalite and "slower" igniters for the M745. I don't know how to do that in combination with a sealed motor.

Jim

Note that the cap on the left doesn't yet have a hole in it for inserting the igniter, but it will at some point.

Just to document, here is the current programming for the three stage flight. Per Kip, I have revised the logic to deal with potential motor chuffs and to rely less on motor burnout count, although I don't see how to avoid using burnout 2 for the third stage. I also confirmed with Keith that "After Motor #1" actually means "between motor burnout #1 and motor burnout #2, if there is a second burnout". Very important to recognize this, as it is different than for the Raven, which is just "after burnout #1 to infinity". Also, per mikec, added a delay to a T>Tval time based on testing.

I'm sure there are still errors to find here, but hopefully less of them now.

Jim

You know Jim, seeing all the work that you have done on this project reminds me of a scene in the movie "What about Bob?".


I am amazed at the work that you have done and documented for those of us to consider. I nominate you for the Hobby Rocketry Hall of Fame.

Sorry if this has already been stated, but is this code Open Source so that others can build upon or is it proprietary? For me, and perhaps a few others, I have to take "baby steps".



Greg

GregGleason said:

Sorry if this has already been stated, but is this code Open Source so that others can build upon or is it proprietary? For me, and perhaps a few others, I have to take "baby steps".

Greg

Click to expand...

Thanks Greg!

I assume you're talking about the stabilization system code? It's not open source, but it has been made available to others on a limited basis, including for potential commercial use.

Jim

JimJarvis50 said:

I have caps over the ends of the motors but they aren't gas tight. This year's versions in the pics. I also typically have significantly more igniter material than you might use on the ground - maybe 4x more - a combination of magnalite and "slower" igniters for the M745. I don't know how to do that in combination with a sealed motor.

Jim

Note that the cap on the left doesn't yet have a hole in it for inserting the igniter, but it will at some point.

Click to expand...

Hi Jim,

Have you looked into head end ignition?

JimJarvis50 said:

Also, per mikec, added a delay to a T>Tval time based on testing.

I'm sure there are still errors to find here, but hopefully less of them now.

Jim

Click to expand...

Why do you have T>Tval and T<Tval on the Easy for stage events?

mpitfield said:

Hi Jim,

Have you looked into head end ignition?

Click to expand...

My very strong preference is not to use head end ignition - at least not with my current electronics setup. One procedure that I use when prepping the rocket is to do an "all-up" test of the electronics. Basically, everything is turned on, just as it would be on the pad, except that the igniter is not in the motor. If the test is successful, you turn everything off, put the rocket on the rail, and proceed with the launch. This is my last line of defense against a motor lighting prematurely. Since you can't remove the igniter with head end ignition, it is not possible to do the all up test. At some point, I may change my mind with suitable remote switching, but I'm not there yet, and carbon rockets don't help.

Jim

Kip_Daugirdas said:

Why do you have T>Tval and T<Tval on the Easy for stage events?

Click to expand...

The purpose of having both is to set a narrow window for when the 2nd and 3rd stage motors could light. The T<Tval basically "closes the window" on the altitude check. If you look at the settings for the 2nd stage motor, for example, without T<Tval, the motor could light even if the rocket doesn't reach the altitude check value of 2,200 meters until well after the intended trigger time. It is possible for that to happen. With T<Tval set, the logic is "light the motor at 11 seconds if the altitude is above 2,200 meters, but if the altitude doesn't reach 2,200 meters by 12 seconds, then never light the motor". Basically, you need T<Tval for a valid altitude check if you are using time as the trigger.

I think I need to change the 3rd stage T<Tval to something like 32 seconds instead of 35, since it is not my intent to have a five-second window. Thanks for making me look at this.

It is possible to instead use altitude or even velocity as the trigger. I want the second stage to trigger at 2,600 meters, so I might have said "light the motor at height above 2,600 meters if T<Tval", and then pick a value for Tval that is a few seconds past the expected time to that altitude. That would also be a valid altitude check. My preference has moved towards using time as the trigger rather than sensor or calculated values.

Jim