Water mass ejection

I saw a post below where someone used water as nose cone mass, which was ejected at apogee. This is quite clever. On the surface it seems fairly easy to make happen. If the nose cone is half full, leave holes. It could act like a flying cup and when cup tips over water falls out. I am not thinking maximum performance here. Is there more too it?
Andrew

When the motor burns out the water would slosh forward, deceleration is greater than one G due to air drag.
It needs some kind of valve.

M

The pessimist in me wonders if the cone is half empty :wink:

One thing that I could think of that might prevent that idea from working is the effects of centrifugal forces. If the nosecone starts to spin, forces might hold the water up inside the cone preventing it from coming out.

Another issue is the effects of the G forces involved. As the rocket slows down after motor burn out, like mclark said, what's to prevent the water from slamming up against the top of the nosecone, possibly dislodging it, or allowing it to leak inside the rocket? Mind you, I'm thinking about the potential for damaging cardboard rockets or any electronics (Oh Hell/Swell).

George's X-1 is the project I think of when you talk water ballast. There should be a link under https://georgesrockets.com/grp/GLIDERS/Glider.htm but it appears to be busted. Hopefully he'll weigh in on this. You can find the old version of the page here https://georgesrockets.com/grp/AOL/GCGassaway/X1.htm

WillMarchant said:

Hopefully he'll weigh in on this.

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:rofl:

I think a plug pulled out on ejection would be pretty easy to come up with.

...or have it in a bladder in the nosecone (water balloon) which is burst on apogee by similar mechanism to firing a cable cutter....


Later!

--Coop

Whatever you use, I'd strongly recommend a "full" container for the water - any sloshing about can quickly lead to oscillations and ultimately instability.

Interesting. I had assumed dumping the water after apogee but I like the observations about the deceleration phase. The key here is that this takes place after motor burnout. Or more specifically after the weight of the propellant has been lost from the tail. So, how long do I need to maintain aerodynamic stability? Every rocket will loose stability at some point prior to apogee strictly due to it decelerating below that threshold. Immediately after burnout could be bad for the load bearing components if it tumbles, however it's not going to change direction. This would have to be compared with the all burnt weight of a rocket design but it seems possible. Perhaps several small holes to leak water out gradually during the unpowered ascent with it all gone by apogee. And add food colouring to help you see the flight.

Hal8472 said:

. Perhaps several small holes to leak water out gradually during the unpowered ascent with it all gone by apogee. And add food colouring to help you see the flight.

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Just don't make it yellow food coloring, or you may lose a lot of friends and the ability to fly at that range very quickly

Yes, yellow rain would be unpopular.

Reminds me of Zappa: "Watch out where the Huskies go, and don't you eat that yellow snow."

I used to fly a paraglider with a water ballast (until I achieved my own ballast). It was fun to fly over the landing zone and dump ballast on spectators.

A small amount of water does not have to fall very far to be disbursed to the point that no one below really cares.

I have a few yellow rain stories as well.