Precision Launch Pads?
 

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see a similar thread having been posted previously, which leads me to suspect if such a thread exists, that it has been archived.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!

Were it not for the atmosphere, it would be a fun project. What I mean by that is that winds aloft and wind shear wreak havoc with flight profiles, and therefore have a lot of "say" on where a rocket lands. It might be a fun science fair project in NASA's VAB, since you do not have the wind influence (when the doors are closed) that you have at a more typical launch.

More often than not, when I have left the launch rod toward dead-center, it's a better flight. For me, things sometimes have gone awry when I begin tilting the rod.

Greg

Many times, the wind at ground level and just above the tree line are a bit different. Causing a rocket to either veer off course (most notably the sci-fi Viper) or the chute to carry it several blocks more than planned...

Thanks for the comments. I realize that the wind at higher altitudes is going to be different than that at the launch site. It also occurs to me that wind is three dimensional: it won't exert a purely orthogonal force to the flight of the rocket.

However, I was thinking that I could project where I thought the rocket would land, and then use a GPS to mark the actual landing site. The difference between the two would be a combination of two factors: environmental effects, and then imperfections in the build of the rocket itself. I was playfully thinking of the latter quantity as "rocket fudge."

Over consecutive launches on the same day, environmental effects might be consistent enough to include as rough estimates. I'm not expecting to predict the exact spot in which the rocket will land, although I do think it would be cool to have a contest to accurately predict the landing site. If I could bring the rockets down within 50 yards of the launch site, then I think that would be a success.

I'll update this thread with my progress. It could still be a fool's errand, but at the moment it's very intriguing for me! :cool:

Please post the results. My guess is that the lower the impulse, the tighter the CEP will be.

Greg

I think that this is more art than science. You develop a feel for where your rockets will land based on your knowledge of the specific field, your experience launching rockets in it under various conditions, and your experience launching your specific rockets with various motors. It all gets combined and processed in your brain to produce something akin to an intuitive feel for the process. I wish it could be reduced to a set of equations, I really do. No expert system or artificial intelligence ever invented has ever had anything like the information processing power of the human brain, nor has any technology ever had anything approaching the incredibly tight coordination of eye, hand and mind. The quadrillions of computations that are executed between our ears every second take place at a level just below consciousness, and they produce results that we perceive as intuition and experience-derived knowledge. I suspect that the most successful predictions of the landing spots for our unguided model rockets will be achieved through the use of these stupendously powerful tools.

In other pursuits, this is sometimes known as a "home field advantage."


Bill

Except that it can be acquired anywhere. One just has to spend a little bit of time at a location and launch some rockets there. None of us ever go to totally new and unfamiliar launch fields all that often. We all do almost all of our launching at a restricted number of sites. Over time the peerless technology that we were all born with gathers the high quality data and performs the ultra-sophisticated multivariate analyses that enable us to fly our rockets in them with ever-improving skill.

Home field advantage stops working when a representative of the national club comes over and changes the angle on your rod with the result your rocket ends up in a tree :eek:

Doug

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Lercari Engineering
 

Remember Lercari Engineering in 1972? I still have their catalog. They sold several motorized launchers and even an automatic countdown ignition system complete with a nixie tube display! Their motorized launchers tilted your rocket in azimuth and elevation. Had microprocessors been abundant in 1972 they probably would have tried just what you described!

Tedster

I don't see much use in it, but it still sounds like a fun project.

kj

Bad officiating can trump the home field advantage almost every time. Was this at McGregor? That big tree got it when the tornado went through.


Bill

Though the capability may bother some, I have always been fascinated by the possibility of combining a steerable parachute, a GPS receiver and a microcontroller.

Such a system is not likely to be good enough to guarantee a win in spot landing, but it will lessen wind drift and can be programmed to try to avoid hazards such as roads, clumps of trees or bodies of water.


Bill

How about a Gemini Titan with an RC Rogallo wing capsule recovery system? Naturally you'd need to have the scale recovery skids for full fidelity points. If things got ugly during glide recovery you could eject the scale astronauts out of the capsule using some Quest 'freeps' in the ejection seats.

I guess NASA planted enough of their boilerplate capsules in the desert during development that they stuck with parachutes and a water recovery. That doesn't mean we have to!!

Wow, that must have been an amazing launcher for the time. I've never heard of them, but that sure sounds impressive!

I was about to say that your suggestion didn't really fit with my idea of a "precision launch pad," but then I saw Bill's post above. Your idea is a bit outside of my budget!

I have to admit that I briefly considered adding RC servos to an Estes SR-71 rocket and eschewing parachute recovery altogether. That's a completely different project. ;)

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:

Doug

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I remember Lercari. Back in the day, I saw their ad in one of the rocket magazines so I ordered a catalog from them. It took a LOOONNGG time for it to arrive, so long that when it arrived I was surprised because I thought it was hopelessly lost. To their credit, there was an included note apologizing for the late delivery. I also remember that the graphics were not all that great in the catalog.

The really cool thing is not on the launching end, it's on the recovery end. I want recovery systems to home in on where I am. I'm sure it's possible, but it would be pricey.

Greg

This could be the seed of a fascinating NAR Research & Development contest category entry. You could use the same "wind-weighting" equations that are used to aim the launchers of full-scale unguided sounding rockets so that the rockets will land in desired impact areas. As the folks at Wallops Island, White Sands, Woomera, and other ranges do, you could collect pre-launch wind data from a ground-based portable anemometer and acquire "winds aloft" data by tracking the motions of released helium balloons. (The "big boys" sometimes botch their "wind-weighting"--the second British Skylark sounding rocket veered far away from its assigned impact zone on the Woomera Range in Australia because the launch crew accidentally skipped one of the equations that they used to compute the rockets' trajectories based on the winds aloft!)

On the micro scale that we deal with, the winds change way too much for this data to remain relevant.


Bill

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

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.

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.

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 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

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.

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.

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?