An R/C water rocket plane!

[dongfang]

Hi,

(All pictures are in reverse order!)

I just want to share a rocket plane that I have been working on for some time. It's really a new recovery mode for water rockets: Guided glide to landing. Kind of like the space shuttle, just with water, a lower altitude, and maybe better reliability .

I calculated a delta wing that can carry a water rocket (similar to my SOAR rocket - 4 * 0,5 liter) to landing. The rest was a matter of cutting it out of 6 mm Depron, adding some carbon fiber stiffeners, finding a way to make to rocket stay on board, and adding control surfaces (elevons), servos, receiver and battery.

The delta is 40 cm long and 60 cm wide. There is an almost-double-delta extension at the front wing roots, making the plane a little longer.

The thing seems to be actually able to fly. Next, I will try it out with real R/C (not just a free flight prototype), and if all OK, with a booster under it (2 or 3 stage).

A remaining problem: Will this thing launch stably with a booster? The wings will be way ahead of the center of gravity. Of course I could add even larger surfaces to the booster. Then, the plane will become a kind of canard (and the control directions will reverse).

Regards
Soren

[Brian]

that plane looks good. for the booster you could put it on the side like the space shuttle.

[dongfang]

Hi,

Yeah but without a very sophisticated guidance system & vectored rockets to make up for the imbalances, the booster/plane combination would flip over backwards and crash immediately at launch. I think I have to balance it as good as I can, and make it long and thin (inertial momentum - it will take more force for longer time to make it spin fast around its pitch axis).

I was thinking about a gyro though. I might try to add one (elevator controls) some time.

Regards
Soren

[Spaceman Spiff]

Hi dongfang. I have seen a few people discussing a water rocket glider in the past and I think someone buillt one that crashed. Your rocket seems to be the most advanced water rocket glider ever! I think I have an idea how to make it fly stable.

If you make your wings angled less than 90 degrees from the body they will form a "V" shape when looking at the nose of the rocket. If you make a large drop off booster and mount the plane at the bottom then you have a booster with 2 fins created by the "V" shape of the plane wings. The only thing left is to make a "fake" plane and fix it permanently to the opposite face of the booster. The fake plane has the same exact shape and when you put it on the other side the fake plane wings balance the plane wings and make a perfect fin set.

If the booster has a large thrust it will keep the plane in place during flight until the booster burns out and then the plane will fly off under power. You can put a parachute release on the booster that is operated when the booster leaves. This is quite reliable and should work well for your plane.

Good luck with testing!

[Cloud Dancers]

Hi dongfang,

I lie Spaceman's idea of the long booster with the plane mounted at the bottom using it as a fin set.. I think you would also need a small nozzle so that you had a long thrust. A large nozzle would not work too well as the sudden acceleration might rip the wings off the plane.

[Andromeda]

Here is someone else who tried this recovery:

http://www.charlesriverrc.org/media/199 ... ocket.html

[dongfang]

Hi,

Well I made a few test flights today. First with the prototype on a booster. Pretty much a failure: The 2 stages kind of jackknifed during launch, separated OK and then tumbled to the ground. The R/C plane made a sharp pitch-down at a vertical launch (directly from the pad w/o booster) - the nose goes down towards the wing - and slammed into the ground. No real damage. Tried to correct for that, by trimming the elevons to pitch up some more. Now, the plane just made a 90 deg turn to fly horizontally, then pitches up again and loops ;)

OK the trick is: The center of gravity must be on the thrust vector. When I taped a small wrench to the top of the bottle/fuselage opposite the wing, the rocket rose vertically; very nice flight!! I even had control of it for a couple of seconds, before it went into some kind of spin. The vertical stabilizer was broken after the landing - maybe it happened before the landing, and that is why I lost control? Anyway I will make a larger replacement for it, hehe.

After I taped the wrench to the prototype, it also had a great and straight flight up with the booster - but then also went unstable, and tumbled down. It's s pleasant surprise that the ascent was stable, because the booster/sustainer combination has its center of gravity behind its aerodynamic center.

I will add a larger battery to fix the problem with weight distribution, and ask the experts at rcgroups what to do with the flight stability problem.. and then try to fly it again..

Regards
Soren

[Mark Chen]

Hi,

After I taped the wrench to the prototype, it also had a great and straight flight up with the booster - but then also went unstable, and tumbled down. It's s pleasant surprise that the ascent was stable, because the booster/sustainer combination has its center of gravity behind its aerodynamic center.

I'm shocked to learn the rocket flew in a stable fashion when you had to CG behind the CP! How do you account for this? Do you suppose that the trim you made to the wing is inducing an aerodynamic stability?

[dongfang]

Mark:

I'm shocked to learn the rocket flew in a stable fashion when you had to CG behind the CP!

Me too! I'll try to mark the exact CG (of the booster and sustainer combo) next time I have it tanked, and then tape a rod on it (side to side) through the CG. Then I can maybe hold it by the rod, and run back and forth a few times and see if the nose swings forward or backward..

Maybe the explanation is that there wasn't really any force wanting to spin the rocket anywhere. OK it didn't fly absolutely straight, but more than straight enough.

I have found the perfect weight to replace the wrench: A FlyCamOne^2. It should be coming today! That's going to be so cool ... seeing the booster burn out & drop off, 2nd stage ignition...

Cloud Dancers: OK I think you understood his idea better than I did! Yes a long booster with a lot of energy and the plane at its base might work ... there's still the problem of the CG being off the thrust vector (OK we just launch 2 airplanes then, hehe..).
Hmm that would be a perfect test vehicle for something else I have on the shelf: A pipe from the bottle throat to a nozzle somewhere else. I could make a slight S-bend on it.

Andromeda: Yes I have seen that (keep forgetting the name all the time). I'm surprised he could get it to work at all, seeing how far his whole plane is off the thrust vector. But he did wreck a plane to 2, as I recall...

Regards
Soren

[Andromeda]

Mark:

I'm shocked to learn the rocket flew in a stable fashion when you had to CG behind the CP!

Me too! I'll try to mark the exact CG (of the booster and sustainer combo) next time I have it tanked, and then tape a rod on it (side to side) through the CG. Then I can maybe hold it by the rod, and run back and forth a few times and see if the nose swings forward or backward..

Maybe the explanation is that there wasn't really any force wanting to spin the rocket anywhere. OK it didn't fly absolutely straight, but more than straight enough.

I have found the perfect weight to replace the wrench: A FlyCamOne^2. It should be coming today! That's going to be so cool ... seeing the booster burn out & drop off, 2nd stage ignition...

Cloud Dancers: OK I think you understood his idea better than I did! Yes a long booster with a lot of energy and the plane at its base might work ... there's still the problem of the CG being off the thrust vector (OK we just launch 2 airplanes then, hehe..).
Hmm that would be a perfect test vehicle for something else I have on the shelf: A pipe from the bottle throat to a nozzle somewhere else. I could make a slight S-bend on it.

Andromeda: Yes I have seen that (keep forgetting the name all the time). I'm surprised he could get it to work at all, seeing how far his whole plane is off the thrust vector. But he did wreck a plane to 2, as I recall...

Regards
Soren

I am always amazed to see the German V-1 flying bomb fly in old movies because the thrust vector is so far off, but for some reason it still worked and worked well. This reminds me of that. I'd be tempted to make a model of that bomb from a water rocket just to see it work. You could even perhaps use a booster to get it flying like their catapult and then a smaller nozzel engine to replace the pulse-jet.

[dongfang]

Hi,

With the camera on board (instead of the wrench), it is perfectly balanced. It just goes straight up....

I had a great flight today, at 6 bar. Very smooth and easy to fly. It only was too short a flight...

... so I tried 8 bar....... BAMM. There's too much power in the rocket for that wing. It started flapping like a pigeon on steroids. No control. Vertical crash. The left servo had lost its connecting rod to the control surface, and the other had its gears smashed.

OK I will get the videos on YouTube or somewhere, and let u know.

I can recommend the FlyCamOne. It made these pictures. Only thing I'm not happy about is that the video and audio went out of sync - even though I used a SanDisk "professional" SD card.

Regards
Soren

[Spaceman Spiff]

Congratulations on a great achievement! You're the first one to get this recovery to work! I can't wait to see the video!

I think if you increase the pressure but reduce the nozzle size you will get a longer thrust duration and possibly a higher flight. I suggest you also look at using a foam instead of plain water because this will thrust a lot longer but will not thrust as violently!

[WRA2]

Congratulations on the successful flight.

What great photos.

Videos can be posted here as long as they are not larger then 20MB.

Also congratulations on being the 2,500th post to the forum!!!!

[dongfang]

Hi,

The failed flight was actually more fun than the good one... it looked really funny. It was also the first time I experienced losing control of an aircraft. The damage only cost a couple of cheap servos so never mind .. and I'll get some with metal gears next time.

Maybe I will make another design, inspired by the F-104 Starfighter...

I think Kansky had one succesful flight with his plane, too. BUT it jettisoned the water rocket, so that doesn't count as recovery.

Here's the vid of the succesful flight:

[Bonami]

Amazing video. It really flies! Nicely done transition from vertical to horizontal flying and then a perfect landing! Bravo!