What would some good engine combinations be?

[von Braun]

I recently finished an Estes Astron Midget with separate parts from Semroc,and I'm trying to decide what some good engine combos for it would be. I'm going to use 13 mm engines compressed into 1.75 inch 18 mm casings. The first stage will have to use A10-0T's that I'll need to order from Launch Pad 2000; would A3-4T's be good for a retainer,or is that not a long enough delay? I'm going to use 1/2A3-4T's also.

[Doug Sams]

I recently finished an Estes Astron Midget with separate parts from Semroc,and I'm trying to decide what some good engine combos for it would be. I'm going to use 13 mm engines compressed into 1.75 inch 18 mm casings. The first stage will have to use A10-0T's that I'll need to order from Launch Pad 2000; would A3-4T's be good for a retainer,or is that not a long enough delay? I'm going to use 1/2A3-4T's also.I frequently fly the A10-0T / ½A3-4T combo in my Midget fleet.

I've also tried the A3-4T. If you use a streamer, you should be OK. The delay will be a tad short, but the streamers don't unfurl with the same zipper-inducing-jerk of parachutes. It's important that the recovery system is set up to tolerate the early deployment.

Another sustainer to consider is the A8-5. They saw off nicely for this purpose :) And have a more optimum delay.

Make sure you scrape the sustainer nozzle in whichever motor you use.

Doug

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[von Braun]

Thanks,Doug. Should I scrape some of the clay out of the nozzle to make it bigger? I've been meaning to ask you that.

I'm also going to try a 1/4A3-3T retainer for test-flying. I thought about the A8-5 also.

-Steve

[von Braun]

I keep saying retainer when I mean sustainer.

[Doug Sams]

Should I scrape some of the clay out of the nozzle to make it bigger? Hi, Steve,

No. You're just trying to make sure it's clean, that there's no clay covering the BP which could prevent it from igniting.

Use the biggest drill bit which will fit into the hole, then give it a couple of twists. Tap the nozzle end on the table top, and if you get a bit of black dust out, you're done. Else, give it a couple more twists :)

Doug

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[von Braun]

Hi, Steve,

No. You're just trying to make sure it's clean, that there's no clay covering the BP which could prevent it from igniting.

Use the biggest drill bit which will fit into the hole, then give it a couple of twists. Tap the nozzle end on the table top, and if you get a bit of black dust out, you're done. Else, give it a couple more twists :)

Doug

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Hey Doug,I thought about something else. What if I sprinkled a few grains of BP on top of the booster stage propellant for a little extra spark to be sure the sustainer ignites? My brother,who does his own reloads,gave me a little jar of BP to use for some extra parachute push,and I thought about trying a little in a booster stage.

-Steve

[Doug Sams]

Hey Doug,I thought about something else. What if I sprinkled a few grains of BP on top of the booster stage propellant for a little extra spark to be sure the sustainer ignites? My brother,who does his own reloads,gave me a little jar of BP to use for some extra parachute push,and I thought about trying a little in a booster stage.Steve,

I've never tried that, but it's certainly something you can experiment with carefully, although it's a safety code violation, I believe, so you shouldn't do it at club launches.

The one experiment I've tried is painting pyrogen in the nozzle of the sustainer motors, but I didn't see any difference. Things worked about the same. In this case, the flash point of the pyrogen wasn't very low - it worked fine for homemade ignitors, but for staging it didn't seem to make much difference. It didn't seem to light particularly fast.

If you could some up with something with a lower flash point, that would help, but it would probably work best being placed in the nozzle of the sustainer rather than atop the booster grain.

A couple of items with low flash point are gasoline and flash powder. Gasoline is definitely a no-no http://forums.rocketshoppe.com/images/smilies/biggrin.gif And, having 0 experience with flash powder, I can only speculate.

Seems to me it would work best in a solution painted into the nozzle and let dry. But I suspect the low flash point properties would be altered by that process.

So, when it's all said and done, scraping the nozzle and getting a good tape coupling are my tried-and-true tips.

Doug

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[PaulK]

Hey Doug,I thought about something else. What if I sprinkled a few grains of BP on top of the booster stage propellant for a little extra spark to be sure the sustainer ignites? My brother,who does his own reloads,gave me a little jar of BP to use for some extra parachute push,and I thought about trying a little in a booster stage. -SteveThe way to use BP for this is to put some in the nozzle of the sustainer, and tamp it down with a small wood dowel.

[Mark II]

I really doubt that you will have any problems staging via the usual way without the use of any augmentation. Personally, I have never witnessed a staging failure with either mine or any other rockets. Yes, they happen, but apparently not all that often. And yes, I realize that I am going against conventional wisdom by saying that.

MarkII