What Altitude does Big Bertha go out of sight? (or any 24" long BT-60 Tube Rocket)

[CrocketRocket]

At around what altitude does Big Bertha go out of sight? (or any 24" long BT-60 tube rocket)?

I've not yet built or flown any BT-60 rockets before.

 

[neil_w]

If you fly it on 18mm motors then that is something you won't need to worry about.

I flew my Solar Warrior, which is of roughly similar size with a 24mm mount, to something over 1000' (guessing 1300?) on an E15 and it was still visible, allthough pretty small at that point. I would guess something like 1500' is where visuals are going to get iffy, but obviously there's no hard cutoff from visible to invisible.

 

[Banzai88]

As much depends on your eyesight as it does the color of the rocket and the overall sky (clear, bright, partly cloudy), but roughly 1500 feet is where small rockets start to get really small 'up there' for us old guys.

 

[CrocketRocket]

Yeah. I'm 42. . . and my vision is definitely not what it used to be. So I know exactly what you mean. But, 1,500ft that's a good guide.

Second question: 1,500ft altitude on a Big Bertha with reduced 12" parachute or huge streamer for recovery. . . any idea how big a field that would require?

As a kid I would launch on whatever field was available. Most fields were tiny, so I would have to stick to A and B engines. Still, I had so many small parachute rocket models fly away that I became paranoid of parachutes, and either converted to streamer or cut out the center circle of my chutes.

Now I have access to a larger field, but I still wonder.

Thanks.

 

[Back_at_it]

Really depends on your vantage point. If you are directly under the rocket at the pad, it is easy to lose them even at 500-600 ft. If you are away from the pad 200-300ft you can track even a small rocket 1200-1500ft. I've been able to track a brightly painted Alpha with a D in it from a few hundred feet away all the way to apogee. If you are flying the Bertha on an 18mm Estes motor you won't lose sight of it on anything unless you painted it white or light blue.

Of course If you stuff a 24mm mount in it an start using AT motors, well then that's another story

 

[CrocketRocket]

big motors = This is of course VERY tempting.

(I see what you mean about moving away. Looking from the side, I'll see the whole profile of the rocket. Looking directly under, I'm only seeing a 2"circle with thin fins. Makes total sense now)

Thanks

 

[Banzai88]

Yeah. I'm 42. . . and my vision is definitely not what it used to be. So I know exactly what you mean. But, 1,500ft that's a good guide.

Second question: 1,500ft altitude on a Big Bertha with reduced 12" parachute or huge streamer for recovery. . . any idea how big a field that would require?

As a kid I would launch on whatever field was available. Most fields were tiny, so I would have to stick to A and B engines. Still, I had so many small parachute rocket models fly away that I became paranoid of parachutes, and either converted to streamer or cut out the center circle of my chutes.

Now I have access to a larger field, but I still wonder.

Thanks.

Best bet for all of that is to do an Open Rocket sim, as cross winds are going to play a factor in your decision. You can plot all of the 'what if' scenarios, and take a worst case into Google Maps for your field and simply get a good look at things and evaluate from there.

But some quick math:
15fps descent rate with 1500ft altitude achieved = 100 seconds descent time.
5mph average cross wind = 7.3 fps side travel rate.
100 seconds descent time X 7.3 fps side travel rate = 730 feet recovery downwind.

So you can extrapolate from there where the rule of thumb '1/2 altitude = recovery run out' comes from.

Only you can decide if the rocket can withstand 15fps or greater impact with the ground.

 

[CrocketRocket]

Excellent rule of thumb. I'll remember that!

 

[neil_w]

15fps descent rate with 1500ft altitude achieved = 100 seconds descent time.

And that's without thermals.

Amazingly, my Solar Warrior caught some thermals and took at least 3 minutes to come down, and landed about 100' from the pad. That was a gooooood day.

 

[Back_at_it]

And that's without thermals.

Amazingly, my Solar Warrior caught some thermals and took at least 3 minutes to come down, and landed about 100' from the pad. That was a gooooood day.

You got lucky, It's normally a bad day when your rocket catches a thermal and you see your rockets going up under a parachute when they should be coming down. I had Guardian seemingly hang at the same point for 30-45 secs about 400ft up before it caught another gust and took off for the field across the road.

 

[neil_w]

You got lucky, It's normally a bad day when your rocket catches a thermal and you see your rockets going up under a parachute when they should be coming down.

I sure did!

 

[Alan15578]

Yeah. I'm 42. . . and my vision is definitely not what it used to be. So I know exactly what you mean. But, 1,500ft that's a good guide.

Second question: 1,500ft altitude on a Big Bertha with reduced 12" parachute or huge streamer for recovery. . . any idea how big a field that would require?

As a kid I would launch on whatever field was available. Most fields were tiny, so I would have to stick to A and B engines. Still, I had so many small parachute rocket models fly away that I became paranoid of parachutes, and either converted to streamer or cut out the center circle of my chutes.

Now I have access to a larger field, but I still wonder.

Thanks.

One of my favorite rockets was a Big Bertha powered by and FSI E5, It flew to almost 1000 feet, I used an 18 inch chure with a 6 inch spill hole, practically a ribbon chute. visibility never a problem.

In general visibility is highly dependent on sky conitions, but you could look at old altitude records for optically tracked rockets.

 

[cbwho]

You got lucky, It's normally a bad day when your rocket catches a thermal and you see your rockets going up under a parachute when they should be coming down. I had Guardian seemingly hang at the same point for 30-45 secs about 400ft up before it caught another gust and took off for the field across the road.

I had a nose cone separate from the rocket with the camera on the nose cone, and it simply went horizontal over the horizon
There is a hill which I believe caused an updraft...

 

[Back_at_it]

Second question: 1,500ft altitude on a Big Bertha with reduced 12" parachute or huge streamer for recovery. . . any idea how big a field that would require?

First, 1500ft in a Bertha is going to take some doing. You're talking 24mm and at least and E20 or E30 to get there but it is doable.

As for field size. This all depends on the wind. If you get lucky and have a calm day, you can get them to land a few hundred feet from the pad. On a windy day you could be in for a long walk.

I've put my 24mm powered Bertha up on an C11's, D12's and one E20-7 composite. On the E20 we saw 1442ft on the altimeter but it landed in the tall grass about 400ft from the pad. This was a dead calm day with a 12" chute and no spill hole. When we sent it up on the D12 we saw around 700ft but winds were 5-8 mph. Again, 12" chute. That was easily a 1/4 mile walk through tall grass. I would not have wanted to put it up on the E20 that day as it would have landed in the next county.

As for streamers. I only use them on rockets with plastic fins or when I'm landing in tall grass and weeds. A normal park that gets mowed or a baseball/soccer field would be way too hard of a landing. A Foil type streamer that is crinkled and about 4"x48" will bring down a Bertha pretty well but don't let it land on anything hard or you'll be replacing fins.

 

[CrocketRocket]

This sounds like pretty good news. Sounds like I can significantly increase the engine size, yet still launch and not loose sight at any point.

All my previous rockets have been BT-20, and BT-50, so they often disappear from view during the highest portion of their flight. With just a "puff" at ejection, being the clue how high it went. . . then reading the altimeter once we get the rocket back. I think my boys will enjoy seeing the rocket WAY up in the sky for the whole flight.

Thank you for the streamer advice. My field is a wild meadow = tall grass and soft sand. I think the 12" parachute or 4"x48" streamer could both be viable options.

Thanks

 

[Banzai88]

For more of an apogee puff, try some of the bright orange tracking powder. Once you get a technique down to make it work, it's very noticeable and dramatic!

 

[Back_at_it]

Thank you for the streamer advice. My field is a wild meadow = tall grass and soft sand. I think the 12" parachute or 4"x48" streamer could both be viable options.
Thanks

Perfect. That stuff you see in the back is what I'm typically landing on. 9 times out of 10 the rocket doesn't actually touch the ground. It gets hung in the brush. Depending on the time of the year, this stuff can be 4ft tall.