Capt. GoodVibes - My First Attempt At Hybrid Build

[fanga]

Howdy All.

Well for us downunder things are quiet for the next 6 months while we eagerly await the end of the bush fire season. With that in mind ad a few other reasons, I am going to start the design and build of a scratch built 54mm Hybrid rocket.

Main goals here are
- Learn to work with liquids (N2O)
- Learn how to use GSE

Sticking with my current trend of naming my rockets after Aussie Cartoon Strips, I have decided to call this rocket Captain GoodVibes.

Once again I will start the design based on some stock materials I already have. I have 2 lengths of black coloured Fibreglass 54mm tube (we can pretend its Carbon Fibre ). So my initial designs will be based on this.

I will be asking all sorts of questions here as I have no idea when it comes to Hybrids and need a lot of help. I will try and learn as much as I can by searching but sometimes I have no idea what I am looking for.

Anyways sit back and enjoy the journey.

 

[fanga]

OK I have Q1 already. I am trying to decide if I will build a rocket that can handle multiple size motors. I will stick with ConTrail for the moment as they are well known, available and I don't mind spending the $$$. I am OK to buy both the 38mm and 54mm complete motor systems so I have a mix of sizes I can use.

The body tube I have is a bit over 1700mm long for the first peice. I have started some basic modeling with the booster 1700mm long and the payload 400mm long.



No it's not a complete model yet. I am just mucking around with the potential options.

I have modeled 6 different motors and they seem to be all within spec for a good flight.



My first question, am I nuts for trying build a Hybrid rocket that could potentially fly all 6 of these motors? Should I consider making this a smaller rocket and simply flying the first few motors to get some experience first with Hybrid specific issues like the shifting CG?

Thanks in advance for your thoughts.

 

[Hobie1dog]

long enough for just about any motor

 

[fanga]

On further research, I may be able to split the booster in two and shorten for the smaller launces. Looks like the forward bulkhead can be attached to a motor retainer. I can't seem to find any details on this to confirm except people saying that it will work. Can anyone show me some pics of the forward bulkhead ataching to an AeroPack min diameter retainer?

I can make this modification later so I will forge on with the design at full length. It wont hurt to do this. On the smaller flights the CG is well in front of the entire motor housing so I am assuning there will not be much issue with CG movement causing instability.

 

[OzHybrid]

Your first one will be difficult enough. Don't make it longer than you have to. It's windy at Mullaley....Usually.... The longer it is, the longer your launch rail will need to be.... As great as it would be to see a ridiculously long rocket, the logistics don't add up. How long a launch rail do you have access to?
Velocity off the rails needs to be higher for a rocket with high "calibers of stability" which in this case is an oxymoron as it won't be going fast enough off the rail. Some of the lower velocity sims might be too low rail exit speed for high calibres of stability and could lead to windcocking.
Max launch windspeed is 32K/h=8.88 m/s
if you say your max windcocking angle is 15deg, Then:- tan(15)=Wind velocity/Min rail velocity
Min Rail Velocity=8.88/tan(15)
Min rail velocity=33m/second ish..........
This is a simplistic view as it's the initial state. As your vertical velocity increases further, the effect of the wind reduces but does add a bit less windcocking in the next second. This is just based on the velocity vector sum. It does not include the additional direction change due to the rotational windcocking.

 

[fanga]

Awesome advice as always Norm, Thanks heaps for this. It confirmed my intial gut feeling re don't make it too complicated.

The unis now normally bring long rails to launchs. I can borrow one of those.

And apologies for the confusion on the rail velocity. That was me in a hurry and those models were set to the default 1m rod. Doh.

 

[BDB]

Following. Because I’d love to venture into hybrids too. For now, I’ll learn vicariously through this thread.

 

[troj]

Predicted 543 ft apogee on the smaller motor - the risk there is how fast/reliably your recovery comes out. Will it fully deploy in time to prevent lithospheric braking?

For me, that's the only real concern I'd have.

-Kevin

 

[BABAR]

Will it fully deploy in time to prevent lithospheric braking?

For me, that's the only real concern I'd have.

-Kevin

I guessed but checked

Lithosphere​

The lithosphere is the solid, outer part of Earth, including the brittle upper portion of the mantle and the crust.

This has also been referred to as

OOI* (pronounced “Oy”) deployment


* Open On Impact.

OOI is often followed by Vey, but I don’t know what Vey stands for.

 

[OzHybrid]

Predicted 543 ft apogee on the smaller motor - the risk there is how fast/reliably your recovery comes out. Will it fully deploy in time to prevent lithospheric braking?

For me, that's the only real concern I'd have.

-Kevin

It's all right Kevin. The ground is really soft at Mullaley.