Large Hybrid Model Rocket

[Raider5678]

Hello guys.

I have an engineering project I've been working on for quite some time now. It's a large hybrid rocket that I plan to build, and I expect it to cost around 2-3k.

Now, because it costs so much, I plan to build it over the course of a few years. But at the same time, I really don't want to waste money so I'd like some tips.

 

So, I'll explain it now. 

 

Firstly, it's objective.

The objective is to get it to around 1k meters, and then bring it in for a propulsive landing. I know landing it will be extremely hard, but that's more of an afterthought.

For comparison, my highest rocket got to about 1800 feet, but that was for a church group who asked me to make them one. I built two, but one of the parachutes failed.

Either way, that's the objective. (It's always good to have an objective for a project in mind right? Beats randomly putting it together.)

1k meters with a propulsive landing. 

 

So, now I'll cover the engineering part of it.

 

For the engine, obviously, I'll be using a hybrid rocket engine.

The fuel will be solid rubber-based fuel fed by gaseous oxygen OR a solid paraffin wax fuel fed by gaseous oxygen. 

The oxygen cannister will be controlled by a motorized valve that can not only open and shut quickly but can be opened specific amounts. Allowing me to control the throttle of it through an onboard flight computer.

 

The flight computer will have a simple motherboard, a gyroscope, an altimeter, a battery pack, an inertial measurement unit, a small camera, and an accelerometer. This is mainly going to collect data because I don't believe the first few flights will be a success, so I'd like to have as much data as possible to see where it went wrong(I.E. wasn't slowing down as expected because it wasn't pointing the right direction). It will use a reaction wheel located near the top of the rocket to control its rotation.  But I'm not sure on the physics of that one so please tell me if that's wrong I'll accommodate changing it to a different section, like the middle. 

The nose cone will contain a small parachute that the flight computer will activate should data reach certain parameters(I.E. not pointing the proper direction, not slowing down like expected, or going too fast at a predetermined height.)

 

Other than that, basic specifications are currently 3 1/2 inches in diameter and 4 ft tall without the nose cone and the rocket is expected to weight around 40-60 pounds. 

 

 

I plan to test the engine first after making it so that I can learn exactly how much thrust I'm getting, how long it can burn, how well it restarts, etc.

Necessary things for the flight computer. 

As for the flight computer, I plan to have it fairly small, so I'll send it up on a reliable rocket that I have that can lift around 3 pounds of extra weight so that I can test the computers readings and everything else. 

 

Once the engine and the computer have been I will start work on integrating them into the main rocket together.

After that is done, I'll do a static test of the rocket to make sure the flight computer is capable of controlling the rocket, the reaction wheel, and interpreting expected data and actual data.

 

 

So, before I commence with assembling the engine and flight computer, is there anything major that I missed?

[Frank]

Wow!  That sounds like fun.

Two thoughts were (and I have no experience with this) how do you keep the rubber or wax from continuing to burn and how do you re-ignite the rocket?  Or is that the answer, it just keeps burning but at a slower rate.  If I understood correctly what "propulsive landing" means  spacex or blue origin type of tail landing.  Some kind of inverse pendulum algorithm and directional thrust.  Or the reaction wheel is to hold it upright, like a spinning top.

Interesting.

 

[Silvestru]

Raider, do you have any photos of your previous two rockets? I just want to have an idea and I understand you want to have a different design for this one.

25 minutes ago, Raider5678 said:

I built two, but one of the parachutes failed.

Also I am a bit worried about this.

Haha what if some innocent family receive an unexpected rocket visitor in their rooftop. 

[Raider5678]

8 minutes ago, Silvestru said:

Raider, do you have any photos of your previous two rockets? I just want to have an idea and I understand you want to have a different design for this one.

Also I am a bit worried about this.

Haha what if some innocent family receive an unexpected rocket visitor in their rooftop. 

I have a large clear flat area to launch the rocket. It should be well away from danger even if it passes that because then there's only 1 lousy barn and house, before clear all over again. Regardless, proper precautions will be taken. 

 

I do have a video of the previous rocket, however, I don't want to share it because it's technically the group's rocket and their video, which is linked to their group directly. Although, the previous was a relatively simple two-stage rocket that landed with a parachute. It is a modified version of the randomizer rocket built by grant Thompson, which is the first rocket I built. The second one had a larger parachute container, so it deployed easier, and a larger nose cone.

 

20 minutes ago, Frank said:

Wow!  That sounds like fun.

Two thoughts were (and I have no experience with this) how do you keep the rubber or wax from continuing to burn and how do you re-ignite the rocket?  Or is that the answer, it just keeps burning but at a slower rate.  If I understood correctly what "propulsive landing" means  spacex or blue origin type of tail landing.  Some kind of inverse pendulum algorithm and directional thrust.  Or the reaction wheel is to hold it upright, like a spinning top.

Interesting.

 

The rubber will keep burning, that's how I restart the engine. However, when simply burning on atmosphere without the oxidizer, it'll basically just become smoldering hot rubber, and when the oxidizer is reintroduced it'll burn again.

The paraffin wax would be around twice as powerful as the rubber, however, I'm concerned that when the oxidizer stops the wax will still be melting, resulting in a lot of loss of potential fuel, and possibly even resulting in the nozzle becoming clogged, resulting in an explosion when the pressurized oxygen burns with the wax. Not a major explosion, but enough to possibly damage the rocket. Hence why I'm leaning towards using a rubber.

I'm using oxygen because then I don't have to worry about the gas catching on fire and burning back through the tube and into the container. THAT, would result in one hell of a firework and probably be getting me investigated by firefighters for a safety hazard. 

[Frank]

I imagine you've already considered, but apparently ABS can be 3d-printed into an optimal shape for hybrid engines' fuel:

http://www.stratasys.com/resources/case-studies/aerospace/rocket-crafters

 

Is there such a thing as reaction wheel kit or do you have to roll your own?

 

 

[Raider5678]

1 minute ago, Frank said:

I imagine you've already considered, but apparently ABS can be 3d-printed into an optimal shape for hybrid engines' fuel:

http://www.stratasys.com/resources/case-studies/aerospace/rocket-crafters

 

Is there such a thing as reaction wheel kit or do you have to roll your own?

 

 

I did. Sadly, I lack access to a 3d printer capable of that.

[Frank]

I build a fairly cheap 3d-printer from an aliexpress kit.  Not as easy as the shiny brochures, but works.  My neighbour and I are talking about building a rocket and he's even considering smelting metal.  3d printed waste casting would help with that too.  Big plans, not enough time.

I don't know if you missed the question or it's top secret , but does  a reaction wheel come as a unit?

 

[Raider5678]

1 minute ago, Frank said:

I build a fairly cheap 3d-printer from an aliexpress kit.  Not as easy as the shiny brochures, but works.  My neighbour and I are talking about building a rocket and he's even considering smelting metal.  3d printed waste casting would help with that too.  Big plans, not enough time.

I don't know if you missed the question or it's top secret , but does  a reaction wheel come as a unit?

 

The reaction wheel will most likely be bought, if I can't buy one, I'll have to find some other method to control the rocket.

[Monomethylhydrazine]

http://www.ukrocketman.com/rocketry/hybridscience.shtml

 

I know I am a little late to the party, but check this website out. I am a liquid bi propellant rocket guy so I am by no means someone who knows hybrid rocketry.  But I skimmed this and it looks good. I think it could really help you. 

 

http://www.arocketry.net/solid.html

 

That website could help you with the safety part. Rocketry is dangerous and I do not want you to hurt yourself. Or anyone for that matter. I am putting this out there, I am not liable for anyone getting hurt using the information I provide.

 

I wish you good luck and be safe!

[Raider5678]

Hey, the rocket engine is coming along nicely. I'm having some trouble getting the right parts to control the oxygen flow remotely, but it's coming along slowly.

No explosions yet, fingers crossed.

It's not an explosive mix, just fuel and oxidizer in a confined space......

[Frank]

I'm curious what you used as an oxygen tank.  I read some discussions (can't remember where) about the pros and cons of NOx (because they are available in small and light cartridges) and other things such as paintball cartridges.  Also wondered if some sort of pressure regulator is used or just a tiny orifice?   So you're looking for a servo controlled valve or maybe a pulsed solenoid, something like a throttle body injector?  What did you choose to vary the flow rate?

 

[Raider5678]

14 hours ago, Frank said:

I'm curious what you used as an oxygen tank.  I read some discussions (can't remember where) about the pros and cons of NOx (because they are available in small and light cartridges) and other things such as paintball cartridges.  Also wondered if some sort of pressure regulator is used or just a tiny orifice?   So you're looking for a servo controlled valve or maybe a pulsed solenoid, something like a throttle body injector?  What did you choose to vary the flow rate?

 

I'm using a small 11 ounce welding oxygen tank, with a small valve feeding into the engine. As I said, yes I'm having trouble finding one that's automatic AND controllable and the right fit.

[Frank]

Maybe try paintball solenoids, should be high pressure, lightweight and cheap. Found type info, but no spec sheet.

http://zdspb.com/tech/misc/solenoids_models.html

 

here a spec sheet

http://www.macvalves.com/wp-content/uploads/PDFs/Series_Pages/Sm3ways/33catalog.pdf

Need a pressure regulator (100 psi max).

[Raider5678]

Update:

The welding oxygen tank didn't work(too bulky, and the seal didn't work and that lead to........problems.)

So, I'm getting a metal worker to make the oxygen tank to the exact specifications.

[Frank]

6 hours ago, Raider5678 said:

Update:

The welding oxygen tank didn't work(too bulky, and the seal didn't work and that lead to........problems.)

So, I'm getting a metal worker to make the oxygen tank to the exact specifications.

Did you look at SCUBA diving tanks?  e.g. http://www.carbondive.com/

 

 

[Raider5678]

1 hour ago, Frank said:

Did you look at SCUBA diving tanks?  e.g. http://www.carbondive.com/

 

I didn't, however I imagine they're larger.

[Frank]

Just now, Raider5678 said:

I didn't, however I imagine they're larger.

And paintball was too small?

[Raider5678]

Just now, Frank said:

And paintball was too small?

I didn't know paintball used oxygen.

[Frank]

Just now, Raider5678 said:

I didn't know paintball used oxygen.

CO2, but it might work as a general pressure vessel compared to rolling your own?

[Raider5678]

7 minutes ago, Frank said:

CO2, but it might work as a general pressure vessel compared to rolling your own?

Maybe.