Possibility of using spring to boost Estes rocket on launch

[Gus]

It's my understanding that the Russians Regularly used "a pinch of something" in their pistons, for a while , until it became obvious.

It's my understanding that the Russians Regularly used "a pinch of something" in their pistons, for a while , until it became obvious.

Terry,

Less nefarious than one might suppose. Not just the Russians, almost all of the Europeans flying 10 mm Euro motors use a pinch of black powder.

First, almost all the 10 mm motors are "quasi-composites" using modified black powder propellant. Nozzles are really tiny and very shallow. So contact area for ignition and flammability of exposed propellant are much less than for something like an Estes motor.

Almost all Euro motors are flown off pistons where the igniter is a very short V-shaped piece of wire which is plugged in to the top of the piston head. Unlike Estes igniters these little wires have no accelerant applied to them. The Euro motors just sit down onto the igniter wire, very similar to how micromax motors sit on the little uncoated igniters.

Because of this, most Europeans press a small pinch of loose black powder in the motor nozzle before setting it down on the igniter wire. Honestly, the amount of black powder involved isn't substantially more than the black accelerant that used to be on the old Estes Solar Igniters.

Are there some who might use more black powder than really necessary? I'm sure it happens. And there are those apocryphal stories of motors failing to ignite and the rockets still sailing 20 feet off the piston. So that's why FAI outlawed pistons for the altitude events. Do those fliers still put a pinch of black powder in the motor nozzles before putting them down on the igniters? Almost assuredly. They need to to ignite the motors. Is it possible some still use too much to get a little extra kick, possibly.

But the bottom line is that most of our competitors are completely honest and when we get beat, which happens often, it's simply because there are so many truly world-class competitors out there.

Steve

 

[troj]

I just did a one hour presentation on pistons for the Juniors hoping to make the next U.S. Spacemodeling team.

It covers both fixed and floating head pistons.

You can see the presentation here:

I saw this thread and immediately thought of your presentation!

-Kevin

 

[Spacedog49Krell]

Thanks for your piston report. It might be worth revisiting piston launch systems with the technology available today. I've bench tested a system at 1000Hz and it probably can be faster. The more significant characteristic today would be reduced mass. The Raven 3 was 1 oz and required a BT-60 tube. My bench prototypes fly in BT-20 rockets. I believe the mass can be reduced to ~5 grams.

 

[lr64]

I still think compressed air would be fun, for someone motivated enough. Much of the required tech is already well developed by HAM guys wanting to loft a weighted tennis ball with a string over a tree branch to pull up an antenna, which I gather they do pretty often. Only problem is that they do it with PVC pipe. Or they did the last time I checked. Lofting a string would also be good for shaking the branches of tall trees for retrieval purposes. Dual use. Appropriate safety precautions might be necessary, depending on just how powerful the system was.

Come to think of it, the easy way is probably to use some of that 1010 rail with a light sled with ball bearing rollers. Surgical tubing instead of a spring. Set the rocket on the sled, free to come off the top. Sled to have own chute if necessary. Some clever device to pull the trigger the instant heat or exhaust was detected.

If what I think was the original idea of a compression spring was used, it could be protected by sacrificial fabric, soda can aluminum, etc.

 

[Art Upton]

^We have used Tethered Tennis Ball launchers to get rockets out of the trees at our club in the past. Probably the best rocketry use for them. Get the cord in a position to pull on the shock cord or parachute.

 

[Alex (Boyce Aerospace)]

I can't remember where, but I read a research paper about using very long launch rails with a sled that was propelled by a thin cable around a pully at the top of the rail and a drop weight. The paper fully described the construction and testing of the launcher along with a study of the use of different amounts of weight and at what point to ignite the rocket's motor on the sled (or after leaving the sled) to achieve the highest altitude. I believe in his tests he insured that the rockets would be stable as they left the rail even if no ignition occurred making the use of the device similar to a second stage flight event. I found the project very interesting.

Alex

 

[SolarYellow]

A drop weight can't accelerate at more than 1g. You'd need a pulley system to provide mechanical advantage to multiply that into a level of accel significantly useful to launch a model rocket.

 

[BABAR]

. I believe in his tests he insured that the rockets would be stable as they left the rail even if no ignition occurred making the use of the device similar to a second stage flight event. I found the project very interesting.

Alex

this initially sounds good, but on consideration may be a problem.

In the absence of an electronics initiated EJECTION event (I.e. Jolly Logic Chute Release doesn’t help if no deployment), a standard single deploy rocket that leaves the rail stable without motor ignition is most likely to imitate the St Louis Arch and return ballistic.

This is generally considered poor form. Definitely want to aim at least 5 degrees AWAY from the flight line.

I theeenk there was an article in Peak of Flight where a young rocketeer teamed with a senior rocketeer and created a tower catapult which accelerated the rocket before ignition, but I searched Apogee site and couldn’t find it.

I DO think the idea of a band or a spring PULLING the rocket forward might be more easily implemented than a PUSHER system, and easily implemented with a burn string to insure rocket ignition.

In fact, I believe such a system is used for RC gliders.

 

[Art Upton]

In fact, I believe such a system is used for RC gliders.

The Surgical Tube Glider Launchers are stretched out along the full length of the runway at the R/C club to get them in the air. I have not seen it used at our club since Electric Motor powered gliders became lightweight [ >2 decades ago]

Edit: probably used in some competitions where they don't allow motor power on the glider. But we don't do competitions in my club anymore.

 

[lr64]

Winches and hi starts have been used much more recently than that and are still used in some competitions. If you strapped a rocket to one of the carbon fiber competition models and zoom launched the model with a good winch, you could separate from the model during the zoom, with hundreds of feet of altitude and maybe 100 mph velocity up. Maybe not so very practical, of course. Plus, the pilot would probably be upset if you ignited early and burned the tail off.

I haven't seen the rocket and burn string thing, but I have seen a small RC rocket glider get an extravagantly high launch from what may have been only a D motor.

 

[bad_idea]

I just did a one hour presentation on pistons for the Juniors hoping to make the next U.S. Spacemodeling team.

It covers both fixed and floating head pistons.

You can see the presentation here:

Great presentation, Steve. Thank you for making and posting it.