Going for 100,000 Feet

Steve Shannon said:

I think any tail fairing, in order to have sufficient effect on airflow at transonic velocity will have to have some structural strength.
I don't think an internal coating of BP will have the effect you wish. Soaking the material with an oxidizer might. The BP coating would be easy and interesting to test though. I'd like to see it anyway.

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Yeah... It's the July 4 weekend. What a perfect time to test the concept.

EeebeeE said:

That would be very nice of you.

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Shoot me a message with your address and I'll get it in the mail tomorrow. It's a Performance Rocketry clamshell model and the shoulder isn't great, but a little work will make it go a long way. It's the graphite-infused gel coat, as well.

Hey, the price is right!

EeebeeE said:

Very interesting. I would think that the boattail is going to get pretty hot, though, and the metals allowed for something like that will readily transfer heat to the airframe, softening the epoxy and ultimately causing the boat tail to come loose.

If I use Cesaroni motors, I can use the Pro 54 Tapered Aft Closure and achieve at least some semblance of a boattail with something designed for the heat. It probably would not get all of the same performance, but I would have a much lower risk of failure from heat or the higher speed.

I may need to turn 1/16" off the forward end of the closure so it will fit into the transition to the booster, but that should not have an adverse impact on the retainer since it is the threads that are most important in retaining the nozzle. Of course the other option would be to fabricate a section of airframe that slips around the outside of the sustainer airframe, which would not be that difficult to do.

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EeebeeE said:

Just reread this. Some questions:
Is it acceptable to eject the boat tail without a recovery system?
Can the boat tail be constructed of some sort of flammable material so that it can incinerate at ignition of the sustainer?
Would an essentially pressure-fitted boat tail be prone to drag separation?

Hypothetically, since it is not subject to near as much heat, it could be made from paper or phenolic and closed completely shut, essentially transforming the sustainer into a boosted dart until the second stage fires. Motor ignition could either burn through the boat tail (which would be nearly instantaneous), incinerating it or blow it off. Either way, a paper product would be biodegradable at the worst, or nothing but ashes at the best, and it should not cause damage if it hit something on the ground.

Another benefit is that it would contain a small amount of air that should be richer in O2 than what would normally be at that altitude. That could help with sustainer ignition.

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I don't understand you concerns and comments.

If you design and implement a boattail properly, it doesn't get hot. A boattail is a drag reduction device to reduce the vacuum at the base of the rocket, and thus reduce the base drag. Boattails also reduce base heating by reducing exhaust gas recirculation.



https://www.aeropack.net/products.asp These products are commonly used and they don't heat up and fall off rockets. The Aeropac aluminum boattail retainers are male tapered devices that can be fitted into a matching tapered female socket transition piece on the top of the booster just like any boosted dart. Properly fitted, the sustainer will drag separate as soon as the booster thrust stops provided the sectional density of the sustainer is much greater than the sectional density of the burned out booster.

Additionally neither rocket motors or igniters can utilize or require atmospheric oxygen to function.

Bob,

Since this is minimum diameter, rear motor retainers will not work including boat tail retainers. The retention needs to be inside the airframe at the forward end. Aeropack makes those as well. Cesaroni makes an aft closure that is the same diameter as the outside of a FG airframe.

So the concept is to have a boat tail in place during the coast phase between stages to reduce drag and achieve a higher altitude before the second stage fires, but when the second stage fires, the tailcone is jettisoned.

So the question becomes, how do we safely jettison a tailcone that we have no intention of recovering? The idea of paper or paper mache is that it would be biodegradeable and would tumble to the ground. The other thought is that since it is jettisoned from 25,000' and is relatively small, perhaps we can build it so that it incinerates when the sustainer is fired so that pieces of it would harmlessly fall to the ground and degrade.

So I tested the concept. The BP went off like a flash...but it burned too quickly and did not ignite the paper airframe. Great image, though. Here is a photo and a video of the attempt.


[YOUTUBE]6hAQ0VCXHoY&feature[/YOUTUBE]

Hmm, cast your tailcone out of NC Lacquer......

If you are really going to have the tailcone burn I would suggest you contact the club where you are planning to launch. You don't want to just show up and have the RSO deny approving the flight.

M

Wouldn't you want the tailcone to still be there post second stage burn? Lower drag coasting then is good too, no?

What does a few degrees of off-vertical do to these altitude estimates? At what altitude/angle combination does horizontal dispersion become a significant issue?

N

Wingarcher said:

Wouldn't you want the tailcone to still be there post second stage burn? Lower drag coasting then is good too, no?

What does a few degrees of off-vertical do to these altitude estimates? At what altitude/angle combination does horizontal dispersion become a significant issue?

N

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Don't think it is possible to keep a tail cone in place on a MD rocket unless I can get a tapered retainer for the motor, which I have mentioned many times. The airframe is minimum diameter, so tail cones are exposed to motor burn.

If there is to be a tail cone, then it has to be jettisoned at the time of sustainer ignition. Otherwise I will have heat issues that will transfer through the tail cone and into the airframe. Frankly I am not married to this idea, but it is worth testing, like what I did this evening.

MClark said:

If you are really going to have the tailcone burn I would suggest you contact the club where you are planning to launch. You don't want to just show up and have the RSO deny approving the flight.

M

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After tonight's test, I do not think it is an option. Even if I can get it to happen in a ground test, I cannot duplicate the conditions at 25,000' to be able to say with certainty that it can happen. It was fun to watch and the neighbor's dog did bark however.

Sorry if I'm late to the party and in case this has already been suggested previously:

What about using the tapered 29mm closure and an internal thrust ring? If the motor protrudes, it can even be used as a staging coupler (probably needs bigger fins to maintain stability).

Another option: Just glue or friction fit a tail cone to the aft closure, if the thrust ring on the motor is desired. If you're concerned about loosing it, because the glue softens or the fit becomes looser due to thermal expansion, make it out of wood. Even if you accidentally litter the landscape, it will degrade over time.

Whatever you do, keeping the tail cone on the rocket is most likely beneficial for it's performance.

Reinhard

Wingarcher said:

Wouldn't you want the tailcone to still be there post second stage burn? Lower drag coasting then is good too, no?

What does a few degrees of off-vertical do to these altitude estimates? At what altitude/angle combination does horizontal dispersion become a significant issue?

N

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I would be interested in a sim of what the effect of a complete tail cone fairing on the sustainer would have on the altitude achieved during coast.

I don't know of a program that could create it. It should have considerable effect because it essentially becomes a boosted dart until the sustainer fires. The tail cone would eliminate most of the base drag.

Reinhard said:

Sorry if I'm late to the party and in case this has already been suggested previously:

What about using the tapered 29mm closure and an internal thrust ring? If the motor protrudes, it can even be used as a staging coupler (probably needs bigger fins to maintain stability).

Another option: Just glue or friction fit a tail cone to the aft closure, if the thrust ring on the motor is desired. If you're concerned about loosing it, because the glue softens or the fit becomes looser due to thermal expansion, make it out of wood. Even if you accidentally litter the landscape, it will degrade over time.

Whatever you do, keeping the tail cone on the rocket is most likely beneficial for it's performance.

Reinhard

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Hmmm... A balsa tail cone perhaps? With the tapered aft closure the cone could have a wooden dowel in the center the same diameter as the nozzle hole so it could also keep the igniter in place. It could fit inside the tapered closure which would create a small but insignificant lip, but would prevent drag separation. The balsa could be sanded and sealed with white glue (several layers) which would add strength to the surface and also enable a smooth sanded surface. I wouldn't paint it because the balsa and the glue are made of natural ingredients and would biodegrade well.

Woohoo! Mad Cow is having an Independence Day sale. 15% off the entire inventory. Just got the 29mm thin wall airframe and couplers to start working on "Do." Also working with Upscale CNC for other parts. One of the added experiments for this bird will be to test a balsa tail cone. Basically fly a low altitude configuration, ideally twice the same day. One with and one without the tail cone to see the altitude difference.

Challenges I see with the tail cone.
- Stability - Will I need bigger fins?
- Longer interstage coupler - I will need about a 3" longer coupler with a tail cone. How much altitude does that cost, and does the tail cone compensate for it.

Making it out of balsa takes out most of the weight issues.

Can't you just sim put the tailcone on the sustainer and simulate it? The software (RASAero or OR) doesn't know or care if its possible mechanically.

I was thinking of "deploying" the tailcone after engine burnout out. Think 3D shutter plate concept....

Could do it as a single stage, but Neither OR or RASAero will let you stuff the tail cone inside the transition. You can show a rocket with a tail cone to zero" dia. provided the forward end of your transition is also 0" dia. That configuration however will play into the aerodynamic algorithms, so it will not be an accurate representation.

EeebeeE said:

Bob,

Since this is minimum diameter, rear motor retainers will not work including boat tail retainers. The retention needs to be inside the airframe at the forward end. Aeropack makes those as well. Cesaroni makes an aft closure that is the same diameter as the outside of a FG airframe.

So the concept is to have a boat tail in place during the coast phase between stages to reduce drag and achieve a higher altitude before the second stage fires, but when the second stage fires, the tailcone is jettisoned.

So the question becomes, how do we safely jettison a tailcone that we have no intention of recovering? The idea of paper or paper mache is that it would be biodegradeable and would tumble to the ground. The other thought is that since it is jettisoned from 25,000' and is relatively small, perhaps we can build it so that it incinerates when the sustainer is fired so that pieces of it would harmlessly fall to the ground and degrade.

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You do not appreciate how a boosted dart/small diameter second stage with a boat tail functions to eliminate base drag because if you did you would not dump the boat tail. I'll suggest that you read about Gerry Bull and his low drag extended range projectiles, and the ballistics of current line of long range boat tail bullet and maybe you will glean some knowledge from that.

It's not my job to educate you on drag reduction so I'm done. Good luck with your project.

bobkrech said:

You do not appreciate how a boosted dart/small diameter second stage with a boat tail functions to eliminate base drag because if you did you would not dump the boat tail. I'll suggest that you read about Gerry Bull and his low drag extended range projectiles, and the ballistics of current line of long range boat tail bullet and maybe you will glean some knowledge from that.

It's not my job to educate you on drag reduction so I'm done. Good luck with your project.

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Bob, I had initially looked at a boosted dart concept before I started this thread as an option to achieve 100,000.' If the dart was 29mm in diameter (and with a tail cone to reduce base drag) I would have achieved it. However, the sim was too close for comfort.

With N Power a boosted dart becomes a very good option, and there is another thread on TRF that proposed to use N power to put a dart into "space" (100KM). I think that is a great project, and I wish him well. However it is not a project that I can afford becaue the speeds are much greater so the materials have to be much stronger and therefore much more expensive. PLUS, if I am going to spend the money to send a rocket this high, I want photos, and the 29mm diameter dart severely restricted the space I could use for a camera, which ultimately reduces the quality of the camera.

So I opted specifically to achieve 100,000' on M power using a 2-stage minimum diameter rocket. 3" for the booster. 2" for the sustainer. This configuration on M power, outperformed a boosted dart capable of carrying at least one, preferably two, onboard cameras in computer sims.

However, having a boat tail during the interstage coast phase is a cool idea. I could gain more altitude before the sustainer fires because of reduced base drag, and that additional altitude would be compounded by a higher altitude when the sustainer ignites. Plus, the use of a CTI tapered closure which is essentially CTI's version of a 54mm boat tail, but attached to the motor case instead of the airframe (Look up CTI Part # P54-TC) increases altitude even more. So during the interstage coast, base reduction is substantially reduced, and because of the tapered closure, base drag is still somewhat reduced after the sustainer motor burns out.

The difference between what you are talking about and what I am talking about is that you are looking at an aft retainer with a boat tail. I am looking at a forward retainer, but the aft motor closure is tapered, essentially creating the same effect as a boat tail.

You are definitely right in that reduction of base drag will result in increased altitude. I am just skinning the cat a different way. Please continue to add comments. I respect your thoughts.

- Evan

Many of the thoughts posted here echo ideas we have been talking about for some Team Icarus projects and I think a jettisonable aft tailcone would be mighty valuable.

I think the best bet here would be to use a fiberglass cone with a small flame resistant streamer inside. I would look to design an easily shearable mechanical interface to retain it.

On head end ignition: I have seen it done a few times with success and I have done it once at XPRS last year when I flew my AT M1419W to AT M650 two stage to 55k'. https://www.dropbox.com/s/t8fx10hdn8b01r2/FBLP%20XPRS.wmv?dl=0

I am planning to fly the same rocket on an AT N1000W to M685W at XPRS this year. Head end ignition again.

But I have to admit that the way I do it kind of gives me the willies. Not for the faint of heart. For those interested in how I do it you can read about it in the Fall 2015 AEROPAC Newsletter beginning on page 18. I also describe how the device was installed when building the moon burn motor with an offset core.

I do not recommend using my method for obvious reasons. Using the flat wire method running along the motor inside the airframe gives one a safer and more "convenient" way of accomplishing 2nd stage ignition.

Jonathan DuBose

jondub said:

On head end ignition: I have seen it done a few times with success and I have done it once at XPRS last year when I flew my AT M1419W to AT M650 two stage to 55k'. https://www.dropbox.com/s/t8fx10hdn8b01r2/FBLP%20XPRS.wmv?dl=0

I am planning to fly the same rocket on an AT N1000W to M685W at XPRS this year. Head end ignition again.

But I have to admit that the way I do it kind of gives me the willies. Not for the faint of heart. For those interested in how I do it you can read about it in the Fall 2015 AEROPAC Newsletter beginning on page 18. I also describe how the device was installed when building the moon burn motor with an offset core.

I do not recommend using my method for obvious reasons. Using the flat wire method running along the motor inside the airframe gives one a safer and more "convenient" way of accomplishing 2nd stage ignition.

Jonathan DuBose

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I have not done head-end ignition and I don't plan to because it is difficult to do an "all up" test (where everything is turned on but the igniter itself is outside of the motor). I think if forced to do it, I would try and have a way of getting everything armed with an external igniter attached, and then switch over to the real one. I hope you are at least switching out the igniter while you power things up, although I didn't see mention of that in your article.

Jim

This may be a dumb suggestion from an HPR mulitstage noob, but I think the talicone idea is pretty cool. If you don't need much to hold it on, how about small magnets to hold the tailcone in place until the sustainer fires? Something like this would be pretty cool.

BDB said:

This may be a dumb suggestion from an HPR mulitstage noob, but I think the talicone idea is pretty cool. If you don't need much to hold it on, how about small magnets to hold the tailcone in place until the sustainer fires? Something like this would be pretty cool.

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Cool idea. Wonder how much electricity, which is a prized commodity onboard a rocket, would be needed to mechanically twist the magnet to an "off" position. Keep in mind it has to escape the friction of being connected. Great thought, though.

JimJarvis50 said:

I have not done head-end ignition and I don't plan to because it is difficult to do an "all up" test (where everything is turned on but the igniter itself is outside of the motor). I think if forced to do it, I would try and have a way of getting everything armed with an external igniter attached, and then switch over to the real one. I hope you are at least switching out the igniter while you power things up, although I didn't see mention of that in your article.

Jim

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Inclined to agree with you, Jim. Seems better to used tried and true approaches than experimental when it comes to ignition. This would be better done at lower altitudes to prove its effectiveness.

I just think "printed magnets" sounds cool. I'm pretty sure that the ones in the video are solid state magnets, though an electromagnet would be cool because you could presumably turn it off. You are right that an on/off magnet would likely require an additional battery and controller of some sort, and that would probably be an unnecessary complication.

patelldp said:

Shoot me a message with your address and I'll get it in the mail tomorrow. It's a Performance Rocketry clamshell model and the shoulder isn't great, but a little work will make it go a long way. It's the graphite-infused gel coat, as well.

Hey, the price is right!

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Dan, the NC arrived today. It is perfect. In excellent shape and I think the shoulder is fine. Thanks again. I really appreciate it.

And so the first build begins! Wahoo. I am using a Mad Cow Thin-wall 29mm airframe plus couplers. The 29mm conical FG nose cone generously sent by Dan Patell, and G-10 FG fins and bulkheads cut by Upscale CNC. When finished, the 2-stage rocket will be a little less than 4' tall. Even though Rocketpoxy should be able to hold the fins in place to Mach 2.2 ..faster than this will fly... I am going to hone in on my tip-to-tip FG skills. so I had Upscale CNC cut a fin alignment jig/cradle. This way I have proper alignment of the fins, and then can lay the fincan into the cradle and hold everything in place while I layer sand and lead weight on the fins to properly hold the glasscloth onto the fins as the glue sets. This should keep everything in pretty fine alignment.

Here's the obligatory parts photo...



And here is the assembled cradle showing a couple fins held in place.

I hate to be that one guy.... But has anyone considered launching from a high altitude balloon? Can BP ignite that high? And I guess stability would be an issue... But has it been Done?