Need Rocket Boosted Glider Design Info

I realized I should have titled this "Need Rocket Glider Design Info" as it really needs to be a Glider,and not a boosted glider

I have been involved in rocketry for along time, but never really delved much into the realm of rocket gliders. As a teen I built a Estes Space Shuttle, but the shuttle/glider seemed to fly in exactly the same way that cows don't. Well maybe closer to the way that cows do.

Anyway, my son got a project for Science Olympiad where they are supposed to design a water rocket that can carry an egg aloft for a duration event, but they cannot use a parachute, and the vehicle cannot change shape. We were talking about different ideas for bringing the egg back, and I asked him what he thought about bringing it back like a glider. We built a concept vehicle just using a "well it looks like it might fly" approach, and when we tossed it, it seemed like it glided about like my old space shuttle. So we launched it. Well... the up part went really well, but the down part was almost as fast as the up.

We found this thread which is close to what we would like to do Water Powered Lifting Body Rocket, but I don't think he would be allowed to adjust the elevons due to the whole "No change in shape" rule.

So I guess I have 2 questions:

1. Is it possible to design a Rocket Glider that does not raise elevons to convert between rocket mode and glider mode?

2. Can anyone point me to a good resource for designing Rocket Gliders?

Thanks for any help!

Not really giving you an answer, but your "contest" sounds similar to the various "egg drop" contests that are held at engineering colleges.

The idea is to use a combination of helicopter motion and air bag. The rocket fin are angled so that the rocket spins going up, then spins coming down: thus creating drag to slow down.

The egg is not at the top of the rocket, but about 3/4 the way up the rocket tube. Toothpicks in the tube prevent the egg from falling toward the exhaust end of the rocket. There is toilet paper packed in the upper quarter of the rocket tube, so that when the rocket points down, the egg pushes against the toilet paper. You may also want the egg to receive its shock load at the 'pointy end', since the egg can withstand a greater shock at that end.

Here are some ideas:

https://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXFSUF&P=0

https://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXDHTY&P=0

Regarding gliders:
Gosh, a model big enough to hold an egg would be quiet large. Could you stick your water rocket on the nose of a big foam glider?

I am really not aware of a glider design that would work for you. Good luck!

Here are some gliders from Apogee:
https://www.apogeerockets.com/Rocket-Kits/Glider-Rockets?zenid=m8eb8ev0krcieak2lu4bniaob0

The NAR has a section on Rocket Glider designs for contests: https://www.nar.org/contest-flying/competition-guide/duration-events/rocketglider-duration/. The one I was specifically thinking of was the Mediocre Fred design https://www.nar.org/wp-content/uploads/2014/05/Mediocre-Fred-D-RG-Wickart.pdf which has no moving parts, relying on the change in CG as the propellant burns to switch from boost to glide.

I have no idea how you would adapt that to a water rocket, nor about attaching an egg, but that's my suggestion for a starting point.

Best of luck!

Crawf56 said:

The idea is to use a combination of helicopter motion and air bag. The rocket fin are angled so that the rocket spins going up, then spins coming down: thus creating drag to slow down.

The egg is not at the top of the rocket, but about 3/4 the way up the rocket tube. Toothpicks in the tube prevent the egg from falling toward the exhaust end of the rocket. There is toilet paper packed in the upper quarter of the rocket tube, so that when the rocket points down, the egg pushes against the toilet paper. You may also want the egg to receive its shock load at the 'pointy end', since the egg can withstand a greater shock at that end.

Click to expand...

We had considered using helicopter recovery, but with no change in shape,our thought was that anything that would slow it down would offer a lot of drag on the way up as well. Severely limiting altitude and therefore duration.

Crawf56 said:

Regarding gliders:
Gosh, a model big enough to hold an egg would be quiet large. Could you stick your water rocket on the nose of a big foam glider?

I am really not aware of a glider design that would work for you. Good luck!

Click to expand...

Sorry, I did not go into all of the rules of the competition, but one is that nothing can be placed further back than 5 cm in front of the nozzle so that it won't interfere with positioning on the launcher. So all forward engine concepts are out.

Thanks for the well wishes!

Mr Rocket said:

We had considered using helicopter recovery, but with no change in shape,our thought was that anything that would slow it down would offer a lot of drag on the way up as well. Severely limiting altitude and therefore duration.

Click to expand...

I thought the Estes Quinstar did not change shape. Sorry.

This was our early prototype (slightly worse for the wear)



The concept was to design a flying wing with the pressure vessel at the rear, and a second plastic bottle in front of it to act as the protective vessel.

I guess what I am really looking for is any guidelines or Rules of Thumb for sizing the wing?

Also, proper procedures for trimming the glider and making sure we get enough lift?

Kind of a "Rocket Gliders for Dummies" with enough math that we could figure this out.

On my RC gliders I try to keep to about 5-7oz/square foot wing loading, simply divide wing area by weight in the right units. You want something slightly nose heavy for unguided boost and then would need some up trim for glide that could be done with a mechanical timer similar to the lifting body water rocket design I posted earlier from a friend of mine. I'm assuming that the water is behind the CG and that the loaded water bottle will give you the most tail heavy condition. The water bottle thrust is very quick, so a slightly tail heavy design may work ok, you may want to consider putting the egg somewhere in the middle to avoid a really nose heavy design, or it may turn out that in the nose is the right place for the right CG. You can figure out where your masses are and design the wing placement and dimensions put the CG right where it will naturally balance out.

Crawf56 said:

I thought the Estes Quinstar did not change shape. Sorry.

Click to expand...

Using something similar to the Quinstar would certainly meet the requirements of the contest.

No need to be sorry. Definitely something to consider if the glider idea tanks.

Thank you Crawf56! :handshake:

burkefj said:

On my RC gliders I try to keep to about 5-7oz/square foot wing loading, simply divide wing area by weight in the right units. You want something slightly nose heavy for unguided boost and then would need some up trim for glide that could be done with a mechanical timer similar to the lifting body water rocket design I posted earlier from a friend of mine. I'm assuming that the water is behind the CG and that the loaded water bottle will give you the most tail heavy condition. The water bottle thrust is very quick, so a slightly tail heavy design may work ok, you may want to consider putting the egg somewhere in the middle to avoid a really nose heavy design, or it may turn out that in the nose is the right place for the right CG. You can figure out where your masses are and design the wing placement and dimensions put the CG right where it will naturally balance out.

Click to expand...

Based on the 5-7oz/SF, I think the wing was way undersized.

Thanks for the rule of thumb. That is exactly the kind of data I have been trying to find, but unable to locate. :handshake:

You are going to need a big shift in CG.
No moving parts.........does the water count as a moving part? Is there a way to have extra water ballast up front that gets released at Apogee to shift CG back? Thinking maybe the ejection charge of the engine could melt a plug releasing the water?

Why not have the water "fuel" ahead of the CG?