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-   -   Precision Launch Pads? (http://www.oldrocketforum.com/showthread.php?t=8457)

Bill 01-27-2011 05:10 PM

Quote:
Originally Posted by Doug Sams
Yes, it was McGregor, but not the big tree. Instead, it was downrange, in the trees along the creek on the right. There was concern that rockets were going uprange, over the spectating/prep area. So the solution was to overcompensate :rolleyes:



That must be the NSL I missed, with all of the debate over the then new safety guideline about crosswind positioning.

There was quite a bit of overflying the crowd at NARAM last summer, both from the sport and contest ranges, and many of the same officials were there.


Bill

blackshire 01-27-2011 11:30 PM

Quote:
Originally Posted by Bill
On the micro scale that we deal with, the winds change way too much for this data to remain relevant.


Bill
I can't agree with that, because I've seen it done in support of manned balloon flights. The owner of a local hot-air balloon rides company uses precisely that method (tracking the movements of small toy helium balloons) to determine whether to fly his passenger-carrying balloon (I flew with him in 2008). He takes off up to 30 minutes after tracking his small "pilot balloons," and he flies at a maximum altitude of about 2,000 feet AGL (Above Ground Level, as opposed to Sea Level), which is the altitude zone in which model rockets fly.

nukemmcssret 02-17-2011 06:32 PM

Quote:
Originally Posted by Beowulf
After our flight on Saturday , I am very interested in building a launch pad that allows for more accurate targeting than our basic Estes one. I have an old german equatorial mount, to which I am thinking about attaching a platform. The idea is that I could adjust the tripod to level the pad, and then set the launch angle and direction using the mount.

What I'd really like to be able to do is to enter the current environmental conditions into an application and then use the calculated rod deflection and direction in order to return the rocket close to the launch pad. Heck, if I could make it land back on the rod, then I would!

My question is this: has this type of project been done before? I don't see a similar thread having been posted previously, which leads me to suspect if such a thread exists, that it has been archived. Either that, or the idea itself is folly. What do you all think? Thanks for your feedback!

Go to Scientific Surplus website and get a cheap ten dollar camera tri-pod. Then using the plastic rod holder from your estes launch pad, trace the bottom of it to a piece of 3/16" balsa wood. Cut out this pattern. Drilla hole slightly larger than the 1/4" 20 bolt that comes out of the top of the tripod. Where you mount your camera. Once the hole is drilled using 20 min. epoxy glue a nut the will thread onto the tripod. Usually 1/4" 20 onto the balsa you cut. Let dry. When dry test it on the tri-pod see if you can thread the wood onto the tri-pod. If you can now is the time to epoxy the balsa to the plastic rod holder. make sure the nut is inside. When this is dryyou can screw it onto the tri-pod and now you have a launcher that will aim any where. Also you do not have to bend over to hook up the ignitor.The rocket is about chest level. Another goody is that is you are on uneven ground you can use the tri-pod legs to level it out. I will attach pictures tomorrow. Chief nukemmcssret ;)

hcmbanjo 02-26-2011 08:33 PM

Quote:
Originally Posted by nukemmcssret
Go to Scientific Surplus website and get a cheap ten dollar camera tri-pod. Then using the plastic rod holder from your estes launch pad, trace the bottom of it to a piece of 3/16" balsa wood. Cut out this pattern. Drilla hole slightly larger than the 1/4" 20 bolt that comes out of the top of the tripod. Where you mount your camera. Once the hole is drilled using 20 min. epoxy glue a nut the will thread onto the tripod. Usually 1/4" 20 onto the balsa you cut. Let dry. When dry test it on the tri-pod see if you can thread the wood onto the tri-pod. If you can now is the time to epoxy the balsa to the plastic rod holder. make sure the nut is inside. When this is dryyou can screw it onto the tri-pod and now you have a launcher that will aim any where. Also you do not have to bend over to hook up the ignitor.The rocket is about chest level. Another goody is that is you are on uneven ground you can use the tri-pod legs to level it out. I will attach pictures tomorrow. Chief nukemmcssret ;)


I've got a new Odd'l Rockets accessory coming out in the next few weeks that will allow you to use most any camera tripod for launching without any drilling or epoxy.
When you are done launching, it comes off clean and allows you to use the tripod with your camera.
I've been launch testing this for the past few weeks.
It's great not being on the wet ground trying to connect up micro clips. My bad knee likes it too.
It feels more "professional" flying rockets on a tripod launcher without lightning bolt legs. The Estes plastic rod holder won't last long. My adapter doesn't use it. The blast deflector is locked in and flat.
Launch angles are easier to adjust with the tripod. And, taking launch pictures is easier when the blast deflector is three feet above the ground.
I wish I'd done this years ago!
Keep an eye out for the product announcement.

Peter Olivola 02-26-2011 08:52 PM

This is really not relevant to small rockets under parachute recovery. Think about the force vectors involved. A sub one pound rocket descending at 18 ft./sec vs a full size hot air balloon with a "crew" of probably 1000 lbs. And the upper limit on wind velocity is lower for launching a balloon.

Quote:
Originally Posted by blackshire
I can't agree with that, because I've seen it done in support of manned balloon flights. The owner of a local hot-air balloon rides company uses precisely that method (tracking the movements of small toy helium balloons) to determine whether to fly his passenger-carrying balloon (I flew with him in 2008). He takes off up to 30 minutes after tracking his small "pilot balloons," and he flies at a maximum altitude of about 2,000 feet AGL (Above Ground Level, as opposed to Sea Level), which is the altitude zone in which model rockets fly.

Bill 02-26-2011 11:22 PM

Quote:
Originally Posted by nukemmcssret
Go to Scientific Surplus website and get a cheap ten dollar camera tri-pod. Then using the plastic rod holder from your estes launch pad, trace the bottom of it to a piece of 3/16" balsa wood. Cut out this pattern. Drilla hole slightly larger than the 1/4" 20 bolt that comes out of the top of the tripod. Where you mount your camera.



I believe that 1/4"x20 thread is the size which goes into a 1/4" drill chuck, though you will have to replace the one which comes with the tripod with your longer bolt. I got some of those chucks very cheaply last year when Michaels was clearing out their Fiskers hand cranked craft drills.


Bill

blackshire 02-27-2011 02:02 AM

Quote:
Originally Posted by Peter Olivola
This is really not relevant to small rockets under parachute recovery. Think about the force vectors involved. A sub one pound rocket descending at 18 ft./sec vs a full size hot air balloon with a "crew" of probably 1000 lbs. And the upper limit on wind velocity is lower for launching a balloon.
I respectfully suggest that you re-read Reply #22 more carefully. I wasn't referring to the passenger-carrying hot-air balloon that the local balloon tour pilot flies; I was referring to the small helium-filled toy party balloons that he releases and tracks as pibals (pilot balloons, a term which has *no* relation to a large balloon with a human pilot onboard) to determine if the wind velocities and directions at various altitudes are favorable for his desired flight direction.

Since he seldom flies above 2,000 feet AGL (Above Ground Level), which is also the altitude region in which most model rockets fly, and since the wind force vectors acting upon the small pibals are comparable to those acting upon a model rocket descending under a parachute, the experiment would be a useful one.

Peter Olivola 02-27-2011 09:01 AM

No, it wouldn't. Between the launch of a small balloon and the launch of the rocket, wind vectors will have changed multiple times. Small Balloon wind determination produces snapshots of a dynamic environment. Spring and fall, especially, experience multiple wind shear phenomenon at quite low altitudes. Those seasons also produce the largest directional and velocity shifts in the shortest periods of time. Any effort to use a balloon to predict winds over a fixed location is an exercise in chaos theory. The change rates for altitude, velocity and direction over a single location will yield little more than a general idea. Fine for hot air ballooning (they are considerably less perturbed.) Not very useful in the context of model rocket flight/descent profile prediction.

IIRC there is someone doing multiple flight profile tracking from a single launch location on a single day using GPS. All the plots I saw showed scattering in excess of 90 degrees and in some cases approaching 180 degrees in both boost/coast and decent.

Just as model rockect engine thrust performance varies widely even within the same batch, so, too, do model rocket flight profiles for reasons having nothing to do with winds aloft (vectored thrust, rod whip, etc.)

About the only useful site prediction tool I've ever seen is a bubble generator for determining when the site is below a thermal. Which introduces another variable that makes using small balloons useful for hot air balloons and useless for rockets. As a thought experiment, use a prediction program to build and test a rocket with absolute minimum stability leaving the launch rod/tower (an Apogee D3 flight comes to mind.) Now lower the velocity at that point in the flight by 10% (the effect of launching into a strong thermal.) Assuming zero wind, how will the rocket react? The answer is, unpredictably (rod whip, vectored thrust, etc., and unknowable.)

Like altitude prediction calculations, there are enough unquantifiable variables in trying to do such predictions that they should be considered advisory at best. The popularity of spot landing competition is a function of its randomness, much like Thanksgiving turkey shoots.

Quote:
Originally Posted by blackshire
I respectfully suggest that you re-read Reply #22 more carefully. I wasn't referring to the passenger-carrying hot-air balloon that the local balloon tour pilot flies; I was referring to the small helium-filled toy party balloons that he releases and tracks as pibals (pilot balloons, a term which has *no* relation to a large balloon with a human pilot onboard) to determine if the wind velocities and directions at various altitudes are favorable for his desired flight direction.

Since he seldom flies above 2,000 feet AGL (Above Ground Level), which is also the altitude region in which most model rockets fly, and since the wind force vectors acting upon the small pibals are comparable to those acting upon a model rocket descending under a parachute, the experiment would be a useful one.

blackshire 02-27-2011 09:21 AM

Quote:
Originally Posted by Peter Olivola
No, it wouldn't. Between the launch of a small balloon and the launch of the rocket, wind vectors will have changed multiple times. Small Balloon wind determination produces snapshots of a dynamic environment. Spring and fall, especially, experience multiple wind shear phenomenon at quite low altitudes. Those seasons also produce the largest directional and velocity shifts in the shortest periods of time. Any effort to use a balloon to predict winds over a fixed location is an exercise in chaos theory. The change rates for altitude, velocity and direction over a single location will yield little more than a general idea. Fine for hot air ballooning (they are considerably less perturbed.) Not very useful in the context of model rocket flight/descent profile prediction.

IIRC there is someone doing multiple flight profile tracking from a single launch location on a single day using GPS. All the plots I saw showed scattering in excess of 90 degrees and in some cases approaching 180 degrees in both boost/coast and decent.

Just as model rockect engine thrust performance varies widely even within the same batch, so, too, do model rocket flight profiles for reasons having nothing to do with winds aloft (vectored thrust, rod whip, etc.)

About the only useful site prediction tool I've ever seen is a bubble generator for determining when the site is below a thermal. Which introduces another variable that makes using small balloons useful for hot air balloons and useless for rockets. As a thought experiment, use a prediction program to build and test a rocket with absolute minimum stability leaving the launch rod/tower (an Apogee D3 flight comes to mind.) Now lower the velocity at that point in the flight by 10% (the effect of launching into a strong thermal.) Assuming zero wind, how will the rocket react? The answer is, unpredictably (rod whip, vectored thrust, etc., and unknowable.)

Like altitude prediction calculations, there are enough unquantifiable variables in trying to do such predictions that they should be considered advisory at best. The popularity of spot landing competition is a function of its randomness, much like Thanksgiving turkey shoots.
He takes off as much as 30 minutes after the pibal observations and goes where they went, so the wind flow fields cannot have changed drastically.

Peter Olivola 02-27-2011 09:35 AM

He has altitude control over his hot air balloon and responds to changes as he experiences them.

I watched a hot air balloon descend over my neighborhood last summer. He was shooting for a ball field half a block from the house. It took over half an hour, ascending and descending, before he could make the landing and even then got in the wrong corner of the field (landed in a patch of goatsheads. Very nasty stuff.)

In general terms, it's possible to know approximately where the wind will take you in a hot air balloon. One of the skills in flying a hot air balloon, much like sailing, is being able to "read" changing conditions and using altitude adjustment to pick the right layer. How would that apply to model rockets?

Quote:
Originally Posted by blackshire
He takes off as much as 30 minutes after the pibal observations and goes where they went, so the wind flow fields cannot have changed drastically.


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