Rockets that do better on windy days?

[FishnBeer]

I had a free weekend to go launch some rockets with the fam. Had not flown any in a while and needed to get out of the house. Go to our spot and conditions are not ideal. Not bad at ground level, but theres a breeze higher up.

My 1/2A mini rockets hit that breezy layer and ended up on a nearly horizontal trajectory mid burn and shot over 100 yards away and almost gone for good. My lower flying rockets on small motors did not seem to go high enough to hit the jet stream but they drifted a ways under parachute.

My hi flier for whatever reason came down the closest of the bunch. It was the fastest flyer of the bunch and I thought for sure it was going to be in the trees. Maybe it went so fast it punched through the wind rather than going with it? and streamer recover meant no hang time for it to drift off into oblivion.

So it got me thinking, I should have a few 'windy day' rockets. But what makes a rocket good for windy day? # of fins? Body length? Tube/fin diameter? Speed?

 

[K'Tesh]

So it got me thinking, I should have a few 'windy day' rockets. But what makes a rocket good for windy day? # of fins? Body length? Tube/fin diameter? Speed?

Well... There's Dorothy...





https://www.rocketryforum.com/threa...instrumentation-launched-into-tornado.153027/

 

[Bat-mite]

For ground wind, more thrust. For winds aloft, a streamer instead of a chute, or a spill hole in the chute if a streamer is no good. More weight means less air-resistance coming down, so heavier rockets.

 

[BABAR]

Kites

 

[kuririn]

Maybe don't launch on windy days?
And that tornado rocket is a Quest Magnum Sport loader.
Don't know if that's a particularly effective rocket in wind, other than it's a two engine cluster.

 

[dhbarr]

Stubby rocket with 7 short tubefins, fastest motor it can take, streamer.

 

[neil_w]

1) The faster it goes up, the less it will weathercock (use high-thrust motors)
2) The faster it comes down, the less it will drift (streamers, dual-deploy, Chute Release, etc.)
3) Probably, heavier rockets will be less buffeted by the wind.

 

[jadebox]

1) The faster it goes up, the less it will weathercock (use high-thrust motors)
2) The faster it comes down, the less it will drift (streamers, dual-deploy, Chute Release, etc.)
3) Probably, heavier rockets will be less buffeted by the wind.

The first two are true. Number three would help only if it makes the rocket not go as high and/or makes the rocket come down faster (so, it is really a specific version of the first two).

 

[neil_w]

The first two are true. Number three would help only if it makes the rocket not go as high and/or makes the rocket come down faster (so, it is really a specific version of the first two).

Hmm, are you sure? Do you think a 1000 lb rocket would get blown as much in the wind as a 1 oz rocket, at equivalent altitude? I don't. It's probably not a simple relationship, and it could be that density is more relevant than weight (or mass), but I would say the general point stands.

Certainly, points 1 and 2 are likely to be most important.

 

[jadebox]

Do you think a 1000 lb rocket would get blown as much in the wind as a 1 oz rocket, at equivalent altitude? I don't. It's probably not a simple relationship, and it could be that density is more relevant than weight (or mass), but I would say the general point stands.

No, the heavier rocket would not drift as much. But that is only because it would fall faster. So, that's a case of #2 being true.

 

[neil_w]

No, the heavier rocket would not drift as much. But that is only because it would fall faster. So, that's a case of #2 being true.

Galileo would disagree.

Unless you're saying it would fall faster because its mass to drag ratio would be greater, in which case that is the same reason it will drift sideways less due to wind.

(BTW this is not really an argument I'm interested in pursuing)

 

[jadebox]

Galileo would disagree.

Nope. (Edit: Unless he wanted to pick on me for assuming that the heavier rocket would fall faster. As Tony notes below, under parachute, it might not.)

The formula for the distance a rocket will drift (relative to a point on the ground) as it falls is simple. It is the time it falls multiplied by the wind speed.

 

[manixFan]

The rate at which a rocket drifts is dependent on its descent rate - the weight of the rocket is basically immaterial. The larger the rocket, the larger the parachute canopy with more area to catch the wind, which offsets the additional weight. In all the drift calculators I've ever used, all that matters is descent rate and wind speed, the weight of the rocket has never come into it.

You want rockets with high speed and close to nominal stability. No over-stable rockets with big fins. And a streamer, reefed chute or dual deploy.


Tony

 

[BABAR]

Why do I feel like this is the same as asking, “What kind of kite should I fly in a thunderstorm?” ????
Sunny windy days are good for doing something OTHER than flying rockets.

 

[kuririn]

A 10 lb. rocket will fall at the same rate as a 1 lb. rocket.
Remember Galileo's classic experiment from the leaning tower of Pisa?

 

[manixFan]

Hmm, are you sure? Do you think a 1000 lb rocket would get blown as much in the wind as a 1 oz rocket, at equivalent altitude? I don't. It's probably not a simple relationship, and it could be that density is more relevant than weight (or mass), but I would say the general point stands.

Certainly, points 1 and 2 are likely to be most important.

What the heck? A rocket falling at 20 feet per second is going to be affected by the wind the same no matter how much it weighs, 1 lb or 100 lbs. At BALLS we've done calculated expected drift distance many times on all kinds of rockets, from 3 pounders to 75lbs, and the only numbers that matter are wind speed and descent rate. And as long as we have a good wind profile the results are reasonably accurate. Rocket weight is not an issue when calculating drift. The canopy on a parachute to slow a 1000lb rocket to 20 FPS is obviously far larger than one for a 1 oz rocket, and will present a much larger surface area to the wind, providing roughly the same sideways force as what the 1oz rocket feels.

All rockets fall at about the same rate because the chute is sized to bring them down safely: bigger rockets = bigger chutes.

This is definitely not rocket science!


Tony

Edit: added quote about weight and canopy size.

 

[kuririn]

No, the heavier rocket would not drift as much. But that is only because it would fall faster.

Rocket weight is never an issue.

Agreed, rocket weight is not an issue, as proven by Galileo.

 

[manixFan]

Agreed, rocket weight is not an issue, as proven by Galileo.

Sorry, no!! Rocket weight is not an issue because we are talking about drift (horizontal force) caused by the wind and descent rates controlled by parachutes. We're not taking about round spheres dropping unretarded through the air. Galileo was basically concerned with the effects of gravity, not aerodynamics. Rockets drift the same amount regardless of weight because they typically all descend at the same rate because the chute is sized to match the weight of the rocket. If heavier rockets were allowed to fall at a faster rate with a smaller chute they would drift less. If a light rocket fell at a faster rate because of a small chute it would drift less. If two rockets of greatly varying weights fall from the same altitude with the same descent rate, they will drift roughly the same distance. You could argue that the larger, heavier rocket will drift further because it presents a larger cross section to catch the wind.

Some will argue that certain designs drift less. That may be but in all the years we've done drift calculations we've never taken the chute design into consideration and it has not affected our results.


Tony

 

[kuririn]

Sorry, no!! Rocket weight is not an issue because we are talking about drift caused by the wind and descent rates controlled by parachutes. We're not taking about round spheres dropping unretarded through the air. Galileo was basically concerned with the effects of gravity, not aerodynamics. Rockets drift the same amount regardless of weight because they typically all descend at the same rate because the chute is sized to match the weight of the rocket. If heavier rockets were allowed to fall at a faster rate with a smaller chute they would drift less. If a light rocket fell at a faster rate because of a small chute it would drift less. If two rockets of greatly varying weights fall from the same altitude with the same descent rate, they will drift roughly the same distance. You could argue that the larger, heavier rocket will drift further because it presents a larger cross section to catch the wind.

Relax. All I'm saying is that a heavier rocket will not "fall faster" as stated by the other post.
The acceleration will be the same as any other mass. The descent rate may be faster than a lighter rocket depending on the sizing of the chute. It also might be slower. That goes without saying.

 

[manixFan]

Relax. All I'm saying is that a heavier rocket will not "fall faster" as stated by the other post.
The acceleration will be the same as any other mass. The descent rate may be faster than a lighter rocket depending on the sizing of the chute. It also might be slower. That goes without saying.

Your quote about Galileo ignored aerodynamic effects, which is the entire point of this discussion.


Tony

 

[jadebox]

Relax. All I'm saying is that a heavier rocket will not "fall faster" as stated by the other post.
The acceleration will be the same as any other mass. The descent rate may be faster than a lighter rocket depending on the sizing of the chute. It also might be slower. That goes without saying.

The acceleration due to gravity is the same. But, two objects don't necessarily accelerate at the same rate when falling in air.

 

[Cape Byron]

 

[kuririn]

Here is a recreation of Galileo's experiment by physicist Steve Shore.
Two water bottles of differing weights dropped from the tower at Pisa.
Both landing at the same time.
Repeated several times.
Not saying that air resistance isn't a factor, but in this case it is negligible compared to the acceleration of the water bottles. And any difference in acceleration due to air resistance is undetectable to the human eye.

 

[kuririn]

The acceleration due to gravity is the same. But, two objects don't necessarily accelerate at the same rate when falling in air.

Yes, so wouldn't a "heavier" 16 oz. circular disk fall more slowly than a "lighter" 15 oz. bullet?

 

[jadebox]

Yes, so wouldn't a "heavier" 16 oz. circular disk fall more slowly than a "lighter" 15 oz. bullet?

Sorry, I really don't understand what you are trying to say. Earlier, you suggested that the acceleration for any two falling objects is the same, but now you are saying that a larger object will fall slower than a smaller one. Those statements are contradictory.

 

[kuririn]

Sorry, I really don't understand what you are trying to say.

No, the heavier rocket would not drift as much. But that is only because it would fall faster.

I'm saying that a heavier rocket will not necessarily fall faster than a lighter one. As you stated:

But, two objects don't necessarily accelerate at the same rate when falling in air.

The value of the drag coefficient of the heavier rocket compared to the lighter one could result in the lighter rocket coming down faster. i.e. the air resistance could be greater with the heavier rocket.
BTW how are you and Bracha doing? Well, I hope.
Stay safe!

 

[kuririn]

Those statements are contradictory.

And yours aren't?

No, the heavier rocket would not drift as much. But that is only because it would fall faster.

But, two objects don't necessarily accelerate at the same rate when falling in air.

So you're saying that a heavier object will always fall faster than a lighter one through air?
Or would you like to make that contingent on other variables?

 

[jadebox]

And yours aren't?

No. The two statements you quoted are not contradictory.

So you're saying that a heavier object will always fall faster than a lighter one through air?

No, that's not what I said.

 

[kuririn]

No, that's not what I said.

No, the heavier rocket would not drift as much. But that is only because it would fall faster.

Hmmmmmmmm.

 

[jadebox]

Relax. All I'm saying is that a heavier rocket will not "fall faster" as stated by the other post.
The acceleration will be the same as any other mass. The descent rate may be faster than a lighter rocket depending on the sizing of the chute. It also might be slower. That goes without saying.

No one is suggesting that a heavier rocket will always fall faster. When I said earlier that a heavier rocket would fall faster, it was with the assumption that a heavier rocket was chosen to reduce the drift. In that case, it would have to fall faster in order to reduce the drift.

Anyway, I think you are misunderstanding what acceleration means. If the acceleration is the same, the descent rate will be the same. A falling object is subjected to the force of gravity and the force of the air resistance. So, the acceleration is not always the same for any two falling masses in air. In a vacuum it is, but not in air.