Idea for controlling descent time with propeller

[Nolan Chu]

Hi Rocketry Forum,

In April I will be competing in TARC, and for those that don't know, this year the goal of the competition is to launch three eggs as close to 856 ft as possible and then recover the eggs with a total flight time of 43-46 seconds. You can find the full rules here.

Although I could just do a bunch of test flights and simulations to determine the parachute size that would get closest to the 43-46 second goal, I had an idea to use a single motor and propeller in addition to the parachute in order to have more control over the time. The motor and propeller wouldn't be strong enough to allow the rocket body to hover, but while the propeller is going, it can "reduce" the weight of the rocket and consequently slow the descent. In my really preliminary calculations I found that I can expect a pretty decent range (~10 seconds of variability) of times by either having the motor on or off. Ideally I would be able to program the on board flight computer to autonomously adjust the motor speed to dial in the time.

I also thought of using something a bit more stable like a drone, but I've found even the smallest ones are still too big to comfortably fit in a rocket that has a weight limit of 650 grams. Also I was hoping I wouldn't need the stability either because it would still use a parachute.

I was wondering if either this has been done to some extent by other previously or if this idea is totally stupid and way out of my grasp and experience (as a rocket novice but decent programmer).

Any feedback would be appreciated.

 

[Steve Shannon]

I think that’s a very interesting idea. I’d like to see you try it. You might have to try a few different arrangements to find where to place the propeller in relation to the chute. You wouldn’t want it to collapse the chute by diverting air, but what a cool concept. You might want to look at ducted fans as used by some RC planes too.

 

[jlabrasca]

It brings to mind the Ronco Inside-the-shell-egg-scrambler.

...
I also thought of using something a bit more stable like a drone, but I've found even the smallest ones are still too big to comfortably fit in a rocket that has a weight limit of 650 grams. Also I was hoping I wouldn't need the stability either because it would still use a parachute.

I was wondering if either this has been done to some extent by other previously or if this idea is totally stupid and way out of my grasp and experience (as a rocket novice but decent programmer).

Any feedback would be appreciated.

I have not read anything about or seen any rockets with powered rotor recovery, but there have been (and will be) autogyro can sat competitions.

https://www.cansatcompetition.com/docs/CanSat_Mission_Guide_2019.pdf

I was wondering if either this has been done to some extent by other previously or if this idea is totally stupid and way out of my grasp and experience (as a rocket novice but decent programmer).

Any feedback would be appreciated.

Yes, the idea is totally stupid and way out of your grasp and you should absolutely pursue it. If for no other reason than the clever naming opportunities. The "Nuvolone", the "Usuyaki Tamago"...

 

[Exactimator]

If I were interviewing two job applicants, one who made it to TARC finals with a standard rocket with chute recovery and another who thought up, designed and implemented a functioning motorized prop recovery that DIDN'T make it to TARC finals, I'd hire the prop recovery guy.

Even more so if he made it to finals and especially if he won, but both of those would be less important than the ability to think outside the box, design and execute something innovative.

But if you just want to make it to finals and win, stick with the standard chute recovery and practice a lot.

 

[anbhtblr]

If I were interviewing two job applicants, one who made it to TARC finals with a standard rocket with chute recovery and another who thought up, designed and implemented a functioning motorized prop recovery that DIDN'T make it to TARC finals, I'd hire the prop recovery guy.

Even more so if he made it to finals and especially if he won, but both of those would be less important than the ability to think outside the box, design and execute something innovative.

But if you just want to make it to finals and win, stick with the standard chute recovery and practice a lot.

+1

 

[Culprit]

Hi Nolan,

You have a great idea that should be pursued, but I recommend emailing TARC to ask for a clarification on the rules to see if your idea is allowed. Here’s an excerpt from this year’s rules:

“The portion of the rocket containing the egg payload and the altimeter (the “Apollo Capsule”) must separate from the rest of the rocket in the air and must descend separately under at least two parachutes that are the same shape and are within 50 millimeters (2.0 inches) of the same diameter. The rest of the rocket must recover safely under any deployed recovery system.“

If your idea is allowed, you would need two or more parachutes, plus your propeller.

 

[DAllen]

Hi Nolan,

You have a great idea that should be pursued, but I recommend emailing TARC to ask for a clarification on the rules to see if your idea is allowed. .

Great recommendation. While the prop system may not technically break the rules it may violate the intent of the rules so clarifications are a fantastic idea.

If the prop thing is not allowed how about a reefing system where the computer you program can control holding the shroud lines on the chute together and then releases them or visa versa to control descent time.

I sure hope the prop system works. Would love to see that in action.

-Dave